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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Sound speed and refractive index of amorphous CaSiO3 upon pressure cycling to 40 GPa

Abstract Brillouin spectroscopy at room temperature and pressures up to 40 GPa documents nearly identical elasticity and refractive index of amorphous CaSiO3 created by two different methods: temperature-quenching the melt at ambient pressure and pressure-amorphizing crystalline wollastonite at room temperature. We find reproducible hysteresis of 0 to 8% on pressure cycling that is small relative to the 30 to 60% changes in shear and longitudinal wave velocities over this pressure range. Together with observed changes in refractive index and previous results from Raman spectroscopy, these measurements reveal a continuous and reversible change in atomic packing induced by pressure. Unlike many other silicate glasses, amorphous CaSiO3 exhibits highly reproducible properties, behaving smoothly and reversibly under pressure cycling and possessing similar structure and elasticity regardless of synthesis paths for the starting material, which suggests that the amorphous solid may mimic the liquid over the pressure range investigated.

Geochemistry & Geophysics↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to eight O2- atoms to form distorted CaO8 hexagonal bipyramids that share corners with two equivalent CaO8 hexagonal bipyramids, corners with two equivalent SiO4 tetrahedra, edges with six equivalent CaO8 hexagonal bipyramids, and edges with four SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.32–2.68 Å. In the second Ca2+ site, Ca2+ is bonded to eight O2- atoms to form distorted CaO8 hexagonal bipyramids that share corners with two CaO8 hexagonal bipyramids, corners with two SiO4 tetrahedra, edges with six CaO8 hexagonal bipyramids, and edges with four SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.29–2.67 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent CaO8 hexagonal bipyramids, corners with two equivalent SiO4 tetrahedra, and edges with four CaO8 hexagonal bipyramids. There is two shorter (1.60 Å) and two longer (1.68 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two CaO8 hexagonal bipyramids, corners with two SiO4 tetrahedra, and edges with four CaO8 hexagonal bipyramids. There are a spread of Si–O bond distances ranging from 1.60–1.68 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Si4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 is (Cubic) Perovskite-like structured and crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent SiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.47–2.64 Å. Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and faces with eight equivalent CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–8°. There is four shorter (1.80 Å) and two longer (1.81 Å) Si–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four equivalent Ca2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ca2+ and two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 crystallizes in the tetragonal I4/mcm space group. The structure is three-dimensional. Ca2+ is bonded to twelve O2- atoms to form CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent SiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.42–2.70 Å. Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and faces with eight equivalent CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–13°. There is four shorter (1.81 Å) and two longer (1.82 Å) Si–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Ca2+ and two equivalent Si4+ atoms to form a mixture of distorted edge and corner-sharing OCa4Si2 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ca2+ and two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 is (Cubic) Perovskite structured and crystallizes in the cubic Im-3 space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to twelve equivalent O2- atoms to form CaO12 cuboctahedra that share corners with twelve CaO12 cuboctahedra, faces with six CaO12 cuboctahedra, and faces with eight equivalent SiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.46–2.65 Å. In the second Ca2+ site, Ca2+ is bonded to twelve equivalent O2- atoms to form CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent SiO6 octahedra. All Ca–O bond lengths are 2.55 Å. Si4+ is bonded to six equivalent O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and faces with eight CaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 6°. All Si–O bond lengths are 1.81 Å. O2- is bonded in a 2-coordinate geometry to four Ca2+ and two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 is Esseneite-derived structured and crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six SiO4 tetrahedra and an edgeedge with one CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.35–2.48 Å. In the second Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.30–3.01 Å. In the third Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.36–2.75 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent CaO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–64°. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 54°. There are a spread of Si–O bond distances ranging from 1.61–1.70 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent CaO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–64°. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Ca2+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ca2+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and one Si4+ atom. In the eighth O2- site, O2- is bonded to three Ca2+ and one Si4+ atom to form distorted edge-sharing OCa3Si trigonal pyramids. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ca2+ and two Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.36–2.61 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with five SiO4 tetrahedra, edges with two equivalent CaO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.52 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with five SiO4 tetrahedra, edges with two equivalent CaO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.29–2.60 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two CaO6 octahedra, corners with two SiO4 tetrahedra, and edges with two CaO6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are a spread of Si–O bond distances ranging from 1.62–1.69 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four CaO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–61°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four CaO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–62°. There are a spread of Si–O bond distances ranging from 1.60–1.67 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Si4+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ca2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ca2+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Ca2+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Ca2+ is bonded to twelve O2- atoms to form distorted CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent SiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.37–2.75 Å. Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and faces with eight equivalent CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 9–12°. All Si–O bond lengths are 1.81 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ca2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ca2+ and two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ca2+ is bonded to twelve O2- atoms to form distorted CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent SiO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.38–2.73 Å. Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and faces with eight equivalent CaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 10–11°. All Si–O bond lengths are 1.81 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ca2+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four equivalent Ca2+ and two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaSiO3 by Materials Project

CaSiO3 is (Cubic) Perovskite structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Ca2+ is bonded to twelve equivalent O2- atoms to form CaO12 cuboctahedra that share corners with twelve equivalent CaO12 cuboctahedra, faces with six equivalent CaO12 cuboctahedra, and faces with eight equivalent SiO6 octahedra. All Ca–O bond lengths are 2.55 Å. Si4+ is bonded to six equivalent O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and faces with eight equivalent CaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Si–O bond lengths are 1.80 Å. O2- is bonded in a distorted linear geometry to four equivalent Ca2+ and two equivalent Si4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Atomistic insight into the ferroelastic post-stishovite transition by high-pressure single-crystal X-ray diffraction

Abstract The post-stishovite transition is a classic pseudo-proper typed ferroelastic transition with a symmetry-breaking spontaneous strain. This transition has been studied using high-pressure spontaneous strains, optic modes, and elastic moduli (Cij) based on the Landau modeling, but its atomistic information and structural distortion remain poorly understood. Here we have conducted synchrotron single-crystal X-ray diffraction measurements on stishovite crystals up to 75.3 GPa in a diamond-anvil cell. Analysis of the data reveals atomic positions, bond lengths, bond angles, and variations of SiO6 octahedra across the transition at high pressure. Our results show that the O coordinates split at ~51.4 GPa, where the apical and equatorial Si-O bond lengths cross over, the SiO6 octahedral distortion vanishes, and the SiO6 octahedra start to rotate about the c axis. Moreover, distortion mode analysis shows that an in-plane stretching distortion (GM1+ mode) occurs in the stishovite structure at high pressure while a rotational distortion (GM2+ mode) becomes dominant in the post-stishovite structure. These results are used to correlate with elastic moduli and Landau parameters (symmetry-breaking strain e1–e2 and order parameter Q) to provide atomistic insight into the ferroelastic transition. When the bond lengths of two Si-O bonds are equal due to the contribution from the GM1+ stretching mode, C11 converges with C12, and the shear wave VS1[110] polarizing along [110] and propagating along [110] vanishes. Values of e1–e2 and Q are proportional to the SiO6 rotation angle from the occurrence of the GM1+ rotational mode in the post-stishovite structure. Our results on the pseudo-proper type transition are also compared with that for the proper type in albite and improper type in CaSiO3 perovskite. The symmetry-breaking strain, in all these types of transitions, arises as the primary effect from the structural angle (such as SiO6 rotation or lattice constant angle) and its relevant distortion mode in the low-symmetry ferroelastic phase.

Geochemistry & Geophysics↗
NASA NTRS1974

EPR measurement of the effect of glass composition on the oxidation states of europium

An investigation was conducted concerning the dependence of the concentration ratio of Eu(2+) to Eu(3+) on composition for silicate liquids whose compositional end members are CaAl2Si2O8 and MgSiO3, MG2SiO4, CaMgSi2O6, CaMgSiO4, CaSiO3, or Ca2SiO4. The liquids were quenched to produce glasses. An electron paramagnetic resonance spectrometer was used to determine the concentration ratios of Eu(2+) to Eu(3+) in the glasses.

Morris, R. V.↗
NASA NTRS1993

Shock-induced devolatization of calcium sulfate and implications for K-T extinctions

Calcium sulfate devolatization during the impact at Chicxulub, Mexico and dispersal in the stratosphere of the resultant sulfuric acid aerosol have been suggested as a possible mechanism for the Cretaceous-Tertiary extinctions. In this paper, we investigated two shock-induced devolatization reactions of calcium sulfate up to 42 GPa in the laboratory: CaSO4 + SiO2 yields CaSiO3 + SO3(degassed) and CaSO4 yields CaO + SO2(degassed) + 1/2 O2(degassed). We found both to proceed to a much less extent than calculated by equilibrium thermodynamic calculations. Reaction products are found to be 10(exp -2) times those calculated for equilibrium. Consequently our estimate of the amount of sulfur oxides degassed into the atmosphere from shock devolatization of CaS04 in the Chicxulub lithographic section (6x10(exp 15)-2x10(exp 16)g in sulfur mass) is lower by a factor of 70 to 400 than previous estimates; the related environmental stress arising from the resultant global cooling of approximately 4 K and fallout of acid rain does not appear to suffice to explain the widespread K-T extinctions.

Chen, Guangqing↗
NASA NTRS2014

Properties of Desert Sand and CMAS Glass

As-received desert sand from a Middle East country has been characterized for its phase composition and thermal stability. X-ray diffraction analysis showed the presence of quartz (SiO2), calcite (CaCO3), gypsum (CaSO4.2H2O), and NaAlSi3O8 phases in as-received desert sand and showed weight loss of approx. 35 percent due to decomposition of CaCO3 and CaSO4.2H2O when heated to 1400 C. A batch of as-received desert sand was melted into calcium magnesium aluminosilicate (CMAS) glass at approx. 1500 C. From inductively coupled plasma-atomic emission spectrometry, chemical composition of the CMAS glass was analyzed to be 27.8CaO-4MgO-5Al2O3-61.6SiO2-0.6Fe2O3-1K2O (mole percent). Various physical, thermal and mechanical properties of the glass have been evaluated. Bulk density of CMAS glass was 2.69 g/cc, Young's modulus 92 GPa, Shear modulus 36 GPa, Poisson's ratio 0.28, dilatometric glass transition temperature (T (sub g)) 706 C, softening point (T (sub d)) 764 C, Vickers microhardness 6.3 +/- 0.4 GPa, indentation fracture toughness 0.75 +/- 0.15 MPa.m (sup 1/2), and coefficient of thermal expansion (CTE) 9.8 x 10 (exp -6)/degC in the temperature range 25 to 700 C. Temperature dependence of viscosity has also been estimated from various reference points of the CMAS glass using the Vogel-Fulcher-Tamman (VFT) equation. The glass remained amorphous after heat treating at 850 C for 10 hr but crystallized into CaSiO3 and Ca-Mg-Al silicate phases at 900 C or higher temperatures. Crystallization kinetics of the CMAS glass has also been investigated by differential thermal analysis (DTA). Activation energies for the crystallization of two different phases in the glass were calculated to be 403 and 483 kJ/mol, respectively.

Desert sand↗
NASA NTRS2015

Crystallization Kinetics of Calcium-magnesium Aluminosilicate (CMAS) Glass

The crystallization kinetics of a calcium-magnesium aluminosilicate (CMAS) glass with composition relevant for aerospace applications, like air-breathing engines, were evaluated using differential thermal analysis (DTA) in powder and bulk forms. Activation energy and frequency factor values for crystallization of the glass were evaluated. X-ray diffraction (XRD) was used to investigate the onset of crystallization and the phases that developed after heat treating bulk glass at temperatures ranging from 690 to 960 deg for various times. Samples annealed at temperatures below 900 deg remained amorphous, while specimens heat treated at and above 900 deg exhibited crystallinity originating at the surface. The crystalline phases were identified as wollastonite (CaSiO3) and aluminum diopside (Ca(Mg,Al) (Si,Al)2O6). Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were employed to examine the microstructure and chemical compositions of crystalline phases formed after heat treatment.

X-ray diffraction (XRD)↗
NASA NTRS2021

Melting and Crystallization Behavior of CaO-MgO-Al2O3-SiO2 Silicates Relevant to Turbine Engine Applications

The melting and crystallization behavior of four quaternary CaO-MgO-Al2O3-SiO2(CMAS) silicates were investigated. The CaO:SiO2 ratios of these systems were based on various terrestrial sources of ingested particles relevant to gas turbine engine operating environments. Melting behavior was characterized using differential scanning calorimetry, and high temperature intrinsic crystallization products were determined by furnace heat treatments of the glasses at 1200°C, 1300°C, and 1400°C. The silicates exhibited a wide range of melting temperatures from ~1240°C up to ~1500°C, with most of the compositions exhibiting incongruent melting behavior. High temperature crystallization products included CaSiO3,CaAl2Si2O8, Ca2MgSi2O7, and Ca(Mg,Al)Si2O6, although SiO2 was the only crystalline phase observed at 1400°C.

Jamesa L. Stokes↗