Low-temperature heat capacity and thermodynamic functions of dysprosium selenide Dy₂Se₃

A sample of dysprosium selenide (Dy2Se3) was synthesized and characterized by various physicochemical methods. The heat capacity of Dy2Se3 has been measured in the temperature range from T = 4.85 K to T = 301.11 K using adiabatic calorimetry. Two pronounced lambda-anomalies with maxima at temperatures T-C1 = 6.20 K and T-C2 = 219.40 K were found in the functional behavior of the heat capacity. In addition, the heat capacity of Dy2Se3(cr) showed a continuing excess value consistent with a Schottky anomaly on energy levels lying roughly from 0 to 425 cm(-1) above the ground state. On the basis of experimental data on the heat capacity, the values of entropy, enthalpy and reduced Gibbs energy were calculated in the interval from T = 0 to T = 301 K, and the anomalous contribution to these properties was determined. The value of the absolute entropy obtained was used for calculation of Dy2Se3(cr) entropy formation at T = 298.15 K.