Title :
Phase chemistry and microstructure evolution in silver-clad (Bi/sub 2-x/Pb/sub x/)Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ wires
Author :
Luo, J.S. ; Merchant, N. ; Escorcia-Aparicio, E. ; Maroni, V.A. ; Gruen, D.M. ; Tani, B.S. ; Riley, G.N., Jr. ; Carter, W.L.
Author_Institution :
Argonne Nat. Lab., IL, USA
fDate :
3/1/1993 12:00:00 AM
Abstract :
The reaction kinetics and mechanism that control the conversion of (Bi,Pb)/sub 2/Sr/sub 2/CaCu/sub 2/O/sub z/ (Bi-2212)+alkaline earth cuprates to (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ (Bi-2223) in silver-clad wires were investigated as a function of equilibration temperature and time at a fixed oxygen partial pressure (7.5% O/sub 2/). Measured values for the fractional conversion of Bi-2223 versus time were evaluated based on the Avrami equation. SEM studies of partially and fully converted wires suggest: (1) the transformation to Bi-2223 is two-dimensional and controlled by a diffusion process; (2) liquid phases are present during part of the Bi-2212 to Bi-2223 conversion; and (3) growth of the (Sr,Ca)/sub 14/Cu/sub 24/O/sub 41/ phase accompanies Bi-2223 formation.<>
Keywords :
bismuth compounds; calcium compounds; composite superconductors; crystal microstructure; high-temperature superconductors; lead compounds; scanning electron microscope examination of materials; silver; strontium compounds; Avrami equation; Bi/sub 2-x/Pb/sub x/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/-Ag; SEM; clad wires; diffusion process; equilibration temperature; fractional conversion; high temperature superconductivity; liquid phases; microstructure; phase chemistry; reaction kinetics; Chemistry; Earth; Equations; Kinetic theory; Microstructure; Pressure control; Strontium; Temperature control; Time measurement; Wires;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
