Kinetic control in the synthesis of metastable polymorphs: Bixbyite-to-Rh{sub 2}O{sub 3}(II)-to-corundum transition in In{sub 2}O{sub 3}
- Freiberg High Pressure Research Centre, Institut für Anorganische Chemie, Technische Universität-Bergakademie Freiberg, Leipziger Straße 29, 09599 Freiberg (Germany)
- Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 760019-0065 (United States)
- Fachbereich Material -und Geowissenschaften, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt (Germany)
An example for kinetic control of a solid-state phase transformation, in which the system evolves via the path with the lowest activation barrier rather than ending in the thermodynamically most favorable state, has been demonstrated. As a case study, the phase transitions of indium sesquioxide (In{sub 2}O{sub 3}) have been guided by theoretical calculations and followed in situ under high-pressure high-temperature conditions in multi-anvil assemblies. The corundum-type rh-In{sub 2}O{sub 3} has been synthesized from stable bixbyite-type c-In{sub 2}O{sub 3} in two steps: first generating orthorhombic Rh{sub 2}O{sub 3}-II-type o′-In{sub 2}O{sub 3} which is thermodynamically stable at 8.5 GPa/850 °C and, thereafter, exploiting the preferred kinetics in the subsequent transformation to the rh-In{sub 2}O{sub 3} during decompression. This synthesis strategy of rh-In{sub 2}O{sub 3} was confirmed ex situ in a toroid-type high-pressure apparatus at 8 GPa and 1100 °C. The pressure–temperature phase diagrams have been constructed and the stability fields of In{sub 2}O{sub 3} polymorphs and the crystallographic relationship between them have been discussed. - Graphical abstract: In situ energy-dispersive XRD patterns in multi-anvil assemblies show the sequence of phase transition c-In{sub 2}O{sub 3}→o′-In{sub 2}O{sub 3}→rh-In{sub 2}O{sub 3} under particular pressure and temperature conditions. The tick marks refer to the calculated Bragg positions of bixbyite-type (c-In{sub 2}O{sub 3}), Rh{sub 2}O{sub 3}-II-type (o–-In2O{sub 3}) and corundum-type (rh-In{sub 2}O{sub 3}). - Highlights: • The solid-state synthesis methods can be employed for obtaining metastable phases. • The phase transition of In{sub 2}O{sub 3} was guided by DFT calculations. • The phase transition of In{sub 2}O{sub 3} was followed in situ under HP–HT conditions. • Orthorhombic o′-In{sub 2}O{sub 3} polymorph was synthesized from c-In{sub 2}O{sub 3} at 8.5 GPa/850 °C. • Metastable rh-In{sub 2}O{sub 3} was obtained from o′-In{sub 2}O{sub 3} at 5.5 GPa during decompression.
- OSTI ID:
- 22486775
- Journal Information:
- Journal of Solid State Chemistry, Vol. 229; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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