Heat capacity and thermal expansion of neodymium hafnate ceramics

Abstract The heat capacity of Nd 2 Hf 2 O 7 ceramics with a pyrochlore structure ( Fd3m) has been measured using the methods of adiabatic (18.9–347.6 K) and differential scanning calorimetries (317–1347 K). The molar heat capacity of neodymium hafnate has been extrapolated to 0 K without taking into account the contribution of antiferromagnetic transition occurring below 10 K, and standard thermodynamic functions (entropy, change in enthalpy and reduced Gibbs energy) have been calculated using smoothed molar heat capacity values. The general form of the molar heat capacity anomaly associated with the non-cooperative Stark effect (Schottky anomaly) has been determined. The has been studied by high-temperature X-ray powder diffraction in the temperature range 303–1273 K. The studies have been performed on samples characterized by chemical, phase and electron microscopic analyses.