JP2931446B2 - Method for producing rare earth oxide superconductor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a high critical current density even under a high magnetic field in which at least one element component of Rh, Pt and Ru is uniformly dispersed. REBa ₂ Cu ₃ O _{y shown} (RE
Represents Y, Gd, Dy, Ho, Er or Yb. )
About the production how of the oxide superconductor. 2. Description of the Related Art Oxide superconductors have been actively studied for practical use because of their high critical temperature. As a method for obtaining these oxide superconductors as a bulk material, a sintering method has conventionally been generally used. The oxide superconductor manufactured by the sintering method has a fine crystal structure in which crystal grains are small and many grain boundaries exist inside. In such an oxide superconducting bulk material by the sintering method, the individual superconducting particles are connected by weak bonds, and the critical current density (Jc) is governed by this weak bond, and a high Jc is obtained. Absent. On the other hand, it is known that single crystal superconductors do not have the above-described problem of grain boundaries and exhibit high Jc even in a high magnetic field. Attempts to approximate the crystal structure were considered,
It has also been proposed to introduce a so-called pinning center for dispersing fine particles of the non-superconducting phase in the superconducting phase and fixing the invading magnetic flux lines. For example, the MTG method (Me
lt Textured Growth method) has been proposed. In the MTG method, the oxide superconductor is gradually cooled from the decomposition melting temperature of 123 phase (YBa ₂ Cu ₃ O _y , where Y is a rare earth element containing Y).
A peritectic reaction between the 11 phase (Y ₂ BaCuO ₅ ) and the liquid phase is caused to cause crystal growth, and 211 g
A phase exists and acts as a pinning center. Therefore, the obtained oxide superconductor shows a high Jc even in a magnetic field. However, the oxide superconductor obtained by this melting method,
There were inconveniences such as a large grain size of the 211 phase, a nonuniform distribution thereof, and cracks along the crystal growth direction. [0004] A method has also been proposed in which the particle size of the 211 phase is made small and uniform to prevent defects such as cracks in the bulk body. For example, Japanese Patent Application Laid-Open No. 2-153803 proposes a QMG method (Quench and Melt Growth method), and furthermore, a MPMG method (Melt Powder and Melt Growth method) for improving formability in the QMG method.
Has also been proposed. It is disclosed that these exhibit an extremely strong pinning effect and exhibit excellent Jc in a high magnetic field. [0005] However, Japanese Patent Laid-Open Publication No.
The QMG method proposed in US Pat.
Although it is possible to obtain a 123-phase crystal in which the phases are relatively uniformly dispersed, the Y ₂ O ₃ phase of 50 μm or less is uniformly dispersed in the BaCu oxide phase by melting and quenching and solidifying the oxide superconductor raw material. After obtaining the intermediate, or Y ₂ O ₃ and Ba
It is mixed with Cu oxide to form a plate-like or linear shaped body having a thickness of 5 mm or less, and is further heated to a semi-molten state at the decomposition melting temperature of the above-mentioned 123 phase, and is gradually cooled from that temperature at a predetermined cooling rate. Cooling is to grow the 123 phase in which 211 phases of 20 μm or less are finely and homogeneously dispersed by cooling, and it is formed into a specific shape, or is melted and quenched solidification-semi-molten-slow cooling and molten state Must be performed in two stages, and the operation becomes complicated. Furthermore, when passing through rapid solidification to prevent agglomeration of the Y ₂ BaCuO ₅ phase and to form a finely dispersed structure, a platinum crucible becomes indispensable, and the superconducting characteristics due to the reaction between platinum and the rare-earth oxide superconductor are reduced. There are also problems such as a possibility of deterioration or variation in characteristics, and a means for rapid quenching. Therefore, industrially, there is a demand for a method for producing an oxide superconductor in which a large crystal can be grown by a simple operation and a similar effect can be obtained. The present invention makes use of the simplicity of the operation of the melting method, and exhibits a pinning effect that is as strong as or higher than that of the oxide superconductor obtained by the QMG method or the MPMG method, and REBa ₂ Cu, in which fine 211 phase is dispersed very uniformly in 123 superconducting phase so as to show excellent Jc
₃ O _y (RE is Y, Gd, Dy, Ho, Er or Yb
Represents As a result of intensive studies on a method for obtaining an oxide superconductor, the present invention was completed. According to the present invention, REBa is provided.
₂ Cu ₃ O _y (RE represents Y, Gd, Dy, Ho, Er or Yb.) In addition to the RE, Ba and Cu components constituting the oxide superconductor, at least one of Rh, Pt and Ru molding using a raw material powder elements ingredient is to be 0.01 to 5 wt% containing organic on an elemental basis melt solidified to powdery
And, the molded body is not less than the decomposition melting temperature of the oxide superconductor
Heat treatment to temperature, slow cooling, heat treatment, REBa ₂ Cu ₃
Oxide with RE ₂ BaCuO ₅ phase finely dispersed in O _y phase
Rare earth oxide superconductor characterized by obtaining an electric conductor
The method of manufacturing is provided. The rare-earth oxide superconductor of the present invention is constituted as described above, and the REBa ₂ Cu ₃ O _y oxide superconductor has an R superconductor.
h, at least one element component of the Pt and Ru (hereinafter,
It is simply a component such as Pt. ) By is uniformly dispersed and contained as particles, RE ₂ Bac to exert pinning effect
The 211 phase of uO ₅ is finely and uniformly dispersed in the 123 phase of REBa ₂ Cu ₃ O _y , exhibiting superconductivity that is uniform and excellent as a whole, and has a high Jc as in the case of the QMG method and the MPMG method. In order to uniformly disperse particles such as Pt, REB
a ₂ Cu ₃ O _y RE ingredients for constituting the oxide superconductor, Ba
And at least one elemental component of Rh, Pt, and Ru in an amount of 0.01 to 5% by weight on an elemental basis.
By using as a raw material a powder obtained by dispersing and being melted and solidified into a powder, particles of the target component such as Pt can be uniformly dispersed. Hereinafter, the present invention will be described in more detail. REBa ₂ Cu ₃ O _y oxide superconductor of the present invention, RE
Is a rare earth-based oxide superconductor such as YBa ₂ Cu ₃ O ₇ having a multilayered perovskite structure containing a rare earth element of Y, Gd, Dy, Ho, Er or Yb. The rare earth oxide superconductor of the present invention is made of REBa ₂ C
RE, a raw material for forming u ₃ O _y oxide, that is, Y, G
An oxide mixed powder obtained by mixing an oxide of d, Dy, Ho, Er or Yb, a carbonate of Ba and an oxide of Cu, a calcined powder of the oxide mixed powder, a frit powder of the oxide mixed powder, etc. , after firing REBa ₂ Cu ₃ O _y and RE ₂ BaCu
A series of steps such as molding, melt decomposition, slow cooling, heat treatment, etc., using a uniformly dispersed and mixed powder obtained by adding a component such as Pt to a compound blended to constitute O ₅ and then melt-solidifying. Can be obtained through In this case, the particle diameters of the raw material powders of components such as RE, Ba and Cu components and Pt to be melt-solidified are not particularly limited.
Fine powder of 0 μm or less, particularly 1 to 5 μm, is preferred. 20μ
Raw material powders exceeding m are not preferred because the composition becomes non-uniform at the time of decomposition and melting. In the present invention, preferably, each component material is used as a powder, and particularly preferably,
It is preferable to use a powder obtained by melting and solidifying RE, Ba, and Cu components as raw materials for forming the above-mentioned REBa ₂ Cu ₃ O _y oxide and a predetermined amount of components such as Pt. In the present invention, the above-mentioned melt-solidification method for obtaining a preferable powder includes:
Usually, it can be performed in the following steps. That is, first, one or more elemental powders of components such as Pt and the like having substantially the same particle diameter as each of RE, Ba and Cu are added to a mixture obtained by mixing the respective components of the raw materials constituting the REBa ₂ Cu ₃ O _y oxide. Is added, mixed and pulverized, and further preferably granulated by a spray drier or the like, and the particle size is adjusted to 2 to 300 μm. The obtained granulated mixed powder is further sprayed into an inert gas such as nitrogen by using a spraying method utilizing flame melting such as an oxygen / hydrogen flame, so that the entire raw material powder is uniformly dispersed. Coagulated powder. In this case, the properties and particle size distribution of the powder obtained vary depending on the spraying conditions. However, in the present invention, the spraying amount is usually 1 to 50 g / min, and the spraying temperature is 1.
It is preferably performed at 300 to 1600 ° C. [0012] powder obtained by the melt-solidification, generally, REBa ₂ after firing Cu ₃ O _y and RE ₂ BaCuO ₅
An oxide of RE compounded in a composition ratio such that
It is presumed that the oxide of Cu and the oxide of Cu and the components such as Pt are uniformly dispersed and mixed. In the present invention, the added amount of the component such as Pt is such that the rare earth oxide superconductor finally obtained contains 0.01 to 5% by weight on an element basis. If the addition amount is less than 0.01% by weight, the oxide superconductor in the form intended by the present invention cannot be obtained, and if it exceeds 5% by weight, REBa ₂ Cu ₃ O _y
The amount of precipitation of a crystal phase other than the crystal phase increases, which is not preferable.
In the present invention, the use of a powder in which the above-mentioned components such as Pt are uniformly dispersed and mixed is not required during melting and decomposition treatment after molding.
REBa ₂ C obtained by the presence of components such as t
The superconducting properties of u ₃ O _y can be significantly improved. The reason for this is not clear, but the uniformly dispersed Pt and other component particles act as nuclei for the formation of the 211 phase,
It is estimated that 211 phases can be very uniformly and finely dispersed in the three phases. In the present invention, after the above powder is formed into a predetermined shape using the powder, the corresponding REBa ₂ Cu ₃ O
heat treatment to the decomposition temperature above the melting temperature of the _y oxide superconductor, annealing in the same manner as in a known melting method, can be obtained by heat treatment in an oxygen atmosphere. As a molding method, a known molding method such as a doctor blade method, a press molding method, a casting method, or the like can be used to obtain a rare earth oxide superconductor as a bulk body. Alternatively, a molded article can be obtained by forming a molded article layer on a substrate of metal, ceramics, or the like by spray coating, powder coating, or the like using the above powder. In the present invention, the temperature not lower than the decomposition melting temperature depends on whether the RE component is Y, Gd, Dy, Ho, Er, or Yb.
° C, Gd is about 1050 to 1250 ° C, Dy is about 1000
~ 1200 ° C, Ho is about 1000-1150 ° C, Er is about 950-1100 ° C, Yb is a temperature in the range of about 900-1100 ° C. What is necessary is just to select suitably from the etc. In addition, the heat treatment is performed by maintaining the above temperature range for a predetermined time. The holding time is not particularly limited, and can be appropriately selected depending on the heating conditions and the like as in the above temperature range, and is usually 20 minutes to 2 hours. After the above heat treatment, the material is gradually cooled in the same manner as in a normal melting method, and is heated at a predetermined temperature under an oxygen atmosphere to thereby obtain REBa _2.
A Cu ₃ O _y oxide superconductor can be obtained. In this case, slow cooling is preferably carried out at a cooling rate of about 1 to 5 ° C. / hour. The heat treatment is usually performed in an oxygen atmosphere at 650 to 400.
It is preferable to hold at about 10 ° C. for about 10 to 50 hours. Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following examples. Example 1 Y: Ba: Cu in a molar ratio of Y ₂ O ₃ , BaCO ₃ , and CuO
= 1.8: 2.4: 3.4, and after adding and mixing Pt powder in the amount shown in Table 1, 9
Calcination was performed at 00 ° C. for 10 hours to obtain a calcined powder. The obtained calcined powder is wet-pulverized and mixed using ethanol, and further granulated with a spray dryer to a particle size of 100 to 300 μm.
Was adjusted. The obtained granulated powder was injected into a nitrogen atmosphere using an oxygen-hydrogen flame spraying apparatus, and the molten and solidified powder was collected on a copper plate. The obtained melt-solidified powder was pulverized in isopropyl alcohol by a rotary mill using zirconia balls. Each of the pulverized powders obtained above was formed into a pellet having a thickness of 10 mm and a diameter of 20 mm by press molding. The obtained pellets were placed in an electric furnace in an air atmosphere, held at 1150 ° C. for 1 hour, decomposed and melted,
It was gradually cooled at a rate of 1 ° C./hour from 980 ° C. to 920 ° C. Thereafter, the atmosphere in the furnace was further changed to an oxygen atmosphere at 450 ° C. for 1 hour.
Heat treatment was performed for 00 hours to obtain a pellet-shaped oxide superconductor. The magnetization hysteresis of each sample cut out from the obtained pellet of each oxide superconductor was determined by SQUA.
Was measured using an ID flux meter, calculated temperatures 77K, the Jc (A / cm ²⁾ in a magnetic field 1T. The results are shown in Table 1. [Table 1] Example 2 Except that Gd ₂ O ₃ was used in place of Y ₂ O ₃ , each melt-solidified powder was prepared in the same manner as in Example 1, and further molded into pellets. In air at 1150 ° C for 2
Hold for time to decompose and melt, then 1050 ° C to 950
Except for slowly cooling to 2 ° C./hour at 2 ° C., pellet-shaped oxide superconductors were obtained in the same manner as in Example 1. Jc was calculated for each sample cut out from the obtained pellets of each oxide superconductor in the same manner as in Example 1, and the results are shown in Table 2. [Table 2] Example 3 Except that Dy ₂ O ₃ was used in place of Y ₂ O ₃ , each melt-solidified powder was prepared in the same manner as in Example 1, and further molded into pellets. In air at 1100 ° C
Pellet-shaped oxide superconductors were obtained in the same manner as in Example 1 except that the mixture was decomposed and melted for a period of time, and then slowly cooled from 980 ° C. to 900 ° C. for 50 hours. Jc was calculated for each sample cut out from the obtained pellets of each oxide superconductor in the same manner as in Example 1, and the results are shown in Table 3. [Table 3] Example 4 Except that Ho ₂ O ₃ was used in place of Y ₂ O ₃ , each of the melt-solidified powders was prepared in the same manner as in Example 1 and further formed into pellets. In air at 1100 ° C
Hold for a time to decompose and melt, then from 1000 ° C to 900
Except for slowly cooling to 1 ° C./hour at 1 ° C., pellet-shaped oxide superconductors were obtained in the same manner as in Example 1. Jc was calculated for each sample cut out from the obtained pellets of each oxide superconductor in the same manner as in Example 1, and the results are shown in Table 4. [Table 4] Example 5 Except that Er ₂ O ₃ was used in place of Y ₂ O ₃ , each melt-solidified powder was prepared in the same manner as in Example 1, and further molded into pellets. The body is held in air at 1050 ° C. for 2 hours to decompose and melt, and then from 950 ° C. to 870 ° C.
Except for slowly cooling to 1 ° C./hour at 1 ° C., pellet-shaped oxide superconductors were obtained in the same manner as in Example 1. Jc was calculated for each sample cut out from the obtained pellets of each oxide superconductor in the same manner as in Example 1, and the results are shown in Table 5. [Table 5] Example 6 Except that Yb ₂ O ₃ was used in place of Y ₂ O ₃ , each melt-solidified powder was prepared in the same manner as in Example 1, and was further formed into pellets in the same manner. The body is held in air at 1050 ° C. for 1 hour to decompose and melt, and then from 950 ° C. to 900
Except for slowly cooling to 2 ° C./hour at 2 ° C., pellet-shaped oxide superconductors were obtained in the same manner as in Example 1. Jc was calculated for each of the samples cut out from the obtained pellets of the oxide superconductor in the same manner as in Example 1, and the results are shown in Table 6. [Table 6] [0027] From the above examples, the Pt and the like components with particles of the REBa ₂ Cu ₃ O _y oxide superconductor 0.01
It can be seen that the rare earth-based oxide superconductor obtained using the melt-solidified powder dispersed and contained by 0.5% by weight exhibits an extremely high Jc. [0028] According to the present invention, by conventional melting method using a specific melting and solidification powder, REBa ₂ Cu ₃ O _y oxide superconductor 211 phase to fix the magnetic flux lines are finely and uniformly dispersed And the resulting rare earth oxide superconductor is
It has a high Jc, is extremely easy to manufacture, and is industrially useful.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C01G 3/00 C01G 1/00 H01B 12/00 H01B 13/00 H01L 39/24 ZAA

Claims (1)

(57) [Claims 1 ] REBa ₂ Cu ₃ O _y (RE is Y, Gd, D
represents y, Ho, Er or Yb. ) Oxide superconductor
Containing RE, Ba and Cu components, and Rh, P
At least one element component of t and Ru is based on the element.
0.01 to 5% by weight and melted and solidified into powder
That the raw material powder is molded using, by heating the shaped article to a decomposition temperature above the melting temperature of the oxide superconductor, annealing, and heat treatment, RE ₂ BaCuO in REBa ₂ Cu ₃ O _y phase ₅ phases
A method for producing a rare earth oxide superconductor, characterized in that a finely dispersed oxide superconductor is obtained.