放电等离子烧结制备Ca_2Co_2O_5热电材料及其性能研究

Preparation and property of Ca_2Co_2O_5 thermoelectric material by spark plasma sintering

以Co(NO3)2·6H2O、Ca(NO3)2·4H2O为原料,NaOH为沉淀剂,采用化学共沉淀方法制备了前驱物。该前驱物预烧后,利用SPS进行烧结获得纯相Ca2Co2O5块体。分别采用DTA TG、XRD和SEM对前驱体的热分解过程、Ca2Co2O5的形成过程进行了表征,并对其热导率进行了测试。结果表明:在pH=13.20获得所需化学计量比的前驱物。该前驱物在700～800℃预烧2h后,采用SPS烧结。烧结温度为800℃,压力30MPa,保温时间5min,可以获得纯相Ca2Co2O5块体。断口形貌为层状,晶粒长约1.4μm。热导率随温度的升高而降低。

The precursor of Ca2Co2O5 was prepared by coprecipitating method using stoichiometric amounts of Co(NO3)2&middot6H2O, Ca(NO3)2&middot4H2O, and NaOH as precipitation agent. After heat treatment, the precursor was sintered by spark plasma sintering (SPS) process. ICP, DTA-TG, XRD and SEM are used to determine the decomposition in the process of heat treatment and the formation of Ca2Co2O5. In order to obtain stoichiometric precursor, the ICP results show the ended pH value was 13.2. The precursor was heat treated in the range of 700°C to 800°C for 2 h, and then sintered by SPS. XRD patterns show that the pure phase Ca2Co2O5 was produced when sintering temperature was 800°C, the pressure was 30 MPa, and last for 5 min. SEM shows that the microstructure of the production was plate-like about 1.4 μm. The thermal conductivity decreases with increasing temperature up to 800°C.