Anisotropic thermal conductivity in lattice transition thermal rectifiers

Abstract

Lattice transition materials can exist in two phases with different thermal conductivities. Because of this, phase change materials (PCMs) are considered as promising next-generation thermal rectifying materials. The performance of a thermal rectifier known as rectification factor (R) is evaluated by the ratio between the heat that preferentially flows in the forward direction and that in the reverse one. In this work, taking into consideration that PCMs have the striking characteristic of high anisotropy, we propose an analytical framework based on the thermal conductivity tensor theory for predicting the R of lattice transition thermal rectifiers. Because of lattice symmetries, model unveils that the rectification factor is ruled, as well as limited by the ratio of the principal thermal conductivity tensor components present in each phase and the thermal conductivity of the invariant phase material. Furthermore, to validate our predictions the model is applied to the existing experimental systems in the literature, providing accurately truthfulness on observed R. Hence, the analytical model is promising from both theoretical and experimental points of view to understand the effects which allow developing a procedure for engineering an enhanced performance thermal rectifying device.