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Materials Data on BaY2CuO5 by Materials Project

Y2BaCuO5 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.64–3.31 Å. There are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to seven O2- atoms to form distorted YO7 pentagonal bipyramids that share corners with four equivalent YO7 pentagonal bipyramids, edges with three equivalent YO7 pentagonal bipyramids, edges with two equivalent CuO5 square pyramids, a faceface with one YO7 pentagonal bipyramid, and a faceface with one CuO5 square pyramid. There are a spread of Y–O bond distances ranging from 2.31–2.39 Å. In the second Y3+ site, Y3+ is bonded to seven O2- atoms to form distorted YO7 pentagonal bipyramids that share corners with five equivalent CuO5 square pyramids, edges with five YO7 pentagonal bipyramids, an edgeedge with one CuO5 square pyramid, and a faceface with one YO7 pentagonal bipyramid. There are a spread of Y–O bond distances ranging from 2.29–2.40 Å. Cu2+ is bonded to five O2- atoms to form CuO5 square pyramids that share corners with five equivalent YO7 pentagonal bipyramids, edges with three YO7 pentagonal bipyramids, and a faceface with one YO7 pentagonal bipyramid. There are a spread of Cu–O bond distances ranging from 2.00–2.30 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three equivalent Ba2+, two Y3+, and one Cu2+ atom to form a mixture of distorted edge and corner-sharing OBa3Y2Cu octahedra. The corner-sharing octahedral tilt angles are 5°. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+, three Y3+, and one Cu2+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+, three Y3+, and one Cu2+ atom.

36 MATERIALS SCIENCE↗

Grain orientation studies in superconductors

Grain oriented fabrication of ceramics utilizes the presence of some form of anisotropy in the particles of the starting material to obtain textured microstructures. The molten salt, or flux method, a popular technique for growing crystals and particles with anisotropic morphology, is utilized in this study. The formation of Ba2YCu3O(7-x) in the presence of molten salts of Na, K, Li belonging to chloride and sulfate systems does not appear feasible in the temperature range up to 900 C. Researchers also present the results of studies in using BaY2CuO5 as seed crystals in the formation of Ba2YCu3O(7-x) wherein BaY2CuO5 has been observed to have better stability in water and against most of the salts as compared to Ba2YCu3O(7-x). Additional results of molten salt processing of bismuth systems are also presented.

Gopalakrishnan, Sudhakar↗