Etudes de l’effet des substitutions et additions de metaux Alkalins sur les proprietes de ceramiques supraconductrices a base de Bismuth.

Abstract

The effect of doping the Bi(Pb)2212 ((Bi,Pb) 2Sr1.8CaCu2O8+d) phase by potassium (K) is investigated. Two kinds of K doped Bi(Pb)2212 samples are used and compared in this study: In the first one K is substituted on the Sr site; In the second one K is added. Using the solid state method reaction, samples of Bi1.5Pb0.5(Sr1.8-xKx)CaCu2O8+d and Bi1.5Pb0.5Sr1.8CaCu2O8+dKx (0 ≤ x≤ 0.05) have been prepared from powders of carbonates and primary oxides having purity over 99%. The samples have been characterized by X ray diffraction (XRD), scanning electron microscopy (SEM), measurements of resistivity versus temperature and magnetization. Results show how the rate of doping by potassium affects the structural, transport and magnetic properties of Bi(Pb)2212 phase. Substitution of K gives better texture for the used rates while this effect occurs only for lower rate with addition. The temperature of onset of superconductivity Tconset decreases more by addition of K than by substitution. The two methods improve the critical current density, which reaches a value double by addition comparing to the K free compound.