Study On Preparation And Upconversion Properties Of BaO-WO₃-SiO₂ System Glass Ceramics

Re/Yb co-doped BaO-WO₃-SiO₂ system glass ceramic（Re=（Er,Tb,Ho））were prepared by melt crystallization method in this paper.By the means of differential scanning calorimetry（DSC）,the optimum heat treatment schedules of Er³⁺/Yb³⁺,Tb³⁺/Yb³⁺,Ho³⁺/Yb³⁺co-doped BaO-WO₃-Si O₂ system glass ceramic were determined to be maintaining 120 min at 610 ℃,maintaining 90 min at 630 ℃,and maintaining 90 min at 610 ℃,respectively.The samples were measured by the X-ray diffraction analysis（XRD）,the results showed that the main crystal phase is always BaWO4（JCPDS: 43-0646）and the change of heat treatment time has not changed the species of crystal.The samples were measured by the scanning electron microscope（SEM）,the results showed that the size of the crystal particles become larger,the distributions become more uniform and the size of Er³⁺/Yb³⁺,Tb³⁺/Yb³⁺,Ho³⁺/Yb³⁺co-doped BaO-WO₃-SiO₂ system glass ceramic crystal particles were about 0.3-0.5μm,0.5-1.0μm,0.5-1.0μm with the increasing of heat treatment time.The transmittance of samples were measured by the UV-vis spectrophotometer,the results showed that the transmittance of the sample were gradually decreased with the increasing of heat treatment time.In the visible region,the transmittance of Er³⁺/Yb³⁺,Tb³⁺/Yb³⁺,Ho³⁺/Yb³⁺co-doped BaO-WO₃-SiO₂ system glass ceramics were 78%,79%,76%.The energy conversion between Yb³⁺ and Re³⁺ was found by the up conversion fluorescence spectra of the glass ceramics with different concentration of Yb³⁺.The optimal doping concentration of Er³⁺:Yb³⁺,Tb³⁺:Yb³⁺,Ho³⁺:Yb³⁺ were determined to be 1:7,1:3,1:5 and the mechanisms of up conversion luminescence were also analyzed.