Abstract
The rapid change in technological influence have seen sodium mixed sulphate phosphors made way in the new development of optoelectronics. Na6Mg(SO4)4 and Na2Ca(SO4)2 nanophosphors were synthesized using chemical combustion method at a temperature of 5800C, with a single dope concentration of (1.0mol%) of Sm3+ and Eu3+. These nanophosphors were co-doped with Na6Mg(SO4)4: Sm3+(1.0mol)/xEu3+ (where x= 0.5mol%, 1mol% and 1.5mol%) and Na2Ca(SO4)2:Sm3+(1.0mol%)/xEu3+(where x= 0.5mol% - 1.5mol%). The structural, morphological and optical properties of prepared nanophosphors were studied using X-ray diffraction (XRD), Field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) techniques. The XRD results confirmed that the crystal structure of both compounds exhibited diffraction peaks of a monoclinic phase with different space groupings. The surface morphological studies showed that the addition of impurities into both Na6Mg(SO4)4 and Na2Ca(SO4)2 phosphors can have an impact on the variation of particle sizes and shapes through their agglomeration effect. The luminescence properties were studied using the DRS spectra measured from 250 nm -2250 nm. To investigate photoluminescence (PL) features of Sm3+ and Eu3+ ions, all series of Na6Mg(SO4)4 and Na2Ca(SO4)2 nanophosphors were excited with 404 nm and 395 nm wavelengths respectively. An improved colour tenability was witnessed in Na6Mg(SO4)4 nanophosphor series and supported by results of the lifetime decay curve and energy transfer mechanism from Sm3+ to Eu3+. The CIE color images were found to be the tuning of pure red color emission for increasing of Eu3+ ion concentration in both Na6Mg(SO4)4 and Na2Ca(SO4)2 nanophosphors. The results of this study show that Sm3+ and Eu3+ co-doped Na6Mg(SO4)4 and Na2Ca(SO4)2 materials are potential candidates for efficient orange and red emitting luminescent phosphors for application in white LEDs.
M.Sc. (Nanoscience)