Atomic structure and strength of inorganic glasses

Abstract

The role of the atomic structure in the fracture processes is considered using borate, silicate, and phosphate glasses as an example. Primary attention is focused on the degree of connectivity of the atomic structure. It is shown that the degree of connectivity is a major factor responsible for the structural strength of glasses under conditions excluding the influence of both accidental surface defects and the environment. The change in the Young’s modulus as a measure of elastic deformation and the change in the hardness as a characteristic of irreversible deformation are analyzed. The ultimate elastic strain experienced by a glass at the instant of fracture is examined. It is found that the ultimate elastic strain is approximately equal to 10% for glasses with a three-dimensional atomic structure and 5% for glasses with a two-dimensional (layered) or chain structure. It is assumed that this behavior of the strength as a function of the degree of connectivity of the atomic structure is associated with the degree of uniformity of the external load distribution over atomic bonds.