The results of a study into the annealing behaviour of an oxygen-rich superconductor, YLa1.6Ba3.4Cu6O 14+or-y(-0.12<y<0.47), are reported. As with YBa 2Cu3O7-d, the oxygen level increases with decreasing quench temperature (Tq), and materials are superconducting only for anneals below 500 degrees C. However, an unusual behaviour of the unit cell symmetry has been observed by powder X-ray diffraction: orthorhombicity increases with increasing Tq, and the superconducting materials in this series are tetragonal.
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