Compressive Fatigue Behavior and Its Influence on the Thermoelectric Properties of p-Type Bi0.5Sb1.5Te3 Alloys.

Abstract

BiSbTe alloy is one of the most important thermoelectric materials that has been commercialized for large-scale applications in waste heat recovery and spot cooling. However, its practical application often involves complicated service conditions, such as substantial dynamic vibrational stresses as well as long-term exposure to the large thermal gradient that usually generates high thermal stress. Thus, it is of vital importance to investigate the mechanical response and the evolution of microstructure and thermoelectric performance of BiSbTe alloy under the quasi-static force and dynamic compressive stress. Herein, we elucidate the compressive fatigue behavior and its influence on the thermoelectric performance of p-type Bi0.5Sb1.5Te3 materials prepared by melt spinning and subsequent plasma-activated sintering. The fatigue life was tested at various stress ratios ranging from 60 to 90%. The microstructure evaluation indicates that repetitive loading of compressive stress contributes to largely accumulated strains and dislocations near grain boundaries. With the increasing cycling numbers, the magnitude of accumulated strains reaches the critical level and leads to microcrack initiation and propagation of fatigue cracks. The cyclic compressive stress resulted in the marked degradation of thermoelectric performance in Bi0.5Sb1.5Te3 material due to the strong suppression of carrier mobility by the fatigue-induced defects. This work can provide important guidance for the practical applications of p-type Bi0.5Sb1.5Te3 material.