Heat capacity of hafnia at low temperature

Research highlights: → PPMS was successfully used to measure the low temperature Cp of hafnia. → Thermodynamic functions at temperature from (2 to 300) K were derived. → Comparisons between the present work and literature, hafnia and zirconia, were made. - Abstract: The low temperature (2 to 300) K heat capacity of monoclinic hafnia (HfO2) was measured using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). The thermodynamic functions in this temperature range were derived by curve fitting. The standard entropy and enthalpy of hafnia at T = 298.15 K was calculated to be 56.15 ± 0.57 J · mol-1 . K-1 and 9.34 ± 0.09 kJ · mol-1, respectively. The results are in fairly good agreement with old data, which only covered temperatures from (50 to 298) K. Hafnia has a higher heat capacity than zirconia at all temperatures from (2 to 300) K.