| As the most promising electric light source in21century, light emitting diode (LED) which is a kind of semiconductor device can convert electrical energy to visible light directly. But at present white LED commodity on the market exists some disadvantages such as aging and discoloration of phosphor, decrease of brightness, poor heat conduction of epoxy resin and so on in the practical application. Transparent oxide glass is the ideal luminescent matrix materials, for the stable physical and chemical properties, high rare-earth ion solubility and easy forming, etc. Rare earth elements have excellent luminescent properties, and can realize white light emission by the mixing of multicolor emission band. So glass as matrix material, doped with rare earth ions is useful for seeking the excellent luminous materials used for white LED, and providing some theoretical and technical support for the research of luminous materials.Rare earth doped SrO-TiO2-SiO2luminescence glass and glass-ceramics have been prepared by choosing strontium titanium silicon glass as matrix materials, adding2to reduce matrix phonon energy, and doping Sm3+, Tb3+, Dy3+. The influence of2content, rare earth ions content and type, and heat treatment system on glass structure and luminescent properties have been studied by X-ray fluorescence, IR, XRD, SEM and fluorescence spectra. The results indicate that:1. SrF2could reduce the glass transition temperature and crystallization temperature, and F-into the glass network caused the change of Sm3+doped SrO-TiO2-SiO2glass structure. A new infrared absorption peak appeared in the930nm and enhanced with the increase of SrF2content.2. With the adding of SrF2and the increase of content, the excitation and emission peaks had no change in position and shape. Because of the low phonon energy, SrF2could reduce non-radiative transition between Sm3+and the glass matrix and cut down Sm3+local symmetry, which increased the luminous intensity.3. The concentration quenching effect was observed when the content of Sm3+over0.5mol%, or Dy3+over0.75mol%, but not found in Tb3+doped glass. The increase of the rare earth ion content had no influence on the positions and shapes of spectral peaks.4. Sm3+, Tb3+co-doped SrO-TiO2-SiO2glass could emit near white light under the excitation of378nm, and the light was closest to white light when Sm3+:Tb3+=1:5(mol%). Dy3+doped SrO-TiO2-SiO2glass could emit white light under the excitation of349nm, and the light was closest to illuminant C when the content of Dy3+was0.75mol%.5. The crystal phase in transparent Sm3+, Tb3+co-doped SrO-TiO2-SiO2glass ceramics was Sr2TiSi2O8, and Tb3+promoted body oriented crystals. With the improvement of the heat treatment temperature and time, the color of glass ceramics obtained changed from dark yellow/brown to light, the size of the crystals became big, even to300μm, and the transmittance decreased gradually resulting in opaque.6. Under the excitation of378nm, the luminous intensity of Sm3+, Tb3+co-doped SrO-TiO2-SiO2glass ceramics was lower than glass. The positions of emission peaks changed little, but their shapes became smooth and flat, and the split of Tb3+characteristic emission peak at541nm disappeared. There were a small number of crystals in ST1series glass ceramics, and the rare earth ions into the crystals were few, which almost couldn’t improve the luminous intensity, at the same time, the glass ceramics had low transmittance which affected the luminescent intensity greatly. |
PDF Full Text Request