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

The present study investigates the boron and aluminium speciation of aluminoborosilicate glasses synthesized under ambient to high-pressure conditions (up to 2.0 GPa) using 11 B and 27 Al Nuclear Magnetic Resonance.Four glass series were prepared in the SiO2-Al2O3-B2O3-Na2O/CaO system, with either high or low R' values (R'=(11 B 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 nonbridging oxygen (NBO) variation witnesses the change in compensation mechanism for boron species.In low R' glasses, limited NBOs suggest Na + /Ca 2+ 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.