Synthesis And Luminescence Properties Of Ca₃SiO₄Cl₂-based Phosphors

Nowadays,The phosphor-converted light-emitting diodes(LEDs)for green lighting has received intense and growing interest,compared to conventional solid state lighting technology,the LEDs advantages in the properties of high luminous efficiency,long lifetimes,low pollution and power consumption and is called a new generation of lighting source.In this paper,Eu2+,Eu3+,Mn2+,Ce3+,Bi3+ single-doped and co-doped Ca3SiO4Cl2 via soft chemical method were prepared,and the influence of synthetic methods on the phase composition and photoluminescence of samples and energy transfer among the doped ions were discussed.The main results obtained in the paper are presented as follows:(1)Ca3SiO4Cl2:Eu2+ phosphor was prepared by sol-gel,sol-hydrothermal and gel-hydrothermal methods,respectively.The phosphor shows two kinds of structures,low temperature phase(LTP)and high-temperature phase(HTP)Ca3SiO4Cl2.Under the excitation of 365 nm,LTP Ca3SiO4Cl2:Eu2+exhibits green emission at 506 nm and HTP Ca3SiO4Cl2:Eu2+exhibits yellow emission at 585 nm.The polymorphic transition temperatures of Ca3SiO4C12:Eu2+phosphors prepared by three different methods are situated at 1002?,1005? and 1002?,respectively.The pure HTP Ca3SiO4Cl2 cannot be easily obtained for the HTP exsits in a narrow temperature interval.LTP-Ca3SiO4Cl2:Eu2+ phosphor prepared by sol-gel method has the highest green emission intensity.(2)A series of Ca3SiO4Cl2:Ce3?,Li+,Mn2+,Eu2+ phosphors were prepared by sol-gel method.Under the excitation of 325 nm,LTP-Ca3SiO4C12:xCe3+,xLi+,yMn2+,zEu2+ phosphors exhibit violet-blue emission,green emission and yellow emission simultaneously,and white light is obtained when x = 0.01,y = 0.07.Moreover,the emission intensity of Mn2+ is greatly enhanced by co-doping Ce3+ ions in Ca2.91SiO4Cl2:0.01Ce3+,0.00Li+,0.07Mn2+ phosphors,which is related to energy transfer process between Ce3+and Mn2+.The emission intensity of Mn2+ and Ce3+is greatly enhanced by co-doping Eu2+ ions in Ca2.91SiO4Cl2:0.01Ce3+,0.01Li?,0.07Mn2+ phosphors.(3)Energy transfer and photoluminescence properties between Bi3+ and Eu3+/Eu2+ in Ca3SiO4Cl2:Bi3+,Li+,Eun+samples prepared by sol-gel method are studied.Under the excitation of 327 or 365 nm,the Ca3SiO4Cl2:xBi3+,xLi+,yEun+ phosphors only show an intense green emission,while under the excitation of 264 nm violet-blue emission(Bi3+),green emission(Eu2+)and red emission(Eu3+)are observed,and the phosphor can emit white light when x = 0.01,y=0.002 with the color coordinate(0.312,0.328).These results indicate that the as-prepared Ca3 SiO4Cl2:Bi3+,Li+,Eu2+,Eu3+ phosphors can act as color-tunable and silgle-phase white emission phosphors for potential applications in UV-excited white LEDs.