Current-voltage hysteresis in GdBa2Cu3O7-delta ceramics in air at room temperature

We report here on the appearance of a hysteresis in the current-voltage characteristic, when a voltage is applied to a GdBa2Cu3O7-delta rod at room temperature. This hysteresis was caused by the appearance and disappearance of a hot spot. When a gradually increasing dc voltage (0-8 V) was applied to a GdBa2Cu3O7-delta rod, a hot spot appeared at a given voltage, V-a. Further increasing of the voltage increased the spot size, while the current stayed constant. When a voltage of 8 V was reached, the voltage was gradually decreased. The spot did not disappear at V-a, but at a voltage 0.2 to 1.3 V lower than V-a. The current remained constant until the spot disappeared. By the authors' best knowledge, this is the first report of a hysteresis in the current-voltage characteristic at room temperature for a high T-c superconductor.