Influence of high-pressure on the short-range structure of Ca or Na aluminoborosilicate glasses from 11B and 27Al solid-state NMR

• Published in: Journal of non-crystalline solids 2024-08, Vol.638, p.123085, Article 123085
• Main Authors: Soudani, Sami, Paris, Michael, Morizet, Yann
• Format: Article
• Language: English
• Subjects: Aluminoborosilicate; Chemical Sciences; Coordination; Glass; High-pressure; Inorganic chemistry; Material chemistry; NBO; NMR
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2024.123085

•11B NMR revealed a non-linear increase of the boron coordination in Na-bearing samples, where Ca-bearing ones display a linear evolution.•27Al NMR shows negligible pressure dependence on aluminium coordination (AlO4) in Na glasses. In contrast, Ca glasses exhibit pressure-induced formation of higher-coordinated AlO5 and AlO6 units.•Low R' (([Na2O]+[CaO])/([B2O3]+[Al2O3])) glasses have limited NBOs available for charge compensation. Therefore, the primary source is likely Na+ or Ca2+ cations released from the transformation of AlO4 units. The present study investigates the boron and aluminium speciation of aluminoborosilicate glasses synthesised under ambient to high-pressure conditions (up to 2.0 GPa) using 11B and 27Al Nuclear Magnetic Resonance. Four glass series were prepared in the SiO2-Al2O3-B2O3-Na2O/CaO system, with either high or low R' values (R'=([Na2O]+[CaO])/([B2O3]+[Al2O3])). 11B NMR reveals a linear increase in four-coordinated boron (BO4) with pressure for Ca glasses and non-linear with a plateau between 0.5 and 1.5 GPa for Na glasses. 27Al NMR reveals minimal pressure impact on aluminium coordination in sodium glasses. Conversely, calcium glasses form higher-coordinated AlO5 and AlO6 units under pressure. The determination of non-bridging oxygen (NBO) variation witnesses the change in compensation mechanism for boron species. In low R' glasses, limited NBOs suggest Na+/Ca2+ release from AlO4 as the primary compensation source. This work sheds light on pressure's influence on network connectivity in simple glasses, aiding the understanding of complex glass behaviour.