Metastability of corundum-type In2O3
Aleksander Gurlo1, Peter Kroll, Ralf Riedel
1Fachbereich Material- und Geowissenschaften, Technische Universitaet Darmstadt, Petersenstrasse 23, Darmstadt, Germany. gurlo@materials.tu-darmstadt.de
Chemistry (Weinheim an Der Bergstrasse, Germany)
|February 14, 2008
Summary
The corundum-type indium oxide (In2O3) polymorph is metastable, transforming to bixbyite-type In2O3 upon heating. Theoretical calculations also predict a new orthorhombic In2O3 phase at high pressures.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Bixbyite and corundum structures are commonly observed crystal structures.
- The transition between bixbyite and corundum structures is relevant to materials synthesis.
- The stability of corundum-type indium oxide (In2O3) requires clarification for phase diagram interpretation.
Purpose of the Study:
- To investigate the stability of corundum-type In2O3.
- To clarify phase transitions in In2O3 under varying conditions.
- To re-interpret the In-O phase diagram based on new findings.
Main Methods:
- Theoretical study using density-functional calculations.
- Experimental synthesis via a modified non-alkoxide sol-gel method.
- Thermal analysis (STA) and in situ X-ray powder diffraction (XRPD) upon thermal treatment.
Main Results:
- Demonstrated the metastability of corundum-type In2O3 polymorph both theoretically and experimentally.
- Observed irreversible transformation of corundum-type In2O3 to bixbyite-type In2O3 upon heating.
- Predicted a new orthorhombic In2O3 phase (iso-typic to Rh2O3-II) forming above 15 GPa.
Conclusions:
- Corundum-type In2O3 is metastable across the entire enthalpy-pressure phase diagram.
- Heating induces an irreversible phase transition from corundum-type to bixbyite-type In2O3.
- A novel high-pressure orthorhombic In2O3 phase is theoretically predicted.
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