Seeking New Layered Oxyselenides with Promising Thermoelectric Performance

Abstract

Abstract Layered oxyselenides have been widely investigated as promising thermoelectric materials due to their unique merits such as super‐lattice structural features and intrinsic complexity, which contributes to low thermal conductivity and easily controllable electrical properties. Newly developed Bi 2 LnO 4 Cu 2 Se 2 (Ln stands for lanthanide) oxyselenides are found to be potential thermoelectric systems since they have excellent electrical conductivity over 10 3 S cm −1 . In this work, unique energy and time‐saving method combined self‐propagating high‐temperature synthesis (SHS) with spark plasma sintering (SPS) is adopted to successfully prepare a highly pure Bi 2 LnO 4 Cu 2 Se 2 instead of a traditional solid‐state reaction. To explore the most suitable lanthanide for Bi 2 LnO 4 Cu 2 Se 2 , thermoelectric performance in a wide temperature range (300 to 923 K) of Bi 2 LnO 4 Cu 2 Se 2 (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) is deeply evaluated and studied. Ultimately, with a relatively high electrical conductivity, moderate Seebeck coefficient, and extremely low thermal conductivity, a maximum ZT value of ≈0.27 at 923K is achieved in Bi 2 DyO 4 Cu 2 Se 2 , which is 4 times larger than that of the ever‐reported Bi 2 YO 4 Cu 2 Se 2 and proves a potential thermoelectric system for further investigation. This work may provide some enlightenment and broaden the horizon in finding new thermoelectric materials, especially for complex layered compounds.