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Title: Coordination chemistry of Ti(IV) in silicate glasses and melts: II. Glasses at ambient temperature and pressure

Abstract

The coordination environment of Ti (IV) in a number of Ti-silicate and Ti-aluminosilicate glasses has been determined by x-ray absorption fine structure (XAFS) spectroscopy at the Ti K-edge at ambient temperature and pressure. These glasses contain 2.7-30.5 wt% TiO{sub 2} and varying amounts of Na{sub 2}O, K{sub 2}O, or CaO (5.0-38.7 wt%) and Al{sub 2}O{sub 3} (0-11.9 wt%), and have NBO/T ratios ranging from 0.07 - 0.81. Quantitative analysis of the Ti XANES spectra, based on ab initio multiple-scattering calculations for a variety of Ti-containing clusters. and anharmonic analysis of the normalized XAFS oscillations suggest the presence of three types of atoms around Ti: O first neighbors, (Si, Ti)-second neighbors, and alkali third neighbors. Five-coordinated Ti, {sup [5]}Ti, is the dominant Ti species in the glasses most concentrated in Ti ( > 16 wt% TiO{sub 2}) and is located in distorted square pyramids (({sup [5]}TiO) O{sub 4}), with one short Ti=O titanyl distance ( 1.67- 1.70 {+-} 0.03 {Angstrom}) and four long Ti-O distances ( 1.94-1.95 {+-} 0.02 {Angstrom}). In addition, minor amounts of {sup [4]}Ti were detected, the proportion of {sup [4]}Ti increasing in the order: Na glasses < K glasses. {sup [4]}Ti is the dominant Ti species inmore » the potassic glasses with the lowest TiO{sub 2} contents ({approx}3-6 wt%) and highest NBO/T ratio. The relative amount of {sup [4]}Ti increases in the order: Ca glass < K glass. Finally, {sup [6]}Ti is a minor species (<20%) when detected in these glasses. The presence of Ti-(Si, Ti) correlations near 3.2-3.4 {+-} 0.1 {Angstrom}, as in crystalline Na{sub 2}({sup [5]}TiO)SiO{sub 4}, is consistent with {sup [5]}TiO{sub 5} and SiO{sub 4}/TiO{sub 5} polyhedra sharing corners in these glasses, with Ti-O-(Si, Ti) angles of {approx}120{degrees}-130{degrees} {+-} 10{degrees}. These models also provide a structural basis for the study of glasses and melts at higher temperatures. 83 refs., 10 figs., 5 tabs.« less

Authors:
 [1];  [2];  [3];  [4]
  1. Universite de Marne-la-vallee, Grand (France)
  2. Stanford Univ., CA (United States)
  3. Princeton Univ., NJ (United States)
  4. Univ. of Washington, Seattle, WA (United States)
Publication Date:
OSTI Identifier:
476825
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta
Additional Journal Information:
Journal Volume: 60; Journal Issue: 16; Other Information: PBD: Aug 1996
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; SILICATES; CRYSTAL LATTICES; TITANIUM COMPOUNDS; STRUCTURAL CHEMICAL ANALYSIS; X-RAY SPECTROSCOPY; PHOSPHATE GLASS; VITRIFICATION

Citation Formats

Farges, F, Brown, Jr, G E, Navrotsky, A, and Rehr, J J. Coordination chemistry of Ti(IV) in silicate glasses and melts: II. Glasses at ambient temperature and pressure. United States: N. p., 1996. Web. doi:10.1016/0016-7037(96)00145-7.
Farges, F, Brown, Jr, G E, Navrotsky, A, & Rehr, J J. Coordination chemistry of Ti(IV) in silicate glasses and melts: II. Glasses at ambient temperature and pressure. United States. https://doi.org/10.1016/0016-7037(96)00145-7
Farges, F, Brown, Jr, G E, Navrotsky, A, and Rehr, J J. Thu . "Coordination chemistry of Ti(IV) in silicate glasses and melts: II. Glasses at ambient temperature and pressure". United States. https://doi.org/10.1016/0016-7037(96)00145-7.
@article{osti_476825,
title = {Coordination chemistry of Ti(IV) in silicate glasses and melts: II. Glasses at ambient temperature and pressure},
author = {Farges, F and Brown, Jr, G E and Navrotsky, A and Rehr, J J},
abstractNote = {The coordination environment of Ti (IV) in a number of Ti-silicate and Ti-aluminosilicate glasses has been determined by x-ray absorption fine structure (XAFS) spectroscopy at the Ti K-edge at ambient temperature and pressure. These glasses contain 2.7-30.5 wt% TiO{sub 2} and varying amounts of Na{sub 2}O, K{sub 2}O, or CaO (5.0-38.7 wt%) and Al{sub 2}O{sub 3} (0-11.9 wt%), and have NBO/T ratios ranging from 0.07 - 0.81. Quantitative analysis of the Ti XANES spectra, based on ab initio multiple-scattering calculations for a variety of Ti-containing clusters. and anharmonic analysis of the normalized XAFS oscillations suggest the presence of three types of atoms around Ti: O first neighbors, (Si, Ti)-second neighbors, and alkali third neighbors. Five-coordinated Ti, {sup [5]}Ti, is the dominant Ti species in the glasses most concentrated in Ti ( > 16 wt% TiO{sub 2}) and is located in distorted square pyramids (({sup [5]}TiO) O{sub 4}), with one short Ti=O titanyl distance ( 1.67- 1.70 {+-} 0.03 {Angstrom}) and four long Ti-O distances ( 1.94-1.95 {+-} 0.02 {Angstrom}). In addition, minor amounts of {sup [4]}Ti were detected, the proportion of {sup [4]}Ti increasing in the order: Na glasses < K glasses. {sup [4]}Ti is the dominant Ti species in the potassic glasses with the lowest TiO{sub 2} contents ({approx}3-6 wt%) and highest NBO/T ratio. The relative amount of {sup [4]}Ti increases in the order: Ca glass < K glass. Finally, {sup [6]}Ti is a minor species (<20%) when detected in these glasses. The presence of Ti-(Si, Ti) correlations near 3.2-3.4 {+-} 0.1 {Angstrom}, as in crystalline Na{sub 2}({sup [5]}TiO)SiO{sub 4}, is consistent with {sup [5]}TiO{sub 5} and SiO{sub 4}/TiO{sub 5} polyhedra sharing corners in these glasses, with Ti-O-(Si, Ti) angles of {approx}120{degrees}-130{degrees} {+-} 10{degrees}. These models also provide a structural basis for the study of glasses and melts at higher temperatures. 83 refs., 10 figs., 5 tabs.},
doi = {10.1016/0016-7037(96)00145-7},
url = {https://www.osti.gov/biblio/476825}, journal = {Geochimica et Cosmochimica Acta},
number = 16,
volume = 60,
place = {United States},
year = {1996},
month = {8}
}