High-temperature thermoelectric performance of Ca0.96Dy0.02RE0.02MnO3 ceramics (RE=Ho, Er, Tm)

Perovskite-type Ca0.98Dy0.02MnO3 (CDM) and Ca0.96Dy0.02RE0.02MnO3 (RE=Ho, Er, Tm) (marked as CDM-Ho, CDM-Er, CDM-Tm) ceramics were prepared by solid state reaction. Their thermoelectric properties were evaluated between 300 K and 1000 K. All the samples are single phase with an orthorhombic structure. The introduction of second doping elements for RE=Ho, Er, Tm lead to a larger carrier concentration. As a result, the resistivity decreases from 36.1 mΩ cm for CDM to 12.4 mΩ cm for CDM-Ho at 973 K, while absolute Seebeck coefficient decreases from −300 μV/K for CDM to −196 μV/K for CDM-Tm. The highest power factor is obtained 350 μW/(K2m) at 923 K for Ca0.96Dy0.02Er0.02MnO3 sample. And also the introduction of second element contributes to lower thermal conductivity. The highest figure of merit 0.23 is obtained for RE=Ho, Er samples at 973 K, representing an improvement of about 109% compared with Ca0.98Dy0.02MnO3 sample.