YBA2CU3O7-X SUPERCONDUCTIVE TAPES AND WIRES - A PERITECTIC SINTERING PROCEDURE TO IMPROVE THE QUALITY

YBa2Cu3O7-x tapes were made by a powder-in-binder technique, using pol ysulphone (PSF) as the organic polymer and N-methyl-2-pyrrolidone (NMP ) as the solvent. The suspension is cast onto a glass substrate plate to form the tape (Doctor Blade method) and is consequently immersed in to a non-solvent to remove the solvent by phase inversion. In this pap er we describe the different steps in an improved ''peritectic'' therm al treatment that are necessary to make the green product into a super conductive tape. Three steps are important in this heat treatment. Fir st the polysulphone binder has to be removed as much as possible witho ut reacting with the YBa2Cu3O7-x material. Next the sample has to be s intered into a dense ceramic material. In order to improve the intergr anular connections, the sample is partially melted at relative low tem perature in vacuum. The sample is subsequently heated up in oxygen to the normal sinter temperature. At this high temperature the YBa2Cu3O7- x, phase will be restored by a peritectic reaction of the Y2BaCuO5 wit h a liquid phase. The final step is a two step anneal to ensure the fu ll oxidation of the superconductor.