Synthesis, Mössbauer studies and superconductivity of substituted Bi 2201 phase

We report X-ray diffraction, resistivity and Mossbauer studies on several substituted 2201 Bi cuprates, Bi2Sr2Cu1−xFexOy(O≤x≤1) and Bi2Sr1.6La0.4Cu1−xFexOy and Bi1.6Pb0.4Sr1.6La0.4Cu1−xFexOy (O≤x≤0.04). The first series is not superconducting and a new phase appears for x=1. For La substituted samples, Tc increases up to 35K and decreases strongly with x. All Mossbauer spectra were fitted well with four quadrupole doublets, with relative population depending on samples.