Powder metallurgy for thermoelectrics

Abstract

Thermoelectric materials, which directly convert thermal energy into electricity, have become quite popular recently due to the development and world spreading of alternative power energy sources. Nowadays powder metallurgy methods are widely used for production of almost all types of thermoelectric (TE) materials, from low-temperature bismuth-telluride-based materials to high-temperature (operating above 1000 K) Cu 2− x Se alloys. Historically, crystallization methods were widely used in production [1] , for example, Czochralski method, Bridgman method and zone melting method are the most common. However, in case of crystallized materials, we face one disadvantage that is weak mechanical properties. In TE devices working bodies in the devices are bulk TE materials with dimensions about millimeters, so they can be exposed to different shifts or tensile stresses. Therefore, powder metallurgy methods were used to improve mechanical strength, in particular, various sintering methods. Later, it was found that sintering from powders allows to reduce one significant parameter for thermoelectrics – thermal conductivity, and in the 2000s the propagation of powder technologies started over.