Judd-Ofelt parameters of Er~(3+) in transparent TeO_2-based nanocrystallized glasses

摘要

Transparent Er~(3+)-doped bulk nanocrystallized (size of nanocrystals: ～40 nm) glasses of 15K_2O·15Nb_2O_5·70TeO_2·0.5Er_2O_3 and 10BaO·10Gd_2O_3·80TeO_2·0.5Er_2O_3 are prepared, and the Judd-Ofelt parameters, Ω_t (t = 2, 4, 6), of Er~(3+) 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 Ω_2 parameter due to the nanocrystallization, indicating that the degree of the site symmetry of Er~(3+) ions in nanocrystallized glasses is much higher than that in the precursor glasses. The decrease in the Ω_4 and Ω_6 parameters due to the crystallization is small, suggesting that the covalency of Er~(3+)-O bonds in nanocrystals is not so different from that in the precursor glasses.