Energy transfer between Ce³⁺ and Eu²⁺ in SrAl₁₂O₁₉:Ce_x³⁺, Eu_0.01²⁺ (x = 0.01-0.09)

The influence of the Ce³⁺ concentration on the cathodoluminescence (CL) characteristics of SrAl₁₂O₁₉:Ce_x³⁺, Eu_0.01²⁺ (x = 0.01-0.09) was studied. At 1 mol% cerium in SrAl₁₂O₁₉:Ce_x³⁺, Eu_0.01²⁺ (x = 0.01), two broad emission bands centered at 320 nm and at about 400 nm were observed. The intensity of Ce³⁺ emission at 320 nm decreased as the Ce³⁺ concentration increased, whereas the intensity of the emission band at 400 nm increased with increasing Ce³⁺ concentration at fixed Eu²⁺ concentration. At low concentration of Ce³⁺ (x = 0.1-0.5), the Ce³⁺ emission intensity decreased with the Eu²⁺ emission intensity being enhanced due to the energy transfer from Ce³⁺ to Eu²⁺. In high concentrations of Ce³⁺ (x = 0.07, 0.09), the cross-relaxation processes between nearest Ce³⁺ ions led to the diminishing intensity of Ce³⁺ emission, because of the limited energy acceptors, i.e., Eu²⁺ ions, which resulted in a single emission band at about 400 nm.