The carrier capture and recombination processes in Ln3+-activated scintillators

The ability of activator ions to capture charge carriers and assume a different charge state under ionizing radiation is essential for efficient performance of rare-earth (RE)-doped scintillator materials utilizing the carrier recombination energy. In this paper, the sequence of carrier trapping is discussed and interpreted using a simple, single-configuration-coordinate model for two different cases: In one case (LuPO₄:Ce, YAlO₃:Ce, LuAlO₃:Ce) the charge state involved in the scintillation mechanism is Ce⁴⁺, while in the other (LuPO₄:Yb, YbPO₄) it is Yb²⁺. The possibility of a nonradiative recombination via Ce and Yb ions is also considered and found highly unlikely in accordance with experimental results