Ca doped YBCO on the Ba site

Abstract

The effect of partial, nominal replacement of Ba with Ca on the properties of the YBa2Cu3O6+gd superconductor varies with the concentration of Ca. For nominal concentrations in Ca up to 50% a two phase system is formed: the known superconducting phase Y1-yCayBa2Cu3O6+δ and a new, non superconducting phase of composition Y1.14Ca1.58Cu3.27O6.45. The x-ray diffraction pattern of this new phase matches the Bragg peaks, as well as the commensurate and incommensurate peaks of a partially indexed pattern of the phase Y2-xCa2+xCu5O10. For nominal Ca concentrations 40 and 50%, microprobe analysis shows that the superconducting phase becomes a mixture of Y1-yCayBa2Cu3O6+° and YBa1.8Ca0.2Cu3O6.5, where Ca enters the structure in the Ba site. The microraman spectra indicate a small substitution of Ba by Ca, while the new phase shows novel characteristics. © 1995 Plenum Publishing Corporation