A study on the superconducting properties of YBa2Cu3-xNbxO7-y (x=0 to 1) thin films

Effect of Nb substitution at the copper site in YBa2Cu3O7-x(Y-123) was studied in thin film form. Stoichiometric targets of YBa2Cu3-xNbxO7-y (YBCNO) where X = 0 to 1 were used and thin films were made on SrTiO3 < 100 > substrate by using Pulsed Laser Deposition(PLD) method. XRD studies have shown that the films are strongly c-axis oriented in nature. For x > 0.1, YBa7NbO6 becomes detectable and its intensity increases with x. T-C was found to decrease from 89 K to 82 K and C-axis parameter found to increase with the increase in x. For x > 0.4 no superconductivity was observed. However, an increase in J(C) was observed upto x less than or equal to 0.05 in YBCNO films. The best J(C)S realized for x = 0.0, 0.025 and 0.05 are 1.4 x 10(6) A/cm(2) at 77 K, respectively. The improvement in J(C) for small concentrations of Mb substitution can be attributed to changes in microstructure with improved grain size and aligned grains.