Preparation of titanium-tantalum-oxygen composite thermoelectric ceramics through high-pressure and high-temperature method

Abstract

Because of its high stability and low cost, titanium oxide is a very promising thermoelectric material. Improvement of its thermoelectric performance is limited by the strong correlations among conductivity, Seebeck coefficient, and thermal conductivity. It is therefore important to optimize at least two of these three parameters. This paper provides a new idea for the synergistic optimization of the conductivity and thermal conductivity of titanium oxide. Under high temperature and high pressure, the elementary substance Ta can reduce TiO2 to Magnèli phase titanium oxide (mainly Ti8O15), which greatly increases its conductivity. At the same time, the submicron tantalum oxide (Ta2O5) generated during the reaction process can effectively reduce the lattice thermal conductivity and total thermal conductivity, and realize the synergistic optimization of the conductivity and thermal conductivity of the material. The titanium-tantalum-oxygen composite thermoelectric ceramics prepared by the high-pressure and high-temperature (HPHT) method have good thermoelectric and mechanical properties. The maximum zT value of the material at 973 K is 0.176, and its Vickers hardness is 11.14.