Research On Synthesis And Properties Of Rare Earth Eu³⁺,Tb³⁺ Doped KLa（MoO₄）₂Phosphors

The white light emitting diodes (W-LEDs), as a new generation of light sources,have many advantages such as stability, high luminous efficiency, low powerconsumption, environment protection and long serving lifetime. In numerousphosphors materials, molybdates with scheelite structure have become the researchhot topic due to their good optical properties, chemical stability and physical stability.In order to obtain a higher efficiency white LED with an appropriate colortemperature and a higher color-rendering index, a new approach using near-ultravioletInGaN-based LED chip coated with blue/green/red tricolor phosphors was introduced.This thesis focuses on the molybdate to achieve high purity, good dispersion anduniform particle phosphor via the hydrothermal process, and research in luminescentproperties of rare ions relate to substrate structure and the morphology.(1) The red-emitting KLa(MoO4)2:Eu3+phosphor was prepared successfully viathe hydrothermal process, which was characterized by X-ray diffraction (XRD), fieldemission-scanning electron microscopy (FE-SEM) and photoluminescence (PL),respectively. The experimental results indicated that the pH values of the reactionsolution have important effects on the phase structures and the morphologies of theproducts. A crystallization pH value of7was able to synthesize high purity, gooddispersion and uniform particle phosphor. In addition, the possible formationmechanism for products with uniform sphere had been presented. This phosphor canbe effectively excited by charge-transfer band275nm, ultraviolet light395nm, bluelight465nm and emit red light616nm with line spectra. The optical propertiessuggest that KLa(MoO4)2:Eu3+is an efficient red-emitting phosphor for white LEDs applications.(2) Trivalent rare-earth (RE3+=Eu3+, Tb3+) ions activated KLa(MoO4)2microspheres have been synthesized at180oC via a facile hydrothermal route withoutusing any templates, surfactant, and other organic additives. X-ray diffraction (XRD),field emission-scanning electron microscopy (FE-SEM) and photoluminescence (PL)were employed to characterize the samples. It was found that the pH value in theinitial solution was responsible for crystal phase of final products. Furthermore, itclearly shows that the PL color can be tuned from green, blue, white and red-orangeby changing the doping concentration ratio of Eu3+and Tb3+ions. It was proved theenergy transfer mechanism is proven to be dipole-dipole interaction between Eu3+andTb3+ions.