Phase Relationships in the BaO-Sm2O3-CuOx System Under 100Pa O2

Published

June 23, 2004

Author(s)

Winnie K. Wong-Ng, Lawrence P. Cook, J Suh, James A. Kaduk

Abstract

By applying controlled atmosphere methods to minimize the presence of carbonate, and CO₂ and H₂O contamination, subsolidus phase equilibria of the BaO-Sm₂O₃-CuOx system at pO₂ = 100 Pa (0.1 % O₂ by volume) were successfully determined. Under carbonate-free conditions, the BaO-Sm₂O₃-CuOx phase diagram at pO₂ = 100 Pa is different from that reported in literature (prepared under air). The BaO-Sm₂O₃-CuOx system consists of five ternary phases. The first phase, (Ba₂-xSmx)CuO₃-z (x= 0 to 0.3), is in the high-BaO region of the phase diagram,. The second phase, Ba₄Sm₂Cu₂Oz, is new insulator phase with a structure comprised of unusual CuO₅ linear chains (orthorhombic Pnn2, a = 11.9718₇C, b= 11.8886₇ C, c = 3.84652₂₁ C, and V = 547.47C3). The structure and the x-ray reference pattern of Ba₄Sm₂Cu₂O₉-z were obtained using the Rietveld refinement technique. Despite the same cation stoichiometry, the third phase, BaSm₂CuO₅ (green-phase), has a different structure from that of the brown phases BaLa₂CuO₅ and BaNd₂CuO₅. The fourth phase, Ba₄SmCu₃Ox, is isostructural with Ba₄YCu₃Ox and has a perovskite-related structure. The fifth phase is the high Tc solid solution series, Ba₂-xSm₁+xCu₃Oz (0.2 > x 0). The Ba₂SmCu₃O₆+z Ba₄SmCu₃Oz tie-line established in this study is different from BaCuO₂+x BaSm₂CuO₅, which is the tie-line frequently observed when samples were prepared in air. This tie-line substantially expands the field of stability of the Ba₂-xSm₁+xCu₃O₆+z superconductor phase into the relatively BaO-rich region of the phase diagram.

Citation

Physica C-Superconductivity and Its Applications

Volume

405

Pub Type

Journals

Keywords

(Ba₄Sm₂Cu₂O_9-z), BaO-Sm₂O₃-CuO_x, crystal structure (Ba₄Sm₂Cu₂O^d, phase diagram, superconductor, x-ray pattern

Citation

Wong-Ng, W. , Cook, L. , Suh, J. and A., J. (2004), Phase Relationships in the BaO-Sm₂O₃-CuO_x System Under 100Pa O₂, Physica C-Superconductivity and Its Applications (Accessed April 26, 2024)