Luminescence and scintillation properties of the small band gap compound LaI3:Ce3+

LaI3:Ce3+ has the smallest band gap in the LaX3:Ce3+ (X=F, Cl, Br, I) series and hence a potentially higher scintillation yield. The luminescence properties of LaI3:Ce were investigated by means of optical, X-ray, and gamma-ray excitation. Unexpectedly, the compound is a poor scintillator at room temperature but presents good scintillation properties for temperatures below 100 K where Ce3+ emission is observed peaking at 452 and 502 nm with a yield of similar to16000 photons/MeV. The drastic thermal quenching of luminescence is explained by the proximity of the Ce3+ lowest 5d excited state to the host conduction band. Autoionization of Ce3+ therefore prevents any scintillation effect at room temperature. The positions of Ce3+ levels relative to the host bands were estimated. (C) 2004 Elsevier B.V. All rights reserved.