Correlation of the Vickers hardness of RO–Al₂O₃–SiO₂ glasses with predicted liquidus temperatures

Abstract

Vickers hardnesses of RO–Al2O3–SiO2 glasses were measured over a broad range of compositions, ranging from ternary endpoints to mixed ratios of RO (CaO with MgO, SrO, or BaO), with the systematic variation of Al2O3 and SiO2 levels. The hardnesses of CAS and MAS glasses are similar, ranging from 6.7 to 7.2 GPa, with the replacement of CaO with MgO producing a marginal increase in hardness. The substitution of SrO or BaO for CaO generally produced in a decrease in hardness down to 4.5 GPa with BaO. The sensitivity to alumina and silica levels, however, was much greater ranging from a minimum of 4.5 GPa to a maximum of ∼8.2 GPa. The correlation of the Vickers hardness with melting temperature was observed in the CAS system but generally not in the RO‐blended glasses. Overall, a combined cation field strength of modifier cations determined the hardness above the critical RO blending ratio.