Enhanced thermoelectric properties of layered anisotropic PbBi₂Te₄ through the suppression of bipolar diffusion effect via Se alloying

The layered ternary PbBi2Te4 is regarded as a promising thermoelectric material due to its intricate crystal structure. However, current research on PbBi2Te4 primarily focuses on theoretical calculations and predictions, with limited investigations conducted on its actual thermoelectric transport properties. In this study, we synthesized the single-phase PbBi2Te4 compound using the high-temperature melting method. The research findings indicate that PbBi2Te4 exhibits significant anisotropic thermoelectric properties and a pronounced bipolar diffusion effect, which can be attributed to its unique layered crystal structure and relatively narrow bandgap. This bipolar diffusion effect remarkably exacerbates the Seebeck coefficient of PbBi2Te4 and amplifies its thermal conductivity. To address these challenges, we effectively manipulated the electronic band structure of PbBi2Te4 and enlarged the bandgap through the incorporation of Se alloying. The thermoelectric performance of PbBi2Te4 has been significantly enhanced as a result of the increase in Seebeck coefficient and reduction in thermal conductivity. Ultimately, a superior ZT value of similar to 0.52 at 673 K is achieved in PbBi2(Te0.85Se0.15)(4), representing an impressive improvement of similar to 49% compared to the pure PbBi2Te4. These results demonstrate the promising potential of ternary PbBi2Te4 as a thermoelectric material.