烧结工艺对Ca_3Co_4O_9基热电氧化物电性能的影响

Effect of Preparation Technique on Electrical Properties of Ca_3Co_4O_9-based Thermoelectric Oxide

采用溶胶-凝胶化学法合成了Ca3Co4O9热电氧化物粉末,分别采用陶瓷烧结工艺方法和放电等离子烧结(Spark Plasma Sintering,SPS)的方法制备了Ca3Co4O9热电氧化物块体材料。利用X射线衍射XRD、扫描电子显微镜SEM和电输运参数测试仪分析了所得样品的物相、微观组织结构、晶粒取向度和电输运性能。结果表明,不同制备方法均可得到纯相的Ca3Co4O9热电氧化物块体材料;通过陶瓷烧结工艺方法制备的Ca3Co4O9热电氧化物块体晶粒取向度较低,但随着成型压力的增加而提高;SPS烧结的方法制备的Ca3Co4O9热电氧化物块体晶粒取向度最高;试样电性能随着晶粒取向度的提高逐渐提高,其中SPS烧结方法制备的块体材料电性能最高,在测试温度最高点700℃时功率因子达3.85μWmK-2,远高于普通烧结试样。

The Ca3Co4O9 thermoelectric powders were synthesized by acid sol-gel chemical method. The Ca3Co4O9 thermoelectric bulk materials were prepared by conventional ceramic method as well as the Spark Plasma Sintering（ SPS） method. The phase composition,microstructure,grain orientation and thermal transport properties of the resulting bulk materials were analyzed by X-ray diffraction XRD,Scanning electron microscopy SEM as well as the electrical transport constants measurement apparatus.The results show the single phase compounds by both the bulk material preparation methods. The bulks prepared by conventional ceramic method exhibits low orientation and it could be enhanced by increasing the pressure. The bulks prepared by the SPS method show highest orientation. The electrical properties can be enhanced by increasing the orientation,the bulk sintered by SPS method has the highest electrical properties with the peak value of power factor 3. 85 μW·mK-2at 700 ℃ within the experimental region which is very much higher than that of the bulks prepared by conventional ceramic method.