Preparation and structure characteristics of orthorhombic and chal copyrite LiGaSe₂

LiGaSe₂ polycrystalline materials were synthesized using a one-temperature horizontal tube furnace. Their structures were characterized by the X-ray powder diffraction (XRD) and Raman spectra. The XRD results reveal that the two kinds of LiGaSe₂ polycrystalline materials with orthorhombic and chalcopyrite structures are single phase and have good crystallization. It is proved that the final soaking temperature and decreasing-temperature rate determine the phase transformation of LiGaSe₂. Two sphalerite-like vibration peaks were identified for Raman spectra. The low-frequency mode peaks are mainly related to Ga-Se vibrations, whereas the high-frequency mode peaks are mainly derived from Li-Se vibrations. The slight shift of peak positions in two structures is caused by the differences of force constants of Li-Se and Ga-Se bonds in the different structures.