Effect of annealing close to Tg on the short-range order of lithium disilicate glass

Abstract

Annealing of glasses at temperatures close to Tg is a usual procedure to reduce internal stresses induced by the conventional melting/quenching process. In this work, the effect of the annealing temperature and time on short-range order of lithium disilicate glass was investigated. The total structure factor and radial distribution function of annealed samples at distinct temperatures and times were derived from synchrotron XRD measurements. The results suggest that short and medium range-orders were affected by the annealing conditions, even for temperatures well below the glass transition temperature, Tg. After annealing at temperatures close to Tg, local arrangements were identified with those corresponding to crystalline phases of lithium disilicate and lithium metasilicate. For temperatures below Tg, the diffusion of lithium atoms was already taking place, while the rearrangements of the SiO4 tetrahedra from the network former started to happen for temperatures close to or higher than Tg.