NMR Studies of Permanent Compression in Oxide Glasses: Invited Talk

Pressure-induced structural rearrangement in oxide glasses is manifested by modification of both short- and intermediate-range structures, including changes to the local coordination numbers of network forming cations and alteration of the modifier environment. NMR spectroscopy is an especially useful tool for examining these changes in network structure, especially for boron-containing glasses, which are particularly sensitive to permanent compression. Here we describe studies based on hot isostatic compression of several different borate and borosilicate glasses, where changes in short-range structure following both compression and thermal annealing (relaxation) treatments have been examined using solid-state NMR. Changes in boron coordination, arrangement of these polyhedra into various superstructural groups, as well as the impact of compression and annealing on the local geometry of the network modifying sodium atoms, will be discussed. Such changes in network structure aid in understanding the pressure-induced properties of these glasses, such as density, elastic moduli, hardness and crack resistance.