Elsevier

Physica B+C

Volume 148, Issues 1–3, December 1987, Pages 432-435
Physica B+C

Structural investigation of superconductors with high transition temperature

https://doi.org/10.1016/0378-4363(87)90255-5Get rights and content

Abstract

Powder X-ray diffraction (14–1223 K) and electrical resistivity measurements have been made for YBa2Cu3Oy superconductors. At low temperatures no distinct structural transformation is observed. At high temperatures the transformation of the orthorhombic phase to the tetragonal phase is started at 850 K and completed at 970 K. Then, the relation between the superconductive critical temperature and the ratios b/a and c/a of the orthorhombic phase is obtained for samples prepared by cooling down from 773, 973 and 1173 K with varying cooling rates. Tonc and Toffc have maximum values of 94 and 93 K, respectively, at b/a=0.9805 and c/a=3.0007. Both of these Tc's decrease as b/a approaches 1.0 and as c/a increases above 3.0007.

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