Thick films of YBaCuO from precalcined powders--

Preparation and some of the chemical and microstructural aspects of thick films of the YBa2Cu3O7-x superconductors (herein designated as YBaCuO) using precalcined YBaCuO powders and a colloidal method are described. Films on alumina substrates were made from calcined YBaCuO powders dispersed in hexane using a commercial dispersant which acts as a steric stabilizer and binder. The additive decomposes without residues at relatively low temperatures, and structurally stable and uniform films are obtained for proper dosage of the dispersant. Scanning electron microscopy has been used to examine the microstructure, quality and sinterability of the films. An example of the use of other additives to improve sintering and adhesion of the film to the substrate is also described. Substrate/film interaction has been studied by compositional mapping using an electron probe microanalyzer. The results show a substantial reaction layer (1-2 μm) of barium aluminate and a significant diffusion distance (of several microns) of aluminum into the film