Fabrication of Thermoelectric Nanocomposites with High Conversion Efficiency Utilizing a Nonequilibrium Milling Process

Abstract

Nanostructuring thermoelectric materials has been attempted to enhance thermoelectric figure of merit, zT. Nanostructuring is expected to lead to the reduction of lattice thermal conductivity or the extension of solubility of dopants, either of which could lead to improvement of zT. A nonequilibrium ball milling process has been employed to fabricate forced solid solutions of silicon with supersaturated antimony or boron, or magnesium silicide with supersaturated bismuth. The power obtained in the ball milling process was consolidated by the spark plasma sintering technique, which resulted in nanoprecipitation. In the silicon-antimony system, the carrier concentration is found to be higher than the equilibrium solubility. In the magnesium silicide-bismuth system, we observed the reduction of lattice thermal conductivity from the nanostructuring.