Effect of Al Doping and Cu Deficiency on the Microstructures and Thermoelectric Properties of BiCuSeO-Based Thermoelectric Materials

Abstract

The effects of low-price element Al doping and Cu deficiency on the thermoelectric performance of Bacchus are studied in the paper. Bi_1−xAl_xCu_1−xSeO (x = 0, 0.025, 0.05, 0.075, 0.1, 0.125) were prepared by high-energy ball-milling, high-temperature solid-state reaction and hot-press sintering. Due to the massive substitutions of Bi³⁺ with Al²⁺, the Al in Bacchus exceeds the solution limit and the thermal conductivity decreases significantly. The structure of the thermoelectric materials is lamellar and tetragonal, and Al doping and Cu deficiency can refine the grains. The deficiency of Cu can reduce the generation of Al₄Cu₉, which guarantees the stability of the sample at high temperature and leads to the formation of a large number of holes. Moreover, the hole carrier again becomes the main carrier of the sample. Therefore, all the samples belong to p-type semiconductors at room temperature. In the results, the combination of optimized conductivity and thermal conductivity is helpful to improve the ZT value; the maximum the ZT value is 0.90 of Bi_0.875Al_0.125Cu_0.875SeO at 873 K, which is 2.46 times higher than that of Bacchus.