Tuning the Eu luminescence in glass materials synthesized in air by adjusting glass compositions

The doped Eu3+ ions can be partly reduced to Eu2+ in a series of MO–B2O3: Eu (M = Ba, Sr, Ca) glasses synthesized in air atmosphere, but not in the 12CaO–7Al2O3: Eu glass. The different redox-behavior of Eu ions in these two glass systems is attributed to the different host optical basicity. It is found that a lower valence state of Eu2+ is more favorable in acidic glasses, which have lower optical basicities. A notion of the critical value of optical basicity is introduced empirically, which can be used as a guide for the selection of glass composition suitable to incorporate Eu2+ for luminescence.