Liquidus diagram of the Ba-Y-Cu-O system in the vicinity of the Ba{sub 2}YCu{sub 3}O{sub 6+x} phase field

Journal Article · Wed Jul 01 04:00:00 EDT 1998 · Journal of Research of the National Institute of Standards and Technology

DOI:https://doi.org/10.6028/jres.103.023· OSTI ID:669843

Wong-Ng, W; Cook, L P ^[1]

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1. National Inst. of Standards and Technology, Gaithersburg, MD (United States)

This paper describes the melting equilibria in the vicinity of the high T{sub c} phase Ba{sub 2}YCu{sub 3}O{sub 6+x}, including evidence for two Ba-Y-Cu-O immiscible liquids. Melting equilibria have been investigated in purified air using a combination of differential thermal analysis (DTA), thermogravimetric analysis (TGA), powder x-ray diffraction (XRD), MgO wick entrapment of liquid for analysis, scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDS), and hydrogen reduction for determination of copper oxidation state. For relatively barium-rich compositions, it was necessary to prepare the starting materials under controlled atmosphere conditions using BaO. A liquidus diagram was derived from quantitative data for the melts involved in various melting reactions. In general the 1/2 (Y{sub 2}O{sub 3}) contents of the melts participating in these equilibria were low (mole fraction <4%). The primary phase field of Ba{sub 2}YCu{sub 3}O{sub 6+x} occurs at a mole fraction of <2.0% 1/2 Y{sub 2}O{sub 3} and lies very close along the BaO-CuO{sub x} edge, extending from a mole fraction of {approx}43% CuO to a mole fraction of {approx}76% CuO. It is divided by a liquid miscibility gap and extends on either side about this gap. The topological sequence of melting reactions associated with the liquidus is presented as a function of temperature. Implications of the growth of Ba{sub 2}YCu{sub 3}O{sub 6+x} crystals are discussed.

• Sponsoring Organization: USDOE
• OSTI ID: 669843
• Journal Information: Journal of Research of the National Institute of Standards and Technology, Journal Name: Journal of Research of the National Institute of Standards and Technology Journal Issue: 4 Vol. 103; ISSN 1044-677X; ISSN JRITEF
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
COPPER OXIDES
CRYSTAL GROWTH
HIGH-TC SUPERCONDUCTORS
MELTING
PHASE DIAGRAMS
PHASE STUDIES
TEMPERATURE DEPENDENCE
YTTRIUM OXIDES