Outline Motivation Dielectric properties of materials Ferroelectric and Antiferroelectric Electrocaloric Effect (EC) Sample preparation method Characterization techniques Result and Discussion Future Work References

1. Influence of La3+ substitution on dielectric, ferroelectric and electrocaloric properties in
AgNbO3
Under the supervision of
Dr. Satyendra Singh
Special Centre for Nanoscience
By
Mohammad Azam

2. o Motivation
o Dielectric properties of materials
o Ferroelectric and Antiferroelectric
o Electrocaloric Effect (EC)
o Sample preparation method
o Characterization techniques
o Result and Discussion
o Future Work
o References
Outline

3. o AgNbO3 is one of the eco-friendly lead-free materials
o AgNbO3 is a perovskite structure.
o AgNbO3 lead free ferroelectric and antiferroelectric
o Very less modified reported for electric properties
o No electrocaloric effect is reported
Motivation
J.F. Scott et al

4. o Dielectrics are the electrically insulating materials those have
permanent dipole moments.
o Dielectric materials are polarized by the applied field.
o Dielectrics are important for explaining various phenomena in
in electronics, optics, solid state physics and cell biophysics .
o dielectric materials are utilized in capacitors, memories,
sensors and actuators etc.
E=0 E >0
Dielectrics materials
K. C. Cao et al.

5. o Ferroelectric materials have spontaneous polarization
and that can be reverse under applied external field.
o Antiferroelectric materials with adjacent dipoles
oriented in antiparallel directions have a double
polarization hysteresis loops.
Ferroelectric and Antiferroelectric
L.Peng et al.

6. o The electrocaloric effect is a phenomenon in which a material
shows a reversible adiabatic temperature change under an applied
electric field.
Types of EC
Positive EC
Co-existence of
both EC
Negative EC
Electrocaloric Effect (EC)
Z. Yao et al.

7. Electrocaloric Effect (EC)
P. Z. Ge et al.

8. Source of Image :- Junye Shi et al.
(a) Indirect method (Maxwell’s Relation)
(b) and (c) Direct method measurement
∆𝑆 = −
1
𝜌 𝐸1
𝐸2 𝜕𝑃
𝜕𝑇 𝐸
𝑑𝐸
∆𝑇 = −
1
𝜌𝐶𝑃 𝐸1
𝐸2
𝑇
𝜕𝑃
𝜕𝑇 𝐸
𝑑𝐸
Electro caloric measurement method

9. Objectives
o To synthesize the lead-free perovskite material (AgNbO3).
o Try to increase the value of the dielectric constant, decrease the dielectric loss with
different percentage of La.
o Calculate electrocaloric effect AgNbO3 and improve the electrocaloric effect by
different composition.

10. Sample Preparation Methods
Grinding using the mortar and pestle
Calcination of properly mixed powder
at 9000 C
Making pellets using die and pressure
machine
Electroding using silver paste
Sintered of the pellets at 11000 C
Weight the chemical using weight
machine
Sakurai et al.

11. (1) (2)
(5)
(4)
(3)
Characterization techniques

12. Average crystallitesize of D =
k λ
βcosθ
Scherrer Equation
Crystal Structure Study

13. Raman Study of Ag(1-x)LaxNbO3

14. ϵr =
Cd
Aϵ0
=
ϵ′′
ϵ′
tan ߜ
Dielectric Properties Study

15. Ferroelectric study of Ag(1-x)LaxNbO3
Figure 36: Polarization verses electric field at different
temperature for Ag(1-x)LaxNbO3 with x =0, 0.005, 0.01 and 0.02.
Figure 35: Variation of polarization with electric
field at room temperature forAg(1-x)LaxNbO3 with
x=0, 0.005, 0.01 and 0.02.

16. Ferroelectric study of Ag(1-x)LaxNbO3
Figure 37. Variation of maximum polarization
with temperature for Ag(1-x)LaxNbO3 with x=0,
0.005, 0.01 and 0.02.

17. Antiferroectric properties of AgNbO3

18. ∆𝑆 = −
1
𝜌 𝐸1
𝐸2 𝜕𝑃
𝜕𝑇 𝐸
𝑑𝐸
Electrocaloric Effect Study in La doped AgNbO
∆𝑇 = −
1
𝜌𝐶𝑃 𝐸1
𝐸2
𝑇
𝜕𝑃
𝜕𝑇 𝐸
𝑑𝐸

19. Result and Discussion
o The crystal structure and phase purity were investigated of Ag(1-x)LaxNbO3 with x = 0, 0.005, 0.01 and 0.02
samples by X-ray diffraction powder study. Patterns of XRD Ag(1-x)LaxNbO3 with x = 0, 0.005, 0.01 and 0.02 all
these four composition have shown orthorhombic perovskite structure and lattice parameter a = 5.553 Å, b =
5.606 Å and c = 15.653 at room temperature. Equated with AgNbO3, the (114), (024), (220), (133), and (137)
peaks of Ag(1-x)LaxNbO3 with x = 0, 0.005, 0.01 and 0.02 respectively shift to higher angles, showing the reduced
lattice parameters with increasing the La.
o This shows that whole the internal vibration related to NbO6 octahedral between 150 cm-1 to 900 cm-1. Due to
the presence of the NbO6 octahedron stretching vibration the peaks 577 and 527 come. While the 258 peaks
are associated with the Nb5+ cation shift and NbO6 octahedral tilting. The peak 258 shows shifting to lower side
wave numbers as the concentration of La increasing. That tells us the combination of La decreases the Nb5+
cation shift and softens the bonding vibration of Nb–O. The 257 peaks gradually weaken gone with the rise of
La concentration, which may have caused the higher symmetry. It should be observed that all peaks become
fade in intensity and wider in outline with the increasing of the La content.

20. o The phase transition temperature of AgNbO3 was recorded at 340 K, 440, 623 K. With doping of La The calculated
real part of the dielectric constant was 1930 at 623K for 1kHz. This value decreases with a doping concentration of
La in AgNbO3. We observed that phase transition temperature shifted towards the low temperature side by increasing
doping percentage.
o The temperature dependent PE hysteresis loop measurement was done by PE Loop Tracer System from low
temperature to high temperature range according to the transition temperature of sample. The polarization was
measured for the AgNbO3 was 14.5 μC/cm2 at 115 kV/cm which varies with frequency and temperature in double
hysteresis loop. We observed the polarization was decreasing with increasing of La concentration in AgNbO3
o We calculated a large ECE that exists for AgNO3 which was calculated using Maxwell’s equations. ECE measured
Negative of ΔT for all compositions. Doping of La in AgNO3 does not give much positive effect on ECE. The value of
ΔS = -0.85 J/Kg. K and ΔT = -1.014 K at a field of 70 kV/cm for pure. The value of ΔS = -0.80 J/Kg. K and ΔT = - 0.80 K
at field of 70 kV/cm for La-doped AgNbO3.
Continue..

21. Future Work
o The ECE could be high if we would apply high electric field.
o We can modify ECE by using various trivalent element at a Ag site.
o To convert pallets in to thin film the electric properties can enhanced.
o AgNbO3 can used in high energy devices.
o We can make small cooling devices using thin film.

22. References
1. J.F. Scott, Electrocaloric materials, Annu. Rev. Mater. Res. 41 (2011) 229–240.
2. L.Peng, H.Q.Fan, Q.Zhang, A giant electrocaloric effect in nanoscale antiferroelectric and ferroelctric
phase coexisting in arlaxor Pb0.8Ba0.2ZrO3 thin film at room temperature Adv.Funct.Mater. 23(2013)
2987-2987.
3. Z. Yao , Z. Song , H. Hao , Z. Yu , M. Cao , S. Zhang , M. T. Lanagan and H. Liu , Adv. Mater., 2017, 29 ,
1601727
4. K. C. Cao, Dielectric phenomena of solids.
5. P. Z. Ge, X. G. Tang, Q. X. Liu, Y. P. Jiang, W. H. Li, and J. Luo, “Energy storage properties and
electrocaloric effect of Ba0.65Sr0.35TiO3 ceramics near room temperature,” J. Mater. Sci. Mater.
Electron., vol. 29, no. 2, pp. 1075–1081, 2018, doi: 10.1007/s10854-017-8008-x.
6. Sakurai H., Yamazoe S., and Wada T., (2010), “Ferroelectric and AntiferroelectricProperties of AgNbO3
Films Fabricated on (001), (110), and (111) SrTiO3 Substrates by Pulsed Laser Deposition,” Appl. Phys.
Lett., 97, 042901, 3pp