Concentration Quenching of Eu3+ Fluorescence

The fluorescence quenching of the two phosphors ${\mathrm{Ba}}_2{\mathrm{Gd}}_{\text{1−x}}{\mathrm{Eu}}_x{\mathrm{Me}}^{\text{5+}}{\mathrm{O}}_6\mathrm{\hspace{0.17em}(}{\mathrm{Me}}^{\text{5+}}={\mathrm{Nb}}^{\text{5+}}\hspace{0.17em}\mathrm{or}\hspace{0.17em}{\mathrm{Ta}}^{\text{5+}})$ and Gd_1−xEu_xAl₃B₄O₁₂ is reported. The shortest distance between the rare‐earth sites in these materials is large and nearly equal, viz., 6.0 and 5.9 Å, respectively. The quenching behavior is different: In the materials Ba₂Gd_1−xEu_xMe⁵⁺O₆, concentration quenching occurs at x≃02, in the materials Gd_1−xEu_xAl₃B₄O₁₂, no quenching was found under uv excitation. These results are discussed in relation to the Van Uitert—Johnson model for concentration quenching of Eu³⁺ fluorescence.