Control of the oxygen doping in Bi-2212 whiskers by means of their synthesis process

摘要

Direct evidence of oxygen doping control in single phase Bi2Sr2CaCu208+δ (Bi-2212)whiskers is reported, along with the changes in their structural properties obtained by varyingthe growth temperature of the synthesis process in the range from 843 to 872 °C. The as-grownwhiskers were investigated by means of x-ray powder diffraction (XRPD), electrical transportmeasurements, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy(EDS). The XRPD measurements showed that the value of the c-axis lattice parameter increasesfrom 30.556 to 30.640 A when increasing the growth temperature, which indicates differentoxygen doping levels spanning from the slightly overdoped to the nearly optimally dopedregimes. Such results are also confirmed by the electrical characterizations, which revealed atypical relationship among resistivity (ρab), superconducting critical temperature (Tc),andc-axis value. The growth of CuO crystals has also been identified during this study, with amaximum yield in the range 860-864 °C, where also a slope change in the c-axis behavior hasbeen found, implying a possible correlation between the two phenomena. Therefore, bychanging the synthesis growth temperature, one can provide an effective way to tune thewhisker electrical transport properties.