Europium doped strontium borate glasses and their optical properties

Optical absorption and luminescence spectra of europium doped strontium borate glasses prepared in different conditions are studied. It is found that the percentage of Eu3+ ions varies from 100 to 30% being controlled by the conditions of preparation. The mechanism, favoring reduction of europium to Eu2+ state in polycrystalline strontium tetraborate, is much weaker in glasses of the same composition. In samples containing mixed valence europium at densities of 8×1020 cm−3, the efficient transfer of optical excitation from Eu3+ to Eu2+, suppressing the Eu3+ luminescence, has been found. The most reliable way of monitoring the percentage of europium ions in different valences for strontium borate glasses is the measuring of absorption at f-f transition 7F0→5D2 of Eu3+.