Investigation On Rare Earth Doped CaO-MgO-SiO₂ Luminescent Glass Ceramic

Rare earth doped glasses are considered to be one of the promising materials for fiber amplifiers,lasers,fluorescent devices and white light emitting diode(LED).For the past decades,a large amount of luminescence research has focused mainly on two aspects.One is crystal matrix,another is non-crystalline matrix.But the poor stability of crystal and the weak luminescence properties of glass limited their further application for the optical devices.Glass ceramic,as the glass and crystal composites, has attracted strong interests for their excellent luminescence properties, machinability,high uniformity and stability.Sm³⁺,Tb³⁺,Eu²⁺doped CaO-MgO-SiO₂ luminescent glass ceramics were prepared in this paper.X-ray Diffraction(XRD)and scanning electron microscope(SEM)were availed to measure the crystalline phase and microstructure of the glass ceramics to find the proper nucleation agent and heat-treatment.Jasco FP-6500 fluorescence spectrometer was used to get the emission and excitation spectra of samples.The effects of heat treatment,concentration of rare earth and co-doped rare earth were discussed.At last, the distribution and luminescent mechanism of rare earth ion in the glass were studied by XRD,Raman spectroscopy,and Electron Microprobe.The results indicate:1.the glass ceramic,predominantly composed of diopside with small amount of glassy phase,were obtained after heat treatment.The crystal content of glass ceramic increased as heat treatment temperature icreasing.2.Sm³⁺doped glass ceramics can emit red light under the excitation of long UV and blue lights.The glass ceramics show emission with peaks at 564 nm,601 nm,648 nm and 710 nm due to transitions ⁴G_5/2→⁶H_J(J=5/2,7/2,9/2,11/2)of Sm³⁺.Tb³⁺ doped glass ceramics emit intense light with cyan color under UV excitation, emission peaks observed are assigned to be the ⁵D_4,3→⁷F_6,5.4,3transition of Tb³⁺. Eu²⁺doped glass can emit blue light under the excitation of long UV and blue lights.3.With the increase of reheat temperatures and the precipitate of diopside,the wavelength of peaks of Sm³⁺and Tb³⁺in optical spectra has no change,but the luminescence of the glass ceramics is stronger than corresponding glass. The luminescence intensity is increased with the increasing of the Tb³⁺content. And concentration quenching effect was also observed in the glass ceramic when the content of Sm₂O₃ over 0.1 mol%.Enhancement of Tb³⁺luminescence intensities are observed in Tb³⁺,Gd³⁺ co-doped glass ceramic,and the sensitization is due to the energy transfer from Gd³⁺to Tb³⁺.The luminescence intensity of Eu²⁺increases with Dy₂O₃ addition.The flurescent spectras of Sm³⁺and Tb³⁺codoped glass ceramics were consist of the characteristic spectrim of Sm³⁺and Tb³⁺respectively.The 350nm～385nm or 475nm～500nm excitation could induce the emissions of Sm³⁺and Tb³⁺,and the 390nm-420nm excitation would only cause the emissions of Sm³⁺.4.The structure analysis shows that the rare earth ions dispersed in the matix homogeneously,when rare earth ions entered the lattice,it would only replace Ca²⁺ sites,suggesting that the enhancement of the luminescence intensity was caused by this strong crystal field acting on rare earth ions.