At+t Corp.

At&t Bell Laboratories

Bell Telephone Laboratories

At&t Technologies, Inc.

Warren W Rhodes

Henry M O'Bryan, Jr

Man Fei Yan

David W Johnson, Jr

John Thomson, Jr

Debra Anne Fleming

Sungho Jin

Thomas H Tiefel

Mark T McCormack

Apurba Roy

Hung C Ling

Gideon S Grader

Materials of composition La.sub.v X.sub.w M.sub.y Mn.sub.z O.sub.x, with x selected from Mg, Sc, Al, Zn, Cd, In and the rare earths that have an ionic radius smaller than that of La, with M selected from Ca, Sr, Ba and Pb, and with v, w, y, z and x in the ranges 0.45-0.85, 0.01-0.20, 0.20-0.45, 0.7-1.3 and 2.5-3.5, respectively, can have substantially improved magnetoresistance (MR) ratios, as compared to the corresponding X-free comparison material. In particular, the novel materials in polycrystalline (or non-epitaxial thin film) form can have relatively large MR ratios. For instance, polycrystalline La.sub.0.60 Y.sub.0.07 Ca.sub.0.33 MnO.sub.x had a peak MR ratio in excess of 10,000% (in absolute value) in a field of 6 T.

Magnetoresistive oxide material and articles comprising the material

This invention is predicated upon applicants' discovery that conventional techniques for minimizing metal loss from sintered ceramic materials are not adequate in the fabrication of small ceramic components such as multilayer monolithic magnetic devices wherein a magnetic core is substantially surrounded by an insulating housing. Applicants have determined that this metal loss problem can be solved by providing the component with a housing layer having an appropriate concentration of metal. Specifically, if the insulating housing material around the magnetic core has, during the high temperature firing, the same partial pressure of metal as the magnetic core material, there is no net loss of metal from the core. In a preferred embodiment, loss of zinc from a MnZn ferrite core is compensated by providing a housing of NiZn ferrite or zinc aluminate with appropriate Zn concentrations. Similar considerations apply to other ceramic components.

Sintered ceramic components and method for making same

Multilayer magnetic components can be made with reduced cracking and magnetic degradation by forming layers having patterns of magnetic and insulating regions separated by regions that are removable during sintering. Advantageously, when the layers are stacked, layers of removable material are also disposed between magnetic regions and insulating regions so as to produce upon sintering a magnetic core within an insulating body wherein the core is substantially completely surrounded by a thin layer of free space.

Method for making multilayer magnetic components

A process for the preparation of superconducting ceramic materials by a solid state reaction technique. The process is especially suited for production of powders including .gtoreq.95% of Ba.sub.2 YCu.sub.3 O.sub.7 for use in producing sintered ceramic bodies including &gt;99% Ba.sub.2 YCu.sub.3 O.sub.7. The process includes the steps of (a) wet milling raw powders of starting ingredients, including oxides and/or carbonates or the respective ions, to form a milled slurry, (b) separating particulate solids from the liquids of the slurry, the 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 including .gtoreq.95% of a single phase material (Ba.sub.2 YCu.sub.3 O.sub.7) and a small amount e.g. 3%, of a single second phase material and leads to a sintered ceramic which is .gtoreq.99% single phase material.

Preparing superconducting ceramic materials

A predominantly perovskite phase Pb(Zn.sub.x Mg.sub.1-x Nb.sub.2).sub.1/3 O.sub.3 ceramic is prepared by first forming a columbite precursor having the formula Zn.sub.x Mg.sub.1-x Nb.sub.2 O.sub.6 and reacting this material with PbO at temperatures of from 800.degree. C. to at least 1000.degree. C. as x varies from 0.025 to 0.7.

Method of preparing a ceramic composition

A method of preparing lightly doped ceramic materials which forms a slurry of the ceramic material with additives in solution, precipitates the additives and spray dries the slurry with the additive precipitates is described.

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Raritan, NJ, United States of America

Warren W Rhodes