Influence of Sintering Temperature and Time on Superconductivity of Bi-Sr-Ca-Cu-O System

In order to get a single high-Tc phase in the simple Bi-Sr-Ca-Cu-O system without any other element, two kinds of powders: one named A obtained by pulverizing of the mixed powder aggregate fired at 850°C for 24h and the other named B obtained by oxalate coprecipitation method, were used in this experiment, and the effect of sintering time and temperature on the superconductivity have been studied.Whereas most of the specimens sintered at 860-880°C for 24h or 288h showed a two step resistivity transition (at about 110K and at about 80K), one specimen using A powder sintered at 877°C for 288h showed a sharp single resistivity transition at about 110K and zero resistance at about 100K. X-ray diffraction pattern, however, showed that the low-Tc phase still remained even in this case.