CATION ARRANGEMENT IN THE COMPLEX PEROVSKITES AND VIBRATIONAL-SPECTRA

Vibrational spectrum analysis was used to study the cation arrangement in the complex perovskites. The transition from the ideal perovskite structure ABO(3) to complex compositions with a pair of the A or B cat ions, such as A(1/2)'A(1/2)'' BO3 or AB(1/2)'B-1/2'' O-3, leads to dra stic changes in the Raman spectra. Correlation between a change in the Raman spectra and the recent structure analysis by advanced direct me thods is discussed for some important 'model' compounds, such as relax er ferroelectrics PbSc1/2Ta1/2O3 (PST), PbMg1/3Nb2/3O3 (PMN) and Na1/2 Bi1/2TiO3 (NBT) and the low-dielectric material BaMg1/3Ta2/3O3 (BMT). (C) 1998 John Wiley & Sons Ltd.