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



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


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.
Physica C-Superconductivity and Its Applications


(Ba<sub>4</sub>Sm<sub>2</sub>Cu<sub>2</sub>O<sub>9-z</sub>), BaO-Sm<sub>2</sub>O<sub>3</sub>-CuO<sub>x</sub>, crystal structure (Ba<sub>4</sub>Sm<sub>2</sub>Cu<sub>2</sub>O^d, phase diagram, superconductor, x-ray pattern


Wong-Ng, W. , Cook, L. , Suh, J. and A., J. (2004), Phase Relationships in the BaO-Sm<sub>2</sub>O<sub>3</sub>-CuO<sub>x</sub> System Under 100Pa O<sub>2</sub>, Physica C-Superconductivity and Its Applications (Accessed April 14, 2024)
Created June 23, 2004, Updated February 19, 2017