FR2749580A1 - MANUFACTURING PROCESS OF HIGH TEMPERATURE SUPRACONDUCTIVE SOLID MATERIALS - Google Patents

Abstract

Process characterized in that a starting powder of formula: SEu Mv CUw Ox with: SE = Y, Nd, Sm, La, Dy, Er or Gd or a mixture of two or more of the preceding elements, M = Ba, Sr or Ca or a mixture of two or more of the above, u = 0.8 to 2, v = 1 to 2, w = 3 to 4, and x = 1.5 u + v + (0.5 .. .1.5) w; a specific platiniferous compound of formula: SEk Ptl Mm CUn Ox with: k = 0 to 2, l = 1 to 2, m = 2 to 4, n = 1 to 2 and, x = 1.5 k + m + (n + 1) z, with (z = 0.5 ... 2), was mixed in a proportion of substance amount from 0.2 to 7 mol%, and from this is produced by grinding and compression as well as by heat treatment which includes a crucible-free melt texturing process of solid materials in the form of, for example, blocks, ribbon moldings. These can be used as a superconductor in energy, propulsion and transport technology.

Description

Description

  The invention relates to a method of manufacturing

  superconducting massive materials at high temperature, tex-

  fused iron which can find an application for example in the technique of energy, propulsion and transport in the form of blocks, moldings, ribbons

and similar.

  It is already known to manufacture foam materials

  high-temperature superconducting materials, by crystalli-

  peritectic phase: x-superconducting phase (solid material) <+ fusion + solid phase P. which takes place for YBa2Cu307-6 (YBCO) as phase a in air at 1020 C. The solid phase P which has not reacted Y2Ba1Cu105 (211)

  remains in the case of YBCO as an inclusion in the structure

  ture. The crystallization underlying this process, related to a temperature gradient, is referred to as "texturing

by merger ".

  Thus, in practice, a powdery solids starting material is usually compressed in the first place.

  molded. These are heated further in a step of fu-

  above the peritectic melting temperature. In-

  then, by means of a holding step, largely above this temperature, a homogenization of the melt is carried out. After that, we make a transition by a rapid lowering to a temperature slightly above

  the peritectic melting temperature in order to crystallize

  sation that occurs with cooling speeds

  reduced in the temperature ranges below the

  peritectic composition and which leads to a tex-

tured.

  In the case where the starting powder consists only of

  In high temperature superconducting material, a high amount of the melt escapes from the solid.

  molded when exceeding the peritectic temperature of a

  disadvantageous. To this is correlated a deterioration

  or certainly a loss of superconducting properties. In-

  the fusion product, which has escaped, can react

  with the crucible material which leads to a deterioration

  addition of superconducting properties.

  To avoid an escape of the fusion product

  of this type, it is already known to use a powder of

  on the other hand, which contains additives. For example, YBCO uses an addition of Y2Ba1Cu1O5 and Y203 which lowers the reaction temperature and leads to a certain reduction in inclusions [211] (G. Krabbes et al.

  Physica C 244 (1995) 145-152). There is a disadvantage

  while a non-homogeneous distribution of

  grains of inclusions and crack formation

  NEET. A certain improvement is obtained in which the homogenization step is carried out in a platinum crucible and at a temperature of 1200 ° C., in which the melt is then quenched at room temperature and then powdered. The starting powder thus produced is extremely sensitive to air and humidity and therefore requires additional cost of the process, high expenses for its manufacture. In addition,

  it is disadvantageous that the massive superconducting materials

  obtained from it still have a

  inhomogeneous tribution of inclusions [211]. These disadvantages are also not eliminated when Pt or

  Pt02 is added and the temperature is limited to 1100 C.

  With other non-species additives, such as TiO3Ba, CeO3Ba and SnO3Ba (Ch.J.J.J. et al., J. Mater Sci Lett, 11 (1992) 831; Ch. J. Kim, PJ Mc. Ginn Physica C. 222 (1994) 177, W. Gawalek et al Cryogenics 33 (1993) 65), the process costs are certainly lower, they can not, however, prevent inhomogeneous distribution of inclusions [211] and the formations crack. A cause is seen in this

  these additives react with the periodic fusion products

  tectics and lead to the formation of parallel phases that disturb the equilibrium. Because of this, the process of texturing by fusion is disturbed in a sensitive way and

  it is difficult to control and reproduce.

  The invention relates to a method of manufacturing

  superconducting massive materials at high temperature textu-

  by fusion, in a cost-friendly manner and in the material as precipitation of [211]

  that are formed are distributed in the most homo-

  possible, that they have a reduced grain size and that crack formation is avoided most

widely.

  This problem is solved by the fact that the invention consists of a starting powder of formula: SEuMvCUwOx with, SE = Y, Nd, Sm, La, Dy, Er or Gd or a mixture of two or more of the preceding elements, M = Ba, Sr or Ca or a mixture of two or more of the preceding elements, u = 0.8 to 2 v = 1 to 2 w = 3 to 4 x = 1.5 u + v + (0.5 ... 1.5) w a specific platiniferous compound of formula: SEkPtlMmCunOx with, k = 0 to 2 1 = 1 to 2 m = 2 to 4 n = 1 to 2 x = 1.5 k + m + (n + 1) z with (z = 0.5 ... 2) was mixed in a proportion of amount of substance ranging from 0.2 to 7 mol%, and that from this mixture is manufactured by grinding and compression as well as by heat treatment which includes a melting process without crucible, massive superconducting materials with

high temperature.

  According to a suitable development of the invention, YBa2Cu307_6 or Nd1 + yBa2 yCu307 8 can be used with y = 0 to 0.6 and 6 = 0 to 1 and can be added as specific platinum compound PtBa4Cu209 in an amount proportion of substance

2% molar.

  The specific platiniferous compound is preferably produced by a process of synthesis of the powder technique.

  The proposed method leads in a way that

  to superconducting materials at high temperature

  stable form, with fields of remanence in the state of

  lation, high and critical current densities as they

  are needed in the field of energy and transport.

  The addition according to the invention of a platinum compound to the starting powder prior to partial melting does not alter the peritectic crystallization underlying the melt texturing process. Process temperatures and process parameters - such as

  Heating rate, holding times and cooling rates can be maintained, whereby the process is advantageously insensitive to fluctuations in process parameters.

  The specific addition according to the invention causes an increase in viscosity and a lowering of the boundary surface tension in a manner similar to an addition foreign to the species. However, the adjustment of the balance of the fusion products is additionally advantageously supported and maintained. Reactions for the formation of parallel phases which deteriorate unwanted qualities do not occur, this leads to the fact that the process of fusion texturing and the formation of the superconducting phase takes place in a more stable manner. In a more reproducible manner, it is advantageous that the melting product outlet and thus the possibility of reaction with the crucible material remains reduced, so that no noticeable impurities and thus correlated degradation occur. superconducting properties in the melt textured material The precipitations of [211] that are formed are characterized by a very small grain size and a homogeneous distribution over the entire volume.

  sample. Crack formation is greatly reduced

  clouded or completely stopped by crystallization

balance.

  In what follows, the invention is explained more

  precisely on the basis of execution example.

Example 1

  To a starting powder obtained commercially from the superconducting compound at high temperature YBa 2 Cu 2 O 3, 2 mol% of a pulverulent characteristic compound was added.

  composition of PtBa4Cu209 and 24 mol% of Y203 pulp.

  vérulent. The above-mentioned characteristic compound was previously produced starting from Y 2 O 3, BaCO 3, CuO and Pt via a synthesis process of

powder adapted.

  The powder mixture obtained is subjected to a grinding process first and then compressed

  axially in cylindrical moldings 15 mm long with a diameter of 30 mm or parallelepiped shaped shaped bodies having the dimensions 27x27x10 mm. Then,

  molded bodies were heated with 300 k / h at 1150 C, now

  at this temperature for 20 minutes and then

  at 1120 C. Finally, texturing was carried out by

  melting in a temperature gradient of 20 K / cm by cooling

  drainage with 6 K / h. The structure of the supracon-

  High temperature conductor thus manufactured consists of large crystals of several cubic centimeters which possess

a different orientation.

  Precipitation [211] is very fine and

  parts in a homogeneous way. The loss on smelting is

  significant despite the temperatures used

  above the training temperature for the products of

peritectic fusion (δ 1020 C).

  After the final oxygen loading required

  At 370 C, the critical current density of the moldings 4 is greater than 10 2 A / cm at 77 K and 0 T is greater than 10 A / cm at 77 K and 0 T.

Example 2

  From the mixture of powders described in the example

  1, which is formed from the starting powder, the compound

  and Y203, was produced by compression into 15 mm long cylindrical molded solids having a diameter of mm, to which each of the molded solids, a seed of Sm-123

  was added before the pressing process. Solids

  pressed at 300 K / h in the same way as in Example 1

  were heated to 1050 C and textures with a speed of

  0lo coldness of 0.5 C / h. The loss on the merger is of this

  equally weak despite the reduced speed of

  coldness and the long process times associated with it. The structure of the molded solids thus produced consists of one or two crystals which have the direction

preferred seed of Sm-123.

  After a final oxygen loading at 370 ° C., for 72 hours in a circulating oxygen atmosphere,

  the superconducting molded solids at high temperature and

  if manufactured, have a field of remanence after freezing

  550 mT and a levitation force of 50 N at 77 K. The critical current density of the molded bodies is greater than 10 A / cm2 at 77 K and O T.

Example 3

  To a starting powder of the composition

  NdBa2Cu307_8, 2% molar of a compound characterized by

  powder composition PtBa4Cu209 and 40 mol% of powdered Nd2BaO4. The above-mentioned characteristic compound was produced beforehand starting from Y 2 O 3, CO 3 Ba, 3 (CuO and Pt) by a process of synthesis of the technique of

powders adapted.

  After running a grinding process, the grinding of powders was uniaxially compressed into

  cylindrical molding bodies 6 mm long with a diameter of

  be 14 mm. Then, the molding solids were textu-

  melted in a nitrogen / oxygen atmosphere with only 1% by volume of O 2. For this purpose, the molding solids were heated to 1100 C and cooled, starting from

  of 1040 C, in a temperature gradient of 2 K / cm

  cold with 1 K / h at room temperature. During merge texturing, there was no significant loss on the merger; The high temperature superconducting molding solids produced in this way have a structure of

  which is characterized by several crystals and has inclusions of homogeneously distributed ND-422, very small in a size of <5 gm. The critical current densities of the molded solids 4 rise after final oxygen loading at> 10 A / cm at 77 K and at O T.

Claims (3)

R E V E N D I C A T IONS   1) Method for manufacturing solid materials, fusion textures, superconductors at high temperature, in which a superconducting starting powder containing additives is used, characterized in that a starting powder of formula: SEUMvCUwOx with, SE = Y, Nd, Sm, La, Dy, Er or Gd or a mixture of two or more of the foregoing, M = Ba, Sr or Ca or a mixture of two or more of the foregoing, u = 0.8 to 2 v = 1 to 2 w = 3 to 4, and x = 1.5 u + v + (0.5 ... 1.5) w a specific platiniferous compound of formula: SEkPtlMmCunOx with, k = 0 to 2 1 = 1 to 2   m = 2 to 4 n = 1 to 2 and x = 1.5 k + m + (n + 1) z, with (z = 0, 5 ... 2) was mixed in an amount proportion of substance   from 0.2 to 7 mol%, and that from this   High temperature superconducting materials are produced by grinding and pressing as well as by heat treatment which includes a melt texturing process. devoid of crucible.   3 () 2) Process according to claim 1, characterized in that YBa2Cu307_6 or Nd1 + yBa2_yCu307 6 is used as YBa2Cu307_6 or Nd1 + yBa2_yCu307 6 with y = 0 to 0.6 and 6 = 0 to 1 and the compound containing specific platinum PtBa4Cu209 in a proportion of the amount of substance, 2% molar.   3) Process according to claim 1, characterized in that the compound containing specific platinum is produced by a process of synthesis of the powder technique.