Forming the locally-gradient Ni@NiTe2 domains from initial Ni inclusions embedded into thermoelectric Bi2Te3 matrix

Abstract

Mixtures of thermoelectric Bi2Te3 powder and ferromagnetic Ni powder were spark-plasma-sintered to prepare bulk composites with different Ni content (0.00, 0.50, 0.85, 1.25 and 1.50 at.%). Hexagonal Bi2Te3, cubic Ni and trigonal NiTe2 phases coexist in the composites. Bi2Te3 phase forms matrix of the composite, whereas Ni and NiTe2 phases correspond to filler. The filler is formed by locally-gradient Ni@NiTe2 (“core–shell”) inclusions. Forming the “core–shell” inclusions is due to high-temperature diffusion redistribution of matrix and filler atoms during the composites sintering. The thermoelectric figure-of-merit of the composites with the locally-gradient inclusions is remarkably enhanced as compared to that of the Bi2Te3 matrix.