THE RAMAN MODES OF THE AURIVILLIUS PHASES - TEMPERATURE AND POLARIZATION DEPENDENCE

Aurivillius phases of order n = 1-4, consisting of perovskite-like (A(n-1)B(n)O(3n+1))(2-) blocks regularly interleaved with (Bi2O(2))2+ sheets, have been studied by laser Raman microprobe. The trends in the Raman spectra have been correlated with the chemical and structural relationships between these phases, and have also been compared with results from other layered oxides containing perovskite-like units. Isomorphism of the Bi-2(Mo, W)O-6 n = 1 members has been confirmed. The phase and Curie transitions have been identified from the evolution of temperature-dependent spectra. Some of these transitions correlate well with Previously reported results; others are reported for the first time. Single crystals of two members (n = 1 and 3) of the series were used to assign the Raman modes from the polarization dependence; the major features were interpreted in the context of the distortions and displacements, some of which are thought to account for the ferroelectric properties of these phases. (C) 1995 Academic Press, Inc.