Ions In Fluorozirconate Glass Research Articles

Temperature dependence of Faraday rotation and magnetic susceptibility for Ce 3+ and Pr 3+ ions in fluorozirconate glass

The temperature dependencies of the Faraday rotation and magnetic susceptibility for fluorozirconate glass doped with cerium or praseodymium ions are reported. The glass compositions were 52% ZrF 4, 20% BaF 2, 10% CeF 3, 4% AlF 3, and 14% NaF for the cerium-doped glass, and 51% ZrF 4, 21% BaF 2, 8% PrF 3, 4% AlF 3, and 16% NaF for the praseodymium-doped glass; the samples were prepared by quenching from the melt at 1000°C and 960°C for Ce and Pr doped glass, respectively, and annealed at 240°C. Faraday rotations were measured using a modulated optical polarisation technique over a wavelength range of 320–850 nm, and a temperature range of 15–295 K. Magnetic susceptibilities were determined using a transformer-based method over a temperature range of 85–295 K. The paramagnetic part of the Faraday rotation and the magnetic susceptibility both show deviations from Curie's law, and are not simply proportional to each other as frequently assumed. For cerium-doped glass, the temperature dependence of the magnetic susceptibility can be fitted with an expression based on an axially symmetric crystal field appropriate to a square anti-prism site for the cerium ion. The fourth order crystal field parameters are estimated from earlier superposition-model analyses of crystal fields for cerium ions in crystalline fluorides, while the second order parameter is determined by the least squares fitting process.

Comment on "Time-resolved photoluminescence of Fe3+ ions in fluorozirconate glass"

Snow, Freitar, and Strom [Phys. Rev. B 37, 10 332 (1988)] have ascribed the fast component in the ${\mathrm{Fe}}^{3+}$ emission of fluorozirconate glass to a charge-transfer process. Here this is shown to be rather improbable. An obvious and simple alternative is presented.

Optical transitions of Dy 3+ ions in fluorozirconate glass

Optical absorption and emission spectra are presented for Dy 3+ ions in fluorozirconate (ZBLA) glass. The measured oscillator strengths and radiative rates for several transitions are compared with calculated values. Radiative transition rates for the excited states are determined by using the Judd-Ofelt theory (B. R. Judd, Phys. Rev. 127, 750 (1962); G. S. Ofelt, J. Chem. Phys. 37, 511 (1962)). Thermal evolution of the radiative rate is observed for the 4F 9 2 level and is well accounted for by Stark level thermalization. Energy transfer effects are responsible for the nonradiative transitions.

Time-resolved photoluminescence of Fe3+ ions in fluorozirconate glass.

The optical properties of ${\mathrm{Fe}}^{3+}$ ions incorporated into fluorozirconate glass have been studied with optical absorption as well as with steady-state and pulsed photoluminescence (PL) techniques. Two separate contributions to the broad ${\mathrm{Fe}}^{3+}$ PL spectrum have been identified on the basis of distinctly different PL decay rates. The slower process (0.2 ms at 300 K) is associated with the internal transitions from the ${G}^{4}$ crystal-field-split level to the $^{6}\mathrm{A}_{1}$ ground state of the ${\mathrm{Fe}}^{3+}$ ion in an octahedral site. The faster process (10 \ensuremath{\mu}s at 300 K) has been identified with the ${\mathrm{Fe}}^{3+}$\ensuremath{\rightarrow}${\mathrm{Fe}}^{2+}$ charge-transfer process. The appropriate crystal-field parameters are B=1091 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, C=2946 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$, and Dq=1222 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$.

Optical transitions of Pr 3+ ions in fluorozirconate glass

Optical absorption and emission spectra are presented for Pr 3+ ions in fluorozirconate (ZBLA) glass. The measured oscillator strengths and radiative rates for several transitions are compared with calculated values. Radiative transition rates for the excited states are determined by using the Judd-Ofelt theory. Energy transfer effects account for the nonradiative transitions. Although the Judd-Ofelt analysis does not yield the same excellent consistency for oscillator strengths and branching ratios for Pr 3+ as for Er 3+ and Ho 3+, the experimental observations are consistent with the Judd-Ofelt calculations and the multiphonon emission rates predicted by the phenomenological energy-gap law. The crystallization of ZBLA glass also was studied, using Pr 3+ ions as probes.

Optical transitions ofHo3+ions in fluorozirconate glass

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.

Optical transitions ofEr3+ions in fluorozirconate glass

Optical-absorption, -emission, and -excitation spectra are presented for ${\mathrm{Er}}^{3+}$ ions in fluorozirconate glass. Measured oscillator strengths of the transitions between $J$ manifolds at 300 and 15 K are compared with calculated electric and magnetic dipole oscillator strengths. Radiative rates for five luminescing states were calculated. The nonradiative rates from these excited states were determined by calculating the difference between the measured rates and the calculated radiative rates. The low-temperature nonradiative rates are in agreement with the phenomenological energy-gap law followed by rare-earth ions in a number of crystals and glasses. The temperature dependence of the lifetimes was analyzed using the Huang-Rhys theory of multiphonon emission. Values for the $^{4}I_{\frac{11}{2}}$ radiative and nonradiative rates obtained by the above methods are compared with those obtained applying the method Flaherty and DiBartolo used to study Mn${\mathrm{F}}_{2}$: ${\mathrm{Er}}^{3+}$. The multiphonon emission rates in fluorozirconate glass are much lower than the rates for the same levels of ${\mathrm{Er}}^{3+}$ in oxide glasses. Measurements of the bandwidths of the ground and excited states of ${\mathrm{Er}}^{3+}$ and the nearly exponential decay of the emissions indicate a relatively narrow distribution of site symmetries compared to oxide glasses.