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.