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Materials Data on BaZr2F10 by Materials Project

BaZr2F10 crystallizes in the monoclinic C2/c 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 2.71–3.01 Å. Zr4+ is bonded to seven F1- atoms to form a mixture of corner and edge-sharing ZrF7 pentagonal bipyramids. There are a spread of Zr–F bond distances ranging from 2.00–2.20 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 two equivalent Zr4+ atoms. In the second F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Zr4+ atoms. In the third F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Zr4+ atoms. In the fourth F1- site, F1- is bonded in a distorted linear geometry to one Ba2+ and one Zr4+ atom. In the fifth F1- site, F1- is bonded in a distorted single-bond geometry to two equivalent Ba2+ and one Zr4+ atom. In the sixth F1- site, F1- is bonded in a distorted bent 120 degrees geometry to one Ba2+ and one Zr4+ atom.

36 MATERIALS SCIENCE↗

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.↗

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.↗

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.↗