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In this paper, a structural study on series crystals of (Bi2-xPbx)Sr2CuOy (0.1≤ x ≤ 0.6) by X-ray precession method is reported. We found that in the lead substitution regions 0.4≤x≤0.5 this system is formed by two interpenetrating subsystems. One subsystem has an incommensurate modulated structure with a pseudo-tetragonal lattice. The other one has a non-modulated orthorhombic structure. They share the same lattice parameters a and c; but the lattice parameter b has different values. We have investigated the extinction rules and satellite diffraction intensities for modulated phase as a function of the lead substitution, and determined the su-perspace group for the modulated phase in this system. Finally, we discussed the asymmetric distribution of the satellite intensities in this series of crystals.
In this paper, a structural study on series crystals of (Bi2-xPbx) Sr2CuOy (0.1≤x≤0.6) by X-ray precession method is reported. We found that in the lead substitution regions 0.4≤x≤0.5 this system is formed by two interpenetrating subsystems. One subsystem has an incommensurate modulated structure with a pseudo-tetragonal lattice. They share the same lattice parameters a and c; but the lattice parameter b has different values. We have investigated the extinction rules and satellite diffraction intensities for modulated phase as a function of the lead substitution, and determined the su-perspace group for the modulated phase in this system. Finally, we discussed the asymmetric distribution of the satellite intensities in this series of crystals.