Local Structure of SixCoordinated Silicon in Li2OSiO2P2O5 Glasses by Transmission XAFS Experiments

Handa, Keita; Ide, Junko; Yamamoto, Kazuhiro; Kurosawa, Nanase; Ozutsumi, Kazuhiko; Harami, Tadahiko; Kojima, K.; Umesaki, Norimasa

doi:10.1238/physica.topical.115a00314

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“…High phosphate content silicophosphate glasses are known for the presence of sixfold‐coordinated silicon even when prepared at ambient pressure . They are of potential interest for various applications, for example, optical fibers or in fuel cells .…”

Section: Introductionmentioning

confidence: 99%

“…High phosphate content silicophosphate glasses are known for the presence of sixfold-coordinated silicon even when prepared at ambient pressure. [1][2][3][4][5][6][7][8][9][10][11][12] They are of potential interest for various applications, for example, optical fibers 13,14 or in fuel cells. 14,15 However, owing to their low chemical durability their use is still limited.…”

Section: Introductionmentioning

confidence: 99%

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Modification of silicophosphate glass composition, structure, and properties via crucible material and melting conditions

Sawangboon

Nizamutdinova

Uesbeck

et al. 2019

Int J of Appl Glass Sci

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Ceramic crucibles are known to corrode in contact with glass melts. Here, we investigate the effect of alumina and fused silica crucibles on the composition, structure, and properties of silicophosphate glasses. Glasses in the system 0.3 Na2O‐0.6 P2O5‐0.1 SiO2 were melted in platinum, alumina, or fused silica crucibles at 900°C or 1200°C for 0.5‐12 hours. Al2O3 and SiO2 were found to leach from the crucibles into the glass melt and alter the glass composition: Al2O3 content increased with melting temperature and time, resulting in up to 10 mol% Al2O3; SiO2 from fused silica crucibles was also introduced into the glass, resulting in a 25% higher SiO2 content compared to the nominal composition. Glass density, transition temperature, thermal expansion, and mechanical properties were strongly affected by these compositional changes. Based on vibrational spectroscopy, this is explained by increasing numbers of P–O–Al or P–O–Si bonds, resulting in a depolymerization of the phosphate network, and ionic cross‐linking by high field strength aluminum or silicon ions. With increasing alumina content, P–O–Si bonds were replaced by P–O–Al bonds. 31P and 27Al MAS NMR spectra revealed that aluminum is present in sixfold coordination exclusively and fully bonded to phosphate species, connecting phosphate groups by P–O–Al–O–P bonds.

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Section: Introductionmentioning

confidence: 99%