X-ray-induced photoconductivity in YBa2Cu3O6 between 70 and 300 K

The x-ray-induced photoconductivity in bulk ceramic samples of YBa2Cu3O6+x, with x approximate to 0, at temperatures between 70 and 300 K has been studied. In addition to a prompt current, which occurs at the beginning of the irradiation, the photocurrent exhibits a saturation growth stage up to values quite larger than the prompt. The amplitude of the saturating stage depends on dose and dose rate. The photocurrent level also increases with the irradiation temperature, but the fractional change in electric carriers decreases as the irradiation temperature increases. It has been found that after irradiation the samples show a persistent photoconductivity (PPC). The isothermal decay curves at the irradiation temperature of the PPC show that its thermal stability increases for an increase of either the irradiation dose or the irradiation temperature. Above 200 K the thermal stability decreases and the sample completely recovers after several hours at room temperature. The possible relation between this PPC and the well known PPC induced by laser illumination in thin films of this material is discussed.