The reduction of Eu3+ to Eu2+ in air and luminescence properties of Eu2+ activated ZnO–B2O3–P2O5 glasses

A valence change from Eu3+ to Eu2+ was observed in the europium ion-doped ZnO–B2O3–P2O5 glasses prepared at high temperature in air. The fluorescence emission spectrum of the sample consists of a broad emission band ascribed to the 5d–4f transition of Eu2+ ion and sharp emission peaks assigned to the transitions of 5Do–7FJ (J = 0, 1, 2, 3, and 4) of Eu3+ ion, indicating that part of Eu3+ can be reduced into Eu2+ in the glass. A charge compensation model is proposed. The rigid tetrahedral network structure of glasses plays an important role in stability of Eu2+. The fabrication conditions are also studied.