T-phase (Ba,Ca)₂SiO₄:Eu²⁺, showing excellent luminescent thermal stability, has a positionally disordered structure with the splitting of five atom sites, but until now the reason has remained unclear. Herein, we investigate the coordination environments of each cation site in detail to understand the origins of the atom site splitting. We find that the three cation sites in the split-atom-site model are optimally bonded with ligand O atoms compared to the unsplit-atom-site model. This atom site splitting results in larger room and smaller room for each splitting cation site, which just accommodates larger Ba²⁺ ions and smaller Ca²⁺ ions, respectively, leading to more rigid structure. Based on the X-ray diffraction data refinement, the boundary of the T-phase for (Ba_1–xCa_x)₂SiO₄ is redetermined. The Eu²⁺-doped T-phase (Ba,Ca)₂SiO₄ phosphors show excellent luminescent thermal stability, which can be attributed to optimal bonding and more rigid structure with atom site splitting. These results indicate that T-phase (Ba,Ca)₂SiO₄:Eu²⁺ phosphors have promise for practical applications.

中文翻译：

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T相（Ba，Ca）₂ SiO ₄：Eu ²⁺荧光粉上无序结构上最佳键合的结果和改善的发光性能

T相（Ba，Ca）₂ SiO ₄：Eu ²⁺具有优异的发光热稳定性，具有位置混乱的结构，具有五个原子位点的分裂，但是直到现在，其原因仍不清楚。在这里，我们详细研究每个阳离子位点的配位环境，以了解原子位点分裂的起源。我们发现，与未分裂原子位点模型相比，分裂原子位点模型中的三个阳离子位点与配体O原子最佳结合。原子位点分裂会导致每个分裂阳离子位点的空间变大，而空间变小，这恰好容纳较大的Ba ²⁺离子和较小的Ca ²⁺离子分别导致更刚性的结构。根据X射线衍射数据的细化，重新确定了（Ba _{1– x} Ca _x）₂ SiO ₄的T相边界。掺杂Eu ^2+的T相（Ba，Ca）₂ SiO ₄荧光粉显示出极好的发光热稳定性，这可以归因于最佳键合和具有原子位点分裂的更刚性的结构。这些结果表明，T相（Ba，Ca）₂ SiO ₄：Eu ²⁺荧光粉具有实际应用前景。