Enhanced thermoelectric properties in MgAgSb composite with Ag 3 Sb fabricated by the microwave-assisted process and subsequent spark plasma sintering

Abstract

MgAgSb material has been attracting more attention for its non-toxicity and elemental abundance of raw materials. We herein utilise the microwave-assisted process and spark plasma sintering to fabricate MgAgSb samples. Different from the sample prepared by the melting process, there is an Ag₃Sb second phase in the matrix of MgAgSb prepared by the microwave-assisted process. Ag₃Sb obviously increases carrier concentration and leads to low electrical resistivity and high power factor. The maximum power factor is about 2000 μWm⁻¹ K⁻², which is double larger than that of MgAgSb sample prepared by the melting process. During the microwave-assisted process, many stacking faults and edge dislocations are introduced into the matrix which leads to the appearance of flake sub-grains with a thickness of 0.5–1 μm. These defects strengthen phonons’ scattering and reduce the lattice thermal conductivity. The decoupling of transport properties leads to 20% enhancement of ZT value (∼0.76@548 K), compared with the sample prepared by the melting process.