Synthesis And Characterization Of Nanosized Rare Vanadate And Rare Phosphate Luminescence Materials

Rare earthactivated LnVO4 and LnPO₄ phosphors have been attracting moreattention in recent years because of their high luminescent intensities and stabilityunder UV or VUVexcitation as comparison with the conventional phosphors. Dueto these advantages, the phosphors have been potential luminescent materials fornew flat displays, such as plasma display panel (PDP), field emission displays(FED).In this dissertation, nanocrystal rare earth orthovanadate were synthesized bymodified Pechini sol-gel and polyacrylamide gel method. The results indicatedthat grains with spherical morphology are homogeneous and well defined. Thegrain size is nearly 20nm. Further more, the samples prepared by these methodsdisplay strong luminescence intensity. At the same time, in order to attain higherquality phosphors, the model was built to improve synthetic routes. Theexperimental results show that the advantages of the improved method over othermethods include higher sample homogeneity, well dispensability and strongerluminescence.The spectral studies on nanosized YVO₄:Eu indicated that the FTIR bands ofnanocrystalline YVO4:Eu have a obvious blueshift as comparisons with bulksamples. But the luminescent spectra of nanocrystalline YVO₄:Eu are similar tothat of bulk samples. This suggests that the local symmetries in bothnanocrystalline and bulk phosphors are the same. In addition, by analyzingexcitation and emission spectra of thulium doped yttrium vanadate, we deducedthe mechanism of the energy transfer between vanadate host and thulium ions.Otherwise, the photoluminescence of nanocrystalline YVO4:TmxDy1-x wereinvestigated . By adjusting the ratio of Tm3+/Dy3+ a white light emission withexcellent color coordinates can be realized. Hexagonal CePO4 nanowire was prepared by a simple hydrothermal synthesisand monoclinic CePO4 nanowire was obtained by high heat treatment. Thedifferences between hexagonal and monoclinic CePO4 were investigated. Moreattentions were focused on the study of the luminescence of Dy3+in hexagonal andmonoclitic CePO4. LaPO4:Tm nanoparticls and nanowires were prepared by hydrothermalsynthesis and Pechini sol-gel methods respectively. The photoluminescence ofLaPO4:Tm with different shapes and phases was carefully studied and themechanismof the luminescence of monoclinic LaPO4:Tm was deduced.