Abstract
Cu1.8S has been considered as a potential thermoelectric (TE) material for its stable electrical and thermal properties, environmental benignity, and low cost. Herein, the TE properties of nanostructured Cu1.8S1−xTex (0 ⩽ x ⩽ 0.2) bulks fabricated by a facile process combining mechanical alloying (MA) and room-temperature high-pressure sintering (RT-HPS) technique were optimized via eliminating the volatilization of S element and suppressing grain growth. Experimentally, a single phase of Cu1.8S was obtained at x = 0, and a second Cu1.96S phase formed in all Cu1.8S1−xTex samples when 0.05 ⩽ x ⩽ 0.125. With further increasing x to 0.15 ⩽ x ⩽ 0.2, the Cu2−zTe phase was detected and the samples consisted of Cu1.8S, Cu1.96S, and Cu2−zTe phases. Benefiting from a modified band structure and the coexisted phases of Cu1.96S and Cu2−zTe, the power factor is enhanced in all Cu1.8S1−xTex (0.05 ⩽ x ⩽ 0.2) alloys. Combining with a drastic decrease in the thermal conductivity due to the strengthened phonon scatterings from multiscale defects introduced by Te doping and nano-grain boundaries, a maximum figure of merit (ZT) of 0.352 is reached at 623 K for Cu1.8S0.875Te0.125, which is 171% higher than that of Cu1.8S (0.130). The study demonstrates that doping Te is an effective strategy to improve the TE performance of Cu1.8S based materials and the proposed facile method combing MA and RT-HPS is a potential way to fabricate nanostructured bulks.
Highlights
Thermoelectric (TE) technology can convert thermal energy directly into electricity and vice versa, which has been expected as a promising solution for the growing demands of green and renewable energy [1,2]
A series of highly dense Cu1.8S1–xTex bulks with nanograins were prepared by a facile method combining mechanical alloying (MA) and room-temperature high-pressure sintering (RT-HPS) technique, which can efficiently eliminate the volatilization of S element and suppress grain growth
Combining with a drastically decreased thermal conductivity due to strengthened phonon scatterings from multiscale defects introduced by Te doping and nano-grain boundaries, a maximum ZT of 0.352 is reached at 623 K for Cu1.8S0.875Te0.125, which is 171% higher than that of Cu1.8S (0.130)
Summary
Thermoelectric (TE) technology can convert thermal energy directly into electricity and vice versa, which has been expected as a promising solution for the growing demands of green and renewable energy [1,2]. Investigation of Te doping in Cu1.8S is desirable and high TE performance can be expected based on the potential effect of band structure modification and reduction, which has rarely been reported so far. A high-pressure process can be used as an effective avenue to change the crystal and electronic structures of TE materials for performance enhancement [32,33,34]. A series of highly dense Cu1.8S1–xTex bulks with nanograins were prepared by a facile method combining MA and room-temperature high-pressure sintering (RT-HPS) technique, which can efficiently eliminate the volatilization of S element and suppress grain growth. Combining with a drastically decreased thermal conductivity due to strengthened phonon scatterings from multiscale defects introduced by Te doping and nano-grain boundaries, a maximum ZT of 0.352 is reached at 623 K for Cu1.8S0.875Te0.125, which is 171% higher than that of Cu1.8S (0.130)
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