Low-temperature X-ray studies of TlInS2, TlGaS2, and TlGaSe2 single crystals

Abstract

The results of X-ray diffraction studies of the unit-cell parameters and thermal-expansion coefficients of TlInS2, TlGaS2, and TlGaSe2 crystals in the temperature range 100–300 K are described. It is shown that the unit-cell parameters of all the studied crystals gradually increase with increasing temperature. The temperature dependences of these parameters exhibit anomalies in the form of bends and kinks at temperatures corresponding to phase transitions in the crystals. The thermal-expansion coefficients along the [001] crystallographic direction of the crystals under study are determined. It is found that their values slightly change with increasing temperature.