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 ( T C ) 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- T C effects could lead to the formation of nanodomains in relaxors, it is the former that leads to the appearance of Burns temperature T B , 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: T B , T * and the freezing temperature T f . This work unravels the detailed physical origin of the relaxor behavior and offers deep microscopic insight into relaxors.