Enhanced thermoelectric properties in MgAgSb composite with Ag3Sb fabricated by the microwave-assisted process and subsequent spark plasma sintering

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.