ZrF4-based Fluoride Glasses Research Articles

Plasma-enhanced chemical vapor deposition of ZrF 4-based fluoride glasses

A ZBLAN (ZrF 4BaF 2LaF 3AlF 3NaF) glass film is synthesized for the first time on the inner surface of a ZBLYAN (ZrF 4BaF 2LaF 3YF 3AlF 3NaF) support tube. The maximum deposition rate is about 60 μm/h. The composition of the ZBLAN glass film is controlled with the vaporizing temperatures of the starting materials, but compositional distribution is observed along the preform axis. The thermal properties of the synthesized glass film are nearly the same as those of ZBLAN glass synthesized by the conventional melt-casting method.

H 2O and HF evolution from ZBLAN glasses

Hydrogen containing gases which evolve from ZrF 4-based heavy metal fluoride glasses during remelting were analyzed using a mass spectrometer. H 2O and HF gases evolved in proportion to the initial hydroxyl concentration of the glass. One glass, which had been prepared using CC1 4, evolved a comparatively large amount of HC1 gas in preference to H 2O.

Electrical conductivity of LiF [sbnd]AlF 3[sbnd]BaNbOF 5 quasi-fluoride glasses

A comparative study of electrical properties of two systems of glasses xLiF (100 − x)BaNbOF 5 and xLiF (100 − x) (0.3AlF 3 · 0.7BaNbOF 5) ( x = 10−60 mol%) has been carried out as a function of LiF content. A minimum in ionic conductivity and a maximum in activation energy has been detected in both systems. It was found that, in the LiF-BaNbOF 5 binary system, the maximal activation energy and the minimal ionic conductivity occur at different LiF concentrations. By analogy with many ZrF 4-based fluoride glasses and the comparison of the influence of AlF 3 on the transport properties of the glasses with low and high LiF content, it is proposed that for the ternary system the transport properties mainly result from the contribution of mobile F − ions in the low LiF content ( ⩽ 25 mol%) region. In the high LiF concentration ( > 25 mol%) domain, the ionic conductivity is mainly governed by the migration of Li + ions. For binary systems, in the low LiF content ( ⩽ 25 mol%) region, the transport properties mainly result from the F − ions; in the range of LiF concentration between 25 and 50 mol%, both Li + and F − ions are responsible for the conduction; when the LiF concentration is higher than 50 mol%, the ionic conductivity of the glasses is mainly dominated by the migration of Li + ions.

Melting Apparatus for the Synthesis of Bulk ZrF4‐Based Fluoride Glass

Heavy‐metal fluoride glasses are currently prepared by melting of the solid fluoride precursors. We have constructed a melting facility for the synthesis of ZrF4‐based fluoride glass cullet. This stand‐alone system provides a controlled (dry and reactive) atmosphere and in situ quenching of the melts. The glass is melted in a vitreous carbon crucible, which is mounted in a silica tube flow reactor. The reactor is resistively heated with a tube furnace and purged with He and SF6 or Cl2. It was found that of the latter two halogenating species only Cl2 prevents effectively the formation of black inclusions in the melt (ZrF3 and ZrF2 particles). With this melting apparatus we have routinely melted 250‐g batches of optically clear ZrF4–BaF2–LaF3–AlF3–NaF glass samples.

Laser emission of Er +3 in ZrF 4 -based fluoride glass

Laser emission is reported in an Er+3-doped ZrF4-based fluoride glass often referred to as ‘heavy metal fluoride glass’ (HMFG). The laser operates at room temperature at a wavelength of 2.78μm. The glass is a standard ZBLAN formulation in which all of the LaF3 (4 mol%) is replaced by ErF3. Glass preparation, spectroscopy, and laser data are presented and discussed.

Absorption characteristics of CO2 molecules dissolved in ZrF4-based fluoride glass

Absorption characteristics of CO2 molecules dissolved in ZrF4-based glass are measured using a Fourier transform spectral attenuation measurement system. Absorptions due to vibrational modes appear at 2353, 3606, and 3716 cm−1, respectively. The influence of the CO2 impurity on transmission loss is clarified. The interaction between dissolved CO2 molecules and the glass matrix is discussed on the basis of the measured spectra.

Dielectric and dynamic mechanical study of ionic motions in a ZrF 4-based fluoride glass

The dielectric permittivity and loss of 0.55 ZrF 4 -0.31BaF 2 -0.06NaF-0.05LaF 3 -0.03AlF 3 glass were measured from 12 Hz to 100 kHz over a wide temperature range up to its T g . Its dynamic mechanical properties were measured from 10 −3 to 1 Hz and at 3 kHz. The dielectric and mechanical relaxation spectra have nearly the same half-width and are much narrower than those observed for other amorphous solids. The rate of the mechanical relaxation is the same as of the electrical relaxation and the two have the same temperature dependence. An analysis for the origin of the two relaxations in terms of the structure of the glass suggests that loosely packed local regions where molecular motion persists may involve regions of unbridged fluoride ions and that the introduction of Ba or other ions in the matrix is partly responsible for the greater strength of the relaxations, while dc conduction in them may still involve long-range diffusion of F − ions.

Iron Ions in ZrF4-Based Fluoride Glasses

Mössbauer spectroscopy, magnetic susceptibility and optical absorption studies have been carried out in order to investigate the states of iron ions in ZrF4-based fluoride glasses prepared using oxidising (NF3 and O2) and inert (Ar) atmospheres. Under oxidising atmospheres iron ions are present as high-spin ferric ions in an octahedral field, while under an inert atmosphere they are in high-spin ferrous states, occupying two inequivalent octahedral sites. In addition, the behavior of ferric ions under the inert atmosphere has been investigated. Ferric-ion stably exists in Ar, but with the presence of moisture they react with OH and are accordingly reduced to ferrous ions.

Phase separation and controlled crystallization of non-oxide glasses

This paper reviews the experimental results associated with the phase separation and controlled crystallization of non-oxide glasses, mainly chalcogenide glasses and ZrF 4-based fluoride glasses. Experiments demonstrate that the phase separation is not always the precursor of the glass-ceramic process. It has been found that some non-oxide glasses could be converted into glass ceramics without phase separation. Different mechanisms of controlled crystallization of non-oxide glasses are discussed.

Dispersive and scattering properties of a ZrF 4 based glass

In a previous letter we presented the material dispersion in a ZrF4 based fluoride glass. The zero crossover wavelength λc was found to occur between 1.6 and 1.7 μm. Here, we analyse the refractive index measurements against wavelength data in order to obtain some physical parameters of this material on which λc is dependent: electronic energy gap E0, electronic oscillator strength ED, lattice oscillator strength E1 and structure factor B. Such values, which are not yet known for fluoride glasses, will be then compared with those corresponding to SiO2 glass. Evaluation of the Rayleigh scattering coefficient will also be made.