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5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Sc2Si2O7 by Materials Project

Sc2Si2O7 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Sc3+ is bonded to six O2- atoms to form distorted ScO6 pentagonal pyramids that share corners with six equivalent SiO4 tetrahedra and edges with three equivalent ScO6 pentagonal pyramids. There are a spread of Sc–O bond distances ranging from 2.10–2.21 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six equivalent ScO6 pentagonal pyramids and a cornercorner with one SiO4 tetrahedra. There is one shorter (1.62 Å) and three longer (1.65 Å) Si–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sc3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Sc3+ and one Si4+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sc2Si2O7 by Materials Project

Sc2Si2O7 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Sc3+ is bonded to eight O2- atoms to form distorted ScO8 hexagonal bipyramids that share edges with six equivalent ScO8 hexagonal bipyramids and edges with six equivalent SiO6 octahedra. There are two shorter (2.03 Å) and six longer (2.34 Å) Sc–O bond lengths. Si4+ is bonded to six equivalent O2- atoms to form SiO6 octahedra that share corners with six equivalent SiO6 octahedra and edges with six equivalent ScO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 46°. All Si–O bond lengths are 1.80 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Sc3+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded to four equivalent Sc3+ atoms to form corner-sharing OSc4 tetrahedra.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Environmental Barrier Coating Surface Temperature Mapping Using a Compatible Er-Doped Sc 2 SiO 5 Temperature-Sensing Layer

Accurate surface temperature-mapping capabilities in the 1300 to 1500 °C range are needed for SiC/SiC ceramic matrix composites protected by environmental barrier coatings (EBCs) under testing in turbine engine environment facilities. The strong background thermal radiation at these higher temperatures is a challenging issue. Er-doped Y 2 SiO 5 was previously shown to be capable of achieving luminescence lifetime-based temperature mapping up to 1560 °C as a standalone material. However, compatibility issues between an Er-doped Y 2 SiO 5 surface temperature sensing layer and an underlying Sc 2 Si 2 O 7 -based EBC topcoat limited temperature mapping of the EBC surface to a maximum of 1380 °C. Therefore, an Er-doped Sc 2 SiO 5 temperature sensing layer has been subsequently developed with better compatibility with the Sc2Si2O7-based EBC topcoat. Localized spot temperature measurements as well as luminescence lifetime imaging-based temperature mapping were demonstrated up to 1535 °C from a 15 µm thick Er-doped Sc 2 SiO 5 layer at the surface of a Sc2Si2O7-based EBC topcoat, a significant improvement over the Er-doped Y2SiO5 layer 1380 °C temperature sensing limit. No degradation of the Er-doped Sc 2 SiO 5 temperature sensing surface layer was observed.

temperature measurement↗
NASA NTRS1990

High-temperature deformation and microstructural analysis for Si3N4-Sc2O3

It was indicated that Si3N4 doped with Sc2O3 may exhibit high temperature mechanical properties superior to Si3N4 systems with various other oxide sintered additives. High temperature deformation of samples was studied by characterizing the microstructures before and after deformation. It was found that elements of the additive, such as Sc and O, exist in small amounts at very thin grain boundary layers and most of them stay in secondary phases at triple and multiple grain boundary junctions. These secondary phases are devitrified as crystalline Sc2Si2O7. Deformation of the samples was dominated by cavitational processes rather than movements of dislocations. Thus the excellent deformation resistance of the samples at high temperature can be attributed to the very small thickness of the grain boundary layers and the crystalline secondary phase.

Cheong, Deock-Soo↗
NASA NTRS1992

High-temperature deformation and microstructural analysis for silicon nitride-scandium(III) oxide

It was indicated that Si3N4 doped with Sc2O3 may exhibit high temperature mechanical properties superior to Si3N4 systems with various other oxide sintered additives. High temperature deformation of samples was studied by characterizing the microstructures before and after deformation. It was found that elements of the additive, such as Sc and O, exist in small amounts at very thin grain boundary layers and most of them stay in secondary phases at tripple and multiple grain boundary junctions. These secondary phases are devitrified as crystalline Sc2Si2O7. Deformation of the samples was dominated by cavitational processes rather than movements of dislocations. Thus the excellent deformation resistance of the samples at high temperature can be attributed to the very small thickness of the grain boundary layers and the crystalline secondary phase.

Cheong, Deock-Soo↗