Suppressed bipolar effect and high average ZTave in CuO-doped Bi0.46Sb1.54Te3 bulks with a large size

Currently, bismuth telluride-based zone-melted ingots dominate the commercial thermoelectric (TE) market. However, bismuth telluride-based zone-melted ingots with a layered lattice structure are brittle, posing challenges for their application in miniature devices. Their polycrystalline alloys have robust mechanical strength. However, the electrical conductivity of a p-type polycrystalline BiSbTe alloy bulk deteriorates. In the current study, the Bi0.46Sb1.54Te3 powder was from crushed zone-melted ingots. Large-sized polycrystalline (CuO)xBi0.46Sb1.54Te3 (x = 0, 0.003, 0.01, 0.03 and 0.1) bulks were prepared via the hot-pressing method under 65MPa at 510°C for 15min. The electrical conductivity was improved remarkably by the acceptor doping effect. The bipolar effect of the Seebeck coefficient and thermal conductivity at high temperatures was suppressed significantly due to increased majority carrier centration and enlarged bandgaps. Consequently, their TE performance (the dimensionless TE figure of merit, ZT) was significantly improved and the ZTmax and ZTave reached 1.4 and 1.27, respectively.