Thermophysical properties of hafnium titanate

Abstract

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 298–800K and 298–1973K 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 298K viz., a, b and c axes are 0.5042, 0.5579 and 0.4732nm 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 1073K. The heat capacity of HfTiO4 at 298K was found to be121.4JK−1mol−1. The percentage linear thermal expansion in the temperature range 298–1973K along a, b and c axes are 2.74, 0.91 and 1.817 respectively.