Thermoelectric Performance of Surface-Engineered Cu<sub>1.5–<i>x</i></sub>Te–Cu<sub>2</sub>Se Nanocomposites
Congcong Xing, Yu Zhang, Ke Xiao, Xu Han, Yu Liu, Bingfei Nan, Maria Garcia Ramon, Khak Ho Lim, Junshan Li, Jordi Arbiol, Bed Poudel, Amin Nozariasbmarz, Wenjie Li, María Ibáñez, Andreu Cabot
Abstract
Cu 2– x S and Cu 2– x Se have recently been reported as promising thermoelectric (TE) materials for medium-temperature applications. In contrast, Cu 2– x Te, another member of the copper chalcogenide family, typically exhibits low Seebeck coefficients that limit its potential to achieve a superior thermoelectric figure of merit, zT, particularly in the low-temperature range where this material could be effective. To address this, we investigated the TE performance of Cu 1.5– x Te–Cu 2 Se nanocomposites by consolidating surface-engineered Cu 1.5 Te nanocrystals. This surface engineering strategy allows for precise adjustment of Cu/Te ratios and results in a reversible phase transition at around 600 K in Cu 1.5– x Te–Cu 2 Se nanocomposites, as systematically confirmed by in situ high-temperature X-ray diffraction combined with differential scanning calorimetry analysis. The phase transition leads to a conversion from metallic-like to semiconducting-like TE properties. Additionally, a layer of Cu 2 Se generated around Cu 1.5– x Te nanoparticles effectively inhibits Cu 1.5– x Te grain growth, minimizing thermal conductivity and decreasing hole concentration. These properties indicate that copper telluride based compounds have a promising thermoelectric potential, translated into a high dimensionless zT of 1.3 at 560 K.