Influence of chemical doping on flux pinning of GdBa ₂ Cu ₃ O _{7− z} films

Epitaxial GdBCO films with Cobalt (Co) and BaZrO ₃ (BZO) doping were prepared on (00l) LaAlO ₃ substrate by a self-developed fluorine-free polymer-assisted metal-organic deposition (FF-PA-MOD) approach. The effect of different doping ways on structure and properties of GdBCO films was investigated. Our results show that in-field critical current density ( J _c ) values of doped films have been distinctly improved compared to the pure film. It is noted that Co-doped film has much larger in-field J _c values than BZO-doped film, especially at higher temperatures. Furthermore, Co-doped GdBCO film shows significantly enhanced surface smoothness and grain connectivity. It is suggested that obviously enhanced J _c – B properties of the film may be attributed to improved surface morphologies and effective flux pinning centres by dilute Co doping. This study may offer another simple and efficient way to obtain the GdBCO-based coated conductors with high current densities.