Optimization of electrical and thermal transport properties of layered Bi2O2Se via Nb doping

Layered oxygen-containing compound Bi2O2Se is a promising n-type thermoelectric material, favored by its considerably high Seebeck coefficient and low thermal conductivity. Significant preferred orientation along plane (110), identified in the hot-pressed sample, results in obvious anisotropy in the electrical and thermal transport properties. Nb substitution Bi in the insulating layer [Bi2O2]2+ can effectively increase the electron concentration (from 1016 to 1018 cm−3) by two orders of magnitude, while maintaining high mobility. Therefore, a larger power factor of 2.19 μW cm−1 K−2 has been obtained for Bi1.94Nb0.06O2Se at 823 K, which enlarges by three times in comparison with pristine Bi2O2Se (0.673 μW cm−1 K−2). Combined with the inherently low thermal conductivity, the ZT values of Bi1.94Nb0.06O2Se reach 0.195 at 823 K, corresponding to 325% enhancement. This study shows that the substitution of Nb for Bi is a promising way to optimize the thermoelectric properties of Bi2O2Se-based thermoelectric materials.