Effect of spark plasma sintering conditions on the thermoelectric properties of (Bi0.25Sb0.75)2Te3 alloys
- Effect of spark plasma sintering conditions on the thermoelectric properties of (Bi0.25Sb0.75)2Te3 alloys
- 임상순; 김주헌; 권범진; 김성근; 박형호; 이기석; 백정민; 최원준; 김동익; 현도빈; 김진상; 백승협
- Thermoelectric; Bismuth antimony telluride; Spark plasma sintering; Microstructure
- Issue Date
- Journal of alloys and compounds
- VOL 678, NO 5, 396-402
- As a field-assisted technique, spark plasma sintering (SPS) enables densification of specimens in a very short period of time compared to other sintering techniques. For high performance thermoelectric material synthesis, SPS is widely used to fabricate nanograin-structured thermoelectric materials by rapidly densifying the nanopowders suppressing grain growth. However, the microstructural evolution behavior of thermoelectric materials by SPS, another important process during sintering, has been rarely studied. Here, we explore SPS as a tool to control the microstructure by long-time SPS. Using p-type (Bi0.25Sb0.75)2Te3 thermoelectric materials as a model system, we systematically vary SPS temperature and time to understand the correlations between SPS conditions, microstructural evolution, and the thermoelectric properties. Our results show that the relatively low eutectic temperature (∼420 °C) and the existence of volatile tellurium (Te) are critical factors to determine both microstructure and thermoelectric property. In the liquid-phase sintering regime, rapid evaporation of Te leads to a strong dependence of thermoelectric property on SPS time. On the other hand, in the solid-phase sintering regime, there is a weak dependence on SPS time. The optimum thermoelectric figure-of-merit (Z) of 2.93 × 10−3/K is achieved by SPS at 500 °C for 30 min. Our results will provide an insight on the optimization of SPS conditions for materials containing volatile elements with low eutectic temperature.
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