Improved thermoelectric properties of hole-doped Bi2−xNaxBa2Co2Oy ceramics

Abstract

In this work, Bi[Formula: see text]Na[Formula: see text]Ba2Co2O[Formula: see text] ([Formula: see text][Formula: see text]=[Formula: see text]0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) ceramic samples were prepared by the conventional solid phase method. The influence of Na element doping on the thermoelectric properties of samples was investigated from 300 K to 950 K. Compared with undoped sample, the Seebeck coefficients of Na-doped samples have only a slight decrease. While, the electrical resistivity of the Na-doped samples reduces, for Bi[Formula: see text]Na[Formula: see text]Ba2Co2O[Formula: see text] ceramic samples with [Formula: see text][Formula: see text][Formula: see text][Formula: see text]0.15, the electrical resistivity decreases with increasing Na doping amounts due to the hole-doping effect. In addition, its temperature-dependent resistivity exhibits metallic electrical conductivity behavior. While, the samples with [Formula: see text][Formula: see text][Formula: see text][Formula: see text]0.20 exhibit semiconductor electrical conductivity behavior at the temperature range of 473–823 K, because of the significant reduction of the electrical resistivity and the slight decrease of Seebeck coefficients, the power factors of the doped samples get a significant improvement. For the most suitable doped sample Bi[Formula: see text]Na[Formula: see text]Ba2Co2O[Formula: see text], its ZT value can reach a better value of 0.2 at 873 K.