221 Fabrication and performance improvement of CuAlO_2 thermoelectrics by orientation process and densification

Thermoelectric materials can convert the unused thermal energy into the electrical energy. Therefore, thermoelectric materials are expected as a technology to enable efficient use of waste heat. However, thermoelectric materials have several challenges such as using the rare or poisonous elements, and working only at low temperatures. Thus, developments of new thermoelectric materials such as metal oxides are paid much attention. From the above background, CuAlO_2 thermoelectric material was fabricated and the properties have been improved in the previous works. Also, improvement of thermoelectric properties including the decrease of the electrical resistivity is necessary to practical use for thermoelectric oxide materials. In this work, focus on CuAlO_2 with a stratified crystallographic structure has a high anisotropy of electric resistivity. Therefore, we purpose for making the oriented CuAlO_2 thermoelectric material in a control crystallographic orientation to decrease the electrical resistivity and to improve the thermoelectric performance. The multi-press forming process and reactive templated grain growth (RTGG) method were performed for fabricating green compact and sintered compact with orientation. Al_2O_3 powder with plate shape, CuO and CuO_2 powders were used as the source materials.