Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Applied Physics | en_US |
| dc.creator | Li, Hiu-ling | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/5671 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | - |
| dc.rights | All rights reserved | en_US |
| dc.title | Luminescence of phosphors based on novel oxides for field emission display | en_US |
| dcterms.abstract | This thesis presents studies on the synthesis, structural and optical characterization of rare-earth doped tungstates and binary oxide phosphors. Photoluminescence (PL) and low-voltage cathodoluminescence (CL) are used to investigate these promising phosphors for use in field emission display. The imperfection performance of sulfide-base phosphors has motivated us to investigate the more chemically and physically stable oxide-based phosphors. In our work, a variety of properties of the phosphors were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, low-voltage CL, PL spectra and lifetime. In our work, the luminescent properties of BaWO₄-based and ZnWO₄-based phosphors were investigated. Rare-earth ions (Eu³⁺ , Tb³⁺ , Tm³⁺) doped BaWO₄phosphors were prepared by a polyol-mediated method. Spherical morphology of the scheelite-structured particles was observed. While excited by ultra-violet (UV) light or low-voltage electron beam, red, green and blue emissions were observed in Eu³⁺, Tb³⁺ and Tm³⁺ doped phosphors, respectively. These emissions are attributed to the characteristic intraconfigurational 4f transitions in Eu³⁺, Tb³⁺ and Tm³⁺. Among them, the luminance of BaWO₄: Tb³⁺ was as high as 4866 cd/m² under excitation of electron beam (4.5 kV). The investigation on the chromaticity of BaWO₄: Tm³⁺ indicated that it had extremely high color purity (97%) and showed its potential as a promising blue-emitting phosphor. For the Eu³⁺ doped BaWO₄, very high intensity ratio of ⁵D₀ → ⁷F₂and ⁵Do → ⁷F₁transitions (R-value) indicates that Eu³⁺ ions may locate at a crystallographic site without inversion symmetry. Wolframite nanostructural ZnWO₄and ZnWO₄: Eu³⁺ were synthesized by refluxing in a water solution and followed by annealing at different temperatures. Different colors of emission were observed from the ZnWO₄- based phosphors. Blue-green CL emission of the annealed ZnWO₄is attributed to the highly emissive WO⁶⁻₆ ion complex. As-synthesized and annealed ZnWO₄: Eu³⁺ phosphors exhibit red and white emissions, respectively. The dynamic of emissions between WO⁶⁻₆ ion complex and Eu³⁺ ions with increasing annealing temperature were discussed. Luminescence of binary oxides was also studied in this work. A urea precipitation method was used to synthesize nanostructural ZrO₂: RE³⁺ (RE=Eu, Tb, Tm) phosphors. The characteristic red-green-blue (RGB) emissions of the rare earth ions were observed in the PL spectrum. Comparing to BaWO₄: Eu³⁺, ZrO₂: Eu³⁺ phosphor has a relatively small R-value, which indicates that Eu³⁺ ions may be distorted slightly and occupy a site without inversion symmetry. Similar result was observed in the CL spectrum. Regarding the Tm³⁺ doped ZrO₂, both emissions from defects of ZrO₂and Tm³⁺ ions was observed; however, such emission was observed in CL. Intrinsic emission in ZnO was also studied via PL and CL. Different morphologies of ZnO particles were synthesized by a hydrothermal method. Defect-related emission of the ZnO particles as a function of crystal size and morphology was discussed. | en_US |
| dcterms.extent | x, 90, xii leaves : ill. (some col.) ; 31 cm. | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2009 | en_US |
| dcterms.educationalLevel | All Master | en_US |
| dcterms.educationalLevel | M.Phil. | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.LCSH | Phosphors. | en_US |
| dcterms.LCSH | Luminescence. | en_US |
| dcterms.LCSH | Metallic oxides | en_US |
| dcterms.LCSH | Field emission | en_US |
| dcterms.accessRights | open access | en_US |
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|---|---|---|---|---|
| b2343000x.pdf | For All Users | 14.64 MB | Adobe PDF | View/Open |
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