At&t Bell Laboratories

Lucent Technologies Inc.

Bell Telephone Laboratories

At+t Corp.

American Telephone & Telegraph Co., At&t Bell Laboratories

American Telephone and Telegraph, Co.

At&t Laboratories, Limited

Thomas H Tiefel

Sungho Jin

Richard C Sherwood

John J Mottine, Jr

Robert Bruce Van Dover

Mark T McCormack

Henry Hon Law

John Thomson, Jr

William C Vesperman

David Wilfred Johnson

John Edwin Graebner

Li-Han Chen

Henry M O'Bryan, Jr

Warren W Rhodes

Te-Sung Wu

Shohei Nakahara

William R Lambert

Stephen G Seger, Jr

James J Royer

Robert C Moore

Robert L Opila, Jr

Some mechanical, electrical, and thermal properties of high T,superconductors such as (Ba, Y) cuprates can be substantially improved by the dispersal of an appropriate metal in the superconductive body. For instance, mixing Ag particles with superconductive powder of nominal composition Ba,YCu,O,and processing the mixture in the conventional manner can produce superconductive bodies having T,of about 93 K and substantially greater fracture strength and normal state electrical and thermal conductivity than otherwise identical bodies that do not contain Ag particles.

Method of making a superconductive oxide body

Many potential applications of CVD diamond film require the ability to remove a predetermined quantity of material from a surface of the film. We have discovered that such removal is advantageously accomplished by contacting the surface of the polycrystalline diamond film with a metal selected from Fe, Ni, Mn and Ti (preferably Fe and Mn, most preferably Mn), and maintaining the metal-contacted diamond film at a temperature in the range 600-1100&deg; C. (preferably 800-1000&deg; C.) without relative lateral motion between the film and the metal, for an effective time for removal of the quantity of material, exemplarily less than 100 hours. The metal can be in any appropriate form, e.g., a deposited layer, (including a patterned layer), a foil, or powder. We have also discovered that the local thermal conductivity of CVD diamond films typically increases with distance from the lower surface of an as-grown film. Thus, in applications such as heat spreading it will frequently be advantageous to remove some of the fine-grained, low thermal conductivity material adjacent to the lower surface of the as-grown CVD film. Such removal can be accomplished by means of the above-described technique.

Method comprising removal of material from a diamond film

Articles according to the invention comprise a superconductive cuprate (e.g., YBa.sub.2 Cu.sub.3 O.sub.7) body containing elongate grains measuring at least about 10 .mu.m along the long axis and having an aspect ratio of at least 10:1. Bodies according to the invention can have relatively high critical current density, as compared to analogous non-textured bodies.

Article comprising textured superconductive cuprate material

New solder compositions having enhanced mechanical properties are disclosed. Relatively inert particles having a diameter of 2000 nm or less are dispersed in a solder material having an average grain size of 500 nm or less to produce such solder compositions. The dispersed particles act as physical barriers substantially impeding the motion of grain boundaries and inhibiting grain growth during thermal and stress cycling which substantially inhibits coarsening. As a consequence, the solder composition exhibits an advantageous level of superplasticity that is substantially resistant to joint failure. Methods for forming articles using such solder compositions is also disclosed.

Article comprising fine-grained solder compositions with dispersoid

The present invention provides improved techniques for metallizing ceramic substrates. The method comprises providing a ceramic substrate and depositing a layer of reducible material on the ceramic substrate. The layer of reducible material includes a reducible ceramic such as copper oxide. The ceramic substrate having the layer of reducible material disposed thereon is heated and the reducible material is contacted with a reducing agent to create a conductive region. The conductive region is either a metallized region formed by reduction, or it is a conductive ceramic formed through surface reduction. The present invention further provides a metallized ceramic substrate. The metallized layer comprises ceramic regions having at least one constituent in common with the ceramic substrate. The ceramic substrate and the ceramic regions of the metallized layer are sintered to each other such that the metallized region is interspersed between the sintered ceramic regions. In this fashion, the metal is firmly held to the ceramic substrate due to the presence of the bonded ceramic within the metallized layer.

Metallization of ceramic through application of an adherent reducible

A novel non-mechanical optical fiber switch contains a magneto-optic element and a tubular magnet. The magneto-optic element is disposed within the field of the magnet but outside of the magnet bore. The beam of radiation from the switch input to the switch output passes through the axial bore of the magnet. The magnet contains magnetically anisotropic material, preferably a deformation-aged alloy having Fe, Cr and Co as major constituents. The switch is advantageously used in optical fiber communication systems.

Article comprising a non-mechanical optical fiber switch

The present invention provides a method for metallizing a ceramic surface comprising a ferrite through a surface reduction treatment. A ceramic surface comprising a ferrite is heated. At least a portion of the ferrite is contacted with a gaseous reducing agent to create a metallic region by removing oxygen from the ferrite. The surface is cooled and, optionally, post-treated to enhance adhesion of the metallic region. Typical gaseous reducing agents are hydrogen, forming gas, and ammonia while typical ferrites are nickel-zinc ferrites and manganese-zinc ferrites. To form patterned regions, portions of the substrate are masked or portions of the reduced layer are removed.

Metallization of ferrites through surface reduction

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

We have discovered that the addition of a relatively small amount of Sr and/or Ba to La-Ca-Mn-O can yield material of improved magnetoresistive properties at room temperature and in a small applied field, as compared to the analogous Sr and/or Ba-free material. An exemplary composition is La.sub.0.55 Ca.sub.0.25 Sr.sub.0.08 MnO.sub.x. Material according to the invention has a substantially larger value of .vertline.d.rho./dH.vertline. than the analogous comparison material at 25.degree. C. and H.ltoreq.0.05 Tesla. Preferred compositions also can exhibit a substantially linear dependence of resistivity on applied magnetic field under these conditions, as well as have a relatively large value of zero field resistivity. The novel materials can advantageously be used in applications that involve sensing of a magnetic field, or of changes in such a field.

Article comprising magnetoresistive oxide of La, Ca, Mn additionally

A magnetoresistive medium for sensing magnetic fields is formed by a metallic alloy that contains spinodally decomposed ferromagnetic particles having at least one thickness dimension equal to or less than approximately 0.01 .mu.m.

Spinodally decomposed magnetoresistive devices

In accordance with the invention, an image is formed by applying a local magnetic field to selected regions of a magnetic composite medium comprising columns of magnetic particles distributed in a matrix medium. The particles are 'hard' or 'semi-hard' magnetic materials in order to retain the latent image as residual magnetism, and the image is developed by exposure to magnetic fluid or powders. The image can be erased by exposure to an AC demagnetizing field or a DC sweep magnet. Preferred apparatus for making such images comprises a sheet of such composite material having a pair of major surfaces with columns of magnetic particles oriented between the surfaces. A local magnetic field, such as a magnetic pen, can be used to write a latent magnetic image on one of the major surfaces. The magnetic columns present the latent image for development at either major surface. In preferred apparatus, one major surface is adapted for magnetic image writing and the other major surface is positioned in sealed relationship with a chamber for exposing the image to magnetic development material. In this arrangement the columns provide a high resolution image on the second surface despite the thickness of the medium between the write and development surfaces.

Method for forming an image on a magnetic composite medium and apparatus

The disclosed method can produce high T.sub.c superconductor material e.g., YBa.sub.2 Cu.sub.3 O.sub.7) of substantially increased intra-grain critical current density (J'.sub.c), as compared to conventionally produced bulk material of analogous composition. Exemplarily, YBa.sub.2 Cu.sub.3 O.sub.7 pellets produced according to the invention had J'.sub.c of about 10.sup.5 A/cm.sup.2 at 77 K. in an applied magnetic field of 0.9 Telsa. The inventive method comprises providing a precursor material whose composition differs from that of the desired superconductor with respect to at least one of the metal constituents of the desired superconductor. It further comprises heating the precursor material above the decomposition temperature (T.sub.d) of the precursor material such that a multiphase material results. The multiphase material comprises, in addition to a majority first phase, a dispersed precipitate phase. The method further comprises cooling the multiphase material to a temperature below T.sub.d at a rate such that at least a major portion of the precipitate phase is retained. The first phase differs from the desired superconductor at most with regard to oxygen content, and the heat treatment of the multiphase material is carried out such that the desired superconductor results. Exemplarily, the desired superconductor is YBa.sub.2 Cu.sub.3 O.sub.7, the precursor material has average composition YBa.sub.2 Cu.sub.4 O.sub.z (z.about.8), the precipitate phase comprises one or more copper oxides, T.sub.d is about 860.degree. C., and the multiphase material is produced at 920.degree. C.

Method of making high T.sub.c superconductor material, and article

A method of making a ribbon-like or sheet-like superconducting composite body is disclosed. The method is well suited for making long lengths (e.g.,&gt;100m) of ribboon or large areas (e.g.,&gt;100cm.sup.2) of sheet-like composite. The method comprises forming a Bi-Sr-Ca-Cu-oxide-containing layer on a metal (exemplarily Ag) substrate, and mechanically deforming (typically by rolling) the thus formed composite such that the oxide is densified to more than 80% of the theoretical density. Subsequently the oxide layer is at least partially melted and allowed to re-solidify such that a large portion of the oxide crystals has c-axis alignment. After appropriate heat treatment in an O.sub.2 -containing atmosphere, thus produced superconductor ribbons or sheets can have high J.sub.c).gtoreq.10.sup.4, frequently &gt;10.sup.5 A/cm.sup.2) for temperatures less than about 20K and in magnetic fields less than about 5T.

Method of making a ribbon-like or sheet-like superconducting oxide

Articles comprising a quantity of superconductive oxide material can be fabricated by a process that comprises melting of part of an oxide precursor material, with resultant directional resolidification. Exemplary embodiments comprise zone melting and movement of the hot zone through the precursor material. The method can result in superconductive material having improved properties, e.g., higher critical current, as compared to prior art oxide superconductors.

Method of fabricating a superconductive body

Disclosed are normal metal-clad superconductive bodies (e.g., wires, ribbons) having a normal metal cladding that is porous during at least a part of the manufacture of the body. The porous cladding permits access of an ambient atmosphere to the superconductive material. Exemplarily, the superconductive material is an oxide such as a (Ba, Y) cuprate, the normal metal cladding comprises Ag particles (or Ag-coated particles), and the body is treated in an oxygen-containing atmosphere. Techniques for producing such a body are also disclosed.

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North Plainfield, NJ, United States of America

Thomas H Tiefel