Preparation And Luminescent Properties Of UV Excited Tri-color Phosphor

White light-emitting diodes (LEDs) are considered to be the next generation solid statelighting devices due to their attractive attributes such as durability, small volume, longlifetime and environment friendly. The development of LEDs is accelerated with the arisingof effectively near UV chip that can emit350~400nm light, which put forward higherrequirements for effectively tri-color phosphor that can be excited by near UV light.A novel Sr3SiO5:Eu2+phosphor was synthesized by high temperature solid state method.The emission spectra are composed of two emission bands centered at476and578nm,respectively when the concentration of Eu2+ions is lower. The blue emission peak weakensgradually with increasing of Eu2+concentration and disappears when Eu2+concentrationreaches1mol%. The yellow emission peak enhances with Eu2+concentration and theconcentration quenching occurs when Eu2+concentration reaches1mol%. The criticaldistance Rc are3.06and2.62nm, respectively according to Dexter theory and Blasseequation. Furthermore, Eu2+ions have energy transfer in the two emission center of Sr3SiO5and the concentration quenching is attributed to electric dipole-dipole transition (d-d).Red SrBPO4:Eu3+phosphor was prepared by high temperature solid state method and theinfluence of Eu3+concentration, types and content of flux and charge compensator on theluminescent properties is investigated. The XRD patterns indicate that the SrBPO5samplesare simple phase and the sintering again help the growth of crystal lattice. There are emissionpeaks at589,596,614,653and687nm, which the peak at596nm attributed to the5D0â†'7F1transition, is the biggest. The excitation spectrum constitute of a wide band at the region of225to228nm and a series of narrow peaks from280to450nm. The excitation peak at395nm is the strongest. The result indicate that the phosphor can be excited by UV light and emitbetter red light. The concentration quenching does not appear with increasing of the activatorconcentration. The flux can enhance the luminescence intensity and NH4Cl is the optimal fluxin this phosphor. Li2CO3, Na2CO3and K2CO3can be used as charge compensator, in whichthe Li2CO3is the topgallant. The yellow emitting phosphors Ca3SiO4Cl2:Dy3+were synthesized by traditionalhigh-temperature solid state reaction method and the luminescence properties were studied indetail. The results indicate that the emission band is a broad band with multi-peaks，whichconsists of two main peaks located at479nm and569nm, respectively. The excitation peakspositioned around320nm,345nm,363nm,384nm,420nm,449nm. The results illustratethat the emitting of Ca3SiO4Cl2: Dy3+can be changed by adjusting the synthesis temperatureand the Dy3+concentration. The most effective sintering temperature is1000℃. The effectsof different flux on the luminescent intensity were studied in detail. Ca3SiO4Cl2:Dy3+is agood blue-white phosphor candidate for white light emitting diode.The series Sm3+-activated phosphors of Ca3SiO4Cl2:Sm3+were prepared by solid-statemethod. The structure and luminescent properties of these powder samples have beeninvestigated by means of X-ray diffraction (XRD), and fluorescent spectrophotometry,respectively. Under ultraviolet excitation, the emission spectrum of Ca3SiO4Cl2:Sm3+showsseries narrow bands centered at564nm,608nm and648nm, in which the relative intensity ofthe648nm is the strongest. Monitoring for648nm, a series of narrow line spectra peaked at363nm,376nm and404nm, respectively. The phosphor can be efficiently excited when thedoping concentration is6mol%. The mechanism of concentration quench was studiedaccording to the relation between doping concentration of Sm3+ions and the luminescentintensities of samples. This phosphor is a better red phosphor for white LED.