Exceptionally Heavy Doping Boosts the Performance of Iron Silicide for Refractory Thermoelectrics

Thermoelectric (TE) power generation is expected to be one of the most effective solutions to convert industrial exhaust heat to electricity for conserving fossil energy and reducing carbon emissions. However, its real application is obstructed decisively by the weakness of the service stability of state-of-the-art TE materials at high temperatures in air. Refractory iron silicide (beta-FeSi2) used to be widely investigated as TE materials, but the low zT has restricted its practical application and even made it almost vanish from TE research in recent years. Here, guided by theoretical calculation, ultrahigh solubility of Ir on the Fe sites of beta-FeSi2 is successfully realized. Doping 16% Ir elicits multi-valley electrical conduction and phonon-electron scattering, doubling the previous zT record of beta-FeSi2 to approximate to 0.6 at 1000 K. The TE properties of the obtained beta-FeSi2 are practically unchanged after thermal aging in air at 1173 K. The new conceptual electrode-less beta-FeSi2-based refractory module demonstrates considerable power density and stable power generation when it is burned by a gas flame in air. These results mark a step toward developing practical TE power generation technology for the recovery of industrial waste heat.

Automated summary

Thermoelectric power generation is an effective solution for converting industrial exhaust heat into electricity. However, current TE materials have poor stability at high temperatures. This study successfully improved the stability and performance of refractory iron silicide by introducing high solubility of iridium. The new beta-FeSi2-based module demonstrated stable power generation with considerable power density when burned by a gas flame.