JP2920001B2 - Method for producing rare earth oxide superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rare earth oxide superconductor, and more particularly to Rh, Pt and Rt.
REBa ₂ Cu ₃ O _y (RE is Y, Gd, Dy, Ho, etc.) exhibiting a high critical current density even under a high magnetic field in which at least one elemental component of u is uniformly dispersed as submicron particles.
Represents Er or Yb. ) Relates <br/> the manufacture how the oxide superconductor.

[0002]

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 No. 2-1
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.

[0007]

According to the present invention, REBa is provided.
₂ Cu ₃ O _y (RE is Y, Gd, Dy, Ho, Er or
Represents Yb. ) RE, Ba and oxide constituting oxide superconductor
Nitrate or acetate containing Cu component, Rh, Pt and
At least one elemental component of Ru is 0.01% on an elemental basis;
Obtained by spraying and pyrolyzing a solution in which about 5% by weight was dissolved.
Molded using the raw material mixed fine powder,
Heat to a temperature above the decomposition melting temperature of the conductor,
Cold, heat treated, RE ₂ BaCuO in REBa ₂ Cu ₃ O _y phase
It is characterized by obtaining an oxide superconductor in which _five phases are finely dispersed.
The method for producing a rare earth oxide superconductor described above is provided.

[0008]

[0009]

[0010]

The rare earth oxide superconductor produced according to the present invention comprises at least one elemental component of Rh, Pt and Ru (hereinafter simply referred to as Pt or the like) in a REBa ₂ Cu ₃ O _y oxide superconductor. ) Are uniformly dispersed and contained as submicron-order particles of 1 μm or less, so that the 211 phase of RE ₂ BaCuO ₅ exhibiting a pinning effect becomes REBa ₂
It is finely and uniformly dispersed in the 123 phase of Cu ₃ O _y , and exhibits superconductivity that is uniform and excellent as a whole.
It has a high Jc as in the G method. In order to uniformly disperse particles such as Pt on the order of submicrons, REBa ₂
RE of the raw materials constituting the Cu ₃ O _y oxide superconductor, a mixed powder obtained by solution spray-pyrolysis which contains dissolved nitrates or acetates and Pt or the like component containing Ba and Cu component as a raw material By using, the desired submicron Pt
Equi-component particles 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, an oxide or a peroxide of Ba, and an oxide of Cu; a calcined powder of the oxide mixed powder;
After firing the frit powder of the oxide mixed powder,
Add components such as Pt prepared as submicron particles in advance to those blended to constitute ₂ Cu ₃ O _y and RE ₂ BaCuO ₅ , and mold using a mixed fine powder uniformly dispersed and mixed. , Melt decomposition, slow cooling, heat treatment and the like. In this case, the particle size of the raw material powder of the RE, Ba, and Cu components excluding components such as Pt is not particularly limited, but is generally 20 μm or less, particularly preferably 1 to 5 μm. Raw material powders having a diameter of more than 20 μm are not preferred because the composition becomes non-uniform at the time of decomposition and melting.

In the present invention, each component material is
It is particularly preferable to use as a mixed fine powder of submicron particles of μm or less. For example, a powder or the like produced by a coprecipitation method can be used, and particularly preferably, the above-described REB is used.
RE, Ba as raw materials for forming a ₂ Cu ₃ O _y oxide
A mixed fine powder obtained by appropriately spraying a solution containing a nitrate or acetate of a Cu component and a predetermined amount of a component such as Pt in a high-temperature reactor and thermally decomposing the solution is used.

In the present invention, the above-mentioned spray / pyrolysis to obtain a preferred mixed fine powder is generally carried out by adding a mixture of nitrates or acetates containing the components of the raw materials to a mixture of Rh, Pt and Ru.
The solution were mixed and dissolved in adding one or more elemental constituents of, or, using a solution obtained by dissolving-containing Pt or the like component in the nitrate or acetate solution was blended each component of the raw material,
Spraying can be performed by spraying oxygen or air at the same time as spraying from a nozzle or the like into a high-temperature reactor, or by spraying with oxygen or air. In this case, as each component raw material used in the solution to be subjected to spraying / pyrolysis, a compound such as nitrate or oxide of RE, a compound such as nitrate, carbonate or oxide of Ba,
Compounds such as nitrates and oxides of Cu can be used,
Further, as the Pt component, a corresponding water-soluble Pt component compound, for example, platinum (IV) chloride or ruthenium chloride (RuCl ₃ ) can be used. Each compound can be appropriately selected from ones that dissolve in the solvent used.

Further, the properties, particle size distribution, etc. of the mixed fine powder obtained differ depending on the conditions of the above-mentioned spraying and thermal decomposition. In the present invention, it is usually preferable to carry out the reaction at a reaction temperature of 600 to 1000 ° C. and a residence time of 10 to 120 seconds. The solution concentration also affects the resulting mixed fine powder particles. In the present invention,
It is preferable to use a solution of about 0.001 to 0.5 mol / liter, preferably 0.05 mol / liter, in order to make the component particles such as Pt into a submicron order of about 1 μm or less. The fine powder obtained by the spray-pyrolysis, generally, REBa after firing ₂ Cu ₃ O _y and RE ₂ Ba
The oxide of RE, the oxide of Ba, the oxide of Cu and the component such as Pt, which are mixed at a component ratio so as to constitute CuO ₅ , have a concentration of 1 μm.
It is estimated that particles of submicron order of m or less were uniformly dispersed and mixed.

In the present invention, the amount of the component such as Pt is
The rare earth oxide superconductor finally obtained is contained in an amount of 0.01 to 5% by weight on an element basis. Can not be the addition amount is obtained an oxide superconductor in the form of interest of the present invention is less than 0.01 wt%, and when it exceeds 5 wt% of REBa ₂ Cu ₃ O _y crystal phase other than the crystalline phase The amount of precipitation is undesirably increased. In the present invention, the use of the mixed fine powder in which the components such as Pt as submicron particles are uniformly dispersed and mixed is achieved by causing the components such as Pt to exist as submicron particles at the time of melt decomposition treatment after molding. The superconducting characteristics of the obtained REBa ₂ Cu ₃ O _y can be remarkably improved. Although the reason is not clear, the submicron particles such as Pt act as nuclei for the formation of the 211 phase, and 21
It is presumed that one phase can be dispersed very uniformly and finely.

In the present invention, after the above-mentioned mixed fine powder is molded into a predetermined shape, the corresponding REBa ₂ C
It can be obtained by heat treatment at a temperature equal to or higher than the decomposition melting temperature of the u ₃ O _y oxide superconductor, followed by slow cooling and heat treatment in an oxygen atmosphere as in a known melting method. The molding method is
Using a known molding method such as a doctor blade method, a press molding method, a cast molding method, etc., the rare earth oxide superconductor can be obtained as a bulk body. Further, it can be obtained as a molded body in which a molded body layer is formed on a substrate of metal, ceramics or the like by spray coating, powder coating or the like using the above-mentioned mixed fine powder.

In the present invention, the temperature not lower than the decomposition melting temperature is different depending 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, the slow cooling is preferably performed at a temperature lowering 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.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. However, the present invention is not limited by the following examples. Example 1 Y (NO ₃ ) ₃ .6H ₂ O, Ba (NO ₃ ) ₂ , Cu (N
O ₃ ) ₂ .3H ₂ O in atomic ratio Y: Ba: Cu = 1.8:
It was weighed to 2.4: 3.4 and dissolved and mixed in distilled water. The obtained solution was adjusted to a YBa ₂ Cu ₃ O _y concentration of 0.05.
Diluted to a mole / liter, and further diluted with YBa ₂ Cu ₃
To _{O 6.8, PtCl 4 · 5H 2} O in the proportions shown in Table 1
Was added and dissolved. Next, into the reaction tube heated to 800 ° C., the obtained solution was atomized and introduced with an ultrasonic oscillator, and at the same time, 5 liters of oxygen gas per minute was jetted out as a carrier gas, to thereby obtain the raw material components in the solution. Pyrolysis was performed. Exhaust gases by collecting capturing the generated microparticles by pyrolysis while filtered through a filter to obtain a mixed powder of the raw materials. Each of the mixed fine powders obtained above was formed into a pellet having a thickness of 7 mm and a diameter of 20 mm by press molding. The obtained pellets were placed in an electric furnace in an air atmosphere, kept at 1150 ° C. for 1 hour to decompose and melt, and then gradually cooled from 1000 ° C. to 950 ° C. at 1 ° C./hour. Thereafter, the furnace was further heat-treated at 450 ° C. for 100 hours in an oxygen atmosphere to obtain a pellet-shaped oxide superconductor. Each sample cut from the pellets of the oxide superconductor obtained, respectively magnetization hysteresis was measured using a SQUID flux meter, calculated temperatures 77K, the Jc (A / cm ²⁾ in a magnetic field 1T. The results are shown in Table 1.

[0019]

[Table 1]

The RhCl ₃ · 3H ₂ O Example ₂ PtCl ₄ · 5H 2 O instead of
, And mixed fine powders were prepared in the same manner as in Example 1 except that they were mixed and added at the ratios shown in Table 2, and pelletized oxide superconductors were obtained in the same manner as in Example 1. For each sample cut out from the obtained pellets of each oxide superconductor, Jc was calculated in the same manner as in Example 1, respectively.
The results are shown in Table 2.

[0021]

[Table 2]

Example 3 Acetates of Y, Ba, and Cu are combined in an atomic ratio of Y: Ba: Cu
= 1.8: 2.4: 3.4, dissolved and mixed in distilled water to prepare each mixed fine powder in the same manner as in Example 1, and further in the same manner as in Example 1. Each pellet-shaped oxide superconductor was obtained. 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.

[0023]

[Table 3]

[0024] Example _{4 Y (NO 3) 3 ·} 6H 2 O in place to Gd (NO _{3) 3} · 5
Except that H ₂ O was used, each mixed fine powder was prepared in the same manner as in Example 1, and further molded into pellets, and each molded product was decomposed and melted at 1200 ° C. for 1 hour in the air. Next, pellet-shaped oxide superconductors were obtained in the same manner as in Example 1 except that the temperature was gradually decreased from 1070 ° C. to 960 ° C. at 1 ° C./hour. 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.

[0025]

[Table 4]

[0026] Example _{5 Y (NO 3) 3 ·} 6H 2 O in instead Dy (NO _{3) 3} · 5
Except that H ₂ O was used, each mixed fine powder was prepared in the same manner as in Example 1, and further formed into pellets, and each molded product was decomposed and melted at 1100 ° C. for 1 hour in the air. Next, pellet-shaped oxide superconductors were obtained in the same manner as in Example 1 except that the temperature was gradually cooled from 980 ° C. to 900 ° C. at 1.5 ° C./hour. 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.

[0027]

[Table 5]

Example 6 Ho (NO ₃ ) ₃ .5H ₂ O, Ba (NO ₃ ) ₂ , Cu (N
O ₃ ) ₂ .3H ₂ O in atomic ratio Y: Ba: Cu = 1.4:
It was weighed to 2.2: 3.2 and dissolved and mixed in distilled water. The resulting solution was adjusted to a HoBa ₂ Cu ₃ O _y concentration of 0.
Dilute to 0.05 mol / L and further add HoBa
₂ Cu ₃ O _6.8 and PtCl ₄ at the ratio shown in Table 6.
· The 5H ₂ O was dissolved added. Then, each mixed fine powder was prepared in the same manner as in Example 1, and further formed into pellets in the same manner. Up to 1.5 ° C
Each oxide superconductor in the form of pellets was obtained in the same manner as in Example 1 except that the temperature was slowly cooled per hour. 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.

[0029]

[Table 6]

Example 7 Instead of Y (NO ₃ ) ₃ .6H ₂ O, Er (NO ₃ ) ₃ .5
Except for using H ₂ O, each mixed fine powder was prepared in the same manner as in Example 1, and further molded into pellets, and each molded product was held in the air at 1100 ° C. for 30 minutes and decomposed and melted. Next, pellet-shaped oxide superconductors were obtained in the same manner as in Example 1 except that the temperature was gradually cooled from 1000 ° C. to 850 ° C. at 2 ° C./hour. 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 7.

[0031]

[Table 7]

Example 8 Instead of Y (NO ₃ ) ₃ .6H ₂ O, Yb (NO ₃ ) ₃ .5
Except that H ₂ O was used, each mixed fine powder was prepared in the same manner as in Example 1, and further molded into pellets, and each molded product was decomposed and melted at 1050 ° C. for 30 minutes in the air. Next, pellet-shaped oxide superconductors were obtained in the same manner as in Example 1 except that the temperature was gradually cooled from 950 ° C. to 850 ° C. at 2 ° C./hour. 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 8.

[0033]

[Table 8]

From the above examples, it can be seen that the rare-earth oxide superconductor obtained by using a mixed fine powder in which a component such as Pt is added as submicron particles in an amount of 0.01 to 0.5% by weight has an extremely high Jc. I understand.

[0035]

According to the present invention, REBa ₂ Cu ₃ in which 211 phases for fixing magnetic flux lines are finely and uniformly dispersed by a melting method.
An _Oy oxide superconductor can be obtained, and the obtained rare earth oxide superconductor 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

Claims (1)

(57) [Claims] 1. REBa ₂ Cu ₃ O _y (RE is Y, Gd, D
represents y, Ho, Er or Yb. ) Oxide superconductor
Nitrate or acetic acid containing RE, Ba and Cu constituents
Salt and at least one elemental component of Rh, Pt and Ru
Is a solution in which 0.01 to 5% by weight based on the element is dissolved.
Molding using raw material mixed fine powder obtained by spraying and thermal decomposition ,
The molded body is heated to a temperature equal to or higher than the decomposition melting temperature of the oxide superconductor, gradually cooled, and heat-treated to obtain REBa ₂ Cu ₃ O _y
A method for producing a rare-earth oxide superconductor, characterized in that an oxide superconductor in which a RE ₂ BaCuO ₅ phase is finely dispersed in a phase is obtained.