Synthesis, characterization and optical properties of Na0.7K0.3Li3SiO4 phosphor doped with Ce³⁺ and Dy³⁺

Na₀._₇K₀._₃Li_₃SiO_₄ phosphors doped with Ce^³⁺ and Dy^³⁺ ions were synthesized in the present investigation using a microwave-assisted solution combustion synthesis method and subsequently underwent thermal treatment at 800°C. The synthesized material was analyzed using X-ray diffraction and scanning electron microscopy (SEM), while its photoluminescence properties were examined by excitation and emission spectroscopy at room temperature. X-ray diffraction (XRD) verified phase-pure orthorhombic crystal structures, characterized by space group I4₁/a and a crystalline size of 55.56 nm, as determined by the Debye-Scherrer formula. SEM images revealed numerous approximately spherical irregular particles, with an average particle size of 45 nm. Photoluminescence (PL) investigations revealed blue emission in Ce^³⁺-doped materials associated with 5d → 4f transitions and distinctive yellow and blue emissions in Dy^³⁺-doped samples resulting from ^⁴F_₉/₂ → ^⁶H_₁₁/₂ transitions. The optical band gap was determined via UV-Vis spectroscopy and Tauc plots, yielding values of 4.93 eV for Ce^³⁺-doped samples and 5.13 eV for Dy^³⁺-doped samples. These phosphors demonstrate favourable luminescent characteristics for ultraviolet-excited white LED applications.