Microstructure and properties of Bi-Sr-Ca-Cu-O with additions of nanometer-scale alumina

Al2O3 particles approximate to 30 nm in size were added to Bi2Sr2CaCu2Ox in a 1:4 molar ratio, For comparison, 0.3- and approximate to 3-mu m Al2O3 pa rticles were added to separate batches. All of the materials were partial-m elt processed. The Al2O3 reacted during melting to form stable compounds, p rimarily of approximate composition (Sr,Ca)(2)AlO4. All additions caused sl ight decreases in the Te and melting point of the Bi2Sr2CaCu2Ox. The submic rometer Al2O3 additions induced large expansions in magnetic-hysteresis wid th at 6 K. Electron microscopy examination strongly suggested that the hyst eresis expansion was related to alloying of the Bi2Sr2CaCu2Ox matrix rather than to pinning by volume defects.