ZrTe5 and HfTe5: The heat capacity and derived thermophysical properties from 6 to 350 K

Abstract

The heat capacities of ZrTe5 and HfTe5 have been measured by adiabatic shield calorimetry from 6 to 350 K on samples carefully shielded to minimize the contact between the sample and oxygen during all stages of preparation and measurements. Since ZrTe5 and HfTe5 are isostructural and their molecular volumes are almost identical, the small differences between their heat capacities are due essentially solely to mass effects. There is absolutely no indication of any excess contribution to the heat capacities of these compounds below 350 K. The effective thermodynamic dimension of ZrTe5 and HfTe5 is estimated to be between one and two. The molar heat capacity, entropy, and enthalpy at 298.15 K are 18.32R, 31.96R, and 4155.7R [middle dot] K for ZrTe5, and 18.77R, 32.99R, and 4276.8R [middle dot] K for HfTe5.