Effects of alkali and alkaline-earth cations on the high-pressure sound velocities of aluminosilicate glasses

The sound velocities (compressional wave velocity [ V P ] and shear wave velocity [ V S ]) of four types of aluminosilicate glasses (Mg 3 Al 2 Si 6 O 18 (MAS), Ca 3 Al 2 Si 6 O 18 (CAS), Na 3 AlSi 3 O 9 (NAS), and K 3 AlSi 3 O 9 (KAS)) are measured using the ultrasonic technique at high pressures of up to 7.8 GPa. The V P and V S of MAS glass decrease up to a pressure of 2 GPa and subsequently increase with increasing pressure. The pressure dependence of the CAS glass velocities changes; V P remains almost constant when P ≤ 2 GPa and subsequently increases above 2 GPa. The minimum V S can be observed at approximately 2 GPa, which is similar to that in the case of the MAS glass. The sound velocities of the NAS and KAS glasses monotonically increase with pressure. The increments in the V P and V S of the KAS glass show less sensitivity when compared with that observed in the case of the NAS glass within the pressure range of our experiments. The differences in the properties of the modifying cations in the glasses, such as size ( [5] Mg 2+