Results for “BaY2O4” | Engineering Papers

DOE OSTI2020

Materials Data on BaY2O4 by Materials Project

BaY2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.74–2.96 Å. There are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing YO6 octahedra. The corner-sharing octahedra tilt angles range from 50–58°. There are a spread of Y–O bond distances ranging from 2.27–2.36 Å. In the second Y3+ site, Y3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing YO6 octahedra. The corner-sharing octahedra tilt angles range from 50–58°. There are a spread of Y–O bond distances ranging from 2.28–2.37 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Y3+ atoms. In the second O2- site, O2- is bonded to two equivalent Ba2+ and three equivalent Y3+ atoms to form distorted edge-sharing OBa2Y3 square pyramids. In the third O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three Y3+ atoms. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ba2+ and three equivalent Y3+ atoms.

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.↗