Meta-study: Analysis of thermoelectric figure of merit parameters for silicides with various doping agents

Abstract

Thermoelectric (TE) materials are increasingly promising for power generation in medium to high-temperature environments. Recent research on thermoelectric generators (TEGs) has determined the thermodynamic properties which impact the total efficiency and figure of merit (ZT) of these materials. A large Seebeck coefficient, high electrical conductivity and low thermal conductivity optimise ZT. This meta-study investigates silicides for potential TEG applications due to their high chemical stability and higher natural abundance than other TE materials. Data on the thermoelectric properties of CrSi2, FeSi2, Mg2Si and MnSi2, with a range of dopants, was sourced from a wide scope of literature and is analysed. The above thermodynamic properties contributing to ZT for each of these materials are graphed between 300 and 1000 K. It was found that chromium silicides are most effective at a temperature range of 600-800 K, and undoped magnesium silicides are most effective around 900 K. Oxide addition to β-FeSi2 produced relatively high ZT scores (ZT ≈ 0.5) among iron silicides. Rhenium substitution in manganese silicides produced a maximum figure of merit (1.05) at 900 K. Supersaturation via liquid quenching was determined to maintain high rhenium substitution and this technique may be the key to further improving the thermoelectric properties of other silicides.