Indium oxide(In2O3) under high pressure: rational design of new polymorphs and characterisation of their physico-chemical properties

本项目的主要目标是研究In2O3在> - 30gpa压力下的高压行为。我们计划使用合适的前驱体（形状和尺寸可控的纳米和微尺寸c-In2O3和rh-In2O3）以及适当的掺杂（Fe, Mn）来调整In2O3在高压（HP）和高温（HT）条件下的相变。通过这种方式，我们的目标是调整氧化铟的电学和光学特性，以及模拟下地幔中富含mgsio3矿物的HP行为，从而为行星内部建模提供输入。跨学科的研究包括(i)溶胶-凝胶和水热合成形状和尺寸可控的In2O3多晶体（bixbyite- and刚玉型），这些多晶体将用作在激光加热金刚石砧细胞（LH-DAC）和多砧细胞（MAC）中合成HP-HT的前体；（ii）在HP-HT （>0 GPa, > 1000 K）条件下寻找In2O3在LH-DAC中的相变条件，（iii）在MAC中合成微量新的In2O3多晶体，（iv）通过原位加热XRD和拉曼光谱研究它们的热稳定性，(v)表征它们的物理性质（带隙、载流子密度、电子迁移率），包括在不同温度和气体气氛下的原位表征(热稳定性和化学稳定性，气敏特性)。该提案包括两个关键组成部分：(i)互补合成方法（溶胶和水热），允许控制相组成以及In2O3， In(OH)3和InOOH晶体的大小和形状，这些晶体将用作HP合成的前体。此外，在In2O3、In(OH)3和InOOH晶体中掺杂选定的（Fe, Mn）金属阳离子，以实现可调/定向相变以及晶体生长；（ii） DFT-GGA计算对可能的相变和过渡压力的估计将用于合理设计合成条件。

The main goal of the present project is to investigate the high-pressure behaviour of In2O3 at pressures > 30 GPa. Using appropriate precursors (shape – and size-controlled nanosized and microsized c-In2O3 and rh-In2O3) as well as appropriate doping (Fe, Mn) we plan to tune the phase transitions in In2O3 under high-pressure (HP) and high-temperature (HT) conditions. In this way we aim to tune the electrical and optical properties of indium oxide as well as to simulate the HP behaviour of MgSiO3-rich minerals in the lower Earth's mantle providing therefore an input in the modelling of planetary interiors. The interdisciplinary studies include (i) sol-gel and hydrothermal synthesis of the shape- and size-controlled In2O3 polymorphs (bixbyite- and corundum-type) which will be used as precursors for the HP-HT synthesis in laser-heated diamond anvil cells (LH-DAC) and in multi anvil cells (MAC); (ii) search for the conditions of the phase transitions in In2O3 under HP-HT ( > 10 GPa, > 1000 K) in LH-DAC, (iii) synthesis of micro quantities of new In2O3 polymorphs in MAC, (iv) investigation of their thermal stability by in-situ heating XRD and Raman spectroscopy, (v) characterisation of their physical properties (band gap, charge carrier density, electron mobility) including also in situ characterisation at different temperatures and gas atmospheres (thermal and chemical stability, gas sensing properties). The proposal includes two key components: (i) complementary synthesis methodology (solgel and hydrothermal) which allows control over the phase composition as well as the size and the shape of In2O3, In(OH)3 and InOOH crystals which will be used as precursors for the HP synthesis. In addition In2O3, In(OH)3 and InOOH crystals will be doped with chosen (Fe, Mn) metal cations for the tunable / directed phase transitions as well as crystal growth; (ii) DFT-GGA computations on the estimation of possible phase transitions as well as transition pressures will be used for the rational design of the synthesis conditions.