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

• Antragsteller: Professor Dr. Aleksander Gurlo; Professor Dr. Hans-Joachim Kleebe
• Fachliche Zuordnung: Mineralogie, Petrologie und Geochemie
• Förderung: Förderung von 2009 bis 2014
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 140391539

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.

• DFG-Verfahren: Schwerpunktprogramme
• Teilprojekt zu: SPP 1236: Strukturen und Eigenschaften von Kristallen bei extrem hohen Drücken und Temperaturen
• Beteiligte Person: Professor Ralf Riedel