Performance Enhancement of thermoelectric MgAgSb based composite from ferroelectric order

Principal investigator: Haixue YAN
Funding source(s): Royal Society
 Start: 01-03-2018  /  End: 30-03-2021
 Amount: £12,000
Spark plasma sintered nano structures

There is an increasing demand for alternative energy technologies to significantly reduce CO2 emissions, energy cost, and our reliance on fossil fuels. One approach is to use thermoelectric (TE) materials to save waste heat energy and to convert it into useful electrical energy. Thermoelectric materials have the additional potential advantages that they could be: small, inexpensive, lightweight, quiet and pollution-free. These applications call for thermoelectric materials with high zT which requires higher Seebeck coefficient, higher electrical conductivity, and lower thermal conductivity. There are three strategies to improve ZT values: (1) Band engineering with element doping; (2) introduction of nanostructure to reduce lattice thermal conductivity; and (3) using new mechanisms for phonon scattering. MgAgSb has the Half-Heusler structure, is a kind of potential green thermoelectric material with high ZT value ~1 between room temperature and 300C. Herein, we proposed a new strategy to obtain much higher performance via fabricating ferroelectric/thermoelectric composite. In this composite, ferroelectric particles can tailor the carrier concentration and mobility of thermoelectric MgAgSb matrix. The coupling between ferroelectric ordering and carriers behaviors can improve the power factors. Meanwhile, the local carriers cloud near the ferroelectric particles may scatter much phonons, which would reduce thermal conductivity. With more tailoring the microstructure of composites, higher ZT value above 1.6 can be obtained likely.