ABSTRACT
The arguments regarding thermal conductivity and resistivity extend over to electrical conductivity and resistivity in an analogous manner. In a crystal the conductivity may take different magnitudes if measured in different directions, it may vary as a function of crystallographic direction. The conductivity ellipsoid is tilted in such a way that the thermal conductivity maximises at an angle measured in an anticlockwise direction from –grad T. Hence the conductivity equation is applicable and the set-up is that to measure thermal conductivity in an anisotropic crystal. Growth of single crystals is often in preferred directions, which can make cutting to specific shapes more difficult. If samples of arbitrary orientation are used, the conductivity components can be obtained from resistivity components only when sufficient measurements have been made to determine each principal component of resistivity. Measurement of the diffusion coefficients for atoms in crystals can give important information regarding crystalline structure.
