Critical slowing down of polar nano regions ensemble in Gd3+-substituted PbMg1/3Nb2/3O3 ceramics

Abstract

Investigations on Gd-substituted lead magnesium niobate (Pb1-xGdxMg(1+x)/3Nb(2-x)/3O3; varying x = 0.01–0.1) ceramics have revealed critical slowing down of the polar nano regions (PNRs) ensemble into a “super-dipolar glass state” for higher Gd-substitution x ≥ 0.05. Low temperature electric field induced polarization switching study (P-E) has revealed a sharp decrease in the remanent polarization up to x = 0.03, which strengthen the critical slowing down of polar nano-domains dynamics, suggesting a reduction in the correlation between or within polar nano regions (PNRs) leading to a reduction in its size. Bright field imaging by using transmission electron microscope has also confirmed the reduction of the size of polar nano regions with increasing “x.” Selected area electron diffraction pattern along ⟨110⟩ unit axis has revealed enhancement in intensity of the superlattice reflections spot at ½ ½ ½ along ⟨111⟩ unit axis with increasing “x,” which is associated with the enhancement of chemical ordered regions and correlate well to enhancement in the degree of diffuseness parameters “δA” determined from fitting of the temperature dependent dielectric constant ε(T) plot above the dielectric maximum peak (εmax). The enhanced “δA” for x ≥ 0.05 is due to additional disorder created by the Gd-ions substitution at the Mg-site, which is consistent with the phase and microstructural analysis. Fitting of frequency dependent Tm (temperature of εmax) to the power law of critical dynamic has revealed realistic pre-factor fitting parameters for x ≥ 0.05 suggesting critical slowing down of the polar nano-domains dynamics ensemble resulting in super-dipolar glass state.