Internship report

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Department: SciTec
M.Sc. Scientific Instrumentation
Internship Report
Simulation and Characterisation of
Permanent Magnets
(01.02.2016-08.06.2016)
Supervised by:
Prof. Dr. Jörg Töpfer
Report submitted by:
Neel Pankajkumar Sheth, M.Nr: 639453
Contact: ns_neel@yahoo.com
+4917680861569

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Acknowledgment
I have taken efforts in this project however, it would not have been possible without
the kind support and help of many individuals and organizations. I would like to extend my
sincere thanks to all of them.
My deepest gratitude to the almighty GOD and My Parents for holding my hand and
guiding me throughout my life. Also thankful to those who support me equally in all aspects.
I would like to express my gratitude to Prof. Dr. Jörg Töpfer , who allowed me to
carry out my Internship and for providing me with all the support for the Internship and
preparing this valuable report.
I am are highly indebted to Dip. Ing. Reimann for his guidance and constant
supervision as well as for providing necessary information regarding the project & also for
his support in completing the project. Further he continuously motivated me to give good
and satisfactory result by interacting with me regularly and giving me tips for
improvements.
My thanks and appreciation also goes to the people who have willingly helped me out
with their best abilities and best possible ways.
Regards ,
Neel Sheth

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Abstract
The report involves study related to a circulator consisting of magnets, LTCC layers and
ferrite layers used for electronic communications in satellites and also with inks used for
screen-printing. The simulations and material prepared would help in optimizing the
current circulator geometry. Simulations are implemented to obtain an idea and a better
understanding of the magnetic field distribution over the surface of the magnet. Using
different variables and geometric parameters enables the selection of optimized
geometry. The realistic measurements of magnetic properties of the magnetic samples
prepared with different composition helps in having a better understanding of the
magnetic behavior. Shrinkage behavior of the ferrite tapes are observed and based on it
new tapes are prepared by milling the powder. Magnetic pastes are developed with
different compositions, which are analyzed, and the best composition is used for screen-
printing. The tapes prepared and films obtained by screen-printing are tested for their
properties to collect useful data for future purpose. Based on all the results and findings a
final circulator geometry is proposed whose practical feasibility needs to tested

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INDEX
Acknowledgment.................................................................................................................................2
Abstract...................................................................................................................................................3
List Of Figures .......................................................................................................................................6
List Of Tables.........................................................................................................................................7
1. Introduction......................................................................................................................................7
2. COMSOL: .............................................................................................................................................8
2.1 Basic structure of the COMSOL simulation:....................................................................................8
2.2 Simulations................................................................................................................................................9
2.2.1 NdFeB magnet with variable height of the magnet and variable air gap..................................9
2.2.2 NdFeB magnet with variable height of the magnet & variable air gap, with & without
iron backing................................................................................................................................................................ 10
2.2.3 SmCo magnets separated by a distance............................................................................................... 11
2.2.4 NdFeB Multipole with different pole distance and heights, with and without iron
backing ......................................................................................................................................................................... 12
2.2.5 NdFeB plates separated by 1 mm........................................................................................................... 13
2.3 Conclusion:...............................................................................................................................................14
3 Perma Graph....................................................................................................................................14
3.1 Measurement of Ferrite samples.....................................................................................................14
3.1.1 Surrounding coil readings......................................................................................................................... 14
3.1.2 Pole coil readings.......................................................................................................................................... 15
3.1.3 New Pole coil: ................................................................................................................................................. 16
3.2 Measurement of NdFeB samples......................................................................................................16
3.2.1 Process for making NdFeb samples....................................................................................................... 16
3.2.2 Readings............................................................................................................................................................ 17
4 AFT ferrite Tapes ...........................................................................................................................18
4.1 Sintering experiments:........................................................................................................................18
4.1.1 AFT RF10 015 with Bi2O3 900°C for 2 h .............................................................................................. 18
4.1.2 AFT RF10 015 without Bi2O3 1300°C for 2 h..................................................................................... 21
4.2 Preparation of New Tapes..................................................................................................................21
4.2.1 Basic principle of the Mastersizer.......................................................................................................... 22
4.2.2 Measurement process................................................................................................................................. 22
4.2.3 Milling process and Particle size measurement:.............................................................................. 22
4.2.4 Further steps: ................................................................................................................................................. 23
4.2.5 Conclusion: ...................................................................................................................................................... 25
4.3 Simplifying the plotting of shrinkage curve ................................................................................25
5. NdFeB pastes...................................................................................................................................26
5.1 Process ......................................................................................................................................................27
5.2 Measurement of Magnetic Properties............................................................................................27
5.2.1 Readings............................................................................................................................................................ 27
5.3 Problems...................................................................................................................................................27
5.3.1 Viscosity............................................................................................................................................................ 27
5.3.2 Terpineol content.......................................................................................................................................... 28
5.4 Screen printing.......................................................................................................................................29
5.5 VSM measurements ..............................................................................................................................30
6. AFT circulator with SmCo...........................................................................................................30
7. Circulator.........................................................................................................................................32
7.1 Trial method: NdFeB (Variable Width & Height)......................................................................33

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7.2 Symmetric Circulator Geometry ......................................................................................................34
8. Final Conclusion ............................................................................................................................35
9.Appendix:Graphs............................................................................................................................36

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List Of Figures
1. Magnetic flux density of NdFeB magnet with variable height and air gap 9
2. Magnetic flux density of NdFeB magnet with and without iron backing 10
3. Magnetic flux density over the surface of NdFeb Magnet with and
without iron backing 10
4. Magnetic flux density SmCo magnets separated by a distance 11
5. Magnetic flux density SmCo magnets separated by a distance at different
working temperatures 11
6. Magnetic flux density of a Multipole NdFeB magnet (pd: 1 mm) with variable air gap
& With and without iron backing 12
7. Magnetic flux density of a Multipole NdFeB magnet (pd: 2 mm) with variable air gap
& with and without iron backing 13
8. Magnetic flux density NdFeB plates with variable height ,separated by a
distance of 1mm 13
9. Magnetic flux density over the surface of NdFeB plates with variable height,
separated by a distance 14
10. Pressure sintering: Before and after images of AFT 10 015 with Bi2O3 18
11.Pressure sintering with less pressure: Before and after images of
AFT 10 015 with Bi2O3 19
12. Shrinkage curve dl/lo (%)for AFT 10 015 with Bi203 20
13. Shrinkage curve dl/dt (%/K) for AFT 10 015 with Bi203 20
14. Pressure sintering: Before and after images of AFT 10 015 without Bi2O3 21
15. Shrinkage demo curve 26
16. Thermal analysis of NdFeB paste containing Magnetic powder,
Terpineol and Araldite 29
17. Magnetic moment vs magnetic field for a NdFeB single layer tape 30
18 Magnetic moment vs magnetic field for a NdFeB three layer tape 31
19. Magnetic moment vs magnetic field for a NdFeB screen printed tape on
Al2O3 substrate 31
20. Magnetic flux density over the surface of AFT circulator with SmCo 32
21. Basic Circulator Geometry 32
22. Magnetic flux density at the center of NdFeB tapes (0.3 cm wide)
23. Magnetic flux density at the center of NdFeB tapes (0.2 cm wide)
24. Magnetic flux density over the surface of Symmetric circulator Geometry 34
25. Magnetic flux density over the surface of Symmetric circulator Geometry with 2-LTCC
and 4-LTCC layers 35

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List Of Tables
1. Perma graph readings for ferrite samples from TriDelta using surrounding coil 15
2. Perma graph readings for ferrite samples from IBS using surrounding coil 15
3. Perma graph readings for ferrite samples from TriDelta using old pole coil 15
4. Perma graph readings for ferrite samples from IBS using old pole coil 15
5. Perma graph readings for ferrite samples from TriDelta using new pole coil 16
6. Perma graph readings for ferrite samples from IBS using new pole coil 16
7. Perma graph readings for NdFeB samples for different powder grade 17
8. Milling Data for AFT RF 10 015_2 at 400 rpm with 3 mm grinding balls 22
9 Milling Data for AFT RF 10 015_2 at 170 rpm with 3 mm grinding balls 23
10. Milling Data for AFT RF 10 015_2 at 400 rpm with 1 mm grinding balls 23
11. Milling Data for AFT RF 10 015_2 with 3 % Bi2O3 at 400 rpm with
3 mm grinding balls 23
12. Perma graph data for samples made from AFT RF 10 015_2 24
13. BET specific surface are measurement 25
14. Standard composition for preparation of NdFeB paste 26
15. Realistic composition for preparation of NdFeB paste 26
16. Perma graph readings for NdFeB samples prepared from NdFeB paste
for different powder grade 27
17. Different composition for NdFeB paste with MQP_B powder for viscosity 28
18. Sample data for VSM measurements 30
19. Magnetic Flux density at 1.2 T & 0.4 T for NdFeB Magnet with variable height
and width used in circulator 33

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1. Introduction
The main tasks of the internship were as follows
o Simulation of magnetic fields of permanent magnets in COMSOL and measuring properties
physically in the laboratory
o Initial preparation, Testing and Optimization of magnetic film for microwave-ferrite component
(circulator)
o Developing the Best Design and Composition of magnetic materials to develop inks for screen-
printing.
2. COMSOL:
This involved carrying out simulation of magnetic fields for permanent magnets with
different geometries in the COMSOL software. To get acquainted with the software the
following steps were followed:
o Previous simulations of SmCo magnets were used as a reference
o Videos and Blogs were referred on the internet
o Tutorials given by COMSOL itself for Permanent Magnets were solved
2.1 Basic structure of the COMSOL simulation:
o Start the COMSOL Multiphysics software
o Select Model wizard
o Select space dimension: 3-D/2-D-Axisymmetric/2-D
(1-D-Axisymmetric/-1D/0-D were not relevant for the task)
o Select Physics: AC/DC
Select physics interface: Magnetic fields, No currents (mfnc) because the behavior of the
magnetic field around the magnets is only to be studied
o Select study: Stationary
This opens up the model builder where the required geometry for the simulation can be
constructed step by step:
1. Definitions: Define parameters in definitions (e.g. Width of the magnet, remanence of the
magnet etc.) any value, which is to be used to construct the model or to carry out the
simulation
2. Geometry: The required geometry is constructed by using the parameters defined in
definitions to standardize the simulation.
Basic geometry for all our simulation: Magnet/s surrounded by an air sphere with a certain
thickness.
3. Materials: Here the material of the magnet is defined and air as a material for sphere.
4. Physics: Here the magnetic flux conversation for the magnet is defined by using the
remanence value defined as a parameter and the direction of magnetization is selected
(normally all the magnets are magnetized axially i.e. the z-direction)
Also, the outer ages of the sphere are defined as zero magnetic scalar potential as the magnet
geometry is confined within the sphere.

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5.Mesh: The result of the simulation depends a lot on the meshing type and size. So the Mesh
type and size were selected very carefully.
General approach for meshing: Keep the mesh very fine for the magnet and normal mesh for
the sphere.
6. Study: This helps to define different cases for the simulation like by using parametric
sweep option; the simulations with different height of the magnets, different working
temperatures, variable air gaps etc. can be carried out
Once everything seems ok, the results can be obtained by using the compute button.
7. Result: After following the entire above procedure the results for the defined geometry are
obtained and are displayed using various options.
2.2 Simulations
2.2.1 NdFeB magnet with variable height of the magnet and variable air gap.
Here air gap meant measuring the magnetic flux density (B) or magnetic field (H) at a certain
distance from the surface of the magnet .The results of the simulation where imported to the
ORIGIN software to plot the graphs showing the behavior of the magnetic flux density at
different distances from the surface of the magnet.
Figure 1 clearly proves the theoretical base of magnetics that the magnetic flux density
decreases by moving away from the magnet surface and the magnetic flux density also
decreases with decrease in the height of the magnet.
Thus it can be concluded that height of the magnet is directly proportional to the magnetic
flux density, while air gap is inversely proportional to the magnetic flux density, i.e. smaller
the air gap higher the magnetic flux induction.
Figure 1: Magnetic flux density of NdFeB magnet with variable height and air gap

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2.2.2 NdFeB magnet with variable height of the magnet & variable air gap, with & without iron
backing.
This simulation was very similar to 2.2.1 but with an addition of iron backing. The
simulation was carried out for two cases: with and without iron backing. The thickness of
the iron backing in this case was 2.5 mm
Figure 2: Magnetic flux density of NdFeB magnet with and without iron backing
Figure 3: Magnetic flux density over the surface of NdFeb Magnet with and without iron backing

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From the figure 2 & 3 it is very clear that the results with iron backing are high in values
compared to the ones without iron backing.
Figure 2 shows that the magnetic flux induction is homogenous over the magnet surface for
the case with iron backing and air gap of 100 µm. Also, the task aim was to make a magnetic
element for a microwave-ferrite component, which has a homogenous field over the surface
of the magnet so that it can magnetize the ferrite layer in between the LTCC layer
homogenously.
2.2.3 SmCo magnets separated by a distance
In this case the study of the magnetic flux induction was carried out at the half distance of
separation i.e. in the center plane at an equal distance from both the magnets; the scenario
where at the center plane would be a ferrite material in real case.
Figure 4: Magnetic flux density SmCo magnets separated by a distance
Figure 5: Magnetic flux density SmCo magnets separated by a distance at different working
temperatures

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The height of the magnets was varied; simultaneously with the distance between the
magnets. The results are shown in the figure 4 & 5 above. The working temperature of the
SmCo magnets is high, but the remenance changes at high temperatures so the simulation
was carried out for room temperatures and for 473 K and as expected the induction values
are higher at the room temperature. The comparison is shown in figure 5. It is very clear
from figure 5 that with different working temperatures but with small height (1 mm) of the
magnet there is no change in the magnetic flux induction but the magnets with significant
height (20 mm) do show a variation in magnetic flux density at different working
temperature but this difference almost vanishes when the distance between the magnets is
significant (in this case 20 mm).
2.2.4 NdFeB Multipole with different pole distance and heights, with and without iron backing
Moving towards complex geometry a multipole magnet with 50 poles in total with different
pole distances and with and without iron backing was simulated. The simulation was similar
to 2.2.2 where the height of the magnet was varied along with the air gap.
Figure 6: Magnetic flux density of a Multipole NdFeB magnet (pd: 1 mm) with variable air
gap & with and without iron backing
From figure 6 & 7 it is clear that for multipole magnet with 1 mm pole distance the iron
backing does not have significant effect on the magnetic flux induction. While multipole
magnets with 2 mm pole distance, iron backing does make a difference but only when the
height of the magnet is large in this case (1000 µm)
The problem with the multipole magnet is that the magnetic flux induction is just at the
edges of the poles and not homogenous over the surface, which does not fulfill the aim of
having a homogenous magnetic field for the microwave-ferrite material

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Figure 7: Magnetic flux density of a Multipole NdFeB magnet (pd: 2 mm) with variable air
gap & with and without iron backing
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2.2.5 NdFeB plates separated by 1 mm
This case was similar to 2.2.3 with the only difference, that the distance between the
magnetic plates was fixed as 1 mm.The aim was also to make magnetic tapes, which are
typically 300 µm thick (NdFeB polymer magnet which typically have remenance of 0.4 T).
The results for the simulations for NdFeB magnets with 1.2 T and 0.4 T are as follows:
Figure 8: Magnetic flux density NdFeB plates with variable height ,separated by a distance of
1 mm

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Figure 9: Magnetic flux density over the surface of NdFeB plates with variable height,
separated by a distance
2.3 Conclusion:
After analyzing the results of different cases it was concluded that the NdFeB plates be used
instead of NdFeb multipole magnet as the aim is to have a homogenous field over the surface
of the magnet in order to homogenously magnetize the ferrite layer.
3 Perma Graph
Specifications of the machine:
Company name: MAGNET-MESSTECHNIK Jürgen Ballanyi e.k.
Magnet examiner: MP2-C (for measuring hysteresis loop)
Electromagnet: EM2
Flux meter: B3
Surrounding coil: J26_COMP.coi
Pole coil: POL6FC01.coi
3.1 Measurement of Ferrite samples
The aim here was to first get acquainted with the perma graph used for plotting hysteresis
loop and also determining the properties of the magnets using the surrounding coil and the
pole coil. The task later was to measure the properties of the magnets prepared by using
NdFeB powder of different grades mixed with PVA.
3.1.1 Surrounding coil readings To start with the hysteresis loop for ferrite samples from
TriDelta which were magnetized at different current was plotted and also for the samples
from IBS. Using the surrounding coil the results are as follows:

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Table 1:Perma graph readings for ferrite samples from Delta using surrounding coil
Surrounding coil (dia: 26mm)
Ferrite
sample from
TriDelta
Magnetizing current Dimension (w*d*h mm) Br (T) Hcj (kA/M) Hcb (kA/m)
40 A 15*10*5 0.342 311.25 254.83
60 A 17*11*10 0.356 311.16 267.27
70 A 30*11*9
large dimension for surrounding
coil
Table 2:Perma graph readings for ferrite samples from IBS using surrounding coil
Ferrite sample
from IBS
Sample Dimension (dia*h mm) Br (T) Hcj (kA/M) Hcb (kA/m)
old 10*5 0.395 233.61 231.32
new 10*5 0.394 230.78 225.65
3.1.1.1 Conclusion for surrounding coil:
Comparing the values from table 1 & 2 with the values from the company data sheet they
seem close enough and acceptable.
3.1.2 Pole coil readings
The next step was to measure the same samples in the pole coil. The results are as follows:
Table 3: Perma graph readings for ferrite samples from Delta using old pole coil
Pole coil old
Ferrite
sample from
TriDelta
40 A 15*10*5 0.245 246.56 186.77
60 A 17*11*10 0.222 268.55 173.25
70 A 30*11*9 0.115 269.99 90.22
Table 4: Perma graph readings for ferrite samples from IBS using old pole coil
Pole coil old
Ferrite sample
from IBS
old 10*5 0.535 208.29 201.25
new 10*5 0.493 224.74 220.64
3.1.2.1 Conclusion
It is clearly observed that the values for the surrounding coil and the pole coil differ a lot.
The readings recorded with the pole coil are just not acceptable because they are too low in
case of samples from TriDelta, while they are too high in the case of samples from IBS. So it
was concluded that the pole might be defective and thus it was decided to use another pole
coil.

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3.1.3 New Pole coil:
With the new pole coil the results are as follows:
Table 5: Perma graph readings for ferrite samples from Delta using new pole coil
Pole coil new
Ferrite
sample
from Delta
40 A 15*10*5 0.256 273.5 197.81
60 A 17*11*10 0.22 281.03 172.9
70 A 30*11*9 0.114 281.35 172.9
Table 6: Perma graph readings for ferrite samples from IBS using new pole coil
Pole coil new
Ferrite sample
from IBS
old 10*5 0.529 190.88 186.58
new 10*5 0.457 204.91 195.45
3.1.3.1 Conclusion
The values were just very similar to the results obtained using the old pole coil. After this the
concern was that the magnetic field sensor used for the pole coil measurement might be
defective but when measured without any sample on pole coil and at different kA/m it
traced the desired values. So the conclusion drawn was that the surrounding coil be used for
future measurements and for the problem with the pole coil measurements we are in talks
with the concerned company to provide as a solution
3.2 Measurement of NdFeB samples
Here the NdFeB samples were prepared using different grade NdFeB powders and a binding
agent (20% PVA) to hold the sample in solid form and give it stability.
The grades of the powder used are as follows:
1. MQP_Q, d50= 5.07 µm
2. MQP 14_12, d50=7.36 µm
3. MQP_B, d50=10.83 µm
3.2.1 Process for making NdFeb samples
Step 1: Taking the required quantity of NdFeB powder.
In this case as the properties of the samples were suppose to be measured using the
surrounding coil we had to make sure that the samples were thick enough to be able to carry
out the measurement so taking 6 g powder in order to make 3 samples was a feasible option.
Step 2: Based on the weight of the powder take 10% of 20% PVA solution.
As the weight of the powder was 6 g we used 0.6 g of 20% PVA solution as a binding agent.
Step 3:The powder and the PVA were mixed very finely so that the PVA binds properly with
the powder
Step 4: After the mixing the mixture was kept in a furnace for 20 min at 95°C in order to dry
the mixture and get it ready to produce the sample

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Step 5: After taking out the mixture from the furnace 2 g mixture was taken and pressed in a
press at a force of 4 t for 30 s giving the solid stable NdFeB sample
3.2.2 Readings
The readings for different grade samples using the surrounding coil are as follows:
Table 7: Perma graph readings for NdFeB samples for different powder grade
Weight (g) Dimension (dia*h mm) Br (T) Hcj (kA/m) Hcb (kA/m)
MQP_Q (3*1.2g with 10% of 20% PVA)
1.6 10*4 0.553 255.98 186.29
MQP_Q (3*2g with 10% of 20% PVA)
2 10*5 0.56 254.2 187.33
MQP 14_12 (3*2g with 10% of 20% PVA)
2 10*5 0.51 885.85 328.18
2.05 10*5 0.46 878.16 303.07
1.56 10*4 0.534 303.07 340.2
MQP_B (3*2g with 10% of 20% PVA)
2 10*5 0.593 665.67 350.01
2.04 10*5 0.603 669.29 357.64
1.72 10*4 0.61 673.35 361.12
Looking from the remenance values from table 7 it is clear that the values are very lower
than what one would expect for a NdFeB magnet. But here a fact needs to considered that
the sample does not totally contains NdFeB powder and has pores, which affects the density
of the sample and thus the remanence values. So the relative density of the NdFeB samples
had to be calculated and based on it compare the remenence values.
3.2.2.1 Calculation for Relative Density
The density of MQP_B grade powder is 7.59 g/cm3 and the dimensions of the samples are
either 10*5mm 0r 10*4mm. Using these two units the standard mass of the sample was
found as follow:
1.For 10*5mm sample
Density=Mass /Volume(πr²h)
7.59 g/cm³=Mass/ 3.14* [(1/2 cm) ^2] *0.5 cm (10 mm=1cm, 5 mm=0.5 cm)
Mass= 2.98 g
The sample just weighs 2 g so it was clear that the sample contains just 1.8 g NdFeB powder,
0.2 g PVA and the rest was air (0.98 g)
With 1.8g NdFeB powder the density is= 1.8g/ 3.14* [(1/2 cm)^2] *0.5 cm
=4.58 g/cm³
Therefore the relative density is= 4.58/7.59= 0.6042
Now taking standard remenance for MQP_B as 0.870 T and using the relative density the
expected remenance must be (0.870*0.6042= 0.525 T)

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2. For 10*4mm sample
Density=Mass/Volume(πr²h)
7.59 g/cm³ =Mass/ 3.14* [(1/2 cm)^2] *0.4 cm (10 mm=1cm, 4 mm=0.4 cm)
Mass= 2.38 g
The sample weighs 1.72 g so it was clear that the sample contains just with 1.548 g NdFeB
powder, 0.172 g PVA and the rest was air (0.66 g)
With 1.8g NdFeB powder the density is= 1.548 g/ 3.14* [(1/2 cm)^2] *0.4 cm
=4.93 g/cm³
Therefore the relative density is= 4.93/7.59= 0.6495
Now taking standard remenance for MQP_B as 0.870 T and using the relative density, the
expected remenance must be (0.870*0.6495= 0.565 T)
4 AFT ferrite Tapes
The tapes provided from AFT microwave GmbH will be used in the circulator as ferrite
layers. The tapes provided were of two categories, which are as follows:
1. NiZn 213: AFT RF10 015 with Bi2O3
2. NiZn 214: AFT RF10 015 without Bi2O3
Here the task was to carry out the sintering experiments on the tapes and see the results and
also calculate the shrinkage of the tapes using optical dilatometer.
4.1 Sintering experiments:
4.1.1 AFT RF10 015 with Bi2O3 900°C for 2 h
The sintering regime for this tape was as follows:
0°-500°C : 16 h
500°-900°C : 2 h 4 min
900°C : 2 h
900°-0°C : -
The results are shown in the form of pictures as follows:
1. Pressure sintering:
Green tape Sintered with pressure
Figure 10: Pressure sintering: Before and after images of AFT 10 015 with Bi2O3

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From the pictures you see that for the sintering process the tape was cut in different sizes,
placed over a zirconia tape and then on the aluminum substrate and for pressure sintering
the zirconia foil was also placed on the top of our ferrite tape along with few aluminum
substrate for the pressure. This whole assembly was put in a Furnace for the sintering
regime. The results were very bad as after the sintering process the ferrite tapes completely
broke down into pieces, which is not what we desire.
So the second approach was by applying less pressure on to the ferrite tapes and the results
are as follows:
Figure 11: Pressure sintering with less pressure: Before and after images of AFT 10 015 with
Bi2O3
It was observed that after the sintering process two out of the three tapes were completely
broken into pieces while one tape had just one broken piece while is not usual because all
the tapes are of same material and so all should show the same behavior.
4.1.1.1 Shrinkage Behavior
The shrinkage behavior was also very important in order to incorporate it into the
calculations and select the LTCC with similar shrinkage characteristics. For this purpose a
shrinkage behavior analysis was carried out using an Optical Dilatometer. The process was
very simple we cut a small piece of the ferrite layer place it on an aluminum substrate and
place it in the optical dilatometer instrument, adjust the focus and illumination. The regime
of the process was as follows:
1st zone: 43°-500°C at 1K/min
2nd zone: 500°-1050°C at 4K/min
3rd zone: 1050°-20°C at 20K/min

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Figure 12: Shrinkage curve dl/lo (%)for AFT 10 015 with Bi203
We also made screenshots at ever 30 s in order to calculate the shrinkage behavior later on
using origin and GNU image manipulation program. From the images, the dimensions of the
tape at different temperature between 100-1050°C were measured, in terms of pixels and
then taking the dimension at 100°C as standard; the percentage variation for the rest of the
temperature range were calculated and a graph was plotted with first differentiation of the
relative dimensions. The Shrinkage curve of the tape are shown in fig 12 and 13:
Figure 13: Shrinkage curve dl/dt (%/K) for AFT 10 015 with Bi203

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From the figure 12 & 13 it is clear that the shrinkage characteristics do not look good with
length continuously changing, which is not desirable, focus was on having a steady behavior
after a certain Temperature.
Thus it was concluded that the tape has some impurities and another new tape was needed
for the measurements.
4.1.2 AFT RF10 015 without Bi2O3 1300°C for 2 h
The sintering regime for this tape is as follows:
0°-500°C : 16h
500°-1300°C :
1300°C : 2 hours
1300°-0°C : -
The sintering process was very similar to that of 4.1.1 but the only difference was that the
temperature here was 1300°C and thus the furnace used was a high temperature furnace.
The result for the sintering process with less pressure are shown below in the form of
pictures:
Figure 14: Pressure sintering: Before and after images of AFT 10 015 without Bi2O3
4.1.2.1 Shrinkage Behavior:
The process was similar to the one used for 4.1.1 but the temperature regime differed in the
following way:
1st zone: 43°-500°C at 1K/min
2nd zone: 500°-1350°Cat 4K/min
3rd zone: 1350°-20°C at 20K/min.
But from the screenshots it was observed that the tape had some impurities due to which
even at 100°C it curled up showing signs of stresses in the tape and making it impossible to
plot the shrinkage graph.
4.2 Preparation of New Tapes
With the disappointing results from the sintering experiments a pure Ferrite powder (RF 10-
015) from AFT was ordered and was graded as AFT RF 10 015_2.

22
The first step was to measure the particle size of the pure Ferrite powder; which was done
on a Mastersizer.
4.2.1 Basic principle of the Mastersizer: The basic principle on which the instrument works is
that we disperse the powder in the way of a laser beam and because of the obscuration the
laser beam it diverts from it’s path and we have the detectors which measure this diversion
and based on the material properties we get the particle size readings.
4.2.2 Measurement process:
Step1: A very small quantity of powder was taken in a small glass flask and filled with 0.2%
Na-pyrophosphate solution. The reason behind using this solution instead of water was that
it gives good dispersion of particles
Step2: Now the solution was diluted with the use of an ultrasonic dispenser for 4mins at
40% intensity. The powder contains of primary particles, the aggregates and accumulates
with increasing in size respectively. The reason to do this was to break down accumulates
and aggregates and to have maximum amount of primary particles.
Step3: After the dispersion process, a small quantity of solution was added into the tank of
Mastersizer until the quantity was in the laser obscuration range. Once the quantity was in
the range we started the calculation and in within minutes we had the graph giving us the
particles size as d10, d50 and d90. The concern here was to get the particle size d50 in
between 0.6-0.7µm. However doing this procedure for the unmilled Ferrite powder we got
the particle size d50 as approx. 2µm. So in order to achieve the desired particle size the
powder was milled.
4.2.3 Milling process and Particle size measurement: The milling process used was Ball
milling. A flask of polymer was used so that the powder did not stick to it. In order to mill the
powder, the composition of powder, water and grinding balls used was in the ratio of 1:2:8.
The grinding balls used here were made up of ZrO2 and were 3 mm diameter in size.
To start with just 30 g of powder was taken and according to the ratio 60 g water and 240 g
grinding balls and the mixture was milled for 5 min at 400 rpm but the particle size
measured was 1.5µm which was way too high than the required so the milling times were
increase until we got the desired values. The particle sizes with increasing Milling times are
as follows:
Table 8: Milling Data for AFT RF 10 015_2 at 400 rpm with 3 mm grinding balls
400 rpm
Milling time (min) d50 (µm)
5 1.5
15 1.2
19 1.1
29 0.99
49 0.81
From the above results it is clear that we did not get the particle size in the desired range
and we did not wanted to go further as with 400 rpm and longer milling times might cause
wear of the grinding balls which was not desirable. So a different approach was tried with
lower milling speed and higher milling time i.e. 170 rpm for 200 min. The results are as
follows:

23
Table 9: Milling Data for AFT RF 10 015_2 at 170rpm with 3mm grinding balls
170 rpm
Milling time(min) d50(µm)
200 0.82
The above approach also did not give satisfactory results. Thus the new approach was to use
smaller grinding balls of 1mm diameter with the base that with smaller grinding balls we
can get finer milling of the powder and use higher milling speeds (400rpm). The results are
as follows:
Table 10: Milling Data for AFT RF 10 015_2 at 400rpm with 1mm grinding balls
400rpm, 1mmGB
Milling time (min)d50 (micrometers)
10 0.91
25 0.79
As the values from table 10 were close to the expected range, now the next step was to mill
the powder with 3% Bi2O3, which is the real material composition in order to make the
tapes. We used larger beaker with the composition as 70 g Ferrite powder, 120 g water and
480 g grinding balls (1 mm dia.). 3% Bi2O3 of 70 g powder means 2.1 g Bi2O3 in the mixture.
Four beakers were prepared with the same composition and were milled together at 400
rpm. The results are as follows; here with a milling time of 32 min we get the average
particle size as 0.66µm, which is our required size.
Table 11:Milling Data for AFT RF 10 015_2 with 3% Bi2O3 at 400 rpm with 1 mm grinding
balls
400 rpm, 1 mm GB with 3% Bi2O3
Milling time (min) d50 (µm)
16 0.87
32 0.66
4.2.4 Further steps:
4.2.4.1 Drying and collecting the powder:
Once the desired particle size was obtained, we had to drain the powder i.e. separate the
powder from the water and grinding balls. So a sieve of 630µm was taken kept above a big
bowl and the content from the beaker were emptied into the sieve, as the sieve size was 630
µm the grinding balls were restricted in the sieve while the powder was collected in the bowl
below the sieve. The complete structure was kept overnight in to a furnace at 95°C in order
to dry the powder. Even after the drying process there was still some powder stuck to the
grinding balls, which needed to be removed so the sieve was placed above a collector vessel
and the whole arrangement was kept on a vibrator where in we carried out vibration for 30
min at 2 mm amplitude. The powder obtained as a result was the powder with average
particle size 0.66 µm.
4.2.4.2 Magnetic properties
Few basic tests needed to be carried out in order to identify some basic properties, so the
palettes were made out of this powder and the process for it was similar to 3.2.1. The only
difference was that here 5% of 10% PVA solution was used. We took 6 g powders and mixed
0.32 g PVA solution and made palettes with 1 g mixtures and another with 1.2 g mixtures.
Now the palettes need to be sintered first. The regime was:

24
0°-900°C: 10K/min
900°C: 2 h
The magnetic properties measured for the two samples under Perma graph are as follows:
Table 12: Perma graph data for samples made from AFT RF 10 015_2
AFT RF 10
015_2
Weight (g) Dimension (d*h mm) Br (T) Hcj (kA/M) Hcb (kA/m)
1 9*3 0.187 4.68 4.57
1.2 9*4 0.255 4.31 4.26
4.2.4.3 BET Specific surface area measurement
BET Theory: The specific surface area of a powder is determined by physical adsorption of a
gas on the surface of the solid and by calculating the amount of adsorbate gas corresponding
to a monomolecular layer on the surface.
Sample preparation: Degassing: Before the specific surface area of the sample can be
determined, it is necessary to remove gases and vapours that may have become physically
adsorbed onto the surface after manufacture and during treatment, handling and storage. If
degassing is not achieved, the specific surface area may be reduced or may be variable
because an intermediate area of the surface is covered with molecules of the previously
adsorbed gases or vapours.
Principle: In the volumetric method, the adsorbate gas (nitrogen) is admitted into the
evacuated space above the previously degasses powder sample to give a defined equilibrium
pressure of the gas.
Actual Procedure:
Step1: Two Burettes one of station A and other of Station B were taken.The weight of the
empty burettes were measured first and then were half filled with the powder whose
specific surface area was to be measure and the burettes were weighed with the powder.
The difference between the weights gave us the weight of the powder.
Step2: This step involved degassing process explained above. The two burettes were fixed
into the holder at the degasser side. In the instrument the Degas-vacuum option was
selected from the control panel option. Once the system started evacuating and the pressure
was about 70-80 mm Hg, the two heating bags were put over the burettes with a
temperature set at 200°c and the burettes were heated for almost 1 h.
Step3: This involved measuring the weight of the burettes again and the difference of weight
here was the actual weight of the powder after the degassing process.
Step 4: This was the final step where the specific surface area was measured; the burettes
were fixed in the measuring station at respective A and B-side. The volume of the burettes
was decreased by inserting smaller burettes into the original burettes before fixing them
onto the measuring station. The purpose of doing this was that by reducing the absolute
volume we reduce the quantity of nitrogen required to measure the SSA.
Than the process: Analysis option -> run-> Setup 01- standard analysis setup-> Calculate
was followed and the values of weight of the powder for A and B, the density of the powder
were inserted.

25
After the process the results obtained were as follows:
Table 13: BET specific surface are measurement
BET Station A Station B
Sample Cell Number 7 8
Sample weight (g) 3.1650 3.7990
Sample Volume (mL) 0.6029 0.7236
Sample density (g/mL) 5.2500 5.2500
Adsorbate Nitrogen Nitrogen
5 point BET SSA (sq.m/g) 8.0632 8.0872
Single point BET SSA
(sq.m/g) 7.7515 7.8053
*SSA: Specific Surface Area
4.2.5 Conclusion:
After all these processes 500 g-milled powder was collected which had a particle size d50 of
0.65-0.73µm and was send further to make magnetic tapes.
4.3 Simplifying the plotting of shrinkage curve
The shrinkage curve plotted in 4.1.1.1 involved a time consuming process, which required
manual measurement of the pixels for each and every picture and than note the readings and
carry out the relative percentage shrinkage and than plot the graph. In order to simply the
process Lab-View vision assistant 2015 was used. This involved making a standard script in
lab assistant which even can be used for future cases and doing the batch processing for all
the images and getting the final results in form of text file, which can be imported into origin
to plot the graph.
The standard script is as follows:
 The starting temperature value picture was selected (in our case it is 500°C)
 Now the first thing done was that the brightness was changed to zero and the contrast was
increased to approx. 90 so that in later stage the reading of temperature values would be
simple.
 Now the Machine vision option in the tool bar was used to try to find the straight edges in
order to measure the vertical and horizontal distances. The two horizontal edges and two
vertical edges were found in a way that by measuring the distances between them we get the
length and height of the tape.
 Once the edges had been found and fixed, the caliper option from the machine vision option
was used in order to measure the distance between the edges.
 Now the final step in the script was to read the temperature value from each picture
automatically. For this OCR/OCV option from the Processing functions option in the left
window on the screen was selected. In order to read the Temperature all the characters that
are required to be identified need to be trained. For that the edit character set file option in
OCR/OCV was used. The idea was to have a sample image containing all the characters that
need to be identified in repetition of 5-6. Once the software knows the value it will
automatically read the values.
 Than for the final step Batch processing option form the tools options was selected, the path
for the images was chosen, the caliper readings were saved and the script was ran and we
had results for all the images, which we imported as text files in to origin and plotted the
graph easily.

26
A trial graph plotted using the above process is shown below and it is clear that with this
approach a good shrinkage curve can be obtained.
Figure 15:Shrinkage demo curve
5. NdFeB pastes
The purpose here was to make magnetic pastes used for screen-printing using different
NdFeB powders, AV 171 and Terpineol in different composition.
The compositions were as follows:
Table 14: Standard composition for preparation of NdFeB paste
25 g NdFeB paste
20 g NdFeB powder
3.5 g AV 171
1.5 g Terpineol
Table 15: Realisitic composition for preparation of NdFeB paste
NdFeB (g) AV 171 (g) Trepineol (g)
MQP 14_12 20.76 36.340 1.55
MQP_Q 22 3.85 1.65
MQP_B 20.45 3.58 1.53
S_0F10 paste
91 Ma% NdFeB
9 Ma% AV & Terpineol (7:3)

27
5.1 Process
The process involved taking the required quantity of Araldite AV 171 and mixing it with the
required quantity of Terpineol. These two components were mixed in a way that they bind
and form a paste and the last step was to add the required quantity of the NdFeB powder
and mix all the three components very well together until a homogenous paste is obtained.
5.2 Measurement of Magnetic Properties
This required formation of solid samples out of the paste. For these purpose Teflon palettes
were used, which contains a mold area where the paste was filled. These Teflon palettes with
the paste in them where kept in a furnace for 1hour at 140°C without any air circulation in
order to solidify the paste.
After removing the Teflon palettes from the furnace the Magnetic samples needed to be
removed out of the palettes, which was done by using a press. The samples obtained where
rough at edges and were not properly cylindrical. The samples need to be in a uniform
geometry in order to measure the magnetic properties using surrounding coil in Perma
Graph. This was achieved by using a grinder with a Silicon Carbide paper in order to grind
the unnecessary material and get proper cylindrical samples.
5.2.1 Readings
The values obtained by measuring the samples with a surrounding coil in a Perma graph are
as follows:
Table 16: Perma graph readings for NdFeB samples prepared from NdFeB paste for different
powder grade
Dimension (mm) Br (T) Hcj (kA/m) Hcb (kA/m)
MQP 14_12
13*8 0.234 850.73 163.45
11*8 0.307 837.14 210.41
11*8 0.291 804.96 198.34
MQP_Q
12*7 0.236 247.54 118.14
12*7 0.235 251.74 118.32
11*6 0.254 253.01 124.43
MQP_B
11*6 0.261 640.85 177.73
11*6 0.276 644.35 187.7
11*6 0.27 645.99 185.3
S_0F10
12*7 0.454 633.71 281.66
11*7 0.473 635.87 289.26
5.3 Problems
5.3.1 Viscosity
The paste that was obtained had high viscosity and the paste used for printing should have
low viscosity in order to be printed. The solution to this was changing the Terpineol amount
while keeping the ratio between the NdFeB powder and AV 171 constant. The different
compositions are as follows:

28
Table 17: Different composition for NdFeB paste with MQP_B powder for viscosity
MQP_B NdFeB (g) AV 171 (g) Trepineol (g)
1 8g 1.4 0.6
2 7.66 1.34 1
3 7.32 1.28 1.4
4 6.89 1.2 2
5.3.2 Terpineol content
The second problem was that after the heating process there was still some content of
Terpineol in the paste but as the boiling point of Terpineol is 217°C which was not desirable.
In order to compensate the effect of Terpineol we a thermal analysis of the paste was carried
out in order to see the mass change in the paste. The process of Thermal analysis is as
follows:
5.3.2.1 Instrument
TGA-92, Company: SETARAM
The basic structure of the instrument is that it contains a DTA (Differential Thermal
Analysis) probe, which has a reference crucible, which is empty, and a sample crucible
where in we fill the sample whose thermal analysis is carried out. This DTA probe is
connected to a very sensitive balance. The probe and the Balance are in a closed chamber
and the gas circulation is carried out in the probe chamber using a Mass Flow Controller
(MFC). The MFC is used to circulate a specific mixture of gas in to the probe chamber. The
other important thing to keep in mind is to keep the flow of argon gas always when you
carry out the thermal analysis.
5.3.2.2 Basic Principle
The Basic principle is that we have two Thermocouples one for the reference crucible and
the other for the sample crucible. Now based on the temperature changes chemical reaction
takes place, which can be either endothermic or exothermic, and this change is plotted as a
function of voltage giving peaks in the graph. On the other hand the balance gives variation
in mass due to the temperature change, which is also plotted in terms of voltage. The end
result shows the behavior of the sample in re-defined Temperature range along with the
mass change during the temperature range as a function of voltage
5.3.2.3 Process
The sample was a NdFeB paste (MQP_B) with 7.32 g NdFeB powder, 1.28 g AV 171 and 1.4 g
Terpineol. The platinum crucible was filled half as required. Before carrying out the analysis
it was made sure that the weight with and without Tare is +1 mg or -1 mg, which is a
prerequisite for the analysis. This was achieved using small lead balls and aluminum foil
balls to balance until the desired values were obtained. After this it was necessary to select
the mixture of gas that will flow in the probe chamber, in this case it was synthetic air with
nitrogen in the MFC1 and 21% oxygen in MFC2. At the same time the argon gas was also
allowed to flow into the chamber.

29
The measurement is carried out using thermal analysis software. In which the results were
plotted in the form of a graph. The sample was heated up to 300°C and the regime for this
Temperature range was as follows:
1st Zone: 20°C, 10 min
2nd zone: 20°-300°C, 10 K/s, and 28 min
3rd zone: 300°C, 1 min
4th zone: 300°-25°C, 9 min
The graph obtained is as follows:
Figure 16: Thermal analysis of NdFeB paste containing Magnetic powder, Terpineol and
Araldite
5.3.2.4 Conclusion
It is clear from figure 16 that there is no significant change in the mass of Terpinoel at 140 °C
(the temperature of the furnace to get the samples out of the paste).
So the next step was to move ahead with the screen-printing by selecting a paste out of the
four pastes with different composition mentioned in 5.3.1 and test in under VSM for the
magnetic properties.
5.4 Screen printing
For screen printing it is necessary that the paste need not be too thick or too fine. Thus from
the visual assessments of the four pastes as mentioned in 7.1, the pastes with 0.6 g and 1 g
Terpineol content were selected to be printed. The pastes were printed on an aluminum
substrate by sieving through a mask of micrometers.
The paste with 0.6 g Terpineol proved to be too thick to be printed. So the further printing
was carried out with the paste with 1 g Terpineol content. The first layer was printed and
the substarte was kept in a furnace for 30 min at 140°C in order to dry the paste so that
another layer can be printed on top of it. The purpose of multilayer printing was to have a
thick enough thin film for which measurements can be carried out on the VSM. So a second
layer was printed was over the dried layer and the substrate was again kept in the furnace
for another 60 min at the same temperature as before. At the end we have a good magnetic
film printed on the substrate.

30
5.5 VSM measurements
In order to measure the magnetic properties of samples in Perma graph using a surrounding
coil the samples needs to be thick enough i.e. in the range of mm. So in order to measure the
magnetic properties of magnetic tapes and films we used the VSM machine. We had three
samples for the measurement as follows:
1.) The sample obtained by screen-printing.
2.) Single layer of a commercial NdFeB tape cured at 140°C for 1 h without any air-
circulation.
3.) Stack of three layers of a commercial NdFeB tape cured at 140°C for 1 h without any air-
circulation
Table 18: Sample data for VSM measurements
Sample
width
(mm)
depth
(mm)
thickness(
)
weight
(mg)
1 3 3 90 4.2
2 5 5 390 48.9
3 5 5 860 117.8
5.5.1 Process:
This aim was to measure the hysteresis loop of the samples in plane and out of plane and
ideally both the loops should be same. Firstly the machine was calibrated for in plane
measurements with Ni probe of 5*5 mm dimensions. After the calibration the measurements
were made for all the three samples. The sample process was followed for out of plane
measurements. The results from the VSM measurements are as follows:
Figure 17: Magnetic moment vs magnetic field for a NdFeB single layer tape

31
Figure 18: Magnetic moment vs magnetic field for a NdFeB three layer tape
Figure 19: Magnetic moment vs magnetic field for a NdFeB screen printed tape on Al2O3
Substarte

32
6. AFT circulator with SmCo
Figure 20: Magnetic flux density over the surface of AFT circulator with SmCo
The geometry of this circulator used one Smco magnet of 1.3 mm diameter and 1.5 mm
height with a LTCC layer underneath the magnet of 50µm with a Ferrite layer of 200 µm
underneath the LTCC layer. Both the LTCC layer and the ferrite layer are 2.8 mm wide.
Carrying out the simulation in COMSOL and plotting the graph using Origin gave the
following result. The magnetic flux density measured here along the surface is at the middle
of the Ferrite Layer as shown in figure 17.
7. Circulator
Figure 21: Basic Circulator Geometry
After the project meeting it was decided that 4 ferrite layers will be used, each layer with
100µm and a LTCC layer at the top and bottom with also a thickness of 100µm, with both
having the width of 600µm and to have two NdFeB Tapes/Laminates/magnet one at the top
and other at the bottom but the dimensions were not fixed. So simulations were carried with
different dimensions keeping in mind a homogenous magnetic field is required over the
surface. To start with, the initial dimension used were 1 cm wide and 300µm height but the
results were not good as the requirement is to have homogenous magnetic field and flux
density in between 170-180 mT. So the next step was to vary the dimensions in order to
achieve these two goals. The standard geometry of the circulator is as follows:

33
7.1 Trial method: NdFeB (Variable Width & Height)
The simulation was carried out for the above shown geometry with two different remenance
one for standard 1.2 T and the other for 0.4 T or the commercially available NdFeB magnets.
The results obtained were not satisfactory as the flux density was very low for 0.4 T, which is
eventually going to be the remenance of the tapes, which will be used for the circulator. The
other problem was that the magnetic flux density was not homogenous over the surface of
the magnet. The next step was to vary the dimensions and look for the required values and
behavior. The results were as follows:
Table 19: Magnetic Flux density at 1.2 T & 0.4 T for NdFeB Magnet with variable height and
width used in circulator
Width
(cm)
Height
(micrometers)
Br: 1.2 T Bmax
(mT)
Br: 0.4 T Bmax
(mT)
1 300 150.7 50.23
600 244.5 81.5
1000 335.7 112
0.8 300 177.37 59.12
600 258.12 86.04
900 334.3 111.43
0.6 300 168.3 56.1
600 321.9 107.3
900 415 138.34
0.5 300 80.5 26.9
600 297.2 99
900 393.7 131.23
0.3 300 212.2 70.7
600 362.7 121
900 480.4 160.13
0.2 300 251.4 83.8
600 427.14 142.4
900 550.8 183.6
Figure 22: Magnetic flux density at the center of NdFeB tapes (0.3 cm wide) separated by a distance

34
Figure 23: Magnetic flux density at the center of NdFeB tapes (0.2 cm wide) separated by a distance
From the above readings it is clear that the desired values are obtained when the width is
either 0.3 or 0.2 cm and the height is 900µm. The conclusion drawn from these was that
higher the aspect ratio (width/height) lower the magnetic flux as with higher aspect ratio we
get max flux only at the edges of the magnet while it drops considerably at the middle of the
magnet that is not useful for our case. The graphs clearly indicate that even with 0.4 T
remanence a homogenous field over the surface of the magnet can be obtained and also the
flux density is according to the requirements
7.2 Symmetric Circulator Geometry
Figure 24: Magnetic flux density over the surface of Symmetric circulator Geometry

35
Figure 25:Magnetic flux density over the surface of Symmetric circulator Geometry with 2-
LTCC and 4-LTCC layers
Based on the results mentioned in 7.1, a simulation was carried out for symmetric circulator
geometry where the width and depth of all components were the same (w: 600µm, d: 600µm).
The height of the magnetic tapes was also 600µm while the height of the LTCC and Ferrite
layer remained the same as 100µm. This geometry gave very satisfactory results as shown in
the above figure where even with the remenance of 0.4 T we get a very homogenous field over
the surface of the magnet with flux density close to 210m T.
Now as this LTCC and ferrite layer structure was suppose to be incorporated in a multi-layer
structure for another use too, a simulation was carried with two LTCC layers on the top and
bottom of the ferrite layers instead of one. The results are shown in figure 21. It is clear from
the graph that incorporating another two LTCC layers, one on the top and another at the
bottom the flux density decreases considerably. For 0.4 T remenance it decreases from 210
mT to 150 mT.
8. Final Conclusion
The overall Learning from the internship was now I am very well acquainted with:
 COMSOL Multiphysics 5.1
 Origin
 Perma graph for hysteresis loop,
 Optical dilatometer
 Magnet and magnetic pastes preparation
 Milling process for magnetic powder
 Sintering process
 Particle size measurement
 Surface area measurement
 In addition basic knowledge of thermal analysis measurment, Lab-View vision assistant.
1. Based on the multiple simulations in COMSOL, we now have an idea for the optimum
geometry of the circulator component.

36
2. Based on the measurements on Perma graph we know that the measurements are
accurate with the surrounding coils but not with pole coils. The company has been contacted
to the solve the same problem and also the instrument gets heated up after2-3 readings
which requires the machines to be cooled down for a couple of minutes and than again carry
out the measurements.
3. The sintering process results were not satisfying for the first tape, so the new powder was
milled and send for the new magnetic tape preparation.
4. From the magnetic paste preparation we know that the Terpineol does not evaporate
completely which was confirmed by Thermal analysis results.
5. The further steps would be to analyze the hysteresis loop of NdFeB tapes on VSM for a
single layer and a triple layer stack and the screen printed film and correct the readings
Once the new ferrite tapes are received the shrinkage curve can be measured again and if it
is good then the best LTCC layer can be selected and the two components can be co-fired
together and the feasibility of the symmetric circulator geometry(7.2) can be tested

37
9.Appendix:Graphs
1. NdFeB magnet with iron backing 38
2. NdFeB magnet without iron backing 38
3. Magnetic flux density over the surface of NdFeb magnet
with iron backing 39
4. Magnetic flux density over the surface of NdFeb magnet
without iron backing 39
5.Magnetic flux density at the center plane for SmCo magnet
6.SmCo magnet separated by a distance, working temperature: 423 K 40
7. NdFeb multipole magnet with iron backing and pole distance 1 mm 41
8. NdFeb multipole magnet without iron backing and pole distance 1 mm 41
9. NdFeb multipole magnet with iron backing and pole distance 2 mm 42
10.NdFeb multipole magnet without iron backing and pole distance 2 mm 42
11. NdFeb plates separated by 1 mm, 1.2 T 43
12. NdFeb plates separated by 1 mm, 0.4 T 43
13. Magnetic flux density at the center plane for NdFeb plates
separated by 1 mm, 1.2 T 44
14. Magnetic flux density at the center plane for NdFeb plates
separated by 1 mm, 0.4 T 44
15. NdFeB Tapes w:0.2 cm separated by a distance 45
18. Field distribution for NdFeB Tapes w:0.5 cm separated by a distance 46

38
1. NdFeb magnet with iron backing
2. NdFeb magnet without iron backing

39
3.Magnetic flux density over the surface of NdFeb magnet with iron backing.
4.Magnetic flux density over the surface of NdFeb magnet without iron backing.

40
5.Magnetic flux density at the center plane for SmCo magnet separated by a
distance
6.SmCo magnet separated by a distance, working temperature:423 K

41
7. NdFeb multipole magnet with iron backing and pole distance 1 mm
8. NdFeb multipole magnet without iron backing and pole distance 1 mm

42
9. NdFeb multipole magnet with iron backing and pole distance 2 mm
10. NdFeb multipole magnet without iron backing and pole distance 2 mm

43
11. NdFeb plates separated by 1 mm, 1.2 T
12. NdFeb plates separated by 1 mm, 0.4 T

44
13. Magnetic flux density at the center plane for NdFeb plates separated by 1 mm,
1.2 T
14. Magnetic flux density at the center plane for NdFeb plates separated by 1mm,
0.4 T

45
15 NdFeB Tapes w:0.2 cm separated by a distance

46
18 Field distribution for NdFeB Tapes w:0. 5 cm separated by a distance

47
19 Field distribution for NdFeB Tapes w:0.3 cm separated by a distance
20 Field distribution for NdFeB Tapes w:0. 2 cm separated by a distance

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