STUDIES OF TRANSITIONS IN ORDERED AND DISORDERED PEROVSKITES - X-RAY AND MOSSBAUER SCATTERING EXPERIMENTS

Scattering experiments using Mossbauer gamma rays and x-rays have been performed on ordered and disordered Pb(Sc0.5Nb0.5)O3 (PSN), and Pb(Fe0.5Nb0.5)O3 (PFN) which exists only in a disordered state. All three materials are ferroelectric at room temperature and undergo a change to a paraelectric form close to 100-degrees-C. No evidence of an increase in inelastic scattering was found as the transition was approached in any of the materials studied. Rather large differences were found in the magnitude of Debye-Waller factors calculated from integrated intensities obtained using x-rays and Mossbauer gamma rays. These differences arise because part of the atomic displacement from positions of high symmetry is dynamic.