Microstructural and transport properties in substituted Bi2Sr2CaCu2O8+δ-modulated compounds

X-ray powder diffraction and resistivity measurements were performed on Bi2Sr2CaCu2O8+delta ceramics substituted by Y and Zn for Ca and Cu sites, respectively. X-ray diffraction patterns show an incommensurate modulated structure along the b-axis. The structural refinements were carried out using the four-dimensional space group Bbmb(0 beta 1)000. From the X-ray peak profiles analysis, an anisotropic line-shape broadening was observed. The use of the "Williamson and Hall" method allows distinguishing the origin of broadening as mainly due to microstrains. A large transition from a metallic to semiconductor behaviour is observed on the resistivity curves at x approximate to 0.4 for Bi2Sr2Ca1-xYxCu2O8+delta and at x' approximate to 0.36 for Bi2Sr2Ca1-xYxCu1.94Zn0.06O8+delta, which can be also correlated to the defects. Oppositely to the metallic behaviour, which satisfies the Mathiessen's rule, the semiconducting one can be modelled by a variable range hopping process. (c) 2006 Elsevier Inc. All rights reserved.