Features of the thermoelectric properties of composites based on Bi _0,5Sb_1,5Te3 with submicron NiTe₂ inclusions

This paper presents the results of a study on the thermoelectric properties (electrical resistivity, Seebeck coefficient, and total thermal conductivity) of a composite with a p-type low-temperature thermoelectric Bi0,5Sb1,5Te3 matrix and inclusions of the semiconductor nickel ditelluride (NiTe2) as a filler. The studied composites were fabricated using solvothermal synthesis for the NiTe2 filler, and mechanochemical activation followed by spark plasma sintering for the Bi 0,5Sb1,5Te3 matrix and the composites themselves. It has been established that the introduction of 1 wt.% of NiTe2 into the composite matrix leads to a significant enhancement of the thermoelectric figure of merit (ZT) to 1,1 at 425 K, which is 16% higher compared to the matrix material itself (ZT ~ 0,95). This enhancement can be attributed to the effective phonon scattering at the NiTe2/Bi0,5Sb1,5Te3 interfaces, which leads to a reduction in the total thermal conductivity, while the power factor (S2/ρ) remains sufficiently high. A further increase in NiTe2 content to 2,5 and 5 wt.% leads to a degradation of ZT in the composites, which may be due to microstructural features such as the formation of a secondary phase of elemental tellurium. This phase forms «thermal bridges», thereby increasing thermal conductivity and slightly deteriorating the electronic transport properties.

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