A comparative study on in situ grown superconducting YBCO and YBCO-Ag thinfilms by PLD on polycrystalline SmBa2NbO6 substrate

The development and characterization of SmBa2NbO6, which is a new ceramic s ubstrate material for the YBa2Cu3O7-delta superconductor, are reported. SmB a2NbO6 has a complex cubic perovskite structure with lattice constant a = 8 .524 Angstrom. The dielectric properties of SmBa2NbO6 are in a range suitab le for its use as a substrate for microwave applications. SmBa2NbO6 was fou nd to have a thermal conductivity of 77 W m(-1) K-1 and a thermal expansion coefficient of 7.8 x 10(-6) degrees C-1 at room temperature. Superconducti ng YBa2Cu3O7-delta and YBa2Cu3O7-delta-Ag thin films have been grown irt si tu on polycrystalline SmBa2NbO6 by the pulsed laser ablation technique. The films exhibited (00l) orientation of an orthorhombic YBa2CU3O7-delta phase and gave a zero resistivity superconducting transition (Tc(0)) at 90 K wit h a transition width of similar to 1.5 K. The critical current density of Y BCO-Ag thin films grown on polycrystalline SmBa2NbO6 substrate was similar to 3 x 10(5) A cm(-2) at 77 K. A comparative study of YBCO and YBCO-Ag thin films developed on polycrystalline SmBa2NbO6 substrate by PLD based on the crystallinity, orientation and critical current density of the YBCO him is discussed in detail.