Synergistic optimization of thermoelectric and mechanical properties in Cu2SnSe3-based thermoelectric materials through transition-metal co-doping (Fe, Mn)

As a viable p-type thermoelectric (TE) material, Cu 2 SnSe 3 has attracted increasing attention, primarily due to its moderate band gap and tunable electronic structure. Nevertheless, its practical TE utilization is significantly limited by its inherently high lattice thermal conductivity ( κ l ) and suboptimal power factor. Herein, a Fe/Mn co-doping strategy is proposed to concomitantly regulate electrical and thermal transport properties, thereby achieving a remarkable improvement in the overall TE performance. A series of Cu 2 Sn 1–2x Fe x Mn x Se 3 (x = 0, 0.02, 0.04, 0.06) ceramic samples were fabricated via vacuum-based melting followed by hot-press sintering, which concurrently introduced abundant lattice defects and a CuSe secondary phase. These multi-scale structural features significantly enhance phonon scattering, causing a substantial reduction in thermal conductivity. Consequently, the total thermal conductivity of Cu 2 Sn 0.92 Fe 0.04 Mn 0.04 Se 3 is reduced to a minimum value of 0.432 W m −1 K −1 at 773 K. Meanwhile, Fe/Mn co-doping notably increases the charge carrier concentration ( n ), resulting in a dramatic enhancement in electrical conductivity—from 189.8 S cm −1 for Cu 2 SnSe 3 to 1381 S cm −1 for Cu 2 Sn 0.92 Fe 0.04 Mn 0.04 Se 3. Although the Seebeck coefficient exhibites a slight to moderate reduction, the significant increase in electrical conductivity prevails, yielding a substantially optimized power factor ( PF ). A maximum PF of 500.1 μW m −1 K −2 was achieved, together with a peak ZT value of 0.89 at 773 K, representing a 5.23-fold enhancement compared to the undoped Cu 2 SnSe 3 sample ( ZT = 0.17). In addition to enhancing thermoelectric performance, Fe/Mn co-doping significantly improves the mechanical of Cu 2 SnSe 3 . Specifically, the Young’s modulus ( E ) and hardness ( H ) of Cu 2 Sn 0.92 Fe 0.04 Mn 0.04 Se 3 increased by 18.2% and 25.2%, respectively, relative to the undoped sample—demonstrating markedly enhanced mechanical robustness. These results establish Fe/Mn co-doping as an effective and versatile strategy for decoupling electrical and thermal transport in Cu 2 SnSe 3 -based materials, thereby providing a promising pathway toward high-performance thermoelectric materials with superior structural integrity.