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Pycnometric and Spectroscopic Studies of Red Phosphors Ca2+(1-1.5x)WO4:Eu3+x and Ca2+(1-2x)WO4:Eu3+x,Na+x

  • Cho, Seon-Woog (Department of Materials Science and Engineering, Silla University)
  • 투고 : 2013.05.20
  • 심사 : 2013.06.27
  • 발행 : 2013.09.20

초록

Red phosphors $Ca_{(1-1.5x)}Eu_xWO_4$ and $Ca_{(1-2x)}Eu^_xNa_xWO_4$ were synthesized with various concentrations x of $Eu^{3+}$ ions by using a solid-state reaction method. The crystal structure of the red phosphors were found to be a tetragonal scheelite structure with space group $I4_1/a$. X-ray diffraction (XRD) results show the (112) main diffraction peak centered at $2{\theta}=28.71^{\circ}$, and indicate that there is no basic structural deformation caused by the vacancies ${V_{Ca}}^{{\prime}{\prime}}$ or the $Eu^{3+}$ (and $Na^+$) ions in the host crystals. Densities of $Ca_{(1-1.5x)}Eu_xWO_4$ were measured on a (helium) gas pycnometer. Comparative results between the experimental and theoretical densities reveal that $Eu^{3+}$ (and $Na^+$) ions replace the $Ca^{2+}$ ions in the host $CaWO_4$. Also, the photoluminescence (PL) emission and photoluminescence excitation (PLE) spectra show the optical properties of trivalent $Eu^{3+}$ ions, not of divalent $Eu^{2+}$. Raman spectra exhibit that, without showing any difference before and after the doping of activators to the host material $CaWO_4$, all the gerade normal modes occur at the identical frequencies with the same shapes and weaker intensities after the substitution. However, the FT-IR spectra show that some of the ungerade normal modes have shifted positions and different shapes, caused by different masses of $Eu^{3+}$ ions (or $Na^+$ ions, or ${V_{Ca}}^{{\prime}{\prime}}$ vacancies) from $Ca^{2+}$.

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피인용 문헌

  1. Effect of Zn2+ ions on the structure, morphology and optical properties of CaWO4 microcrystals vol.72, pp.3, 2014, https://doi.org/10.1007/s10971-014-3550-y
  2. (A = Ca, Sr; □ = vacancy) vol.44, pp.13, 2015, https://doi.org/10.1039/C5DT00022J
  3. Point Defects and Photoluminescence of Green Phosphors Ca(1-1.5x)WO4:Tbx3+ and Ca(1-2x)WO4:Tbx3+, Nax vol.23, pp.9, 2013, https://doi.org/10.3740/mrsk.2013.23.9.537