Preparation Of Red Phosphor And Study On Luminous Properties For White LED

White light diodes have become a new generation of lighting source because of their low energy consumption,long life and good luminous effect.At present,the following two methods are commonly used to synthesize white light:?1?red,green and blue phosphors excited by near ultraviolet chips.?2?yellow phosphors excited by blue LED chips.In the first method,due to the coating of red,green and blue phosphors,the color rendering index of white light is relatively high.at present,the luminous efficiency of red phosphors used in near-ultraviolet chips is lower than that of the other two colors,and there are fewer kinds of red phosphors.The second method is lack of red light,and the color rendering index is low.Therefore,it is necessary to study a kind of red phosphor with low price and good luminous performance.Common red phosphors have the following systems:molybdate system,silicate system,tungstate system,vanadate system.Among them,rare earth vanadate system has been widely used in luminescent materials because of its good stability and low price.Eu³⁺and Sm³⁺are common red luminescence centers with low cost and strong fluorescence emission when excited.In this paper,the red phosphor Sr₉Y?VO₄?₇ is used as the matrix material,and the crystal structure and luminescent properties are studied by doping rare earth ions Eu³⁺and Sm³⁺.It is expected to obtain a kind of red phosphor suitable for white LED.The sample was prepared by high temperature solid state method,the calcination temperature was 1300?and the calcination time was 4 h.Through the study,the following conclusions are drawn:?1?It is found that the monitoring wavelength is set at 616 nm and the excitation peaks in the excitation spectra are located at 395 nm,465 nm and 538 nm for Sr₉Y_1-x?VO₄?₇:xEu³⁺?x=0.15,0.2,0.25,0.3,0.4,0.5,0.6,0.7,0.8?samples doped with different concentrations.Under the excitation of 395 nm?near ultraviolet?excitation light,the emission peak of the sample is the strongest when the doping concentration of Eu³⁺is 0.5.The emission spectrum covers the wavelength range of 420 nm-750nm,and the emission peak is located at 594 nm,619 nm,652 nm and 700 nm,among which the 619 nm?red light?emission peak is the strongest.Under the excitation of465 nm?blue light?,the emission spectrum range is 490 nm,and the emission peak is located at 534 nm,588 nm and 614 nm,and the 614 nm emission peak is the strongest.When the doping concentration of Eu³⁺is x=0.4,the above three emission peaks are the strongest.At this concentration,the color coordinate of the sample is?0.41,0.25?,which is located in the orange-red region.To sum up,Sr₉Y_0.6?VO₄?₇:0.4Eu³⁺is an orange-red phosphor,which can be used as a red phosphor excited by near-ultraviolet or blue light.?2?The study of Sr₉Y_1-x?VO₄?₇:xSm³⁺?x=0.01,0.02,0.03,0.05,0.07,0.10,0.15,0.20,0.25,0.35?samples with different concentrations of Sm³⁺shows that the monitoring wavelength is 604 nm,and the excitation wavelengths in the excitation spectrum are 405 nm and 478 nm.The strongest excitation peak is at the wavelength405 nm.From the emission spectrum under 405 nm excitation light,it can be seen that the spectral range is 420 nm,the luminescence peak is located at 563 nm,604 nm and 647 nm,and the strongest luminescence peak corresponds to the wavelength 604nm.When the doping concentration of Sm³⁺is 0.15,the above three emission peaks are the strongest.Under 405 nm excitation,the color coordinate of Sr₉Y_0.85?VO₄?₇:0.15Sm³⁺is?0.46,0.34?,which is expected to be a red phosphor for LED excited by near-ultraviolet light.