Vol. 7, Issue 2, Part C (2025)

This study presents a facile, cost-effective, and scalable one-step wet chemical synthesis method for preparing KBiF₄:Eu³⁺ nanophosphors, with a focus on the systematic characterization of their structural, morphological, and optical properties.
The structural phase and crystallinity of the synthesized samples were confirmed using X-ray diffraction (XRD), revealing a well-defined tetragonal KBiF₄ structure with no secondary phases. The successful incorporation of Eu³⁺ ions into the host lattice was validated by Rietveld refinement and the slight shift in peak positions due to the ionic radius mismatch. Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of characteristic Bi-F and K-F vibrational modes, while energy-dispersive X-Ray Spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) provided evidence for the uniform elemental distribution and the oxidation state of Eu³⁺ ions, respectively.
Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed nanocrystalline morphology with particle sizes ranging between 40-80 nm, exhibiting spherical to irregular shapes. The small particle size and uniform dispersion are indicative of the efficacy of the one-step wet chemical method in producing homogeneous nanophosphors.
Optical characterization was carried out using photoluminescence (PL) spectroscopy. Under excitation at 394 nm (corresponding to the ⁷F₀ → ⁵L₆ transition of Eu³⁺), the emission spectrum exhibited sharp, intense red emissions centered at 612 nm, associated with the ⁵D₀ → ⁷F₂ electric dipole transition of Eu³⁺ ions. The emission intensity showed a strong dependence on Eu³⁺ doping concentration, with an optimal doping level observed at 5 mol%. Beyond this threshold, concentration quenching effects became prominent due to cross-relaxation and non-radiative energy transfer mechanisms.
In conclusion, this work demonstrates that the simple one-step wet chemical route provides an efficient and low-temperature pathway for synthesizing high-quality KBiF₄:Eu³⁺ nanophosphors. The method is not only scalable but also environmentally benign, avoiding high-temperature sintering and complex processing steps. The resulting material exhibits excellent crystallinity, strong red luminescence, and thermal robustness, highlighting its potential in advanced photonic and optoelectronic applications.