Rebco (re = Y, Sm) High-temperature Superconducting Thin Film Growth

Owing to its excellent electrical property, YBa2Cu3O7-δ(YBCO) thin films have been applieded in the microwave devices.It makes the devices with higher quality factor and lower insertion loss; to obtain high critical current for coated conductor applications,one way is to fabricate YBCO thick films, thus,YBCO films have been studied intensively. The SmBa2Cu3O7-δ(SBCO) compound, obtained by substituting the rare earth Sm to Y in the well-known YBCO, is potentially attractive, because the Sm-system superconductors reveal not only a higher transition temperature (Tc) than YBCO but also have higher critical current density (Jc) in high magnetic fields. Aiming the growth mechanism of REBCO(RE=Y,Sm), the dissertation had touched the following aspects: The preparation of YBCO, SmBCO and HoBCO ceramic targets were studied. Based on a series of experiments,YBCO, SmBCO and HoBCO ceramic targets with high density and homogeneous roar grains were prepared. These targets were used to prepare superconducting films, which had excellent electrical properties. On the film growth mechanism, the film morphologies and epitaxial orient evolutions had been discussed with respect to deposition temperature, substrate and film thickness. The results show that all the grains are c-axis oriented and no a-axis grains have been detected on LAO and STO substrates at initial stage. It shows improved in-plane orientation of the YBCO films on annealed MgO substrate. The SmBCO thin films were deposited by pulsed laser deposition (PLD). The effect of deposition parameters such as substrate temperature, the oxygen pressure on the properties of the thin films were systematically studied. SmBCO thin films were grown expitaxially on MgO substrates and had critical current densities Jc 1.9 MA/cm2 at 77K. YBCO/SmBCO integrated thin films were also prepared following the optimized experimental conditions of SmBCO thin films.