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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on BaCuO2 by Materials Project

BaCuO2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Ba–O bond lengths are 2.79 Å. Cu2+ is bonded in a square co-planar geometry to four equivalent O2- atoms. All Cu–O bond lengths are 2.01 Å. O2- is bonded to four equivalent Ba2+ and two equivalent Cu2+ atoms to form a mixture of distorted face, edge, and corner-sharing OBa4Cu2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCuO2 by Materials Project

BaCuO2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.70–3.09 Å. In the second Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.70–3.09 Å. There are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are a spread of Cu–O bond distances ranging from 1.93–2.09 Å. In the second Cu2+ site, Cu2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are a spread of Cu–O bond distances ranging from 1.93–2.10 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Cu2+ atoms. In the second O2- site, O2- is bonded to four Ba2+ and two Cu2+ atoms to form a mixture of corner, edge, and face-sharing OBa4Cu2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the third O2- site, O2- is bonded to four Ba2+ and two Cu2+ atoms to form a mixture of corner, edge, and face-sharing OBa4Cu2 octahedra. The corner-sharing octahedral tilt angles are 58°. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Cu2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaCuO2 by Materials Project

BaCuO2 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Ba2+ is bonded to seven O2- atoms to form a mixture of distorted corner, edge, and face-sharing BaO7 pentagonal bipyramids. There are a spread of Ba–O bond distances ranging from 2.67–2.88 Å. Cu2+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Cu–O bond distances ranging from 1.89–2.05 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to five equivalent Ba2+ and one Cu2+ atom to form distorted OBa5Cu octahedra that share corners with four equivalent OBa5Cu octahedra, corners with seven equivalent OBa2Cu3 trigonal bipyramids, edges with eight equivalent OBa5Cu octahedra, and faces with two equivalent OBa2Cu3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 8°. In the second O2- site, O2- is bonded to two equivalent Ba2+ and three equivalent Cu2+ atoms to form distorted OBa2Cu3 trigonal bipyramids that share corners with seven equivalent OBa5Cu octahedra, corners with four equivalent OBa2Cu3 trigonal bipyramids, edges with two equivalent OBa2Cu3 trigonal bipyramids, and faces with two equivalent OBa5Cu octahedra. The corner-sharing octahedra tilt angles range from 0–56°.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Synthesis of Y1Ba2Cu3O(sub x) superconducting powders by intermediate phase reaction

One of the more striking problems for the synthesis of the Y1Ba2Cu3Ox compound is the high-temperature decomposition of the BaCO3. This compound is present as raw material or as an intermediate compound in chemical processes such as amorphous citrate, coprecipitation oxalate, sol-gel process, acetate pyrolisis, etc. This fact makes difficult the total formation reaction of the Y1Ba2Cu3Ox phase and leads to the presence of undesirable phases such as the BaCuO2 phase, the 'green phase', Y2BaCuO5 and others. Here, a new procedure to overcome this difficulty is studied. The barium cation is previously combined with yttrium and/or copper to form intermediate compounds which can react between them to give Y1Ba2Cu3Ox. BaY2O4 and BaCu2O3 react according to the equation BaY2O4+3BaCu2O3 yields 2Y1Ba2Cu3Ox. BaY2O4 is a stable compound of the Y2O3-BaO system; BaCu2O3 is an intimate mixture of BaCuO2 and uncombined CuO. The reaction kinetics of these phases have been established between 860 and 920 C. The phase evolution has been determined. The crystal structure of the Y1Ba2Cu3Ox obtained powder was studied. According to the results obtained from the kinetics study the Y1Ba2Cu3Ox the synthesis was performed at temperatures of 910 to 920 C for short treatment times (1 to 2 hours). Pure Y1Ba2Cu3Ox was prepared, which develops orthorombic type I structure despite of the cooling cycle. Superconducting transition took place at 91 K. The sintering behavior and the superconducting properties of sintered samples were studied. Density, microstructure and electrical conductivity were measured. Sintering densities higher than 95 percent D(sub th) were attained at temperatures below 940 C. Relatively fine grained microstructure was observed, and little or no-liquid phase was detected.

Moore, C.↗
NASA NTRS1991

Stability of Y-Ba-Cu-oxide phases in salt flux

The results of an investigation into the possibility of growing YBa2Cu3O7 (or Y123) single crystals from a NaCl-KCl flux (salt flux) are presented. They are compared with results for Y123 crystals grown from a Ba-Cu-oxide flux system. The chosen salt flux composition was 1:1 (NaCl:KCl). The preparation method of the solutes is presented, with particular attention given to the compounds surrounding the Y123 phase, such as Y2BaCuO6 (Y211). Optical microscopy was introduced to study the morphology of the sample; X-ray diffraction was used for phase identification; and a chemical analysis was effected. The Y123, Y211, and BaCuO2 phases were shown to be dissociated in the NaCl-KCl flux, and could not be recrystallized. A small amount of the flux could be added to create large-grain Y123 crystals, but single-crystal growth was not possible in a top-seeded NaCl-KCl solution. This is attributed to significant differences in solubility of the crystal elements, and phase separation caused by CuO crystal formation.

Tao, Y. K.↗