Coexistence mechanism of Eu 2+ /Eu 3+ ions in YAl 3 (BO 3 ) 4 : Crystal structure, luminescence property, and substitution defects

Abstract The coexistence mechanism of Eu 2+ and Eu 3+ ions in YAl 3 (BO 3 ) 4 host under different reducing conditions is investigated and confirmed in great detail, which can be described by three aspects as following. First, Eu 3+ is protected by the layered structure of YAl 3 (BO 3 ) 4 . Second, the number of the interstitial defects ((Al) i … ,(Y) i … ) increases with increasing Eu 2+ to maintain the charge balance of the system. And these defects can capture free electrons which are used for the reduction of Eu 3+ . Finally, free holes become more and more with the number of nonequivalent substitution defects (Eu Y ') increasing, which make the 5d electrons of Eu 2+ easily escape to the conduction band and Eu 2+ convert to Eu 3+ . This work will be of great significance to research coexistence of multiple valence ions in the structure of borate and defect motion with nonequivalent substitution.