A Study on the Mechanism of the Abnormal Reduction of Eu3+→Eu2+in Sr2B5O9Cl Prepared in Air at High Temperature

This paper reports a new observation of the abnormal reduction of Eu3+→Eu2+in Sr2B5O9Cl when prepared in air at high temperature. A model based on the nature of substitution defects is proposed to explain this abnormal reduction. Electrons, which reduced the Eu3+ions, are created by the substitution of cations first and then transferred to the target Eu3+ions via tetrahedral borate anion groups. Codoping experiments are designed and performed. The results of these experiments support the model proposed.