Annex.

In this thesis, we had prepared two series of Bi-Based superconductors samples (La series and Sm series) by two different methods and studied the effect of doping on their modulation and physical properties. In the first series labeled La series (Bi2Sr2-xLaxCaCu2O8+ ) prepared by the conventional solid state reaction, the increase of La doping favors the purification of samples, reduces the cell parameters and increases the incommensurate modulation vector. The increase of oxygen concentration in case of x 0.3 of Lanthanum leads to a transformation of crystal system from the orthorhombic to tetragonal system.
For Sm series (Bi2-xSmxSr2CaCu2O8+ ), prepared by Pechini type solgel method it was revealed that the FTIR analysis showed that all the samples are free of organic elements after sintering step. The XRD analysis proved that Sm samples crystallized in the Bi-2212 phase with a little presence of the Bi-2201 and Bi-2223 phases in the Sm05 sample (x 0.05). The cell parameters decreased with the Sm doping. This later led to the transformation of the structure into a pseudo-tetragonal structure in the case of the Sm10 sample (x 0.10). The modulation was incommensurate and increased with Sm content. The crystallites size was nanometric. SEM analysis showed a well-connected plate-shaped grains. The electrical resistivity study showed that the transition to the superconductor state for all samples. The Bi-2223 phase appeared in Sm05 caused a double transition in the tail part of resistivity curve. The critical temperature Tc decreased with the Sm doping, whereas the activation energy U0 increased. The magneto-resistivity measurements showed that a 0.7 tesla applied magnetic field leads to a decrease of both Tc and U0.