The thermoelectric properties and stability of copper zinc tin sulfide (Cu2ZnSnS4) in air at 300–720 K were evaluated. Cu2ZnSnS4 was chemically stable in air and exhibited a maximum thermoelectric dimensionless figure of merit of 0.1 at 720 K, making it a promising candidate for the p-type leg of thermoelectric devices that operate in air. However, air annealing of Cu2ZnSnS4 with Pt paste induced macroscopic segregation of a ZnS-rich phase, which increased its electrical resistivity. Because Pt is considered a suitable junction material, a barrier material between Cu2ZnSnS4 and Pt paste is needed to realize reliable thermoelectric devices.

We prepared polycrystalline samples of GeBi 6Àx In x Te 10 (x = 0, 0.06, 0.18, 0.3, and 0.6) by melting a stoichiometric mixture of Ge, Bi, In, and Te, followed by quenching in water and annealing at 723 K for 1 week. Under these preparation conditions and irrespective of the degree of In-substitution, the samples contained two different periodic structures: GeBi 6 Te 10 and GeBi 4 Te 7 structures. The relationship between the Seebeck coefficient, electrical resistivity, and phase fraction of the two structures was investigated at room temperature. We concluded that changes in the transport properties for all samples may reflect a mixture effect of the phase fraction of the two structures and the amounts of In-substitution in the framework of the assumed structure model in this study. The thermoelectric properties of the samples with x = 0 and 0.18 were determined from 300 K to 723 K from the measured electrical properties and the reported lattice thermal conductivity. The sample with x = 0.18 had the highest dimensionless figure of merit: ZT max = 0.11 at 466 K, which was 1.8 times larger than that of the sample with x = 0.

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