Ba-doped calcium cobaltite ceramics prepared by a alternative chemical method

Reference Presenter Authors
06-215 Daniel Thomazini Cesarino, E.M.(Itajuba Federal University); dos Santos, S.F.(São Paulo State University); Thomazini, D.(Itajuba Federal University); Recently, oxides-based thermoelectric materials have been explored. Ca3Co4O9 ceramics have been reported to demonstrate good p-type thermoelectric properties at high temperature. However, n-type oxides with good thermoelectric properties for power generation are still a challenge for high thermoelectric performance. Also, developing simpler synthesis method than conventional one to produce thermoelectric ceramics is needed in order to make the use of these materials economically viable. Ba-doped calcium cobaltite (Ba0.05Ca2.95Co4O9 (Ba-CCO) ceramics were produced by a simplified chemical route. Barium was used as a doping agent to increase the electrical conductivity. The synthesis consists in the dissolution of the nitrate salts of barium, calcium and cobalt in stoichiometry proportions, Ba0.05Ca2.95Co4O9, in deionized water with the subsequent addition of polyethylene glycol. The solution was dried (80 °C) and calcined (600 °C). The resulting powder was uniaxially pressed to form pellets that were sintered at 750°C for 120 minutes. The samples presented relative density about 52% of theoretical density which is similar to that obtained by conventional methods. The presence of CCO phase was observed by X-ray diffraction analyses (DRX). Scanning electron microscopy (SEM) confirmed the presence of nanosized particles of CCO phase. Thermal and electrical characterizations revealed values about 0,68 Wm-1K-1 and 1950 Sm-1, respectively, at 25 °C.
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