PREPARATION AND SUPERCONDUCTING PROPERTIES OF HIGH-QUALITY BI-2212 CERAMICS

High-quality Bi-2212 ceramic samples were obtained by a solid-state re action method. At the starting composition Bi2.12Sr1.90Ca1.02Cu1.96Oy, X-ray diffraction, optical micrographs and scanning electron microsco py investigations show that the level of impurity phases is less than 1% by volume. Synthesis at a few degrees below the melting point favou rs grain growth. A final annealing treatment at controlled temperature and oxygen pressure, followed by rapid quenching, yields sharp superc onducting transitions, as observed by measurement of the a.c. suscepti bility and Meissner effect, and specific heat experiments. The Meissne r fraction in 2 mT approaches 50%.