Temperature Dependence of Diffuse Scattering in PZN

Abstract

Structural disorder seems to relate to the useful physical properties of ferroelectrics and relaxors. One such material is PZN, \(\hbox{PbZn}_{1/3}\hbox{Nb}_{2/3}\hbox{O}_{3}.\) To explore what aspects of the disorder are specific to the polarized state, the temperature dependence of diffuse scattering in PZN has been investigated. The data were collected using both neutron and X-ray single crystal experiments in a range of temperatures from 50 K to 500 K (−223 °C to 227 °C). It has been found that some features, like the diffuse scattering from the B-site ordering, remain unchanged with change of temperature in terms of both intensity and peak shape. However, other diffuse scattering features evolve with T, for example the size effect scattering around the Bragg peaks. The size-effect becomes less pronounced with increasing temperature, with the diffuse scattering becoming more symmetric around the Bragg peaks. The diffuse rods caused by the planar domains change only slightly with temperature. This finding indicates that the planar domains persist into the paraelectric state but that the correlation between lead displacement and the average separation of adjacent lead atoms becomes weaker, suggesting that this size effect may be crucial to the ferroelectric properties.