The Annealing Process And Up-conversion Properties Of Rare-earth Doped Glass Ceramics

In recent years, rare earth doped SiO₂-PbF₂ up-conversion optical oxyfluoride glass ceramics have attracted much more attention owing to their lower phonon energy environment of heavy metal fluoride crystal and the better mechanical, thermal stability of oxide glasses. A large number of studies show that up-conversion sensitization mechanism is an effective mechanism to increase the intensity of luminescence. In this dissertation, Yb³⁺ ions as sensitizers,the Tm³⁺/Yb³⁺and Ho³⁺/Yb³⁺ codoped 50SiO₂-50PbF₂ glass and glass ceramics samples were prepared by high temperature sintering method. We had studied their optical properties, J-O parameters, and the change of micro-structure during the annealing process.(1) In 50SiO₂-50PbF₂-1YbF₃-xTmF₃ glass sample, XRD patterns showedβ-PbF₂ microcrystals had produced after annealing. Through calculation we found the lattice constant was 5.74 ?, and the size of microcrystal was about 14 nm. The quench concentrations were 0.05 mol% in glasses and 0.02 mol% in glass ceramics respectively. The glass ceramic with lower Tm³⁺ ions concertration (0.02 mol%) has intense blue and ultraviolet up-conversion luminescence.(2) 50SiO₂-50PbF₂-1YbF₃-0.5HoF₃ glass ceramic has intense green up-conversion luminescence. The value of Judd-Ofelt parameter ?2 of Ho³⁺ ions in glass ceramic is 0.17×10-20cm².(3) The resistance of glass (50SiO₂-50PbF₂-1YbF₃-0.5HoF₃) was measured by data acquisition equipment during the annealing process. At the setted temperature (440℃), we found that the microcrystals were formed after 163 s and the microcrystals were growing up with increasing the time. As inceasing the time up to 600 s, the growth process of the microcrystals were tended to a stable status.