Post-calcination, a novel method to synthesize cobalt oxide-based thermoelectric materials

作者：Kang Min Gyu; Cho Kwang Hwan; Kim Jin Sang; Nahm Sahn; Yoon Seok Jin; Kang Chong Yun^*

来源：Acta Materialia, 2014, 73: 251-258.

DOI：10.1016/j.actamat.2014.04.008

• Ca3Co4O9
• Phase decomposition
• Sintering
• Thermoelectrics

Cobalt oxide-based Ca3Co4O9 ceramics are known for their good thermoelectric (TE) performance and chemical stability at high temperatures (<900 degrees C); however, the crystalline phase of these ceramics is unstable beyond 926 degrees C due to thermal decomposition. This low limit (926 degrees C) on the sintering temperature produces a very low-density material with poor TE properties. Here, a novel method (post-calcination) to synthesize high-density and single-phase Ca3Co4O9 ceramics is investigated by high-temperature X-ray diffraction analysis. The post-calcination method, which includes cooling and reheating of the phase decomposed Ca3Co4O9 ceramics, synthesizes high-density (relative density = 92%) and single-phase Ca3Co4O9 ceramics via a solid-state reaction at a high sintering temperature of 1200 degrees C, and improved TE properties (power factor = 0.245 mW K-2 in 1 at 800 degrees C) are observed. The post-calcination method is expected to be applicable to Ca3Co4O9 and other materials that are difficult to obtain in high-density form due to thermal decomposition. Furthermore, this technique improves the sinterability and production efficiency without using complicated processes.

• 出版日期2014-7