The effect of Mn substitution on thermoelectric properties of Ca3MnxCo4−xO9 at low temperatures

The effects of partial substitution of Mn for Co on the thermoelectric properties of Ca3MnxCo4−xO9 (x=0, 0.03, 0.9), prepared by sol–gel process, were investigated at the temperatures from 380 K down to 5 K. The results indicate that the substitution of Mn for Co results in increase in thermopower at temperatures >∼80 K, and substantial (23–31% at 300 K) decrease in lattice thermal conductivity in the whole temperature range investigated. The temperature behavior of ZT suggests that Ca3MnxCo4−xO9 with light Mn substitution would be a promising candidate for high-temperature thermoelectric applications.