Preparation And Performance Study Of SrLu₂O₄:Ce³⁺ Blue Phosphor Excited By Near Ultraviolet

With the advancement of white light-emitting diodes(w-LEDs)technology and human pursuit of higher lighting quality,the full-spectrum w-LEDs has attracted widespread attention in the industry due to their excellent performance,such as safety and health,high color reduction and saturation,and good spectral continuity.In recent years,SrLu2O4:Ce3+blue phosphor has been reported,its main excitation peak matches well with near ultraviolet LED chip,and full width at half maximum(FWHM)is wide,high thermal stability,which shows that SrLu2O4:Ce3+has a very good application prospect in full-spectrum w-LEDs.However,the current research on this phosphor is inadequate,the luminescence mechanism is still unclear.Especially,the preferential occupation position of the activator Ce3+ is unclear,and the spectrum is not adjusted,and the luminous efficiency is not improved.Therefore,this thesis carried out detailed research on these issues.SrLu2O4:Ce3+phosphor was synthesized at the different temperature by the high temperature solid-sate reaction method.The study found that SrLu2O4:Ce3+phosphors synthesized atl560? or 1600? have one more excitation band with peak at around 360 nm than that at 1480? or 1520?.Meanwhile,with the increase of synthesis temperature,the photoluminescence emission(PL)intensity increases,the PL bands shows a slight red shift,and the emission of the shoulder peak region is enhanced.Combining the refinement of crystal structure,characterization of luminous properties,and theoretical analysis of crystal field,it is concluded that Ce3+of SrLu2O4:Ce3+synthesized at 1480? or 1520?occupies only Sr2+sites,while Ce3+of SrLu2O4:Ce3+synthesized at 1560? or 1600?occupies Sr2+and Lu3+sites.The photoluminescence of SrLu2O4:Ce3+phosphor was studied.Analysis found that the phosphor was efficiently excited in the 250-430 nm region,and could achieve emission in the region of 420-600 nm with a peak wavelength of 459 nm,and FWHM is about 90 nm.The emission intensity increases as the Ce3+ion concentration increases,up to 0.15%,then tends to decrease gradually due to the concentration quenching effect,the major quenching mechanism on the doping levels is dipole-dipole interaction.The external quantum efficiency of SrLu2O4:Ce3+at 150?(423 K)remian 84.3%of that of the room temperature(298 K),which showed that its temperature characteristic is obviously superior to the current commercial blue phosphor.By replacing Sr2+ by Ca2+,the crystal structure and photoluminescence properties of Sr1-xCaxLu2O4:Ce3+(x=0-1.0)phosphors were studied.With increasing x,the crystal field splitting and Stokes shift of Sr1-xCaxLu2O4:Ce3+were increase,which results that the excitation peak of Sr1-xCaXLu2O4:Ce3+phosphors were red-shifted from 405 to 420 um,and the dominant emission peak could be red-shifted from 459 to 503 nm.The performance of Sr1-xCaxLu2O4:Ce3+(x=0-0.2)phosphors was investigated in detail.The emission peaks of the Sr1-xCaxLu2O4:Ce3+(x?0-0.2)phosphors can be red-shifted from 459 to 465 nm.When x=0.2,the emission intensity is increased by 23%,the external quantum efficiency is increased by 34.9%.And since the thermal quenching activation energy and band gap width were increase,the thermal stability of Sr1-xCaxLu2O4:Ce3+was further improved by the substitution of Ca2+ions(86.2%).The application performance of Sr1-xCaxLu2O4:Ce3+(x=0-0.2)was evaluated.W-LEDs was fabricated by using Sr1-xCaxLu2O4:Ce3+(blue),,?-sialon:Eu2+(green)and(Sr,Ca)AlSiN3:Eu2+(red)phosphors combined a 405 nm near-UV LED chip.When applying Sr0.8Ca0.2Lu2O4:Ce3+or SrLu2O4:Ce3+as the blue phosphor,the former package device had the higher luminous efficiency than the latter one,and CRI of both devices greater than 95.0.These results show that Sr1-xCaxLu2O4:Ce3+was a potential blue phosphor for n-UV pumped full-spectrum w-LEDs application.