JPH04124033A - Superconducting materials containing vanadium and their production method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to novel superconducting substances, and includes stable oxide superconductors with high critical temperatures, superconducting materials using them,
Regarding devices, equipment and their systems.

〔Effect of the invention〕

Copper oxide La-Ba-Cu-0 with high critical temperature
A superconductor with a perovskite-type structure has been discovered. , (for example, JP-A-63-260853, JP-A-63-19)
No. 0712, etc.) After that, Y-B with a critical temperature of 90
a-Cu-○(M,ni,Wu,,1.R,Ashbur
n, C, J.

Torng, Y., Q.Jand and C.J., Chu.
: Phys, Rev, Lett.

58 (1987) 908) was discovered, and the application of superconductivity using liquid nitrogen as a refrigerant began to be expected.

In particular, progress has been remarkable in the development of materials with higher critical temperatures, and in 1988, B1-3r~Ca-Cu-○
system oxides were discovered as superconductors with a critical temperature of 1] and OK@ (tl, Maeda, S', Tan
aka, M.

Fukutomi and T, Asano: Jp.
n+Jr, Appl, Phys, 27 (1988) L
209), and TQ-Ba- with a critical temperature of 720
Ca-Cu-0 based oxide superconductor was discovered (Z, Z
, Sheng and A., M., Hermann: N.
ature 332 (1988) 55).

All of these have a perovskite containing copper oxide or a similar crystal structure, and it is known that the charge carriers are holes. On the other hand, as a system in which charge carriers are electrons, Nd-Ce-Cu-○ oxide was discovered as a 20-class superconductor (T, Tokur
a,)1. Takagi, S.

Llcida: Nature 337.345-34
7 (1989).

The simple manufacturing method for these is to mix and grind the carbonates or oxides of the respective constituent metals into powder, and then pulverize the mixture in air, oxygen, or a reducing atmosphere at a temperature of 800 to 1.100°C for 5 minutes to 1.100°C. Obtained by firing for hundreds of hours. However, layered or composite layered perovskite structures such as Y-Ba-Cu-○r B1-5r-Ca-Cu-○ and TQ-BaCa-Cu-0 systems include multiple superconductors with different numbers of layers. exist, each with a different critical temperature. In each superconductor, the change in free energy between structures with different numbers of layers is small, and it is extremely difficult to selectively synthesize each layer separately during synthesis. For example, in the Bj -5r-Ca-Cu-〇 system, Bj 25 r2C+, zOe (at critical temperature 7:
low temperature phase), Bi25r2CaICu208 (critical temperature 8
O-9QK: intermediate temperature phase), B i zS r2c a 2
Cu aolo (critical temperature 1.10 K: high temperature phase)
Each of these is a superconductor, and even if the atomic ratio of the raw materials is adjusted to 2:2:2:3 to synthesize B i 2S rzCa 2Cu 5our, which has the highest critical temperature among them, the sintered body remains moderately mild. It is synthesized as a mixture of a high-temperature phase and a high-temperature phase, and it is difficult to obtain a single phase.

[Problem to be solved by the invention]

As a result, problems arise in that the critical current density and critical magnetic field, which are the most important characteristics when applying this superconducting material to wires, coils, electronic elements, devices, etc., become low. In addition, these copper oxide perovskite superconductors are subject to chemical decomposition in the environment, particularly carbon dioxide gas and/or moisture, and in some cases, collapse of the crystal structure due to mechanical processing such as crushing, or due to temperature changes.

Changes in oxygen partial pressure cause oxygen vacancies in the crystal, which significantly reduces its superconducting properties and poses environmental stability problems.

[Means to solve the problem]

Although the causes of problems with conventional superconductors are not yet clear, there are many issues that need to be resolved before they can be put into practical use. The present invention relates to a new superconducting material that solves the above-mentioned problems, and aims to provide a stable oxide superconductor containing vanadium with a high critical temperature, and superconducting materials, devices, and equipment using the same. There are things.

Another object of the present invention is to provide a method for synthesizing an oxide superconductor containing vanadium. This led to the discovery of devices and equipment. That is, the chemical composition formula is the general formula A-B-A'-V- where A=alkali metal, lanthanide metal, yttrium,
At least one selected from scandium.

B=alkali metal A' = thallium, lead, bismuth, indium.

At least one selected from antimony and tin.

■ = Vanadium ○ = A stable oxide superconductor containing vanadium, which has a high critical temperature, can be produced by firing a composition in which the composition is made of oxygen in an oxidizing inert or reducing atmosphere such as helium, argon, nitrogen, or hydrogen. can be built. As another method, the above-mentioned composition is prepared by firing a mixture of component A, component B, and component (2) in an oxidizing inert or reducing atmosphere (2) such as helium, argon, nitrogen, hydrogen, etc., and then combining the fired product with the mixture. Synthesize a stable oxide superconductor containing vanadium hairs with a high critical temperature by firing a mixture of A' components in an oxidizing inert or reducing atmosphere such as helium, argon, nitrogen, or hydrogen. I can do it.

In addition, when synthesizing a superconductor containing the A' component with high vapor pressure, a mixture of the A component HA' component and the ■ component or the A component and the ■ component must be prepared in advance using, for example, helium, argon, etc.
Calcined in an oxidizing inert or reducing atmosphere such as nitrogen or hydrogen, and the A' component, for example /\lium, argon,
A under an oxidizing inert or reducing atmosphere such as nitrogen or hydrogen gas
React with the gas phase of component 'A', or sinter the mixed powder of component A and component (2) or the sintered powder and the gas phase of component A' in an oxidizing inert or reducing atmosphere such as helium, argon, nitrogen, or hydrogen. It can be made by

[Effect]

The raw materials for the composition of the present invention react during firing.

There is no particular limitation as long as the chemical composition formula is the general formula A-B-A'-V-○.However, A=alkaline earth metal, alkali metal, lanthanide metal, yttrium, scandium. At least one selected from ■3-Alkaline earth metal A' = thallium, lead, bismuth, indium.

At least one selected from the group consisting of antimony and tin. ■ = Vanadium (however, the average valence is 2.5 to 4.5); ○ = A, B, constituting the composition which is awashed with oxygen; A'■ Oxide, nitrate, carbonate ammonium salt of element.

Halides, organic acid salts, organometallic complexes, etc. can be used. Among these, it is preferable to use oxides, ammonium salts, diorganic acid salts, and the like.

Regarding the mixing of raw materials, there is no particular limitation as long as each component is homogeneously dispersed and mixed, and there are methods such as directly mixing and pulverizing the solid raw materials, or preparing an insoluble precursor of the above composition from an aqueous or non-aqueous solution of the raw materials. A method for producing mixed hydroxides, mixed oxalates, mixed complex salts, or a composite form of these
Examples include coprecipitation methods (sequential precipitation method, intimate coprecipitation method, etc.), precipitation kneading method, and the like. Alternatively, synthesis can also be carried out by preparing two to three components of the raw materials in advance by a coprecipitation method or a precipitation mixing method, and then impregnating the solution with a solution of the remaining components.

Alternatively, it can be synthesized by melting a mixed raw material of two or more of A, B, A', and V at a high temperature in advance, rapidly cooling the mixture to form an amorphous material, and firing the amorphous material.

The composition prepared by the method described above can be synthesized by firing the mixed powder as it is or molding it into a shape such as a pellet at a temperature of 700° C. or higher. The atmosphere at this time is selected to be an oxidizing inert or reducing atmosphere because it is necessary to provide vanadium with a low valence of 2.5 to 4.5 on average. For example, an inert atmosphere such as argon, helium, nitrogen or hydrogen.

- A reducing gas atmosphere such as carbon oxide or a mixed gas atmosphere thereof is preferred. Furthermore, when synthesizing using such a sintering method, repeating the process of re-pulverizing and sintering the sintered body multiple times is an effective method for synthesizing a homogeneous superconductor with high volume fraction and excellent properties. be.

The synthesis reaction can be carried out by the steaming method, sputtering method, c
A method in which the composition is directly formed into a film by vDt or thermal spraying is also a preferred method.

At this time, heating the substrate on which the film is to be formed or forming the film while supplying an activated reducing gas to the film are preferred methods for forming a high-quality thin film. When forming a thin film, in the case of a superconducting film containing the A' component with a high vapor pressure, there is a method of annealing the film in a vapor atmosphere of the A' component after the film is formed, or a method of annealing the film in a vapor atmosphere of the A' component, A component, B component, A' component, ■ component. Or A.

It is effective to alternately laminate the B, V mixed components and the A' component in accordance with the two compositions of their crystal structures. This alternate layering method is also an advanced method for selectively synthesizing superconductors with specific crystal structures.

A method for making the obtained oxide superconductor into a wire rod.

Methods such as plastic working methods, in which a metal pipe is filled with a superconductor or a mixed powder raw material and then stretched to form thin wires, thermal spraying on a substrate, and CVD method.

A method in which a tape-shaped wire is formed by forming a film using sputtering or vapor deposition, a method in which a superconductor or its raw material is melted and applied to a core material, and a molten metal quenching method.

A method is used in which a superconductor or its raw material powder is made into a slurry or paste with a binder and processed into a linear shape by tape casting or printing. The following is a detailed explanation of the case where wire rods are formed by the plastic working method as an example.

In advance, the superconducting material synthesized by the method described above is pulverized using a raikai machine or a ball mill to an average particle size of several microns to about 10-odd microns. This powder is poured into a metal pipe (for example, gold) with a diameter of 4 to 10 mm.

silver, gold-palladium, silver-palladium, copper-nickel,
(copper-aluminum, etc.), and the stiffened material is stretched using a swager to form a linear shape of 1 m or less. A superconducting wire can be produced by using this as it is or by rolling it into a tape shape using a roll or press and sintering it at a temperature of 700° C. or higher.

Since the superconducting powder is bonded by this sintering, when the wire material is processed into a coil shape or used for purposes such as wiring processing, it is preferable to sinter the wire material after processing it into that shape. At this time, in order to improve the orientation of the anisotropic superconductor in the sheathed wire, plate-shaped crystal grains are synthesized in advance and processed while applying shearing force, and superconductors or raw materials filled in the sheath are used. A method of melting and solidifying in one direction is effective.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1 Strontium oxide (SrO) and ammonium metavanadate (NHtV Oa) powders were prepared in a molar ratio of Sr:V=1
Weigh the ingredients so that the amount is 1:1, and grind and mix for about 30 minutes in a Raikai machine using an agate mortar. The obtained powder is placed in an aluminum crucible and fired in air at 980°C for 10 hours. The sintered body is again crushed for about 30 minutes using a Raikai machine using an agate mortar, and then fired in air at 980° C. for 10 hours. The obtained powder was reduced twice for 3 hours at 1050''C in 4% H2/He to obtain a 5rxVtOz, a reduced product.

Add thallium oxide (TQzOa) to this powder at a molar ratio of TQ.
Weigh it so that it is 0.2 and mix it in a Raikai machine for about 30 minutes. Pellets obtained by press-molding 2 g of the obtained powder into a diameter of 20 m were subjected to reduction treatment at 820° C. for 5 hours in a 4% H2/He and Tρ steam atmosphere.

The obtained sintered body is 10 mm x 5 m x 1 m+
A rod was cut out, four terminals were joined to it using indium solder, and the temperature change in electrical resistance was measured using liquid helium as a coolant using the west terminal resistance method. The results are shown in FIG. In the figure, 1 indicates that the current value during measurement is 0.5 mA, 2 indicates 7,
The electrical resistance change curve at 5 mA is shown. By the way, 3 is TQ, which is said to have the highest Tc value (122K) among the currently known oxide superconductors.
The resistance change of the zBa2ca2cua○1o superconductor is shown. As can be seen in Figure 1, the new material made by the method of the present invention shows a rapid change in resistance from around 150°C, and the current value is 0.
．． The detection limit of this measuring device is approximately 130 in the range of 5 to 7.5 mA (the generated voltage is 1 μV when a constant current is applied).
) showed the following values.

The electrical resistance of the sintered body obtained according to the present invention was measured after being left in the atmosphere for 48 hours, and the results are shown in FIG.

The resistance change shows a metallic behavior until around 150, then becomes semiconducting, and the resistance decreases rapidly from around 70, until 3.
The value was close to 0 and was below the measurement limit. Figure 11. The difference between 2 and 2 and 4 is that this sintered body was synthesized in a reducing atmosphere, so it is thought that it deteriorated due to oxygen or moisture in the air when left in the atmosphere. Therefore, the sample shown in FIG. 2 was further reduced in 4% H2 at 200 DEG C. for 1 hour, and the same measurements as described above were performed. The results are shown in FIG. 2.5.

The resistance change of No. 5 completely coincided with the resistance change shown in FIG. 1, and it was found that the deterioration of the new material according to the present invention was restored by H2 annealing.

Example 2 Strontium oxide (SrO), cerium oxide (Ce0)
2) Ammonium metabakedate (NH4VO3) powder in molar ratio Sv:Ce:V=0.9:0.1
: 1.0, and pulverized and mixed for about 30 minutes in a Raikai machine using an agate mortar. The obtained powder is placed in an aluminum crucible and fired in air at 980°C for 10 hours. The sintered body is again crushed for about 30 minutes using a Raikai machine using an agate mortar, and then fired in air at 980° C. for 10 hours. The obtained powder was reduced twice at 1050°C for 3 hours in 4% H2/He, and S ro, 9ceo, t
A Vz,a reduced product was obtained. Thallium oxide (TQ) is added to this powder.
203) so that the molar ratio TQ is 0.2, and mixed in a Raikai machine for about 30 minutes. 2g of the resulting powder
Pellets press-molded into a diameter of 20 mm contain 4% H2/
Reduction treatment was performed at 820° C. for 5 hours in a He and TQ vapor atmosphere. The obtained sintered body is 1. Own X 5 rrxm
X 1 ant was cut into rod shapes and the electrical resistance with respect to temperature was measured in the same manner as in Example 1. The results are shown in FIG. As shown in Figure 3, it shows a slight metallic change as the temperature decreases, and changes to a semiconductor state from around 50K to 31K.
The resistance suddenly decreased and reached a value below the lower limit of measurement at about 8K.

Example 3 In Example 1, T Q 203 was used instead of thallium oxide (TQzOa) mixed in the S rxVi○2.5 reductant.
A sintered body was obtained by mixing TQ20 or TQ40s obtained by thermally decomposing TQ20 or TQ40s at a molar ratio of 1.0, with all other modifications being made. The Tc onset of this sintered body showed a value of about 150.

Example 4 In Example 2, S r o, ec e 0.1. V
2. Instead of thallium oxide Tl2203) mixed with the Fl reduced product, TQzO or Tfla○8 obtained by thermally decomposing TΩ208 is mixed at a molar ratio of 1.0.
Other than that, the sintered body was obtained using a completely modified method. T of this sintered body
The onset of c showed a value of about 150.

Examples 15-17 In Example 2, the elements were Li and Na.

K, Ln, Y, Sc, Sr and Ca as B elements.

T of the sintered body treated in the same manner as in Example 2 using Ba
Table 1 shows the c-onset values. The composition ratios in the table are the values of the charged composition.

Table 1 Te values of various sintered bodies Examples 18 to 31 In Example 4, as elements Li, Na+, Ln
, Y, Sc, and Sr and Ca as B elements.

The composition ratio according to Examples 5 to 17 using Ba (however, T
The Tc oncent value of the sintered body subjected to the same treatment as Example 4 with ff = 1.0) corresponds to <Example 5~]-7, which is related to the TQ amount and TQ20 raw material, and is almost the same. The value was shown.

Examples 32 to 40 In Example 1, as the B element, Sr, Ba and C
Using a, T Q + B i + Pb as A′ element,
Table 2 shows the Tconset values of the sintered bodies that were heat-treated in the same manner as in Example 1 using In, Sb, and Sn. The composition ratios in the table are the values of the charged composition.

Table 2 Tc values of various sintered bodies Examples 41 to 45 SrO and NH4VO2 powder in molar ratio Sr:V=0
．． 05: 1.0, 3: ], 1: ], and weighed about 30% using a Raikai machine using an agate mortar.
Mix and grind for a minute. The obtained powder is placed in an aluminum crucible and fired in air at 980°C for 10 hours.

The sintered body is again crushed for about 30 minutes using a Raikai machine using an agate mortar, and then fired in air at 980° C. for 10 hours. Among these powders, the powder with Sr:V=1:1 is divided into three equal parts, and the remaining two have TQ of 0.1 and 2.
Add TQ20 so that it is 0 and mix thoroughly with a Raikai machine. 2g each from the 5 types of powder obtained above
was sampled and press-molded to a diameter of 20IlIll. TQ
Pellets without 4% H2/He in an atmosphere of 8
Reduction treatment was performed at 20°C for 5 hours. On the other hand, the pellet containing Tfl was subjected to reduction treatment at 820° C. for 5 hours in a 4% H2/He and TQ vapor atmosphere. A test piece measuring 10 rrn x 5 vrm x 1 rm was cut out from the obtained sintered body, and temperature changes in electrical resistance were measured using liquid helium as a coolant using a four-terminal resistance method. Tco of these sintered bodies
The values of nset are summarized in Table 3.

Table 3 Tc of various sintered bodies Examples 46 to 48 Table 4 shows the T c onset values of sintered bodies obtained by changing the firing atmosphere under the synthesis conditions of Example 1.

Table 4 Tc of sintered body when synthesized by changing the atmosphere Example 49 SrO and N H4V Os powders in molar ratio Sr:V=
Weigh it so that 1=1, and grind and mix for 3 degrees using a Raikai machine. Place the obtained powder in an alumina crucible and
Calcinate in air at 80°C for 10 hours. The fired body was again crushed and mixed using the Laikai machine, and fired at 980° C. for 0 hours in air.The fired body was further crushed and mixed using the Laikai machine. Using pellets made by press-molding this powder as targets, 15
A film composition is manufactured by sputtering on a single crystal substrate of rmX5I. At this time, an MgO single crystal (001) plane was used as the substrate. Accelerating voltage 2kV, argon atmosphere 1x10-
It was created under the condition of 2 Torr. The obtained film thickness is 0.5
It was μm. This film composition was prepared in 4% H2/He]0
Reduction treatment was performed at 50°C for 5 hours. The film was further treated in 4% F (2/He) containing TQ vapor at 820° C. for 5 hours.

Example 50 The pellets obtained in Example] were pulverized with a Raikai machine, and the powder with an average particle size of 3 to 5 μm was filled into a silver vibrator with a diameter of 6 m, and this was stretched to 1.8+ nm on a draw bench. , in the form of a tape. The obtained tape-shaped molded body was cut in advance to a length of 25 on to prepare a sample, which was heat-treated at 820''C in an argon atmosphere for 5 hours.The four terminals of this were connected with indium T1 solder, and liquid Helium 13 was applied. When we measured the temperature change in electrical resistance using a refrigerant, Tc ons
et 150K.

〔Effect of the invention〕

As explained above, the material of the present invention has a higher T c
Wire rods and coils due to high onset.

It is extremely effective when applied to electronics elements, devices, etc.

[Brief explanation of drawings]

FIG. 1 shows S r ITΩ obtained in one embodiment of the present invention.
, o , 2 V 10 sintered bodies and GoR2BazCa
Figure 2 is a graph showing the change in electrical resistance with respect to temperature of the 2Cug○1o sintered body.
sTΩo, 2 V 10 x A graph showing changes in electrical resistance with respect to temperature of the sintered body, FIG. 3 shows C eo, ts ro, 9T I20.
2V1. 2 is a graph showing changes in electrical resistance with respect to temperature of an OX sintered body. 1...Resistance change curve when 0.5 mA/al current is passed through the sintered body of the present invention, 2...7, 5 m
Resistance change curve when A/al current flows, 3・T
Ω2Ba2. Typical resistance change curves of ca2Cu, aO+, o sintered bodies, 4...48 hours in the atmosphere of the sintered bodies of the present invention
Electrical resistance change curve after standing, 5...Deteriorated sintered body 4
%H2/He after treatment at 200°C for 1 hour, 6-...Ceo, ss ro according to the present invention,
eT Qo, 2v108 sintered body shows an electrical resistance change curve with respect to temperature. 2 seats (ni)

Claims (1)

[Claims] 1. The chemical composition formula is the general formula A_X-B_W-A'_Y-V_Z-O_δ, where A=alkali metal, lanthanide metal, yttrium,
At least one of scandium B = alkaline earth metal A' = at least one of thallium, lead, bismuth, indium, antimony, tin V = vanadium (however, the average valence is 2.5 to 4.5) It is a composition represented by O=oxygen superconducting material. 2. In claim 1, A is an alkali metal;
A superconducting material characterized by being the lanthanide metal yttrium. 3. A superconducting material according to claim 1, characterized in that B is an alkaline earth metal. 4. A superconducting material according to claim 1, wherein A' is thallium, lead, or bismuth. 5. The superconducting material according to claim 1, wherein the basic crystal structure is perovskite, corundum, rutile, spinel, or a structure similar to these. 6. A superconducting material according to claim 1, wherein the basic crystal structure is perovskite or a similar structure thereof, and the superconducting material has a hierarchical structure of 1 to 4 layers. 7. The chemical composition formula is the general formula A_X-B_W-A'_Y-V_Z-O_δ, where A = alkali metal, lanthanide metal, yttrium,
At least one of scandium B = alkaline earth metal A' = at least one of thallium, lead, bismuth, indium, antimony, tin V = vanadium (however, the average valence is 2.5 to 4.5) O=oxygen X=0-0.67 W=0.05-3 Y=0.1-2 δ=1.3-6 Alternatively, a method for synthesizing a superconducting material, which is characterized in that it is synthesized from a step of firing in a reducing atmosphere. 8. The chemical composition formula is the general formula A_X-B_W-A'_Y-V_Z-O_δ, where A = alkali metal, lanthanide metal, yttrium,
At least one of scandium B = alkaline earth metal A' = at least one of thallium, lead, bismuth, indium, antimony, tin V = vanadium (however, the average valence is 2.5 to 4.5) O=Oxygen , a step of firing in an oxidizing inert or reducing atmosphere such as argon, nitrogen, hydrogen, etc., and a step of firing the mixture of the fired product and component A' in an oxidizing inert or reducing atmosphere such as helium, argon, nitrogen, hydrogen, etc. A method for synthesizing a superconducting material, characterized in that it is synthesized from. 9. A superconducting material according to claim 1, characterized in that the material is in the form of powder, bulk, or pellet. 10. A superconducting material comprising the superconducting material according to claim 1 and having a linear or flat plate shape. 11. A superconducting material according to claim 10, characterized in that the superconducting material has a shape that covers a surface made of a linear or structured object coated with a conductive material other than the superconducting material. 12. An electric wire using the material according to claim 10,
Magnets, magnetic shielding materials, antennas, resonators, and devices and systems using these. 13. A material containing the superconducting substance according to claim 1, characterized in that the material is in the form of a thin film with a thickness of 10 μm or less. 14. Electronic devices and sensors using the material according to claim 13, and systems using the same. 15. A Josephson element using the material according to claim 13, and an electronic device and system using the same.