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Title: Method of manufacture of single phase ceramic superconductors

A ceramic superconductor is produced by close control of oxygen partial pressure during sintering of the material. The resulting microstructure of YBa.sub.2 Cu.sub.3 O.sub.x indicates that sintering kinetics are enhanced at reduced p(O.sub.2) and that because of second phase precipitates, grain growth is prevented. The density of specimens sintered at 910.degree. C. increased from 79 to 94% theoretical when p(O.sub.2) was decreased from 0.1 to 0.0001 MPa. The increase in density with decrease in p(O.sub.2) derives from enhanced sintering kinetics, due to increased defect concentration and decreased activation energy of the rate-controlling species undergoing diffusion. Sintering at 910.degree. C resulted in a fine-grain microstructure, with an average grain size of about 4 .mu.m. Post sintering annealing in a region of stability for the desired phase converts the second phases and limits grain growth. The method of pinning grain boundaries by small scale decompositive products and then annealing to convert its product to the desired phase can be used for other complex asides. Such a microstructure results in reduced microcracking, strengths as high as 230 MPa and high critical current density capacity.
Inventors:
 [1];  [2];  [3];  [3]
  1. (Naperville, IL)
  2. (Glen Ellyn, IL)
  3. (Downers Grove, IL)
Issue Date:
OSTI Identifier:
869804
Assignee:
University of Chicago (Chicago, IL) ANL
Patent Number(s):
US 5401712
Contract Number:
W-31109-ENG-38
Research Org:
Argonne National Laboratory (ANL), Argonne, IL
Country of Publication:
United States
Language:
English
Subject:
method; manufacture; single; phase; ceramic; superconductors; superconductor; produced; close; control; oxygen; partial; pressure; sintering; material; resulting; microstructure; yba; cu; indicates; kinetics; enhanced; reduced; precipitates; grain; growth; prevented; density; specimens; sintered; 910; degree; increased; 79; 94; theoretical; decreased; 0001; mpa; increase; decrease; derives; due; defect; concentration; activation; energy; rate-controlling; species; undergoing; diffusion; resulted; fine-grain; average; size; post; annealing; region; stability; desired; converts; phases; limits; pinning; boundaries; scale; decompositive; products; convert; product; complex; asides; results; microcracking; strengths; 230; critical; current; capacity; ceramic superconductor; average grain; desired phase; oxygen partial; current density; grain boundaries; grain size; partial pressure; critical current; single phase; activation energy; grain growth; close control; ceramic superconductors; resulting microstructure; phase ceramic; phase precipitate; ceramic superco; /505/252/

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