Thermophysical properties of hafnium titanate

Heat capacity and lattice thermal expansion of hafnium titanate (HfTiO4) have been studied by differential scanning calorimeter (DSC) and high temperature X-ray diffraction technique (HT-XRD) in the temperature range 298–800 K and 298–1973 K respectively. From the heat capacity data, other thermodynamic functions such as enthalpy, entropy and Gibbs energy functions were computed. Percentage linear thermal expansion and mean linear thermal expansion coefficients were computed from the lattice parameter data. The thermal expansion of HfTiO4 was found to be anisotropic. The lattice parameters at 298 K viz., a, b and c axes are 0.5042, 0.5579 and 0.4732 nm respectively. The expansivity along the ‘a’ axis was found to be larger than the expansivity along ‘b’ and ‘c’ axes. The lattice was found to contract along b-axis below 1073 K. The heat capacity of HfTiO4 at 298 K was found to be121.4 J K−1 mol−1. The percentage linear thermal expansion in the temperature range 298–1973 K along a, b and c axes are 2.74, 0.91 and 1.817 respectively.