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High pressure polymorphism of Beta-TaON

DOI: 10.1039/c4dt00805g DOI Help

Authors: Katherine Woodhead (University College London) , S. Pascarelli (European Synchrotron Radiation Facility) , Andrew Hector (University of Southampton) , Richard Briggs (University of Edinburgh) , N. Alderman (University of Southampton) , Paul Mcmillan (University College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Dalton Transactions , VOL 43 (25) , PAGES 7726-7733

State: Published (Approved)
Published: May 2014

Abstract: The high pressure behavior of TaON was studied using a combination of Raman scattering, synchrotron X-ray diffraction, and X-ray absorption spectroscopy in diamond anvil cells to 70 GPa at ambient temperature. A Birch¨CMurnaghan equation of state fit for baddeleyite structured ¦Â-TaON indicates a high bulk modulus value Ko = 328 ¡À 4 GPa with K¡äo = 4.3. EXAFS analysis of the high pressure XAS data provides additional information on changes in the Ta¨C(O,N) and Ta¨CTa distances. Changes in the X-ray diffraction patterns and Raman spectra indicate onset of a pressure induced phase transition near 33 GPa. Our analysis indicates that the new phase has an orthorhombic cotunnite-type structure but that the phase transition may not be complete even by 70 GPa. Similar sluggish transformation kinetics are observed for the isostructural ZrO2 phase. Analysis of compressibility data for the new cotunnite-type TaON phase indicate a very high bulk modulus Ko 370 GPa, close to the theoretically predicted value.

Subject Areas: Materials, Chemistry

Instruments: B18-Core EXAFS , I15-Extreme Conditions

Other Facilities: ID24 at ESRF

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