Study of Energy Transfer from Sb3+, Bi3+, Ce3+ to Sm3+, Eu3+, Tb3+, Dy3+

Abstract

Energy transfer from the sensitizers (S) Sb³⁺, Bi³⁺, or Ce³⁺ to the activators (A) Sm³⁺, Eu³⁺, Tb³⁺, or Dy³⁺ has been studied in four different host lattices, viz., YOCl, YBO₃, YAl₃B₄O₁₂, and YPO₄. The efficiency of the energy transfer in these systems varies markedly. This is the case even for a given combination of S and A in different host lattices. In most, but not all, cases SS energy transfer is also important. The SA energy transfer is probably nonradiative and occurs mainly by exchange interaction if the S emission band overlaps only 4f−4f absorption bands of A, but by electric multipole—multipole interaction, if the S emission band overlaps allowed absorption bands of A. Taking these ideas and the energy overlap of S emission and S absorption or S emission and A absorption into account, it is possible to explain the results in a qualitative way. If, however, the energy difference between the state S^* (excited) +A and the state consisting of the ions S⁺+A⁻ is relatively small, no energy transfer by exchange is observed.