Enhanced thermoelectric properties in p-type Bi_0.4Sb_1.6Te₃ alloy by combining incorporation and doping using multi-scale CuAlO₂ particles

Multi-scale CuAlO₂ particles are introduced into the Bi_0.4Sb_1.6Te₃ matrix to synergistically optimize the electrical conductivity, Seebeck coefficient, and the lattice thermal conductivity. Cu element originating from fine CuAlO₂ grains diffuses into the Bi_0.4Sb_1.6Te₃ matrix and tunes the carrier concentration while the coarse CuAlO₂ particles survive as the second phase within the matrix. The power factor is improved at the whole temperatures range due to the low-energy electron filtering effect on Seebeck coefficient and enhanced electrical transport property by mild Cu doping. Meanwhile, the remaining CuAlO₂ inclusions give rise to more boundaries and newly built interfaces scattering of heat-carrying phonons, resulting in the reduced lattice thermal conductivity. Consequently, the maximum ZT is found to be enhanced by 150% arising from the multi-scale microstructure regulation when the CuAlO₂ content reaches 0.6 vol.%. Not only that, but the ZT curves get flat in the whole temperature range after introducing the multi-scale CuAlO₂ particles, which leads to a remarkable increase in the average ZT.