Study On Preparation And Luminescent Properties Of Li₂ZnSiO₄ Based Red Luminescent Materials

Li2ZnSiO4:RE3+(RE= Eu,Sm) and Li3Zn0.5SiO4:RE3+(RE= Eu,Sm) red luminescent materials were prepared by sol-gel method,and characterized by X-ray diffraction patterns(XRD), scan electron microscopy (SEM), infrared spectrometry(IR)and Photoluminescence spectrum (PL), and their properties, such as crystal structure, shape, luminescent properties, site occupations, critical quenching concentrations and their interactions of doped phosphors and so on, were also investigated.The red phosphor of Li2ZnSiO4:Eu3+ was synthesized by sol-gel method. The sample belongs to orthorhombic crystal system which is ellipsoid-liked, and the size of particles is about 2μm. The excitation spectra of the sample consist of O2-â†'Eu3+ charge transitions and Eu3+ ion excitation peak. Under ultraviolet excitation at a wavelength of 395 nm, the sample gives a red luminescence that is attributed to the transition 5D0â†'7F2 of Eu3+, and the maximum emission peak is at 613 nm. The luminescence intensity firstly increases and then decreases with increasing Eu3+ doping concentration. The optimal content of Eu3+ is about 3.5%,and H3BO3 is 3%, then the luminescence intensity of samples is better.The luminescent materials Li2ZnSi04:Sm3+ was obtained with Sm3+ as the activator. the sample belongs to orthorhombic crystal system which is columnar particles. The emission spectrum consists of four emission bands under excitation at 408 nm, The emission peaks are located at 566 nm,604 nm,651 nm and 710 nm, corresponding to the typical transitions of Sm3+ 4G5/2â†'6HJ (J=5/2,7/2,9/2,11/2),and the strongest one is at 604 nm. It is a very appropriate red emitting phosphor for white light-emitting diodes. The optimal content of Sm3+ is about 2.5%. Use H3BO3 as a flux and it also can improve the luminescence intensity of samples, and its optimum amount is 3%.The Li3Zn0.5SiO4:Eu3+ red phosphor was prepared by a sol-gel method. The sample is tetragonal structure whose space group is Pmnb(62). The emission spectrum excited by 395 nm or 465 nm, showed strong red emission peak at 613 nm that due to 5D0â†'7F2 of Eu3+. The doping concentration of Eu3+ is closely related to the photoluminescence intensity. Within a certain range, the emission intensity increases with increasing Eu3+ proportion. The optimal Eu3+ doping mole fraction is 5%The red phosphor of Li3Zn0.5SiO4:Sm3+ was obtained with Sm3+ as the activator.The sample belongs to tetragonal crystal system,and the space group is Pmnb(62). The maximum excitation peak of Li3Zn0.5SiO4:Sm3+ is 408 nm (6H5/2â†'4L13/2). Under ultraviolet excitation with a wavelength of 408 nm, the emission pectra of the sample consisted of characteristic transitions of Sm3+.The emission peaks are located at 566 nm(4Gs/2â†'6H5/2),601 nm(4G5/2â†'6H7/2),651 nm(4G5/2â†'6H9/2) and 710 nm(4G5/2â†'6H11/2), respectively. The phosphors exhibit a red performance at 601 nm. The effect of the doping amount of Sm3+ on the luminescence properties of Li3Zn0.5SiO4:Sm3+ was investigated. When Sm3+ doping concentration increases, the luminescence intensity firstly increases and then decreases. The optimal content of Sm3+ is about 3%.