Optical transitions ofHo3+ions in fluorozirconate glass

Abstract

Optical-absorption and emission spectra are presented for ${\mathrm{Ho}}^{3+}$ ions in fluorozirconate (ZBLA) glass [the nominal composition of ZBLA glass (in mol%) is 57, ${\mathrm{ZrF}}_4$; 34, ${\mathrm{BaF}}_2$; 5, ${\mathrm{LaF}}_3$; and 4, ${\mathrm{AlF}}_3$]. The measured oscillator strengths and radiative rates for several transitions were compared with calculated values. Nonradiative transition rates for the excited states were determined by the difference between the measured rates and the calculated radiative rates. Multiphonon emission and energy-transfer effects accounted for the nonradiative transitions. The low-temperature multiphonon emission rates are in agreement with the rates predicted by the phenomenological energy-gap law, when one uses parameters obtained previously for ${\mathrm{Z}\mathrm{B}\mathrm{L}\mathrm{A}:\mathrm{E}\mathrm{r}}^{3+}$. The crystallization of ZBLA glass was studied, with ${\mathrm{Ho}}^{3+}$ and ${\mathrm{Er}}^{3+}$ ions as probes. Isochronal heating data indicate that the glass undergoes rapid devitrification around 630 K. The crystallization of ZBLA is found to involve two distinct processes.