Ba(Ti1−x,Zrx)O3 relaxors: Dynamic ferroelectrics in the gigahertz frequency range

Abstract

Relaxor ferroelectrics are of great scientific and technological significance as they exhibit large and unusual responses to external stimuli. Their hallmark features are broadness and frequency dispersion of the peak in the temperature dependence of the dielectric constant. Both are believed to originate from the dynamics of polar nanoregions. We apply first-principles-based molecular dynamics to resolve the gigahertz electric response of dynamically poled $\mathrm{Ba}({\mathrm{Ti}}_{1\ensuremath{-}x},{\mathrm{Zr}}_{x}){\mathrm{O}}_{3}$ ferroelectric relaxors that remained overlooked so far. We find that (i) the hallmark relaxor features continue to persist even in the dynamically poled structures, but do not necessarily originate from the polar nanoregions dynamics; (ii) dynamically poled samples exhibit polarization aging which leads to the frequency dependence of both remnant polarization and the Curie temperature; (iii) ``dynamical'' nature of the latter naturally explains the frequency dependence of the dielectric susceptibility maximum in dynamically poled $\mathrm{Ba}({\mathrm{Ti}}_{1\ensuremath{-}x},{\mathrm{Zr}}_{x}){\mathrm{O}}_{3}$; and (iv) incorporation of the polarization aging into dielectric susceptibility expression explains its enhancing contribution in an intuitive way.