What is it about?
The complex investigation of the behavior of the structure modulation has been carried out on single crystals of the Bi2yxPbxSr3Fe2Oy compound Žisostructural with 2212Cu. depending on the Pb content Žxs0.12, 0.15, 0.20, 0.25. by X-ray diffraction methods, Mo ̈ssbauer spectroscopy, and electron microscopy. It has been shown that the modulated structure exists in all the studied specimens with x-0.25. Beginning from the Pb concentration xs0.12 the modulated structure is no longer continuous over the specimen as in the free-Pb compound and becomes ‘island’ one combining the regions with modulation and without it. At xs0.25 the modulation disappears practically, however, the structure is distorted because of, probably, a high Pb concentration.
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Why is it important?
Bi-containing high-temperature superconductors (HTSC) and compounds of Bi-ferrates isomorphous with them are characterized by modulated structures. A great number of X-ray diffraction and elec- tron-microscopic investigations testifies on it. Present complex investigation of the behavior of the structure modulation has been carried out on single crystals of the 232Fe compound (isostructural with 2212Cu) in the dependence on the Pb content by X-ray diffraction methods, Mo ̈ssbauer spectroscopy, and electron microscopy. For electron microscopy space resolution and sensitivity to the structure modulation can be considerably higher at definite conditions than for X-ray diffraction analysis.
Perspectives
The averaged modulated structure of 232Fe coincides with the nonmodulated structure of Pb- doped specimens. It means that the X-ray diffraction patterns of the studied specimens without and with modulated are identical, if satellite reflections are not taken into account. The most intensity of satellite reflections in the modulated structures is 30% relative to the Bragg reflections. When the amount of the regions without modulation increases (with increasing the Pb concentration), the sensitivity of an X-ray diffraction method becomes not enough to observe satellite reflections.
Dr Bagautdin Bagautdinov
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This page is a summary of: The effect of Pb on the behavior of structure modulation in Bi2−xPbxSr3Fe2Oy isostructural with Bi2Sr2CaCu2O8, Physica C Superconductivity, December 1998, Elsevier,
DOI: 10.1016/s0921-4534(98)00569-3.
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