High thermoelectric performance of all-oxide heterostructures with carrier double-barrier filtering effect

Abstract

Thermoelectric materials can realize significant energy savings by generating electricity from untapped waste heat; however, the coupling of the thermoelectric parameters unfortunately limits their efficiency and practical applications. Herein, rational all-oxide TiC1-xOx@TiOy-TiO2 (x<1, 1<y<2) heterostructures with significantly enhanced thermoelectric properties have been designed, and a high dimensionless figure of merit (ZT) value of up to 0.84 at 973 K was achieved in the all-oxide TiC0.1O0.9@TiOy-TiO2 heterostructures, which is one of the highest values in n-type oxide bulk thermoelectric materials to date. The TiC1-xOx@TiOy heterostructures, which include a thin film of approximately 5–10 nm on the surface of TiC1-xOx compounds prepared by a facile anodization process, exhibit an obvious improvement of the thermoelectric power factor. Furthermore, an excellent dimensionless figure of merit value was obtained in the TiC1-xOx@TiOy-TiO2 heterostructures prepared by the anodization process assisted by the sol-gel chemical route, which can be attributed to the decrease in the carrier concentration via the carrier double-barrier filtering effect. This work develops a facile strategy for synthesizing core-shell heterostructures and demonstrates their superior ability to optimize thermoelectric energy harvesting. All-oxide heterostructures exhibiting a high thermoelectric performance have been fabricated by scientists in China and Japan. Thermoelectric materials are attractive for generating electricity from waste heat, but their performance is limited by interdependencies between their thermoelectric parameters. Now, Hongmin Zhu at University of Science and Technology Beijing and co-workers have used heterostructure engineering to produce all-oxide composites with a dimensionless figure of merit (ZT) of up to 0.84 at 973 kelvin. They ascribe the excellent thermoelectric properties of these heterostructures to an enhanced Seebeck coefficient resulting from a carrier double-barrier filtering effect. The potential barrier of the heterostructure interface can be engineered by varying the anodization voltage, the TiO2 coating content and the solid-solution level of TiC1−xOx. The composites were produced by a straightforward anodization process in combination with a sol-gel chemical route. The rational all-oxide TiC1-xOx@TiOy-TiO2 heterostructures with the significantly enhanced thermoelectric properties had been designed, and a high dimensionless figure of merit (ZT) value of up to 0.84 at 973 K was achieved in all-oxide TiC0.1O0.9@TiOy-TiO2 heterostructures.