Mixed-modifier effect in (Ca,Mg) metaphosphate glasses

Griebenow, Kristin; Kamitsos, E. I.; Wondraczek, Lothar

doi:10.1016/j.jnoncrysol.2017.04.036

Cited by 27 publications

(23 citation statements)

References 43 publications

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“…e ., rotational motions (liberation modes) of interconnected tetrahedral SiO 4 units and localized vibrations of the network modifier cations within oxygen cages. Noteworthy, the latter are different from the common cage rattling modes of modifier cations as they are typically found in the Raman scattering range of 100–300 cm −1 69,70 .…”

Section: Discussionmentioning

confidence: 81%

Boson peak, heterogeneity and intermediate-range order in binary SiO2-Al2O3 glasses

Ando¹,

Benzine²,

Pan³

et al. 2018

Sci Rep

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In binary aluminosilicate liquids and glasses, heterogeneity on intermediate length scale is a crucial factor for optical fiber performance, determining the lower limit of optical attenuation and Rayleigh scattering, but also clustering and precipitation of optically active dopants, for example, in the fabrication of high-power laser gain media. Here, we consider the low-frequency vibrational modes of such materials for assessing structural heterogeneity on molecular scale. We determine the vibrational density of states VDoS g(ω) using low-temperature heat capacity data. From correlation with low-frequency Raman spectroscopy, we obtain the Raman coupling coefficient. Both experiments allow for the extraction of the average dynamic correlation length as a function of alumina content. We find that this value decreases from about 3.9 nm to 3.3 nm when mildly increasing the alumina content from zero (vitreous silica) to 7 mol%. At the same time, the average inter-particle distance increases slightly due to the presence of oxygen tricluster species. In accordance with Loewensteinian dynamics, this proves that mild alumina doping increases structural homogeneity on molecular scale.

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Section: Discussionmentioning

confidence: 81%

Boson peak, heterogeneity and intermediate-range order in binary SiO2-Al2O3 glasses

Ando¹,

Benzine²,

Pan³

et al. 2018

Sci Rep

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“…Q n indicates a phosphate tetrahedral unit with n bridging oxygen atoms connecting to a neighboring PO 4 tetrahedron. The band at 1349 cm −1 can be attributed to the stretching mode of the P=O double bond, ν(P = O), of the Q 3 unit and the band at about 1298 cm −1 to the asymmetric stretching mode of the

{PO}_{2}^{-}

group in Q 2 units,

ν_{as} ({PO}_{2}^{-})

, in metaphosphate chains or rings . The Raman bands at 1156 and 1200 cm −1 are characteristic for the symmetric stretching mode of Q 2 units,

ν_{normals} ({PO}_{2}^{-})

.…”

Section: Resultsmentioning

confidence: 99%

“…The development of IR spectra with Al 2 O 3 and SiO 2 incorporation is in good agreement with the Raman spectra (Figure ), although more bands are IR active and, thus, more vibrational modes overlap. The high‐frequency range is dominated by a strong band peaking in the range from 1283 to 1298 cm −1 , owing to the

ν_{as} ({PO}_{2}^{-})

mode of the

{PO}_{2}^{-}

group in Q 2 units . This band of Q 2 units at about 1300 cm −1 exhibits some contribution from Q 3 units on the high‐energy side, and the down‐shift of this band from 1298 to 1283 cm −1 reflects the higher degree of depolymerization, as the number of Q 3 units decreased and more Q 1 units formed for longer melting times at 1200°C in Al 2 O 3 crucibles .…”

Section: Resultsmentioning

confidence: 99%

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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“…Usually, the tetrahedra are classified using the Q n terminology, where the superscript represents the number of BOs per tetrahedron. Hence, three main tetrahedral species are distinguished: Q 1 —phosphate tetrahedra with one BO; Q 2 —with two BOs; and Q 3 —with three BOs . In the case of equimolar amounts of a matrix modifier oxide with phosphorus pentoxide as network former, the metaphosphate structure is attained, which is mostly composed of the Q 2 units .…”

Section: Introductionmentioning

confidence: 99%

Synergistic thermo‐Raman and calorimetric kinetic study of the cation modifier's role in binary metaphosphate glasses

Sendova

Jiménez

2018

J Raman Spectroscopy

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A comprehensive temperature‐dependent Raman spectroscopy and differential scanning calorimetry study has been performed on three metaphosphate glasses with different modifying cations (Ca2+, Ba2+, and Pb2+). The P–NBO (nonbridging oxygen) Raman spectral feature, the force constant, and the glass transition activation energy (AETg) are shown to be strongly correlated to the relative effective nuclear charge difference between the modifying and the glass former cations, ζ. In addition, the estimated AETg values between 3.6(2) and 4.7(2) eV are found to be in the range of the P–O bond energy values in the phosphate glasses. The study contributes to the enrichment of the bond exchange kinetic theory of the glass transition in general and to the bond modifying mechanism of the cations. The authors propose that Raman spectroscopy alone can be implemented reliably for evaluation not only of AETg, but for calculation of the Morse potential of the moiety crucial for the onset of glass transition. Alternatively, in glasses without Raman scattering, the force constant of the critical moiety can be deduced from calorimetric measurements alone. The proposed analytical methodology broadens Raman spectroscopy and calorimetric applications and offers a viable technique for all types of glass matrices.

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Mixed-modifier effect in (Ca,Mg) metaphosphate glasses

Cited by 27 publications

References 43 publications

Boson peak, heterogeneity and intermediate-range order in binary SiO2-Al2O3 glasses

Boson peak, heterogeneity and intermediate-range order in binary SiO2-Al2O3 glasses

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

Synergistic thermo‐Raman and calorimetric kinetic study of the cation modifier's role in binary metaphosphate glasses

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