Synthesis And Properties Of Several Rare-Earth Phosphors

In this thesis,rare-earth luminescent materials based on Ca3Al2O6:Eu/Tb/Sm、La4SrO7:Eu/Sm/Tb、CaWO4:Eu,Tb were successfully synthesized by Pechini sol-gel method.And Na2Ca3A12F14:Ce/Tb/Eu were successfully synthesized by Hydrothermal method.The crystal structure,morphology and luminescent properties were investigated using X-rays diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)were used to characgterized the structures of the phosphors;scanning electronmicroscopy(SEM)was utilized to characterized the morphology;photoluminescence spectra(PL)were used to chareacterized the luminescent properties.The optimum annealing temperatures of Ca3Al2O6:Eu/Tb/Sm was 900 ℃,much lower than the traditional solid state method of 1350 ℃.The average grain size of as prepared phsophors is 1500 nm with an even size distribution.Exciation spectrum of Ca3A12O6:Eu is dominated by the 223 nm band originated from Eu-O charge transfer transition.Ca3Al2O6:Eu emission shows characterstic emission of Eu3+,dominated by electric dipole transition of 5D0-7F2 at 612 nm.The optimum doping concentration of Eu3+ is 5mol%.Exciation spectrum of Ca3Al2O6:Tb is dominated by the 223 nm band originated from 4fg-4f75d1 transition.Emission spectrum originated from 5D3,4-7FJ,,domimated by5D3-7F6 at 378 nm and 5D4-7F5 at 542nm.Optimum doping concentration of Tb3+ is 1 mol%.Ca3Al2O6:Sm is dominated by the 222 nm band originated from 6H5/2→4H7/2 transition.Emission spectrum is domimated by 4G5/2-6H7 at 605 nm.Optimum doping concentration of Sm3+ is 4 mol%.The optimum annealing temperatures of La4SrO7:Eu/Sm/Tb was 1150 ℃.Exciation spectrum of La4SrO7:Eu is dominated by the 223 nm band originated from Eu-0 charge transfer transition.La4SrO7:Eu emission shows characterstic emission of Eu3+,dominated by electric dipole transition of 5D0-7F2 at 622 nm.The optimum doping concentration of Eu3+ is 5mol%.Exciation spectrum of La4SrO7:Sm is dominated by the 222 nm band originated from 6H5/2→4H7/2 transition.Emission spectrum of La4SrO7:Sm is domimated by 4G5/2→6H7/2 at 608 nm.Optimum doping concentration of Sm3+ is 2 mol%.Exciation spectrum of La4SrO7:Tb is dominated by the 223 nm band originated from 7F→6D transition.Emission spectrum of La4SrO7:Tb is domimated by 5D4→7F5 at 541 nm.Optimum doping concentration of Tb3+ is 4 mol%.The optimum annealing temperatures of CaWO4:Eu,Tb was 1100 ℃.Exciation spectrum of CaWO4:Eu,Tb is dominated by the 256 nm band originated from W-O charge transfer transition.Emission spectrum of CaWO4:Eu,Tb is domimated by 5D0-7F2 at 615 nm.And Eu3+and Tb3+ have common characteristic emission peaks at 615 nm.In addition,Na2Ca3A12F14:Ce/Tb/Eu phosphors were synthesized by hydrothermal method.Na2Ca3Al2F14:Ce/Tb/Eu were synthesized at 200 ℃.Exciation spectrum of Na2Ca3A12Fi4:Ce is dominated by the 253 nm band originated from 4f1-5d1 transition.Emission spectrum of La4SrO7:Sm is domimated by 5d1-4f1 at 365 nm.Optimum doping concentration of Sm3+ is 4 mol%.Exciation spectrum of La4SrO7:Tb is dominated by the 248 nm band originated from 4f8-4f75d1 transition.Emission spectrum of La4SrO7:Sm is domimated by 5D4→7F5 at 540 nm.Optimum doping concentration of Tb3+ is 4 mol%.Exciation spectrum of La4SrO7:Eu is dominated by the 258 nm band originated from 2p-4f transition.Emission spectrum of La4SrO7:Sm is domimated by 5D0-7Fj at 585 nm.Optimum doping concentration of Eu3+ is 3 mol%.