Red emission of Praseodymium ions (Pr ³⁺)

English: Red glowing phosphors were prepared by adding Pr3+ ions as activators to several oxide host matrixes; CaTiO3, LaTaO4, YTaO4, and GdTaO4. The perovskite CaTiO3:Pr3+ compound is a phosphor that glows with a single red emission around 613 nm at room temperature upon irradiation with UV light of 230 – 360 nm wavelengths or an electron beam. The source of the single red emission is the intervalence charge transfer between Pr3+ and Ti4+ ions, which opens up a channel to completely depopulate the 3P0 state, by populating the 1D2 state. This leads to a dominant emission coming from the 1D2 → 3H4 transition. The dynamics of Pr3+ in YTaO4, LaTaO4, and GdTaO4 have not been explored excessively, and the resulting emission of these compounds doped with Pr3+ comes from both 3P0 and 1D2 states of Pr3+. The compounds were prepared by solid state reaction at 1200 oC and CaTiO3 was prepared by directly firing TiO2 (Anatase phase) and CaCO3 for 4 hours. The compound was doped with several mol% concentrations of Pr3+ from PrCl3 compound to optimize the output emission intensity. The rare-earth tantalate phosphors were prepared by directly firing Ta2O5 with Y2O3, La2O3, or Gd2O3 for 4h to obtain LaTaO4, YTaO4, and GdTaO4 respectively. The tantalates were doped with 0.5 mol% concentration of Pr3+ from PrCl3 and the synthesis was carried through in the presence of 30 wt% Li2SO4 flux agent. The role of the flux agent in this instant was to increase the reaction rate by acting as an intermediate that converts the reagents to reactive species, lower the reaction temperature required for the final compound to form and to facilitate crystallinity and to control particle sizes. The phase of the phosphor compounds was identified by using X-ray diffraction (XRD, Bruker AXS D8 Advance). The XRD patterns of CaTiO3 with different Pr3+ concentrations match that of the standard orthorhombic CaTiO3 (JCPDS card no. 22-0153). The XRD patterns of LaTaO4, YTaO4, and GdTaO4 with 0.5 mol % of Pr3+ s
National Research Foundation (NRF)