Thermal conduction of Sn₂P₂S₆ferroelectric monocrystal and its isostructural analogs

Abstract Temperature dependences of thermal conduction have been studied for Sn2P2S6 and Pb2P2Se6 crystals. For Sn2P2S6 a presence of a maximum in λ(T) has been found at 11K which is explained by the restriction of free path length (ι) by phonon scattering on defects. λ variation as T−n (n≈1) within 15200K results from the lack of the temperature dependence of ι due to the commensurability of its value to the unit cell size. The form of the anomaly in λ(T) at the phase transition is defined by the ratio of temperature dependences of specific heat and mean sound velocity.