The Intermediate Role of Gd3+ in the Energy Transfer from a Sensitizer to an Activator (Especially Tb3+)

Abstract

Energy transfer from a sensitizer to an activator via Gd³⁺ ions is discussed. This is done for the Bi³⁺ → Dy³⁺ and Sb³⁺ → Dy³⁺ transfer in , and for the Bi³⁺ → Tb³⁺ transfer in . The phosphor shows Tb³⁺ luminescence with a quantum efficiency of 80% for excitation of Bi³⁺. After excitation of Bi³⁺, energy transfer takes place to Gd³⁺ ions. Then the energy may migrate from one Gd³⁺ to another until energy transfer from Gd³⁺ to Tb³⁺ occurs. Compared to the energy transfer in other sensitized Tb³⁺ phosphors, this process has a high efficiency at relatively low activator concentrations. The energy transfer from Bi³⁺ to Gd³⁺ and between Gd³⁺ions mutually has been investigated for . For energy transfer between Gd³⁺ ions is observed. The quantum efficiency of the Gd³⁺ luminescence for Bi³⁺ excitation of amounts to 75% and decreases for increasing Gd concentrations.