Structural Analysis of SiO2-Al2O3 Glasses

Morikawa, Hideki; Miwa, Shuichiro; Miyake, Michihiro; Μarumo, F.; Sata, Toshiyuki

doi:10.1111/j.1151-2916.1982.tb10361.x

Cited by 81 publications

(61 citation statements)

References 10 publications

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“…As the Al-O bond length in the tetrahedral site is 0.13 Å longer than the Si-O bond length in the tetrahedral site (Shannon 1976), the average first nearestneighbor T-O (T = Si, Al) lengths in SiO 2 -Al 2 O 3 glasses are longer than the Si-O length. These lengths for SA1 and SA2 were between that of SiO 2 glass (1.59 Å; Meade et al 1992) and those of SiO 2 + 25.0 mol% Al 2 O 3 glass Morikawa et al 1982), showing that our results were in agreement with previous studies about T-O lengths at ambient conditions. Brillouin peaks from the transverse acoustic modes of both SA1 and SA2 were observed over the entire pressure range up to 169.…”

Section: Resultssupporting

confidence: 93%

“…The SiO 2 -Al 2 O 3 system is the simplest from among the aluminous silicate systems. A number of previous studies have reported structural features at ambient pressure, as inferred by Raman scattering (Kato 1976;McMillan and Piriou 1982), infrared absorption (Poe et al 1992a;Okuno et al 2005), X-ray diffraction (Morikawa et al 1982;Okuno et al 2005), nuclear magnetic resonance (NMR) spectroscopic techniques (Risbud et al 1987;Sato et al 1991;Poe et al 1992a, b;Sen and Youngman 2004;Weber et al 2008), and by molecular dynamics (MD) computer simulations (Poe et al 1992a, b;Linh and Hoang 2007).…”

Section: Introductionmentioning

confidence: 99%

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Ultrahigh-pressure acoustic wave velocities of SiO2-Al2O3 glasses up to 200 GPa

Ohira

Murakami

Kohara

et al. 2016

Prog. in Earth and Planet. Sci.

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Extensive experimental studies on the structure and density of silicate glasses as laboratory analogs of natural silicate melts have attempted to address the nature of dense silicate melts that may be present at the base of the mantle. Previous ultrahigh-pressure experiments, however, have been performed on simple systems such as SiO 2 or MgSiO 3 , and experiments in more complex system have been conducted under relatively low-pressure conditions below 60 GPa. The effect of other metal cations on structural changes that occur in dense silicate glasses under ultrahigh pressures has been poorly understood. Here, we used a Brillouin scattering spectroscopic method up to pressures of 196.9 GPa to conduct in situ high-pressure acoustic wave velocity measurements of SiO 2 -Al 2 O 3 glasses in order to understand the effect of Al 2 O 3 on pressure-induced structural changes in the glasses as analogs of aluminosilicate melts. From 10 to 40 GPa, the transverse acoustic wave velocity (V S ) of Al 2 O 3 -rich glass (SiO 2 + 20. 5 mol% Al 2 O 3 ) was greater than that of Al 2 O 3 -poor glass (SiO 2 + 3.9 mol% Al 2 O 3 ). This result suggests that SiO 2 -Al 2 O 3 glasses with higher proportions of Al ions with large oxygen coordination numbers (5 and 6) become elastically stiffer up to 40 GPa, depending on the Al 2 O 3 content, but then soften above 40 GPa. At pressures from 40 to~100 GPa, the increase in V S with increasing pressure became less steep than below 40 GPa. Abovẽ 100 GPa, there were abrupt increases in the P-V S gradients (dV S /dP) at 130 GPa in Al 2 O 3 -poor glass and at 116 GPa in Al 2 O 3 -rich glass. These changes resemble previous experimental results on SiO 2 glass and MgSiO 3 glass. Given that changes of dV S /dP have commonly been related to changes in the Si-O coordination states in the glasses, our results, therefore, may indicate a drastic structural transformation in SiO 2 -Al 2 O 3 glasses above 116 GPa, possibly associated with an average Si-O coordination number change to higher than 6. Compared to previous acoustic wave velocity data on SiO 2 and MgSiO 3 glasses, Al 2 O 3 appears to promote a lowering of the pressure at which the abrupt increase of dV S /dP is observed. This suggests that the Al 2 O 3 in silicate melts may help to stabilize those melts gravitationally in the lower mantle.

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Section: Resultssupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Ultrahigh-pressure acoustic wave velocities of SiO2-Al2O3 glasses up to 200 GPa

Ohira

Murakami

Kohara

et al. 2016

Prog. in Earth and Planet. Sci.

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“…Morikawa et al 1982, Brown et al 1995and references therein, Stebbins 1995, McMillan & Wolf 1995. Morikawa et al (1982) carried out an X-ray-scattering study of a number of compositions along the join Al 2 O 3 -SiO 2 . They noted that these glasses are phase-separated into a SiO 2 -rich and an Al 2 O 3 -rich phase.…”

Section: Aluminum (Al 3+ )mentioning

confidence: 99%

The Structure of Silicate Melts: A Glass Perspective

Henderson

2005

The Canadian Mineralogist

126

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Glasses are widely used as analogues for the study of silicate melts. Although they are solid materials, their structure is inherently complex and diffi cult to study. However, progress has been made in elucidating this structure, its relationship to composition, and how it behaves at high temperatures and pressures. Recent research has brought to light some new fi ndings with important implications for natural melts. These include the observation that the structure is dependent upon the type and size of alkali or alkaline-earth cations incorporated into the glass network, with Li behaving very differently than other alkali cations. In addition, the presence of more than one type of alkali cation can cause non-linear physical behavior. Elements such as Al, Ti and Fe, which play important roles in petrological phenomena, can exhibit coordination environments (e.g., 5-fold) or polyhedral arrangements (e.g., triclusters) that are not common in crystalline phases. Furthermore, polyamorphic phase-transitions may occur at high temperature and pressures; the application of new theoretical models like mean fi eld-constraint hypothesis suggests that several glass phenomena, and probably melt phenomena as well, may be related to stress-rigid to fl oppy transitions. The state of understanding of glass structure, although still rudimentary relative to crystalline materials, has grown exponentially over the last few decades, often with geological researchers at the forefront.Keywords: melts, structure, glasses, petrology, spectroscopy, behavior, model. SOMMAIREOn se sert couramment des verres pour étudier les bains fondus silicatés. Quoiqu'ils sont des matériaux solides, leur structure est naturellement complexe et diffi cile à étudier. Toutefois, des progrès ont été faits dans l'étude de cette structure, sa relation à la composition, et son comportement à températures et pressions élevées. Les projets de recherche récents font ressortir les implications importantes aux bains fondus naturels. A titre d'exemple, la structure dépendrait de la sorte et la taille d'ion alcalin ou alcalino-terreux qui se trouve incorporé dans le réseau du verre. Le Li se comporte de façon très différente des autres alcalins. De plus, la présence de plus d'une sorte d'alcalin peut causer des comportements physiques non-linéaires. Les élements tels Al, Ti et Fe, dont l'importance pétrologique est évidente, peuvent adopter une coordinence inhabituelle, cinq par exemple, et un arrangement polyédrique, des groupements par trois, par exemple, qui ne sont pas communs dans les phases cristallines. De plus, des transitions de phases polyamorphiques pourraient avoir lieu à températures et à pressions élevées. L'application de nouveaux modèles théoriques, par exemple le modèle de contrainte moyenne du champ, fait penser que plusieurs phénomènes impliquant les verres, et tout probablement les bains fondus, pourraient résulter de transitions de matériau rigide face aux contraintes à maté-riau déformable. Quoique les connaissances de la structure du ve...

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“…Thus, unlike SiO 2 , Al 3+ ions do not form a network of AlO 4 tetrahedra that are connected with each other via the O atoms at the corners. Instead, different experimental techniques such as nuclear magnetic resonance (NMR) [Lee and Stebbins, 2000;Schmücker et al, 1999;Sen and Youngman, 2004;Stebbins et al, 2005;Stebbins and Xu, 1997; Xue and Kanzaki, 1999] as well as IR and Raman spectroscopy and X-ray scattering [Morikawa et al, 1982;Okuno et al, 2005] found evidence for structural units such as three-fold coordinated oxygen atoms and five-and six-fold coordinated aluminium atoms that are not found in pure silica, unless one considers amorphous silica at very high temperatures, say above 4000 K (see Horbach and Kob, 1999).…”

Section: Introductionmentioning

confidence: 99%

Structure and transport properties of amorphous aluminium silicates: Computer simulation studies

2006

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The structure and transport properties of SiO 2 -Al 2 O 3 melts containing 13 mol% and 47 mol% Al 2 O 3 are investigated by means of large scale molecular dynamics computer simulations. The interactions between the atoms are modelled by a pair potential which is a modified version of the one proposed by Kramer et al. [J. Am. Chem. Soc. 64, 6435 (1991)]. Fully equilibrated melts in the temperature range 6000 K ≥ T > 2000 K are considered as well as glass configurations, that were obtained by a rapid quench from the lowest melt temperatures. Each system is simulated at two different densities in order to study the effect of pressure on structural and dynamic properties. We find that the Al atoms are, like the Si atoms, mainly four-fold coordinated by oxygen. However, the packing of the AlO 4 tetrahedra is very different from that of the SiO 4 tetrahedra, which is reflected by the presence of triclusters (O atoms surrounded by three cations) and edge-sharing AlO 4 tetrahedra. On larger length scales, a micro-segregation occurs, resulting in an Al-rich network percolating through the Si-O network. This is reflected in a prepeak of concentrationconcentration structure factors around 0.5Å −1 (both in the system with 47 mol% and 13 mol% Al 2 O 3 !). We also address the interplay between structure and mass transport. To this end, the behavior of the selfdiffusion constants for the different compositions and densities is studied.

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Structural Analysis of SiO2-Al2O3 Glasses

Cited by 81 publications

References 10 publications

Ultrahigh-pressure acoustic wave velocities of SiO2-Al2O3 glasses up to 200 GPa

Ultrahigh-pressure acoustic wave velocities of SiO2-Al2O3 glasses up to 200 GPa

The Structure of Silicate Melts: A Glass Perspective

Structure and transport properties of amorphous aluminium silicates: Computer simulation studies

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