The effect of binary glass composition on the Eu-ions luminescence properties

Eu2O3-doped Ca1-xBaxO-2SiO2 glasses were prepared using standard melt-quenching technique at 1500 °C in CO-rich atmosphere. The changes of the Eu2+/Eu3+ ratio as a function of Ba content (x) were investigated by optical absorption, photoluminescence (PL), radioluminescence (RL) and electron paramagnetic resonance (EPR) methods. The increase of x leads to a monotonic decrease of the absorption band related to Eu2+. On the other hand, the glass samples with a dominating Ca2+ content exhibit the strongest Eu2+ luminescence. Altogether this may point out the domination of the energy transfer from Eu2+ to Eu3+. A weak Eu2+- and Eu3+-related emission in mixed glasses with 1-x = 0.5, 0.75 can be the result of some kind of quenching due to the mutual Ca2+ and Ba2+ influence introduced to the nearest environments of Eu ions. The role of x in the glass structure modification was confirmed also by infrared spectroscopy (IR) methods. Specific Eu2+ signals were detected in EPR spectra measured in all the glass samples with the exception of the BaO–2SiO2 one, so only the europium 3+ charge state is expected to be present in this glass. EPR measurements thus correlate well with optical observations.