SINGLE-PHASE REGION OF THE 2212-BI-SR-CA-CU-O SUPERCONDUCTOR

The phase relationships and solid-solution region of the Bi2Sr2CaCu2O8 +delta (2212) superconductor were investigated at 850-degrees-C under air atmosphere in a cross-section of the system Bi-Sr-Ca-Cu-(O) define d by the formula Bi2+ySr3-y-xCaCu2O8+delta. The system was studied by means of XRD and EMA and an approximate position of the 2212 single-ph ase region is delimited by the values of y=0.1 and 0.8 less-than-or-eq ual-to x less-than-or-equal-to 1.3. The single-phase region determined may be divided into two subregions, Sr-rich in the range 0.8 less-tha n-or-equal-to x less-than-or-equal-to 1.0 and Ca-rich in the range 1.1 less-than-or-equal-to x less-than-or-equal-to 1.3, these differing in the number and character of intergrowths. The highest superconducting transition temperature (T(c)) was found for x=0.8.