This Small Business Innovation Research (SBIR) Phase I project will develop a novel and cost-effective processing and manufacturing route to produce high-temperature ceramic oxide thermoelectric materials comprised of nanosized (< 40 nm) grains. Research has shown that a reduction in grain size below 100 nanometers in thermoelectric materials results in an increase in thermal resistance and overall thermoelectric performance by up to 40%. The technical challenge involved is to maintain the correct powder composition and the sintered grain size below 40 nm throughout the required processing steps. The spark plasma sintering (SPS) technique limits grain growth to a minimum, such that grain size of the sintered ceramic remains below 100 nanometers, thus preserving all of the enhanced material properties. This project will evaluate the effects of processing parameters on physical properties of the thermoelectric powder, including particle size, surface area, impurity gain, green and sintered density, grain size and final microstructure. The thermoelectric properties of the resulting powder will be evaluated, including Seebeck coefficient, dc conductivity, thermal conductivity, and ZT. A commercially viable manufacturing process will be demonstrated for scale up to large quantities in the follow-on Phase II project. The broader impact/commercial potential of this project will be the availability of thermoelectric nanomaterials operating at high temperatures (> 800 C), with enhanced thermoelectric properties. As the conservation of energy resources and associated environmental concerns become more critical, societal interest in utilizing thermoelectric devices to generate electricity from waste heat has grown. Thermoelectrics can function in many specialized applications, but have been hindered by a relatively low efficiency and high material costs. Current materials also have production scalability concerns. A new low-cost, high-temperature, high figure-of-merit thermoelectric material is necessary to satisfy commercial demands. The materials to be developed in this project will enable increased market adoption by allowing waste energy harvesting at high temperatures with a relatively low expected low cost of production (under $3/watt). Potential early adopters of these materials include the glass industry, steelmakers, and the automobile industry. According to recent studies, there is almost $300 million worth of wasted energy per year in the glass industry alone. The estimated market for these materials in vehicles is more than $1 billion. This same material processing technology can be adapted for future applications in high ionic conductors for battery and fuel cell technologies, and other ceramic industrial materials
