The thermal treatement influence on the electrical resistance of underdoped YBa2(Cu0.96Fe0.04)(3)O-y superconductor

The underdoped YBa2(Cu0.96Fe0.04)(3)O-y superconducting system has been pre pared and investigated. The effect of oxygen content and the thermal treatm ent (fast quenching of underdoped samples from 250 K to 4.5 K) on the elect rical resistance were studied. The semiconductor behaviour of electrical re sistance after the fast quenching of the samples agree with a model for the stripe formation in Cu(2)O-2 plane. The presence of two resistive transiti ons (T-cl = 18 K and T-c2 = 36 K) were evidenced for y = 6.75 sample. The d isappearance of the low transition after the thermal treatment were analyse d in relation with the role of Fe clusters on the order of apical oxygen. T he decrease of T-c by increasing oxygen deficiency was attributed to the fr agmentation and stripe pinning in Cu(2)O-2 planes as a result of the disord er produced by the Fe clusters in Cu(1)O chains.