The influence of doping with Ca and Mg in YBa₂Cu₃O_7-δ ceramic

¹ Université Mentouri. Laboratoire Couches Minces et Interfaces. Campus de Chaabet Erssas – 25017 Constantine, Algéria
² CNR-SPIN and Dipartimento di Fisica “E. R. Caianiello” Università di Salerno, I-84084 Fisciano (SA), Italy

^a e-mail: attaf.sonia@yahoo.fr

Abstract

We have investigated the effect of partial substitution of Ca for Y and/or Mg for Cu on structural, compositional and magnetic properties in γBa₂Cu₃O_7-δ polycrystalline compounds. All prepared samples were found to be single phase with small fraction of Ba-secondary phases. Substitution by more than 2% of magnesium causes an increase of spurious phases. Energy Dispersive Spectroscopy (EDS) revealed that the distribution of Ca in the sample is quite homogenous. DC susceptibility measurements show that superconducting transition temperature Tc is reduced much more by Ca than Mg. Hysteresis loops reveal that magnetic irreversibility is decreased by Ca and Mg content. The deduced critical current density Jc does not follow the same variation. Ca alone reduces Jc for x=0.1 and x=0.2. Together with Ca, Mg compensates the reduction of Jc and increasing its content near the solubility limit gives higher Jc than in the undoped sample.