Precipitation of impurity phases and its effect on the intergrain conducting properties of Ag-doped Bi(Pb)-Sr-Ca-Cu-O

The precipitation of impurity phases and its effect on the intergrain conduction have been investigated for the sintered Bi(Pb)-Sr-Ca-Cu-O compound of 2223 phase by doping with a small amount of Ag (2.8 wt%) and cooling at different rates from the sintering temperature (as high as 835 degrees C or 840 degrees C). A different set of impurity phases appeared according to whether the compound was doped or undoped. The appearance of some phases was extremely sensitive to the cooling rate. Among them the semiconducting 2201 phase in doped samples was found to play a crucial role in characterizing the intergrain superconductivity. This behaviour is discussed with particular reference to an observed fact that the weak link in the doped samples is markedly deteriorated by quenching. (author)