Thermal diffusivity data on nonmetallic crystalline solids from laser-flash analysis

This chapter presents an extensive database on thermal diffusivity (Dheat) vs temperature (T) of ~200 different and diverse crystalline solids, obtained using laser-flash analysis, which are verifiably free of unwanted ballistic radiative gains and contact losses. The universal formula, Dheat(T)=FT-G+HT, where F, G, and H are positive fitting parameters, describes all materials. Parameters depend mainly on structure, and secondarily on the chemical composition. Thermal diffusivity depends on thickness for nonmetals, which implicates diffusion of radiation and emphasizes the problematic nature of high pressure studies. Thermal diffusivity and optical thickness depend on length in the same way, showing that heat is diffused by infrared photons. Thermal diffusivity is reduced linearly with porosity for ceramics and monomineralic rocks. Also, the temperature dependence for grainy mixtures is the same as that of crystals. Hence, grain boundary resistance does not contribute. However, storativity of the constituents is important, due to energy conservation.