JPS63297203A - Production of superconductive material - Google Patents

Abstract

PURPOSE:To obtain an oxide superconductive material having high superconductive critical temperature and stable superconductive characteristics at a temperature to make electric resistance zero, by heat-treating a raw material oxide containing specific elements alpha, beta and gamma in a ratio to make the composition of the aimed substance in an O2-containing atmosphere. CONSTITUTION:A raw material oxide 3 containing (A) an element alpha (e.g. Ba or Sr) selected from groups IIa and IIIa of the periodic table, (B) an element beta(e.g. Y or La) selected from groups IIa and IIIa and containing the same material as that of the element alpha and (C) an element gamma (e.g. Cn) selected from groups Ib, IIb, IIIb, IVa and VIIIa is collected in such a way that a composition shown by the formula [x=beta/(alpha+beta) atomic ratio, 0.1<=x<=0.9; y and z are 0.4<=y<=3.0 and 1<=z<=5 when (alpha1-xbetax)=1]. Then the raw material oxide 3 is set in a chamber 1, the chamber 1 is evacuated through an exhaust vent 7, O2 is introduced from a gas inlet hole 6 to the chamber, O3 is generated through an electric source 5 and electrodes 2 at 10Torr O3 partial pressure to give an O3-containing atmosphere and the raw material oxide is heat-treated by a heater 4 at 500-1,000 deg.C to give the oxide superconductor shown by the formula.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing superconducting materials. More specifically, the present invention relates to a method for producing a superconducting material having a high superconducting critical temperature and excellent superconducting properties.

BACKGROUND OF THE INVENTION Superconductivity, which is said to be a phase transition of electrons, is a phenomenon in which the electrical resistance of a conductor becomes zero under certain conditions and exhibits complete diamagnetic properties. That is, under superconductivity, there is no power loss at all even when current is passed through a superconductor, and a high-density current continues to flow forever. For example, if superconducting technology is applied to power transmission, it will be possible to significantly reduce the approximately 7% power transmission loss that currently occurs with power transmission. In addition, applications as electromagnets for generating high magnetic fields include, for example, MHD in the field of power generation technology.
Along with power generation and electric motors, it is expected to be a technology that advantageously promotes the realization of nuclear fusion reactions, which are said to consume more electricity to develop than they do to generate electricity. In addition, N
It is expected to be used in MR1π meson therapy, high-energy physical experiment equipment, etc.

On the other hand, despite various efforts, the superconducting critical temperature Tc of superconducting materials could not exceed 23K of Nb3Ge for a long time, but last year, in the future, [:La, B
a1l 2CuO, or [:La, Sr]2cu○
A sintered material of 2NiF4 type oxide has been discovered as a superconducting material with a high Tc, and the possibility of realizing non-low temperature superconductivity is greatly increasing. These materials have a T of 30 to 50, which is dramatically higher than that of conventional materials. was observed, and more than 70 T. has also been observed.

As methods for producing these oxide superconductors, sintering is generally used for bulk products, and physical vapor deposition such as sputtering is used for thin films. Heat treatment is performed on a physical superconductor in an oxygen-containing cloud atmosphere.

Problems to be Solved by the Invention However, the superconducting properties of the oxide superconducting materials obtained so far are extremely unstable, and the temperature and electrical resistance at which superconducting phenomena begin are completely zero. The difference (ΔT) from the temperature Tcf was also large.

Therefore, an object of the present invention is to solve the above-mentioned problems and provide a method for producing a superconducting material with excellent characteristics, which has high Tc and stable superconducting properties.

Means for Solving the Problems The present invention has been completed as a result of repeated various experiments and studies in order to solve the above-mentioned problems.According to the present invention, the periodic table [a, I[a 1 selected from group elements
Species element α, periodic table ■a.

[[One type of element β selected from the elements of group a containing the same elements as α and Ib, nb, ■b, rVa of the periodic table
, a method for producing a superconducting material whose main feature is to heat-treat a raw material oxide containing at least one element T selected from Group VIIIa elements in an atmosphere containing ozone to produce an oxide superconductor. provided.

Function The main feature of the present invention is that an oxide superconductor raw material is heat-treated in an ozone-containing atmosphere to obtain an oxide superconductor with excellent properties.

The above oxide superconductor and/or raw material oxide has the general formula: (αl-Xβx)ryO2 (where α, β, and γ are the elements defined above, and X is α
The atomic ratio of β to +β, 0.1 ≦x≦0.9, and 0.4≦y≦3.0.1≦z, where y and 2 are <α, 1−xβx) as 1. It is preferable to use an oxide having a composition represented by (the atomic ratio is ≦5), for example, B
a -Y, -Cu -0 system, Ba2Y+Cu3
It is considered to be a mixed phase mainly composed of 0t-xz.

The oxide superconductor and/or the raw material oxide are preferably perovskite-type oxides or pseudo-perovskite-type oxides. Pseudo-perovskite refers to a structure similar to perovskite, and includes, for example, an oxygen-deficient perovskite type, an orthorhombic type, and the like.

Combinations of elements contained in the raw material oxide used in the present invention include Ba, Y, Al5Fe, Co, N
A combination consisting of at least one element selected from the group consisting of i5Zn, Cu, Ag, Ti, Ba5La and Al, Fe, Co, Ni,
1nSCu, Ag.

At least one selected from the group consisting of Ti
Combinations consisting of elements of species or Sr, La and Al, FeCo, Ni, Zn, Cu, Ag
A combination of at least one element selected from the group consisting of , , Ti is preferred.

Further, the atomic ratio of α and β in the raw material oxide used in the method of the present invention can be appropriately selected depending on the types of α, β, and T mentioned above. That is, in the case of Ba-Y, Ba-La, and 5r-La systems, Y/(Y+Ba) is in the range 06 to 0.
It is preferably 94, more preferably 0.1 to 0.4, and Ba/(La+8a) is 0.0
It is preferably from 4 to 0.96, more preferably from 0.08 to
More preferably, it is 0.45, Sr/(1
, a+Sr) is preferably in the range of 0.03 to 0.95, more preferably 0.05 to 0.1. If the atomic ratio of the raw material oxide deviates from the above range, the Tc will be low, probably because the crystal structure, oxygen vacancies, etc. of the obtained oxide superconductor will differ from the desired one.

According to the method of the present invention, the raw material oxide is heat treated in an atmosphere containing ozone. According to the findings of the present inventors, conventional oxide superconductors produced by sintering or physical vapor deposition and then heat-treated in an oxygen-containing atmosphere suffer from a lack of oxygen in the crystal structure due to lack of oxygen in the crystal. etc. are inappropriate, resulting in low Tc and unstable superconducting properties. Therefore, in order to improve superconducting properties, it is necessary to supplement oxygen by some method.

According to the method of the present invention, the heat treatment is performed not simply in an oxygen-containing atmosphere, but in an ozone-containing atmosphere.

Ozone is more active than oxygen, so it is more easily incorporated into crystals. Therefore, it has become possible to produce an oxide superconductor with superior superconductivity and conductive frame properties compared to conventional production methods.

This heat treatment is more preferably performed in an oxygen atmosphere containing ozone, and in that case, the ozone partial pressure is preferably IQ7 orr or higher.

The means for generating ozone is selected from methods such as silent discharge such as corona discharge, method of irradiation with ultraviolet rays, etc., depending on the shape and size of the oxide to be heat-treated, and the shape, size, and structure of the heating furnace determined accordingly. It is possible to do so.

Furthermore, during heat treatment, since the oxide is at a high temperature, the ozone taken in becomes oxygen and diffuses, improving the crystal structure of the oxide, improving uniformity, and making oxygen vacancies appropriate. At this time, the heating temperature is preferably 500°C to 1000°C, and this heat treatment preferably includes a step of slow cooling at a cooling rate of 10°C/min or less, and a process of rapid cooling at a cooling rate of 100°C/min or more. .

According to a preferred embodiment of the present invention, the heat treatment includes a cooling process in ozone. By this cooling method, oxygen, which was conventionally liberated during cooling, can be fixed in the crystal, and preferred oxygen-rich crystals can be obtained.

Furthermore, by heat treatment according to the method of the present invention, oxygen is supplemented to an oxide that does not exhibit superconductivity due to poor conditions during sintering or vapor deposition, resulting in a lack of oxygen in the crystal, resulting in excessive oxygen vacancies, and transforms into a superconductor. It is also possible to do so.

Next, the apparatus used to carry out the method of the present invention will be explained. FIG. 1 and FIG. 2 are schematic diagrams of an ozone furnace used for producing a superconducting oxide material by the method of the present invention.

The apparatus shown in FIG. 1 mainly includes a chamber 1, an electrode 2 attached to the chamber 1, a raw material oxide 3, and a heater 4. The chamber 1 is connected to a vacuum pump (not shown) through an exhaust hole 7, so that the inside can be evacuated.

Further, the chamber 1 is provided with an inlet 6 for introducing cloud gas.

The procedure for implementing the method of the present invention using this apparatus will be described below. The chamber 1 in which the reeds and the raw material oxide 3 are attached is evacuated and made vacuum. Next, 02 gas is introduced into the chamber 1 and a DC voltage is applied to the electrode 2 to generate ozone. Then, the heater 4 is energized to perform heat treatment.

The apparatus shown in FIG. 2 is particularly suitable when the raw material oxide is a thin film. It mainly consists of a source oxide 10 installed in the chamber 8 facing each other, a heater 11 that heats the source oxide, and a light source 12 that irradiates ultraviolet rays into the chamber 8 through the entrance window 9 of the chamber 8. . chamber 3
is connected to a vacuum pump (not shown) through an exhaust hole 14, and can evacuate the inside.

To carry out the method of the present invention using this apparatus, the following procedure is followed. The chamber 8 in which the raw material oxide 3 is attached is evacuated to a vacuum. 02 gas is introduced into the chamber 8, and the light source 1 is
From step 2, ultraviolet rays are irradiated to generate ozone. Heater 1
1, and heat treatment is performed.

EXAMPLES The present invention will be explained below using examples, but it goes without saying that the technical scope of the present invention is not limited to these examples in any way.

A superconducting material was produced using the ozone shown in FIG.

The manufacturing conditions for each example are shown in Table 1.

Example 1 As raw material oxides, Y2O3 and BaC0+ were mixed at a Y:Ba molar ratio of 1:2, and CuO was added in excess of 10% by weight over the amount at which the Y:Ba:Cu molar ratio was 1:2:3. YBa2 obtained by mixing, pre-sintering at 880℃, and sintering at 940℃
A Cu, 07 sintered body block was used. The block size is 20x30x3 mm.

The above oxide is placed in the chamber, and then the chamber is evacuated to a vacuum of L XIO'Torr or less, and then 1
Atmospheric pressure of 0.02 was introduced. A DC high voltage of 30 kV was applied to the electrode, and the electrode was heated from room temperature to 900° C. at a heating rate of 15° C./min, maintained at that temperature for 3 hours, and cooled at a cooling rate of 8° C./min.

For comparison, heat treatment was performed in the same manner as above in an oxygen atmosphere of 1 atm.

Next, samples were prepared to measure the resistance of each of the obtained oxides. For the sample to be subjected to resistance measurement, a pair of layer electrodes were further formed by vacuum evaporation on both ends of the produced oxide, and the AI main electrode lead wire was soldered to the sample.

The heat treatment conditions and the measurement results of Tc and Tcf (the temperature at which the electrical resistance becomes completely zero) are shown in Table 1.

Example 2 As raw material oxides, La2O3 and BaC0* were used as La:f
3a were mixed at a molar ratio of 1:2, and CuO was added to form a:Ba:C.
A LaBa2Cu, 07 sintered body block obtained by mixing 10% by weight of u in excess of the molar ratio of 1:2:3, pre-sintering at 870°C, and sintering at 955°C was used. The heat treatment procedure is the same as in Example 1.

For comparison, heat treatment was performed in exactly the same way in an oxygen atmosphere of 1 atm, and Tc and Tcf of each sample were
Measurements were made.

The heat treatment conditions and the measurement results of Tc and Tcf are shown in Table 1.

Example 3 Using La2O3,5rCO+ as the raw material oxide, a+B
a at a molar ratio of 1:2, and CuO was mixed with La:Sr:Cu.
L obtained by mixing 10% by weight in excess of the amount with a molar ratio of 1:2:3, pre-sintering at 850°C, and sintering at 935°C.
An a5r2Cu307 sintered block was used. The heat treatment procedure is the same as in Example 1.

For comparison, heat treatment was performed in exactly the same way in an oxygen atmosphere of 1 atm, and Tc and Tcf of each sample were
Measurements were made.

The heat treatment conditions and the measurement results of Tc and Tcf are shown in Table 1.

Example 4 Using the raw material oxide used in Example 1 as a target, an oxide thin film produced on a 5rTi03 substrate by sputtering was heat-treated using the apparatus shown in FIG. The membrane is 5×8 mm and 3 μm thick.

A low-pressure mercury lamp was used as the light source, and quartz glass was used as the entrance window. After evacuating the inside of the chamber, 1 atm of O2 was introduced and irradiated with a low-pressure mercury lamp. Heating rate 1
It was heated from room temperature to 930°C at a rate of 0°C/min, maintained at that temperature for 8 hours, and cooled at a cooling rate of 5°C/min. For comparison,
Heat treatment was performed in exactly the same manner in an oxygen atmosphere of 1 atm, and Tc and Tcf were measured for each sample.

The heat treatment conditions and the measurement results of Tc and Tcf are shown in Table 1.

Example 5 Using the same material as in Example 1 as the raw material oxide, 8
A sintered block of oxide superconductor that was sintered only once at 40°C was used. Although this raw material oxide did not exhibit superconductivity, it was shown in Table 1 in 02 ozone generated by introducing 1.5 atmospheres of 02 gas using the apparatus shown in Figure 1 and applying a DC voltage of 4 QkV. After the heat treatment shown, it became a superconductor.

The heat treatment conditions and the measurement results of Tc and Tcf are shown in Table 1.

As a result, it was found that the method of the present invention can appropriately control the crystal structure and oxygen concentration of the oxide and produce a superconducting oxide with excellent properties. It has also been demonstrated that inappropriate sintering conditions can result in a lack of oxygen in the crystal, causing an oxide that does not exhibit superconductivity to be transformed into a superconductor.

Table 1 Effects of the Invention As detailed above, the superconducting material obtained by the method of the present invention has a higher T than that produced by the conventional method.
C and Tcf, and has stable superconducting properties.

This was obtained by configuring conditions that produce an oxide with a perovskite or pseudo-perovskite crystal structure, which is thought to be responsible for superconductivity, according to the characteristic manufacturing method of the present invention. be.

Further, even materials that do not exhibit superconductivity due to insufficient oxygen due to inappropriate sintering conditions, etc., become superconducting by heat treatment according to the method of the present invention. Therefore, the conditions for sintering and physical vapor deposition are more relaxed than in the past, and the mass productivity of oxide superconducting materials is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of one example of an ozone furnace used to carry out the method of the present invention, and FIG. 2 is a schematic diagram of another example. (main reference number)

Claims (27)

[Claims] (1) One element α selected from the elements of groups IIa and IIIa of the periodic table, one element β selected from the elements of groups IIa and IIIa of the periodic table that include the same elements as α, and the periodic table
An oxide superconductor is produced by heat-treating a raw material oxide containing at least one element γ selected from group Ib, IIb, IIIb, IVa, and VIIIa elements in an ozone-containing atmosphere. A method for producing superconducting materials. (2) The oxide superconductor or/and the raw material oxide have the general formula: (α_1_−_xβ_x)γ_yO_z (where α, β, and γ are the elements defined above, and x is the atomic ratio of β to α+β. and 0.1≦x≦0.9, and y and z are 0 when (α_1_−_xβ_x) is 1.
．． 4≦y≦3.0, 1≦z≦5 atomic ratio) The method for producing a superconducting material according to claim 1, wherein the oxide is an oxide having a composition represented by the following: . (3) The method for producing a superconducting material according to claim 1 or 2, wherein the oxide superconductor and/or the raw material oxide is a perovskite or pseudo-perovskite oxide. . (4) The raw material oxide is Ba and Y oxide, carbonate, nitrate or sulfate powder, Al, Fe, Co,
an oxide or carbonate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti;
250 to 12 by mixing with nitrate or sulfate powder
The method for producing a superconducting material according to any one of claims 1 to 3, wherein the superconducting material is pre-sintered at a temperature of 00°C. (5) The raw material oxide is a powder of Ba and La oxides, carbonates, nitrates, or sulfates, and Al, Fe, Co
, mixed with powder of oxide, carbonate, nitrate, or sulfate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti.
The method for producing a superconducting material according to any one of claims 1 to 3, wherein the superconducting material is temporarily sintered at a temperature of 230°C. (6) The raw material oxide is a powder of Sr and La oxides, carbonates, nitrates, or sulfates, and Al, Fe, Co
, mixed with powder of oxide, carbonate, nitrate, or sulfate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti.
The method for producing a superconducting material according to any one of claims 1 to 3, wherein the superconducting material is temporarily sintered at a temperature of 260°C. (7) The raw material oxide is Ba and Y oxide, carbonate, nitrate or sulfate powder, Al, Fe, Co,
an oxide or carbonate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti;
After mixing with nitrate or sulfate powder and pre-sintering, 70
5. The method for producing a superconducting material according to any one of claims 1 to 4, wherein the superconducting material is main-sintered at a temperature in the range of 0 to 1500°C. (8) The raw material oxide is powder of Ba and La oxides, carbonates, nitrates, or sulfates, and Al, Fe, Co
, mixed with powder of oxide, carbonate, nitrate, or sulfate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti, and pre-sintered.
A method for producing a superconducting material according to any one of claims 1 to 5, characterized in that the superconducting material is main-sintered at a temperature in the range of 50 to 1580°C. (9) The raw material oxide is a powder of oxides, carbonates, nitrates or sulfates of Sr and La, and Al, Fe, Co
, mixed with powder of oxide, carbonate, nitrate, or sulfate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti, and pre-sintered.
7. The method for producing a superconducting material according to any one of claims 1 to 6, wherein the superconducting material is main-sintered at a temperature in the range of 80 to 1530°C. (10) The raw material oxide is a powder of Ba and Y oxides, carbonates, nitrates, or sulfates, and Al, Fe, Co
, mixed with a powder of an oxide, carbonate, nitrate or sulfate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti.
Claim 1, characterized in that the material is physically vapor deposited using a material pre-sintered at a temperature of 200° C. as a vapor deposition source.
4. A method for producing a superconducting material according to any one of Items 4 to 4. (11) The raw material oxide is an oxide of Ba and La,
Carbonate, nitrate or sulfate powder and Al, Fe, C
mixed with powder of oxide, carbonate, nitrate or sulfate of at least one element selected from the group consisting of O, Ni, Zn, Cu, Ag, and Ti at a temperature of 220 to 1230°C. A method for producing a superconducting material according to any one of claims 1 to 5, characterized in that physical vapor deposition is performed using a temporarily sintered material as a vapor deposition source. (12) The raw material oxide is an oxide of Sr and La,
Carbonate, nitrate or sulfate powder and Al, Fe, C
mixed with powder of oxide, carbonate, nitrate or sulfate of at least one element selected from the group consisting of O, Ni, Zn, Cu, Ag, and Ti at a temperature of 234 to 1260°C. 7. A method for producing a superconducting material according to any one of claims 1 to 6, characterized in that physical vapor deposition is performed using a temporarily sintered material as a vapor deposition source. (13) The raw material oxide is a powder of Ba and Y oxides, carbonates, nitrates, or sulfates, and Al, Fe, Co
, mixed with powder of oxide, carbonate, nitrate, or sulfate of at least one element selected from the group consisting of Ni, Zn, Cu, Ag, and Ti, and pre-sintered.
The superconducting material according to any one of claims 1 to 4, wherein the superconducting material is physically vapor-deposited using a material sintered at a temperature in the range of 00 to 1500°C as a vapor deposition source. How to make (14) The raw material oxide is an oxide of Ba and La,
Carbonate, nitrate or sulfate powder and Al, Fe, C
After pre-sintering with a powder of an oxide, carbonate, nitrate or sulfate of at least one element selected from the group consisting of o, Ni, Zn, Cu, Ag, and Ti,
The superconducting material according to any one of claims 1 to 5, wherein the superconducting material is physically vapor-deposited using a material sintered at a temperature in the range of 650 to 1580° C. as a vapor deposition source. How to make (15) The raw material oxide is an oxide of Sr and La,
Carbonate, nitrate or sulfate powder and Al, Fe, C
After pre-sintering with a powder of an oxide, carbonate, nitrate or sulfate of at least one element selected from the group consisting of o, Ni, Zn, Cu, Ag, and Ti,
The superconducting material according to any one of claims 1 to 6, wherein the superconducting material is physically vapor-deposited using a material sintered at a temperature in the range of 680 to 1530°C as a vapor deposition source. How to make (16) Claims 1 to 13, characterized in that the atomic ratio Y/(Y+Ba) of the oxide superconductor and/or raw material oxide is in the range of 0.06 to 0.94. A method for producing a superconducting material according to any one of the above. (17) The superconducting material according to claim 16, wherein the atomic ratio Y/(Y+Ba) of the oxide superconductor or/and the raw material oxide is 0.1 to 0.4. Fabrication method. (18) The atomic ratio Ba/(La+Ba) of the oxide superconductor or/and raw material oxide is 0.04 to 0.96
15. The method for producing a superconducting material according to any one of claims 1 to 14, wherein the superconducting material is within the range of . (19) The atomic ratio Ba/(La+Ba) of the oxide superconductor or/and raw material oxide is 0.08 to 0.45
A method for producing a superconducting material according to claim 18, characterized in that: (20) The atomic ratio Sr/(La+Sr) of the oxide superconductor or/and raw material oxide is 0.03 to 0.95
16. The method for producing a superconducting material according to any one of claims 1 to 15, wherein the superconducting material is within the range of . (21) The superconducting material according to claim 20, wherein the oxide superconductor or/and the raw material oxide have an atomic ratio Sr/(La+Sr) of 0.05 to 0.1. Fabrication method. (22) A method for producing a superconducting material according to any one of claims 1 to 21, characterized in that heat treatment is performed in an oxygen atmosphere containing ozone. (23) The method for producing a superconducting material according to any one of claims 1 to 22, wherein the ozone partial pressure is 10 Torr or more. (24) The method for producing a superconducting material according to any one of claims 1 to 23, wherein the heat treatment includes heat treatment in a range of 500°C to 1500°C. (25) The method for producing a superconducting material according to any one of claims 1 to 24, wherein the heat treatment includes a step of cooling in an atmosphere containing ozone. (26) Claim 1, wherein the heat treatment includes a step of slow cooling at a cooling rate of 10° C./min or less.
26. A method for producing a superconducting material according to any one of Items 25 to 25. (27) The method for producing a superconducting material according to any one of claims 1 to 26, wherein the heat treatment includes a step of rapidly cooling at a cooling rate of 100° C./min or more. .