Unfolding kinetic fragility in relaxor ferroelectrics

Abstract

The fragility parameter is one of the most important material constants that is extensively used in glass science, playing a central role in the enhancement of the understanding the glass formation process of disordered systems. Although fragility has been widely used, this concept has never been precisely defined and evaluated in relaxor ferroelectrics. Here, we have filled up this scientific gap. Based on a generalized Vogel-Fulcher-Tammann equation, the fragility parameter is introduced for relaxor ferroelectrics. The new formulation has been quantitatively assessed by combining dielectric spectroscopy and pyroelectric measurements on canonical relaxors. A clear correlation between the fragility and a new local structural heterogeneity related order parameter elucidates new information about the ferroelectric order of relaxor ferroelectrics. A new pathway to disentangle relaxation phenomena in other relaxor ferroics could have opened.