Effects of Pr and Yb Dual Doping on the Thermoelectric Properties of CaMnO(3)

There has been research on CaMnO(3) with natural abundance, low toxicity, and low cost as promising candidates for n-type thermoelectric (TE) materials. In this paper, Ca(1−2x)Pr(x)Yb(x)MnO(3) with different Pr and Yb contents (x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05) were synthesized by means of coprecipitation. With X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM), researchers characterized the phase structure and morphology of all the samples. The oxidation states of manganese were determined by X-ray photoemission spectroscopy (XPS). The role of Ca-site dual doping in the TE properties was also investigated. Increasing the Pr and Yb contents leads to decreases in the electrical resistivity and Seebeck coefficient, leading to a power factor of 3.48 × 10(−4) W·m(−1)·K(−2) for x = 0.04 at 773 K, which is its maximum. Furthermore, the thermal conductivity (κ) decreases with increasing x, and κ = 1.26 W·m(−1)·K(−1) is obtained for x = 0.04 at 973 K. Ca(0.92)Pr(0.04)Yb(0.04)MnO(3) exhibit a ZT (thermoelectric figure of merit) value of 0.24 at 973 K, approximately 3 times more than that of the pristine CaMnO(3). Thus, the reported method is a new strategy to enhance the TE performance of CaMnO(3).