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Phase Regions and Kinetics of Formation of (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O x in Ag‐Sheathed Tape
Author(s) -
Sung Yeon Soo,
Hellstrom Eric E.
Publication year - 1995
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1995.tb08610.x
Subject(s) - activation energy , kinetics , isothermal process , nucleation , thermodynamics , phase diagram , avrami equation , materials science , phase (matter) , diffusion , oxide , kinetic energy , analytical chemistry (journal) , arrhenius equation , mineralogy , chemistry , metallurgy , physics , organic chemistry , quantum mechanics , chromatography
Ag‐sheathed (Bi,Pb) 2 Sr 2 Ca 2 Cu 3 O, (2223) tapes were made by the oxide‐powder‐in‐tube method. Tapes were heat‐treated isothermally at several different temperatures in 7.5% O 2 /Ar, then quenched into oil to retain the phase assemblages at the reaction temperatures. 2223 formed between ∼810° and ∼837°C. The Avrami equation was applied to describe the kinetics of 2223 formation from a mixture of Bi 2 Sr 2 CaCu 2 O x and nonsuperconducting phases, mainly Ca 2 PbO 4 and CuO. The calculated Avrami exponent, n ∼ 1, indicated that the kinetics in this system could be described as a diffusion‐controlled, two‐dimensional nucleation and growth process. The apparent activation energy for forming 2223 was ∼2900 kJ/mol from ∼817° to ∼825°C and ∼890 kj/mol from ∼825° to ∼837°C. A temperature‐time‐transformation diagram was constructed based on the kinetic data; it describes the transformational behavior of this particular system.