Structural and luminescent properties of crystalline microstructure in the GeO2-PbO-PbF2 glass-ceramics doped with luminescent ions

Transparent glass-ceramics containing β-PbF2:Ln3+ (Ln3+ = Er, Tm, Yb) crystallites were prepared by controlled nucleation of basic oxyfluoride glass with composition 50GeO2-(40 - x)PbO-10PbF2-xLnF3 (x = 0.2-5 mol%). The differential thermal analysis of as-melted samples provided thermal characteristics essential for individual controlled devitrification processes. Kinetics and optical techniques monitored the thermal treatment effect on the lanthanide coordination sphere. The X-ray powder diffraction technique (XRD) was used to confirm and to identify crystalline phases and to estimate average crystalline size. In the case of the Er3+ and Tm3+-doped specimens the presence of both the halo pattern (typical for an amorphous state) and the crystalline phase of β-PbF2:Ln was observed. The Yb-doped samples did not exhibit such XRD patterns. The thermal treatment effects on excited state relaxations of luminescent levels and the structure of optical bands were observed. Non-exponential decay curves of precursor samples became nearly exponential with longer lifetimes in glass-ceramics