Study On The Preparation And Properties Of Rare Earth And Transitional Metal Ions Doped Luminescence Glasses For LED Applications

Light emitting diodes?LEDs?have attracted wide attention due to their considerable advantages in long lifespan,high efficiency,small volume,good shock resistance,environment friendly,energy-saving,safety etc.and also shown great potential for lighting,decorating,displaying and so forth.Currently,the commercialized W-LEDs with the advantages of low cost and high brightness are fabricated by combining a blue semiconductor chip with yellow YAG:Ce phosphors.However,the W-LEDs developed in this way have lower color rendering,difficulties in realizing fluorescent powder coating uniformity and heat dissipation,as well as aging of epoxy resin,all of which would hinder their further development.Besides,with the improvement of people's living level,the multicolor LED suitable for scene light would gradually become the core-competitiveness for lighting source applications,surely making more consideration taken into the multicolor and homogeneous luminescence of LEDs.Compared with the crystalline phosphors used in W-LEDs,luminescence glasses are promising candidates to prepare W-LEDs because glasses possess the merits of excellent luminous uniformity,homogeneous distribution of the activated ions,high transparency,high thermal stability,low production cost,easy to fabrication,free to epoxy resin and so on.In this case,we investigate the rare earth or transition metal ions doped luminescence glasses for LEDs in this paper.We prepared a series of Eu/Dy doped calcium aluminoborosilicate glasses and Ce/Ho/Sm,Pr³⁺as well as Mn⁴⁺doped oxyfluoride silicate glasses by melting-quenching method.These glasses are studied via optical absorption,emission spectra,excitation spectra,X-ray diffraction?XRD?,Fourier transform infrared?FTIR?spectra,color coordinates and correlated color temperatures?CCTs?.The main research contents and the results are as follows:For the Eu-/Dy-single and co-doped calcium aluminoborosilicate glasses prepared in air atmosphere,with increasing the content of B₂O₃,more Eu³⁺ions are spontaneously converted to Eu²⁺ions.Before up to the quenching concentration,the addition of Eu can make more Eu³⁺reduced to Eu²⁺.Besides,we also find that the introduction of Dy³⁺ions can affect the reduction extent from Eu³⁺to Eu²⁺.In the Ce/Ho/Sm doped oxyfluoride silicate glasses,the introduction of Al₂O₃ in glass composition can improve the emissions of Ho³⁺and Sm³⁺.While the presence of B₂O₃ has the adverse effect and can suppress the emissions of Ho³⁺and Sm³⁺.With substituting Na₂O for CaO in the glass compositions,CaF₂ crystals can be formed during the melt quenching process.We find the formation of CaF₂ crystals can change the emission behavior of Ho³⁺and Sm³⁺ions.Furthermore,the emission of Sm³⁺ions could excite the Ho³⁺ions and be absorbed,consequently weakening the emission intensity of Sm³⁺.In the Pr³⁺single doped oxyfluoride silicate glasses,we find that replacing Ca O with Na₂O in base glass composition can favor the formation of CaF₂ crystals during the melt quenching process.The content of CaF₂ crystals can be controlled by changing the proportion of Al₂O₃ to ZnO in the glasses.The results of FT-IR spectra show that the glass structure is compositional dependent.Besides,the addition of Al₂O₃ and ZnO in glass composition can enhance the ³P₀?³H₄ emission of Pr³⁺ions,whereas B₂O₃ and SiO₂ have the adverse effect.The self-excitation of Pr³⁺is observed using the excitation wavelength of 443 nm,which can be strengthened with the increase of CaF₂ crystallinity.Furthermore,a unique emission peak at 690 nm is observed in glass containing crystalline Al₂O₃.The variation of glass composition can change the site of Mn⁴⁺ions in oxyfluoride silicate glasses,and the emission and excitation spectra of Mn⁴⁺located in distinct sites show some difference with each other.The addition of Al₂O₃,B₂O₃and SiO₂ can affect the site distributions of Mn⁴⁺,and the ability of influencing the site distributions is in the order of SiO₂>B₂O₃>Al₂O₃.The glass matrix composition,excitation wavelength and concentration of rare earth ions can affect the photoluminescence spectra,color coordinates and correlated color temperatures?CCTs?of luminescence glasses.For the Eu/Dy doped calcium aluminoborosilicate glasses and the Ce/Ho/Sm doped oxyfluoride silicate glasses,the white light is achieved and the emission color can be tailored.In addition,for the Pr³⁺and Mn⁴⁺single doped oxyfluoride silicate glasses,the emission spectra can be controlled by adjusting the glass compositions.