Synthesis and charecterization on Ferroelectric material BaTiO2

1. DATE OF PRESENTATION 9th NOVEMBER 2016

2. SYNTHESIS AND CHARACTERIZATION OF
FERROELECTRIC MATERIAL
Ba1-xSrxTiO3
Shashi Kumar
M.Sc. (Applied Physics) 3rd semester
Department of Applied Physics
IIT(ISM), Dhanbad.
Under the Supervisor
Dr. Manoranjan Kar,
Department of Physics
IIT Patna,Bihar-801103

3. Introductions:-
 Ferroelectric - A material that shows spontaneous
and reversible dielectric polarization without
externally applied field
 Barium strontium titanate (Ba1-x SrxTiO3, BST) is one the
most important ferroelectric materials, it is a ceramic
compound.
 Barium strontium titanate (BST) has been the most
intensively investigated because of its high dielectric
constant, low dielectric loss and good thermal stability

4. Barium titanate (BaTiO3) are crystalline perovskite
structure . The models for many ABO3 materials which
are very important in ferroelectrics.
Perovskites
A
O
B

5.  BST can exist in five phases, depends from high
temperature to low temperature:-
1. Above 120oC BaTiO3 is cubic (non-polar)
Ba
O
Ti

6. BaTiO3
 From 120oC down to ~5oC, there is a distortion to a
tetragonal phase.
 All of the cube directions can undergo this type of
distortion:

7. BaTiO3
 From 5oC down to around -90oC the structure is
orthorhombic. There are 12 possible orientations.

8. BaTiO3
 Finally the lowest temperatures yield rhombohedra
(distortions along the body diagonal).
 There are 8 equivalent distortion directions.

9. FINALLY

10. Experimental Detail
 Here two standard material preparation method will
be explained.
I. Sol - Gel Method
II. Solid State Method.
1) A sol is a dispersion of the solid particles (~ 0.1-1 μm)
in a liquid where only the Brownian motions suspend
the particles. A gel is a state where both liquid and
solid are dispersed in each other, which presents a
solid network containing liquid components.

11.  For Better understanding take the example of sol- gel
method (by preparing Barium hexaferrite using sol gel
method )

12. 2 ) Solid State Method:- BST powders were commonly
prepared by solid-state reaction
 In this method all the weighing process of the molecules
are same as in the sol –gel method after that mix all the
raw materials in a beaker. The mixture was grinded using
mortar pestle for 4 hours.
Mortar pestle for grinding the BaxSr1-xTiO3
(X=0.00,0.20,0.4,0.50,0.60,0.80,1).

13.  The grinded mixed powder was heated at 1250°C in the
furnace for 10 hours
 The crystalline phases of the sample were examined by
X-ray Diffraction (XRD)
APPLICATION OF BST:-
BST is widely used because it have
1. high permittivity
2. low dielectric losses
3. BST has a variety of electronic applications in
multilayer and voltage-tunable capacitors
4. microwave phase shifters
5. Oscillators
6. uncooled infrared sensors and so….

14. Characterization Techniques:
XRD
 Fourier Transform Infrared spectroscopy
(FT-IR)
Dielectric Measurement

15. XRD:-
We can use XRD to determine:-
 Phase Composition of a Sample
 Unit cell lattice parameters and Bravais lattice
symmetry
 Residual Strain (macrostrain)
 Crystal Structure
Crystal structure determination
Monochromatic X-rays Many s (orientations)
Powder specimen
POWDER
METHOD

16.  The Scherrer’s equation was published in 1918.
Scherrer use the formula to estimate the crystallite size
of nanophase material which is given by,
 The Scherrer constant K actually varies from 0.62 to
2.08
2nd is Willianson Hall Method :-
This approximate formulae for size broadening, βL, and
strain broadening, βe , with respect to Bragg angle, θ

17.  Here by plotting βtotcosθ versus sinθ we obtain the
strain component from the slope (Cε) and the size
component from the intercept (Kλ/L). Such a plot is
known as a Williamson-Hall plot θ and β can be
calculated by XRD pattern of the sample using origin
software β(FWHM)

18. Fourier Transform Infrared spectroscopy (FT-IR):
 What information can FT-IR provides?
 It can identify unknown materials
 It can determine the quality or consistency of a sample
 It can determine the amount of components in a
mixture
 (FTIR) is a technique which is used to obtain an
infrared spectrum of absorption or emission of a solid,
liquid or gas

19. Dielectric Measurement:-
 For dielectric measurements of any samples first we
have to make pallets of that material with the help of
pelletizer
 The surface of the disc shaped pallets was coated with
silver paste (T-10112, Metalor Technologies UK Ltd.),
and sintered at 250◦c for two hours
Image of Impedance Analyzer (N4L PSM 1735)

20.  Impedance spectroscopy Purpose:- Exploring the
electrical behavior of a microcrystalline solid sample as
function of an alternating current (ac) with a variable
frequency.
RESULTS AND DISCUSSIONS :-
FIG 1.

21.  FIG 2.

22.  FIG 1. :- The XRD PATTERN OF Ba1-xSrxTiO3(X=0.0,0.2,0.4,0.5,0.6,0.8,1.0)
at room temperature.
 FIG 2. :- The XRD peaks shift of Ba1-xSrxTiO3
(X=0.00,0.20,0.4,0.50,0.60,0.80,1.0)at room temperature.

23. fig 3 Rietveld refinement of Ba0.8Sr0.2TiO3 XRD pattern
(Refine parameters:a=b= 3.979(75)A0, c= 3.998(93)A0,Goodness fit(κ2)=2.39,space
group=P4mm)

24.  Impedance Spectroscopy :- impedance spectroscopy is
a technique in which the dielectric properties as a
function of temperature, frequency and time are
measured.
 Phase transitions can also be identified using this
technique Phase transitions can also be identified using
this technique
 The dielectric constant of the material is related to its
capacitance as
 Imaginary permittivity is calculated by ε’’= ε’tanδ

25. fig4. The Real part of impedance of BaTiO3 with
frequency variation at selected temperature

26. fig5. The imaginary part of impedance of BaTiO3 with
frequency variation at selected temperature

27. fig 6. The Real part of dielectric constant of BaTiO3 with
frequency variation at selected temperature.

28. fig 7.The imaginary part of dielectric constant BaTiO3
with frequency variation at selected temperature.

29. Fig 8.The Real part of dielectric loss of BaTio3 with
frequency variation at selected temperature.

30.  Fig 7. shows that real part of the impedance is high at
low frequency, after 1KHz frequency the impedance is
going to drastically decrease with the high frequency
 Decrement of impedance is due to effect of polarization
 FIG 8. it shows the dielectric loss (tan δ)
 The peak position of sample BaTiO3 shift towards
higher frequency with the increase in temperature.
 For Fig 6 and Fig 7 , At higher frequencies, both, ε’ and
ε’’ become almost constant i.e. frequency independent
region.