Thermoelectric properties of CoSb3 prepared by copper mold quenching technique

Abstract

A novel technique to prepare CoSb/sub 3/ materials on a mass production level was studied. Co and Sb were melted together in an alumina crucible at 1373 K, and cast in a copper mold to solidify the melts. The obtained alloyed ingots consist of mainly three phases of CoSb/sub 3/, CoSb/sub 2/ and Sb. To react Sb with CoSb/sub 2/ and get a CoSb/sub 3/ single phase, the ingots were annealed at 823-1073 K. During the heat treatment, Sb and CoSb/sub 2/ phases changed to CoSb/sub 3/ phases and voids. The obtained CoSb/sub 3/ samples show n-type thermoelectric properties. Some factors affecting the properties, for example, Sb/Co atomic ratio, impurity content and density are discussed, based on the experimental data by X-ray diffractometry, optical microscopy, EPMA, chemical analysis and so on. On the other hand, an ingot was ground, mechanically alloyed and hot-pressed. The hot-pressed samples show p-type thermoelectric properties. Moreover, mechanical alloying is effective to reduce the thermal conductivity by refining the crystal grain size of CoSb/sub 3/. As a result, ZT value, 0.10 was obtained at a temperature of 669 K.