Raman scattering, central peak and phase transitions in AgNbO3

Light-scattering investigations in the temperature range from 10 to 850K have been performed on single crystals of silver niobate AgNbO3. The results are compared with structural and dielectric measurements revealing a complex sequence of phases. The Raman results and especially the strong central peak, which occurs over a wide range of frequencies and temperatures, are analysed in connection with the various phase transformations. The specific contributions of the niobium and the silver ions are tentatively discussed.