Thermoelectric properties of Zn 4Sb 3 thin films prepared by magnetron sputtering

Abstract

Microstructure and thermoelectric properties were investigated on Zn 4Sb 3 thin films prepared by co-deposition of Zn and Sb by magnetron sputtering. The as-deposited amorphous thin films were annealed at temperatures between 573 and 673 K so that they crystallized in the form of β-Zn 4Sb 3. The Zn 4Sb 3 thin films have a relatively high power factor and a low thermal conductivity. Microstructure of the thin films can be controlled by changing sputtering power and deposition time. The thin films investigated are all Zn-rich with respect to the stoichiometric Zn 4Sb 3. Their electrical resistivity decreases as film thickness increases and Zn-rich particles in the matrix grow coarse. Their Seebeck coefficient decreases as electrical resistivity decreases. Low electrical resistivity and high Seebeck coefficient can be achieved simultaneously in a film specimen with properly controlled thickness and microstructure. A nano-scale grain size in a ∼300 nm-thick film specimen gives rise to an almost 50% reduction in its thermal conductivity. A ZT of 1.2 at ∼460 K has been obtained for a 349 nm-thick Zn 4Sb 3 film specimen.