Relaxations in Li2O-Al2O3-SiO2-type glass and glass-ceramics studied by isothermal mechanical spectroscopy

The aim of this work is to describe and discuss internal friction data from LAS based glass and glass-ceramics with identical composition. The internal friction measurements were performed by isothermal mechanical spectroscopy. In order to obtain further information and to interpret mechanical damping measurements, dielectric relaxation experiments were also carried out on these materials. In totally vitreous material, internal friction spectra show a single low-temperature peak (at 276+/-2 K for 1 Hz) assigned to the stress-induced motion of lithium-ions. This peak is not observed in glass-ceramics. However, two other peaks occur in these materials. The first one (at about 343 K for 1 Hz), also obtained by dielectric measurements, is probably linked with the Li+-ion mobility inside the crystal-phase. The second one occurs at higher temperature (between 600 K and 700 K for 1 Hz); its origin is more uncertain, and the relaxation parameters are dependent on the microstructure of the glass-ceramic.