中国物理B ›› 2026, Vol. 35 ›› Issue (5): 56102-056102.doi: 10.1088/1674-1056/ae3606

所属专题： SPECIAL TOPIC — John Tse: Pioneer in high-pressure materials science

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Free oxide ion abundances in Na, Ba, and K silicate glasses from O 1s XPS, 29Si NMR, Raman, and MD simulations

G. Michael Bancroft1,†, H. Wayne Nesbitt2, John S. Tse3, Grant S. Henderson4, and Ben J. A. Moulton5   

  1. 1 Department of Chemistry, University of Western Ontario, London, ON N6A 5B7 Canada;
    2 Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7 Canada;
    3 Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, SASK S7N 5E2 Canada;
    4 Department of Earth Sciences, University of Toronto, Toronto, ON M5S 3B1 Canada;
    5 Inamori School of Engineering, New York College of Ceramics, Alfred University, Alfred, New York 14802 USA
  • 收稿日期:2025-10-23 修回日期:2026-01-06 接受日期:2026-01-09 出版日期:2026-04-24 发布日期:2026-05-11
  • 通讯作者: G. Michael Bancroft E-mail:gmbancro@uwo.ca
  • 基金资助:
    We are very pleased to help celebrate the many outstanding research accomplishments (in many scientific disciplines) of our colleague John Tse over the last 50 years, including close to 50 joint publications and his calculations in this paper. We thank our respective departments and universities for logistical support required to conduct this study. JST acknowledges computational facilities provided by the Argonne Leadership Computing Facility (ALCF) and the Fugaku computer system at RIKEN, Japan. We also thank the solid-state NMR spectroscopists, Profs. H. Eckert and Y. Huang, for their confirmation that higher magnetic fields do not improve the 29Si resolution of silicate glasses.

Free oxide ion abundances in Na, Ba, and K silicate glasses from O 1s XPS, 29Si NMR, Raman, and MD simulations

G. Michael Bancroft1,†, H. Wayne Nesbitt2, John S. Tse3, Grant S. Henderson4, and Ben J. A. Moulton5   

  1. 1 Department of Chemistry, University of Western Ontario, London, ON N6A 5B7 Canada;
    2 Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7 Canada;
    3 Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, SASK S7N 5E2 Canada;
    4 Department of Earth Sciences, University of Toronto, Toronto, ON M5S 3B1 Canada;
    5 Inamori School of Engineering, New York College of Ceramics, Alfred University, Alfred, New York 14802 USA
  • Received:2025-10-23 Revised:2026-01-06 Accepted:2026-01-09 Online:2026-04-24 Published:2026-05-11
  • Contact: G. Michael Bancroft E-mail:gmbancro@uwo.ca
  • Supported by:
    We are very pleased to help celebrate the many outstanding research accomplishments (in many scientific disciplines) of our colleague John Tse over the last 50 years, including close to 50 joint publications and his calculations in this paper. We thank our respective departments and universities for logistical support required to conduct this study. JST acknowledges computational facilities provided by the Argonne Leadership Computing Facility (ALCF) and the Fugaku computer system at RIKEN, Japan. We also thank the solid-state NMR spectroscopists, Profs. H. Eckert and Y. Huang, for their confirmation that higher magnetic fields do not improve the 29Si resolution of silicate glasses.

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摘要： In alkali silicate glasses with $\le 50$ mol%$M_{2}$O ($M={\rm Na}$, K, Rb, Cs), the existence of $>1$ mol%reactive "free" oxide (FO, where O is not bonded to Si) has been a highly controversial topic over the past 15 years. Unlike their crystalline analogues, Raman and $^{29}$Si nuclear magnetic resonance (NMR) studies since 1980 have shown that two or more $Q^{n}$ ($n=$0-4) species are present in silicate glasses over a wide range of compositions. For example, $M_{2}$SiO$_{3}$ crystals contain only $Q^{2}$ species; however, glasses of the same composition exhibit $Q^{1}$ and $Q^{3}$ in addition to $Q^{2}$. Previous Raman and NMR studies on alkali silicate glasses have related the abundances of these three species solely through disproportionation reactions (e.g. $2{ Q}^{2}\Leftrightarrow { Q}^{1}+{ Q}^{3}$). In doing so, polymerization reactions (e.g. $2{ Q}^{2}\Leftrightarrow 2{ Q}^{3}+{\rm FO}$) were completely neglected. By combining published O 1s x-ray photoelectron spectroscopy (XPS) spectra, $^{29}$Si NMR and Raman results for 40 mol%and 50 mol%Na$_{2}$O, K$_{2}$O, and BaO glasses, together with new molecular dynamics (MD) simulations of Na$_{4}$SiO$_{4}$ glass, we provide consistent and compelling evidence for the existence of $>1$ mol%FO in these glasses and melts. In particular, for 50 mol%K$_{2}$O silicate glass, all three experimental techniques estimate FO to be $\ge 7$ mol%, while MD simulations of Na$_{4}$SiO$_{4}$ yield $\sim 5$ mol%FO. Our analysis requires revised assignments (challenging decades of "conventional wisdom") for $^{29}$Si NMR and Raman spectra, based on O mass balance, recognition of M-BO bonding effects first identified in O 1s XPS spectra, and quantitative analysis of Raman spectra for 40-50 mol%Na$_{2}$O, K$_{2}$O, and BaO glasses. These FO values are comparable to those now accepted for alkaline-earth silicate glasses. The importance of this reactive FO for chemical reactivity (e.g. with H$_{2}$O and CO$_{2}$), bioactivity, and physical properties (e.g. melting) of silicate glasses is discussed.

关键词: alkali silicate glasses, free oxide (Na-O-Na), O 1s XPS, Raman, $^{{29}}$Si NMR

Abstract: In alkali silicate glasses with $\le 50$ mol%$M_{2}$O ($M={\rm Na}$, K, Rb, Cs), the existence of $>1$ mol%reactive "free" oxide (FO, where O is not bonded to Si) has been a highly controversial topic over the past 15 years. Unlike their crystalline analogues, Raman and $^{29}$Si nuclear magnetic resonance (NMR) studies since 1980 have shown that two or more $Q^{n}$ ($n=$0-4) species are present in silicate glasses over a wide range of compositions. For example, $M_{2}$SiO$_{3}$ crystals contain only $Q^{2}$ species; however, glasses of the same composition exhibit $Q^{1}$ and $Q^{3}$ in addition to $Q^{2}$. Previous Raman and NMR studies on alkali silicate glasses have related the abundances of these three species solely through disproportionation reactions (e.g. $2{ Q}^{2}\Leftrightarrow { Q}^{1}+{ Q}^{3}$). In doing so, polymerization reactions (e.g. $2{ Q}^{2}\Leftrightarrow 2{ Q}^{3}+{\rm FO}$) were completely neglected. By combining published O 1s x-ray photoelectron spectroscopy (XPS) spectra, $^{29}$Si NMR and Raman results for 40 mol%and 50 mol%Na$_{2}$O, K$_{2}$O, and BaO glasses, together with new molecular dynamics (MD) simulations of Na$_{4}$SiO$_{4}$ glass, we provide consistent and compelling evidence for the existence of $>1$ mol%FO in these glasses and melts. In particular, for 50 mol%K$_{2}$O silicate glass, all three experimental techniques estimate FO to be $\ge 7$ mol%, while MD simulations of Na$_{4}$SiO$_{4}$ yield $\sim 5$ mol%FO. Our analysis requires revised assignments (challenging decades of "conventional wisdom") for $^{29}$Si NMR and Raman spectra, based on O mass balance, recognition of M-BO bonding effects first identified in O 1s XPS spectra, and quantitative analysis of Raman spectra for 40-50 mol%Na$_{2}$O, K$_{2}$O, and BaO glasses. These FO values are comparable to those now accepted for alkaline-earth silicate glasses. The importance of this reactive FO for chemical reactivity (e.g. with H$_{2}$O and CO$_{2}$), bioactivity, and physical properties (e.g. melting) of silicate glasses is discussed.

Key words: alkali silicate glasses, free oxide (Na-O-Na), O 1s XPS, Raman, $^{{29}}$Si NMR

中图分类号:  (Glasses)

  • 61.43.Fs
79.60.-i (Photoemission and photoelectron spectra) 76.60.-k (Nuclear magnetic resonance and relaxation) 78.30.-j (Infrared and Raman spectra)