Superconducting Properties of Sol-Gel Derived Bi(Pb)-Sr-Ca-Cu-O System
The Bi₂₋ᵪPbᵪSr₂Ca₂Cu₃Oᵧ (2223) superconductor, has been prepared by sol-gel technique, using metal acetate precursors. Room temperature hydrolysis followed by polycondensation and heating yielded a transparent blue gel. The key to successful gel formation was due to a firm control of the pH of t...
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| 格式: | Thesis |
| 语言: | English English |
| 出版: |
1998
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| 主题: | |
| 在线阅读: | http://psasir.upm.edu.my/id/eprint/9427/1/FSAS_1998_18_A.pdf |
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| 总结: | The Bi₂₋ᵪPbᵪSr₂Ca₂Cu₃Oᵧ (2223) superconductor, has been
prepared by sol-gel technique, using metal acetate precursors. Room
temperature hydrolysis followed by polycondensation and heating
yielded a transparent blue gel. The key to successful gel formation
was due to a firm control of the pH of the solution. It was required to
maintain the pH at 5.5 throughout the sol to gelation process. The
decomposition of the polyhydroxyl metal complex to amorphous gel
was found to be completed at temperatures in the range of 200 to
250'C producing submicron size particles. The amorphous gel
transformed into crystalline powder at 600' C to 700' C.
The effect of heat treatment as a function of sintering time and
temperature have been also studied on Bi₂₋ᵪPbᵪSr₂Ca₂Cu₃Oᵧ
system. The 2223 phase was observed in samples sintered at 8450 C
for 48 h.
The effect of the Pb doping at the bismuth lattice site have been
studied in the Bi₂₋ᵪPbᵪSr₂Ca₂Cu₃Oᵧ ( x= 0.0, 0.4, 0.5 ) samples. Two
samples doped with 20 and 25 mole % of Pb in the bismuth site
yielded single phase sample with T, (R=O) above 102 K. Undoped
sample had mixed phases (2212 and 2223). The study shows that
the doped-sample with 25 mole % of Pb is the most suitable ratio
that gives rise to the best superconducting properties.
New procedure adopted in this work succeeded in getting good
quality gel from carbonates, oxides and nitrates as the starting
materials. The study shows that high-purity single-phase
superconductor with T, (R=O) at 104 K was obtained from carbonate
and oxide as starting materials. This value is comparable to that
obtained from corresponding metal acetates. |
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