Synthesis of Er³⁺ doped KNbO₃ nanocrystals and nanoceramics with outstanding up-conversion luminescence behaviors

Rare earth doped perovskite has become one of the most attractive multifunctional materials benefiting from the unique ferro-/piezoelectric, photocatalytic and photoluminescence properties. In this contribution, a series of Er³⁺ doped KNbO₃ nanocrystals with distinctive morphologies, i.e., nanocubes, nanocuboids, and quasi-nanospheres, were prepared via a facile molten salt synthesis method. Furthermore, using the as-synthesized nanocrystals, the Er³⁺ doped KNbO₃ ceramics with homogeneous nanograins were obtained. The growth mechanism of the nanocrystals with different morphologies and sintering process of the nanoceramics were rationally proposed, respectively. It was demonstrated that the morphology of the nanocrystals could be controlled by adjusting the doping amount of Er³⁺ and the structure of the as-sintered nanoceramics strongly depends on the morphology of the pristine nanocrystals. Impressively, the Er³⁺-KNbO₃ nanocrystals and nanoceramics exhibited excellent up-conversion photoluminescence (UC PL) properties. This work may pave a new way to the structure-controlled synthesis of rare earth doped perovskite oxides and related nanoceramics, which show large potential in applications of novel multifunctional devices.