Photoluminescence, Judd–Ofelt analysis and photometric characterization of Eu3+ activated Ca0.5Gd(WO4)2 red phosphor

The red emitting Ca 0.5 Gd(WO 4 ) 2 :Eu 3+ was synthesized by a solid-state reaction method. X-ray diffraction patterns were used to characterize crystal structure as well as phase purity. The results suggest that the as synthesized powder phosphor possess scheelite crystal structure with tetragonal symmetry along with the space group of I 4 1 /a. SEM studies reveal that the as synthesized sample show polyhedral morphology with particle size of 5.5 µm. Photoluminescence excitation spectrum depicts that a broad band (from 200 to 300 nm) centered at 242 nm is attributed to the ligand to metal charge transfer transition of WO 4 2− and three intense with sharp absorption bands (observed at 394, 464 and 535 nm) are designated as f–f electronic transitions of Eu 3+ . Photoluminescence emission studies indicate that, under 394 nm UV excitation, a hypersensitive red emission was observed at 617 nm due to the transition from upper 5 D 0 level to the 7 F 2 lower level of Eu 3+ ion. The spectroscopic behaviour of the as synthesized phosphor Ca 0.5 Gd(WO 4 ) 2 :Eu 3+ was determined using Judd–Ofelt theory. The CIE color coordinates, colour correlated temperature and luminous efficacies of radiation were estimated. The as obtained results indicating that the Ca 0.5 Gd(WO 4 ) 2 :Eu 3+ red phosphor is most suitable for solid state lighting applications.