JPH02188462A - Production of superconducting molded body of tl-alkaline earth metal-cu oxide - Google Patents

Abstract

PURPOSE:To introduce Tl into a specified multiple oxide after molding by bringing a molded body of the oxide into contact with a Tl compd. at a high temp. CONSTITUTION:Oxides or carbonates of components forming an oxide represented by formula I (where A is at least one kind of alkaline earth metal selected among Mg, Ca, Sr and Ba, 1 <y<2.5 and 1.5< z<3.5) are mixed and this mixture is calcined and molded. The resulting molded body is embedded in a powdery Tl compd. such as Tl2O5 and heated to 800-930 deg.C to obtain a superconducting molded body of Tl-alkaline earth metal-Cu oxide represented by formula II (where 0.1<w<2.0 and 1<X<7).

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides Tl-alkaline earthff1f+element-Culv
This article relates to a method for manufacturing compound superconducting ceramics.

(Prior art and its problems) High-temperature superconducting ceramic having an oxygen-deficient layered perovskite structure consisting of rare earth element-alkaline earth element-copper oxide represented by Y-Ba-Cu-0 system, B1-
Old-alkaline earth element-copper oxide system represented by Ca-5r-Cu-0 system and alkaline earth element-fIi4Iv compound system high temperature superconductivity represented by Tl-Ca-Ba-Cu-0 system Ceramics are expected to be used in a wide variety of fields, including transportation, heavy electrical equipment, computers, and medical equipment.

These oxide-based high-temperature superconducting ceramics also become superconducting when cooled with an inexpensive coolant such as liquid nitrogen, so they can be used as an alternative to Nb-'ri-based superconducting alloys, which only exhibit superconducting state in liquid helium. Furthermore, if it can be used in superconducting magnets, it would have great economic benefits.

In particular, Tl represented by the Tl-Ca-roa-Cu-0 system
-Alkaline earth element-copper oxide-based high-temperature superconducting ceramics are attracting attention because of their high critical temperature.

However, in the Tl-alkaline earth element-Cu-0 system, when a molded sintered body is manufactured using the Meishin molding method,
There were problems such as poor reproducibility of the superconducting properties of the shaped sintered body.

It has been pointed out that one of the causes of these problems is that it is difficult to obtain a superconductor with a desired composition with good reproducibility, as one component tends to volatilize and the high-temperature phase and low-temperature phase become mixed. ing.

Until now, Tl-alkaline earth element-copper oxide-based high-temperature superconducting ceramic molded sintered bodies have generally been made into bulk molded bodies by pressurizing and sintering raw material powder prepared by a dry mixing method or wet mixing method. A method of applying raw material powder as a paste to a substrate and sintering it to form a film or wire; A method of forming a thin film by physicochemical means such as sputtering or vacuum evaporation using a target made of superconducting ceramic components. It is prepared by various methods. In all of these methods, a Tl compound, for example, an oxide of Tl, 6n
H7 salts, carbonates, halides, alkoxides, etc. are used.

- Alkaline earth elements - C using any method
Even if a u-0 type superconducting molded body is prepared, there is a problem in that it is not possible to obtain a molded body having a high critical temperature and a high critical current density with good reproducibility. Furthermore, there is a need for a method for producing a superconductor that avoids the generation of highly toxic Tl during molding as much as possible, such as a method for producing superconductors that involves inserting paper after molding.

(Technical means for solving the problems) As a result of intensive research on the problems listed in L, the inventors have found that:
This led to the present invention.

The present invention provides the following steps: (1) A composite oxide molded body represented by the formula ^y Cu + Ox and a published compound are heated at 800 to 930°C.
The formula Tl-AyCu+0-
A method for producing a superconducting molded body shown in (In formula 12, A is Mg, Ca, Sr, Ha
At least one alkaline earth element selected from

+ < y < 2.5.1.5 < Z < 3.5.0.
1<w<2.0. and I<x<7. ), (2) Formula ^, Cu, +1. A molded body of the composite oxide represented by is coated with Tl metal, and in the presence of fa element,
TlwA, Cu+0, characterized by heat treatment at ℃
A method for producing a superconducting molded body represented by w (in the above formula, A is Mg, Ca, Sr, rla
represents an alkaline earth element of at least I PD selected from

l<3'<2.5. L, 5<7. <3.5
．． 0.1<w<2.0 and I<x<7. ), and Tl expressed by the formula (3) TlwAyCutO*
A method for manufacturing a superconducting molded body denoted by Shikikan, ^, Cu, and L (in formula l-2, Δ is Mg, Ca, Sr, B
represents at least one alkaline earth element selected from a.

1<y<2.5, 0.1<w<2.0. and 1<X<
It is 7. ).

Second, in the present invention, the method for producing a composite oxide molded body represented by Cu+O* is not particularly limited, but A, C
Preferably, a method is employed in which a raw material powder prepared by mixing oxides of each compositional element of u and 0 by a dry mixing method or a wet mixing method is pressed and sintered to form a bulk compact.

At least one alkaline earth element selected from Mg, Ca, Sr, and Ha includes Ba and Ca.
, Ba, Ca, and Mg, or Sr and Ca.

The dry mixing method, which is one of the methods for producing raw material powder for bulk molded bodies, is a method for producing powder of oxides or carbonates of constituent components of ^, Cu, 0, such as BaCO5, Can.

In this method, CuO powder is used as a starting material, and the raw material powder is prepared by pulverizing and mixing with a ball mill, crusher, pestle, mortar, etc., and then pre-sintering. The wet mixing method is a method in which a solvent that does not react with and is substantially insoluble in the starting materials is added to the same starting materials as in the dry method and mechanically mixed.6 Other methods for preparing raw material powder include: Examples include a sol-gel method, a flux method, and a hydrothermal method.

The shape of the molded article in the present invention is not particularly limited, and includes all molded articles such as membranes, wires, molds, etc. that can be obtained by per se known molding methods.

As a method for manufacturing the ^ycu+L film and wire, there is a method of applying the raw material powder as a paste to a substrate. In addition, in order to form a thin film, ^ycu+
Physicochemical methods such as sputtering, vacuum evaporation, etc. are most conveniently applied using single or multiple targets consisting of the components of L. Furthermore, the raw material powder is melted,
It can be drawn into a wire rod. In addition, the molded body can be prepared by a rubber press method, an injection molding method, a pressure molding method, a slurry casting method, etc., which are known as methods for molding ceramic green bodies.

In the present invention, as a first method, a Tl compound is heated and brought into contact with a molded body of a composite oxide represented by the formula A (Cu+O), but the method is not particularly limited except for the temperature.

As a Tl compound, rll'[I2 compound, 1°! Composite oxides are preferred. Examples of useful complex oxides include T
lwA, a compound represented by Cu+Oy, produced by mixing oxides, nitrates, carbonates, etc. of each element in desired proportions and firing, or the first method of the present invention^yC
It is produced by bringing a compound into contact with u+O□ under heating.

As a method of contacting, A,
A method of embedding a molded body of Cu+L, a method of bringing this molded body into contact with a gaseous compound, etc. can be employed. Furthermore, when the molded body is a thin film, the reaction rate can also be controlled by diluting the gaseous Tl compound with an inert gas or the like.

The heating temperature is 800-930°C, and the preferred temperature range is 870-910°C.

In the present invention, a molded sintered body of TlwA, Cu, 0, which is a high-temperature superconducting ceramic, is obtained by bringing the ^, Cu, O molded body into heating contact with the ``I compound.
When the contact time is increased, the composition of the sintered body changes, but a sintered body with a desired composition can be easily obtained by controlling the heating temperature and time.

In the present invention, as a second method, one formula A y Cu lO
A molded body of the composite oxide represented by x is coated with Tl metal and heat treated, but the method is not particularly limited except for the temperature and atmosphere.

The heating temperature is 800-930°C, and the preferred temperature range is 870-910°C. The heating atmosphere is in the presence of oxygen.

In the present invention, A, Cu+0. A shaped sintered body is obtained.

When the heating time is increased, the composition of the sintered body changes, but a sintered body with a desired composition can be easily obtained by controlling the heating temperature and time.

In the present invention, the formula TlwA, Cu+
The molded body of the Tl composite oxide represented by O* is heat treated, but the method is not particularly limited except for the temperature and atmosphere.

The heating temperature is 750-950°C, and the preferred temperature range is 830-900°C. The heating atmosphere is in the presence of oxygen.

The Tl compound, metal or rlPS1 composite oxide used as a Ti source in the 2nd (1st to 3rd) J method is. Tl atoms can be replaced with PB atoms if they are within 50 atomic %, and even in TlwA, Cu+O It can be replaced by pb atom.

(Example) Examples of the present invention are shown below.

Example 1 Ran, Cab, Cub (element ratio 2:3:
After mixing and stirring the powder of 4), a pellet (diameter I Om
1 mm thick) and sintered in an electric furnace at 885° C. for 2 hours in an oxygen atmosphere.

Place I0* 50 mg + Ijiki Beret (approximately 430 mg) in an alumina crucible, set the container, and heat to 895.
℃ in oxygen.

Figure 1 is an X-ray diffraction diagram of the pellet after heat treatment.
After minutes, a characteristic peak 2θ = 5.0° (002), 35.
3 @t00+4) 4Q, 5'' fQ (+161) It was confirmed that a high temperature superconducting molded body indicated by .Tl, 1llaaCaiCLIJff* was formed.

The critical temperature of the obtained superconducting molded sintered body was 12.0.

When the heat treatment is performed for 110 minutes.

The characteristic peak 2θ・6.1” (0021,18,1') belonging to Tl4ai(:a+cug[l*xnin)
(006), 36.9” (00121°43.2°
(From 00121, TlJa, which is known as a low temperature phase
It was confirmed that iCa+Cu20ay was formed.

Moreover, FIG. 2 shows the heat treatment time and pellet weight: ■1 change. With processing time, Tl. 0゜It was found that the love for width II increased with each reaction.

Example 2 Lieftenate salts of barium, calcium, and copper were mixed in toluene at an elemental ratio of 2:3:4, coated on a YSZ substrate, and thermally decomposed at 500°C. Apply 10 times,
The decomposition was repeated and heat treated in oxygen at 900° C. for 10 minutes to obtain a 10 micron film.

In an aluminum crucible, 1) a membrane with a substrate mentioned in 11. TlaO
60 mg of S powder was placed in 6 bottles, covered with a lid, and heat-treated in oxygen at 895° C. for 10 minutes.

Figure 3 is an X-ray diffraction diagram of the pellet after heat treatment, rL
It was confirmed that a high temperature superconducting film with C-axis orientation, which is small in size, was formed.

The critical temperature of the obtained superconducting film is +! It was IK.

Example 3 Ba1CasC by sputtering method to treat Mg0 group
A thin film (1 micron thick) having a composition of u404□ was formed.

In the same way as Example 2, in an aluminum crucible. TlJ.

It was heat-treated together with 50 mg of powder at 895° C. for 10 minutes in oxygen.

The critical temperature of the obtained superconducting film was 115.

Example 4 11aiCatCuJ4y silk wire (diameter 0.5mm
) by the melting method (1100° C.) and heat-treated in an alumina crucible in the same manner as in Example 2.

The critical temperature of the obtained superconducting film was 114.

Example 5 Bad, Can, Cub (element ratio 2:2:
After mixing and stirring the powder of 3), a pellet (diameter 10 mm)
, and sintered in an electric furnace at 885° C. in an oxygen atmosphere for 2 hours.

As in Example 1, heat treatment was performed in an aluminum crucible together with Tl-0s powder at 895° C. for 50 minutes in oxygen.

The critical temperature of the obtained superconducting film was 119.

Example 6 A film (thickness: 10 microns) having a composition of BaiCasCuaO4m was formed on a YSZ substrate in the same manner as in Example 2.

Tlsθs, Bad, Can, Cu powders are mixed and fired by a commonly known method to obtain Tl:+Ba2
A powder of CagCuJam was obtained.

The membrane with the substrate is placed in an aluminum crucible, and mj is placed on top of it.
600 mg of the above powder was placed, and the algae were heated at 895° C. for 10 minutes in oxygen.

The obtained film was confirmed by X-ray diffraction (from Figures 4 and 5 (the same applies hereinafter)) to be a superconducting film with a composition of TlJaaCasCuaOa++, and its critical temperature was 111
It was.

Example 7 BaaCa*C was deposited on Mg0 substrate by sputtering method.
A thin film (1 micron thick) having a uJsi composition was formed.

Place this in an aluminum pot and place TlsIla on top of it.
50 mg of gCagCua[lsx powder was placed, the lid was closed, and heat treatment was performed in oxygen at 895° C. for 10 minutes, 60 minutes, and 80 minutes, respectively.

The obtained film was heated for 10 minutes, and the composition confirmed by X-ray diffraction was as follows: published by ABaicaacus Ro 1. ．． When the critical temperature is 115K and heating for 60 minutes, Tl+BaiCaaCus
Osw, 117K, TlJaxCas when heated for 80 minutes
It was CLln04m, 118.

Example 8 Ran, Can, Cub (element ratio 2:3:
After mixing and stirring the powder of 4), a pellet (diameter l On
m, thickness Lmm) and sintered in an electric furnace at 885°C in an oxygen atmosphere for 2 hours.

50 mg of TlgOs and the pellet were placed in an alumina crucible, and the jar was covered with a lid and heat-treated in oxygen at 895° C. for 200 minutes. Furthermore, this pellet was placed in an aluminium crucible and heated at 885°C for 20 minutes, 35 minutes, and 40 minutes in an air circulation mode.
Heat treated for minutes.

The resulting pellet had a composition confirmed by X-ray diffraction when heated for 20 minutes, [1azCa, Cu502m, critical temperature of 120K, and a composition confirmed by X-ray diffraction when heated for 35 minutes.
Ll+0*x, 119K, 40 minutes heating: +Ba,
Ca5CuaOax *122.

Moreover, FIG. 6 shows the heat treatment time under air circulation and the weight change of the pellet. It was found that Tl oxide was released and the weight decreased as the treatment time increased.

Example 9 Tl. 0. , Ban, Cab, Cub (element ratio 4
:2:3:4) powder was mixed and stirred, then pelleted (
It was molded to a diameter of 10 mm and a thickness of 1 mm, and sintered in an electric furnace in an aluminum crucible at 885°C in an oxygen atmosphere for 2 hours.
A composition of laBaiCil+CuJa++ was formed.

Place this pellet in an aluminum crucible and place it under air circulation.
Heat treatment was performed at 85° C. for 20 minutes, 35 minutes, and 40 minutes.

The obtained pellet was heated for 20 minutes and the composition confirmed by X-ray diffraction was TlJa2CaiCuaO□, and the critical temperature was 116K, and when heated for 35 minutes it was rl+Bazcazcu.
Js*.

Tl+BazCa, lCu when heated at 117K for 40 minutes
It was on aOaw, 119.

Example 10 A Mg0 substrate of 11a2ca was prepared by sputtering method.
A thin film (1 micron thick) having a composition of 2 cu 302 m was formed.

50 mg of TlaOp in an alumina crucible, the Mg
An O-based thin film was placed on the base, covered with a lid, and heat-treated in oxygen at 895° C. for 200 minutes. Furthermore, this thin film with the substrate was placed in an aluminum crucible, and heated at 885°C for 15 minutes under air circulation for 3 minutes.
Heat treatment was performed for 0 minutes and 35 minutes.

The resulting film had a composition confirmed by X-ray diffraction of rlJa, 1caacuJ:+x when heated for 15 minutes, and a critical temperature of 116 when heated for 30 minutes, and Tl+1laiCa2Cu when heated for 30 minutes.
s mouth 3. ．． 118K, 35 minutes heating +BazCa
*Cu404m, 119.

Example I+ A wire rod (diameter 0.5 mm1) having a composition of BaxCazCuJ*z was molded by melting method +1100°C.

50 mg of Tl□L and the wire rod were placed in an alumina crucible, covered with a lid, and heat-treated in oxygen at 895° C. for 200 minutes. Further, this wire rod was placed in an alumina crucible and heat treated at 885° C. for 15 minutes, 30 minutes, and 35 minutes with air flow F.

When the obtained wire was heated for 15 minutes, the composition confirmed by X-ray diffraction was JaaCazCuJa++, and the critical temperature was 1.
When heated at 15K for 30 minutes, Tl+BaicaxcusO
im.

117, Tl, Ba, CasCua were heated for 35 minutes.
It was 04g, 118.

Example 12 A film (thickness: 10 microns) having a composition of BazCa and CuaOax was formed on a YSZ substrate F in the same manner as in Example 2. Next, one layer of Tl metal was deposited using the electron beam evaporation method.
Coated with a thickness of 0 microns.

Furthermore, this was placed in an aluminum crucible and heated under air circulation for 8 hours.
Heat treatment was performed at 85° C. for 15 minutes, 30 minutes, and 35 minutes, respectively.

The resulting film had a composition confirmed by X-ray diffraction of rlJaacaJu;+[]sx when heated for 15 minutes, and a critical temperature of 115K, and 1'l+BaiCa2C when heated for 30 minutes.
u303m.

When heated at 120 K for 35 minutes, Tl + [1aaCa:
+CuJ4m, 122.

Example 13 BazCa was deposited on Mg0 substrate-1- by sputtering method.
A thin film (1 micron thick) having a composition of sCu404□ was formed. Next, a metal layer was coated with a thickness of 1 micron using electron beam evaporation.

Furthermore, put this in an aluminum crucible, air circulation F, 8
Heat treatment was performed at 85° C. for 15 minutes, 30 minutes, and 35 minutes.

When heated for 15 minutes, the resulting film had a composition confirmed by X-ray diffraction of 0□ and a critical temperature of 1.
I 6 K, heating for 30 minutes: 1'l+B'a2Caz
CusOsx.

When heated at 120K for 35 minutes, Tl + Ba2CasCu
It was 40mm, 123mm.

Example j4 BatCat by sputtering method on MgO substrate
A thin film (1 micron thick) having a composition of Cu30it was formed. Next, Tl metal was coated with a thickness of 1 micron using electron beam evaporation.

Furthermore, this was placed in an aluminum crucible and heated under air circulation for 8 hours.
Heat treatment was performed at 85° C. for 15 minutes, 30 minutes, and 35 minutes.

The resulting film had a composition confirmed by X-ray diffraction of TlJaiCaxCu, lOi* when heated for 15 minutes, and a critical temperature of 115K, and rl+1lazcaxc when heated for 30 minutes.
utL++.

Tl+BaaCaiCuJ when heated at 119K for 35 minutes
4m.

It was on 121.

[Brief explanation of the drawing]

FIG. 1 is an X-ray diffraction diagram of the pellet of Example 1. FIG. 2 shows the heat treatment time and the weight change of the pellet in Example 1. FIG. 3 is an X-ray diffraction diagram of the pellet of Example 2. Figure 4 shows I'1JaiCaxCuJsy
．． Tl +138zCazCuimouthsmrl+Tla,
This is an X-ray diffraction diagram of ca*cu4Ly, and FIG. 5 is a partially enlarged view thereof. FIG. 6 shows the heat treatment time and weight change of pellets under air circulation in Example 8. Figure 1 Special fraud applicant Ube Industries Co., Ltd. 2θ Figure 2

Claims (6)

[Claims] 1. A method for producing a superconducting molded body represented by the formula Tl_wA_yCu_1O_x, which comprises bringing a composite oxide molded body represented by the formula A_yCu_1O_x into contact with a Tl compound at 800 to 930°C. (In the above formula, A represents at least one alkaline earth element selected from Mg, Ca, Sr, and Ba. 1<y<2.5, 1.5<z<3.5, 0.1 <w<2
．． 0, and 1<X<7. ) 2. 2. The method according to claim 1, wherein the Tl compound is a Tl oxide. 3. The manufacturing method according to claim 1, wherein the Tl compound is a complex oxide of Tl. 4. A in the formula Tl_wA_yCu_1O_x is Ba and C
The manufacturing method according to claim 1, which is a combination of a, Ba, Ca and Mg, or Sr and Ca. 5. A molded body of a composite oxide represented by the formula A_yCu_1O_z is coated with Tl metal and heated to a temperature of 800 to 930 in the presence of oxygen.
Tl_wA_yCu characterized by heat treatment at ℃
A method for producing a superconducting molded body represented by _1O_x. (In the above formula, A represents at least one alkaline earth element selected from Mg, Ca, Sr, and Ba. 1<y<2.5, 1.5<z<3.5, 0.1 <w<2
．． 0, and 1<x<7. ) 6. Tl_wA_yCu_1O, characterized in that a molded body of Tl composite oxide represented by the formula Tl_wA_yCu_1O_x is heat-treated at 750 to 950°C in the presence of oxygen.
A method for producing a superconducting molded body indicated by _x. (In the above formula, A represents at least one alkaline earth element selected from Mg, Ca, Sr, and Ba. 1<y<2.5, 0.1<w<2.0, and 1<x<
It is 7. )