Electrical Transport and Oxygen Disorder in YBCO

We investigated the origin of a non-linear temperature dependence of resistivity ρ_ab(T) in the a-b planes of YBCO, frequently observed in optimally doped twinned YBCO single crystals and thin films and in untwinned YBCO crystals along the chain direction. We performed the measurements of ρ_ab(T) in c-axis oriented YBCO thin films that were subjected to low temperature annealing at 120–140°C (400–420 K) in argon. Our results have shown that redistribution of oxygen at a fixed oxygen content in the chain layers of YBCO with a non-linear ρ_ab(T), leads to an increase of T_c, an increase of resistivity and a reduction of the non-linear component in ρ_ab(T).