Title :
Phase formation from liquid phase under various post-annealing conditions
Author :
Nakao, Fumitake ; Osamura, Kozo
Author_Institution :
Dept. of Mater. Sci. & Eng., Kyoto Univ., Japan
fDate :
6/1/2005 12:00:00 AM
Abstract :
The process of phase formation from the liquid phase during post-annealing process has been studied precisely using the powder XRD Rietveld analysis. Mass fraction of the liquid phase was estimated to be 9.3% from the sum of phases that formed during post-annealing. Phase conversion from the liquid phase depended strongly on post-annealing temperature and its regime is mainly divided into two patterns. The first is the conversion into (Bi,Pb)2212 and CaPbO4 and the second is into (Pb,Bi)3221 and AEC. The former regime was observed during post-annealing at around 1073 K, whereas the latter occurred at around 1053 K. The liquid phase existed at (Bi,Pb)2223 grain boundaries is suggested to limit superconducting current path. The increase of critical current by 1.4 times after post-annealing is closely related with the crystallization of grain boundary liquid.
Keywords :
X-ray diffraction; annealing; bismuth compounds; calcination; calcium compounds; critical current density (superconductivity); grain boundaries; high-temperature superconductors; lead compounds; powders; sintering; strontium compounds; superconducting tapes; (PbBi)3Sr2Ca2CuOx; 1053 K; 1063 K; 1073 K; 1095 K; 165.6 ks; 432 ks; 7.2 ks; 72 ks; 77 K; AEC; Bi2PbSr2Ca2Cu3O10; Bi2Sr2CaCu2O8; CaPbO4; critical current; grain boundary liquid crystallization; liquid phase; mass fraction; phase conversion; phase formation; post-annealing conditions; post-annealing temperature; powder XRD Rietveld analysis; superconducting current path; Chemicals; Critical current; Crystallization; Grain boundaries; Heat treatment; Phase estimation; Powders; Superconducting materials; Temperature dependence; X-ray scattering; (Bi,Pb)2223; Rietveld analysis; critical current density; liquid phase; phase conversion; post-anneal;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2005.847476
