SAIP 2011 Support
Synthesis and Characterization of Structural and Luminescent properties of long afterglow CaAl2O4: Eu2+, Nd3+, Dy3+ nano-scaled phosphors by solution – combustion technique.
Presented by Mr. Ali WAKO on 13 Jul 2011 from 11:30 to 11:45
Type: Oral Presentation
Track: Track A - Condensed Matter Physics and Material Science
<p>Long afterglow calcium aluminate phosphors doped with Eu<sup>2+</sup> and co-doped with Nd<sup>3+</sup> /or Dy<sup>3+</sup> (CaAl<sub>2</sub>O<sub></sub>4:Eu<sup>2+</sup>, Nd<sup>3+</sup>, Dy<sup>3+</sup>) were fabricated by urea-nitrate solution – combustion method at 500 °C. The effects of varying concentrations of Ca:Al and co-dopants molar ratio (Nd<sup>3+</sup>:Dy<sup>3+</sup>) on the structural and luminescent properties of the phosphor were investigated. It was observed that Ca:Al molar ratios greatly affect the crystalline structure of the material. The results of the X-ray diffraction (XRD) analysis reveal that the formation of several crystalline phases depends on the molar ratios of the host material. The peaks show the presence of other phases such as Ca<sub>3</sub>Al<sub>2</sub>O<sub>6</sub> and CaAl<sub>4</sub>O<sub>7</sub> but the predominant phase formed was that of CaAl<sub>2</sub>O<sub>4</sub>. As the concentration of Ca ions increase, the peak intensity increase which led to formation of monoclinic CaAl<sub>2</sub>O<sub>4</sub> as a single phase for the 1.5% Ca. However it was found that the crystalline structure is generally not affected by variation of the co-dopants concentration. PL studies revealed a general rise in intensity with increase in the mole ratio of Ca:Al . The highest PL intensity was observed with 1.5% Ca but was weak with 0.1% Ca. Also it is evident that as the fraction of Nd<sup>3+</sup> increase and that of Dy<sup>3+</sup> decrease proportionally good emission intensities are formed in the region 400nm-500nm at the ratio 1:1. The initial luminescent intensity and rate of decay vary from each other when co-doped with various proportions of Nd<sup>3+</sup> and Dy<sup>3+</sup>. Low Nd<sup>3+</sup> exhibited high initial luminescent intensity but low decay rate because of insufficient trap vacancies in the host matrix.
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