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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 9, Number 5
May 20, 1988 

Determination of the Copper Valency and the Oxygen Deficiency in the High Tc Superconductor, YBa2Cu3O7-δ
Jin-Ho Choy*, Suk-Yong Choi, Song-Ho Byeon, Sung-Ho Chun, Seung-Tae Hong, Duk-Young Jung, Won-Young Choe, Yung-Woo Park
The ratio of trivalent to divalent copper has been determined by the redox titration for two superconducting phases of YBa2Cu3+2xCu2+3-2xO6.5+x with the onset temp. of 60K (x = 0.23 ± 0.01) and 90K (x = 0.35 ± 0.02), and for the insulating one (x ≒ 0) which was kept in an ambient atmosphere for 72 hrs. It is found that Tc, and the ratio of Cu3+/Cu2+ depend strongly on the annealing temperature and time. A typical orthorhombic phase can easily be obtained by a slow cooling or stepwise cooling at PO2 = 1 atm, and shows a high Tc (ca. 90K) superconductivity.
289 - 291
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