High- SuperconductivityView this Special Issue
The Properties of Screen Printed (Bi,Pb)-Sr-Ca-Cu-O Thick Films Based On Decomposed Oxalate Powders
The significance of powder and paste characteristics was studied in order to improve the morphology and structure of superconducting (Bi,Pb)-Sr-Ca-Cu-O screen printed thick films. Powder with nominal composition of Bi1.75Pb0.4Sr1.9Ca2.1Cu3.2Oy was prepared via the oxalate route and decomposed at 430 to 795℃. The decomposed powders were characterized by X-ray diffraction, transmission electron microscopy and specific surface area measurements. These studies showed a variation of specific surface area from 16.5 to 0.9 m2/g and a variation of the average particle size from 100 nm to 800 nm in the studied temperature interval. The phase structure showed three distinct temperature areas; between 430 to 620, 620 to 715, and at 795℃.Thick-film pastes were made by the addition of an organic vehicle at 500, 620, 650 and 795℃ to decompose annealed oxalate synthesized powders and, for comparison, the vehicle was also added to sintered mixed-oxide/carbonate-based powder in weight ratios from 0.42 to 0.54:1. Films were screen printed on single crystal MgO (100) substrates and melt annealed at 890 to 895℃ for 3 min and subsequently, for prolonged diffusion, annealed at 852℃. After firing, the films were mainly composed of the (001) textured (Bi,Pb)2Sr2Ca2Cu3Oy phase. The reference films, made from mixed oxide/carbonate powder, resembled the films based on oxalate powders decomposed at 795℃. Films based on oxalate powders, decomposed at lower temperatures, were smoother and were able to carry noticeably higher currents than films based on powders decomposed at higher temperatures.
Copyright © 1993 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.