A Power-Generation Test for Oxide-Based Thermoelectric Modules Using p-Type Ca3Co4O9 and n-TypeCa0.9Nd0.1MnO3 Legs

Metal oxides are considered to be promising thermoelectric (TE) materials, especially for high-temperature power-generation applications, because they have many advantages such as low price, light weight, thermal stability, nontoxicity, and high oxidation resistance. For these reasons, oxide-based TE modules were fabricated using p-type pure Ca₃Co₄O₉ and n-type Ca_0.9Nd_0.1MnO₃ legs for power generation at temperatures in excess of 1000?K. This study involved the use of Ag sheets with a Ag paste as electrode materials and alumina plates as a substrate for the modules. The p-type pure Ca₃Co₄O₉ legs were manufactured by spark plasma sintering, and the n-type Ca_0.9Nd_0.1MnO₃ legs were sintered by a conventional process at atmospheric pressure. From a unicouple, a power density as high as 93.2?mW/cm² under a temperature condition of ??T?=?727?K (T _hot?=?1175?K) was obtained. This high power density is believed to be a result of the modified contact of the electrode (notch process) and the optimized material properties (the SPS process and a dopant effect) along with the high ??T obtained in this study (reduced thermal losses because of good packing of thermal insulation). Areas of concern for future research include the following: (1) the measured open-circuit voltage from the present unicouples was only 94.3% of the theoretical voltage, and (2) the internal resistance value was as high as 490% of the theoretical resistance.