Judd–Ofelt parameters of Er3+ in transparent TeO2-based nanocrystallized glasses

Transparent Er3+-doped bulk nanocrystallized (size of nanocrystals: ∼40 nm) glasses of 15K2O·15Nb2O5·70TeO2·0.5Er2O3 and 10BaO·10Gd2O3·80TeO2·0.5Er2O3 are prepared, and the Judd–Ofelt parameters, Ωt (t=2, 4, 6), of Er3+ are evaluated from optical absorption spectra. The change in the molar polarizability due to the nanocrystallization is small in both samples, but a clear decrease in the mean atomic volume due to the nanocrystallization, i.e. more close atom packing, is observed. In both systems, a large decrease is observed in the Ω2 parameter due to the nanocrystallization, indicating that the degree of the site symmetry of Er3+ ions in nanocrystallized glasses is much higher than that in the precursor glasses. The decrease in the Ω4 and Ω6 parameters due to the crystallization is small, suggesting that the covalency of Er3+–O bonds in nanocrystals is not so different from that in the precursor glasses.