Evaluating the efficacy of spark plasma sintering, hot pressing, and cold pressing for PbTe materials

Developing thermoelectric (TE) materials that are both efficient and stable over time requires low-cost, simplified fabrication techniques that effectively control microstructure and transport properties. While advanced fabrication methods such as hot pressing (HP) and spark plasma sintering (SPS) are widely used, alternative approaches that enhance phonon scattering without degrading electrical performance are highly desirable. In this work, we systematically investigate the impact of different processing techniques – cold pressing (CP), hot pressing, and spark plasma sintering – on the structural and thermoelectric properties of PbTe material. We demonstrate that high-pressure cold pressing (2 GPa), followed by controlled annealing, can reduce the lattice thermal conductivity by 10-15 % compared to HP and SPS while maintaining comparable electrical conductivity and Seebeck coefficient values. This improvement is attributed to enhanced phonon scattering at grain boundaries, a mechanism that can be applied to a wide range of TE materials. Additionally, we assess the long-term stability and reproducibility of thermoelectric properties in the most promising cold-pressed sample, demonstrating its potential for use in the fabrication of thermoelectric converters.