Evaluating NaREMgWO6 (RE = La, Gd, Y) Doubly Ordered Double Perovskites as Eu3+ Phosphor Hosts

Abstract

Three doubly ordered double perovskites NaREMgWO₆ (RE = La, Gd, Y) have been synthesized via traditional solid-state methods, doped with Eu³⁺, and characterized to evaluate their promise as Eu³⁺ phosphor hosts. NaYMgWO₆, a new member of the family, was found to crystallize in the P2₁ space group and is isostructural with NaGdMgWO₆. Emissions characteristic of Eu³⁺ ions (⁵D₀ → ⁷F_4,3,2,1,0) were observed, with the most intense transition being the ⁵D₀ → ⁷F₂ transition near 615 nm. Substitution of Eu³⁺ onto a more compressed RE site in the NaY_1-xEu_xMgWO₆ and NaGd_1-xEu_xMgWO₆ hosts results in a blue shift of the charge-transfer excitation band and an increase in the intensity of the ⁵D₀ → ⁷F₂ transition compared to NaLa_1-xEu_xMgWO₆. All of the hosts can incorporate high concentrations of Eu³⁺ before concentration quenching is observed. When the rare-earth ion is either Gd³⁺ or Y³⁺, good energetic overlap between the Eu³⁺ charge-transfer band and the absorption of the host lattice results in sensitization and energy transfer from the perovskite host lattice to the Eu³⁺ activator sites. These hosts display comparable if not better luminescence than Y₂O₃:Eu³⁺, a commonly used commercial standard, demonstrating their promise as red phosphors.