Al doping influence on crystal growth, structure and superconducting properties of Y(Ca)Ba2Cu3O7−y whiskers

Abstract We synthesized Al doped Y(Ca)Ba 2 Cu 3 O 7− y (YBCO) whiskers via the solid state reaction method. Al doping was systematically varied in the nominal cationic stoichiometry of YBa 2 Cu 3 CaTe 0.5 Al x O 7− y , with 0 ⩽  x  ⩽ 0.5. The amount of the grown whiskers increases for nominal Al addition up to x  = 0.05, decreasing for larger concentrations. The concentration of Al incorporated in the crystals ( x ′) is always higher with respect to the starting stoichiometry and shows a gradient along its length, with a higher amount at the tip regions. The single crystal diffraction analyses show an increasing tetragonal character with increasing x ′, with a transition from the orthorhombic to the tetragonal system for x ′ = 0.13, which is in agreement with the worsening of electrical transport properties and disappearing of superconductivity for x ′ = 0.19.