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DOE OSTI2020

Materials Data on BaZrF6 by Materials Project

BaZrF6 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ba2+ is bonded in a 11-coordinate geometry to eleven F1- atoms. There are a spread of Ba–F bond distances ranging from 2.72–3.20 Å. Zr4+ is bonded in a 7-coordinate geometry to seven F1- atoms. There are a spread of Zr–F bond distances ranging from 2.03–2.29 Å. There are six inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted bent 120 degrees geometry to one Ba2+ and one Zr4+ atom. In the second F1- site, F1- is bonded in a 2-coordinate geometry to two equivalent Ba2+ and two equivalent Zr4+ atoms. In the third F1- site, F1- is bonded in a distorted single-bond geometry to two equivalent Ba2+ and one Zr4+ atom. In the fourth F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent Ba2+ and one Zr4+ atom. In the fifth F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent Ba2+ and one Zr4+ atom. In the sixth F1- site, F1- is bonded in a distorted single-bond geometry to two equivalent Ba2+ and one Zr4+ atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaZrF6 by Materials Project

BaZrF6 crystallizes in the orthorhombic Cmme space group. The structure is three-dimensional. Ba2+ is bonded in a 10-coordinate geometry to ten F1- atoms. There are a spread of Ba–F bond distances ranging from 2.65–2.99 Å. Zr4+ is bonded in a 8-coordinate geometry to eight F1- atoms. There are four shorter (2.06 Å) and four longer (2.27 Å) Zr–F bond lengths. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 1-coordinate geometry to two equivalent Ba2+ and one Zr4+ atom. In the second F1- site, F1- is bonded in a trigonal planar geometry to one Ba2+ and two equivalent Zr4+ atoms.

36 MATERIALS SCIENCE↗

NASA NTRS1985

X-ray diffraction studies of phase transformations in heavy-metal fluoride glasses

Powder X-ray diffraction and differential scanning calorimetry studies of the crystallization properties of five ZrF4-based glass compositions have indicated that the crystalline phase in Zr-Ba-La-Pb fluoride glass is beta-BaZrF6; no such identification of crystal phases was obtainable, however, for the other glasses. Reversible polymorphic phase transformations occur in Zr-Ba-La-Li and Zr-Ba-La-Na fluoride glasses, upon heating to higher temperatures.

Bansal, N. P.↗

NASA NTRS1984

Crystallization of fluorozirconate glasses

The crystallization of a number of glasses of the fluorozirconate family has been studied (using powder X-ray diffraction and DSC) as a function of time and temperature of heating. The main crystalline phases were beta BaZrF6 and beta BaZr2F10. Stable and metastble transformations to the low-temperature alpha phases were also investigated. The size of crystallites in fully devitrified glasses was calculated (from line broadening of the X-ray diffraction peaks) to be about 60 nm.

Bansal, Narottam P.↗

NASA NTRS1984

Crystallization of heavy metal fluoride glasses

The kinetics of crystallization of a number of fluorozirconate glasses were studied using isothermal and dynamic differential scanning calorimetry and X-ray diffraction. The addition of the fluorides LiF, NaF, AlF3, LaF3 to a base glass composition of ZrF4-BaF2 reduced the tendency to crystallize, probably by modifying the viscosity-temperature relation. ZrF4-BaF2-LaF3-AlF3-NaF glass was the most stable against devitrification and perhaps is the best composition for optical fibers with low scattering loss. Some glasses first crystallize out into metastable beta-BaZr2F10 and beta-BaZrF6 phases, which transform into the most stable alpha-phases when heated to higher temperatures. The size of the crystallites was estimated to be about 600 A from X-ray diffraction.

Bansal, Narottam P.↗

NASA NTRS1990

Containerless processing of fluoride glass

Ground-based experiments on glass formation, crystallization, surface tension, vaporization, and chemical durability of a zirconium-barium-lanthanum (ZBL) fluoride glass are summarized. In a container large, columnar grains grew out from the container-glass interface during cooling. The main crystalline phase was alpha BaZrF6. A ZBL glass sphere was levitated acoustically during Shuttle flight STS-11. The glass was melted and then cooled while being levitated (containerless). Crystallization in the recovered sample was very fine and mainly beta BaZr2F10, showing the influence of the container on the nucleation and microstructure of crystallization in the glass. Glass formation should be easier for a containerless glass than in a container.

Doremus, Robert H.↗