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Applicant:
Indian Institute of Technology (IIT) Patna 
Author:
L. K. Kumar, R. Pandey, S. Kumar, S. Kumari and M. Kar 
Corresponding Authors:
Manoranjan Kar 
DOI #:
https://doi.org/10.1007/s10854-019-01288-y 
Title:
Evidence of compositional fluctuation induced relaxor anti-ferroelectric to antiferroelectric ordering in Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3 based lead free ferroelectric 
Journal:
Journal of Materials Science Materials in Electronics 
Year:
2019 
Volume:
Page:
095521 
Keywords:
compositional fluctuation, antiferroelectric ordering 
Abstract:
The high temperature electrical phase transitions of (1 − x) Bi0.5Na0.5TiO3–(x) Bi0.5K0.5TiO3 (x = 0.10, 0.15, 0.20, 0.25, 0.30 and 0.35) relaxor ferroelectrics have been investigated by employing the dielectric spectroscopy technique. The Rietveld refinement of the XRD patterns reveals the increase of the lattice distortion (c/a) from 1.001 to 1.006 in the tetragonal crystal symmetry (P4mm) with the increase of the BKT (x = 0.10, 0.15, 0.20, 0.25, 0.30 and 0.35) mole fraction. The different bonds vibration (Bi³⁺/Na⁺/K⁺–O and Ti⁴⁺–O) related to phonon modes have been studied by analyzing the Raman spectra. The relaxor antiferroelectric ordering temperature (Td: depolarization temperature) of Bi0.5Na0.5TiO3 (BNT) reduce from ~ 200 to ~ 91 °C with the increase of the BKT mole fraction. This observation is well correlated to the formation of polar nanoregions (PNRs) due to the compositional fluctuation in the local crystal structure. Also, Td varies with the frequency of the applied electric. It suggests the presence of the PNRs and, subsequently exhibits the relaxor ferroelectric behavior. The activation energy to activate the PNRs reduces from 2.573 to 2.383 meV with the increase of the BKT mole fraction in the solid solutions. Reduction in remanent electrical polarization and the electrical coercive field in temperature dependent ferroelectric hysteresis loops suggest the relaxor antiferroelectric behavior of the solid solutions (x ≥ 0.15) near the depolarization temperature 
Entered by:
Venkata Dantham on 2020-08-02 
 
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