Phase Equilibria and Crystal Chemistry in Portions of the System SrO-CaO-Bi2O3-CuO, Part II-The System SrO-Bi2O3-CuO.
New data are presented on the phase equilibria and crystal chemistry of the binary systems Sr0-Bi203and SrO-CuO and the ternary system SrO-Bi2O3-CuO. Symmetry data and unit cell dimensions based on single crystal and powder x-ray diffraction measurements are reported for all the binary SrO-Bi2O3phases, including a new phase identified as Sr6Bi2O9. The ternary system contains at least four ternary phases which can be formed in air at ~900 °C. These are identified as Sr2Bi2CuO6, Sr8Bi4Cu5O19+x, Sr3Bi2Cu2O8and a solid solution (the Raveau phase) which, for equilibrium conditions at ~900 °C, corresponds approximately to the formula Sr1.8-xBi2.2+xCu1±x/2Oz.(0.0⩽x⩽~0.15). Superconductivity in this phase apparently occurs only in compositions that correspond to negative values ofx. Compositions that lie outside the equilibrium Raveau-phase field often form nearly homogeneous Raveau-phase products. Typically this occurs after relatively brief heat treatments, or in crystallization of a quenched melt.
National Institute of Standards and Technology, Gaithersburg, MD 20899.
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RS
Roth
National Institute of Standards and Technology, Gaithersburg, MD 20899.
C J
CJ
Rawn
National Institute of Standards and Technology, Gaithersburg, MD 20899.
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Burton
National Institute of Standards and Technology, Gaithersburg, MD 20899.
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Beech
SrO-CaO-Bi2O3-CuO; crystal chemistry; phase equilibria; single crystal diffraction; superconductivity; x-ray powder diffraction