Determination of Thermal Conductivity and Estimation of Specific Heat for High-Temperature Oxides

A new method is proposed for the simultaneous determination of thermal conductivity, thermal diffusivity and specific heat for high-temperature materials by use of a hot strip.The principle of this method is based on the two solutions of the Fourier’s partial differential equation solved under the different conditions of time. The temperature increase with time is proportional to logarithm of time for a long-time measurement. The slope of this straight line gives thermal conductivity (λ). On the other hand, the response-curve by a short time measurement is proportional to square root of time. The slope of this straight line offers thermal diffusivity (κ). The specific heat (Cp) can be estimated by virtue of ρCp=λ⁄κ (ρ: density).By using this method, thermal conductivity, thermal diffusivity and specific heat of 30(mol%)Na2O–70SiO2 sample have been determined over the wide temperature range of 300 to 1500 K in liquid and glassy states. The thermal conductivity is in good agreement with that obtained by the hot wire method. The thermal diffusivity is nearly constant at low temperatures but decreases with increasing temperature. The specific heat increases with increasing temperature but the absolute values are 1.1–1.2 times higher than those by the laser-flash method.The hot-strip method can be used for a simultaneous determination of thermal conductivity, thermal diffusivity and specific heat for materials at high temperatures.