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Issue 25, 2014
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High pressure polymorphism of β-TaON

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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–Murnaghan equation of state fit for baddeleyite structured β-TaON indicates a high bulk modulus value Ko = 328 ± 4 GPa with Ko = 4.3. EXAFS analysis of the high pressure XAS data provides additional information on changes in the Ta–(O,N) and Ta–Ta 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.

Graphical abstract: High pressure polymorphism of β-TaON

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Publication details

The article was received on 18 Mar 2014, accepted on 08 May 2014 and first published on 08 May 2014

Article type: Paper
DOI: 10.1039/C4DT00805G
Author version available: Download Author version (PDF)
Citation: Dalton Trans., 2014,43, 9647-9654
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    High pressure polymorphism of β-TaON

    K. Woodhead, S. Pascarelli, A. L. Hector, R. Briggs, N. Alderman and P. F. McMillan, Dalton Trans., 2014, 43, 9647
    DOI: 10.1039/C4DT00805G

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