Seeking New Layered Oxyselenides with Promising Thermoelectric Performance

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 Bi2LnO4Cu2Se2 (Ln stands for lanthanide) oxyselenides are found to be potential thermoelectric systems since they have excellent electrical conductivity over 103 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 Bi2LnO4Cu2Se2 instead of a traditional solid‐state reaction. To explore the most suitable lanthanide for Bi2LnO4Cu2Se2, thermoelectric performance in a wide temperature range (300 to 923 K) of Bi2LnO4Cu2Se2 (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 Bi2DyO4Cu2Se2, which is 4 times larger than that of the ever‐reported Bi2YO4Cu2Se2 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. A series of layered oxyselenides Bi2LnO4Cu2Se2 (Ln = Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) are synthesized by a time‐saving method. The origin of the excellent thermoelectric performance of Bi2LnO4Cu2Se2 is thoroughly investigated. A maximum ZT value of ≈0.27 at 923K is achieved in Bi2DyO4Cu2Se2, which proves to be a potential thermoelectric system for further investigation.