制备工艺对Ca_3Co_4O_9/Bi_2Ca_2Co_2O_y复合热电材料组织和性能的影响

Effect of preparation process on microstructure and performance of Ca_3Co_4O_9/Bi_2Ca_2Co_2O_y composites

采用助熔剂法和固相反应法分别合成了Ca_3Co_4O_9和Bi_2Ca_2Co_2O_y粉体。配比后分别通过冷压、冷等静压、热压三种制备工艺制得组织取向和致密度不同Ca_3Co_4O_9/Bi_2Ca_2Co_2O_y块体复合材料,测量表征了其热电性能和物相形貌。结果表明,冷等静压工艺减弱了材料中颗粒的取向,降低了热导率,973 K时为1.35 W·K^(–1)·m^(–1);热压工艺提高了样品的致密度,降低了电阻率,973 K时功率因子达到了4.0×10^(–4) W·m^(–1)·K^(–2)。

Ca3Co4O9 and Bi2Ca2Co2Oy powder were synthesized separately by method of flux and solid phase synthesis reaction. After matching , Ca3Co4O9 / Bi2Ca2Co2Oy block composites with different orientation and density were procured by three types of preparation technology, including cold pressing, cold isostatic pressing and hot pressing. To that end, the characteristics of thermoelectric properties and phase morphology were measured. The results show that cold isostatic pressing technology weakens the grain orientation of materials and reduces the thermal conductivity. In this case, when the temperature reaches 973 K, the thermal conductivity is 1.35 W·K–1·m–1. Hot-pressing technology improves the density of the samples and reduces the electrical resistivity. Therefore, when the temperature reaches 973 K, the power factor is 4.0×10–4 W·m–1·K–2.