Electrical properties of Dy3+/Na+ Co-doped oxide thermoelectric [Ca1-x(Na1/2Dy1/2)x]MnO3 ceramics

• The Dy3+/Na+-doped CaMnO3 showed distinctive thermoelectric properties.
• Holes introduced by doping Na+ balanced the electrons introduced by doping Dy3+.
• Geometric distortion increased with the increasing amount of (Dy1/2Na1/2).
• The best electrical property is observed in [Ca0.95(Dy1/2Na1/2)0.05]MnO3 ceramics.

A new Dy3+/Na+ co-doping system was attempted for improving the thermoelectric properties of CaMnO3 system in this paper. [Ca1-x(Na1/2Dy1/2)x]MnO3 samples were produced by the solid state reaction method, and the electrical properties and the microstructure were investigated. The X-ray diffraction data and tolerant factor were obtained, indicating the second phase and the geometric distortion in this system. Besides, compared with the resistivity and the Seebeck coefficient of single Dy-doped system, Dy3+/Na+ co-doping method could partially decrease the variation of carrier concentration as our expectation. More specifically, the holes introduced by doping Na+ could compensate electrons introduced by doping Dy3+, leading to a low variation of carrier concentration. As the result, a relatively high Seebeck coefficient (−251.6 μV/K) and a relatively low resistivity (8.7  mΩ cm) were gained in this system, and the highest power factor value of 298.0 μW/K2m was obtained at 323 K in [Ca0.95(Dy1/2Na1/2)0.05]MnO3.