Thermal Properties of Synthetic Fluorapatite Crystals

Abstract

Measurements of the heat capacity, thermal expansion, and thermal conductivity on synthetic crystals of undoped and neodymium-doped fluorapatite are reported. Fitting the low-temperature specific heat data to a Debye model yields a Debye temperature of 550°K. At 25°C the thermal expansion coefficients are 10.0×10−6 °K−1 and 9.4×10−6 °K−1, respectively, along the [0001] and [101̄0] directions. The thermal-expansion measurements yield a Debye temperature of 500°K. A typical value of the thermal conductivity is 0.020 W cm−1 °K−1 at room temperature. The thermal conductivity is only feebly temperature dependent and, similar to the thermal-expansion coefficient, shows very little crystallographic anisotropy.