Rare earth substituted thallium-based superconductors

Abstract

The present invention comprises novel superconducting materials exhibiting superconductivity at temperatures exceeding 90 K. with chemical formula Tl.sub.a Pb.sub.b Ca.sub.c Sr.sub.d R.sub.e Cu.sub.f O.sub.g where R=Y or the lanthanide rare earth elements and where 0.3.ltoreq.a,b.ltoreq.0.7, 0.05.ltoreq.c.ltoreq.1.1,2-c.ltoreq.d.ltoreq.1.95, 0.05.ltoreq.e.ltoreq.1, 1.9.ltoreq.f.ltoreq.2.1 and 6.5.ltoreq.g.ltoreq.7.5. These compounds, which are layered perovskite-like oxides, exhibit a high chemical stability, form readily into nearly single phase, do not require adjustment of oxygen stoichiometry after synthesis and compositions may be chosen allowing superconductivity at temperatures exceeding 100 K. A preferred form of the superconducting materials is the range of compositions given by the chemical formula Tl.sub.0.5+x Pb.sub.0.5-x Ca.sub.1-y Sr.sub.2-z R.sub.y+z Cu.sub.2 O.sub.7.+-..delta. where 0.ltoreq.x, 8.ltoreq.0.3, 0.ltoreq.y.ltoreq.0.95, 0.05.ltoreq.z.ltoreq.1-y of which a preferred form is Tl.sub.0.5+x Pb.sub.0.5-x Ca.sub.0.8+x+z Sr.sub.2-z R.sub.0.2-x Cu.sub.2 O.sub.7.+-..delta. exemplified by Tl.sub.0.5 Pb.sub.0.5 CaSr.sub.1.8 La.sub.0-2 Cu.sub.2 O.sub.7.+-..delta. where 0.ltoreq..delta..ltoreq.0.1.

Dependencies are inferred from the claim text.