Judd-Ofelt analysis and optical properties of Eu³⁺-doped GdPO₄ phosphors synthesized by combustion method

Abstract

The Eu³⁺-doped GdPO₄ nanoparticles were prepared via a straightforward combustion method using urea as fuel and nitrates as a precursor. X-ray powder diffraction patterns, infrared spectrum (IR), HR-TEM, photoluminescence (PL), phonon sideband and photoluminescence excitation (PLE) were researched. There is a phase transition from the hexagonal phase into the monoclinic phase when the calcined temperature is over 700 °C. All of phosphors have similar morphology and the average diameters for nanoparticles are 20-30 nm. Under the excitation at 273 nm, GdPO₄:Eu³⁺ powders showed red emission bands originating from the ⁵D₀-⁷F, (J=1, 2, 3 and 4) transitions of Eu³⁺. The orangered emission (⁵D₀-⁷F₁, transition) is dominated because the Eu³⁺ ions exist with inversion symmetry in the lattice. The study suggests that the optimal Eu³⁺ ions concentration is 5 mol%. In addition, the second order crystal field parameter (B₂₀) and the influence of concentration of Eu³⁺ ions on decay time are also mentioned, the intensity parameters (Ω₂,₄,₆) and quantum efficiency were determined based on Judd-Ofelt theory.