Cu-doping boosts the thermoelectric properties of layered compound LaOBiS2 with weak anisotropy

Abstract

Layered compounds like Bi2Te3 and SnSe are attracting great interest for applications in thermoelectric devices, mainly due to their low lattice thermal conductivity from large anharmonicity. Herein, we report the thermoelectric properties of the quaternary layered compound LaOBiS2, which is a n-type semiconductor constructed by stacking of fluorite-type [LaO]+ layers and rock-salt-type [BiS2]- layers. Our results reveal that the as-sintered LaOBiS2 sample features weak anisotropy due to the almost random arrangement of crystalline grains with nonpreferred-orientation growth. The pristine LaOBiS2 has high intrinsic electrical conductivity and low Seebeck coefficient as a result of a high electron concentration (n = 3.25 ×1020 cm−3, 300 K) from anionic vacancy. Meanwhile, the total thermal conductivity of LaOBiS2 is as low as 1.10 W m−1 K−1 at 873 K. Cu-doping improve the overall thermoelectric properties, which induces a decrease in both electrical conductivity and thermal conductivity. The maximum zT is 0.24 at 873 K for the sample with dopant Cu of 1 %, indicating a 33 % increase compared with pristine LaOBiS2. Our work demonstrates that constructing semiconductors by functional building blocks is an effective approach to design thermoelectric compounds.