Abstract
The high pressure behaviors of the two perovskite structures (hexagonal 6H-SrIrO 3 and orthorhombic 3C-SrIrO 3) have been studied in diamond anvil cells to 43 and 60 GPa, respectively, using synchrotron powder X-ray diffraction. 6H-SrIrO 3 was first synthesized at ambient pressure and subsequently transformed into 3C-SrIrO 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 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 0=151.5(12) GPa (fitted range 0<P<30 GPa) for 6H-SrIrO 3 and K 0=187.1(9) GPa for 3C-SrIrO 3. Analysis of the structural parameters for 6H-SrIrO 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 3 becomes less compressible than 3C-SrIrO 3 above 32 GPa as a result of the mechanistic change, and a crossing of their P-V curves is avoided. For 3C-SrIrO 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.
Original language | English |
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Journal | Journal of Solid State Chemistry |
Volume | 238 |
Pages (from-to) | 74-82 |
Number of pages | 9 |
ISSN | 0022-4596 |
DOIs | |
Publication status | Published - Jun 2016 |
Keywords
- CAIRO3
- EQUATIONS
- FERROMAGNETISM
- High pressure
- MGSIO3
- NAMGF3 PEROVSKITE
- NEUTRON POWDER DIFFRACTION
- PHASE-TRANSITION
- Perovskite
- Polymorphism
- Post-perovskite
- SINGLE-CRYSTAL
- SRIRO3
- STATE
- SrlrO(3)