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DOE OSTI2020

Materials Data on SiO2 by Materials Project

SiO2 crystallizes in the orthorhombic C222 space group. The structure is three-dimensional. there are six inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is two shorter (1.63 Å) and two longer (1.65 Å) Si–O bond length. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is two shorter (1.64 Å) and two longer (1.66 Å) Si–O bond length. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is two shorter (1.64 Å) and two longer (1.66 Å) Si–O bond length. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is two shorter (1.64 Å) and two longer (1.66 Å) Si–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the ninth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiO2 by Materials Project

SiO2 is quartz (beta)-like structured and crystallizes in the cubic I-43m space group. The structure is three-dimensional. Si4+ is bonded to four equivalent O2- atoms to form corner-sharing SiO4 tetrahedra. All Si–O bond lengths are 1.62 Å. O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca(SiO2)8 by Materials Project

Ca(SiO2)8 is Low Tridymite-derived structured and crystallizes in the monoclinic Pc space group. The structure is three-dimensional. Ca is bonded in a 4-coordinate geometry to four O atoms. There are a spread of Ca–O bond distances ranging from 2.56–2.70 Å. There are eight inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.64 Å. In the second Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.64 Å. In the third Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the fourth Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.65 Å. In the fifth Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the sixth Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. In the seventh Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. In the eighth Si site, Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. There are sixteen inequivalent O sites. In the first O site, O is bonded in a 2-coordinate geometry to one Ca and two Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the seventh O site, O is bonded in a distorted bent 150 degrees geometry to one Ca and two Si atoms. In the eighth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the ninth O site, O is bonded in a distorted bent 150 degrees geometry to one Ca and two Si atoms. In the tenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the eleventh O site, O is bonded in a distorted bent 150 degrees geometry to one Ca and two Si atoms. In the twelfth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the thirteenth O site, O is bonded in a linear geometry to two Si atoms. In the fourteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiO2 by Materials Project

SiO2 is quartz (alpha)-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eighteen inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is three shorter (1.65 Å) and one longer (1.66 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the seventh Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the eighth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the ninth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the tenth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the eleventh Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is one shorter (1.65 Å) and three longer (1.66 Å) Si–O bond length. In the twelfth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the thirteenth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the fourteenth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the fifteenth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the sixteenth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the seventeenth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the eighteenth Si4+ site, Si4+ is bonded to four O2- atoms to form distorted corner-sharing SiO4 tetrahedra. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. There are thirty-six inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventeenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eighteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the nineteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twentieth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twenty-ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirtieth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirty-first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirty-second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirty-third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirty-fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirty-fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirty-sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiO2 by Materials Project

SiO2 is quartz (alpha)-like structured and crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are four inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.64 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.63 Å) Si–O bond length. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.63 Å) Si–O bond length. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is two shorter (1.61 Å) and two longer (1.63 Å) Si–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the seventh O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiO2 by Materials Project

SiO2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of four trioxidane molecules and two Si14O25 sheets oriented in the (1, 0, 0) direction. In each Si14O25 sheet, there are seven inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is three shorter (1.63 Å) and one longer (1.64 Å) Si–O bond length. In the third Si4+ site, Si4+ is bonded in a water-like geometry to two O2- atoms. There is one shorter (1.64 Å) and one longer (1.65 Å) Si–O bond length. In the fourth Si4+ site, Si4+ is bonded in a distorted see-saw-like geometry to four O2- atoms. There are a spread of Si–O bond distances ranging from 1.66–2.09 Å. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is three shorter (1.63 Å) and one longer (1.64 Å) Si–O bond length. In the sixth Si4+ site, Si4+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There is one shorter (1.62 Å) and two longer (1.65 Å) Si–O bond length. In the seventh Si4+ site, Si4+ is bonded to four O2- atoms to form a mixture of corner and edge-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in an L-shaped geometry to two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in an L-shaped geometry to two equivalent Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Si4+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Si4+ and one O2- atom. The O–O bond length is 1.52 Å. In the tenth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent Si4+ atoms. In the eleventh O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirteenth O2- site, O2- is bonded in a bent 120 degrees geometry to two Si4+ atoms. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the fifteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K(SiO2)2 by Materials Project

K(SiO2)2 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. K is bonded in a trigonal planar geometry to three equivalent O atoms. All K–O bond lengths are 3.18 Å. Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There is three shorter (1.66 Å) and one longer (1.67 Å) Si–O bond length. There are two inequivalent O sites. In the first O site, O is bonded in a linear geometry to two equivalent Si atoms. In the second O site, O is bonded in a linear geometry to three equivalent K and two equivalent Si atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiO2 by Materials Project

SiO2 is Low Tridymite-like structured and crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are eight inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.61–1.64 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the fourth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is three shorter (1.63 Å) and one longer (1.64 Å) Si–O bond length. In the fifth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the sixth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.63 Å) Si–O bond length. In the seventh Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.64 Å. In the eighth Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is three shorter (1.63 Å) and one longer (1.64 Å) Si–O bond length. There are sixteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Si4+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the thirteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fourteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms. In the fifteenth O2- site, O2- is bonded in a linear geometry to two Si4+ atoms. In the sixteenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SiO2 by Materials Project

SiO2 is Low Tridymite-like structured and crystallizes in the tetragonal I4_1/amd space group. The structure is three-dimensional. Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There is two shorter (1.62 Å) and two longer (1.63 Å) Si–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Na(SiO2)3 by Materials Project

Na(SiO2)3 crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Na is bonded in a distorted hexagonal planar geometry to three equivalent O atoms. All Na–O bond lengths are 2.24 Å. Si is bonded to four O atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. There are three inequivalent O sites. In the first O site, O is bonded in a bent 120 degrees geometry to two equivalent Si atoms. In the second O site, O is bonded in a linear geometry to two equivalent Si atoms. In the third O site, O is bonded in a distorted trigonal planar geometry to one Na and two equivalent Si atoms.

36 MATERIALS SCIENCE↗
NASA NTRS2016

Thermochemistry of CaO-MgO-Al2O3-SiO2 (CMAS) and Advanced Thermal and Environmental Barrier Coating Systems

CaO-MgO-Al2O3-SiO2 (CMAS) oxides are constituents in a broad number of materials and minerals which have recently inferred to discussions in materials science, planetary science, geochemistry and cosmochemistry communities. In materials science, there is increasing interest in the degradation studies of thermal (TBC) and environmental (EBC) barrier coatings of gas turbines by molten CMAS. These coatings have been explored to be applied on silicon-based ceramics and composites which are lighter and more temperature capable hot-section materials of gas turbines than the current Ni-based superalloys. The degradation of the coatings occurs when CMAS minerals carried by the intake air into gas turbines, e.g. in aircraft engines, reacts at high temperatures (1000C) with the coating materials. This causes premature failure of the static and rotating components of the turbine engines. We discuss some preliminary results of the reactions between CMAS and Rare-Earth (RE Y, Yb and Gd) oxide stabilized ZrO2 systems, and stability of the resulting oxides and silicates.

CaO-MgO-Al2O3-SiO2 (CMAS)↗
DOE OSTI2020

Enhanced Interfacial Stability of Si Anodes for Li-Ion Batteries via Surface SiO2 Coating

Silicon is a promising alloying anode for lithium-ion batteries owing to its high capacity and low cost. However, its use has been hampered by mechanical failure arising from the large volume change upon cycling and by an insufficiently stable solid-electrolyte interphase (SEI). SEI formation depends on the Si surface, which is often an oxide (SiO x ). In this study we compare three different Si surfaces using Si wafers: 1.3 nm native SiO x , 1.4 nm thermally grown SiO2, and a SiOx-free surface. The oxide-free surface showed the worst electrochemical performance, never exceeding 94% Coulombic efficiency (CE). Furthermore, it also exhibited the thickest SEI and the highest overpotential for lithiation, which correlated with uninhibited electrolyte reduction and the incorporation of P-F species into the SEI. The oxide-coated surfaces performed significantly better, demonstrating a CE above 99% beyond the second cycle, low overpotential for lithiation, and a thinner and more stable SEI. The oxides lower the onset potential for electrolyte reduction, and yield an SEI with fewer P-F species. However, it was found that the CE with the native oxide surface decays from the fifth cycle onwards and correlates with a resurgence of electrolyte reduction. A 1-2 nm thermal SiO 2 coating is optimum for achieving a stable SEI that minimizes side reactions and sustains efficient cycling.

25 ENERGY STORAGE↗
DOE OSTI2024

Temperature effects on the nanoscale thermoelastic response of a SiO2 membrane

We crossed two femtosecond extreme ultraviolet (EUV) pulses on a 100 nm thick amorphous membrane of SiO2, generating transient gratings (TGs) of light intensity with 84 nm spatial periodicity. The EUV TG excitation gave rise to the efficient generation of Lamb waves (LWs) and of a temperature grating, whose dynamics was studied at two different initial sample temperatures, 50 and 300 K. The short penetration depth of the EUV excitation pulses turned into a strong non-uniformity in the actual temperature as a function of the depth from the sample surface. At the lowest temperature, the LW frequencies presented a sizable shift in time due to the thermal equilibration along the membrane thickness. The analysis of the EUV TG waveforms allowed us to determine the decay time of the thermal grating and the sound attenuation coefficient, both found in reasonable agreement with the literature. The results show how EUV TG can provide information of non-equilibrium thermoelastic dynamics in thin membranes transparent to optical radiation.

Materials Science↗
NASA NTRS1972

Disproportionation of Fe2SiO4 to 2FeO plus SiO2 at pressures up to 250kbar and temperatures up to 3000 C

A sample of Fe2SiO4 (spinel) at approximately 250 kbar in a diamond anvil press was heated to approximately 3000 C for a duration of some ms using a focused light beam from a pulsed ruby laser. After quenching and unloading, X-ray diffraction patterns indicated that the portion of the sample that had been heated contained wustite and stishovite. A sample of Fe2SiO4 (fayalite) at approximately 200 kbar in a diamond anvil press has been heated to 800 C for 20 min in a furnace. After quenching and unloading, the sample was found to have concentric zones with the fayalite phase at the lowest pressure, the spinel phase at the intermediate pressure, and a dark region at the center where the pressure was highest. An X-ray diffraction pattern of the dark central region indicated the presence of wustite. A microprobe analysis of a sample produced by a similar procedure indicated that SiO2 is apparently evolved along with wustite but is not sufficiently crystalline to be detected by X-ray diffraction.

Bassett, W. A.↗
NASA NTRS1975

Silicon ions below 100 km - A case for SiO2/+/

An investigation regarding the occurrence of Si ions is conducted, taking into account an unusual metal ion structure observed during a meteor shower event. Loss processes involving silicon oxides are considered in connection with a study of the reasons for the unique Si(+) distribution found. It is suggested that below 100 km Si(+) is rapidly depleted by two- and three-body reactions with molecular oxygen, forming SiO2(+) which then recombines.

Goldberg, R. A.↗
NASA NTRS1975

Ion-implantation effect on time-dependent breakdown in SiO2

It was experimentally demonstrated that the field emission of positive ions from the metal SiO2 interface in MOS structures can be controlled by introducing a positive charge in a small ion-implantation dose to a shallow depth below the metal electrode. Considerable improvement of time-dependent breakdown was noted in structures implanted in this manner as opposed to nonimplanted ones. This experiment confirms the model proposed by Li and Maserjian (1975) for radiation effect on time-dependent breakdown.

Li, S. P.↗
NASA NTRS1976

The origin of chondrules - Experimental investigation of metastable liquids in the system Mg2SiO4-SiO2

Laser-melted magnesium silicate droplets were supercooled 400-750 C below their equilibrium liquidus temperatures before crystallization and their texture was compared with that of meteoritic and lunar chondrules. Crystal morphology, width and texture were studied in relation to nucleation temperature and bulk composition. It was found that the only phase to nucleate from the forsterite-enstatite normative melts was forsterite. Highly siliceous glass, about 65% SiO2 by weight, was identified interstitially to the forsterite crystals in seven of the MgSiO4 spherules and was thought to be present in all.

Blander, M.↗