Synthesis and Characterization of Rare Earth Doped Molybdate and Tungstate Phosphors for Lighting Applications

Abstract

i newlineABSTRACT newlineIn this research work, viable routes such as solid-state reaction method (SSR), hydrothermal method, and pulsed laser deposition technique (PLD) have been adopted for the preparation of lanthanide ion-doped molybdate and tungstate based phosphors which have wide applications in WLEDs, display devices, and solid state lighting applications. The Ln3+ doped visible light emitting Ca0.5Y(MO4)2 (M = Mo, W) phosphors were successfully synthesized at 900oC for 3 h by solid-state reaction method. The obtained color chromaticity coordinate values for Ln3+ doped Ca0.5Y(MO4)2 (M = Mo, W) phosphors are in agreement with NTSC standard values. Significantly, luminescence properties were enhanced by the presence of alkali metal ions which are suitable for solid state lighting applications. Self-assembled bi-pyramid-shaped structures of Ca0.5Y(MO4)2:Ln3+ (M= Mo, W; Ln = Pr, Sm, Eu, Tb, Dy, Yb/Er, Yb/Tm, Yb/Ho) 3D architectures were successfully synthesized by using Na2EDTA based hydrothermal method under optimized experimental conditions. The crystal structure, 3D surface morphology, size and elemental distribution were performed. The up/down-conversion luminescence properties, photophysical parameters, decay time, and photometric characteristics of Ca0.5Y(MO4)2:Ln3+ (M = Mo, W) phosphors were studied. The as- synthesized phosphors are co-doped with alkali metal ions and charge compensation effect was studied. Nano-sized Ca0.5Y(MO4)2:Ln3+ (M = Mo, W; Ln3+ = Eu, Tb, Dy, Yb/Er) thin film phosphors were deposited on quartz substrates by pulsed laser deposition technique using Nd-YAG laser source. The deposition was performed in an ultra-high vacuum (UHV) with an oxygen back pressure of 300 mTorr. The as-deposited thin films could serve as an excellent material for electro/cathodo-luminescence devices and display applications. newline