Degradation kinetics and service performance prediction of CoSb3-based skutterudite thermoelectric device

Abstract

Predictable service performance is essentially required for practical applications of thermoelectric (TE) power generators. Sublimation at TE material surface and chemical reaction/diffusion at electrode interface are the major causes for the performance degradation of TE devices. The synergistic effect of surface and interface behaviors coupled with temperature gradient makes the degradation relationship much more complicated, and the accurate prediction of service performance very challenging. In this work, we systematically investigated the sublimation kinetics for p-type Ce0.9Fe3CoSb12 and n-type Yb0.3Co4Sb12 skutterudites. A service performance prediction model (SPPM) is proposed to illustrate the service performance profiles of TE device, in which an equivalent circuit approach is applied to quantitatively link the kinetic parameters of structure and composition evolutions at both surface and interface to the output performance of device. It is found that, the performance degradation is mainly caused by the interfacial structure evolution at early stage, while the influence of surface sublimation becomes dominant in long-term service. The SPPM simulation results are well verified by the long-term evaluation tests of single-leg devices under temperature gradients, demonstrating its potential application to the engineering design of TE power generators.