The effect of Pb on the behavior of structure modulation in Bi2-xPbxSr3Fe2Oy isostructural with Bi2Sr2CaCu2O8

The complex investigation of the behavior of the structure modulation has b een carried out on single crystals of the Bi2-xPbxSr3FexOy compound (isostr uctural with 2212Cu) depending on the Pb content (x = 0.12, 0.15, 0.20, 0.2 5) by X-ray diffraction methods, Mossbauer spectroscopy, and electron micro scopy. It has been shown that the modulated structure exists in all the stu died specimens with x < 0.25. Beginning from the Pb concentration x = 0.12 the modulated structure is no longer continuous over the specimen as in the free-Pb compound and becomes 'island' one combining the regions with modul ation and without it. At x = 0.25 the modulation disappears practically, ho wever, the structure is distorted because of, probably, a high Pb concentra tion. (C) 1998 Published by Elsevier Science B.V. All rights reserved.