Heat Capacity and Thermodynamic Functions of Dysprosium Orthoniobate in the Range 2–1300 K

The heat capacity of polycrystalline dysprosium orthoniobate was studied over a wide temperature range by three calorimetric methods: relaxation calorimetry (2–50 K), adiabatic calorimetry (9–350 K), and differential scanning calorimetry (308–1300 K). Below 9 K a descending low-temperature anomaly branch was detected, whose peak is beyond the measurement limits. At 1086 K a reversible phase transition occurs. The behavior of heat capacity and in the phase-transition region implies that this is a second-order phase transition. The data gained were used to calculate temperature-dependent standard thermodynamic functions of DyNbO 4 over the whole measurement range.