Abstract
Thermoelectric (TE) oxides are paid great attention due to their good thermal stability, but the high lattice thermal conductivity (κL) largely impedes their further development. In this paper, a Hollandite-type structure and multiple dopants in KxTi8O16-based oxides are studied to seek for an ultralow κL. Benefited from the complex crystal structure, a relatively low κL (2.13 W m−1 K−1 at 373 K) is obtained in K1.78Ti8O16. The Ba dopant can make the [TiO6] octahedra undistorted and increase the Ti3+ amount, leading to a doubled power factor. Meanwhile, the dual-doping effect of Ba and Nb dopants can further decrease the κL to 0.85 W m−1 K−1. Thus, a competitive zT value of 0.18 is obtained in Ba1.15Ti7.2Nb0.8O16 at 1073 K. This work demonstrates that the TE performance of Hollandite-type oxides deserves to be further studied and a complex crystal structure can be designed to achieve a high zT value.
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