Abstract This work aims at studying optical properties of Eu3+ dopant in K0.3Bi0.7F2.4 host and seeking their applications. A series of orange red emitting K0.3Bi0.7F2.4:Eu3+ phosphors were synthesized via a chemical precipitation reaction method at room temperature, which is convenient, economical and less time consuming. XRD and Rietveld refinement results confirm the pure phase of as-prepared materials. The optimal doping concentrations are determined to be 40%mmol, and both of the corresponding concentration quenching mechanism have been validated to be dipole−dipole interactions. Additionally, the Judd-Ofelt theory was selected to study the local structure environment of the Eu3+ ions in the K0.3Bi0.7F2.4 host lattices and the tendency of J-O parameters (Ω2>Ω4) confirm the asymmetric environment around Eu3+ ions. The thermogravimetric analysis and activation energy results of K0.3Bi0.7F2.4:Eu3+ materials with high thermal stability exhibit promising performances for temperature sensor applications. Moreover, the temperature-dependent of samples are investigated in a large temperature range of 303−573 K to explore thermal quenching performance. Significantly, luminescent temperature sensing has been accomplished by specifically utilizing thermal quenching performance and high temperature sensitivity around 1.54×104K-1 is achieved, which indicates that K0.3Bi0.7F2.4:Eu3+ fluorescent nanoparticles can be exploited for promising luminescent thermometer. Another important results are the K0.3Bi0.7F2.4:40%Eu3+ nanoparticles exhibiting orange red emission with the CIE coordinates (0.6226, 0.3747) and the luminescence photographs of K0.3Bi0.7F2.4:40%Eu3+ samples under UV lamp (365 nm) irradiation revealing obvious orange red. Besides, the color purity of orange red K0.3Bi0.7F2.4:40%Eu3+ phosphor is demonstrated to be about 98.4%, which indicate that the as-prepared K0.3Bi0.7F2.4:Eu3+ phosphors may be a candidate component applied in UV w-LEDs.

中文翻译：

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用于温度传感应用的 K0.3Bi0.7F2.4:Eu3+ 荧光粉的室温合成、光致发光特性和 Judd Ofelt 分析

摘要 本工作旨在研究K0.3Bi0.7F2.4主体中Eu3+掺杂剂的光学特性并寻求其应用。采用化学沉淀反应法在室温下合成了一系列橙红色发光K0.3Bi0.7F2.4:Eu3+荧光粉，该方法方便、经济且耗时少。XRD 和 Rietveld 精修结果证实了所制备材料的纯相。最佳掺杂浓度确定为 40% mmol，并且两种相应的浓度猝灭机制均已被验证为偶极-偶极相互作用。此外，选择 Judd-Ofelt 理论来研究 K0.3Bi0.7F2.4 主晶格中 Eu3+ 离子的局部结构环境和 JO 参数 (Ω2>Ω4) 的趋势证实了 Eu3+ 离子周围的不对称环境。具有高热稳定性的 K0.3Bi0.7F2.4:Eu3+ 材料的热重分析和活化能结果显示出在温度传感器应用中的良好性能。此外，在 303-573 K 的大温度范围内研究了样品的温度依赖性，以探索热淬火性能。值得注意的是，通过专门利用热猝灭性能实现了发光温度传感，并实现了大约 1.54×104K-1 的高温度灵敏度，这表明 K0.3Bi0.7F2.4:Eu3+ 荧光纳米粒子可用于有前途的发光温度计。另一个重要的结果是 K0.3Bi0.7F2.4:40%Eu3+ 纳米粒子在 CIE 坐标 (0.6226, 0.3747) 和 K0.3Bi0.7F2.4 的发光照片中表现出橙红色发射：40%Eu3+ 样品在紫外灯（365 nm）照射下呈现明显的橙红色。此外，橙红色 K0.3Bi0.7F2.4:40%Eu3+ 荧光粉的色纯度约为 98.4%，表明所制备的 K0.3Bi0.7F2.4:Eu3+ 荧光粉可能是候选组分应用于 UV w-LED。