Temperature effects on non-bridging oxygen and aluminum coordination number in calcium aluminosilicate glasses and melts

Stebbins, Jonathan F.; Dubinsky, E. V.; Kanehashi, Koji; Kelsey, Kimberly E.

doi:10.1016/j.gca.2007.11.018

Cited by 168 publications

(216 citation statements)

References 86 publications

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“…Equation (4) has been used previously as well to estimate the NBO fraction in percalcic aluminosilicate systems. 26) In fact, the calculated NBO fraction was close to the value determined using 17 O MAS NMR spectroscopy (= 32.4 ± 0.3%) (see Fig. 5).…”

Section: Effect Of Degree Of Polymerization Of the Networksupporting

confidence: 83%

Effect of Potassium Oxide Addition on Viscosity of Calcium Aluminosilicate Melts at 1673–1873 K

et al. 2014

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We investigated the changes induced in the viscosities of CaO-SiO2-Al2O3-K2O melts (CaO/SiO2 molar ratio = 0.68 ± 0.04, Al2O3 content = 13.4 ± 0.6 mol%) with the addition of K2O in amounts of 0-17.4 mol% for temperatures of 1 673-1 873 K using the rotating crucible method. The viscosity increased with an increase in the K2O content when K2O/Al2O3 molar ratio < 0.7. On the other hand, the viscosity decreased with the addition of K2O for K2O/Al2O3 molar ratio > 0.9. The maximum values of the viscosities were noticed in the range of 0.7 < K2O/Al2O3 molar ratio < 0.9. This behavior could not be explained on the basis of the polymerization degree of the aluminosilicate network structure. The 17 O magic angle spinning nuclear magnetic resonance (MAS NMR) spectrum of the 31.6CaO-44.2SiO2-13.4Al2O3-10.8K2O (mol%) glass suggested that K + ions preferentially compensate the negative charge of AlO4, while the Ca 2+ ions primarily create non-bridging oxygens (NBOs). The viscosity data and the 17 O MAS NMR spectrum also suggested that the increase in viscosity for K2O/Al2O3 molar ratio < 0.7 was because of the increase in the average bond strength of the aluminosilicate framework, which was attributable to the substitution of Ca 2+ ions by K + ions at the charge compensator sites. The activation energies for viscous flow indicated that the NBOs bonded with K + ions, forming NBO-K species, for K2O contents greater than those corresponding to the viscosity maxima. Thus, the viscosities of aluminosilicate melts are indicative of the average bond strengths of the melts.KEY WORDS: viscosity; K-Ca aluminosilicate melts and glasses;17 O MAS NMR spectroscopy.

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Section: Effect Of Degree Of Polymerization Of the Networksupporting

confidence: 83%

Effect of Potassium Oxide Addition on Viscosity of Calcium Aluminosilicate Melts at 1673–1873 K

et al. 2014

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“…The effect of temperature on ð∂X NBO ∕∂PÞ T at high pressure is necessary to have improved understanding of the nature of melt polymerization above the melting temperature. At 1 atm, the effect of a fictive temperature on the X NBO for diverse aluminosilicate melts was reported to be apparently minor (47). The sloped ð∂X NBO ∕∂PÞ T thus derived from these supercooled liquids is likely to be representative of that in the melts themselves.…”

Section: O-17mentioning

confidence: 95%

Simplicity in melt densification in multicomponent magmatic reservoirs in Earth’s interior revealed by multinuclear magnetic resonance

Lee

2011

Proc. Natl. Acad. Sci. U.S.A.

114

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Pressure-induced changes in properties of multicomponent silicate melts in magma oceans controlled chemical differentiation of the silicate earth and the composition of partial melts that might have formed hidden reservoirs. Although melt properties show complex pressure dependences, the melt structures at high pressure and the atomistic origins of these changes are largely unknown because of their complex pressure-composition dependence, intrinsic to multicomponent magmatic melts. Chemical constraints such as the nonbridging oxygen (NBO) content at 1 atm, rather than the structural parameters for melt polymerization, are commonly used to account for pressure-induced changes in the melt properties. Here, we show that the pressure-induced NBO fraction in diverse silicate melts show a simple and general trend where all the reported experimental NBO fractions at high pressure converge into a single decaying function. The pressure-induced changes in the NBO fraction account for and predict the silica content, nonlinear variations in entropy, and the transport properties of silicate melts in Earth's mantle. The melt properties at high pressure are largely different from what can be predicted for silicate melts with a fixed NBO fraction at 1 atm. The current results with simplicity in melt polymerization at high pressure provide a molecular link to the chemical differentiation, possibly missing Si content in primary mantle through formation of hidden Si-rich mantle reservoirs. E arly in Earth history, during the magma-ocean phase, the chemical differentiation of the silicate earth, formation of core, and evolution of atmosphere were controlled by the properties of silicate melts at high pressure (1-6). Pioneering experimental studies show that these thermodynamic and transport properties relevant to the chemical evolution of the Earth vary nonlinearly with changes in pressure (7-9). For instance, the solubility of Ar into melts increases with increasing pressure and then decreases drastically with a further increase in pressure, with data suggesting a strong composition dependence (7,10,11). Similarly, complex behaviors were reported for the diffusivity and viscosity of silicate melts at high pressure (8). Although the trend in the silica activity in the melts at high pressure is not known, phase relations of mantle melts and minerals imply varying activity coefficients of the oxide in silicate melts with changes in pressure (12)(13)(14). Changes of up to two orders of magnitude in the element partitioning coefficient between melts and crystal/coexisting phases have been reported stemming mostly from the effect of the melt composition, constraining the fate of radioactive nuclides in the Earth's interior (15-18).The key to understanding these nonlinear changes in melt properties with pressure is the melt structure at high-pressure in a short-(e.g., coordination number) to medium-range scale (19)(20)(21). While recent progress in mineral physics provides the link between the macroscopic properties and the structures of...

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“…In general, the Al atoms in the investigated materials are four-or fivefold-coordinated and were both treated as network formers such that n O A represents either the Si-O or Al-O coordination number, or an average of both. The assignment of a networkforming role to fivefold-coordinated Al follows from the existence of pure aluminate glasses, in which networks are found with both four-and fivefold-coordinated Al atoms (SI Text, section 3.3), and from work on aluminosilicates (31 ( Fig. 2B).…”

Section: Significancementioning

confidence: 99%

Packing and the structural transformations in liquid and amorphous oxides from ambient to extreme conditions

Zeidler

Salmon

Skinner

2014

Proc. Natl. Acad. Sci. U.S.A.

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Liquid and glassy oxide materials play a vital role in multiple scientific and technological disciplines, but little is known about the part played by oxygen-oxygen interactions in the structural transformations that change their physical properties. Here we show that the coordination number of network-forming structural motifs, which play a key role in defining the topological ordering, can be rationalized in terms of the oxygen-packing fraction over an extensive pressure and temperature range. The result is a structural map for predicting the likely regimes of topological change for a range of oxide materials. This information can be used to forecast when changes may occur to the transport properties and compressibility of, e.g., fluids in planetary interiors, and is a prerequisite for the preparation of new materials following the principles of rational design. Examples range from the dependence on network connectivity of the transport properties (e.g., viscosity) of glass-forming and/or magma-related oxide melts (3-7) to the role played by atomic packing in determining the elastic behavior of glass (8-10). In the case of open glass-forming structures, the network connectivity often follows from Zachariasen's rules (11), but there is no reliable guide for predicting the conditions under which transformations occur in the character of network-forming motifs, e.g., from AO 3 to AO 4 or from AO 4 to AO 6 polyhedra.With increasing density, oxygen-oxygen interactions are expected to manifest themselves in the structural transformations that occur (12), but the nature of this role is unknown. For example, the oxygen atom number density ρ O will depend on the type of network-forming motifs, can be altered by adding network modifiers, and will increase with density. Nevertheless, a plot of ρ O versus the measured mean A-O coordination number n O A for network-forming structural motifs does not offer a basis for generalization (Fig. 1). It will be shown, however, that if the data are scaled by the volume occupied by an oxide ion V O , and an adjustment is made for the volume occupied by any network-modifying atoms (i.e., atoms other than oxygen that are not at the centers of network-forming motifs), then the resultant oxygenpacking fraction η O does offer a means for rationalizing the structural transformations that occur. An important proviso is that a constant oxide ion size cannot be assumed. Instead, the oxide ion environment has a profound influence as evidenced by the instability of these ions in the gas phase but their omnipresence in condensed matter (13,14). This variability was recognized in the construction of well-known tables of ionic radii (15, 16), although a constant size was assumed for a given oxide ion coordination number. The variability of the oxide ion size is also a key theme in the development of transferable aspherical ion models which have been successful in accounting for many of the structure-related properties of oxide materials (13,14). In the following we use an empirical approach to tac...

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Temperature effects on non-bridging oxygen and aluminum coordination number in calcium aluminosilicate glasses and melts

Cited by 168 publications

References 86 publications

Effect of Potassium Oxide Addition on Viscosity of Calcium Aluminosilicate Melts at 1673–1873 K

Effect of Potassium Oxide Addition on Viscosity of Calcium Aluminosilicate Melts at 1673–1873 K

Simplicity in melt densification in multicomponent magmatic reservoirs in Earth’s interior revealed by multinuclear magnetic resonance

Packing and the structural transformations in liquid and amorphous oxides from ambient to extreme conditions

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