A remarkable Tc-enhancement effect in Na-doped Y1-xNaxBa2Cu2.7Zn0.3O7-δ

In this paper, the preparation, structure, oxygen content and superconductivity of Y1-xNaxBa2Cu2.7Zn0.3O7-delta samples were investigated by means of x-ray diffraction, iodine titration, resistance and magnetism measurements. In this system, a remarkable T-C-enhancement effect and an insulator to superconductor transition have been observed due to Na doping. The superconducting transition temperature T-C of the Y1-xNaxBa2Cu2.7Zn0.3O7-delta sample with x = 0.20 is enhanced to similar to 60 K. The results for x-ray diffraction, lattice parameters, superconductivity and oxygen content indicate that the maximum substitution level of Na for Y in this system is x = 0.20, and T, increases while oxygen content decreases with increasing Na content x.