Microwave absorption properties of strontium hexaferrite for stealth applications

1. Strontium Hexaferrite as Microwave Absorbing
Material
Presented By:
Lalit Katariya
Program: M.Sc Physics
Roll No: M20PH010
M.Sc Project Presentation on
Department of Physics
Indian institute of Technology, Jodhpur
Project Supervisor:
Dr. Sampat Raj Vadera
Deputy Director and Professor,
Indian institute of Technology, Jodupur
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2. Contents
• Introduction
• Mechanism of Microwave Absorption
• Fundamentals of Analysis
• Strontium Hexaferrite
• Sample preparation
• Sol-gel auto-combustion
• Characterization
• Results
• Conclusion
• Acknowlegment
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3. Introduction
• Microwave Absorbing Materials: Functional materials which can dissipate electromagnetic wave by
converting it into thermal energy.
• Used in:
 Stealth Technology
 Communication
 Information Processing Technologies
• Nano-materials are suitable for microwave absorption application because of its intrinsic properties
like small size and large surface area etc.
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4. Mechanism of Microwave Absorption
• Microwave contains:
 Electric field
 Magnetic field
• For absorption purpose, material must interact
with one the Electromagnetic field or both i.e. :
 Dielectric loss
 Magnetic loss
• Properties of Medium for microwave absorption
: ε, μ, σ
• For destructive interference
Path difference = /2
• Thickness of the material = /4
Wang C, Murugadoss V, Kong J, He Z, Mai X, Shao Q, Chen Y, Liu
C, Angaiah S, Guo G.. Carbon 2018;140:696e733. 4
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5. Mechanism of Microwave Absorption
• The complex permittivity,
• where ɛ’ quantifies the lossless interaction
between the waves and Materials and ɛ”
describes the dissipation pathway in which there
will be generation of heat due to displacement of
subatomic particles.
• Magnetic loss is described by complex
permeability,
μ’ quantifies the lossless interaction between the
magnetic field of EMW and μ” quantifies the
lossy interaction
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Dielectric/magnetic loss coupling :
The attenuation of one of the electromagnetic fields has an associated effect on the other. so the
attenuation of electromagnetic energy can be done by either through interaction with electric field ,
magnetic field or both

6. Fundamentals of Analysis
• Loss tangents- represents the loss rate of energy
or a efficiency parameter for overall energy
transfer
• Dielectric loss tangent:
• Magnetic loss tangents
• Performance Evaluation
• Refection loss: log ratio of the incident power
with respect to reflected power
• Reflection Coefficient
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tan
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For good dielectric tan δε<<1
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log
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tanh(
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7. Fundamentals of Analysis
• Response to incident electromagnetic wave is
quantified by a scattering parameter(s).
• For reflection/transmission methods, there is only
two scattering parameter to be experimentally
determined, S11 and S21 parameter.
• For transmission/reflection lines, the utilization
of a two-port device allows for the quantification
of electromagnetic response.
• the S-parameters for the 2x2 matrix ,
where S12 is signal response from port 1
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
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22
21
12
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S
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Port1
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Port 2
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Eincident

8. Strontium Hexaferrite
• Ferrites are nanostructured ferrimagnet oxides.
• Composed of metal oxide and ferric oxide.
• Hard Ferrites Having High Coercivity.
• Strontium Ferrites is suitable for Microwave absorption because of:
 its Magnetic Properties
 High Coercivity
 Unilateral Magnetic Anisotropy
 Also low cost Materials
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9. Sample preparation
• Sol-gel Process:
Reaction taking place during the process follows:
Sr(NO3)2 + Fe(NO3)39H2O + C6H8O7 + NH4 OH
SrFe12O19 + NH4NO3 + CO2 + H2O
Sr: 0.4183g + Fe:9.581g + Citric acid: 9.875g +
DI:100ml 90°C For 4h gel formation
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rise temp. to
200°C
Powder form via
Autocumbuston
Anneal at 950°c
for 1 hr
Strontium ferrite
nanoparticles

10. Sol-gel Auto-Combustion
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11. Characterization
• X-Ray Diffraction:
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Scanning Electron Microscopy

13. Characterization
• UV Visible spectroscopy
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FTIR Spectroscopy

14. Results
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Dielectric and Magnetic loss Measurement result from Vector Network Analyzer

15. Conclusion
• Xrd result confirmed M-type Strontium Hexaferrite
• Using SEM particle size is in Micrometer and EDAX confirmed the elemental Composition of
Strontium Hexaferrite
• The FTIR spectra of strontium hexaferrite powders Reveals the formation of ferrite phase. It shows
three signature transmittance peaks of hexaferrite at ~ 439 cm-1, 552 cm-1 and 600 cm-1 which are
same when compared with other published works
• UV visible shows maximum absorbance between 300-600nm.
• VNA studied at the range of between 8-12 GHz. The graph of Dielectric and magnetic tangential loss
with frequency has been drawn.
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16. Acknowledgement
I would like to express my gratitude to
• My supervisor Dr. Sampat Raj Vadera for his exemplary guidance and constantly encouragement
throught the project
• My Senior PhD Scholar Nishtha Vats
• Dr. Partha Ghosal,DMRL
• Dr. Lokesh saini, DLJ
• Dr. RK Jani, DLJ
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17. References
1. Chen L, Ong C, Neo C, Varadan V, Varadan V. Microwave electronics: measurement and materials
characterization. John Wiley and Sons; 2005.
2. Griffiths D. Introduction to electrodynamics. Cambridge University Press;1999.
3. Naito Y, Suetake K. Application of ferrite to electromagnetic absorber and its characteristics Wave.
IEEE Trans Microw Theory Tech 1971;19:65e72.
4. Kasap S. Principles of electronic materials and devices. McGraw-Hill; 2018.
5. Steer M. Microwave and RF design: a systems approach. Scitech Publishing; 2013.
6. Malhotra S. , Chitkara and Sandhu S., Microwave Absorption Study of Nano Synthesized Strontium
Ferrite Particles in X Band , International Journal of Signal Processing, Image Processing and Pattern
Recognition Vol.8, No.10 (2015), pp.115-120
7. https://doi.org/10.1515/mgmc-2020-0004
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18. Thank you
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