Abstract We report on the photoluminescence properties of Sr4Al14O25:Eu2+,Dy3+ (SAED) phosphors modified by adding Ho3+ in excess and partially substituting Dy3+ with Ho3+ (SAEDHs). Samples were produced using an established solid-state synthesis method known to consistently yield long-persistent afterglow phoshors. Substitutions were performed in stoichiometrically modified host lattices (Al/Sr = 3.2, 3.5, 3.7). Partially substituting Dy3+ with Ho3+ resulted in a remarkable increase in photoluminescence (PL) intensity, Ho3+ co-doping caused a shift in the main emission peaks between 494 and 497 nm and introduced new peaks as well. Important from the security application point of view, the PL intensity was significantly improved under both purple (400 nm) and blue (445 nm) illumination. Color shift of the powders from green to a yellowish and pale pink shade resulted from the Ho3+ addition. Afterglow (AG) properties and thermoluminescence (TL) response decreased non-gradually as Dy3+ was substituted by Ho3+, due to possible charge transfer effects caused by Ho3+. AG and TL properties remained more intact in the presence of Ho3+ when the Al/Sr ratio differed from the ideal 3.5 ratio. Rearrangements of trap energy levels, and energy transfer induced by Ho3+ co-doping were analysed by TL. Dy3+/Ho3+ co-dopants and Al/Sr stoichiometric ratios asymmetrically influenced the trapping/detrapping and energy transfer processes of the SAEDH phosphors. The developed new materials meet the general characteristics of long-persistent phosphors: charging by sunlight, efficient light conversion, chemical stability, all-night afterglow observable by the human eye.

中文翻译：

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Ho3+ 共激活 Sr4Al14O25：Eu2+、Dy3+ 荧光粉的发光和颜色特性

摘要 我们报告了通过添加过量 Ho3+ 并用 Ho3+ 部分取代 Dy3+ (SAEDHs) 改性的 Sr4Al14O25:Eu2+,Dy3+ (SAED) 荧光粉的光致发光特性。样品是使用已建立的固态合成方法生产的，已知该方法可始终如一地产生持久的余辉磷光体。在化学计量修饰的主晶格（Al/Sr = 3.2、3.5、3.7）中进行置换。用 Ho3+ 部分取代 Dy3+ 导致光致发光 (PL) 强度显着增加，Ho3+ 共掺杂导致主要发射峰在 494 和 497 nm 之间发生偏移并引入新峰。从安全应用的角度来看，PL 强度在紫色 (400 nm) 和蓝色 (445 nm) 照明下均显着提高。由于添加了 Ho3+，粉末的颜色从绿色转变为淡黄色和淡粉色。由于 Ho3+ 可能引起的电荷转移效应，当 Dy3+ 被 Ho3+ 取代时，余辉 (AG) 特性和热释光 (TL) 响应非逐渐降低。当 Al/Sr 比值与理想的 3.5 比值不同时，在 Ho3+ 存在下，AG 和 TL 特性保持更完整。通过 TL 分析陷阱能级的重排和由 Ho3+ 共掺杂引起的能量转移。Dy3+/Ho3+ 共掺杂剂和 Al/Sr 化学计量比不对称地影响了 SAEDH 荧光粉的俘获/释放和能量转移过程。开发的新材料满足长余辉荧光粉的一般特性：通过阳光充电、高效的光转换、化学稳定性、