Abstract:

Based on direct reversible conversion between heat and electricity, thermoelectric (TE) energy-conversion technology can give an attractive solution for increasingly serious environmental impact of global climate change due to the massive combustion of fossil fuels. TE energy-conversion technology possesses several unique advantages over conventional compressor-based energy-conversion technology, including compactness, no greenhouse gas emission, no noise pollution, long-time reliability in demanding environment. However, TE energy-conversion efficiency, governed by a dimensionless figure of merit zT = S2σT/(κc+κL), in which S, σ, T, κc and κL are the Seebeck coefficient, the electrical conductivity, the absolute temperature, the carrier and lattice thermal conductivity, respectively, is low, limiting the practical applications. Because transport parameters S, σ and κc are highly interrelated, it is difficult to improve TE performance if only optimizing one of them. Hence, suppressing the only relatively independent parameter κL is a straightforward strategy to boost TE performance. The concept of phonon-liquid electron-crystal (PLEC) was proposed to search for TE materials with intrinsically low κL induced by liquid-like ions randomly hopping in the crystal structure at elevated temperatures. In recent years, argyrodite-type compounds have attracted much attention because of their remarkable PLEC effect. This seminar will give a summary of the progress made in developing argyrodite-type TE materials, and identify scientific issues which need further investigation.