Abstract
? 2021 Elsevier B.V.Thermoelectric materials based on Cu1.8S are not hampered by electric-field-driven degradation in real applications, but their high-temperature applications are problematic owing to their tendency to oxidize or spontaneously decompose. Here, we reveal that Cu1.8S powder is gradually oxidized to form a mixture of Cu2O, Cu(SO4), and Cu2O(SO4) at high temperatures under air. Although a dense oxide film is formed on the surface of the sintered Cu1.8S block at high temperature, hindering the oxidation process, the brittle oxide film fails to inhibit the spontaneous decomposition of the Cu1.8S block into the Cu1.96S phase and S vapor at high temperatures. Thus, Cu1.8S thermoelectric materials are unsuitable for applications above 300 °C in air. To address this issue, we partially replaced S atoms with Se; the sintered Cu1.8S0.8Se0.2 blocks exhibited significantly increased anti-oxidation and anti-decomposition capacities in air. In addition, we found that the thermoelectric figure of merit of the sintered Cu1.8S0.8Se0.2 block was 47% higher than that of traditionally prepared, pure Cu1.8S at 450 °C.
NSTL
Elsevier