Properties of Bi2Sr2CaCu2O8 thick films melt-processed at temperatures up to 950 °C

Abstract

Thick Bi2Sr2CaCu2O8 films have been produced by melting Bi2Sr2CaCu2O8 powder on MgO substrates at temperatures just above the melting temperature of the powder. X-ray diffraction measurements indicate enhanced c-axis alignment throughout the thickness of the films. Films melted at 900 °C show greater alignment and contain less Bi2Sr2CuO6 compared to those processed at 950 °C. Both the degree of alignment and the Bi2Sr2CuO6 content increase as the cooling rate is decreased. Transport measurements show that films quickly cooled from low melt-processing temperatures have the highest critical current densities (Jc = 13 kA/cm2 at 30 K). The temperature dependence of Jc is best described by a flux creep model. Finally, Jc at 4.2 K (in both parallel and perpendicular magnetic fields) undergoes a sudden drop at low fields, but levels off above 0.5 T to about 30% of the zero field value.