Anion Distributions and Phase Transitions in CuS1-xSex(x = 0-1) Studied by Raman Spectroscopy

Anion distributions and phase transitions in CuS1-xSex (x = 0-1), which are isostructural with CuS (covellite), have been studied through the Raman spectroscopic measurements. In hexagonal CuS type structure, there exist two different anion sites (2c and 4e sites of the hexagonal space group P63/mmc), and it has been shown that the selenium atoms occupy the 4e sites preferentially in these solid solutions. The temperature dependences of the frequencies of the Raman peaks have also been measured for the seven samples of CuS1-xSex in the temperature range from 300 to 80 K. For each sample except for CuSe, the lowest frequency Raman peak has shown the soft mode behavior, which is considered to be related to the structural phase transition. These results have been discussed referring to those obtained by the X-ray diffraction method. In these solid solutions, the phase transition temperatures rise with increasing selenium contents.