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Journal of the Korean Chemical Society (JKCS)

ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 33, Number 3
JKCSEZ 33(3)
June 20, 1989 

High Tc Superconductor Fiber YBa2Cu3O7-δ Synthesized by the Sol-gel Process

Sol-gel 법에 의한 고온 초전도체 YBa2Cu3O7-δ 선재 합성에 관한 연구
Jin Ho Choy, Jong Seok Yoo, Bae Whan Kim, Seung Tae Hong

최진호, 유종석, 김배환, 홍승태
Sol-gel법으로 고온 초전도체인 YBa2Cu3O7-δ의 세선을 제작하였다. Y, Ba, Cu 질산염을 1:2:3의 몰비로 수용액을 제조한 후 구연산 수용액을 첨가하고, 암모니아 수용액을 첨가하여 pH를 5.8∼6.2로 조절함으로써 균일한 colloid sol을 제조할 수 있었다. 이를 358K 로 가열하면 점차 점도가 증가하면서 gel화 반응이 진행되고 이 gel화 반응이 완결되기 전에 구연산염 precursor gel fiber를 임의의 길이 및 두께로 뽑을 수 있었다. 이 precursor를 1223K, Po2=1atm. 하에서 8시간 열처리한 후 723K로 서냉하고 13시간 동안 annealing 하여 약 95K에서 전기저항이 급격히 감소(Tc, onset), 약 82K에서는 저항 0(Tc, offset)을 나타내었고 액체질소 비등점에서 Meissner-effect를 보임으로써 초전도체 임을 확인하였다.

Superconducting fiber of high Tc YBa2Cu3O7-δ was successfully prepared by the sol-gel method. The stoichiometric mixture of Y, Ba and Cu nitrates was dissolved in water, to which citric acid solution was added. Then ammonium hydroxide was added to the mixture in order to increase the pH to a value between 5.8 and 6.2. The mixture was heated carefully to form a homogeneous colloid sol at 358 K. The solution was viscous enough to draw a long gel fiber, which was then heated at 1223K for 8 hrs. under oxygen partial pressure of PO2 = 1 atm., cooled slowly and annealed at 723K for 13 hrs.. The reacted superconducting sample maintained a fiber form with some shrinkage of its volume. The superconducting transition temperatures (Tc, onset and Tc, offset) of YBa2Cu3O7-δ have been determined to be approximately 95K and 82K, respectively. The superconducting phase was also confirmed by Meissner effect at liquid nitrogen boiling temperature.

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