Phase relations in the systems SrO-Y{sub 2}O{sub 3}-CuO-O{sub 2} and CaO-Y{sub 2}O{sub 3}-CuO-O{sub 2} at 1173 K

Journal Article · Mon Aug 01 00:00:00 EDT 1994 · Journal of Phase Equilibria

DOI:https://doi.org/10.1007/BF02647560· OSTI ID:421415

Jacob, K T ^[1]; Waseda, Y ^[2]

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1. Indian Inst. of Science, Bangalore (India)
2. Tohoku Univ., Sendai (Japan)

Phase relations in the systems SrO-Y{sub 2}O{sub 3}-CuO-O{sub 2} and CaO-Y{sub 2}O{sub 3}-CuO-O{sub 2} at 1173 K were established by equilibrating different compositions in flowing oxygen gas at a pressure of 1.01 X 10{sup 5} Pa. The quenched samples were examined by optical microscopy, X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX), and electron spin resonance (ESR). In the system SrO-Y{sub 2}O{sub 3}-CuO-O{sub 2}, except for the limited substitution of Y{sup 3+} for Sr{sup 2+} ions in the ternary oxide Sr{sub 14}Cu{sub 24}O{sub 41}, no new quaternary phase was found to be stable. The compositions corresponding to the solid solution Sr{sub 14-x}Y{sub x}Cu{sub 24}O{sub 41} and the compound SrCuO{sub 2+{delta}} lie above the plane containing SrO, Y{sub 2}O{sub 3}, and CuO, displaced towards the oxygen apex. However, in the system CaO-Y{sub 2}O{sub 3}-CuO-O{sub 2} at 1173 K, all the condensed phases lie on the plane containing CaO, Y{sub 2}O{sub 3}, and CuO, and a new quaternary oxide YCa{sub 2}Cu{sub 3}O{sub 6.5} is present. The quaternary phase has a composition that lies at the center of the non-stoichiometric Held of the analogous phase YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} in the BaO-Y{sub 2}O{sub 3}-CUO-O{sub 2} system. The compound YCa{sub 2}Cu{sub 3}O{sub 6.5} has the tetragonal structure and does not become superconducting at low temperature. Surprisingly, phase relations in the three systems CaO-Y{sub 2}O{sub 3}-CuO-O{sub 2}, SrO-Y{sub 2}O{sub 3}-CuO-O{sub 2}, and BaO-Y{sub 2}O{sub 3}-CuO-O{sub 2} are found to be quite different.

• Sponsoring Organization: USDOE
• OSTI ID: 421415
• Journal Information: Journal of Phase Equilibria, Vol. 15, Issue 4; Other Information: PBD: Aug 1994
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
STRONTIUM OXIDES
PHASE STUDIES
YTTRIUM OXIDES
COPPER OXIDES
CALCIUM OXIDES
OPTICAL MICROSCOPY
X-RAY DIFFRACTION
SUPERCONDUCTORS
PHASE DIAGRAMS