Electron microscopy studies of high Tc phase development in melt-quenched Bi-Ca-Sr-Cu oxides

Journal Article · Mon Jan 01 04:00:00 EST 1990 · Journal of Materials Research; (United States)

DOI:https://doi.org/10.1557/JMR.1990.0039· OSTI ID:7068344

Xu, Z; Han, P D; Chang, L; Asthana, A; Payne, D A ^[1]

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1. Univ. of Illinois, Urbana (United States)

A Bi-Ca-Sr-Cu oxide composition (2:4:2:5) was rapidly solidified from the melt, and the crystallization behavior examined on heat treatment. Annealing conditions were 865C for up to 11 days. The high {Tc} 2,223 phase (105 K) evolved from the 2,122 phase (80K), which in turn developed from the 2,021 phase (12K). The high {Tc} phase developed only in the presence of a liquid phase at 865 C. Lattice imaging was used to follow the conversion of 2,122 phase to 2,223. Date are reported for syntactic intergrowths, which became less frequent with time at temperature. EDS results are consistent with the conversion of 2,122 to 2,223. Crystals of 2,223 could not be grown from the melt, nor crystallized from the solid at temperatures below 820 C. The presence of a Cu- and Ca-rich liquid was essential for the development of 2,223 at 865 C. A tentative model for the formation of 2,223 via a liquid mediated reaction is proposed. EDS confirmed the liquid was rich in Ca and Cu near the solid-liquid interface, and precipitates of secondary phases were identified by SEM, TEM, and XRD methods. The presence of CuO and (Ca,Sr){sub 2}CuO{sub 3} verified the enrichment of Cu and Ca at the solid-liquid interface. The results are consistent with the evolution of structure of a 2,223 from a 2,425 starting composition.

• DOE Contract Number: AC02-76ER01198
• OSTI ID: 7068344
• Journal Information: Journal of Materials Research; (United States), Journal Name: Journal of Materials Research; (United States) Vol. 5:1; ISSN JMREE; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALKALINE EARTH METAL COMPOUNDS
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
HEAT TREATMENTS
HIGH-TC SUPERCONDUCTORS
MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS