Effects of La, Sm and Yb doping on thermoelectric properties of Ca0.98Er0.02MnO3 at high temperature

Abstract

A series of perovskite-type ceramic materials Ca_0.98Er_0.02MnO₃ (CDM) and Ca_0.96Er_0.02Re_0.02MnO₃ (Re = La, Sm, Yb) (denoted as CDM-La, CDM-Sm, CDM-Yb) which worked from 300 K to 1000 K with excellent thermoelectric properties was prepared by a sol–gel and cold-pressing method. XRD results revealed that the prepared samples are uniform crystalline particles with high purity. The results of XPS characterization show that an increase in the Mn³⁺ ratio is caused by the introduction of dual-doping. The characterization results of resistivity and Seebeck coefficient reveal that the carrier concentration is optimized by dual doping, accordingly the resistivity decreases continuously and the value of the Seebeck coefficient increases continuously. The highest power factor of 219 μW (K² m)⁻¹ is obtained at 773 K for the Ca_0.96Er_0.02Yb_0.02MnO₃ sample. And also the introduction of a second element contributes to lower the thermal conductivity. The highest figure of merit, ZT, of the Ca_0.96Er_0.02Yb_0.02MnO₃ sample exceeds 0.12 at 973 K.