Investigation on the microstructure and thermoelectric performance of magnetic ions doped Bi0.5Sb1.5Te3 solidified under a magnetostatic field

Abstract The present work demonstrates the effect of Mn, Fe, Ni and Cu doping on the orientation, microstructure, electrical and thermal transport properties of Bi 0.5 Sb 1.5 Te 3 ingots prepared under a 2 T magnetic field. The comparative results show that the c-axis is inclined to perpendicular to magnetic field in the ferromagnetic ions (Fe and Ni) doped samples, while is inclined to parallel to magnetic field in the non-magnetic Cu and paramagnetic Mn doped samples; in addition, the growth of eutectic structure is disturbed intensively in the ferromagnetic ions doped samples, resulting in scattered arrangement of Te trips, BST Ⅱ nano-rods and nano-scale Te crystals. As a consequence, the thermal conductivity in the ferromagnetic ions doped samples are sharply decreased owing to the enhanced scattering of holes and phonons by the hierarchical architecture of phase boundaries, grain boundaries, BST Ⅱ nano-rods even sub-grain boundaries, and a high ZT of ∼1.6 at 323 K was obtained in the ferromagnetic ions doped samples.