Abstract A simple recipe for synthesizing green emitting Mn2+-doped ZnAl2O4 phosphor has been developed. Metal-organic complexes, with their unique properties, were employed as precursors to obtain phase-pure, nanocrystalline material in the as-prepared form within just 5 min of microwave irradiation. The Mn2+ doping concentration that showed the highest photoluminescence (PL) intensity was optimized and a comprehensive investigation of the structural and optical properties were made for various annealing temperatures. Rietveld refinement of the samples annealed at 1200 °C and 1400 °C, showed that the cationic inversion in the spinel decreased from 3.4 to 2.1% and this change was validated by the X-ray photoelectron spectroscopy results. XPS confirmed that the inversion for Zn2+, Al3+, and Mn2+ cations decreased with annealing temperature, despite of which, inversion remained at 20%, 10%, and 15%, respectively for the sample annealed at 1400 °C, emphasizing the fact that synthesis plays an important role in controlling the amount of inversion in an otherwise normal spinel. Electron paramagnetic resonance spectra of the as-prepared and the samples annealed at high temperatures confirmed that the Mn2+ hyperfine spectrum was not just a function of the crystal field environment but also strongly depends on the doping concentration. The PL spectrum taken at different annealing temperatures, comprised of the characteristic 4T1 (G) → 6A1 (S) spin-forbidden Mn2+ transitions, showed that the emission intensity depends on the material crystallinity. The sample annealed at 1400 °C displayed a significantly higher PL intensity compared to those annealed at lower temperatures. The variation of PL spectrum of this sample was investigated between 9 K and 300 K to determine the origins of the asymmetry at room temperature and the vibrational sidebands at lower temperatures. The energy levels of the Mn2+ dopant, calculated theoretically and verified experimentally, were used to determine the spectroscopic parameters such as the Racah B and C values and the crystal field energy, Dq. These values showed that the Mn2+ was in a weak tetrahedral field. This work demonstrates a technologically important, green, and swift technique in synthesizing phosphors for various applications in displays, bioimaging, solid state lighting, etc.

中文翻译：

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一种用于合成绿色发光 Mn2+ 掺杂 ZnAl2O4 的新微波方法：对其结构和光学性质的详细研究

摘要 已开发出一种用于合成绿色发光 Mn2+ 掺杂 ZnAl2O4 荧光粉的简单配方。金属-有机配合物以其独特的性质被用作前驱体，在微波辐射的短短 5 分钟内获得制备形式的相纯纳米晶材料。对显示最高光致发光 (PL) 强度的 Mn2+ 掺杂浓度进行了优化，并对各种退火温度下的结构和光学特性进行了全面研究。在 1200 °C 和 1400 °C 下退火的样品的 Rietveld 精修表明，尖晶石中的阳离子转化率从 3.4% 降低到 2.1%，并且 X 射线光电子能谱结果证实了这种变化。XPS 证实 Zn2+、Al3+ 和 Mn2+ 阳离子的转化率随退火温度降低，尽管如此，对于在 1400 °C 下退火的样品，反转率分别保持在 20%、10% 和 15%，这强调了合成在控制其他正常尖晶石中的反转量方面起着重要作用的事实。所制备的和在高温下退火的样品的电子顺磁共振谱证实 Mn2+ 超精细谱不仅是晶体场环境的函数，而且还强烈依赖于掺杂浓度。在不同退火温度下获得的 PL 光谱，包括特征 4T1 (G) → 6A1 (S) 自旋禁止 Mn2+ 跃迁，表明发射强度取决于材料结晶度。与在较低温度下退火的样品相比，在 1400 °C 下退火的样品显示出明显更高的 PL 强度。在 9 K 和 300 K 之间研究了该样品的 PL 光谱的变化，以确定室温下不对称性的起源和较低温度下的振动边带。Mn2+ 掺杂剂的能级，通过理论计算和实验验证，用于确定光谱参数，例如 Racah B 和 C 值以及晶体场能 Dq。这些值表明 Mn2+ 处于弱四面体场中。这项工作展示了一种在合成荧光粉方面具有重要的技术意义、绿色和快速的技术，用于显示器、生物成像、固态照明等的各种应用。Mn2+ 掺杂剂的能级，通过理论计算和实验验证，用于确定光谱参数，例如 Racah B 和 C 值以及晶体场能 Dq。这些值表明 Mn2+ 处于弱四面体场中。这项工作展示了一种在合成荧光粉方面具有重要的技术意义、绿色和快速的技术，用于显示器、生物成像、固态照明等各种应用。Mn2+ 掺杂剂的能级，通过理论计算和实验验证，用于确定光谱参数，例如 Racah B 和 C 值以及晶体场能 Dq。这些值表明 Mn2+ 处于弱四面体场中。这项工作展示了一种在合成荧光粉方面具有重要的技术意义、绿色和快速的技术，用于显示器、生物成像、固态照明等的各种应用。