Anisotropic Thermal Diffusivity and Conductivity of La-Doped Strontium Niobate Sr_2NB_2O_7

摘要

The thermal diffusivity of the La-doped layered perovskite Sr_2NB_2O_7 parallel and perpendicular to the perovskite layers is reported from room temperature up to 1000℃. The anisot-ropy persists through an incommensurate-normal ferroelectric phase transformation at 215℃ and up to 1000℃, the maximum temperature of our measurements. The thermal conductivity perpendicular to the perovskite layers, derived from the diffusivity in the same direction, calculated using the density and measured heat capacity, has a constant value of 1.05 + 0.05 W/mK up to 1000℃. Possible explanations for the low thermal conductivity and anisotropy are described.