Relation Between the Characteristics of Powder and Microstructure; Properties of Ceramics for YBa 2 Cu 2 O x Superconduc
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RELATION BETWEEN THE CHARACTERISTICS OF POWDER AND MICROSTRUCTURE; PROPERTIES OF CERAMICS FOR YBa.Cu.O. SUPERCONDUCTORS Meiyu Zhao, Chengen Li, Xingyun Jin, Yeming Huang, Enji Zhou, Huanyao Ni, Yaoming Qu, Xiangyun Song and Wenjun Wu Shanghai Institute of Ceramics, Chinese Academy of Sciences Shanghai 200050, P.R.China
ABSTRACT Four kinds of YBaCuO.(YBCO) superconducting powders with different particle sizes, shapes and different amounts of twins have been prepared in this work. The density, grain sizes,XRD of have phase composition, configuration of twins of the ceramics been investigated. The relation between the characteristics of YBCO powders and the microstructure, current density of the bulk materials are also discussed. In contrast to the YBCO powder through the prepared by solid state method, the YBCO powders impurities, smatter improved coprecipitation approach have less amounts of twins, as well as the particle size and much more density, an orthorhombic single sintered pellets show a higher phase, and moreover, the pellets have finer grain boundaries and well developed twins. As a result these samples exhibit current densities (about 1500 A/cm') higher than those prepared by solid state method. Using BaO, instead of BaCO, as the starting material, a more dense bulk YBCO ceramics with orthorhombic single phase and Jc (about 1,000 A/cm') can have also been fabricated by solid state mathod.
INDRODUCTION Since the discovery of high Tc superconductors Y-Ba-Cu-O System, much efforts have been done in the research to improve the critical current density of the materials. M.F.Yan... discussed the technical factors influenced Jc; the others"'"' provided various kinds of processing approaches to get the crystal grains closely packed and highly oriented. Although the processing techniques are essential for raising Jc, the characteristics of YBaCu,O. (YBCO) powders should play an important role in affecting microstructure and Jc of the polycrystalline ceramics. In this paperwe have described the characteristics of four kinds of YBCO powders prepared by different processings and starting materials. We have identified the relation among the characteristics of YBCO powders and the microstructure; current density of the bulk materials. Mat. Res. Soc. Symp. Proc. Vol. 169. ©1990 Materials Research Society
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Table 1. Preparing methods and characteristics of YBCO powders Suapl
Paeparia9 Holethod
Starting Mtaterials
Yo
Solid state Reaction
Y203 , Crut, BaO.Z
0.32
Y1
Solid stale Reaction
Y2 03 , CuO, BaC,0
0.44 1
Y2,0 3 , Cu(N0 3 )2 ,
0.36
CYo
Improved Chtaeical Coprecipitation
CY1
Specific Particle Surface Sige( P) Area(m /U) 2-4
The Percentage of Particles Containisig twins (91) 2096
agglomerated
I particles 2-3
51,96
B0O2, IfIC2.0+
Chemical
Y2.0 3 , Cu3O3),
Coprecipitation-
Ba NO0 4 3 )z, ttCO.
I
04
I/
_zc
RESULTS AND DISCUSSIONS Characteristics
of the YBCO powders
In this work, four kinds of YBCO powders were prepared by solid state reaction techniques and chemical coprecipitation m
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