Physics and Chemistry of Minerals

, Volume 21, Issue 8, pp 510-515

First online:

Pressure-induced coordination change of Ti in silicate glass: a XANES study

  • E. ParisAffiliated withDipartimento di Scienze della Terra, Universita' di Camerino
  • , D. B. DingwellAffiliated withBayerisches Geoinstitut, Universität Bayreuth
  • , F. A. SeifertAffiliated withBayerisches Geoinstitut, Universität Bayreuth
  • , A. MottanaAffiliated withDipartimento di Scienze Geologiche, Terza Universita' di Roma
  • , C. RomanoAffiliated withBayerisches Geoinstitut, Universität Bayreuth

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The effect of pressure on titanium coordination in glasses, with composition K2TiSi4O11, quenched isobarically from liquids equilibrated at high pressure (5, 10, 15, 20, 25, 30 kbar respectively) and T=1600° C has been investigated by X-ray absorption spectroscopy (XAS). The XANES spectra collected at the Ti K-edge clearly show a variation with pressure that is related to changes in the geometrical environment around the Ti atoms. By comparison with spectra of standard materials, the XANES spectra of the glasses suggest a relatively low average coordination number (near 5) in samples quenched at low pressure and a higher coordination number (near 6) in samples quenched from the highest pressure. The combination of XANES data with density and compressibility measurements supports the idea that a mixture of 6- and lower coordinated (4- and/ or 5-coordinated) Ti geometries are present in the 1 bar glass, and an increasing proportion of 6-coordinated Ti occurs in the glasses synthesized at progressively higher pressures.