INVESTIGATIONS OF (BI PB)-SR-CA-CU-O-BASED SUPERCONDUCTORS BY EDS ANALYSIS/

Superconducting ceramic materials with a nominal composition Bi1.75Pb0 .25Sr2Ca2.05Cu3.05Ox were synthesized. T-c (R = 0) was 60 K (extrapola ted), 105 K and 110 K for samples fired at 800 degrees C, 845 degrees C and 855 degrees C respectively. Fractured and polished surfaces were investigated by energy dispersive x-ray spectroscopy (Eos) using a st andardless ZAF method and a ZAF method with standards. The volume frac tion of the superconducting phase increased with increasing firing tem perature. The non-superconducting phases identified in samples fired a t 800 degrees G were Ca2CuO3, (Sr, Ca)Cu2O3, Ca2PbO4 and unreacted CuO . After higher firing temperatures only Ca2CuO3 and (Sr, Ca)Cu2O3 rema ined. The EDS results showed that the composition of the high-T-c phas e differed from the 'ideal' 2223 (Bi0.66Sr0.66Ca0.66CuOx) composition which was attributed to the formation of solid solutions between the l ow-T-c and the high-T-c phases.