High pressure structure studies of 6H-SrIrO{sub 3} and the octahedral tilting in 3C-SrIrO{sub 3} towards a post-perovskite

Journal Article · Wed Jun 15 00:00:00 EDT 2016 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2016.03.012· OSTI ID:22584106

Kronbo, Camilla H.; Nielsen, Morten B.; Kevy, Simone M. ^[1]; Parisiades, Paraskevas ^[2]; Bremholm, Martin ^[1]

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1. Center for Materials Crystallography (CMC), Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, 8000 Aarhus C (Denmark)
2. ID27 Beamline, European Synchrotron Radiation Facility, 71 Avenue des Martyrs, 38043 Grenoble (France)

The high pressure behaviors of the two perovskite structures (hexagonal 6H-SrIrO{sub 3} and orthorhombic 3C-SrIrO{sub 3}) have been studied in diamond anvil cells to 43 and 60 GPa, respectively, using synchrotron powder X-ray diffraction. 6H-SrIrO{sub 3} was first synthesized at ambient pressure and subsequently transformed into 3C-SrIrO{sub 3} in a large volume press at 8.8 GPa and 1000 °C. Both polymorphs were found to retain the initial symmetry up to the highest pressures measured, but in the case of 6H-SrIrO{sub 3}, two anomalies were identified: a change in the axial compressibilities at 24 GPa and a change in both the axial and volume compressibilities at 32 GPa. Fitting a 3rd order Birch-Murnaghan equation of state to the obtained P-V data yielded bulk moduli of K{sub 0}=151.5(12) GPa (fitted range 0<30 GPa) for 6H-SrIrO{sub 3} and K{sub 0}=187.1(9) GPa for 3C-SrIrO{sub 3}. Analysis of the structural parameters for 6H-SrIrO{sub 3} aided by F-f plots suggests the anomalies are caused by changes in the compression mechanism. Comparison of the two polymorphs reveals that 6H-SrIrO{sub 3} becomes less compressible than 3C-SrIrO{sub 3} above 32 GPa as a result of the mechanistic change, and a crossing of their P-V curves is avoided. For 3C-SrIrO{sub 3}, analysis of the octahedral tilt angles shows that these increase monotonically from the ambient value of 7.23(6) to 23.0(2)° at 60 GPa suggesting that a transition to a post-perovskite is approached. - Graphical abstract: The structure of 3C-SrIrO{sub 3} synthesized at high pressure has been studied in a diamond anvil cell and is found to maintain its orthorhombic structure up to 60 GPa but distorts drastically due to octahedral tilting, strongly suggesting that a post-perovskite transition is possible. The compression is compared to 6H-SrIrO{sub 3} synthesized at ambient pressure, which is initially found to be more compressible but undergoes changes in its compression mechanism and 3C remains denser throughout compression. Display Omitted - Highlights: • Structures of 6H- and 3C-SrIrO{sub 3} were studied to pressures of 43 and 60 GPa, respectively. • Both structures maintain the initial symmetry up to the highest pressures measured. • 6H-SrIrO{sub 3} is initially more compressible than 3C-SrIrO{sub 3}. • Due to changes in the compression mechanism in 6H-SrIrO{sub 3} the 3C-SrIrO{sub 3} remains denser throughout. • 3C-SrIrO{sub 3} show large octahedral tilting, strongly suggesting a post-perovskite transition is imminent.

• OSTI ID: 22584106
• Journal Information: Journal of Solid State Chemistry, Vol. 238; Other Information: Copyright (c) 2016 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

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
COMPARATIVE EVALUATIONS
COMPRESSIBILITY
COMPRESSION
EQUATIONS OF STATE
IRIDIUM OXIDES
ORTHORHOMBIC LATTICES
PEROVSKITE
POWDERS
PRESSES
PRESSURE RANGE GIGA PA
PRESSURE RANGE MEGA PA 10-100
STRONTIUM COMPLEXES
X RADIATION
X-RAY DIFFRACTION