The cation stoichiometric Bi2Sr2CuOδ was successfully obtained by solid state reaction under ambient oxygen pressures (Po2=0.2, 1atm). The modulation period as estimated by means of X-ray powder diffraction was λ ?? 4.7b for Bi2Sr2CuOδ synthesized under Po2=1atm, which is shorter than that for Bi2.125Sr1.875CuOz(λ ?? 15b). The Bi2Sr2CuOδ synthesized under Po2=1 atm showed metallic conductivity down to 2K, whereas it done under Po2=0.2 atm showed superconductivity with Tc ?? 8K. By annealing in Ar, Tc was raised up to 16K. At the same time, it was newly found that the modulation is disproportionate into two types with A, λ ?? 4.7b and λ ?? 5.5b.
