The influence of lithium halides on the superconducting properties of YB2Cu3O7-x

The effects of addition to YBa2Cu3O7-x Of lithium halides (YBa2Cu3O7-x (LIF )(gamma) and YBa2Cu3O7-x (LiCl)(gamma)) on the structural, electric, magnet ic, and transport properties are analyzed. Both structural and superconduct ing properties depend weakly on the lithium content up to gamma=0.10. The c ritical temperature keeps on a value well above 91 K for a small amount of lithium halide (reaching 93.48 K for gamma=0.02 in YBa2Cu3O7-x (LiF)(gamma) and 91.30 K in YBa2Cu3O7-x (LiCl)(gamma)), but for higher concentration of Li it rapidly decreases (81.68 K for gamma=0.20). The same behavior is exh ibited in the lower intragranular critical field. The intragranular critica l current density depends on the magnetic field as a power law: j(c)proport ional to B-alpha, with a lithium-concentration-dependent a. The voltage-cur rent characteristics follow a law typical for granular superconductors, V p roportional to(I-I-c(B, T))(n(B,T)). The dependence of the intergranular cr itical current, I-c, and of the exponent, n, on temperature, magnetic field , and concentration is analyzed.