Role of point defects in the formation of relaxor ferroelectrics

Abstract

Relaxor ferroelectrics are engineered by doping a large amount of point defects into normal ferroelectrics. The point defects create nanoscale compositional heterogeneity, which in turn lead to local Curie temperature (TC) variation and random local electric and strain fields. However, it is still unclear about the individual roles played by each of these effects in converting a normal ferroelectric into a relaxor. In this study we distinguish these effects by carryout computer simulations using the phase field method. We find that although both the local-field and local-TC effects could lead to the formation of nanodomains in relaxors, it is the former that leads to the appearance of Burns temperature TB, the latter that leads to the appearance of the intermediate temperature T*, and a combination of the two allows one to model all three characteristic temperatures of a relaxor reported in experiments: TB, T* and the freezing temperature Tf. This work unravels the roles of point defects in the formation of relaxor ferroelectrics and offers deep microscopic insight into relaxors.