Undoped and fluorine-doped materials of GdBa2Cu3O7-XFx (with x = O, 0.05, 0.1 and 0.2) were prepared at high temperature (950° C) by solid state reaction followed by oxygen treatment. X-ray diffractograms of the undoped sample showed single orthorhombic phase. Resistivity measurements showed that Tc(0) decreases with fluorine concentration. Thermopower measurements indicated a peak just before the onset of the superconducting transition. The reasons for the decrease of Tc and the anomalous behaviour of thermopower have been explained.
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