Study On The Preparation And Luminescence Properties Of Ce And Mn Doped In CaM₂Al₄SiO₁₂?M=Y,Lu? Phosphors

Recently,increasing attention has been focused on the research in phosphor-converted white LEDs?pc-WLEDs?due to their excellent properties,such as higher efficiency,energy saving,long lifetime,and environment friendly features.The most popular way to obtain WLEDs is to combine yellow emitting phosphor YAG:Ce with blue InGaN LED chip.However,the white light obtained in this way has low fraction of red light and thus the color rendering index lower and the correlated color temperature is high.To overcome these deficiencies,the yellow/green phosphor blended with red nitride phosphor is applied.However,the reabsorption of emission colors and the difference in degradation between different host phosphor will lead to the loss of luminous efficiency and color aberration.Therefore,it is urgent to explore a new phosphor to solve the above problem.?1?CaY_2-xLu_xAl₄SiO₁₂:0.002Mn⁴⁺?x=0,0.6,1,1.6,2?and CaLu₂Al₄SiO₁₂:xMn⁴⁺?x=0.001⁰.005?phosphors were synthesized by conventional solid-state reaction.The influence of the sintering temperature,raw materials and flux on the luminece properties of the prepared phosphors was studied.Rietveld refinements show that the CaY_2-xLu_xAl₄SiO₁₂ crystallizes as a cubic structure.The changes of the Y/Lu ratio on the crystal field strength and the luminescence properties of CaY_2-xLu_xAl₄SiO₁₂:0.002Mn⁴⁺?x=0,0.6,1,1.6,2?phosphors.The results indicate that the crystal field strength decreases gradually,and the absorption band and emission peak blueshift with the increasing of Lu content.The influence of the Mn⁴⁺content on the emission intensity and decay times of CaLu₂Al₄SiO₁₂:xMn⁴⁺?x=0.001⁰.005?phosphors was also investigated.The emission intensity of the CaLu₂Al₄SiO₁₂:xMn⁴⁺?x=0.001⁰.005?phosphors increases with the Mn content,and reaches the highest at x=0.002.The concerntraton quenching of the Mn⁴⁺in CaLu₂Al₄SiO₁₂ is demonstrated to the dipole-dipole interaction.The decay times of CaLu₂Al₄SiO₁₂:xMn⁴⁺?x=0.001⁰.005?phosphors are shortend with the increasing of the Mn⁴⁺content.Due to the low cost,simple preparation,high luminous efficiency,and can be excited by UV and blue chip,they are expected to be potential red phosphors for WLED.The results indicate that garnet could be a promising phosphor for blue chip based white light emitting diodes?LEDs?.?2?Ce³⁺singly doped and Ce³⁺,Mn²⁺co-doped CaY₂Al₄SiO₁₂ phosphors were synthesized by conventional solid-state reaction.The crystal structure,luminescence properties and energy transfer mechanism between Ce³⁺and Mn²⁺were investigated.The results show that Ce³⁺ions occupy only the Y³⁺ions lattice,while Mn occupy not only the Ca²⁺ions lattice but also the Al³⁺ions lattice.According to the doping ratio of Ce³⁺and Mn²⁺,the luminous region can be adjustable from yellow to red.The color rendering index of the white LED combined by blue LED chips with Ce and Mn co-doped phosphor increases from 65 to 75,and color temperature decreases from 4712 K to 4620 K comparing to that combined by blue LED chips with of the Ce doped phosphor.The higher Ra and lower color temperature made CaY₂Al₄SiO₁₂:Ce³⁺,Mn²⁺phosphors to be candidates for WLED.