Preparation And Thermoelectric Properties Of Perovskite CaMnO₃

CaMnO₃ is a environmental-friendly thermoelectric materialsde. It is a potential candidate in the field of high-temperature thermoelectric material, because of its unique crystal structure and high temperature chemical stability. Perovskite CaMnO₃ powder were prepared by sol-gel route. Thermal decomposition behavior of the gel, phase formation, morphology and performance of CaMnO₃ powders were characterized by TG-DTA, XRD, FT-IR, SEM and Seebeck coefficient measuring instrument. The effects of complexing agent, calcination temperature and solution heating conditions to the structure and performance of CaMnO₃ were studied, and the mechanism of how CaMnO₃ powder structure to influence its thermoelectric properties.Study found, via the Microwave-assisted citrate sol-gel method, pure phase CaMnO₃ powder were obtained when the molar ratio of citric acid and total metal ions is 1:1 and 1.5:1 at 800℃. While the molar ratio of citric acid and total metal ions is 1:1 and calcination temperature is 900 ℃, the average crystal grain size is about 27 nm and the particle size is between 40 nm and 90nmWhile EDTA was used as the complexing agent, the molar ratio of EDTA and otal metal ion to achieve pure phase CaMnO₃ is 0.5:1, calcination temperature is900℃and calcination time is 4h. The average crystal grain size is about 22 nm and the particle size is between 100 nm and 200 nm. When pure phase CaMnO₃ was prepared by EDTA-citric acid route, the optimum molar ratio of EDTA,citric acid and total metal ion is 0.5:1:1 and the lowest synthesis temperature is 900℃. It has a larger particle size which distribute from 300 nm to 600 nm.The CaMnO₃ powder prepared by microwave-assisted route, EDTA route and EDTA-citric acid route were pressed into tablets, which factor values were18μW·m-1K-2, 16μW·m-1K-2 and 10μW·m-1K-2.