Preparation Of Rare Earth Doped Tungstate Luminescent Materials By Soft Chemical Method

Tungsten compound is a kind of important inorganic functional materials and has been widely used in the fields of photocatalysis, electrochromic, optochromic, gas sensors and so on. Due to its wide development foregrounds and the anticipative market potentials, the development of high-quality tungstate compound materials has attracted more and more attentions of researchers. Synthesis of double tungstate is mostly employed high temperature solid state method in current, but its reaction conditions are very harsh, so in this dissertation NaY (WO4)2:Eu3+ tunable phosphors were synthesized by soft chemical method.1. Eu3+ doped NaY(WO4)2 nano/micro crystals of different morphologies have been prepared by hydrothermal method and solvothermal method.2. The presence form of tungstate is determined by the pH value of the solution in the aqueous solution reaction systems. When the pH value is equal to 9, its presence form is WO42-.3. On the condition of pH=9, needle-like sphere, urchin-like, flake-flowers, needles-like, cauliflower-like, bow-like and peanut-like microcrystals were obtained in the different reaction systems (H2O, cetyl trimethyl ammonium bromide(CTAB)/H2O, sodium citrate/H2O, polyvinyl pyrrolidone(PVP)/H2O, sodium citrate/2-octanol, polyvinyl pyrrolidone(PVP)/2-octanol). Based on the detailed investigation on the influences of experimental parameters, the formation mechanism of different morphologies is proposed.4. Under the ultraviolet(UV) excitation, different molar ratio of R(Eu/Y) doped the phosphors emit multicolour light, blue(R=0), white(R=0.02), pink(R=0.04) and red (R=0.06) respectively. This result shows that it has potential applications as novel multi-purpose luminescent materials in the lighting and display areas. There are two linear excitation peaks at 395nm (near UV) and 465nm (blue light) in excitation spectrum. So it can be deduced that the phosphors are suitable for both the near UV (395nm) LED chips excited and blue (465nm) LED chips excited. After comparison, the urchin-like NaY(WO4)2:Eu3+ phosphor is the most effective luminescent crystals among the seven different morphologies of phosphors.