The synthesis of CaZn/sub 2/Sb/sub 2/ and its thermoelectric properties

CaZn/sub 2/Sb/sub 2/ was prepared and examined for use as a high temperature thermoelectric material. It has a high Seebeck coefficient and high electrical conductivity-comparable to /spl beta/-Zn/sub 4/Sb/sub 3/. These two properties are vital in determining the ability of the compound to change heat into electricity isentropically. The dimensionless figure of merit, ZT, a measure of the thermoelectric material's efficiency is defined as ZT = S/sup 2//spl sigma/T//spl lambda/ where S is the Seebeck coefficient, Z the figure of merit, T the temperature, /spl sigma/ the electrical conductivity, and /spl lambda/ the thermal conductivity. However, due to its simple structure, CaZn/sub 2/Sb/sub 2/ has high /spl lambda/. Doping CaZn/sub 2/Sb/sub 2/ with Ga/sup 3+/ or modifying the (Ca, Zn) to Sb ratio was also investigated. Samples were prepared from Zn, Sb, and the binary compound CaSb/sub 2/. They were tested for material composition, structure, and thermoelectric properties. Results of this experiment are presented and discussed as are the applicability of these materials to future thermoelectric use. Conservative estimates show a ZT of .5 at 500/spl deg/C; CaZn/sub 2/Sb/sub 2/ could be a good thermoelectric to use at temperatures above 400/spl deg/C.