Improved thermoelectric performance in p-type Bi_0.48Sb_1.52Te₃ bulk material by adding MnSb₂Se₄

Bismuth telluride (Bi₂Te₃) based alloys, such as p-type Bi_0.5Sb_1.5Te₃, have been leading candidates for near room temperature thermoelectric applications. In this study, Bi_0.48Sb_1.52Te₃ bulk materials with MnSb₂Se₄ were prepared using high-energy ball milling and spark plasma sintering (SPS) process. The addition of MnSb₂Se₄ to Bi_0.48Sb_1.52Te₃ increased the hole concentration while slightly decreasing the Seebeck coefficient, thus optimising the electrical transport properties of the bulk material. In addition, the second phases of MnSb₂Se₄ and Bi_0.48Sb_1.52Te₃ were observed in the Bi_0.48Sb_1.52Te₃ matrix. The nanoparticles in the semi-coherent second phase of MnSb₂Se₄ behaved as scattering centres for phonons, yielding a reduction in the lattice thermal conductivity. Substantial enhancement of the figure of merit, ZT, has been achieved for Bi_0.48Sb_1.52Te₃ by adding an Mn_0.8Cu_0.2Sb₂Se₄ (2 mol%) sample, for a wide range of temperatures, with a peak value of 1.43 at 375 K, corresponding to ~40% improvement over its Bi_0.48Sb_1.52Te₃ counterpart. Such enhancement of the thermoelectric (TE) performance of p-type Bi₂Te₃ based materials is believed to be advantageous for practical applications.