Abstract
Silver-sheathed powder-in-tube processed tapes and thick films of the Bi/sub 2/Sr/sub 2/Ca/sub 1/Cu/sub 2/O/sub 8/spl plusmn//spl delta//-type (Bi-2212) superconductor have been annealed under high temperature, high oxygen fugacity (i.e.fO/sub 2/>0.1 MPa) conditions. At sufficiently high temperatures and oxygen fugacities, the Bi-2212 phase decomposes into a mixture of solid oxides: a Bi/sub 2/(Sr,Ca)/sub 2/Cu/sub 1/O/sub 8/spl plusmn//spl delta//-type (Bi-2201) phase, an alkaline-earth bismuthate Bi/sub 9/Sr/sub 1/1Ca/sub 5/O/sub y/-type (Bi-91_1_5) phase and CuO. Subsequent reformation of Bi-2212 in pure, flowing oxygen at 0.1 MPa and 860/spl deg/C has yielded plate-like grains with enhanced 00l texture (as discerned from X-ray pole figure analyses and electron microscopy). The values of oxygen fugacity leading to sub-solidus decomposition and reformation of Bi-2212 at 500 to 860/spl deg/C are given. XRD and SEM analyses, as well as preliminary critical current measurements of decomposed and reformed Bi-2212 tapes, are presented.
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