Two-Dimensional-Layered Perovskite ALaTa(2)O(7):Bi3+ (A = K and Na) Phosphors with Versatile Structures and Tunable Photoluminescence

Topological chemical reaction methods are indispensable for fabricating new materials or optimizing their functional properties, which is particularly important for two-dimensional (2D)-layered compounds with versatile structures. Herein, we demonstrate a low-temperature (similar to 350 degrees C) ion exchange approach to prefabricate metastable phosphors ALa(1-x)Ta(2)O(7):xBi(3+)(A = K and Na) with RbLa1-xTa2O7:xBi(3+)serving as precursors. The as-prepared ALa(0.98)Ta(2)O(7):0.02 Bi3+ (A = Rb, K, and Na) share the same Dion-Jacobson type 2D-layered perovskite phase, and photoluminescence analyses show that ALa(0.98)Ta(2)O(7):0.02 Bi3+ (A = Rb, K, and Na) phosphors exhibit broad emission bands peaking at 540, 550, and 510 nm, respectively, which are attributed to the nonradiative transition of Bi3+ from excited state P-3(1) or P-3(0) to ground state S-1(0) The various Bi3+ local environments at the crystallographic sites enable the different distributions of emission and excitation spectra, and the photoluminescence tuning of ALa(0.98)Ta(2)O(7):0.02 Bi3+ (A = Rb, K, and Na) phosphors are realized through alkali metal ion exchange. Notably, the combination of superior trivalent bismuth emission and low-temperature ion exchange synthesis leads to a novel yellow-emitting K(La-0.98 Bi-0.02)Ta2O7 phosphor which is successfully applied in a white LED device based on a commercially available 365 nm LED chip. Our realizable cases of this low-temperature ion exchange strategy could promote exploration into metastable phosphors with intriguing properties.