The crystallization of (Pb, Yb, Er)F_x nano particles from glasses with the composition 20 SiO_2-13.5 B_2O_3-6 Al_2O_3-10 PbO-6.6 CdO 20 PbF_2-13.3 CdF_2.10YbF_3-0.5ErF_3

摘要

In glasses with the mol% composition 20 SiO_2-13.5 B_2O_3-6 Al_2O_3 - 10 PbO-6.6 CdO 20 PbF_213.3 CdF_2-10 YbF3-0.5 ErF_3-, annealing at temperatures in the range from 405 to 450 °C leads to the formation of (Pb, Yb, Er)F_x crystals. The mean crystallite size as determined by XRD-line broadening remains constant when the annealing time is increased. With increasing annealing temperature, the quantity of crystals formed gets larger while the size of the crystals increases slightly. The glass transition temperature of partially crystallized samples increased with increasing annealing time and approaches a value equal to the temperature, the samples were annealed. This was explained by the formation of a highly viscous layer formed during crystallization. This layer is enriched in SiO_2, acts as a diffusion barrier and hinders further crystal growth.