Abstract
X-ray powder diffraction and resistivity measurements were performed on Bi 2Sr 2CaCu 2O 8+ δ 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 β1)0 0 0. 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 ≈ 0.4 for Bi 2Sr 2Ca 1− x Y x Cu 2O 8+ δ and at x ′ ≈ 0.36 for Bi 2Sr 2Ca 1− x Y x Cu 1.94Zn 0.06O 8+ δ , 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.
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