High-temperature thermoelectric characteristics of B-site substituted Yb0.1Ca0.9Mn1−x Nb x O3 system (0≤x≤0.1)

Abstract

The thermoelectric performance of Yb0.1Ca0.9MnO3 doped with Nb5+ at B-site is investigated in this paper. It is found that there is a phase transition from O-type to O*-type orthorhombic structure with increasing of Nb doping content, which indicates that the structure distortion becomes more seriously. Since the electron–phonon interaction can be enhanced by the structure distortion, the small polaron formation is promoted in Yb0.1Ca0.9Mn1−x Nb x O3 with increasing Nb content. In the whole measured temperature range, the electrical conductivity can be fitted very well by the adiabatic small polaron hopping model. The activated energy E α is ascending with increasing Nb content. The temperature dependence of Seebeck coefficient S of Yb0.1Ca0.9Mn1−x Nb x O3 shows that the S is basically inversive to the charge carrier concentration. S(T) can be fitted well by the Cutler and Mott model, which indicates that the density of state around the Fermi level is strongly affected by Nb-doping at B-site. It is contrary to those of CaMnO3 and RE0.1Ca0.9MnO3, when Nb content x>0.05, the |S| and σ show a same tendency of the temperature dependence.