Study On The Effect Of Ti⁴⁺ Site Substitution And Eu³⁺ Co-doping On CaTiO₃:Dy³⁺ Luminescence Performance

As the fourth-generation lighting source,white LED has many advantages such as energy saving,environmental protection,high efficiency and long life.Although white LED has been commercialized and widely used,there are still many problems to be solved such as high prices,lighting quality and service life of far from expectations.Especially it is hard to obtain a warm white LED because of lacking of red light components in the phosphors.The above problems restrict the development of white LED in lighting,display and other application fields.It is a current research direction in LED lighting,display and other application fields to find white fluorescent powder materials with practical application,adjustable luminous color and color temperature and high luminous efficiency.Aiming at this kind of problem,the rare earth white luminescent material CaTiO₃:Dy³⁺,which is cheap,stable in structures and properties,and easily available raw materials,is selected to be synthesized and researched.In addition,relevant experiments and analytical methods are carried out to optimize its synthesis process conditions and performance.Firstly,using calcium nitrate as the calcium source,butyl titanate as the titanium source,rare earth dysprosium ions as the luminescence center and citric acid as the activating combustion aid,the CaTiO₃:Dy³⁺white light phosphors which have high purity,good luminous performance and orthorhombic crystal structure with space group of Pbnm（62）is synthesized by combustion method.The excitation spectrum of its fluorescence spectrum includes three near-ultraviolet characteristic excitation peaks of 353 nm,365 nm and 387 nm,and the emission spectrum consists of blue light at 484 nm and yellow light at 578 nm.The optimized synthesis process parameters obtained is 900°C and sintering 1 hour in a muffle furnace.The amount of citric acid burner is 1.5 times of the metal cation in the system and the the concentration of the light-emitting center Dy³⁺is 2 mol%.In order to improve the luminous performance of CaTiO₃:Dy³⁺phosphors,the Zr⁴⁺,Si⁴⁺and Al³⁺are selected to partial repalce Ti⁴⁺in CaTiO₃ lattice at B-site according to theoretical analysis.All three kinds of substituted ions can partially replace the position of Ti⁴⁺,causing distortion of the crystal lattice.In addition,all substituted ions can increase the luminous intensity of CaTiO₃:Dy³⁺and affect the fluorescence lifetime and color coordinate.The optimized concentration of the three substituted ions is 40 mol%for Zr⁴⁺,30 mol%for Si⁴⁺,and 1 mol%for Al³⁺.Compared the comprehensive fluorescence performance of the Ca(Ti_0.6Zr_0.4)O₃:Dy³⁺,Ca(Ti_0.7Si_0.3)O₃:Dy³⁺and Ca(Ti_0.99Al_0.01)O₃:Dy³⁺pohspohrs synthesized under their optimal conditions.The result is that Zr⁴⁺enhances the glow effect of CaTiO₃:Dy³⁺phosphor more than Si⁴⁺and Al³⁺.To improve the emitting color and color temperature performance of the synthesized Ca(Ti_0.6Zr_0.4)O₃:Dy³⁺white phosphor,a typical red luminescent rare earth Eu³⁺is selected to be co-doped with Dy³⁺in the phosphor.The results show that Eu³⁺has an excellent influence on the emitting color and color temperature of the phosphor.The doping of Eu³⁺can not only add the red light emission in the phosphor,but also adjust the emitting color and color temperature of Ca(Ti_0.6Zr_0.4)O₃:Dy³⁺,Eu³⁺phosphor by changing the excitation wavelength or Eu³⁺concentration.This is beneficial to broaden the application field of fluorescent materials and improve the application effect.