Structural and photoluminescence behavior of thermally stable Eu3+activated CaWO4 nanophosphors via Li+ incorporation

Abstract We have studied the structural and photo physical analogue of Eu 3+ activated CaWO 4 nanophosphors via Lithium (Li +  = 2, 5 7 and 10 at.%) ion incorporation. As-prepared (APS) samples were annealed at 900 °C to eliminate unwanted organic moieties present in the sample and to improve crystallinity. The samples are characterized employing X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), UV-VIS spectroscopy, photoluminescence studies and lifetime decay studies. FTIR features an absorption band at ∼832 cm −1 , which correspond to its antisymmetric vibrations into O W O band in the WO 4 2− tetrahedron. CaWO 4 having the scheelite type structure with C 4h point group and I 4 1 / a space group. The surface morphology of the samples are studied with Scanning Electron Microscopy (SEM). Lithium Co-doped CaWO 4 :Eu 3+ nanoparticles show red luminescence because of strong host contribution and different energy transfer rates from host to Eu 3+ ions under 266 nm excitations. Lithium ion enhances the crystallinity and radiative transition rate thus results in higher emissive property. Calculated CIE co-ordinates of these Li + doped 900 °C annealed samples under 266 nm excitation is x = 0.65 & y = 0.34, which are closer to the standard of NTSC (x = 0.67 & y = 0.33). This material may be potential candidates for white light emitting diodes.