Valency states of Yb, Eu, Dy and Ti ions in Li2B4O7 glasses

Abstract Absorption and emission spectra of Eu and Dy, Yb and Ti ions in Li2B4O7 glasses grown in oxygen and hydrogen gas atmospheres were measured for valency states and lattice-sites analysis. For the Li2B4O7 glass doped with Eu2+, Eu3+ and Dy3+ ions which were grown in oxidizing and reducing atmospheres, absorption and emission bands due to these ions were investigated before and after γ-irradiation. For the Yb3+-doped Li2B4O7 glass, a weak, broad band was observed near the sharp 976.3 nm absorption band. The origin of this band is discussed in comparison with other glasses. Moreover, irradiation experiments using γ-rays were also performed in order to investigate the possibility of valency change of Yb ions. It was found that Ti4+ ions, which are produced under oxidizing atmosphere, change to Ti3+ ions after γ-irradiation with a dose of 105 Gy. An additional absorption band observed at about ∼500 nm is due to the Ti3+ ions accompanied by charge-compensating vacancy and does not give any emission.