Structural, electrical and magnetic properties of Y(1−)Ca Ba2Cu3−M O7– compounds, where M=Ni, Fe, Al, Cr

Abstract Polycrystalline samples of YBa 2 Cu 3− y M y O 7− δ and (Y 1− x Ca x )Ba 2 Cu 2.85 M 0.15 O 7− δ with M=Ni, Al, Fe or Cr ( x ⩽0.3; and y ⩽0.25) were prepared by solid-state reaction. Electrical resistivity, DC and AC magnetic susceptibility measurements showed that the T c values decrease for the samples with y =0, as the level of doping, x , increases from 0.0 to 0.25. As the Ca content increases, the T c increases. The co-substitution of Ca tends to counteract the effect induced by M atoms, by doping holes into CuO 2 planes, but it cannot recover the decrease of the critical temperature.