Papers by Author: Ryoji Funahashi

Abstract: We report the fabrication of p- and n-type thermoelectric oxide thick films laminated by insulating alumina using electrophoretic deposition and their thermoelectric performance. From the experimental studies performed for optimization of the thermoelectric performance in the p- and n-type mono-layers, the control of sintering temperature for densification and the usage of fine powder were effective for reducing the electrical resistivity of thermoelectric layers. These findings could be applicable also to the triple-layered thick films. When one assumes that two triple-layered films of p- and n-type thermoelectric materials are combined as unicouple of thermoelectric module, an estimated maximum output power was 20 times higher than a measured maximum output power of a previously reported multi-layered thermoelectric module. It was found that precise control of the microstructure in the thermoelectric layers is indispensable for development of the thermoelectric modules based on the electrophoretic deposition.

Abstract: Different versions of thermoelectric unicouples composed of p-type Ca3Co4O9 (Co-349) and n-type LaNiO3 (Ni-113) or CaMnO3 (Mn-113) bulk materials were prepared. In the unicouples p- and n-type legs were connected with Ag electrodes using Ag paste including various oxide powders with various ratios. For the Co-349/Ni-113 unicouples, maximum output power (Pmax) reaches 177mW at a hot side temperature (TH) of 1073K and a temperature differential (ΔT) between TH and cold side temperature of 500K at 6wt% of Co-349 powder. On the other hand, the lowest internal resistance (RI) is observed in a Co-349/Mn-113 unicouple prepared using Ag paste including 3wt% of Mn-113 powder. Thermoelectric modules consisting of 8 pairs of oxide legs were fabricated using the same method with the unicouples. The open circuit voltage (VO) and Pmax increase with increasing TH and reach 0.392 V and 0.314 W, and 0.911 V and 0.233 W at a TH of 1273 K in air for the Co-349/Ni-113 and Co-349/Mn-113 modules, respectively.