The vibration spectrum and structural phase transitions in cesium-bismuth molybdate

The vibration IR spectra of a crystal CsBi(MoO4)2 are studied under polarized radiation (E < b, E < c) in the te mperature region of 16 to 300 K and frequency range of 60 to 1000 cm-1. It is found that the structural phase transitions (Tc1=135 K, Tc2=330 K) affect the IR reflection spectra of the crystal. The symmetry of low-temperature phases is obtained by comparing the vibration spectra of CsBi (MoO4)2 with those of crystals CsDy (MoO4)2 and KDy (MoO4)2. Below Tc1 and Tc2 the low-temperature phase symmetries are found to be D2h8 and Ci1