Preparing superconducting ceramic materials

• Main Authors: THOMSON, JR.; JOHN, RHODES; WARREN W, O'BRYAN, JR.; HENRY M
• Format: Patent
• Language: English
• Published: 09.04.1991
• Subjects: ARTIFICIAL STONE; BASIC ELECTRIC ELEMENTS; CABLES; CEMENTS; CERAMICS; CHEMISTRY; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDINGMATERIALS; COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSESC01D OR C01F; CONCRETE; CONDUCTORS; ELECTRICITY; INORGANIC CHEMISTRY; INSULATORS; LIME, MAGNESIA; METALLURGY; PERFORMING OPERATIONS; PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL; REFRACTORIES; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING ORDIELECTRIC PROPERTIES; SEPARATION; SLAG; TRANSPORTING; TREATMENT OF NATURAL STONE

This invention is concerned with the preparation of superconducting ceramic materials by a solid state reaction technique. The process is especially suited for production of powders comprising >/=95% of Ba2YCu3O7 for use in producing sintered ceramic bodies comprising > 99% Ba2YCu3O7. The process includes the steps of a) wet milling raw powders of starting ingredients, including oxides and/or carbonates of the respective ions, to form a milled slurry, b) separating particulate solids from the liquids of the slurry, said separating including continuously agitating the mixed slurry so as to avoid segregation of the milled ingredients and spray drying the milled slurry to produce spray dryed particles, c) calcining the separated particles in oxygen to form calcined powder, d) optionally remilling the calcined powder, e) forming the calcined powder into a suitable form body and f) sintering the formed body in oxygen; preferably said separating step including spray drying the agitated, milled slurry. The above process results in calcined material comprising >/=95% of a single phase material (Ba2YCu3O7) and a small amount e.g. 3%, of a single second phase material and leads to a sintered ceramic which is >/=99% single phase material. This process is highly advantageous over prior processes in which the liquid is removed from the milled slurry by evaporation, filtering, settling and decantation or the like, which leads to segregation of the components prior to the calcining step and, thus, to the production of calcined powders having several second phases in addition to the main, desired phase.