Nielsen Ida Gjerlevsen, Sommer Sanna, Iversen Bo Brummerstedt
Center for Materials Crystallography, Department of Chemistry and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
Nanoscale. 2021 Feb 25;13(7):4038-4050. doi: 10.1039/d0nr08587a.
The indium oxides, c-In2O3, h-In2O3, InOOH and In(OH)3, constitute an important class of wide band gap semiconductors. Synthesis of any indium oxide phase involves manoeuvring in a complex matrix of process parameters, and some phases are only obtained through controlled phase transformations. Considering the widespread use of indium oxide semiconductors it is restrictive that no coherent picture exists of the formation mechanisms of individual phases and phase transformations between them. Here we access the indium oxide system through solvothermal synthesis and/or powder calcinations, and we use in situ X-ray scattering in combination with thermal analysis to investigate the complex phase relations. This allows us to unravel synthesis pathways for the different indium oxide phases, and the insight is used to develop procedures for scalable continuous flow solvothermal synthesis. Direct formation of crystalline nanomaterials from precursor solutions was observed for In(OH)3, InOOH and cubic c-In2O3, while formation of hexagonal h-In2O3 requires thermal decomposition of InOOH. The in situ X-ray scattering data reveal new phase transformations from In(OH)3 to InOOH, and from InOOH to c-In2O3. Interestingly, solvothermal synthesis conditions facilitate different reactions mechanisms than dry powder calcinations, and both In(OH)3 and InOOH have different transformations under dry and wet conditions.
氧化铟，如c-In2O3、h-In2O3、InOOH和In(OH)3，构成了一类重要的宽带隙半导体。任何氧化铟相的合成都涉及在复杂的工艺参数矩阵中进行操作，并且某些相只能通过可控的相变来获得。考虑到氧化铟半导体的广泛应用，目前对于各个相的形成机制以及它们之间的相变尚无连贯的认识，这是具有局限性的。在这里，我们通过溶剂热合成和/或粉末煅烧来研究氧化铟体系，并结合原位X射线散射和热分析来研究复杂的相关系。这使我们能够揭示不同氧化铟相的合成途径，并利用这些认识来开发可扩展的连续流溶剂热合成程序。观察到In(OH)3、InOOH和立方相c-In2O3可从前驱体溶液直接形成结晶纳米材料，而六方相h-In2O3的形成需要InOOH的热分解。原位X射线散射数据揭示了从In(OH)3到InOOH以及从InOOH到c-In2O3的新相变。有趣的是，溶剂热合成条件与干粉煅烧相比促进了不同的反应机制，并且In(OH)3和InOOH在干燥和潮湿条件下都有不同的转变。
