Studies have been carried out to understand the specific role of the alkali charge compensator on the luminescence properties of an alkali ion (Li⁺, Na⁺, and K⁺) codoped SrWO₄:Eu phosphor. The oxidation state of the europium ion was found to be +3 on the basis of X-ray absorption near edge structure (XANES) measurements. This is the first report of its kind where opposite effects of Li⁺ ion and Na⁺/K⁺ ions on photoluminescence intensity have been observed. Li⁺ ion codoping enhanced the photoluminescence intensity from SrWO₄:Eu³⁺ phosphor while Na⁺/K⁺ ion codoping did not. On the other hand, the luminescence lifetime is maximum for the Na⁺ ion codoped sample and minimum for the Li⁺ ion codoped sample. The results could be explained successfully using time-resolved luminescence, positron annihilation lifetime spectroscopy (PALS), and extended X-ray absorption fine structure (EXAFS) spectroscopy measurements. Changes in the Eu–O bond length and Debye–Waller Factor (σ²) upon Li⁺/Na⁺/K⁺ codoping were monitored through EXAFS measurements. PALS also highlighted the fact that Li⁺ codoping is not contributing to reduction in the cation vacancies and might be occupying interstitial sites rather than lattice positions due to its very small size. On europium doping there is lowering in symmetry of SrO₈ polyhedra from S₄ to C₆, which is reflected in an intense electric dipole transition in comparison to the magnetic dipole transition. This is also corroborated using trends in Judd–Ofelt parameters. The results have shown that the luminescence lifetime is better when the vacancy concentration is lower as induced by Na⁺ and K⁺ codoping, while the emission intensity is higher in the samples when distortion around Eu³⁺ is reduced as induced by Li⁺ codoping.

中文翻译：

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解释电荷补偿剂在SrWO ₄：Eu ³⁺：A（A = Li ⁺，Na ⁺，K ⁺）光学性质中的作用：使用光致发光，正电子An没和X射线吸收的光谱学见解

已经进行了研究以了解碱电荷补偿剂对碱金属离子（Li ⁺，Na ⁺和K ⁺）共掺杂的SrWO ₄：Eu荧光粉的发光性能的特定作用。根据X射线吸收近边缘结构（XANES）测量，发现ion离子的氧化态为+3。这是该领域的第一个报道，其中观察到Li ⁺离子和Na ⁺ / K ⁺离子对光致发光强度的相反作用。Li ⁺离子共掺杂增强了SrWO ₄：Eu ³⁺荧光粉的光致发光强度，而Na ⁺ / K⁺离子共掺杂没有。另一方面，Na ⁺离子共掺杂样品的发光寿命最大，而Li ⁺离子共掺杂样品的发光寿命最小。使用时间分辨发光，正电子an没寿命光谱（PALS）和扩展X射线吸收精细结构（EXAFS）光谱测量可以成功地解释结果。在欧盟-O键长和改变德拜-沃勒因子（σ ²）在锂⁺ /钠⁺ / K ⁺共掺杂是通过EXAFS测量来监测。PALS也强调了一个事实，李⁺共掺杂并不能帮助减少阳离子空位，并且由于其很小的尺寸，可能占据了间隙位置而不是晶格位置。在euro掺杂时，SrO ₈多面体的对称性从S _4降低到C ₆，这与磁偶极跃迁相比，反映在强烈的电偶极跃迁中。Judd–Ofelt参数的趋势也证实了这一点。结果表明，Na ⁺和K ⁺共掺杂引起的空位浓度越低，发光寿命越长，而Eu ³⁺周围的畸变则样品的发光强度越高。由于Li ⁺共掺杂而降低。