SYNTHESIS AND SUPERCONDUCTING PROPERTIES OF THE CA1-XNAXLABACU3OY SYSTEM

Studying the series Ca1-xNaxLaBaCu3Oy one finds that the tetragonal Na -doped CLBCO system exhibits superconducting properties when the oxyge n content is below 6.6. X-ray diffraction analysis shows that Na has a limited solubility in the parent compound. It is concluded that the s ubstitution of Na at (1/2, 1/2, 1/2) site reconstructs the long-range ordered Cu-O chains in the CuO planes. This introduces self-doping of holes on the CuO2 planes, resulting in superconductivity at low oxygen content. But when the oxygen content increases up to y = 6.85, the su perconductivity can be explained in terms of the nominal hole concentr ation. The Na doping also decreases the processing temperature of CLBC O.