The Study On Ca3Co4O9of Preparation And Properties Based Nanocomposite Thermoelectric Materials

Due to the advantages such as small-size, high-reliability, long-lifetime and pollution-free, thermoelectric materials are of interest for applications as cooling devices and power generator used in craft or recycling of the industrial waste heat. In recent years, due to its unique layered crystal structure and thermoelectric transport properties, and good thermal stability, non-toxic, pollution-free, long-term work in the high-temperature oxidation environment, so the cobalt-based oxide thermoelectric materials have great prospects in the exhaust gas, waste heat re-use areas, become one of the current research focus.In this paper, The Sol-Gel method combined with the Field Activited and Pressure Assisted synthesis process prepare Ca3Co4O9/xwt.%SiO2(x=0.1,0.5,1,2), Ca3Co4O9/0.5wt.%SiO2/xwt.%Ag(x=3,6,9) and Ca3Co4O9/xwt.%CNTs(x=0.05,0.1,0.5,1) nanocomposite thermoelectric materials. The microstructure and thermoelectric property test can explore the effect of the nano-second phase addition to Ca3Co4O9on microstructure and thermoelectric property of Ca3Co4O9.The Ca3Co4O9powder with uniform particle size can be synthesized by sol-gel method which use nitrate as raw materials, doped nano-second phase can be obtained by ultrasonic vibration, and then pure phase Ca3Co4O9compounds can be gained after FAPAS sintering, the second phase can stably exist in the matrix; From the SEM photos we can see that the crystal structure of Ca3Co4O9particles is lamellar, the grain size and shape of Ca3Co4O9are affected after doping the nano-second phase.The result showed that the electrical property can be improved when nano second phase(nano-SiO2or CNTs) were doped in oxides thermoelectric materials Ca3CO4O9. The performance came to the best when x=0.5among the system Ca3CO4O9/xwt.%SiO2(x=0.1,0.5,1,2), the Power factor of Ca3Co4O9/0.5wt.%SiO2come to highest value0.349mW/mk2, improved by8%compared to the highest level of pure sample0.324at800℃; The property of Ca3CO4O9/0.5wt.%SiO2was further researched by incorporating Ag grain. The results shows that the orientation of the Ca3CO4O9/xwt.%SiO2grain were effectively changed after doped Ag. Power Factor of the double doped sample (Ca3Co4O9/0.5wt.%SiO2/9wt.%Ag) reach the top (0.389mW/mk2), higher than the top of Ca3CO4O9/0.5wt.%SiO2(0.349mW/mk2).Power Factor of Ca3CO4O9/0.1wt.%CNTs comes to the point (0.595mW/mk2) at800℃among the system Ca3CO4O9/xwt.%CNTs (x=0.05,0.1,0.5,1).