New Nanofibrous Structured CsAg₅Te₃ Exhibiting Ultralow Thermal Conductivity and High Figure of Merit

Low-thermal-conductivity materials are ideal candidates for high-performance thermoelectric materials. CsAg5Te3 is a new metal-rich chalcogenide with an inherent low-thermal conductivity. However, due to its complex crystal structure, obtaining high-purity CsAg5Te3 poses a serious challenge. In addition, the high price of pure metals Cs, Ag, and Te leads to the high cost of traditional solid-state methods for preparing CsAg5Te3. To address these issues, the preparation of CsAg5Te3 with a nanostructured fiber morphology was carried out using a low-energy-intensity scalable microwave method. The CsAg5Te3 nanofibers were then assembled using spark plasma sintering technology to prepare CsAg5Te3 bulk with a layered structure. The lattice thermal conductivity of the CsAg5Te3 nanostructured material is 0.19 W m(-1) K-1, which is almost the lowest among the state-of-the-art thermoelectric materials. Finally, at 673 K, the maximum zT value of CsAg5Te3 can reach similar to 0.67. This study provides a feasible pathway for low-cost preparation of nanostructured thermoelectric materials.