A comparative study of spectral and luminescent properties of Eu3+-doped cation-deficient perovskite phosphors

Abstract

Eu³⁺ is not only a major red-emitting activator, but also an excellent spectral probe ion. This work reports the Eu³⁺-sites and luminescence in the cation-deficient perovskite tungstates, A-site deficient SrLa₂(Mg₂W₂)O₁₂ [Sr_1/2□_1/2La(MgW)O₆] and B-site deficient Sr₂La₂(MgW₂)O₁₂ [SrLa(Mg_1/2□_1/2W)O₆]. The ⁷F₀→⁵D₀ excitation spectra of Eu³⁺ activators in two lattices were measured via pulsed dye laser. In SrLa₂(Mg₂W₂)O₁₂:Eu³⁺, there is only one ⁷F₀→⁵D₀ transition, which could be related to the Eu³⁺ center on La³⁺ sites; while, two ⁷F₀→⁵D₀ transitions in Sr₂La₂(MgW₂)O₁₂ indicate Eu³⁺ ions occupy Sr²⁺ in addition to La³⁺, resulting in the luminescent centers related to heterovalent substitution defects. The different Eu³⁺ sites make two phosphors exhibit different red luminescence properties. SrLa₂(Mg₂W₂)O₁₂:Eu³⁺ shows higher luminescent efficiency and thermal quenching due to its regular distribution of the activators resulting in lower dispersion losses of the energy transfer. The experimental results show that rare earth ions occupy different crystallographic positions in A-site and B-site deficient perovskite oxides, and this microstructure can be important for the corresponding luminescent properties.

Keywords: Eu(3+); Laser site-selective spectroscopy technique; Perovskite-type compound; Photoluminescence; Tungstate.