Synthesis and Superconducting Properties of the Ca1−xNaxLaBaCu3Oy System

Abstract

Studying the series Ca1‐xNaxLaBaCu3Oy one finds that the tetragonal Na‐doped CLBCO system exhibits superconducting properties when the oxygen 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 substitution 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 superconductivity can be explained in terms of the nominal hole concentration. The Na doping also decreases the processing temperature of CLBCO.