Effect of long aging on the resistivity properties of optimally doped YBa2Cu3O7−δ single crystals

• Long time exposure in air leads to the degradation of the conducting properties.
• There is emergence of effective scattering centers of the carriers.
• In the aging process there are signs of phase separation.

We investigate the conducting properties in the basal ab-plane before and after a long time exposure in air atmosphere of the optimally oxygen doped YBa2Cu3O7−δ single crystals. Prolonged exposure leads to an increase of the effective scattering centers of the normal carriers. The excess conductivity in a wide temperature range has exponential temperature dependence and near the critical temperature is well described within the Aslamazov–Larkin theoretical model. The prolonged exposure increases to a great extent the temperature range of the implementation of the pseudogap state, narrowing the linear section of the temperature dependence of the resistivity in the ab-plane, ρab(Т).