Photoluminescence properties of Tb~(3+) and Eu~(3+) ions co-doped SrMg_2La_2W_2O_(12) phosphors for solid state lighting applications

摘要

In this paper, we report a series of Tb~(3+) and Eu~(3+) activated SrMg_2La_2W_2O_(12) phosphors synthesized by the solid state reaction method. The structural and photoluminescence properties have been characterized and analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, photoluminescence and decay measurements. X-ray diffraction pattern confirms that the SrMg_2La_2W_2O_(12) powders were well indexed to orthorhombic structure (JCPDS card No. 35-0259). The excitation spectra monitored at 547 and 617 nm consist of a broad band in the region 250-370 nm pertaining to O ->W ligand to metal charge transfer transition and several narrow bands related to Tb~(3+) and Eu~(3+) ions absorptions, respectively. The emission spectra of singly Tb~(3+) and Eu~(3+) doped SrMg_2La_2W_2O_(12) phosphors consist of narrow bands from 4f-4f emission transitions of ~5D_4 and ~5D_0 excited levels to several lower lying levels of Tb~(3+) and Eu~(3+) ions, respectively. The emission color of phosphors doped with Tb~(3+) and Eu~(3+) ions has been changed by varying concentrations and excitation wavelengths to obtain white light emission. The Commission Internationale de L'eclairage (CIE) chromaticity coordinates and correlated color temperatures (T_(cct)) show that the SrMg_2La_2W_2O_(12):TbEu phosphors can be tuned to exhibit white light emission ranging from 450 to 750 nm, when they are excited by ultraviolet (UV) light.