Search NASA⌕ Search

SEARCH · Search NASA

Results for “Y2Ti2O7”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

Materials Data on Y2Ti2O7 by Materials Project

Y2Ti2O7 crystallizes in the monoclinic P2 space group. The structure is three-dimensional. there are six inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Y–O bond distances ranging from 2.20–2.48 Å. In the second Y3+ site, Y3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Y–O bond distances ranging from 2.21–2.44 Å. In the third Y3+ site, Y3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Y–O bond distances ranging from 2.26–2.47 Å. In the fourth Y3+ site, Y3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Y–O bond distances ranging from 2.17–2.72 Å. In the fifth Y3+ site, Y3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Y–O bond distances ranging from 2.15–2.37 Å. In the sixth Y3+ site, Y3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Y–O bond distances ranging from 2.37–2.72 Å. There are six inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There is two shorter (1.79 Å) and two longer (1.96 Å) Ti–O bond length. In the second Ti4+ site, Ti4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ti–O bond distances ranging from 1.81–2.45 Å. In the third Ti4+ site, Ti4+ is bonded in a tetrahedral geometry to four O2- atoms. There is one shorter (1.82 Å) and three longer (1.83 Å) Ti–O bond length. In the fourth Ti4+ site, Ti4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ti–O bond distances ranging from 1.83–2.24 Å. In the fifth Ti4+ site, Ti4+ is bonded to six O2- atoms to form corner-sharing TiO6 octahedra. There are a spread of Ti–O bond distances ranging from 1.83–2.17 Å. In the sixth Ti4+ site, Ti4+ is bonded to four O2- atoms to form distorted corner-sharing TiO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 32°. There is two shorter (1.83 Å) and two longer (1.86 Å) Ti–O bond length. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded to two Y3+ and two Ti4+ atoms to form distorted OY2Ti2 tetrahedra that share corners with three OY2Ti2 tetrahedra and edges with two OY3Ti tetrahedra. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Y3+ and one Ti4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two Y3+ and one Ti4+ atom. In the fourth O2- site, O2- is bonded to three Y3+ and one Ti4+ atom to form distorted OY3Ti tetrahedra that share corners with three OY3Ti tetrahedra and an edgeedge with one OY2Ti2 tetrahedra. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two Y3+ and one Ti4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Y3+ and one Ti4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Y3+ and two Ti4+ atoms. In the eighth O2- site, O2- is bonded to two Y3+ and two Ti4+ atoms to form a mixture of distorted corner and edge-sharing OY2Ti2 tetrahedra. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to one Y3+ and two Ti4+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to two Y3+ and one Ti4+ atom. In the eleventh O2- site, O2- is bonded in a 3-coordinate geometry to two Y3+ and one Ti4+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two Y3+ and one Ti4+ atom. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to two Y3+ and two Ti4+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Y3+ and two Ti4+ atoms.

36 MATERIALS SCIENCE↗

Synthesis of Nano-Oxide Precipitates by Implantation of Ti, Y and O Ions in Fe-10%Cr: Towards an Understanding of Precipitation in Oxide Dispersion-Strengthened (ODS) Steels

The properties of oxide dispersion-strengthened steels are highly dependent on the nature and size distribution of their constituting nano-oxide precipitates. A fine control of the processes of synthesis would enable the optimization of pertinent properties for use in various energy systems. This control, however, requires knowledge of the precise mechanisms of nucleation and growth of the nanoprecipitates, which are still a matter of debate. In the present study, nano-oxide precipitates were produced via the implantation of Y, Ti, and O ions in two different sequential orders in an Fe-10%Cr matrix that was subsequently thermally annealed. The results show that the oxides that precipitate are not necessarily favoured thermodynamically, but rather result from complex kinetics aspects related to the interaction between the implanted elements and induced defects. When Y is implanted first, the formation of nanoprecipitates with characteristics similar to those in conventionally produced ODS steels, especially with a core/shell structure, is evidenced. In contrast, when implantation starts with Ti, the precipitation of yttria during subsequent high-temperature annealing is totally suppressed, and corundum Cr 2 O 3 precipitates instead. Moreover, the systematic involvement of {110} matrix planes in orientation relationships with the precipitates, independently of the precipitate nature, suggests matrix restriction effects on the early stages of precipitation.

36 MATERIALS SCIENCE↗