Structural Design And Application Of Nitrogen Oxide?Ba,M?Si₂O₂N₂?M=Sr,Ca? Blue Green Phosphor

As an important part of strategic emerging industries,solid-state lighting has received global attention and has established a leading position in the field of lighting.Currently,the global solid-state lighting technology continues to break through,the overall scale of the industry is growing and market applications is broaden constantly,which makes the market application field of white LED continues to expand from simple pursuit of light efficiency to the improvement the light quality.And also gradually expands from lighting,backlight,display to medical treatment,agriculture and other fields.The core technical obstacle which restricts high-quality light environment is the preparation of high-quality phosphor.At present,the mainstream technology of white LED is stimulating the yellow-green phosphor by blue light chip to synthesize white light.Which leads to the obvious gap of high color rendering(Ra>80)white LED in the blue-green light band.As a result,the white LED is not enough to restore the blue-green color.Therefore,the solution to full spectrum lighting is to modulate the spectrum with new-structured blue-green light emission phosphor.The Eu2+-activated oxynitride BaSi2O2N2:Eu2+phosphor can effectively absorb blue light in the range of 440 nm to 460 nm and emit blue-green light with a peak wavelength about 495 nm.With the discovery of BaSi2O2N2:Eu2+phosphors,the lack of blue-green light in the full spectrum has been effectively complemented,and full-spectrum white LED packaging is possible.However,there is still a large gap between BaSi2O2N2:Eu2+phosphor and widely used YAG(Y3Al5O,2:Ce3+)yellow-green phosphors and CASN(CaAlSiN3:Eu2+)nitride red phosphors in terms of the thermal quenching performance and the long-term anti-high temperature and high humidity performance.In other words,the brightness and color coordinate retention rate of BaSi2O2N2:Eu2+phosphor is low under high temperature and high humidity environment,which limits its application in white LED.Therefore,it is necessary to improve the reliability of BaSi2O2N2:Eu2+phosphor.In this thesis,BaSi2O2N2:Eu2+phosphor was studied,and its preparation method,spectral characteristics and the improvement of luminescence reliability were studied.The main research work is as follows:1.The BaSi2O2N2:Eu2+phosphor was synthesized by a one-step high temperature solid state reaction method and a two-step high temperature solid state reaction method using Ba2SiO4:Eu2+green powder as the pre-synthesis precursor.By comparing the two methods,it is found that the luminous intensity of the phosphor synthesized by the two-step method is 180%of that of the phosphor prepared by one-step method.The phosphor synthesized by the two-step method has higher luminescence because the synthesized phosphor has more excellent crystallization properties and the particle morphology is more regular.The high-temperature solid-state synthesis process of two-step synthetic phosphors was optimized.The effects of key synthesis processes such as thermal insulation process,temperature rise process system,combined synthesis atmosphere and insulation platform on the luminescence properties were studied,and the best synthesis process was obtained.2.The luminescent properties,the concentration quenching of luminescence as well as the effect of alkaline earth ion doping on the luminescent behavior of BaSi2O2N2:EU2+ phosphors were investigated.It is found that the BaSi2O2N2:Eu2+phosphor emits blue green light with the peak wavelength at 495 nm and has higher color purity.The excitation spectrum of BaSi2O2N2:Eu2+phosphor covers 300-460 nm band,which matches the emission band of blue LED chip well.The experiment also found that the concentration quenching of luminescence in BaSi2O2N2:Eu2+was caused by the increase of the electric dipole-electric dipole energy transfer probability of Eu2+,and the optimum doping concentration of Eu in BaSi2O2N2:Eu2+was 0.06mol%.The effects of alkaline earth ions doping on the luminescence of BaSi2O2N2:Eu2+phosphors was also investigated.The doping of Mg caused the decrease in luminescence of BaSi2O2N2:Eu2+phosphor and deteriorated its crystallization properties.The doping of Sr resulted in red shift of the emission spectrum of BaSi2O2N2:Eu2+phosphors,but its luminous efficiency is hardly affected.The doping of Ca not only caused a red shift of the emission spectrum but also caused a decrease in luminescent performance of BaSi2O2N2:Eu2+phosphor.3.The effect of Na+-Ge4+combined ion doping on the thermal quenching performance of BaSi2O2N2:Eu2+blue-green phosphor was studied.The XRD results show that the Na+-Ge4+combination ions doping does not bring heterophase in the synthesis of phosphors,indicating that the Na+-Ge4+combination ions successfully enter the matrix of the phosphor,and the doping makes the crystal structure of BaSi2O2N2:Eu2+phosphors more stable.The results of thermal quenching show that the Na+-Ge4+doping improves the emission intensity of BaSi2O2N2:Eu2+phosphor in the working environment at 150? by 12%.Doping also improved the color shift property of BaSi2O2N2:Eu2+phosphor at high temperatures.After Na+-Ge4+ions doping,the color shift caused by the thermal quenching of BaSi2O2N2:Eu2+blue-green phosphor improved by 98%,indicating that the anti-high temperature bleaching ability of the phosphor is significantly improved.4.The effects of SiO2 coating on the luminescence and thermal properties of BaSi2O2N2:Eu2+phosphors were investigated.In the research,it was found that in order to ensure the luminescent property and the coating effect at the same time,the optimum coating amount of SiO2 is 6 wt%.Under the coating amount of 6 wt%,the coating thickness is about 36 nm detected by the long etching time XPS,which matches well with the results of the TEM test.After coating,the thermal quenching performance of BaSiO2N2:Eu2+ phosphor increased by 2.4%at 150?,and the luminescent performance increased by 15%after baking at 500?.The performance of high temperature and high humidity resistance of BaSi2O2N2:Eu2+phosphor was significantly improved as well.According to the analysis of the test results,SiO2 coating has formed a dense amorphous film on the surface of the phosphor,which not only prevents the luminescent center in the phosphor surface from being oxidized,but also prevents the phosphor from being eroded by high temperature water vapor.5.Finally,the application of BaSi2O2N2:Eu2+phosphor prepared in this thesis in full-spectrum LED packaging was studied.The synthesized BaSi2O2N2:Eu2+phosphor combined with YAG yellow-green phosphor and CASN red phosphor can package 2700K-6500K full-spectrum white LEDs with different color temperature.The full-spectrum white LEDs of the above color temperature has the color rendering indices greater than 97,and all the special color rendering indices are greater than 90,which satisfies the requirements of the full spectrum LED.The aging results of the white LED showed that the aging performance of BaSi2O2N2:Eu2+blue-green phosphor improved by doping and SiO2 coating was significantly improved,and the color shift of white LED was also reduced.6.A new type of Ba3Si6Oi2N2:Ce3+,Eu2+green phosphor was synthesized.The energy transfer from Ce3+to Eu2+was confirmed by spectral test and fluorescence lifetime test.Based on energy transfer,the luminescence intensity of Ba3Si6O12N2:Ce3+,Eu2+phosphor is 150%of the luminescence intensity of Ba3Si6O12N2:Eu2+phosphor,indicating that the energy transfer significantly enhances the luminescence intensity of Ba3Si6O12N2:Ce3+,Eu2+phosphors.The obtained Ba3Si6O12N2:Ce3+,Eu+2 phosphor is a promising green phosphor.