Dissimilar behavior of YAG:Ce and LuAG:Ce scintillator garnets regarding Li+ co-doping

Abstract

Using a combination of experimental methods, the substitution tendencies of Li⁺ and involved charge compensation mechanisms are determined and compared in two important similar scintillators, LuAG:Ce and YAG:Ce. The studies were performed on polycrystalline samples prepared by solid phase reactions as well as in single crystals grown by the vertical Bridgman method. The results show that Li⁺ in LuAG:Ce, Li is localized mainly at Lu³⁺ sites with charge compensation brought about by Ce³⁺ → Ce⁴⁺ conversion and creation of anion vacancies. Surprisingly, unlike LuAG:Ce, Li, no evidence for Li⁺ substitution at Y³⁺ sites and conversion of Ce³⁺ to Ce⁴⁺ has been obtained in YAG:Ce, Li. It suggests that Li⁺ goes mainly to interstitial positions and does not interact with Ce³⁺. From an application point of view, Li⁺ co-doping of YAG:Ce is not efficient to improve the scintillationdecay parameters, however, it is efficient to reduce the amount of anion vacancies in both YAG and YAG:Ce.