Classifications

• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/10—Inorganic compounds or compositions
  • C30B29/16—Oxides
  • C30B29/22—Complex oxides
  • C30B29/225—Complex oxides based on rare earth copper oxides, e.g. high T-superconductors
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/45—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides
  • C04B35/4504—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on copper oxide or solid solutions thereof with other oxides containing rare earth oxides
  • C04B35/4508—Type 1-2-3
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/653—Processes involving a melting step
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B9/00—Single-crystal growth from melt solutions using molten solvents
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N60/00—Superconducting devices
  • H10N60/01—Manufacture or treatment
  • H10N60/0268—Manufacture or treatment of devices comprising copper oxide

Definitions

• This invention relates to a method of preparing large multiple and single domain YBa 2 Cu 3 O ⁇ material (123 material) . More specifically, the invention relates to an improved seeding method for preparing large single domain as well as large multiple domain YBa 2 Cu 3 O ⁇ materials, each with improved levitation properties.
• an object of the present invention is to provide a method of making large single domain 123 material by the use of Nd seeding materials.
• Another object of the invention is to provide a method of making multiple domain material using Nd seeding materials.
• Yet another object of the invention is to provide a method of making large single domain crack free 123 material using Nd as a seeding material.
• FIG. 1 is a view of a multiple domain material using a cube shape seed material in direct contact with the bulk 123 material and;
• FIG. 2 is a view like Fig. 1 wherein the preferential growth cylinder is of a smaller diameter than the cube shape seed material;
• FIGURE 3 is an elevational view of a single domain material showing a generally cubic seed material and a preferential growth cylinder;
• FIG. 4 is a graphical representation of the relationship of levitation force and distance for materials made in accordance with the present invention.
• 123 material has superior critical current density J c and high T c properties if a mixture of 211 (Y 2 BaCu ⁇ 5 ) is precipitated throughout the 123 material.
• enhanced flux pinning in bulk 123 material has been obtained by providing precipitated 211 material distributed throughout the 123 material by heating the 123 components to a temperature just below 1200°C to form a mixture of 211 plus a liquid (211+L) and subsequent slow cooling of the product.
• This technique is often associated with formation of larger 211 precipi ⁇ tates having particle diameters in the order of 5-30 microns if a platinum crucible is not used, since at elevated temperatures the Pt crucible interacts with the materials to produce finer 211 precipitates on the order of 0.01 to l micron.
• the resultant 123 material has reduced flux pinning as well as other properties such as lower J c .
• the prior art method is called quench-melt growth (QMG) method and has been shown to be an effective way of making 123 superconductors with strong pinning strength.
• QMG quench-melt growth
• one of the characteristics of the conventional QMG method is that it relies upon the reaction of the molten liquid with a platinum crucible to generate fine 211 precipitates. If a platinum crucible is not used, large precipitates result in spite of quenching.
• the subsequent quenching processing which is the key part of QMG, can be difficult to control, making systematic studies difficult. In order to develop various microstructures consistently, using low processing temperature and avoiding the quenching procedure are highly desirable.
• An alternative method was used to obtain a icrostructure that is similar to that obtained with QMG and provided enhanced flux pinning from fine 211 precipitates.
• the sintered sample is generally located to the Y 2 0 3 plus liquid phase region (>1200°C) and then splat-quenched using copper plates.
• the resulting sample then consists of Y 2 0 3 particles and solidified liquid phase (a mixture of barium cuprates and amorphous phases) .
• the quenched sample is crushed into fine powder and pressed into the desired shape (the so- called Melt Powder Growth Method) .
• the pressed sample is then heated to the 211 plus liquid phase region and cooled slowly through the peritectic point.
• the liquid phase is produced prior to quenching by heating the
• SLMG solid-liquid-melt growth
• PMP "powder melt process”
• the PMP process always employs Y 2 BaCu0 5 , BaCu0 2 and CuO as the starting materials, while it is the Y 2 0 3 instead of Y 2 BaCu0 5 that is used with BaCu0 2 and CuO in SLMG method.
• SLMG processing a mixture of powders of Y 2 0 3 , BaCu0 2 , and CuO were used as a precursor which was ball-milled for 24 hours to achieve a homogenous mixture. The resulting powder was then pressed into pellets, heated to a temperature of 1030-1050 ⁇ C at a rate of 100 ⁇ C/hour, and then cooled slowly through the peritectic reaction temperature at a rate of l°C/hour.
• the amount of the 211 phase was controlled by changing the amount of Y 2 0 3 , BaCu0 2 and CuO in the starting mixture, but the preferred ratio of 123 to 211 is about 5:1.
• the 211 precipitates in the SLMG samples are mostly of the size of 5-15 ⁇ . It is unclear in the present which part of 211 in the final microstructure formsssssssss during processing and which part is a residual from the starting powders. Differential thermal analysis showed a sharp endotherm at 1010°C, indicating some 123 formed during heating. However, some of the 211 must have also formed during heating. If this sample was solely 123 prior to passing through the peritectic temperature (1010°C) one would expect to see the same textured microstructure (i.e. with coarser 211, etc.) as is produced by conventional melt texturing of pure 123.
• the 123/211 mixture sample shows nearly uniform dispersion of 211 precipitates on the order of 1 ⁇ m.
• This microstructure is similar to that obtained with the QMG method. It has been well established that the size and distribution of 211 is closely associated with the initial size and mixing of the Y 2 0 3 .
• the SLMG method can produce a microstructure similar to that obtained by the QMG process but without undesirable high temperature melting and quenching.
• Seeding material used in the present invention is a REBa 2 Cu 3 0 ⁇ material (RE 123).
• the seeding material preferably is one using either Sml23 or Ndl23 with Nd being preferred, notwithstanding the fact that it forms a solid solution unlike Sm and certain other rare earths.
• Ndl23 has a higher melting point than Sml23 by about 15°C which surprisingly, is critical to the success of the present invention. It is believed that certain combinations of Sm and Nd may be used in a satisfactory manner. However, the use of the solid solution Nd 1+ ⁇ Ba 2 .
• y is between 6 and 7, permits the use of a temperature gradient in the furnace of up to about 30°C/cm, which if parallel to the C axis of the domain material supports and enhances the directional solidification of the 123 material.
• Single crystals of the seed material may be produced and harvested by providing oxide or carbonate sources of the rare earth barium and copper in quantities for the RE Ba 2 Cu 3 0 x seed crystal.
• barium and copper is preferably present in excess of that required for the final crystals. The amount of excess barium and copper provided will determine, to a large extent, the final geometry and properties of the crystal.
• the oxides and/or carbonates are ground and calcined to form powders which are thereafter heated to a temperature in excess of about 1000°C and more particularly to a temperature of about 1100 ⁇ C to form a molten flux which is rich in both barium and copper.
• the molten flux is slowly cooled at a range of from about l°c/hr to about 10°C per hour until single crystals of the RE Ba 2 Cu 3 O x are formed along with flux material.
• the mixture of single crystals REBa 2 Cu 3 0 ⁇ and flux is quenched from about 1020°C to 970°C and then transferred onto a porous substrate which may be, for instance magnesium oxide or 211 material, which is by its nature porous, and is then again heated to a temperature above the melting point of the flux which is about 950°C but below the melting point of the crystals which in the case of Nd 1+ ⁇ Ba 2 .
• ⁇ Cu 3 0 is 1070 ⁇ C in the presence of a porous material which is unreactive with the seed crystal in order to wick away the flux leaving the crystals more readily available for recovery. Nd 1+ ⁇ Ba 2 .
• ⁇ Cu 3 0 y has been prepared as above by a procedure in which the powders were calcined for a time of not less than about 24 hrs at a temperature below 1000°C and thereafter heated to a temperature of about 1050°C less than 1070°C, the melting point of the Nd seed for not less than 24 hrs and subsequently heated to a temperature to about 1100°C for about hrs and then cooled at a rate in the range of between 1°C per hour to about 10°C per hour.
• the mixture of single crystals and flux were heated to a temperature in the range of from about 870°C to about 1050° in the presence of a porous material unreactive to the rare earth seed crystal in order to wick away the flux leaving the crystals available for easy separation and recovery.
• a porous material unreactive to the rare earth seed crystal in order to wick away the flux leaving the crystals available for easy separation and recovery.
• barium and copper are present in excess so that the mole ratio of Nd to Ba to Cu is in the range of from about 1:2:15 to about 1:6:3 and preferably about 1:3:10.
• the unreactive porous wicking material should have an open porosity with substantial connection between the pores as it obtained by using 211 material.
• the seed material formed can be either cubic or plate like in shape depending on the excess amount of flux used. Using two times the excess amount of flux will produce plate-like seed crystals, while using less flux to produce cubic shaped crystals.
• the invention includes providing a preferential growth material intermediate the seed crystal and the bulk 123 material which results in production of a crack-free single domain 123 material. Where a material with multiple domains is preferred, the method of the present invention provides such a material in addition to the single domain crack free material.
• the preferential growth material which may be 123 or mixtures of 123 and 211 and Pt0 2 and as used herein may be cylindrical or tubular in geometric configuration and should be of sufficient length so that single domain material is produced in the bulk 123 material.
• the seed crystal is simply laid on top of the preferential growth material and depending upon the size of the seed material, the length of the preferential growth material has to be selected to provide single domain material in the bulk 123 material.
• FIG. 1-3 representations of multiple domain material in Fig. l and single domain materials in Figs. 2 and 3 wherein the seed crystal dimensions exceed that of the preferential growth material in Fig. 2 and the seed material dimensions are less than the diameter of the preferential growth material in Fig. 3.
• each of these large domain materials are crack free with the a-b axes of the material parallel, increasing the ability to cleave the domains along the a-b planes producing materials of desired thickness and reducing the mechanical handling of the material previously required when the material needed to be cut with diamond tools.
• Fig. 1-3 representations of multiple domain material in Fig. l and single domain materials in Figs. 2 and 3 wherein the seed crystal dimensions exceed that of the preferential growth material in Fig. 2 and the seed material dimensions are less than the diameter of the preferential growth material in Fig. 3.
• each of these large domain materials are crack free with the a-b axes of the material parallel, increasing the ability to cleave the domains along the a-b planes
• the pedestal height is at least 10-20% of the longitudinal extent of the seed crystal.
• the longitudinal extend of the pedestal height is at least 50% as large as the difference between the pedestal cross sectional area and the longitudinal extent of the seed crystal. This is sufficient that growth of more than one domain ceases before the bulk 123 material crystallizes resulting in a single crack free domain with parallel a-b axes capable of being cleaved rather than cut and with the c-axis vertically oriented.
• FIG. 4 there is illustrated a graphical representation of the levitation force of single domain material which is crack free compared to multiple domain material which contains cracks. More specifically, Fig. 4 shows the difference in levitation force for crack- free single domain material (top curve) and material in which there are multiple domains with cracks (lower curve) . While there has been disclosed what is considered to be the preferred embodiment of the present invention, it is understood that various changes in the details may be made without departing from the spirit, or sacrificing any of the advantages of the present invention.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Ceramic Engineering (AREA)
• Inorganic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Metallurgy (AREA)
• Structural Engineering (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=23466014

Family Applications (1)

Country Status (3)

Families Citing this family (5)

Citations (1)

Family Cites Families (3)

• 1996
  • 1996-01-11 EP EP96903372A patent/EP0793850A4/de not_active Withdrawn
  • 1996-01-11 AU AU47480/96A patent/AU4748096A/en not_active Abandoned
  • 1996-01-11 WO PCT/US1996/000200 patent/WO1996021934A1/en not_active Application Discontinuation

Patent Citations (1)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events