Synthesis, structural, photoluminescence, and EPR analysis of far red emitting Ca3La2W2O12:Mn4+ inorganic phosphor for applications in plant-growth LEDs

This study explores the structural and optical properties of Mn4+ doped Ca3La2W2O12 phosphor. It also investigates the incorporation of Mn4+ ions for deep red emission and electron paramagnetic resonance (EPR) analysis. The phosphors were synthesized using the sol-gel method, and their properties were thoroughly examined using a combination of X-ray diffraction (XRD), Fourier transform infrared (FT-IR), photoluminescence (PL), and EPR technique. The XRD analysis provided insights into the phase purity, and constituents of the synthesized samples. Under 345 nm excitation, we observed far red emission at 705 nm, with the highest emission intensity occurring at a concentration of 0.0025 mol of Mn4+ metal ions in the host matrix. Concentration quenching was observed due to dipole-quadrupole interactions. The CIE chromaticity coordinates confirm far red region emission, and the estimated correlated color temperature (CCT) suggests that these phosphors can be used for bright illumination. Concurrently, the EPR examination also confirmed the presence of Mn4+ ions in the host matrix and showed the effect of variation on Mn4+ concentration in the EPR spectroscopy measurements. Furthermore, the electron paramagnetic resonance analysis demonstrated a distinctive six-line spectrum with a g-factor of approximately 1.98, indicating the presence of paramagnetic Mn4+ ions. This primary line was accompanied by a broader resonance with a linewidth of 950 Gauss, partially overlapping the six-line spectrum. The initial investigation indicates that this far red emitting phosphor can be applied to plant-growth LEDs.