SOL-GEL PROCESS FOR PREPARATION OF YBA2CU4O8 FROM ACIDIC ACETATES AMMONIA/ASCORBIC ACID SYSTEMS/

YBa2Cu4Ox sols were prepared by addition of ammonia to acidic acetate solutions of Y3+, Ba2+, and Cu2+. Ascorbic acid was added to part of t he sol. The resultant sols were gelled to a shard or a coating by evap oration at 60 degrees C. Addition of ethanol to the sols facilitated f ormation of gel coatings, fabricated by a dipping technique, on Ag or glass or substrates. At 100 degrees C, gels formed in the presence of ascorbic acid were perfectly amorphous, in contrast to crystalline ace tate gels. The quality of coatings prepared from ascorbate gels was su perior to that of acetate gel coatings. Copyright (C) 1997 Elsevier Sc ience Ltd.