From SrCuO2 to Sr8Cu8O20-y: Why are superconducting properties of infinite-layer compounds so poor?

A series of infinite-layer compounds NdxSr1-xCuO2 were synthesized by high- pressure technique under different pressure. temperature. and time conditio ns. Crystal structure, microstructure, and superconducting properties of th e samples obtained were systematically investigated as a function of the sy nthesis conditions. The stability of the IL phase was studied using anneali ng procedures in Ar- and O-2-flow. as well as under oxygen pressure up to 9 0 bar followed by thermogravimetric, energy-dispersive X-ray analysis, and X-ray diffraction measurements. On the basis of the results obtained we sug gest a decomposition mechanism for the infinite-layer phase, which is respo nsible for the degradation of T-c, as well as a routine to produce electron -doped infinite-layer compounds with a sharp diamagnetic signal of bulk sup erconductivity.