Study On Preparation And Characterization Of Ce～(3+) Codoped LaPO₄: (Tb～(3+), Eu～(2+))

Our main purpose is to get Ce³⁺ co-doped LaPO₄:(Tb³⁺, Eu²⁺) by homogeneous precipitation synthesis method and combustion synthesis method in this thesis. The prepared phosphors have strong photoluminescence, giving strong blue and green emission respectively. In this thesis, we characterized the phase, morphology and structure of phosphors with some methods in detail, such as DTA FT-IR XRD TEM UV-Vis. Then we draw on some conclusions as the following:In a new aqueous system, sodium tripolyphosphate was used as a source of orthophosphate ions and a stabilizing agent. Lanthanum phosphate use as the matrix, co-doped with the rare-earth ions. After being centrifuged and dried, the precursor was obtained. The precursor come about complex physical and chemical reaction during annealing on the precursor, which result in the decreasing of content of hydroxyl group in the precursor and the particles were aggregated and the size was increased. The matrix crystal occurred phase transition at 300 ℃, which convert from Rhabdophane to monazite phase. The matrix LaPO₄ has no absorb to UV light. The UV absorption peak of phosphors all assign to 4f-5d bands of the cerium. The PL properties of phosphors are changeable with the production conditions, such as annealing temperature, annealing times, etc. PL analysis shows that the activated centers in the phosphors are Tb³⁺, excitation spectra of phosphors was shown the peaks of 260nm in the UV region, and emission spectra of phosphors was nearly at 543nm. Otherwise, Ce³⁺ can sensitize luminescence of Tb³⁺ in the phosphors, the energy transition mechanism between activated centers and sensitizer is dipole-dipole action. The syntheses conditions have been confirmed by contrasting PL intensity, the sintering temperature and time is about 900℃ and 2 hours, respectively.A new luminescent material -LaPO₄ doped with Eu²⁺ was prepared by combustion method. The as-synthesized phosphors have characteristic of strong blue emission, which the main peak is nearly at 423nm. The sizes of obtained particles were in nanometer scale and the nanoparticles disperse uniformly. XRD analysis shows that the phase of samples is very pure,...