Thermal conduction of Sn(Pb)(2)P2S(Se)(6)-like compounds

Temperature dependences of thermal conduction coefficient lambda for the monocrystalline compounds of the Sn(Pb)(2)P2S(Se)(6) system, their solid solutions and glass have been studied. A maximum in thermal conduction of Sn2P2S6 has been found at T = 11 K. Within the 12 K less than or equal to T less than or equal to U-D interval (U-D is a Debye temperature) lambda varies in accordance with Eiken's law (lambda similar to 1/T), while its absolute value is proportional to the dissociation energy of the crystal and inversely proportional to the total mass of the atoms in the unit cell. Low lambda value and its weak dependence on the temperature at T > 2U(D) is probably due to that the free phonon path is proportional to the unit cell size.