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 (∼350 °C) ion exchange approach to prefabricate metastable phosphors ALa_1–xTa₂O₇:xBi³⁺ (A = K and Na) with RbLa_1–xTa₂O₇:xBi³⁺ serving as precursors. The as-prepared ALa_0.98Ta₂O₇:0.02 Bi³⁺ (A = Rb, K, and Na) share the same Dion–Jacobson type 2D-layered perovskite phase, and photoluminescence analyses show that ALa_0.98Ta₂O₇:0.02 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 ³P₁ or ³P₀ to ground state ¹S₀. The various Bi³⁺ local environments at the crystallographic sites enable the different distributions of emission and excitation spectra, and the photoluminescence tuning of ALa_0.98Ta₂O₇:0.02 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_0.98Bi_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.

中文翻译：

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具有多功能结构和可调光致发光的二维层钙钛矿ALaTa ₂ O ₇：Bi ³⁺（A = K和Na）荧光体

拓扑化学反应方法对于制造新材料或优化其功能特性必不可少，这对于具有通用结构的二维（2D）层化合物尤为重要。在本文中，我们演示了一种低温（〜350°C）离子交换方法，用于制备亚稳荧光粉ALa _{1– x} Ta ₂ O ₇：x Bi ³⁺（A = K和Na）和RbLa _{1– x} Ta ₂ O ₇：x Bi ³⁺用作前体。制备的ALa _0.98 Ta ₂ O ₇：0.02 Bi ³⁺（A = Rb，K和Na）共享相同的Dion–Jacobson型2D层钙钛矿相，光致发光分析表明ALa _0.98 Ta ₂ O ₇：0.02 Bi ³⁺（A = Rb，K和Na）荧光粉分别显示出在540、550和510 nm处达到峰值的宽发射带，这归因于Bi ³⁺从激发态³ P ₁或³ P ₀到基态¹ S ₀的非辐射跃迁。各种Bi ³⁺晶体学位置的局部环境使发射光谱和激发光谱具有不同的分布，并且通过碱金属离子交换实现了ALa _0.98 Ta ₂ O ₇：0.02 Bi ³⁺（A = Rb，K和Na）荧光粉的光致发光调谐。值得注意的是，优异的三价铋发射与低温离子交换合成的结合产生了一种新型的发黄光的K（La _0.98 Bi _0.02）Ta ₂ O _7。荧光粉已成功应用于基于市售365 nm LED芯片的白色LED器件中。我们可实现的这种低温离子交换策略的案例可以促进对具有吸引人的特性的亚稳磷光体的探索。