TiO _x -Based Thermoelectric Modules: Manufacturing, Properties, and Operational Behavior

Abstract

Substoichiometric titanium oxides are attractive thermoelectric materials for high-temperature modules. Their advantages are availability, economy, and safety. This paper gives results of thermoelectric data on scale-up titanium suboxides, manufacturing technologies of TiO _x modules, glass coating as an option for oxidation protection, and test results of TiO _x modules. The thermoelectric efficiency of TiO _x is low compared with established thermoelectric materials. However, TiO _x is very attractive for economic reasons, and there are still expectations for efficiency rise by modification of the material’s microstructure. TiO _x can be produced in large quantities of several tens of kilograms. A manufacturing process for TiO _x -based unileg n-type modules has been established, including all technological steps. The design of the TiO _x -based modules was optimized for the thermoelectric conversion process and thermal robustness. A test device was used for experimental analysis with maximum temperature of 600°C at the hot side and 100°C at the cold side. This initial test revealed similar power output and internal resistance of all fabricated modules. Furthermore, thermal cycles with increasing and decreasing temperatures at the hot side were realized to characterize the reliability and stability of the modules. Additionally, modules were tested in a hot gas test rig to simulate the thermal stresses during power generation in the exhaust line of a passenger car.