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Retrograde Densification in Bi 2 Sr 2 CaCu 2 O 8 Superconductors
Author(s) -
Johnson David W.,
Rhodes Warren W.
Publication year - 1989
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.1151-2916.1989.tb06086.x
Subject(s) - sintering , materials science , microstructure , atmospheric temperature range , crystallite , superconductivity , phase (matter) , oxide , high temperature superconductivity , composite material , mechanical strength , transition temperature , mineralogy , metallurgy , chemistry , condensed matter physics , thermodynamics , physics , organic chemistry
Bi 2 Sr 2 CaCu 2 O 8 was prepared using the mixed oxide‐carbonate method and sintered at temperatures ranging from 850° to 911°C. The samples were characterized for density, mechanical strength, phase composition, microstructure, and superconducting transition temperatures. A unique retrograde densification characteristic is demonstrated in the temperature range 850° to 890°C whereby the material first becomes less dense as the sintering temperature is raised, and only in a narrow temperature range from 900° to 905°C does the material densify then with the formation of a liquid phase. The retrograde densification mechanism is shown to be that of the formation of thin platelike crystallites which grow in a randomly oriented fashion, thus pushing the structure apart. This retrograde densification, coupled with a narrow sintering range overlapping the melting temperature, makes this compound a difficult one to process.