Effect of Bi doping on the modulated composite structure of (Sr2Cu2O3)0.70CuO2, “Sr14Cu24O41”

The effect of Bi doping on the modulated composite structure of (Sr2Cu2O3)0.70CuO2 has been investigated on the basis of (3+1)-dimensional superspace group approach. By applying the bond-valence-sum method for the modulated composite structure, it has become apparent that the valence state of the Cu atom in any sites of the Cu2O3 ladder in (Sr2-xBixCu2O3)0.70CuO2 is maintained divalent. The interatomic distance between the Cu atom in the two-legged Cu2O3 ladder and the O atom in the CuO2 chain becomes larger with Bi doping, in spite of the slight shrinkage of lattice dimension along the stacking direction. The hole transfer from the CuO2 chain to the Cu2O3 ladder in (Sr2Cu2O3)0.70CuO2 is depressed by the effect of Bi doping on the atomic modulations. 15 refs.