Concepedia

Abstract

A superconducting transition with an onset temperature of about 40 K has been observed in the La-Cu-O system which is not doped with alkaline earth ions. The compounds with nominal compositions, La 2 CuO 4-δ , La 3 Cu 2 O y and La 4 Cu 3 O z were prepared. In this system, the occurrence of superconductivity is attributed to the orthorhombic (distorted K 2 NiF 4 type) phase. The superconducting transition occurs following a semiconductor-like increase in the resistivity with decreasing temperature, which is characteristic of the low carrier density superconductors. The effects of an annealing in oxygen at atmospheric pressure are also reported.