Degradation analysis and modelling of bismuth-antimony-tellurium(selenium) semiconductor thermoelectric power modules.

摘要

Close-packed array (CPA) thermoelectric module technology has been recently developed for use in terrestrial and space thermoelectric power generators. In order to achieve high efficiencies in converting thermal energy into electricity, compound semiconductors have been extensively used for thermoelectric modules. Since most thermoelectric devices operate in hostile environments for remote and unattended applications, highly reliable thermoelectric modules are required. Accordingly, reliability issues that arise from thermally induced degradation have attracted much attention from researchers for several decades.; To study the performance degradation and reliability problems encountered in semiconductor thermoelectric modules, two different module types are characterized and modeled using both experimental and analytical approaches. The objective of this research is to investigate the thermally induced degradation of (Bi,Sb){dollar}sb2{dollar}(Te,Se){dollar}sb3{dollar} semiconductor thermoelectric modules caused by chemical inhomogeneity (segregation, precipitation, coarsening and impurity diffusion) and microstructure change (microcracking, oxidation and the formation of dark band), as well as to understand the mechanism of the formation of dark band caused by diffusion of impurities from insulator into semiconductor. In the experimental investigation, surface characterization of thermoelectric modules and materials has been systematically conducted using both scanning electron microscopy and energy dispersive x-ray spectroscopy. In mathematical models, exactly analytical solutions to partial differential equations based on the dynamic thermal stress assisted diffusion cracking model and a new modified Whipple's diffusion model for high diffusivity paths have been obtained to elucidate the mechanism of the observed dark bands. This modified Whipple's diffusion model considers the effect of the thermomigration driving force perpendicular to a microcrack as the high diffusivity path on impurity diffusion. The diffusion model established in this study is also applicable to semiconductor solid state electronic devices for understanding the effect of the thermomigration and electromigration driving forces on grain boundary diffusion, which usually results in the most prevalent failure mechanisms in microelectronic devices and circuits.