Energy transfer mechanisms in CaAl₁₂O₁₉:Ce_0.06³⁺,Eu_x²⁺ phosphors

CaAl₁₂O₁₉:Ce_0.06³⁺,Eu_x²⁺ phosphors were synthesized through a combustion process, and their optical properties were investigated using cathodoluminescence (CL) measurements. The results for the CL spectra showed that different energy transfer mechanisms exist in CaAl₁₂O₁₉:Ce_0.06³⁺,Eu_x²⁺ and are dependent on the Eu_x²⁺ acceptor concentration. As the Eu_x²⁺ acceptor concentration increased, the lifetime of the Ce³⁺ donor decreased, while that of the donor related to the diffusion increased. The dominant energy transfer at low concentrations of the Eu_x²⁺ acceptor in CaAl₁₂O₁₉:Ce_0.06³⁺,Eu_x²⁺ was attributed to the electric dipole-dipole interaction between the Ce³⁺ donors and the Eu²⁺ acceptors, resulting from the diffusion limited energy migration. While a similar energy transfer mechanism at the high concentrations of the Eu²⁺ acceptor in CaAl₁₂O₁₉:Ce_0.06³⁺,Eu_x²⁺ dominated in the transient state part, a different energy transfer mechanism appeared in the steady state part of the decay process.