Structural, optical, and color-tunable luminescence of Dy3+-doped Ca3Ga4O9 phosphors for white-light emitting diode applications

Abstract

A series of single-phase Dy³⁺-activated Ca₃Ga₄O₉ phosphors were synthesized using a high-temperature solid-state reaction method for white light. The phase purity and crystal structure of the synthesized phosphors were verified through X-ray powder diffraction patterns. Surface characteristics and elemental composition were analyzed using field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. X-ray photoelectron spectroscopy was used to validate the elemental oxidation states and gain insights into the influence of structural properties. The bandgap of the synthesized phosphor and its doping variation were investigated through diffuse reflectance spectra. The bandgap value for the undoped phosphor was determined to be 4.57 eV, exhibiting a slight decrease to 4.45 eV as the doping concentration was increased to 2 mol%. An analysis was conducted on the photoluminescence phenomenon by recording the excitation and emission spectra. In addition to the vibrant blue light emitted by the host materials, fundamental emission peaks corresponding to Dy³⁺ [⁴F_9/2 → ⁶H_J (J=15/2, 13/2, 11/2, 9/2)] were also observed. The emission phenomenon was further verified by recording the Cathodoluminescence spectra, which closely resemble the recorded emission spectra. Judd-Ofelt analysis showed that the Judd-Ofelt intensity parameter Ω₂ is more responsive to the changes in the ligand environment. Chromaticity analysis indicated the proximity of the International Commission on Illumination coordinates for 1 mol% (0.3259, 0.3475) to the standard white point (0.3333, 0.3333), yielding a correlated color temperature of 5798 K. Thermal studies revealed that the synthesized phosphors exhibited excellent thermal stability up to 673.15 K, with an activation energy of 0.28 eV. All the experimental findings prove that the synthesized phosphor exhibits high potential and can prove to be as a proficient contender for white light applications.