Study On Synthesis And Luminescent Properties Of Borate Phosphors For White LEDs

The reasearch of high quality and environmental protection phosphors forwhite LEDs is key to the development of lighting industry. Based on the excellentluminescent properties of borate phosphors, a battery of Sr3B2O6and LiSrBO3phosphors were synthesized using high temperature solid-state technique in thisstudy. The crystal structure and luminescent performance of the samples doping withdifferent rare earth ions were studied using X-ray diffraction, SEM andphotoluminescence spectroscopy, etc.The Eu2+-doped Sr2.94B2O6:0.06Eu2+yellow phosphor was sintered bycommonly used solid-state reaction technique. The excitation spectra of the samplehad the wavelength ranging from300nm to500nm, and it exhibited yellow lightpeaking at576nm under450nm blue light excitation. The impact of preparationtechnology on the spectral performance of Sr2.94B2O6:0.06Eu2+was carefullyexplored. Results showed that the best preparation condition is synthesized at1100℃for6hours. We also researched the luminescence performance of theSr3-xB2O6: xEu2+samples, and when the Eu2+concentration reached0.06mol, thetypical quenching phenomenon arises. Caculation and analyzing assured thatconcentration quenching for the Eu2+site emission centers is caused by dipole-dipoleinteraction in the Sr3-xB2O6: xEu2+phosphor.A battery of Sr2.94-xCaxB2O6:0.06Eu2+and Sr2.94-xBaxB2O6:0.06Eu2+sampleswere sintered through high temperature solid-state reaction technique. With Ca2+concentration rising, the crystal field intensity declines, the spectra ofSr2.94-xCaxB2O6:0.06Eu2+appeared an abvious blue shift; the crystal field intensityincreases when Ba2+concentration increasing, Sr2.94-xBaxB2O6:0.06Eu2+had a redshift in emission wavelength. The color of Sr3B2O6: Eu2+phosphor could becontrolled by changing crystal field environment.The solid-state reaction technique was used to synthesize a Ce3+ion/Eu2+ionco-doped Sr3B2O6: Eu2+, Ce3+phosphor. Upon351nm excitation, finally white lightcould be released from Sr3B2O6: Ce3+, Eu2+samples by constantly adjusting the relative ratio of Ce3+/Eu2+. The cause of energy transfer from Ce3+to Eu2+in theinternal crystal structure was further investigated. The emission intensity ofSr3B2O6: Eu2+phosphor can be efficiently strengthened by co-doping with Ce3+andDy3+. The inclusion of Ce3+and Dy3+in Sr3B2O6: Eu2+samples dramaticallyincreased the fluorescence intensity by56%and70%, separately.The high temperature solid-state technique was used to synthesize theEu2+-doped LiSr0.96BO3:0.04Eu2+yellow phosphor which had the excitation spectraranging from300nm to500nm. And it exhibited a single emission peaking at570nmunder the380nm UV light excitation. Further more, we researched the luminescenceperformance of the LiSr1-xBO3: xEu2+samples, and when the Eu2+concentrationreached0.04mol, the typical quenching phenomena arises, an obvious red shift inemission spectra were noticed with the increase of Eu2+. It was found that theinclusion of Dy3+, Mn2+in LiSrBO3: Eu2+dramatically enhanced the fluorescenceintensity by51%and70%, separately.