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Grain boundary degradation of YBCO superconductors sintered in CO{sub 2}-containing atmospheres

Technical Report ·
DOI:https://doi.org/10.2172/10194903· OSTI ID:10194903
; ;  [1];  [2]; ; ;  [3]
  1. Argonne National Lab., IL (United States)
  2. New Mexico Inst. of Mining and Metallurgy, Socorro, NM (United States). Dept. of Materials and Metallurgical Engineering
  3. San Jose State Univ., CA (United States). Dept. of Materials Engineering
The transport critical current density (J{sub c}) of YBCO superconductors decreased with increasing CO{sub 2} partial pressure in the sintering atmosphere and ultimately reached zero, even though magnetization measurements showed that the bulk of the samples with zero J{sub c} remained superconducting. The microstructure and composition of the samples was investigated by high resolution transmission electron microscopy and secondary-ion mass spectroscopy (SIMS). Microbeam SIMS indicated carbon segregation at grain boundaries (GBs). Approximately 10% of the GBs were coated with a thin layer of a second phase, deduced to be BaCuO{sub 2} and BaCu{sub 2}O{sub 2}. Near some grain boundaries, the structure was tetragonal within several tens of nm of the boundaries. The degradation of J{sub c} is discussed in terms of the partial pressure of CO{sub 2} and the processing temperatures. Detailed examination of GB microstructures is given in this paper.
Research Organization:
Argonne National Lab., IL (United States)
Sponsoring Organization:
USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
DOE Contract Number:
W-31109-ENG-38
OSTI ID:
10194903
Report Number(s):
ANL/ET/CP--78725; CONF-931142--4; ON: DE94003206; CNN: Contract DMR88-09854
Country of Publication:
United States
Language:
English