Tuning thermoelectric properties of BiCuSeO via Ca–Sr–Ba Co-doping for high-performance thermoelectric applications

BiCuSeO has attracted significant interest in the field of thermoelectric materials due to its layered crystalline structure, along with advantages such as abundant elemental availability, low thermal conductivity, and outstanding thermal stability. However, the inherently low electrical conductivity of BiCuSeOlimiting overall thermoelectricperformance. To address this, as an effective strategy to enhance thermoelectric performance, BiCuSeO was subjected to tri-element co-doping. Bi 1−3x (CaSrBa) x CuSeO (x = 0.0, 0.02, 0.03, 0.04, and 0.05) ceramics were synthesized using an advanced fabrication process that combined high-energy ball milling with hot-press sintering techniques. Substituting Ca 2+ , Sr 2+ , and Ba 2+ at the Bi 3+ sites effectively optimized the carrier concentration, increased the effective mass, and significantly enhanced the electrical conductivity from 9.67 to 91.55 S cm −1 . Notably, the power factor of the Bi 0.88 (CaSrBa) 0.04 CuSeO sample reached 476.54 μW m −1  K −2 at 323 K. and electrical conductivity. Simultaneously, the introduction of lattice defects through co-doping considerably enhanced phonon scattering, reducing the lattice thermal conductivity to 0.342 W m −1  K −1 for Bi 0.85 (CaSrBa) 0.05 CuSeO, compared with 0.447 W m −1  K −1 for the pristine sample. Consequently, a maximum dimensionless figure of merit ( ZT ) of 0.65 was achieved at 773 K for Bi 0.88 (CaSrBa) 0.04 CuSeO. These findings provide valuable insights into improving the thermoelectric performance of BiCuSeO-based materials through multi-element co-doping.