Abstract Novel low temperature sol-gel route for the synthesis nanostructured Hausmanite, Mn3O4with very small crystallite size (9±1 nm) and phase purity is reported. Reaction temperature of 0–5°C and drying temperature of 40°C is the lowest reported so far. Average particle size (8±1 nm) measured from Transmission Electron Microscopy is in good agreement with the crystallite size indicating monodispersed nature. Raman analysis indicates the presence of +4 valence states for Mn over and above +2 and +3and the presence of an Mn2O3 like surface layer. XPS analysis confirms the phase purity as well as the presence of Mn4+ions. Presence of +4 valence state for Mn is attributed to the presence of cation vacancies that lead to disproportionate reactions. UV-visible absorption spectra is quite broad with charge transitions associated with Mn2+, Mn3+ and Mn4+ statesand d-d crystal field transitions. DC electrical conductivity is about two orders of magnitude higher than that of single crystalline Mn3O4 and the conduction mechanism is defect dependent.

中文翻译：

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用于低温合成纳米结构 Mn3O4 的新型溶胶-凝胶法：结构、阳离子价态、光学和电学性质

摘要 报道了一种用于合成纳米结构Hausmanite Mn3O4 的新型低温溶胶-凝胶途径，具有非常小的晶粒尺寸(9±1 nm) 和相纯度。0-5°C 的反应温度和 40°C 的干燥温度是迄今为止报道的最低温度。从透射电子显微镜测量的平均粒径 (8±1 nm) 与表明单分散性质的微晶尺寸非常一致。拉曼分析表明，在 +2 和 +3 之上，Mn 存在 +4 价态，并且存在类似 Mn2O3 的表面层。XPS 分析证实了相纯度以及 Mn4+ 离子的存在。Mn的+4价态的存在归因于导致歧化反应的阳离子空位的存在。紫外可见吸收光谱非常宽，与 Mn2+ 相关的电荷跃迁，Mn3+ 和 Mn4+ 状态和 dd 晶场跃迁。DC 电导率比单晶 Mn3O4 高约两个数量级，并且导电机制取决于缺陷。