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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Synthesis and ion-irradiation tolerance of the Dy2TiO5 polymorphs

In developing improvements in nuclear fuels, work has been conducted in replacing boron with lanthanides to act as neutron absorbent materials. To further this development for the first time the three major polymorphs of Dy2TiO5 have been fabricated as bulk, single-phase materials in a systematic study. Crystal structure refinement has been carried out from powder x-ray diffraction data, with further structural detail attained via electron diffraction. A cubic phase, defect-pyrochlore, Fd-3m space group, was found with cell parameter a = 10.2996 (1) angstrom and oxygen x48f positional parameter = 0.331 (1). Dy2TiO5 was also fabricated as a bulk, single-phase compound with hexagonal symmetry, P6(3)/mmc space group, with cell parameters a = b = 3.6307(2), c = 11.8963(8) angstrom. The radiation response for each of the polymorphs has been investigated in-situ via 1 MeV Kr - ion-irradiation and transmission electron microscopy characterisation at the IVEM-TANDEM facility, Argonne National Laboratory. Critical temperatures, T-c, for maintaining crystallinity during irradiation were determined and showed Dy2TiO5 with either orthorhombic or cubic symmetry to perform the best, with the lowest T-c values of 711 and 761 K respectively when compared with the hexagonal form. These relatively low T-c values may be attributed to different characteristics for each phase; high anti-site defect formation energy for the orthorhombic symmetry, and the ability to accommodate disorder for the cubic symmetry.

Burnable poison↗
DOE OSTI2020

Materials Data on Dy2TiO5 by Materials Project

Dy2TiO5 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. Dy3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Dy–O bond distances ranging from 2.19–2.58 Å. Ti4+ is bonded to six O2- atoms to form corner-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are a spread of Ti–O bond distances ranging from 1.96–2.08 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Dy3+ and one Ti4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Dy3+ and one Ti4+ atom. In the third O2- site, O2- is bonded to two equivalent Dy3+ and two equivalent Ti4+ atoms to form distorted corner-sharing ODy2Ti2 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy2TiO5 by Materials Project

Dy2TiO5 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Dy3+ is bonded to six O2- atoms to form distorted DyO6 pentagonal pyramids that share a cornercorner with one TiO6 octahedra, corners with three equivalent DyO6 pentagonal pyramids, edges with three equivalent TiO6 octahedra, and edges with three equivalent DyO6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 31°. There are a spread of Dy–O bond distances ranging from 2.19–2.40 Å. Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with two equivalent DyO6 pentagonal pyramids, and edges with six equivalent DyO6 pentagonal pyramids. The corner-sharing octahedral tilt angles are 32°. There are a spread of Ti–O bond distances ranging from 1.87–2.13 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Dy3+ and one Ti4+ atom. In the second O2- site, O2- is bonded to three equivalent Dy3+ and one Ti4+ atom to form distorted ODy3Ti trigonal pyramids that share a cornercorner with one ODy2Ti2 tetrahedra, corners with three equivalent ODy3Ti trigonal pyramids, edges with two equivalent ODy2Ti2 tetrahedra, and edges with two equivalent ODy3Ti trigonal pyramids. In the third O2- site, O2- is bonded to two equivalent Dy3+ and two equivalent Ti4+ atoms to form distorted ODy2Ti2 tetrahedra that share corners with two equivalent ODy2Ti2 tetrahedra, corners with two equivalent ODy3Ti trigonal pyramids, and edges with four equivalent ODy3Ti trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Dy2TiO5 by Materials Project

Dy2TiO5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Dy3+ sites. In the first Dy3+ site, Dy3+ is bonded to seven O2- atoms to form distorted DyO7 hexagonal pyramids that share corners with two equivalent DyO7 pentagonal bipyramids, a cornercorner with one TiO5 trigonal bipyramid, edges with four equivalent DyO7 hexagonal pyramids, edges with three equivalent DyO7 pentagonal bipyramids, and edges with two equivalent TiO5 trigonal bipyramids. There are a spread of Dy–O bond distances ranging from 2.34–2.37 Å. In the second Dy3+ site, Dy3+ is bonded to seven O2- atoms to form distorted DyO7 pentagonal bipyramids that share corners with two equivalent DyO7 hexagonal pyramids, corners with three equivalent TiO5 trigonal bipyramids, edges with three equivalent DyO7 hexagonal pyramids, edges with two equivalent DyO7 pentagonal bipyramids, and edges with two equivalent TiO5 trigonal bipyramids. There are a spread of Dy–O bond distances ranging from 2.28–2.39 Å. Ti4+ is bonded to five O2- atoms to form distorted TiO5 trigonal bipyramids that share a cornercorner with one DyO7 hexagonal pyramid, corners with three equivalent DyO7 pentagonal bipyramids, corners with two equivalent TiO5 trigonal bipyramids, edges with two equivalent DyO7 hexagonal pyramids, and edges with two equivalent DyO7 pentagonal bipyramids. There are a spread of Ti–O bond distances ranging from 1.79–1.97 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to three Dy3+ and one Ti4+ atom to form distorted ODy3Ti tetrahedra that share corners with nine ODy3Ti tetrahedra and edges with five ODy4 tetrahedra. In the second O2- site, O2- is bonded to four Dy3+ atoms to form ODy4 tetrahedra that share corners with fourteen ODy3Ti tetrahedra and edges with four ODy4 tetrahedra. In the third O2- site, O2- is bonded to two Dy3+ and two equivalent Ti4+ atoms to form distorted ODy2Ti2 tetrahedra that share corners with six ODy3Ti tetrahedra and edges with five ODy4 tetrahedra. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Dy3+ and one Ti4+ atom. In the fifth O2- site, O2- is bonded to three Dy3+ and one Ti4+ atom to form ODy3Ti tetrahedra that share corners with nine ODy3Ti tetrahedra and edges with four ODy2Ti2 tetrahedra.

36 MATERIALS SCIENCE↗