To estimate the ratio of densification to Vickers indentation volume, three-dimensional images of Vickers indentations on several glasses, including silicate glasses and bulk metallic glass (BMG), were obtained before and after annealing using an atomic force microscope. Large volume recovery of Vickers indentation by annealing was observed for all glasses but BMG. Following previous studies, this recovered volume almost corresponded to the densified volume under a Vickers indenter, and the compositional dependence of densification was discussed. The ratios of densification to the total indentation volume for silica and soda-lime glasses were 92% and 61%, respectively. It was concluded that densification was a general property for silicate glasses and that the ratios of densification to the total indentation volume for all the glasses correlated well with Poisson’s ratios of the glasses.

Ge-Se chalcogenide glasses are characterized by relatively low hardness (0.39 -2.35 GPa) and low fracture toughness (0.1-0.28 MPa⅐m 1/2 ). Actually, the hardness of chalcogenrich glasses is low enough so that the brittleness parameter, B ‫؍‬ H/K c , is lower than that of silicate glasses. Whereas hardness and Young's modulus increase with increasing germanium contents, fracture toughness follows a trend similar to that of the density and exhibits a maximum for the Ge 20 Se 80 composition, which corresponds to the rigidity percolation threshold. Optical microscopy and atomic force microscopy observations suggest that the indentation deformation proceeds by a localized shear deformation phenomenon. Glasses in the chalcogen-rich region behave viscoelastically at room temperature. As a consequence, an increase of the loading time results in a decrease of hardness and toughness.

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