Pressure-induced Structural Transitions and Phase Decomposition in Cd2Nb2O7 Pyrochlore
Journal Article
·
· Physical Review B
- University of Michigan
- ORNL
- National Synchrotron Light Source (NSLS)
- Florida International University, Miami
The structural transitions of the pyrochlore, Cd{sub 2}Nb{sub 2}O{sub 7}, at pressures up to 32.5 GPa have been investigated by in situ Raman scattering and angle-dispersive x-ray diffraction (ADXRD) methods. The x-ray diffraction results reveal that small amounts ({approx}7%) of metallic cadmium form by chemical decomposition at pressures greater than 4 GPa. Both Raman and XRD results indicate that a pressure-induced structural distortion from pyrochlore to defect fluorite occurs in pyrochlore Cd{sub 2}Nb{sub 2}O{sub 7} at pressures of 12-14 GPa. Subsequently, a new high-pressure phase formed and the phase transition was complete at {approx}27 GPa. The high-pressure phase is either monoclinic or orthorhombic and transforms to either the pyrochlore (or defect fluorite) structure or the amorphous state when quenched to ambient conditions. Energy dispersive spectroscopy (EDS) analysis and high-resolution transmission electron microscopy (HRTEM) observation of the quenched sample confirmed the Cd loss and resulting mixture of ordered pyrochlore, defect fluorite, high-pressure phase, as well as amorphous domains.
- Research Organization:
- Oak Ridge National Laboratory (ORNL)
- Sponsoring Organization:
- ORNL work for others
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 979582
- Journal Information:
- Physical Review B, Journal Name: Physical Review B Journal Issue: 17 Vol. 74; ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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