Superconductivity in Mn-doped Ca-Y-B-Cu-oxide ceramics

Abstract

The Mn - doped YO.3BaO.5 _xMnxCaO . ZCu03_z superconducting ceramics for ° < x s 0.15 were prepared under different heat treatments and sintering conditions. Electrical resistance and X-ray diffraction measurements from ambient temperature to 77K show that samples are either nonsuperconducting (for x > 0.07) or multiphase systems. The high temperature superconducting phase onse t 0 shows Tc 85 K. The resistance does not approach to zero value up to 77oK. Resul t s indicate that likely occupancy s i te s f or Mn are Ba and/ or Ca-sites rather than Cu(l) or Cu(Z) sites. Somewhat gross "structural modifications" in the neighbourhood of Mn-sites is responsible for depression of Tc and the appearance of low Tc phase (below 77K) . The effect of incr eased Mn content i s adverse on the superconducting properties of the samples. ESR studies of Mn - doped samples in dil. HCl are also reported.