Effect of Eu3+ doping on the structural, optical, and photoluminescent properties of LiGa5O8 phosphor

Abstract

This study reports on the synthesis and characterization of a series of lithium gallate (LiGa₅O₈) phosphors doped with varying concentrations of Eu³⁺ ions. X-ray powder diffraction analysis confirmed the synthesis of the cubic phase of LiGa₅O₈, with additional peaks corresponding to Eu₂O₃ at higher dopant concentrations. Rietveld refinement confirmed the formation of a spinel-structured host with a space group of P4₃22. Ultraviolet-visible spectroscopy was used to analyze the absorption properties of the phosphor material and estimate the bandgap for all synthesized samples, which ranged from 4.75 to 4.95 eV, indicating the formation of a wide bandgap semiconductor stable at room temperature. Morphological and compositional analysis, along with surface mapping, were conducted using field emission scanning electron microscopy, energy dispersive electron spectroscopy, and time-of-flight secondary ion mass spectroscopy. X-ray photoelectron spectroscopy provided insights into the crystal structure and revealed the presence of oxygen vacancies and some other crystal defects. Photoluminescent properties were examined through photoluminescence excitation and emission spectra for all doped samples. Notably, samples doped with 6 and 7 mol% Eu³⁺ displayed a prominent excitation peak at 247 nm corresponding to the presence of Eu₂O₃, while the remaining samples exhibited characteristic Eu³⁺ excitation. Lifetime measurements for both excitation wavelengths showed decay times in the millisecond range. The emission color of all samples resided within the red region of the electromagnetic spectrum, boasting remarkable color purity. The results suggest that this material has potential as a red light-emitting component for LED applications.