Preparation And Luminescence Properties Of Alkali Metal Vanadate

In recent years,as a new generation of green lighting source,white light-emitting diode?LED?has been widely used in military,medical and electronic industries for its advantages of low power consumption,long service life,small volume,fast response and excellent optical performance.Therefore,the research of phosphors for white LED has become a hot direction that people pursue,never stop.At present,the blue-light chips widely used in the commercial market stimulate YAG:Ce³⁺yellow phosphors to emit white fluorescence.Although this technology has been quite mature,there are still shortcomings such as lack of red light and poor color rendering.Therefore,many researchers are looking for a new kind of phosphor material with high luminescent properties for white LED,in which the use of ultraviolet-near ultraviolet light to excite red,green and blue phosphors is a solution.In this paper,the synthesis and luminescent properties of alkali metal vanadium metavanadate AVO₃?A=Rb,Cs,K?as a phosphor for white LED are studied.The specific contents and conclusions are as follows:In this paper,RbVO₃ and CsVO₃ phosphors were prepared by solid-phase synthesis method.The two samples were analyzed by X-ray diffraction?XRD?to determine their crystal structure.The morphology of the samples was observed by scanning electron microscopy.The photoluminescence spectra of the samples were measured by fluorescence spectrophotometer.Colour coordinates.The final results show that the particle size of RbVO₃ is about 1.6-1.8 um,the wavelength range of photoluminescence spectrum is between 400-700nm,the maximum emission peak is at 507nm,and the chromaticity coordinates are?0.3415,0.3960?.The particle size of CsVO₃ is about 2-3 micron.The wavelength range of photoluminescence spectrum is 400-700nm,the peak value is 492nm,and the color coordinate is?0.3591,0.4131?.In addition,theoretical studies have been carried out.Based on the first principle of density functional theory and GGA optimization,crystal models have been constructed to calculate the band,density of states,dielectric function and absorption spectra of RbVO₃,CsVO₃ and KVO₃.The final results show that the calculated optical band gap of RbVO₃ is2.973eV,the absorption spectrum is 125-450nm,and the absorption peak is 5.62eV,226nm.The band gap is 3.143eV,the absorption wavelength is 139-340nm,the peak absorption coefficient is5.69eV,224nm;the optical band gap of KVO₃ is 3.042eV,the strongest abs peak is 5.25eV,220nm,and the absorption range is 129-300nm;the optical band gap of RbVO₃ is the narrowest,and the color coordinate is the closest to the pure white coordinate.RbVO₃,CsVO₃ and KVO₃ are all direct band gap semiconductors.The luminescence mechanism originates from the single electron transition between the 2p orbital of O and the 3d orbital of V.They can be excited by ultraviolet-near-ultraviolet broadband to emit white light.