EFFECT OF PHONON-SCATTERING BY ISOTOPE IMPURITIES ON THE THERMAL-CONDUCTIVITY OF DIELECTRIC SOLIDS

By an iteration method which has recently been applied to perfect rare gas crystals, the phonon Boltzmann equation is solved for a dielectri c isotropic solid subjected to a thermal gradient and containing isoto pe scattering centres. The solution avoids the use of the relaxation t ime approximation for three phonon collisions, and consequently provid es a rigorous description of the interference effects between these co llisions and Rayleigh scattering due to point impurities. Good agreeme nt is found between theory and experiment for solid krypton, germanium and silicon.