Recently, rare earth doped vanadate phosphors have paid considerable attention owing to their long-wavelength excitation properties, which enable their use in LEDs, fluorescent lamps, and flat panel displays. The luminescence performance of a material can be enhanced significantly by the suitable selection of host material. Since the white light-emitting diodes (WLEDs) gaining much more attention. Generation of the white light by combining an ultraviolet (UV) LED and appropriate phosphors is most desirable. Hence, it is essential to develop efficient phosphors to convert the near-UV pump light with a range of 300-400 nm into the visible wavelength. In order to fabricate excellent WLEDs, the excitation wavelength of the red phosphors should match the emission of the near UV-LEDs (350-410 nm) or blue LEDs (440-470 nm). Therefore, the phosphor materials play an important role in WLEDs. Most vanadates exhibit intense broadband emission from 400 nm to 700 nm under UV excitation because of tetrahedral VO4 with Td symmetry. The broadband emission spectra of vanadate phosphors are due to the charge transfer (CT) of an electron from the oxygen 2p orbital to the vacant 3d orbital of V5+ in tetrahedral VO4 with Td symmetry. The luminescence is attributed to the 3T2→1A1 and 3T1 →1A1 transitions. Nanocrystalline high-quality Ca3-3x/2(VO4)2:xEu (0.01≤x≤0.09) phosphors are successfully synthesized by the solution combustion method. The crystal structure, particle size, and photoluminescence (PL) properties of the annealed Ca3-3x/2(VO4)2:xEu phosphors are studied. The impact of concentration and temperature on the luminescence properties of the Eu3+ activated Ca3-3x/2(VO4)2:xEu (0.01≤x≤0.09) phosphors are studied. The characteristic PL peaks caused by the 5D1 → 7F1, 5D1 → 7F2, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, and 5D0 → 7F4 transitions of Eu3+ are observed at 537, 556, 592, 613, 654, and 701 nm, respectively. The Ca3-3x/2(VO4)2:xEu nanophosphors show the strongest red emission at 613 nm under ultraviolet (UV) excitation because of the charge transfer state of VO43- and f–f transitions of Eu3+ ions. In this study, the Ca3-3x/2(VO4)2:xEu phosphors can be used as red nanophosphors for white light-emitting diodes (LEDs).

Dr. K.N. Shinde has completed his Ph. D. from R.T.M. Nagpur University, Nagpur, India and postdoctoral studies from Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul, South Korea. At present, He is an assistant professor and the Director of R & D at N.S. Science and Arts College, Bhadrawati, India. He has published more than 50 papers in reputed journals and serving as an editorial/reviewer of international journals. His research interests are synthesis of nanocrystalline materials and exploring novel materials and study their PL properties. He published 02 books and contributed one chapter in international repute publications. One Korean patent is on his credit. He is an active member of International centre for diffraction data (ICDD), USA.