MICROHARDNESS OF PHOSPHATE-GLASSES

Vickers microhardness values of some binary and ternary phosphate glasses were determined. An increase of Vickers hardness was obtained on addition of a second alkali oxide (Li2O or K2O) or a divalent oxide (CaO or ZnO) to a sodium phosphate glass. The microhardness values were also seen to be a function of the applied load. Results are discussed in relation to the possible flow mechanism in the glass during indentation, together with the role of mixed alkali. The data are also correlated to polarization, field strength and ionic radii of the incorporated cations and their effects on the geometrical arrangement of the building units in the glassy network.