Synergetic effects of co-dispersed Cu and insulating HfO2 nanoparticles enabled high thermoelectric figure of merit in Bi0.5Sb1.5Te3 composites

Highlights: • Synergistically optimized the TE properties by dual incorporation of Cu and insulating HfO₂ nanoparticles. • S was enhanced due to the energy filtering effect (EFE) caused by the potential barriers. • A maximum ZT of 1.35 and an outstanding η_max of ~9.2% were obtained. Considerable efforts have been invested in improving the thermoelectric (TE) performance of Bi_0.5Sb_1.5Te₃ (BST) materials for room temperature power generation and cooling. In this contribution, we study the effect of co-dispersed Cu and insulating HfO₂ nanoparticles (NPs) into BST matrix and synergistically optimized TE performance. The Seebeck coefficient increased for the BST-Cu/xHfO₂ (x = 0.5 and 1.0 wt%) composites compared to BST-Cu sample due to enhance the energy filtering effect (EFE) caused by the potential barriers. Specifically, the dual incorporated (Cu and 0.5HfO₂) BST sample reaches 1.35 at 400 K, which is 80% higher than that of BST at the same temperature. A peak ZT_ave of 1.25 and maximum conversion efficiency of ~9.2% were obtained in the temperature range of 300–500 K. The significant enhancement of ZT in dual incorporated samples mainly attributed to the increased power factor (PF) and shifting the minimum κ at higher temperatures.