Low-Temperature Thermal Properties of Calcium Tungstate

The heat capacity of a single crystal of CaWO4 was determined by adiabatic calorimetry from 5° to 350°K and found to be without transitions or thermal anomalies. Deviation of the curve from normal sigmate shape is shown to be due to internal vibrations of the WO4= ions. Apparent Debye θ's for the lattice-only heat capacity and for that of the acoustical spectrum show “normal” deviation from simple Debye theory. Values of the heat capacity (Cp), entropy (S°), enthalpy function [(H°–H0°) / T], and Gibbs function [(G° / H0°) / T] at 298.15°K are 27.28, 30.21, 16.02, and −14.19, in calories per gram formula mass·degree Kelvin.