Abstract The spectroscopic properties of bright red-emitting Eu3+-doped Ca9Y(PO4)7 (x = 0.01–1.00 mol) nanophosphors synthesized by the time-saving combustion approach were investigated by employing Judd-Ofelt theory. The band-gap analysis for the pure host was executed utilizing the Kubelka-Munk function. Scheming of Judd-Ofelt parameter was done for the first time in CYPO: Eu3+ system. The value of Ω2 higher than Ω4 of Eu3+ in the CYPO of 5D0→7F2 transition leads to the red luminescence of the nanophosphors revealing the local surrounding and high covalency of the Eu3+ ions in a matrix. The other radiative parameters, such as effective bandwidth (Δλeff), fluorescence branching ratios (β) and stimulated emission cross-section (δem) of the characteristic transitions have been calculated from emission spectra. The luminescence decay profiles are found to be triple-exponential in nature and in good agreement to the outcomes of the Rietveld analysis, i.e. presence of three non-centrosymmetric sites acquired by the Eu3+ ions. Auzel's model was employed to find the intrinsic radiative transition lifetime of 5D0 level (t = 0.819 ms). The sharp red-emission with high color purity and quantum yield efficiency up to 91.7% of Ca9Y1-x(PO4)3: xEu3+ nanophosphors makes them capable aspirants for WLEDs using near ultra-violet excitation, solid-state laser and display systems.

中文翻译：

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Judd-Ofelt框架中Eu3+激活的Ca9Y(PO4)7纳米磷光体的光谱特性

摘要 利用 Judd-Ofelt 理论研究了通过节省时间的燃烧方法合成的亮红色发光 Eu3+ 掺杂 Ca9Y(PO4)7 (x = 0.01–1.00 mol) 纳米荧光粉的光谱特性。纯宿主的带隙分析是利用 Kubelka-Munk 函数执行的。Judd-Ofelt参数在CYPO:Eu3+体系中首次进行了规划。在 5D0→7F2 转变的 CYPO 中，Ω2 的值高于 Eu3+ 的 Ω4 导致纳米磷光体的红色发光，揭示了 Eu3+ 离子在基质中的局部周围和高共价性。其他辐射参数，如有效带宽 (Δλeff)、荧光分支比 (β) 和特征跃迁的受激发射截面 (δem) 已从发射光谱计算出来。发现发光衰减曲线本质上是三指数的，并且与 Rietveld 分析的结果非常一致，即存在由 Eu3+ 离子获得的三个非中心对称位点。Auzel 模型被用来寻找 5D0 能级 (t = 0.819 ms) 的固有辐射跃迁寿命。Ca9Y1-x(PO4)3: xEu3+ 纳米磷光体具有高色纯度和高达 91.7% 的量子产率效率的锐利红光发射，使其成为使用近紫外激发、固态激光器和显示系统的 WLED 的理想候选者。