JPH0733517A - Oxide superconductive material and its production - Google Patents

Abstract

PURPOSE:To obtain an oxide superconductive material high in a critical electric current density also in a magnetic field and strengthened in the superconductive bonding of the crystal grain boundary against the magnetic field by mixing compounds giving the oxides of Ti, Pb, Sr, Ba, Ca and Cu and subsequently heating the mixture under specific conditions. CONSTITUTION:Tl2O3, PbO, BaO, SrO, CaO and CuO are mixed with each other, heated at >=840 deg.C and then at >=940 deg.C and subsequently at 880 deg.C to provide a superconductive material comprising a composition of the formula (Tl1-xPbx)i(Sr1-yBay)jCakCulOz (0.8<=i<=1.6, 1.6<=j<=2.4; 0.8<=k<=3.6; 1.6<=1<=4.6; 0.05<=x<=0.9; 0<=y<=0.5; 6<=z<=12), having a critical temperature of >=80K and having a non-superconductive phase comprising at least an element selected from Tl, Pb, Ba, Ca, and Cu left at parts of the crystal grain boundary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a superconductor using an oxide-based superconducting material, which uses liquid helium or liquid nitrogen as a refrigerant, and a superconducting wire, a superconducting coil, a magnetic shield, and the like. Manufacturing method.

[0002]

2. Description of the Related Art Conventional oxide high temperature superconducting materials have a very low critical magnetic field value, and when there is no magnetic field applied to the superconducting material, a large superconducting current density can be secured. When a magnetic field is applied to the superconducting material, even a small amount of superconducting current flows. Therefore, it was difficult to apply it when manufacturing an application product that actually flows a superconducting current. Therefore, as a method for obtaining a high critical current density even in a magnetic field, Y ₁ Ba ₂ Cu ₃ O _x is used in a Y-based superconductor.
A method such as introducing a pinning center by finely dispersing Y ₂ BaCuO ₅ in a superconductor matrix (Murakami Masato: The Japan Institute of Metals, 2)
9, 9 (1990), 749. ).

[0003]

The above-mentioned prior art, even if a pinning center exists and a large superconducting current flows in the bulk crystal grains, is a polycrystal when applied to a wire or the like. Since it is unavoidable, the junction of grain boundaries is weak against a magnetic field, and no consideration has been given to securing a superconducting critical current density in the magnetic field to a sufficiently large value, and even if a slight magnetic field is applied to the superconducting substance. There is a problem that the critical current density is greatly reduced.

An object of the present invention is to make an oxide-based superconducting material having a high critical magnetic field, have a high critical current density even in a magnetic field, and strengthen the superconducting coupling of grain boundaries against the magnetic field.

[0005]

The above object is to provide a superconductor containing a superconducting material containing at least Tl, Sr, Ca, Cu, O as its constituent elements at least in part.
A non-superconducting phase composed of at least one element of Pb, Ba, Ca, and Cu is kept in a temperature range where it decomposes and forms from the superconductor, and while gradually cooling this, the superconducting phase is crystal-grown to obtain a superconducting material. This is achieved by dispersing a non-superconducting substance or a portion having a weak superconducting property in the inside or outside part of the crystal grains consisting of, and at the same time increasing the superconducting bondability between the crystal grains consisting of the superconducting substances.

When an oxide type superconducting substance, which is a type II superconductor, is cooled to a temperature below the critical temperature and kept in a superconducting state in a magnetic field, quantized magnetic flux lines penetrate into the superconducting substance. When an electric current is applied to the superconducting substance in this state, the Lorentz force acts on the magnetic flux lines, and the magnetic flux lines move in the superconducting substance. The movement of the magnetic flux lines causes a slight loss of energy, which is observed as the generation of electrical resistance. Therefore,
In order to secure a higher superconducting critical current density in a magnetic field, some measure may be taken to prevent the magnetic flux lines penetrating inside the superconducting material from moving even when a current is applied. In a conventional superconducting wire using a metal-based or intermetallic compound-based superconducting substance, a weak superconducting grain boundary or a non-superconducting precipitate is introduced into the matrix of the superconducting substance, and quantization occurs at this part (pinning center). We are producing a superconductor that traps the generated magnetic flux lines and keeps the invading magnetic flux lines from moving so that a current can flow in a magnetic field with substantially no resistance.

Even if a quantized magnetic flux line that has penetrated into the superconducting material is trapped and an electric current is applied, a portion that has a function of fixing the magnetic flux line so that the magnetic flux line does not move and electrical resistance is not generated. It is called a pinning center. When a non-superconducting part is introduced into a matrix composed of superconducting materials,
If there is a quantized magnetic flux line penetrating into the non-superconducting portion at a temperature below the temperature (hereinafter abbreviated as Tc) at which the superconducting substance undergoes a phase transition to the superconducting state, the energies become low, and the magnetic flux line is It will be fixed to the superconducting part. That is, when the non-superconducting portion is introduced into the matrix of the superconducting material, they all have the possibility of becoming pinning centers. However, the quantized magnetic flux depends on the type of material forming the pinning center, the size, shape and distribution state of the non-superconducting portion, the distance between the non-superconducting portions, and the bonding state at the interface between the superconducting material and the non-superconducting material. The power to fix the wire (pinning hose) is very different.

By introducing the pinning center into the superconducting substance, the critical current density in the superconducting crystal grains increases, but if the coupling between the crystal grains is weak, a superconducting current flows between the crystal grains with a slight applied magnetic field. However, the transport Jc sharply decreases. Improving the bondability of grain boundaries is an important issue when considering the practical application of superconductors, and the melting process is one of the effective means for solving it. In the melting method, the liquid phase reacts with each other to grow crystal grains made of a superconducting substance, and the bond between the crystal grains is improved. However, the liquid phase that has not completely reacted remains at the crystal grain boundaries and causes weak bonding. Therefore, the remaining liquid phase must be controlled. In the present invention, Tl, Pb, Ba, Ca, C
The non-superconducting phase composed of one or more elements of u corresponds to the liquid phase component, and the non-superconducting phase is allowed to remain at 10% or less, so that a superconductor having good bonding of crystal grain boundaries can be obtained. I found it.

In the present invention, it was not possible to clearly specify what kind of non-superconducting material was the pinning center. However, at least Tl, Sr, Ca, C
A superconductor consisting of u and O, with at least a portion of Tl and P
Heat treatment is performed in a temperature range where a non-superconducting phase composed of one or more elements of b, Ba, Ca, and Cu is decomposed and generated from the superconductor, and the superconducting phase is formed in the state where the superconductor and the non-superconducting phase coexist. Recrystallized, volume ratio of non-superconducting phase is 10%
By dispersing and precipitating a non-superconducting phase in a superconductor matrix as shown below, a superconductor with a pinning hose having a fairly high strength and good grain boundary connectivity, that is, a superconductor with a high superconducting critical current density even in a magnetic field, was prepared. I came to discover what I could do.

[0010]

In the present invention, the reason why a superconductor having a high superconducting critical current density can be produced even in a magnetic field is considered as follows. When the superconductor is heat-treated at a temperature of 800 ° C. or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca and Cu is decomposed and produced. In addition to the non-superconducting materials mentioned above, Ca, S and
(Ba, Sr) C, which is composed of r and Cu elements and has a ratio of (Ca, Sr) to Cu of approximately 1: 1 or 2: 1
There exists a non-superconducting substance having a phase composed of Sr and Ba which is considered to be O ₃ . When this is annealed, the decomposed and generated non-superconducting phases react with each other and the superconducting phase is recrystallized, and the non-superconducting phase consisting of one or more of Tl, Pb, Ba, Ca, and Cu remains in the superconductor. To do. It is considered that some kind of pinning center is introduced in the process of the recrystallization reaction of the superconductor.

Another important point that a high superconducting critical current density is obtained is to increase the bonding property between crystal grains made of a superconducting substance in order to pass an electric current through a superconductor which is a polycrystalline body. There is something. In the state where the liquid phase coexists, the diffusion of atoms becomes faster, so that the crystallinity of the crystal grain boundaries forming the superconductor is improved. The superconductor is Tl,
When crystal growth is performed in the state of coexisting with a non-superconducting phase composed of one or more elements of Pb, Ba, Ca and Cu, the crystallinity of the crystal grain boundaries constituting the superconductor is improved, but the non-superconducting phase is When 10% or more remains, the non-superconducting phase exists so as to surround the crystal particles made of the superconducting substance, so that the binding of the crystal particles made of the superconducting substance is hindered,
Since the superconducting current does not flow, the critical current density becomes low. Take enough reaction time for the superconducting phase to grow,
When the volume ratio of the remaining non-superconducting phase is set to 10% or less, the non-superconducting phase disperses and precipitates in the superconducting matrix, the bondability between the crystal particles made of the superconducting substance increases, and the high critical current density is achieved. Is believed to have been obtained.

The temperature at which the non-superconducting phase is generated varies depending on the composition of the superconductor, but for example, Tl: Pb: S.
r: Ba: Ca: Cu = 0.5: 0.5: 1.6: 0.4:
With the composition of 2.0: 3.0, when heat-treated at 870 ° C. and the structure thereof was observed, a non-superconducting phase containing Ca and Pb as main components was generated. Also, if heat treatment is performed at 880 ° C or higher,
A non-superconducting phase mainly composed of Ba and Pb is generated, and 970
When the product baked at ℃ is rapidly cooled to room temperature, Tl, Pb,
A non-superconducting phase composed mainly of Ba and Cu was generated.
There was evidence that these non-superconducting phases were liquid. In the superconductor heat-treated at a temperature at which these non-superconducting phases decompose and form, in addition to the non-superconducting phases, each element of Ca, Sr, and Cu has a ratio of (Ca, Sr) to Cu of about 1: 1. Alternatively, there is a non-superconducting substance having a phase of 2: 1 and a phase composed of Sr, Ba which is considered to be (Ba, Sr) CO ₃ . When this is annealed at 850 to 900 ° C., the decomposed and generated non-superconducting phases react with each other, and the superconducting phase is recrystallized, so that one or more of the non-superconducting phases,
That is, the non-superconducting phase made of one or more elements among Tl, Pb, Ba, Ca, and Cu remains in the superconductor. The remaining non-superconducting phase may be of any type, but if the remaining volume ratio is 10% or less, a superconductor having good bonding between crystal grains can be obtained. Further, by making Tl having a high vapor pressure larger than the stoichiometric composition, compositional deviation due to evaporation of Tl can be prevented and precipitation of a different phase can be suppressed.

The superconductor is subjected to heat treatment at a temperature of 800 ° C. or higher, preferably 850 ° C. or higher, because a melt starts to be generated at a temperature of 800 ° C. or higher. The heat treatment time depends on the temperature of the melt and is determined by the state of formation of the melt. The lower heat treatment time is longer and the higher heat treatment time is shorter. Also,
If the heat treatment is performed at a temperature higher than 1100 ° C., Tl is significantly evaporated and the melted phase cannot be recrystallized into a superconducting phase. Therefore, it is preferable to perform the heat treatment at a temperature of 1100 ° C. or lower. When the heat treatment is performed in a sealed tube such as an Ag pipe or in a Tl atmosphere, the evaporation of Tl can be suppressed.

[0014]

EXAMPLES Examples of the present invention will be shown below.

Example 1 As a starting material, a purity of 99%
The above Tl ₂ O ₃ , PbO, BaO, SrO, CaO, CuO
Was used. First, BaO, SrO, CaO, and CuO have an atomic ratio of Ba, Sr, Ca, and Cu of 0.4: 1.
Mix so as to be 6: 2: 3, and bake in air at 880 ° C. for 20 hours. This powder is crushed, and the obtained powder is T
The atomic ratio of l: Pb: Ba: Sr: Ca: Cu is 0.
Tl ₂ O to be 5: 0.5: 0.4: 1.6: 2: 3
Add ₃ and PbO and mix for 30 minutes on a fryer. The powder is formed into pellets having a diameter of 30 mm and a thickness of 3 mm, and the pellets are fired in an alumina crucible with a lid at 880 ° C. for 10 hours in the air. When powder X-ray diffraction measurement was performed on the obtained sintered body, it was confirmed that the sintered body contained 90% or more of a superconducting substance having a crystal structure as shown in FIG.
This sintered body was heated to 970 ° C. in the air, held for 1 hour, and then cooled to room temperature. The cross section of the obtained sample piece was polished, and the structure inside the sample was observed using a scanning electron microscope. The main phase generated is T by EDX analysis.
It consists of each element of l, Pb, Ba, Cu, and its composition is
Tl: Pb: Ba: Cu = 0.6-2.0: 0.79-2.
It was found to be 0: 0.34 to 1.0: 3.04 to 4.0. In addition, (Sr, Ca) CuO and CaO were precipitated. Therefore, after holding it at 970 ° C. for 1 hour, it was cooled to 880 ° C. at 5 ° C./min. A sample piece of the obtained sample was cross-section polished, and the structure inside the sample was observed using a scanning electron microscope. As a result, Tl _0.5 Pb
_The superconducting material represented by _0.5 Sr _1.6 Ba _0.4 Ca ₂ Cu ₃ O ₉ and having a crystal structure as shown in FIG. 3 was the main crystal phase. Also, E
The composition by DX analysis is Tl: Pb: Ba: Cu = 0 to
0.46: 1.1-2.0: 0.19-1.0: 0.25-
A non-superconducting phase of 0.85 was formed. The volume ratio of the non-superconducting phase obtained by mapping the SEM image is 5
%Met. Others, Tl _0.5 Pb _0.5 Sr _1.6 Ba _0.4 C
a ₁ Cu ₂ O ₇ superconducting material and Ca, Sr, C
It was found that a non-superconducting phase composed of u and a non-superconducting phase of (Ba, Sr) CO ₃ were included.

The superconducting critical temperature of this superconductor was 123 K as measured by the DC 4-terminal method. Also, VSM
When the BH curve of this sample at 77 K was measured by the device, the magnitude of hysteresis (ΔM) at an applied magnetic field of 1 Tesla was 20.0 emu / cc, and from this, the critical current density flowing in the crystal grains was determined. Jc =
It was 40,000 A / cm ² .

Next, the obtained superconductor is crushed and filled in a 5 wt% Pd-Au pipe having an outer diameter of 6 mm and an inner diameter of 4 mm,
After drawing to an outer diameter of 0.5 mm, it was rolled to a thickness of 0.1 mm. This was cut out as a 300 mm sample piece, heated to 950 ° C. at 30 ° C./min. In an oxygen atmosphere and held for 1 hour, then cooled to 880 ° C. at 30 ° C./min. Held About the obtained sample 77
When the critical current density was measured by a direct current 4-terminal method in a magnetic field of K, 1 Tesla, it was Jc = 36000 A / cm ² .

(Example 2) Purity 99% as a starting material
The above Tl ₂ O ₃ , PbO, BaO, SrO, CaO, CuO
Was used. First, BaO, SrO, CaO, and CuO have an atomic ratio of Ba, Sr, Ca, and Cu of 0.4: 1.
Mix so as to be 6: 2: 3, and bake in air at 880 ° C. for 20 hours. This powder is crushed, and the obtained powder is T
The atomic ratio of l: Pb: Ba: Sr: Ca: Cu is 0.
Tl ₂ O to be 5: 0.5: 0.4: 1.6: 2: 3
Add ₃ and PbO and mix for 30 minutes on a fryer. The powder is formed into pellets having a diameter of 30 mm and a thickness of 3 mm, and the pellets are fired in an alumina crucible with a lid at 880 ° C. for 10 hours in the air. When powder X-ray diffraction measurement was performed on the obtained sintered body, it was confirmed that the sintered body contained 90% or more of a superconducting substance having a crystal structure as shown in FIG. This sintered body was heated to 980 ° C in the air and held for 1 hour, then cooled to 880 ° C at 30 ° C / min.
Hold for 0 hours. The cross section of the obtained sample piece was polished, and the structure inside the sample was observed using a scanning electron microscope. As a result, the superconducting material represented by Tl _0.5 Pb _0.5 Sr _1.6 Ba _0.4 Ca ₂ Cu ₃ O ₉ and having a crystal structure as shown in FIG. 3 is the main crystalline phase, and is composed of Tl, Pb, Ba, and Cu elements. And the composition by EDX analysis is Tl: Pb: Ba: Cu
= 0 to 0.91: 0.88 to 2.0: 0.68 to 1.0: 2.
It was found that a non-superconducting phase of 79 to 4.0 and a non-superconducting phase of Pb and Ba as main components and Pb: Ba of 1: 1 were formed in 10% between the grains of the superconducting crystal grains. .

The sample was again heated to 880 ° C. in the atmosphere and kept for 30 hours. As a result, it was found that a non-superconducting phase containing Pb and Ba as main components and Pb: Ba being 1: 1 was formed in 7% between the superconducting crystal grains. In addition, a non-superconducting phase composed of Ca, Sr, Cu, (Ba, S
The non-superconducting phase of r) CO ₃ was deposited. When the critical current density of this superconductor was measured by the DC 4-terminal method, Jc =
It was 33000 A / cm ² .

(Example 3) Purity 99% as a starting material
The above Tl ₂ O ₃ , PbO, BaO, SrO, CaO, CuO
Was used. First, BaO, SrO, CaO, and CuO have an atomic ratio of Ba, Sr, Ca, and Cu of 0.4: 1.
Mix so as to be 6: 2: 3, and bake in air at 880 ° C. for 20 hours. This powder is crushed, and the obtained powder is T
The atomic ratio of l: Pb: Ba: Sr: Ca: Cu is 0.
Tl ₂ O to be 6: 0.5: 0.4: 1.6: 2: 3
Add ₃ and PbO and mix for 30 minutes on a fryer. This powder is molded into pellets having a diameter of 30 mm and a thickness of 3 mm and fired in an alumina crucible with a lid at 880 ° C. for 10 hours in the air. When powder X-ray diffraction measurement was performed on the obtained sintered body, it was confirmed that the sintered body contained 90% or more of a superconducting substance having a crystal structure as shown in FIG. This sintered body was heated to 950 ° C in the air and held for 1 hour, then cooled to 880 ° C at 30 ° C / min.
Hold for 0 hours. The cross section of the obtained sample piece was polished, and the structure inside the sample was observed using a scanning electron microscope. As a result, the superconducting material represented by Tl _0.5 Pb _0.5 Sr _1.6 Ba _0.4 Ca ₂ Cu ₃ O ₉ and having a crystal structure as shown in FIG. 3 is the main crystalline phase, and each of Tl, Pb, Ba, Ca, and Cu is It is composed of elements and the composition by EDX analysis is Tl: Pb: B.
a: Cu = 0 to 0.58: 0.88 to 2.0: 0.57 to
1.0: 1.70 to 3.3 non-superconducting phase, and Pb
It was found that 5% of non-superconducting phase having Ca as a main component and Pb: Ca of about 1: 2 was formed. Other, Ca,
A non-superconducting phase composed of Sr and Cu and a non-superconducting phase of (Ba, Sr) CO ₃ were deposited.

The critical current density of this superconductor in a magnetic field of 77 K, 1 Tesla was measured by the DC 4-terminal method.
It was c = 32000 A / cm ² .

(Example 4) As a starting material, a purity of 99%
The above Tl ₂ O ₃ , PbO, BaO, SrO, CaO, CuO
Was used. First, BaO, SrO, CaO, and CuO have an atomic ratio of Ba, Sr, Ca, and Cu of 0.4: 1.
Mix so as to be 6: 2: 3, and bake in air at 880 ° C. for 20 hours. This powder is crushed, and the obtained powder is T
The atomic ratio of l: Pb: Ba: Sr: Ca: Cu is 0.
Tl ₂ O to be 5: 0.5: 0.4: 1.6: 2: 3
Add ₃ and PbO and mix for 30 minutes on a fryer. This powder is molded into pellets having a diameter of 30 mm and a thickness of 3 mm and fired in an alumina crucible with a lid at 880 ° C. for 10 hours in the air. When powder X-ray diffraction measurement was performed on the obtained sintered body, it was confirmed that the sintered body contained 90% or more of a superconducting substance having a crystal structure as shown in FIG. This sintered body was heated to 980 ° C. in the air, held for 1 hour, and then cooled to room temperature. The obtained sample was heated to 880 ° C. in the atmosphere and kept for 170 hours. The cross section of the obtained sample piece was polished, and the structure inside the sample was observed using a scanning electron microscope. As a result, Tl _0.5 Pb _0.5 Sr _1.6 Ba
_The superconducting material represented by _0.4 Ca ₂ Cu ₃ O ₉ and having a crystal structure as shown in FIG. 3 is the main crystalline phase, and Pb and Ba are the main components.
Non-superconducting phase with Pb: Ba of approximately 1: 1 Pb, Ca
It was found that 4% of the non-superconducting phase in which Pb: Ca is the main component and Pb: Ca is approximately 1: 2 is formed between the superconducting crystal grains. In addition, a non-superconducting phase composed of Ca, Sr and Cu and a non-superconducting phase of (Ba, Sr) CO ₃ were deposited.

The critical current density of this superconductor in a magnetic field of 77 K, 1 Tesla was measured by the DC 4-terminal method.
c = 19000 A / cm ² .

(Example 5) As a starting material, a purity of 99%
The above Tl ₂ O ₃ , PbO, BaO, SrO, CaO, CuO
Was used. First, BaO, SrO, CaO, and CuO have an atomic ratio of Ba, Sr, Ca, and Cu of 0.4: 1.
Mix so as to be 6: 2: 3, and bake in air at 880 ° C. for 20 hours. The powder is crushed, and the obtained powder is T
The atomic ratio of l: Pb: Ba: Sr: Ca: Cu is 0.
Tl ₂ O to be 5: 0.5: 0.4: 1.6: 2: 3
Add ₃ and PbO and mix for 30 minutes on a fryer. The powder is formed into pellets having a diameter of 30 mm and a thickness of 3 mm, and the pellets are fired in an alumina crucible with a lid at 880 ° C. for 10 hours in the air. When powder X-ray diffraction measurement was performed on the obtained sintered body, it was confirmed that the sintered body contained 90% or more of a superconducting substance having a crystal structure as shown in FIG. Furthermore, this sintered body is heated to 880 ° C. in the atmosphere and
It was kept for 6 hours and cooled to room temperature. This was repeated 3 times. A sample piece of the obtained sample was cross-section polished, and the structure inside the sample was observed using a scanning electron microscope. As a result, the main crystal phase was Tl _0.5 Pb _0.5 Sr _1.6 Ba _0.4 Ca ₂ Cu ₃ O.
_In addition to the superconducting material represented by ₉ , there are 10 non-superconducting phases in which Pb and Ba are the main components and Pb: Ba is approximately 1: 1.
% Was generated. In addition, a non-superconducting phase composed of Ca, Sr, Cu and a non-superconducting phase of (Ba, Sr) CO ₃ were precipitated.

The critical current density of this superconductor in a magnetic field of 77 K, 1 Tesla was measured by the DC 4-terminal method.
c = 27,000 A / cm ² .

(Example 6) As a starting material, a purity of 99%
The above Tl ₂ O ₃ , PbO, SrO, CaO and CuO were used. First, SrO, CaO, and CuO are replaced with Sr and C, respectively.
Mix so that the atomic ratio of a and Cu is 2: 2: 3,
Bake at 880 ° C. for 20 hours in air. This powder was pulverized, and Tl ₂ O was added to the obtained powder so that the atomic ratio of Tl: Pb: Sr: Ca: Cu was 0.5: 0.5: 2: 2: 3.
Add ₃ and PbO and mix for 30 minutes on a fryer. The powder is formed into pellets having a diameter of 30 mm and a thickness of 3 mm, and the pellets are fired in an alumina crucible with a lid at 880 ° C. for 10 hours in the air. When powder X-ray diffraction measurement was performed on the obtained sintered body, it was confirmed that the sintered body contained 90% or more of a superconducting substance having a crystal structure as shown in FIG.
Furthermore, this sintered body is heated again to 880 ° C. in the atmosphere, and
Hold for 0 hours and cool to room temperature. A sample piece of the obtained sample was cross-section polished, and the structure inside the sample was observed using a scanning electron microscope. As a result, the main crystalline phase was Tl _0.5 Pb.
_As a superconducting substance represented by _0.5 Sr ₂ Ca ₂ Cu ₃ O ₉ , 7% of non-superconducting phase having Pb and Ca as main components and Pb: Ca of about 1: 2 was formed. Others, Ca, S
A non-superconducting phase composed of r and Cu and a non-superconducting phase of (Ba, Sr) CO ₃ were deposited.

The critical current density of this superconductor in a magnetic field of 77 K, 1 Tesla was measured by the DC 4-terminal method.
c = 25,000 A / cm ² .

Example 7 As a starting material, a purity of 99%
The above Tl ₂ O ₃ , PbO, BaO, SrO, CaO, CuO
Was used. First, BaO, SrO, CaO, and CuO have an atomic ratio of Ba, Sr, Ca, and Cu of 0.4: 1.
Mix so as to be 6: 2: 3, and bake in air at 880 ° C. for 20 hours. This powder is crushed, and the obtained powder is T
The atomic ratio of l: Pb: Ba: Sr: Ca: Cu is 0.
Tl ₂ O to be 5: 0.5: 0.4: 1.6: 2: 3
Add ₃ and PbO and mix for 30 minutes on a fryer. The powder is formed into pellets having a diameter of 30 mm and a thickness of 3 mm, and the pellets are fired in an alumina crucible with a lid at 870 ° C. for 10 hours in the air. When powder X-ray diffraction measurement was performed on the obtained sintered body, it was confirmed that the sintered body contained 90% or more of a superconducting substance having a crystal structure as shown in FIG.

Next, the obtained superconductor was crushed, filled in an Ag pipe having an outer diameter of 6 mm and an inner diameter of 4 mm, drawn to an outer diameter of 0.7 mm, and then rolled to a thickness of 0.1 mm. This 3
Cut out as a 00 mm sample piece, and in an oxygen atmosphere,
The temperature was raised to 870 ° C. at a rate of ° C./min. The cross section of the obtained sample was polished, and the structure inside the wire was observed using a scanning electron microscope. As a result, Tl _0.5 Pb _0.5 Sr _1.6 Ba _0.4 Ca ₂
The superconducting material represented by Cu ₃ O ₉ is the main crystalline phase, and P
b, Ba is the main component, Pb: Ba is about 1: 1 in the non-superconducting phase, Pb, Ca is the main component, and Pb: Ca is about 1:
The non-superconducting phase of 2 is 1% between the superconducting crystal grains.
It turns out that it is generating. Others, Ca, Sr, C
A non-superconducting phase composed of u and a non-superconducting phase of (Ba, Sr) CO ₃ were deposited. The critical current density of this sample was measured by a DC 4-terminal method in a magnetic field of 77 K and 1 Tesla.
c = 29000 A / cm ² .

Comparative Example A superconductor was synthesized by the same composition and heat treatment method as in Example 4, but the annealing time at 880 ° C. was set to 30 hours. The cross section of the obtained sample piece was polished, and the structure inside the sample was observed using a scanning electron microscope. As a result, Tl _0.5 Pb _0.5 Sr _1.6 Ba _0.4 Ca ₂ Cu
A superconducting material represented by ₃ O ₉ and having a crystal structure as shown in FIG. 3 is a main crystal phase and is composed of each element of Tl, Pb, Ba, and Cu, and the composition by EDX analysis is Tl: Pb: B.
a: Cu = 0.99 to 2.00: 0.58 to 1.07: 0
It was found that the non-superconducting phase of 0.20: 1.58 to 4.0 was formed in 22% between the superconducting crystal grains. When the critical current density of this superconductor was measured by the DC 4-terminal method, Jc was 100 A / cm ² or less.

[0014]

According to the present invention, superconductors and superconductors using an oxide superconducting material which has a high superconducting critical current density even in a high magnetic field are operated by liquid nitrogen cooling as well as liquid helium cooling. Wires and superconducting magnets can be obtained.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph of a superconductor according to the first embodiment.

FIG. 2 is a BH characteristic diagram of the superconductor according to the first embodiment measured at 77K.

FIG. 3 is an explanatory diagram showing a crystal structure of a superconducting material according to the first embodiment.

[Explanation of symbols]

1 ... Tl _0.5 Pb _0.5 Sr _1.6 Ba _0.4 Ca ₂ Cu ₃ O ₉ superconducting phase, 2 ... non-superconducting phase consisting of Tl, Pb, Ba, Cu elements, 3 ... Ca, Sr, Cu Non-superconducting phase consisting of elements, 4 ... (Ba, Sr) CO ₃ phase, 5 ... T
1 atom or Pb atom, 6 ... Sr atom or Ba atom, 7 ... Ca atom, 8 ... Cu atom, 9 ... Oxygen atom.

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[Procedure amendment]

[Submission date] March 12, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph showing a crystal structure of a superconductor in a first example.

FIG. 2 is a BH characteristic diagram of the superconductor according to the first embodiment measured at 77K.

FIG. 3 is an explanatory diagram showing a crystal structure of a superconducting material according to the first embodiment.

[Description of Reference Numerals] 1 ... Tl _0. Consisting _{5 Pb 0. 5 Sr 1.} 6 Ba 0. 4 superconducting phase represented by _{Ca 2 Cu 3 O 9, 2} ... Tl, Pb, Ba, each element of Cu Non-superconducting phase, 3 ... Non-superconducting phase composed of Ca, Sr, and Cu elements, 4 ... (Ba, Sr) CO ₃ phase, 5 ...
Tl atom or Pb atom, 6 ... Sr atom or Ba
Atom, 7 ... Ca atom, 8 ... Cu atom, 9 ... Oxygen atom.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshi Takeuchi 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Institute Ltd. (72) Inventor Yuichi Kamo 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Japan Corporation Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inheihei Matsuda, 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture

Claims (16)

[Claims] 1. A composition formula chemicals in general (of _{1) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1.6 1 .6 ≦ j ≦ 2.4 0.8 ≦ k ≦ 3.6 1.6 ≦ l ≦ 4.6 0.05 ≦ x ≦ 0.9 0 ≦ y ≦ 0.5 6 ≦ z ≦ 12 In a superconductor having a critical temperature of 80 K or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a portion between crystal grains, which is a superconducting material. . 2. The method according to claim 1, wherein Tl, Pb, Ba, C
A superconducting material in which the melting point of the non-superconducting phase consisting of at least one element of u is 980 ° C. or lower. 3. The Tl, Pb, Ca, C according to claim 1.
A superconducting material in which the melting point of the non-superconducting phase composed of at least one element of u is 900 ° C. or lower. 4. The Tl, Pb, Ba, C according to claim 1.
a, containing a non-superconducting phase composed of at least one element of Cu and having a magnetization hysteresis at 77K of 1T
Superconducting material with emu / cc or higher. 5. The composition formula of chemicals, generally, (of _{2) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a superconductor having a given critical temperature of 80 K or higher, the element ratio in a part between crystal grains is as follows: Tl: Pb: Ba: Ca: Cu = a: b: c: d: e 0 ≦ a ≦ A superconducting material in which a non-superconducting phase represented by 2.0 0.4 ≤ b ≤ 2.0 0 ≤ c ≤ 1.0 0 ≤ d ≤ 2.0 0.25 ≤ e ≤ 4.0 remains. Composition formula of wherein chemicals, generally, (of _{4) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a given superconductor with a critical temperature of 80K or higher,
A superconducting material, characterized in that a non-superconducting phase composed of at least one element out of Tl, Pb, Ba, Ca, and Cu remains at 10% or less in a part between crystal grains. Composition formula 7. chemicals, generally, (of _{5) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a method of synthesizing a material mainly composed of a superconductor having a given critical temperature of 80 K or more, a step of mixing each compound that gives an oxide of a constituent element, and a step of heat-treating this mixture to 840 ° C. or more And a method of synthesizing a superconducting material, further comprising the step of further heating it to 940 ° C. or higher and then heating it at a temperature of 880 ° C. or lower. Composition formula 8. chemicals, generally, (of _{6) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 It is characterized in that the critical temperature is 80 K or higher, and a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a portion between crystal grains. A wire made of superconductor. 9. The wire according to claim 8, wherein the critical current density of the transport at 77K of the wire made of a superconductor is 1000 A / cm ² or more at 1T. Composition formula of 10. chemicals, generally, (of _{7) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a superconductor having a critical temperature of 80 K or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a part between crystal grains. A magnet for generating a magnetic field using a wire that uses a superconductor. 11. The composition formula of chemicals, generally, (of _{8) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a superconductor having a critical temperature of 80 K or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a part between crystal grains. A device that has a magnet for generating a magnetic field using a wire that uses a superconductor. 12. The composition formula of chemicals, generally, (of _{9) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a superconductor having a critical temperature of 80 K or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a part between crystal grains. An electron spin resonance apparatus having a magnet for generating a magnetic field using a wire material using a superconductor. 13. The composition formula of chemicals, generally, (of _{10) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a superconductor having a critical temperature of 80 K or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a part between crystal grains. A nuclear magnetic resonance apparatus having a magnet for generating a magnetic field using a wire using a superconductor. 14. The composition formula of chemicals, generally, (of _{11) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a superconductor having a critical temperature of 80 K or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a part between crystal grains. A magnetic resonance imaging apparatus having a magnet for generating a magnetic field using a wire material using a superconductor. 15. The chemical formula of a chemical substance is generally represented by:_1-xPb_x)_i(Sr_1-yBa_y)_jCa_kCu_lO_z  0.8 ≤ i ≤ 1.6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 ≤ 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0 .5 in superconductors with a critical temperature of 80K or more given by 6 ≦ z ≦ 12
The Tl, Pb, Ba, Ca, Cu
A non-superconducting phase consisting of at least one element remains
Using a wire material using a superconductor
Magnetic levitation train with a magnet for generating a magnetic field. Composition formula of 16. chemicals, generally, (Formula _{13) (Tl 1-x Pb} x) i (Sr 1-y Ba y) j Ca k Cu l O z 0.8 ≦ i ≦ 1. 6 1.6 ≤ j ≤ 2.4 0.8 ≤ k ≤ 3.6 1.6 ≤ l ≤ 4.6 0.05 ≤ x ≤ 0.9 0 ≤ y ≤ 0.5 6 ≤ z ≤ 12 In a superconductor having a critical temperature of 80 K or higher, a non-superconducting phase composed of at least one element of Tl, Pb, Ba, Ca, and Cu remains in a part between crystal grains. A fusion device having a magnet for generating a magnetic field using a wire using a superconductor.