Some observations of the effects of high pressures and temperatures on the stability of YBa sub 2 Cu sub 3 O sub 7 minus x

Journal Article · Fri Jun 01 04:00:00 EDT 1990 · Journal of Applied Physics; (USA)

DOI:https://doi.org/10.1063/1.345088· OSTI ID:6881896

Williams, R K; Alexander, K B; Brynestad, J; Henson, T J; Kroeger, D M; Lindemer, T B; Marsh, G C; Scarbrough, J O ^[1]

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1. Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831 (USA)

Hot isostatic pressing and heat treatments in high-pressure oxygen were used to study the effect of pressure on the stability of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}}. At 875 {degree}C the compound decomposes at an oxygen pressure of about 7 bars. The decomposition involves formation of Y{sub 2}BaCu{sub 3}O{sub 5} and a Ba-Cu oxide phase. Formation of the latter phase involves additional oxidation because this phase can contain as many as 1.5 oxygen atoms per barium atom. The decomposition can most simply be visualized by considering the chemical reaction 2(YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}})+( (1)/(4) +{ital x}{minus}{ital y}/2)O{sub 2}{r arrow}Y{sub 2}BaCuO{sub 5}+Ba{sub 3}Cu{sub 5}O{sub 9.5{minus}{ital y}}. Encapsulated samples also decompose during hot isostatic pressing, but the process appears to be more complex. The compound YBa{sub 2}Cu{sub 4}O{sub 8} was detected in addition to the two products observed in oxygen-treated samples. The reaction above, with YBa{sub 2}Cu{sub 3}O{sub 7{minus}{ital x}} serving as an oxygen source, aids in understanding the microstructural observations for encapsulated samples. Decomposition can be completely reversed by annealing in air for 20 h at 875 {degree}C.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6881896
• Journal Information: Journal of Applied Physics; (USA), Journal Name: Journal of Applied Physics; (USA) Vol. 67:11; ISSN 0021-8979; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
AIR
ALKALINE EARTH METAL COMPOUNDS
ANNEALING
BARIUM COMPOUNDS
BARIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COPPER COMPOUNDS
COPPER OXIDES
DECOMPOSITION
ELEMENTS
FLUIDS
GASES
HEAT TREATMENTS
MEDIUM PRESSURE
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
STABILITY
TRANSITION ELEMENT COMPOUNDS
VERY HIGH TEMPERATURE
YTTRIUM COMPOUNDS
YTTRIUM OXIDES