| Summary: | 碩士 === 國立交通大學 === 應用化學系 === 89 === Phosphors with MS (M = Ca, Sr) as host lattice have been commonly utilized in the cathode ray tube and electroluminescence displays. However, reports regarding wet-chemical synthesis of MS phosphors have been rarely reported as compared to that from solid-state routes and the rationalization can presumably be attributed to the formation of stable metal sulfates and sulfites in aqueous solutions. We have synthesized the phosphors of MS phases by chemical colloid and microemulsion methods, respectively, and investigated the dependence of synthetic methodology on microstructure and luminescent properties of both pristine and rare-earth-activated MS phases.
In addition, to investigate the luminescence of rare earth-activated alkaline sulfide phosphors we have prepared three series of MS:1%A (M = Ca, Sr; A = Ce3+, Eu3+, Sm3+) phosphors. As indicated by photoluminescence (PL) spectra, the emission wavelength (lem) attributed to the 5d → 4f transition of Ce3+ was found to exhibit an apparent blue shift when x increases from 0 to 1.0 for the series of (Ca1-xSrx)S:Ce3+ (0 < x < 1) phases. This observation can presumably be rationalized by the weakening of crystal field that was experienced by Ce3+ luminescence center when Sr2+ content increases.
The emission of CaS:Eu was found to exhibit a red emitting band that consists of line emissions attributed to Eu3+ in the red region and a band emission attributed to Eu2+ in the blue-green spectral region. Furthermore, the both CaS:Sm3+ and SrS:Sm3+ were found to be orange-emitting due to 4f → 4f transition regardless of the type of host lattice, which was attributed by the shielding effect of 4f electrons by outer 5d and 6s shells.
To stabilize metal sulfide particles, we have attempted to carry out the passivation of CaS and SrS by coating the phosphor surface with poly(methylmethacrylic acid) (PMMA) and, however, the crystallinity and PL intensity were found to deteriorate for passivated MS and MS:A phosphors.
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