The enhanced thermoelectric properties of Pb-doped Cu2.85Ag0.15Sb0.985−xBi0.015Se4 samples synthesized via vacuum melting and cold isostatic pressing

Cu 3 SbSe 4 has garnered significant attention due to its low thermal conductivity, complex elemental composition, and economic feasibility. In this study, Cu 2.85 Ag 0.15 Sb 0.985−x Bi 0.015 Pb x Se 4 (x=0, 0.05, 0.10, and 0.15) samples were synthesized using a system of vacuum melting combined with cold isostatic pressing techniques. The impact of Pb doping on the thermoelectric properties of Cu 2.85 Ag 0.15 Sb 0.985 Bi 0.015 Se 4 was comprehensively investigated. The experimental results revealed a notable increase in carrier concentration, from 2.95×10 18 cm −3 to 8.31×10 19 cm −3 , leading to a substantial improvement on the electrical conductivity. At 573 K, the electrical conductivity of the Cu 2.85 Ag 0.15 Sb 0.835 Bi 0.015 Pb 0.15 Se 4 reached 234.26 S cm −1 , while the power factor of the Cu 2.85 Ag 0.15 Sb 0.885 Bi 0.015 Pb 0.10 Se 4 achieved a maximum value of 883.5 μW m −1 K −2 . The incorporation of Pb induced lattice defects, which modified the phonon mean free path and enhanced phonon scattering. As a result, the increased phonon scattering contributed to a reduction in lattice thermal conductivity within the Cu 2.85 Ag 0.15 Sb 0.985 Bi 0.015 Se 4 sample. The thermoelectric figure of merit (ZT) for the Cu 2.85 Ag 0.15 Sb 0.935 Bi 0.015 Pb 0.05 Se 4 reached a peak value of approximately 0.74 at 573 K, marking a 157.4% improvement compared to that of Cu 2.85 Ag 0.15 Sb 0.985 Bi 0.015 Se 4 (∼0.47). This study demonstrates that multi-element doping is a highly effective strategy for optimizing the thermoelectric properties of the Cu 3 SbSe 4 system.