Thermoelectric Materials from Powder Metallurgy

Abstract

A wide variety of materials useful for thermoelectric power generation and refrigeration, including lead telluride (n- and p-types), germanium bismuth telluride (p-type), and zinc antimonide (p-type) were prepared from powders by cold-pressing and sintering techniques. Thermoelectric properties of these materials were found to be superior in most cases to what was achieved by other methods of preparation. The alloys were prepared from high-purity raw materials by atmosphere melting and casting. Cast ingots were crushed to powder and subsequently consolidated to pellets of desired shape and size by cold-pressing and sintering. The following determinations were made: effects of composition, particle size, and method of grinding; prepressing treatments; compacting pressure; die lubrication techniques; sintering temperatures; times and atmospheres on Seebeck coefficient vs. temperature, electrical resistivity vs. temperature, thermal conductivity vs. temperature; density, structure, and mechanical properties. Measurement techniques are described for many of the above property determinations. A method of capping lead telluride pellets with iron powder during the pressing operation is described which solved a major problem of joining the pellets to conductor materials.