Superconductivity and transport critical current density of Nd substituted Tl-1212 phase Tl(Sr1-xNdx)2CaCu2O7

Nd substituted Tl-1212 type phase high-temperature superconductors with nominal starting composition Tl(Sr1-xNdx)(2)CaCu2O7 (x = 0-1.0) have been prepared and characterized. The x-ray diffraction patterns indicate that Nd substitution for x = 0.1-0.5 showed a dominant 1212 phase and a 1201 minor phase. This system showed a metallic normal state behaviour for x less than or equal to 0.4 and semiconducting-like behaviour for x greater than or equal to 0.5. Scanning electron micrographs indicate a similar grain size for the x = 0.1, 0.2 and 0.3 samples which is approximately 2-4 mu m. The transport critical current density, J(c), for the superconducting samples (x = 0.1, 0.2 and 0.3) at various temperatures together with a self-field approximation model indicates that the characteristic length (L-c) associated with the pinning force becomes lower with Nd substitution.