Synthesis, luminescence and photometric characteristics of Ca_0.5La(MoO₄)₂:Ln³⁺ (Ln = Eu, Tb, Dy) phosphors

Ca_0.5La(MoO₄)₂:Ln³⁺ phosphors, where Ln = 4, 8, 12, 16, and 20 mol% of Eu, Tb, or Dy, were successfully synthesized by a conventional solid-state reaction method at 900 °C for 3 h. The Ca_0.5La(MoO₄)₂:Ln³⁺ phosphors exhibit a scheelite tetragonal crystal structure belonging to the I4₁/a space group. The strong absorption bands seen in Fourier transform infrared (FTIR) spectra confirm that F₂(ν₃) modes of vibration are IR active. The photoluminescence(PL) spectra reveal that, under optical excitation, the as-synthesized phosphors show high intensity narrow emission bands in the red (615 nm), and green (545 nm), and yellow (570 nm) regions for samples doped with Eu³⁺, Tb³⁺, and Dy³⁺ ions, respectively. The critical concentrations of Eu³⁺, Tb³⁺, and Dy³⁺ as dopants in Ca_0.5La(MoO₄)₂ were found to be 16, 12 and 12 mol%, respectively. Thereafter, concentration quenching effect occurred in the solid solutions. The fluorescence decay times for the major transitions of ⁵D₀ → ⁷F₂, ⁵D₄ → ⁷F₅, and ⁴F_9/2 → ⁶H_13/2 were estimated for different doping concentrations of Eu³⁺, Tb³⁺, and Dy³⁺ in Ca_0.5La(MoO₄)₂, respectively. To determine the color purity and emission quality of the phosphor, photometric parameters such as color chromaticity coordinates, color correlated temperature (CCT), color rendering index (CRI), and luminous efficacy of radiation (LER) were estimated using the spectral energy distribution functions of the Ca_0.5La(MoO₄)₂:Ln³⁺ phosphors. - Graphical abstract: Display Omitted - Highlights: • Single crystalline ceramic phosphor Ca_0.5La(MoO₄)₂:Ln³⁺ were successfully synthesized. • The phosphor exhibits scheelite tetragonal crystal structure with space group I41/a. • Luminescence properties as a function of Ln³⁺ ions concentration were discussed. • The photometric parameters of the phosphor were estimated