This study uses hydrothermal synthesis combined with calcination to prepare magnesium aluminate spinel powders, discussing the impact of hydrothermal conditions and the stoichiometric ratio on the structure and intrinsic luminescence of magnesium aluminate spinel. The results show that at a low hydrothermal temperature of 120 °C for 24 hours, a standard MgAl₂O₄ phase can be obtained. However, at higher hydrothermal temperatures (≥140 °C), regular nano-sized rod-like Al-rich spinel tends to form, along with the precipitation of magnesium oxide impurities. As the hydrothermal temperature increases, the minimum aluminum stoichiometry required for the initial formation of pure phase Al-rich spinel also increases, and there's a polynomial relationship between temperature (T) and the minimum aluminum stoichiometry (x₀). When the sample is excited with ultraviolet light at λ_ex=255 nm (4.86 eV), within a certain non-stoichiometric range, both Mg-rich and Al-rich samples exhibit higher intrinsic luminescence intensity than standard spinel. Specifically, at a hydrothermal temperature of 160 °C with an aluminum stoichiometry of 5.6, the sample exhibits high-purity blue light emission; however, excessive aluminum also causes quenching effects. Mg-rich spinel enhances intrinsic luminescence through the photoionization process in F defect centers, while Al-rich spinel structures are more likely to enhance luminescence directly through F⁺ centers.

中文翻译：

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铝酸镁尖晶石的水热合成和本征发光特性


本研究采用水热合成结合煅烧制备铝酸镁尖晶石粉末，讨论了水热条件和化学计量比对铝酸镁尖晶石结构和本征发光的影响。结果表明，在120 °C的低水热温度下，持续24 h，可获得标准的MgAl₂O₄相。然而，在较高的热液温度 （≥140 °C） 下，随着氧化镁杂质的沉淀，往往会形成规则的纳米级棒状富铝尖晶石。随着热液温度的升高，最初形成纯相富铝尖晶石所需的最小铝化学计量也增加，温度 （T） 和最小铝化学计量 （x₀） 之间存在多项式关系。当样品被 λ_ex=255nm （4.86eV） 的紫外光激发时，在一定的非化学计量范围内，富镁和富铝样品都表现出比标准尖晶石更高的本征发光强度。具体来说，在 160 °C 的水热温度下，铝化学计量为 5.6 时，样品表现出高纯度的蓝光发射;然而，过量的铝也会引起淬火效应。富含镁的尖晶石通过 F 缺陷中心的光电离过程增强本征发光，而富铝尖晶石结构更有可能直接通过 F⁺ 中心增强发光。