Effects of Ca-doping on microstructure and Tc in Bi2201 system

In this article, a series of samples with the nominal composition of Bi2Sr2-xCaxCuO6 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) are prepared by sol-gel method. By means of XRD, TEM and four point probe measurements, the effects of Ca doping on phase composition and lattice constant of Bi2201 superconductor are studied. It is shown that Ca element occupy and influence the modulation period and Tc. It has been found that b and c axes shortens firstly and then keeps constant with increasing of Ca. The introduction of Ca results in a decrease of Sr content as well as increase of the modulation wavelength and Tc. When the doping level of Ca is up to 0.7, a fraction of impurity appears gradually, which leads to a decrease in Tc.