A Raman study of silver tantalate (AgTaO3) and its structural phase transition sequence

Light scattering measurements in the temperature range from 10 to 775 K have been performed on single crystals of silver tantalate (AgTaO3). The results are compared with dielectric and X-ray investigations. The intensity distribution of the scattered light is analysed and discussed in terms of the sequence of structural phase transitions. The Raman spectrum displays important changes at 170 K on heating and at 120 K on cooling. This feature is the first clear evidence of an additional structural phase transition that is not evident from X-ray and dielectric measurements.