Calorimetric and structural studies of langbeinite-type Tl2Cd2(SO4)3

Abstract

Abstract Heat capacity measurements have been made from 6 to 344 K on well-characterized single crystals of dithallium dicadmium sulfate Tl2Cd2(SO4)3 (abbreviated as TlCdS) with an adiabatic calorimeter. Three very sharp peaks were observed in the heat capacity curve indicative of phase transitions. The transition temperatures were found to be 96.0, 123.0, and 129.9 K, respectively. Enthalpies and entropies of phase transition are reported. The phase transition at 96.0 K shows apparent thermal hysteresis (2.0 K), while the other two transitions do not. Smoothed values of the heat capacity, entropy, enthalpy increment, and Gibbs free energy function are presented from 10 to 340 K. The detailed crystal structure of TlCdS was determined by x-ray diffraction at room temperature. The experimental results are discussed and compared to those reported in the literature.