In this study, magnesium aluminate nanopowders doped with manganese ions (MgAl2O4:0.1% Mn2+) were prepared by citrate sol–gel technique. The consequences on the structural, morphological and optical properties when varying the annealing period (AP) at a fixed annealing temperature of 800 °C and dopant concentration (0.1% Mn2+) were investigated. The AP was varied at the range of 1–6 h. X-ray powder diffraction (XRD) results showed that doping with 0.1% Mn2+ and varying the AP did not influence the crystal structure of the host (un-doped) material. The scanning electron microscope (SEM) images suggested that doping does not influence the morphology of the prepared nanopowders and varying the AP slightly influence the particle size. Transition electron microscopy (TEM) image suggested that the crystallite sizes were below 15 nm. The ultraviolet–visible (UV–Vis) diffuse reflection spectroscopy showed that the band gap of the MgAl2O4:0.1% Mn2+ can be tuned from 5.04 to 4.58 eV with varying AP. Photoluminescence (PL) results showed two emission peaks located at around 413 and 655 nm. They were attributed to the defect levels within the host material and to the (4T1 → 6A1) transitions of Mn2+, respectively. Increasing the AP significantly influences the luminescence of the prepared powders. The CIE coordinate results showed that the bluish emission colour can be changed to the violet region when AP was increased.

中文翻译：

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改变退火时间对 MgAl2O4:0.1% Mn2+ 纳米磷光体结构、形貌和光学性能的影响

在本研究中，通过柠檬酸盐溶胶-凝胶技术制备了掺杂有锰离子（MgAl2O4：0.1% Mn2+）的铝酸镁纳米粉体。研究了在 800 °C 的固定退火温度和掺杂剂浓度 (0.1% Mn2+) 下改变退火时间 (AP) 对结构、形态和光学特性的影响。AP 在 1-6 小时的范围内变化。X 射线粉末衍射 (XRD) 结果表明，掺杂 0.1% Mn2+ 和改变 AP 不会影响主体（未掺杂）材料的晶体结构。扫描电子显微镜 (SEM) 图像表明，掺杂不影响制备的纳米粉末的形态，改变 AP 对粒径略有影响。跃迁电子显微镜 (TEM) 图像表明微晶尺寸低于 15 nm。紫外-可见 (UV-Vis) 漫反射光谱表明，MgAl2O4:0.1% Mn2+ 的带隙可以在 5.04 到 4.58 eV 之间调整，而 AP 不同。光致发光 (PL) 结果显示两个发射峰位于 413 和 655 nm 附近。它们分别归因于主体材料内的缺陷水平和 Mn2+ 的 (4T1 → 6A1) 跃迁。增加AP显着影响制备的粉末的发光。CIE坐标结果表明，当AP增加时，蓝色的发射颜色可以改变为紫色区域。它们分别归因于主体材料内的缺陷水平和 Mn2+ 的 (4T1 → 6A1) 跃迁。增加AP显着影响制备的粉末的发光。CIE坐标结果表明，当AP增加时，蓝色的发射颜色可以改变为紫色区域。它们分别归因于主体材料内的缺陷水平和 Mn2+ 的 (4T1 → 6A1) 跃迁。增加AP显着影响制备的粉末的发光。CIE坐标结果表明，当AP增加时，蓝色的发射颜色可以改变为紫色区域。