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

- Preparing paramagnetic Mn, ferromagnetic Fe and Ni, and nonmagnetic Cu doped Bi0.5Sb1.5Te3 by a magnetic field assisted melting-solidification (HMAMS) method.
- Studying the effect of different dopants on the orientation, microstructure, electrical and thermal transport properties, and thermoelectric performance of Bi0.5Sb1.5Te3 prepared by HMAMS.
- Thermal conductivity was greatly reduced in the ferromagnetic ion doped samples owing to the intensive scattering of phonon by the hierarchical architecture from macroscale to atomic scale scatter centers.

The present work demonstrates the effect of Mn, Fe, Ni and Cu doping on the orientation, microstructure, electrical and thermal transport properties of Bi0.5Sb1.5Te3 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, BSTⅡ 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, BSTⅡ nano-rods even sub-grain boundaries, and a high ZT of ∼1.6 at 323 K was obtained in the ferromagnetic ions doped samples.

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