Structural characteristics of the pseudo-perovskite relaxor ferroelectric Pb(Sc_(0.5), Ta_(0.5))O_3

摘要

Studies carried out using high resolution powder diffractometery (HRPD) on highly ordered Pb(Sc_(0.5)Ta_(0.5)O_3, indicate that the paraelectric phase is Fm3m and the ferroelectric state is R3m. The calculated atomic displacements show that on passing into the ferroelectric state, the polarization arises mainly from distortions in the lead cations. There are some subtleties in this system observed in the TEM, where extremely weak facecentred forbidden reflections are observed. In the neutron data, there are also extremely weak features that are consistent with these primitive reflections. Structure refinement indicates that there is a major movement of the Pb-cations along the polar axis.