制备工艺对La改性的Ca_3Co_4O_9基陶瓷热电性能的影响

INFLUENCE OF SYNTHESIS TECHNIQUES ON THERMOELECTRIC PROPERTIES OF La-MODIFIED Ca_3Co_4O_9-BASED CERAMICS

利用常压烧结、冷等静压成型后常压烧结及热等静压烧结3种不同制备工艺,合成了(Ca0.9La0.1)3Co4O9热电材料。XRD分析表明:不同工艺制备的样品均为Ca3Co4O9相。样品的SEM照片显示:晶粒为片状结构;热等静压烧结制备的样品,其片状结构不明显,但致密度较之另外两种工艺大幅度提高,其相对密度为95%。制备工艺对(Ca0.9La0.1)3Co4O9热电材料Seebeck系数影响不大,但热压烧结样品能大幅度提高(Ca0.9La0.1)3Co4O9电导率。在一定温度范围内,随温度升高,功率因子大幅度增加,对于热压烧结的样品尤为显著。

(Ca0.9La0.1 )3Co4O9 thermoelectric materials were prepared by three kinds of synthesis techniques, ordinary pressing sintering (OP), ordinary pressing sintering after cold isostatic pressed forming (COP) and hot isostatic pressing sintering (HP). The XRD results indicate that all samples prepared by different techniques are single Ca3Co4O9 phase. The grains for the OP and COP samples are in lamellar structure observed by the SEM. The lamellar structure is not distinct for samples sintered by hot isostatic pressing sintering, but for those samples, the relative density can be improved greatly and reaches to about 95%. The synthesis techniques have little influence on the samples' Seebeck coefficient but have a great effect on the electric conductivity of samples prepared by hot-pressing sintering. The power factor will increase with the increase of the temperature, especially for the samples prepared by the hot-pressing sintering technique.