Influence of conditions of synthesis on superconductivity in Nd2-xCexCuO4-y

Samples of Nd1.85Ce0.15CuO4 were prepared using two different methods of synthesis (series A and B). The superconductivity was characterized by electrical resistivity and dc magnetic susceptibility measurements. X-ray diffraction (XRD) and energy dispersion X-ray analysis (EDAX) were used to characterize the structure composition and the sample quality. The resistivity measurements show a double transition to the superconducting state. It is proposed that the grains consist of a core with the optimum cerium content ( [similar to] 0.15) and a shell where the cerium content is different. The homogeneity of the samples was estimated through the determination of the slope of resistivity in the superconducting transition region (d?/dT). Ce content is higher and it is more homogeneously distributed in the samples treated at higher temperatures. EDAX analysis shows that the quantity of Cu on the surface of the samples increases with the temperature of the reduction process.