Crystallization of BaF<sub>2</sub> from droplets of phase separated glass – evidence of a core–shell structure by ASAXS

Hoell, Armin; Raghuwanshi, Vikram Singh; Bocker, Christian; Herrmann, Andreas; Rüssel, Christian; Höche, Thomas

doi:10.1039/c9ce02003a

Cited by 7 publications

(2 citation statements)

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“…Since calcium is the highest atomic number element in these glasses, the dark colour in bright field images suggests that those PSD are enriched in Ca 2+ . This agrees with studies showing that fluorides can induce phase separation, in which the nucleation and crystallization takes place in the volume of the PSD 14 , 31 – 35 . Larger PSD were also observed in the phosphate-containing glasses (Fig.…”

Section: Resultssupporting

confidence: 92%

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Jaimes

Kirste

Pablos-Martín

et al. 2021

Sci Rep

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Bioactive glasses convert to a biomimetic apatite when in contact with physiological solutions; however, the number and type of phases precipitating depends on glass composition and reactivity. This process is typically followed by X-ray diffraction and infrared spectroscopy. Here, we visualise surface mineralisation in a series of sodium-free bioactive glasses, using transmission electron microscopy (TEM) with energy-dispersive X-ray spectroscopy (EDXS) and X-ray nano-computed tomography (nano-CT). In the glasses, the phosphate content was increased while adding stoichiometric amounts of calcium to maintain phosphate in an orthophosphate environment in the glass. Calcium fluoride was added to keep the melting temperature low. TEM brought to light the presence of phosphate clustering and nearly crystalline calcium fluoride environments in the glasses. A combination of analytical methods, including solid-state NMR, shows how with increasing phosphate content in the glass, precipitation of calcium fluoride during immersion is superseded by fluorapatite precipitation. Nano-CT gives insight into bioactive glass particle morphology after immersion, while TEM illustrates how compositional changes in the glass affect microstructure at a sub-micron to nanometre-level.

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Section: Resultssupporting

confidence: 92%

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Jaimes

Kirste

Pablos-Martín

et al. 2021

Sci Rep

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“…One is the suppression of diffusion, which reduces the crystal growth rate. The base glass in most transparent oxyfluoride glass–ceramics is an aluminosilicate system in which the viscous SiO 2 -rich phase surrounding the fluoride nanocrystal acts as a diffusion barrier, suppressing the crystal growth. ,, Heat treatment at low temperatures is necessary for the precipitation of fluoride nanocrystals because nanocrystallization cannot be achieved without suppressing diffusion, but several hours of heat treatment is necessary because of the low nucleation rate . The other mechanism of nanocrystallization is nanophase separation.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Nanocrystallization of BaF₂ in Oxyfluoride Glasses with Crystal-like Nanostructures: Implications for Upconversion Fiber Devices

Shinozaki

Ishii

Sukenaga

et al. 2022

ACS Appl. Nano Mater.

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Transparent glass−ceramic fibers containing fluoride nanocrystals are attracting attention as upconversion devices. In this paper, a material design is proposed that eliminates the need for heat treatment processes. The impact of short-to mediumrange structures on the crystallization of glasses was investigated to enable nanocrystallization in the quenching process via ultrafast nucleation. In this study, the short-to medium-range structures of (33.3 − x/3)BaF 2 −xZnO−(66.7 − 2x/3)B 2 O 3 glasses were investigated by 11 B-and 19 F-magic-angle spinning nuclear magnetic resonance spectroscopy, molecular dynamics simulations, and the high-energy synchrotron X-ray diffraction. After heat treatment, glasses with x > 40 formed BaF 2 nanocrystals with a diameter of ∼5 nm and a small particle size distribution (<1 nm). Based on the high-energy synchrotron X-ray diffraction, the critical size of the nuclei was estimated to be 4 nm, which was similar to the size of the precipitated crystals. Obvious selectivity in the binding was observed: F − preferred Ba 2+ and O 2− preferred B 3+ , whereas Zn 2+ was bound to both anions. The binding selectivity caused a bicontinuous structure of oxide and fluoride domains, and the fluoriderelated structure factors and bond distance were very similar to the peak positions of the precipitated crystals. Er 3+ -doped glasses with x > 40 showed upconversion luminescence with a spectrum similar to that of BaF 2 . These results suggested the pre-existence of a crystal-like structure with a composition, density, and ordering similar to those of the precipitated crystals. Moreover, glass with the modified composition was successfully crystallized during press-quenching of the melt and the fiber drawing process. These results could facilitate the production of photonic components such as nanocrystallized glass fibers and microspheres for upconversion lasers as well as a wide variety of glass−ceramic products.

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Lanthanide doped fluorosilicate glass-ceramics: A review on experimental and theoretical progresses

Zhao

et al. 2022

Journal of Rare Earths

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Crystallization of BaF₂ from droplets of phase separated glass – evidence of a core–shell structure by ASAXS

Abstract: Glasses with the mol% compositions 1.88 Na2O·15.04 K2O·7.52 Al2O3·69.56 SiO2·6.00 BaF2 and 1.88 Na2O·15.03 K2O·7.52 Al2O3·69.52 SiO2·6.00 BaF2·0.05 SmF3 were studied using X-ray diffraction, transmission electron microscopy, and anomalous small-angle X-ray scattering.

Cited by 7 publications

References 35 publications

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Ultrafast Nanocrystallization of BaF₂ in Oxyfluoride Glasses with Crystal-like Nanostructures: Implications for Upconversion Fiber Devices

Lanthanide doped fluorosilicate glass-ceramics: A review on experimental and theoretical progresses

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Crystallization of BaF2 from droplets of phase separated glass – evidence of a core–shell structure by ASAXS

Abstract: Glasses with the mol% compositions 1.88 Na2O·15.04 K2O·7.52 Al2O3·69.56 SiO2·6.00 BaF2 and 1.88 Na2O·15.03 K2O·7.52 Al2O3·69.52 SiO2·6.00 BaF2·0.05 SmF3 were studied using X-ray diffraction, transmission electron microscopy, and anomalous small-angle X-ray scattering.

Cited by 7 publications

References 35 publications

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Nano-imaging confirms improved apatite precipitation for high phosphate/silicate ratio bioactive glasses

Ultrafast Nanocrystallization of BaF2 in Oxyfluoride Glasses with Crystal-like Nanostructures: Implications for Upconversion Fiber Devices

Lanthanide doped fluorosilicate glass-ceramics: A review on experimental and theoretical progresses

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Crystallization of BaF₂ from droplets of phase separated glass – evidence of a core–shell structure by ASAXS

Ultrafast Nanocrystallization of BaF₂ in Oxyfluoride Glasses with Crystal-like Nanostructures: Implications for Upconversion Fiber Devices