Pengli Si,Xinxin Wang,Yajing Wang,Guangmeng You,Xueke Gu,Zheng Jiang,Jingdan Lei,Chao Wang
N-type PbSe-based materials have emerged as a research focus in medium-to-high temperature thermoelectric applications due to their high carrier mobility, stability across wide temperature ranges, and cost-effectiveness. However, simultaneously maintaining high carrier mobility while reducing lattice thermal conductivity remains a critical challenge for PbSe-based materials. Research demonstrates that constructing coherent interfaces optimizes charge carrier scattering, thereby maintaining high carrier mobility while achieving thermal conductivity reduction. In this work, after Cu 2 S alloying treatment, coherent nanostructured precipitates consisting of Cu 2 S (monoclinic phase) and PbS (cubic phase) are formed at grain boundaries. The lattice mismatch at the interface is maintained below 4.5%, which consequently leads to only a marginal reduction in charge carrier mobility. Meanwhile, Cu 2 S, as a dynamic electron donor, increases the carrier concentration. Additionally, the diffusion of Cu + ions introduces lattice disorder, which, in combination with the low- to mid-frequency phonon scattering from the nano-precipitates, significantly reduces the lattice thermal conductivity. As a result, a ZT value of 1.53 is achieved at 773 K. The Pb 1.02 Se-0.5% Cu 2 S composite prepared in this study exhibits superior thermoelectric performance compared to most n-type PbSe-based materials, demonstrating that the introduction of coherent nanostructures constitutes an effective strategy for enhancing the thermoelectric properties of n-type PbSe.
N-type PbSe thermoelectric materials encounter challenges in improving the power factor due to the single-band structure near the Fermi level, which obstructs typical band convergence. The primary strategy for enhancing the thermoelectric figure of merit (ZT) for n-type PbSe involves reducing lattice thermal conductivity (κ lat ) by introducing various defect structures. However, lattice mismatches resulting from internal defects within the matrix can diminish carrier mobility, thereby affecting electrical transport properties. In this study, n-type AgCuTe-alloyed PbSe systems achieve a peak ZT value of ≈1.5 at 773 K. Transmission electron microscopy reveals nanoprecipitates of Ag 2 Te, the room temperature second phase of AgCuTe, within the PbSe matrix. Meanwhile, a unique semi-coherent phase boundary is observed between the PbSe matrix and the Ag 2 Te nanoprecipitates. This semi-coherent phase interface effectively scatters low-frequency phonons while minimizing damage to carrier mobility. Additionally, the dynamic doping effect of Cu atoms from the decomposition of AgCuTe within the matrix further optimize the high-temperature thermoelectric performance. Overall, these factors significantly enhance the ZT across the whole temperature range. The ZT value of ≈1.5 indicates high competitiveness compared to the latest reported n-type PbSe materials, suggesting that these findings hold promise for advancing the development of efficient thermoelectric systems.
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