Photoluminescence properties of Na(Sr,Ca)VO4:Eu(3+) phosphors.

Eu(3+)-activated novel alkaline earth metal (Sr and Ca) vanadate phosphors, Na(Sr(0.97-x), Ca(x))VO4:Eu0.03(3+) (x = 0 to 0.97) has been successfully synthesized using solid state reaction method and characterized by XRD, XPS, FE-SEM, luminescence (PLE, PL and CIE coordinate) and decay rate measurements as a function of Ca ion concentration. Phosphors show a broad excitation band (monitored for (5)D0 --> (7)F2 transition of Eu(3+)) in the 230-430 nm wavelength regions which make them highly suitable for LED chips. Material gives strong emission of Eu(3+) ion (λex = 323 nm) and intensity of this emission increases with increase in the doping concentration of Ca ions until a maximum is reached for Na(Sr0.22, Ca0.75)VO4:Eu0.03(3+) (x = 0.75) phase phosphor. The intensity ratio of (5)D0 --> (7)F2 to (5)D0 --> (7)F1 transition (monochromaticity, R) suggest that local symmetry around the Eu(3+) ion increases with increase in Ca ion concentration, which is responsible for enhanced emission.