Studies of Ferroelectric and Multiferroic Behavior in [Ba(Zr,Ti)O3]1-y:[CoFe2O4]y System

MUHAMMAD USMAN, . (2015) Studies of Ferroelectric and Multiferroic Behavior in [Ba(Zr,Ti)O3]1-y:[CoFe2O4]y System. Doctoral thesis, Quaid-i-Azam University, Islamabad.

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In this thesis we report the ferroelectric relaxor behavior of the zirconium doped barium titanate BaZrxTi1-xO3 solid solutions and their composite with Cobalt ferrite. BaZrxTi1-xO3 ceramics of the several compositions (0 ? x ? 0.8) have been prepared by conventional solid state synthesis route. Dielectric behavior of the BaZrxTi1-xO3 ceramics has been studied in the temperature range from 300 K to 10 K at various frequencies in the range 0.2-500 kHz. It was observed that for composition where x ? 0.3 the dielectric response show a diffused dielectric transition with decreasing temperatures. Furthermore the dielectric peak shows a strong frequency dependence moving towards higher temperatures for increasing frequencies. We discuss dependence of the dielectric constant on temperature, frequency and concentration in term of correlations among the polar nano regions. By considering the relaxor ferroelectrics as an analogue to classical magnetic spin glass system, we have analyzed the relaxor behavior within the mean field theory by estimating the Edward-Anderson order parameter EA q . We find that EA q calculated for the different concentrations obeys a scaling behavior () n mEA TTq /1 ?= , where Tm are the respective dielectric maxima temperatures and n = 2.0 ± 0.1. The frequency dependence of the EA q is also consistent with the above mentioned picture. </br> Magnetoelectric composites were prepared using conventional sintering.BaZrxTi1-xO3 was used as the relaxor ferroelectric material and the ferrite CoFe2O4 was used as the magnetostrictive component. We report the effect of magnetic field on the dielectric response in the relaxor ferroelectric and ferromagnetic composite [BaZr0.5Ti0.5O3]0.65:[CoFe2O4]0.35. Relaxor characteristics such as dielectric peak temperature and activation energy show a dependence on applied magnetic fields, viz. the dielectric peak shifts to higher temperature with increasing magnetic field. This is explained in terms of increasing magnetic field induced frustration of the polar nano regions comprising the relaxor. The results are also consistent with the mean field formalism of dipolar glasses. It is seen that the variation of the spin glass order parameter EAq (T) with applied magnetic fields is consistent with an increased frustration and earlier blocking of polar nano regions.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Ferroelectric , Multiferroic,Behavior [Ba(Zr,Ti)O3]1-y:[CoFe2O4]y System
Subjects: Q Science > QC Physics
Depositing User: Unnamed user with email
Date Deposited: 26 Oct 2017 03:45
Last Modified: 26 Oct 2017 03:45

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