Inorganic glasses and glass-ceramics studied by isothermal mechanical spectroscopy

This paper describes isothermal mechanical spectroscopy measurements carried out in silicate glasses and LAS (Li2O–Al2O3–SiO2)-type glass-ceramics. alkali silicate glass Na2O·3SiO2 exhibits two relaxation peaks. The first one located at a low temperature is generally assigned to the stress-induced diffusion of alkali ions. The second relaxation peak is attributed to the “non-bridging oxygen”. Mixed alkali silicate glasses (1 − x)Na2O·xLi2O·3SiO2 with x = 0, 0.25, 0.5, 0.75 exhibit the mixed alkali peak. And also the “non-bridging oxygen” peak. Two LAS-type glass-ceramics having the same chemical composition but different microstructures: “β-quartz” and “β-spodumene” type, respectively, and their parent glass have been studied. For the glass which does not contain “non-bridging oxygen”, a single mechanical relaxation peak linked with the stress-induced movement of lithium ions is observed. On the contrary, two peaks occur in the “β-quartz” and “β-spodumene” glass-ceramics. The “low-temperature” peak (∼340 K for 1 Hz) is linked with ion mobility in the respective main crystalline phase. The origin of the “high-temperature” peak is totally different for the two glass-ceramics; in the “β-quartz” glass-ceramic, it is due to Mg2+ and Zn2+ ion relaxation in the crystalline phase, whereas in the “β-spodumene” glass-ceramic, it is linked with a complex entity within the residual vitreous phase.