Optical properties and Judd-Ofelt analysis of Dy³⁺ doped CoAl₂O₄ nanocrystals

CoAl₂O₄:xDy³⁺ nanocrystals (x = 0, 0.1, 0.5, 1.0, and 3.0 mol%) with spinel structures were prepared using the co-precipitation method. The crystal structure, optical properties, and presence of elements were respectively analyzed using X-ray diffraction, photoluminescence excitation, photoluminescence spectra, luminescence lifetime, and X-ray photoelectron spectroscopy. The influence of temperature on material fabrication was studied using differential scanning calorimetry and thermogravimetric techniques. The color characteristics of Dy³⁺ luminescence in the CoAl₂O₄ host were evaluated using CIE chromaticity coordinates and correlated color temperature. For the first time, the electronic dipole transitions in the photoluminescence excitation spectra were used to calculate the optical parameters of Dy³⁺ ions in the CoAl₂O₄ host using Judd-Ofelt theory. The Inokuti-Hirayama model was used to explain the energy transfer process between Dy³⁺ ions, the main interaction mechanism, and energy transfer parameters for the luminescence of Dy³⁺ ions.