Study On Preparation,Structure And Luminescence Properties Of Molybdenum Borosilicate Glass And Glass Ceramics

Light-emitting diodes（LEDs）have become a new generation of solid lighting source and display devices because of their high light efficiency,long life,low energy consumption,fast response and high color quality.Rare-earth luminescent materials are widely used in the field of white LED lighting and luminescent display.Rare-earth luminescent materials for LED mainly include phosphor,luminescent glass and luminescent glass ceramic.With the development of white LED lighting and display technology,people increasingly expect to develop new high-performance luminescent materials.Molybdate luminescent glass and glass ceramics have the advantages of non-toxicity and pollution-free,good luminescence performance,good physical and chemical properties,and low phonon energy,and are widely used as high-quality luminescent host materials.Thus,the research on rare earth doped molybdate glass and glass ceramics for LED has important theoretical significance and practical value.In this paper,molybdenum borosilicate luminescent glasses were prepared by high temperature melting method,and molybdenum borosilicate glass ceramics were prepared by controllable crystallization.FT-IR,DSC,XRD and TEM were used to characterize the thermal stability,phase composition and microstructure of glass and glass ceramics.Using ultraviolet-visible spectrophotometer,up/down conversion excitation emission fluorescence spectrometer and fluorescence lifetime decay spectrum,CIE color coordinates,color temperature CCT,optical properties and energy transfer mechanism of glass and glass ceramics were studied.Using fluorescence intensity ratio technique,the optical temperature-sensitive characteristics of typical molybdate glass ceramics are calculated and evaluated,and the results are as follows:1.FT-IR spectra show that rare earth doping has no effect on the amorphous structure of glass,but it can transform unstable BO₂O^-groups into stable BO₄ groups or BO₃ groups.The figure shows that there are Si O₄ group,BO₂O^-group,BO₄ group,BO₃ group and Mo-O bond structure in Mo O₃ in the glass,and it is determined that the glass network formers are molybdate,borate and silicate.2.Tm³⁺/Tb³⁺/Mn²⁺Mo-doped borosilicate glass:With the increase of Mn²⁺ion concentration,the distance between rare earth ions decreases,the interaction force increases,the possibility of fluorescence quenching increases,and the luminous intensity decreases.In the glass sample doped with 1.5Tm³⁺/5.0Tb³⁺/3.0Mn²⁺（mol%）,when the excitation light moves to the long wave direction,the blue light emission peak（located at 453 nm）is most affected by the excitation light wavelength,and the intensity decreases.The color coordinates move between the blue area and the yellow area.1.5Tm³⁺/5.0Tb³⁺/3.0Mn²⁺（mol%）glass sample has a color coordinate of（0.3386,0.3559）and a color temperature of 5253.49 K at the excitation wavelength of 360 nm,which is expected to be used in the field of white LED lighting.3.Tm³⁺/Dy³⁺double-doped molybdenum borosilicate glass and glass ceramics:The transmission spectrum shows that rare earth doping has certain influence on the transmittance of glass.For the glass sample doped with 0.8Tm³⁺/1.2Dy³⁺（mol%）,when the excitation light moves to the long wavelength direction,the intensity of the blue light emission peak at 454 nm first increases and then decreases,while that of the orange light emission peak at 576 nm decreases and then increases,and the color coordinates gradually move from blue-violet light to yellow light.With the increase of Dy³⁺ion concentration,the luminous intensity of the sample increases at first and then decreases.When the doping concentration of Dy³⁺is 1.2 mol%,the strong emission peaks of blue light and orange light are the sharpest,which indicates that the energy transfer is the strongest at this time.0.8Tm³⁺/1.2Dy³⁺（mol%）glass sample,under the excitation of 362 nm light,the color coordinates are（0.3462,0.3353）and the color temperature is 4894.74 K After holding at 540℃for 1 h,and then heating to 620℃for 2 h,NaLaMo₂O₈ crystal phase with stable tetragonal scheelite structure can be precipitated from the glass.It is proved that the luminous intensity of glass-ceramic samples is nearly doubled compared with that of glass,and the color coordinates of emitted light are basically unchanged.It shows that glass and glass-ceramic samples have good application potential in single substrate warm white light emission.4.Tb³⁺/Eu³⁺double-doped molybdenum borosilicate glass:The transmission spectrum shows that rare earth doping will affect the transmittance of the glass and reduce it.With the increase of Eu³⁺ion concentration,the strong emission peak of Tb³⁺ion at 454 nm decreases,and the strong emission peak of Eu³⁺ion at 576 nm first increases and then decreases.If the doping concentration of Eu³⁺is changed,the modulated luminescence between the green light emitting region and the orange red light emitting region can be coordinated,and the color coordinate changes from（0.4503,0.4937）to（0.5879,0.3734）,which is expected to be used in the light emitting display field.5.Tm³⁺/Tb³⁺/Eu³⁺Mo-doped borosilicate glass:With the increase of Tm³⁺ion concentration,the intensity of blue emission peak increases,while the intensity of other emission peaks decreases,and the energy transfer mechanism is Tb³⁺/Eu³⁺→Tm³⁺.The emission color coordinates of the sample doped with1.0Tm³⁺/2.0Tb³⁺/1.0Eu³⁺（mol%）are（0.3295,0.3362）,and the color temperature is 5629.35K,which is close to the color coordinates and color temperature of standard white light,so it has a potential application prospect in the field of near-ultraviolet excited white light LED.6.Yb³⁺/Er³⁺double-doped molybdate glass-ceramic:NaLaMo₂O₈ nano-transparent glass-ceramic with scheelite structure can be obtained by two-step heat treatment process,that is,holding at 540℃for 1 hour and then heating to 620℃for 2 hours.XRD finishing results show that Yb³⁺/Er³⁺ions enter the Na/La sites in the crystal structure of NaLaMo₂O₈.The results of up-conversion emission spectrum changing with pump power show that the mechanism of luminescence process is up-conversion emission by absorbing three photons.The glass-ceramic sample doped with 2.0Yb³⁺/0.1Er³⁺（mol%）has the highest luminous intensity.The results of optical temperature measurement show that the absolute sensitivity（Sa）and relative sensitivity（Sr）of 2.0Yb³⁺/0.1Er³⁺（mol%）glass ceramic samples are 1.406×10^-2 K^-1 and 0.697%K^-1 respectively when the temperature rises from 373 K to 623 K.Its good thermal stability is expected to be used in the fields of optical temperature sensor and up-conversion luminescence display.