Determination of thermal conductivity tensor and heat capacity of insulating solids

Abstract

Specific heat capacity rho c_p and thermal conductivity components lambda _ii for several classes of anisotropic crystals as well as isotropic materials may be determined by a transient method. The specimen is ground flat, the boundary plane being oriented parallel to two principal axes of the conductivity tensor. Two parallel metal strips in one of the principal directions are evaporated on to this surface. One is heated with a constant DC power, the other is used as an AC-driven resistance thermometer. It is shown that the temperature variation measured in response to a heat pulse permits lambda and rho c_p to be determined if the specimen is isotropic. If it is anisotropic, two parameters of the type lambda ₁₁ lambda ₃₃ and lambda ₁₁/ rho c are obtained. Additional measurements with the strips deposited in the other principal directions enable lambda ₁₁, lambda ₂₂, lambda ₃₃ and rho c_p to be calculated.