JPS63299018A - Manufacture of superconductive material - Google Patents

Abstract

PURPOSE:To obtain a superconductive material of a high critical temperature (Tc) having characteristics of excellent shape retention and stability by depositing raw material powder made up of mixture of specific powders on a metallic substrate and heating and sintering both of the substrate and the raw material powder. CONSTITUTION:Raw material powder which is either a powder mixture or baked powder obtained by baking and milling the powder mixture of oxide, nitride, fluoride, carbonate, nitrate, oxalate or sulfate of each of an element selected from group IIa of the periodic table, an element from group IIIa, and an element selected from groups of Ib, IIb, IIIb, IVa, and VIIIa, is deposited on a metallic substrate. Both the metallic substrate and the raw material powder are heated to sinter the raw material powder. This make it possible to form a compound oxide superconductive sintered material having a high Tc with an excellent repeatability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing superconducting members. More specifically, the present invention relates to a novel method for manufacturing superconducting members that can effectively utilize superconducting materials with high superconducting critical temperatures.

Conventional technology Under superconducting phenomena, materials exhibit complete diamagnetic properties, and no potential difference appears even though a finite steady-state current flows inside them. Therefore, various applications of superconductors as transmission media with no power loss have been proposed.

That is, its application fields include power fields such as MHD power generation, power transmission, and power storage, power fields such as magnetic levitation trains and electromagnetic propulsion ships, and NMR1π as an ultra-sensitive sensor for magnetic fields, microwaves, radiation, etc. There are many fields that can be mentioned, such as meson therapy, measurement fields such as high-energy physics experimental equipment, etc.

Furthermore, in the field of electronics, typified by Josephson devices, this technology is expected to not only reduce power consumption but also realize devices that operate at extremely high speeds.

By the way, superconductivity was once a phenomenon observed only at extremely low temperatures. That is, Nb, which is said to have the highest superconducting critical temperature Tc among conventional superconducting materials,
Even in Ge, an extremely low temperature of 23.2 was considered to be the limit of superconducting critical temperature for a long period of time.

Therefore, conventionally, in order to realize the superconducting phenomenon, superconducting materials have been cooled to below Tc using liquid helium with a boiling point of 4.2. However, the use of liquid helium imposes an extremely large technical burden and cost burden due to cooling equipment including liquefaction equipment, which has hindered the practical application of superconducting technology.

However, in recent years, it has been reported that sintered bodies containing oxides of Group A elements or Group Ma elements can become superconductors at extremely high Tc, and the practical application of superconducting technology using non-low-temperature superconductors has been delayed for some time. is about to be promoted. Examples that have already been reported are thought to have crystal structures similar to perovskite oxides such as orthorombic structures (La.

Da) zcuoa or (La, Sr), CL
Composite oxides having a so-called pseudo-perovskite crystal structure, such as I04, can be mentioned. For these substances, 30
A Tc of 50 to 50, which is significantly higher than that of conventional materials, has been observed, and a Tc of 70 or more has also been reported for superconducting materials made of Ba5YSCu complex oxides.

Problems to be Solved by the Invention The above-mentioned superconducting materials are generally obtained as sintered bodies, but sintered bodies are originally microscopically non-uniform in composition.
At present, the properties of the obtained superconducting sintered body are unstable and do not always reliably exhibit a high Tc. Furthermore, as a sintered body, it is very brittle and easily damaged, so it cannot currently be used for practical use as a side sole. .

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a new method for producing a superconducting material having a high Tc so as to maintain its shape well and exhibit stable characteristics. .

Means for solving the problem, namely, according to the present invention, one element α selected from Group 1 Ia of the periodic table, one element β selected from Group 1 Ia of the periodic table, and periodic Table 1b.

lIb5 I[Ib% rva, ■ oxide, nitride, fluoride of element T selected from group a,
A raw material powder, which is either a powder mixture of carbonate, nitrate, oxalate, or sulfate, or a fired powder obtained by firing and pulverizing the mixture, is deposited on a metal substrate, and the metal substrate and the raw material powder are Provided is a method for producing a superconducting material, characterized in that the superconducting material is formed by heating and sintering the raw material powder.

As a result of a detailed study of each step in the conventional manufacturing method, the present inventors concluded that it is particularly important to control the oxygen content of the sintered body, and completed the present invention. .

That is, a composite oxide sintered body having superconducting properties generally has the general formula = (αl-X βx>ry δ2 (however,
Element α is an element selected from group A of the periodic table, element β is an element selected from group IIIa of the periodic table, and element γ is an element selected from group I b of the periodic table. IIb, I[
b, ■It is one type of element selected from the a group, δ is ○, X is the atomic ratio of β to α + β, and y and 2 are 0 when (αI - wing β8) is 1. .4≦y≦3
．． The atomic ratio satisfies 0.1≦2≦5), but precise control is particularly required for the O content. This seems to be because, in the above-mentioned composite oxide, formation of an appropriate amount of oxygen vacancies is essential for realizing superconducting properties. However, on the other hand, it is known that excessive oxygen is released from the above composite oxide especially when exposed to high temperatures during sintering. In addition, especially Ba2
It is known that in complex oxides such as YCus Oy, oxygen is insufficient when transforming from a high temperature phase to a low temperature phase, and it is presumed that the above-described operation is effective.

Therefore, according to a preferred embodiment of the present invention, by oxidizing the surface of the metal substrate in advance, oxygen can be supplied from the substrate to the raw material powder during sintering. In other words, some oxides of specific metals as described below have the property of decomposing with oxygen within a predetermined temperature range, and by appropriately selecting the combination of this decomposition temperature and sintering temperature, sintering Oxygen sometimes released from the composite oxide can be supplemented.

The upper limit of the sintering temperature is the melting point of the fired body, and it is desirable that the difference from this melting point be within 100°C. This is because if the sintering temperature is lower than the above range, the sintering reaction of the sintered body powder will not proceed and the strength of the obtained sintered body will be extremely low. On the other hand, if the sintering temperature exceeds the above range, a liquid phase will be generated during sintering, causing melting or decomposition of the fired body. The Tc of the sintered body that has undergone such a reaction is greatly reduced.

In addition, as the above-mentioned complex oxide, especially Ba-Y-
Composite oxides such as CuSBa-La-Cu or Sr-La-Cu are cited as exhibiting particularly excellent properties, and these are said to have a so-called pseudo-perovskite crystal structure such as an orthorhombic structure. Seem.

On the other hand, examples of metals that can form oxides that decompose at high temperatures as described above include oxides such as Ag1Pd and Rh.

Similarly, in view of the oxygen-containing atmosphere, the dimensions of the product as a sintered body are preferably 0.8 mm or less in thickness. This is because the oxygen contained in the atmosphere has a favorable effect on the raw material powder during sintering, so the formation of an effective superconducting material only near the surface is to be effectively utilized. For the same reason, when using a method of applying paste kneaded with a binder to a substrate, the thickness of the paste is reduced to 1
It is preferable to set it to below mm. The reason why there is a difference between the thickness of the molded body and the thickness of the sintered body is that the dimensions of the product are reduced during the drying and binder removal processes.

It is also preferable to heat the metal substrate to a sintering temperature in advance when depositing the raw material powder. In other words, by such an operation, the raw material powder deposited on the metal substrate is sequentially sintered, so that the sintering reaction always proceeds over the entire thickness of the sintered body under the same conditions as on the surface. . When implementing this method, it is preferable that the particle size of the raw material powder is 5 μm or less, and by making the raw material powder finer, it is possible to achieve an effective sintering reaction, uniformity of the structure, and important functions in superconducting properties. An increase in grain boundary area is realized. Further, by heating the substrate in advance, the difference in coefficient of thermal expansion between the obtained sintered body and the substrate acts as compressive stress on the sintered body, which is also preferable from this point of view.

On the other hand, when attaching the raw material powder to the substrate as a paste in the attachment process, the binder used is polyvinyl butyral (PVB) using dibutyl phthalate (DBP) as a plasticizer, or polyvinyl gelcol (PVB) using water as a solvent. ) etc. These binders can be easily removed by heating at about 400°C to 700°C.

In addition, metals for forming the metal substrate include stainless steel, C
u, ＾gSAuSPt, Pd, Rh, Fe5Pb
SSn, Cd.

One metal selected from the group consisting of TiSWSMoSZr and Hf5TaSNb or an alloy thereof can be used. Cu, Fe, etc. are advantageous in that they are easy to process and inexpensive, stainless steel and Pt are advantageous in that they are stable metals and do not have a chemical effect on superconducting materials, and in addition, Ag5Pd, Rh, etc. Some of its oxides release 0 depending on temperature changes, and can be used to proactively control oxygen concentration.

For example, silver(I) oxide [:Ag*O) is heated at 160℃
Rhodium(III) oxide decomposes to release oxygen
(Rh 2 O) or (III) (RhzO3) decomposes at 1100° C. or higher and releases oxygen. Furthermore, lead oxide (rV) (Pb 2 O,) releases oxygen in two stages at temperatures above 290°C. Therefore, these substrate materials should be appropriately selected depending on the use of the superconducting material and the elements forming it.

Furthermore, according to the findings of the present inventors, the raw material powder further contains VSNb, TaSMo, W, TiSCrSMn5.
Ga.

an oxide or carbonate of at least one element selected from the group consisting of In5CdSSn, Tl, Pb, and Zn;
By incorporating sulfate or nitrate powder as an additive in an atomic ratio of about 0.01 to 0.15 to element T, better superconducting properties can be obtained. It should be noted that if the amount of the additive is less than the above range, no significant effect of the addition of the fifth element will be observed, while if it exceeds the above range, the superconducting properties will deteriorate.

EXAMPLES The present invention will be specifically explained below using examples, but the following examples are merely illustrative of the present invention, and the technical scope of the present invention is not limited by these disclosures.

Example BaCO3/Y2O with a purity of 3N or more and an average particle size of 5μ or less
3. The composition of each CuO powder after firing is Ba2YC.
The mixed powder mixed to give usOt is used as raw material powder [A
] was prepared.

In addition, the raw material powder (A) was preliminarily calcined at 900° C. for 12 hours in an oxygen stream, and the powder solidified into a cake shape was coarsely ground in a mortar, and then further ground to 4 μm using a ball mill made of high-purity alumina. Hereinafter, this step was repeated three times to obtain a raw material powder CB) for a composite oxide fired body.

Furthermore, the above-mentioned raw material powders (A) and CB) were kneaded with PVB (polyvinyl butyral) using a toluene-based solvent as a binder to form pastes [a] and [b], respectively.

On the other hand, as the metal substrate C2 group], stainless steel, Pt,
30mm x 10 each made of CuSAg5Rh
A plate of 0 mm x 2 mm was prepared. Also, CuSAg
, Regarding Rh, metal substrates (group Q) whose surfaces had been oxidized in advance were prepared.

Samples were obtained by combining these materials as shown in Table 1 and sintering them at 935° C. for 12 hours. still,
Raw material powders (a) and (b) kneaded with a binder
For those using
The binder was volatilized and removed by heating to 00°C.

Table 1 also shows the results of measuring the superconducting properties of the samples thus obtained. To measure the critical temperature Tc and the temperature TC1 at which the electrical resistance becomes completely zero, attach electrodes with Ag conductive toast to both ends of the sample according to the standard method, cool it to about 25°C, and then gradually increase the temperature. Observe the change in resistance. It was performed in a Tarabiostat using a DC four-point probe method. Temperature was measured using a calibrated Au(Fe)-Ag thermocouple. Also,
Five samples were prepared, and Table 1 shows the average values.

Table 1 (1) Table 1 (2) Effects of the Invention As detailed above, according to the method for producing a superconducting material according to the present invention, a composite oxide superconducting sintered body having a high critical temperature can be produced with good reproducibility. It becomes possible to manufacture.

In addition, since the superconducting sintered body manufactured according to the present invention is actually obtained in a form that is baked onto the surface of the substrate, if it is cut and used as it is, it is possible to prepare a mechanical support member and a current bypass during quenching in advance. It can be used as a superconducting material.

Claims (18)

[Claims] (1) One type of element α selected from Group IIa of the periodic table,
oxides and nitrides of one element β selected from group IIIa of the periodic table, and one element γ selected from groups Ib, IIb, IIIb, IVa, and VIIIa of the periodic table;
A raw material powder, which is either a powder mixture of fluoride, carbonate, nitrate, oxalate, or sulfate, or a fired powder obtained by firing and pulverizing the mixture, is deposited on a metal substrate, and the metal substrate is heated. Also, a method for producing a superconducting material, which comprises forming a superconducting material by heating a raw material powder and sintering the raw material powder. (2) The sintered body and/or fired body formed on the substrate has the general formula: (α_1_−_xβ_x)γ_yδ_z (where element α is one type of element selected from Group IIa of the periodic table. Element β is an element selected from group IIIa of the periodic table, and element γ is an element selected from group Ib, IIb, IIIb, V of the periodic table.
One element selected from group IIIa, δ is O, x is the atomic ratio of β to α+β, y and z
is (0.4≦y when α_1_−_xβ_x is 1
The method for producing a superconducting material according to claim 1, wherein the superconducting material is a composite oxide sintered body having an atomic ratio of 3.0 and 1≦z≦5. (3) The metal substrate is stainless steel, Cu, Ag, or Au.
, Pt, Pd, Rh, Fe, Pb, Sn, Cd, Ti,
The superconducting material according to claim 1 or 2, characterized in that it is made of one metal selected from the group consisting of W, Mo, Zr, Hf, Ta, and Nb or an alloy thereof. manufacturing method. (3) The method for manufacturing a superconducting material according to claim 1 or 2, wherein the metal substrate has a surface oxidized in advance. (4) The thickness of the raw material powder deposited on the metal substrate is 0.
Claim 1 characterized in that the diameter is 8 mm or less
3. A method for producing a superconducting material according to any one of Items 3 to 3. (5) The method for manufacturing a superconducting material according to any one of claims 1 to 4, characterized in that the raw material powder is attached to the metal substrate using a binder. (6) As the binder, polyvinyl butyral (P
6. The method for manufacturing a superconducting material according to claim 5, characterized in that VB) is used. (7) The method for manufacturing a superconducting material according to claim 5, characterized in that polyvinyl alcohol (PVA) using water as a solvent is used as the binder. (8) The superconducting material according to any one of claims 5 to 7, wherein the thickness of the raw material powder including the binder and deposited on the metal substrate is 1 mm or less. Production method. (9) The method according to any one of claims 5 to 8, characterized in that the solvent and binder are removed by heating to a temperature in the range of 400°C to 700°C in the atmosphere. Method for manufacturing superconducting materials. (10) The raw material powder further includes V, Nb, Ta, and M.
o, W, Ti, Cr, Mn, Ga, In, Cd, Sn,
At least one selected from the group consisting of Tl, Pb, and Zn
The superconductor according to any one of claims 1 to 9, characterized in that a powder of a certain element or an oxide, carbonate, sulfate, or nitrate of the element is mixed as an additive. Method of manufacturing wood. (11) The additive has an atomic ratio of 0 to the element γ.
．． 11. The method for manufacturing a superconducting material according to claim 10, wherein the amount of the superconducting material is mixed in a range of 0.01 to 0.15. (12) The sintering is carried out at a temperature within a temperature range of 100°C or less, with the upper limit being the melting point of the material with the lowest melting point among the raw material powders.
A method for producing a superconducting material according to any one of Items 1 to 11. (13) Manufacturing the superconducting material according to any one of claims 1 to 3, wherein the metal substrate is maintained at a sintering temperature when the raw material powder is attached. Method. (14) Claim 1, wherein the raw material powder and/or additive powder has a particle size of 5 μm or less.
A method for producing a superconducting material according to item 3. (15) The sintering is performed in an oxygen-containing atmosphere containing oxygen at a partial pressure of 0.5 to 50 atm. Method for manufacturing superconducting materials. (16) The above element α (however, element α is as defined above)
is Ba, the element β (however, element β is as defined above) is Y, and the element γ (however, element γ is as defined above) is Cu. A method for producing a superconducting material according to any one of items 1 to 15. Law. (17) The above element α (however, element α is as defined above)
is Ba, the element β (however, element β is as defined above) is La, and the element γ (however, element γ is as defined above) is Cu. A method for producing a superconducting material according to any one of items 1 to 15. (18) The above element α (however, element α is as defined above)
is Sr, the element β (however, element β is as defined above) is La, and the element γ (however, element γ is as defined above) is Cu. A method for producing a superconducting material according to any one of items 1 to 15.