Photoluminescence Properties of LaNbO₄:Eu³⁺ Phosphors Prepared by a Solid-state Reaction

Abstract

LaNbO₄: Eu³⁺, Dy³⁺ phosphors prepared by a solid-state reaction were characterized by X-ray diffraction (XRD) and photoluminescence spectra. The XRD patterns of LaNbO₄ doped with Eu³⁺ and Dy³⁺ essentially agreed with those of LaNbO₄, indicating that the doping of Eu³⁺ and Dy³⁺ ions does not change the host crystal structure. From the strong emission peak at 615 nm corresponding to ⁵D₀→⁷F₂, Eu³⁺ was thought to occupy the sites with lower symmetry. In addition to the usual emission transitions from ⁵D₀, the emission transitions from the higher ⁵D₁ and ⁵D₂ levels were observed. The transitions from the higher levels were explained by the reduced multi-phonon relaxation from the ⁵D₁ and ⁵D₂ to the lowest excited level ⁵D₀ due to the lower vibrational energy of NbO₄^3-. The relative emission intensity of the ⁵D₀→⁷F₂ transition decreased with an increase in the amount of Dy³⁺. This was attributed to energy transfer to the Dy³⁺ ions.