JPH03223153A - Oxide superconductor and its production - Google Patents

Abstract

PURPOSE:To improve critical temperature by preparing a raw material comprising Tl, Ba or Sr, Ca, one or more of rare earth elements and Cu in a specific atomic ratio and burning the mixture in an O2-containing atmosphere. CONSTITUTION:Powder of oxides of Tl, AE, Ca and Cu (AE is Ba or Sr and RE is one or more selected from Sc, Y and lanthanide) is blended in an atomic ratio of m/2/n (1-x)/nx/(n+1) (0<x<1 and (m) is 1 or 2 and (n) is >=1). Then the mixed powder is press molded, the molded article is burnt in an O2- containing atmosphere at 800-950 deg.C to give an oxide superconductor shown by the formula (Y is value sufficiently satisfying demand of valence), having a crystal structure of tetragonal system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thallium (Tff)-based oxide superconductor and a method for producing the same.

[Prior Art] In recent years, it has been announced that Tl-Ba-Ca-Cu-0-based oxide superconductors have a high critical temperature (Tc) of over 100. Research regarding the body is actively being conducted. And up to now, T
Reported oxide superconductors containing I are -Tll2B82Ca, -+Cu, 02m+4, T
IBa2Ca5-1Cu*02m+*,
and (TIP b,) S r 2 Cam-1Cu
It has a structure represented by sO2a+i.

[Problems to be Solved by the Invention] The object of the present invention is to provide a novel TIP-based oxide superconductor and a method for producing the same.

[Means and Effects for Solving the Problems] The oxide superconductor according to the present invention is characterized in that it contains a substance represented by the following formula: %. Here, AE represents at least one element selected from Ba and Sr. Further, RE is a rare earth element, and specifically represents one or more elements selected from Sc, Y, and lanthanoids. Furthermore, X is Q<x<1
m is 1 or 2, n is an integer of 1 or more, and y is a number sufficient to satisfy the valence requirements. Note that the value sufficient to satisfy the valence requirement here is a number selected such that the total charge of oxygen ions neutralizes the total charge of metal ions, and is not limited to integers but non-integers. There may be cases where

Among the rare earth elements represented by RE, the yttrium group elements, namely Y, Pr, Nd, and Gd.

Tb, Dy, Ho, Er, Tm, Yb, and Lu are preferred from the viewpoint of obtaining a high critical temperature.

Such an oxide superconductor has a tetragonal crystal structure in which a part of the Ca site of Tjl @ AE2Can Cu*+, O, is replaced with an element represented by RE. The amount of substitution in this case is the above-mentioned X, and the preferable range of the value of X is determined as appropriate depending on the values of m and n, and the type of AE and RE source search used. For example, when m and n are 1, AE is Ba and RE is Y, 0<x<0.5 is preferable.

Further, the method for producing an oxide superconductor according to the present invention includes T
j, AE, Ca, RE and Cu in atomic ratio substantially m:
The method is characterized by comprising a step of preparing raw materials containing a ratio of 2:n(1-x):nx:(n+1), and a step of firing this mixture in an oxygen-containing atmosphere.

Here, the elements and X represented by AE and RE.

The values indicated by m and n are the same as those described above.

The raw material used here only needs to have each element in substantially the above-mentioned ratio, and its form is not particularly limited, but it is preferably a mixture of oxide raw materials of each element.

In the firing step, the firing temperature is preferably in the range of 800 to 950°C, more preferably 880 to 910°C. The firing time is preferably 1 to 10 hours, more preferably 1 to 5 hours. Within this range, the oxide superconductor represented by the above-mentioned general formula % can be formed extremely effectively. Further, the firing is performed in an oxygen-containing atmosphere as described above. In this case, the amount of oxygen in the oxide superconductor depends on the cooling rate, and this cooling rate is set to a value that can satisfy the oxygen valence requirements of the oxide superconductor to be produced.

In the above raw material, when AE is Ba and RE is Y, it is preferable that X is in the range of 0<x<0.5. Also, by applying Ba and Y in this way, T, Ba,
The atomic ratio of Ca, Y, and Cu(7) is substantially 1:2:
(1-x): 880 to 9 raw materials such that x: 2
It is preferable to manufacture the oxide superconductor by firing at a temperature range of 00''C for an appropriate time, for example, about 3 hours.

The tetragonal Tit-based oxide, which has the above composition and is made by substituting an appropriate amount of a suitable rare earth element for a part of the Ca site of Tft, AE2 Can Cua++ o, is a new oxide that has never existed before. It is a superconductor and has a high critical temperature.

For example, if the basic composition is T(l B a 2 Ca o, tsYo2sc u
A superconductor expressed as 20 F has a critical temperature of 90°C, which is much higher than the boiling point of liquid nitrogen at 1 atmosphere of 77°F, and is expected to be applied to a wide range of applications.

[Example] Examples of the present invention will be described below.

Example 1 First, fine powders of BaC0 and CuO were mixed and fired,
Synthesize BaCuO2. Next, the synthesized B a
Powderize CuO2 and combine this powder with Tft 203,
By mixing Y203 and CaO fine powder, Tl,
Ba, Ca, Y, and Cu in an atomic ratio of 1:2:0. 9
:o, a mixed powder raw material containing at a ratio of 1:2 was prepared. In this case, since Tjl is toxic, these operations were performed in a glove box.

Note that this example shows the case where n is 1, but if n is 2 or more, CuO will be added in excess because Cu will be in excess of Ba.

Next, about 200 kg/cm of such mixed powder raw material
A pellet-shaped sample with a diameter of 1011% and a thickness of 1 to 1.5 cm was prepared by molding at a pressure of 2.

After that, in view of the high reactivity of Ti, the sample was loosely wrapped in gold foil that does not easily react with Ti, and due to the toxicity of Ti, an additional double trap was attached in the quartz tube and the sample was flowed with ff112.
It was calcined at 890° C. for about 3 hours in an oxygen flow of 0 mN/min, and then cooled at a rate of 10° C./min.

As a result, Tit Baz Cao, e Yo, + Cuz o7
An oxide superconductor with the following composition was synthesized.

Note that the material used to wrap the sample during firing is not limited to gold foil.
Any material that does not easily react with l may be used. Also, if the cooling rate is made faster, the valence of 0 becomes smaller than 7.

FIG. 1 is a diagram showing a powder X-ray diffraction pattern of Cu of this sample using alpha rays. The numbers displayed above the diffraction peaks in the figure are tetragonal Tp Ba2Cao, y
o, l represents the mirror surface index of Cu207.

As shown in this figure, although diffraction peaks of other materials were also observed, it was confirmed that a TI Ba2Ca(,,gyo,,Cu,07 phase) having a tetragonal crystal structure was synthesized.

Next, we determined the critical temperature of the sample after firing.

FIG. 2 is a diagram showing the results of measuring the temperature change in resistivity of this sample using the known four-terminal method. As shown in this figure, the transition to the superconducting state begins at 10K, and the electrical resistance disappears at 85. That is, it was confirmed that the critical temperature of this sample was 85°C. This value is the known T
TI Ba2 CaCu20.
is much higher than the critical temperature of 73, and higher than 77, which is the boiling point of liquid nitrogen.

Example 2 By the same method as in Example 1, Tl7. Ba.

The atomic ratio of Ca, Y, and Cu was 1:2:0.85:0.
A mixed powder raw material containing the ratio of 15:2 was prepared and molded in the same manner as in Example 1, and the firing temperature was set to 88.
A sample was prepared by firing under the same conditions as in Example 1 except that the temperature was 5°C. As a result, TI Baz Cao, g, Y
An oxide superconductor with a composition of 0, +5Cu207 was synthesized.

FIG. 3 is a diagram showing the powder X-ray diffraction pattern of this sample. Similar to Example 1, the diffraction pattern reveals that tetragonal TI Ba2 CaO, 85yo, 15c u207
The existence of was confirmed.

Moreover, FIG. 4 is a diagram showing temperature changes in the magnetic susceptibility of this sample using Kokon's alternating current magnetic susceptibility method. For this measurement method,
Since the temperature at which diamagnetism occurs corresponds to the critical temperature exhibiting superconducting properties, it was confirmed from this figure that the critical temperature of this sample was approximately 83.

Example 3 A mixed powder was prepared in the same manner as in Example 2, except that the ratio of Tj, Ba, Ca, Y, and Cu of the mixed powder raw materials was 1:220 and 8:0.2:2. Samples were prepared under the following conditions. As a result, TIB B'2 Cao,a y,,2Cu2
0. An oxide superconductor with the following composition was synthesized.

FIG. 5 is a diagram showing the powder X-ray diffraction pattern of this sample. As in Example 1, the presence of tetragonal TI Ba2Cao, ayo, Cu20t was confirmed by the diffraction pattern.

Moreover, FIG. 6 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 82°C.

Example 4 The same procedure as Example 2 was carried out except that a mixed powder was prepared with the ratio of T, Ba, Ca, Y, and Cu of the mixed powder raw materials at a ratio of 1:2:0.75:0.25:2. Samples were prepared under the following conditions.

As a result, Tp Ba2Cao, tqYo, zqCu2
An oxide superconductor with a composition of 0f was synthesized.

FIG. 7 is a diagram showing the powder X-ray diffraction pattern of this sample. Similar to Example 1, the diffraction pattern shows that tetragonal TI Ba 2 Ca 0.75Y0.2SCu 2
The existence of 07 was confirmed.

Moreover, FIG. 8 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 90°C.

Example 5 The same procedure as in Example 2 was carried out except that the mixed powder raw materials were prepared with a ratio of T, Ba, Ca, Y, and Cu of 1:2:o and 7:0.3:2. Samples were prepared under the following conditions. As a result, TI B a2 Cao, 7Yo, 3 Cu20
An oxide superconductor with a composition of 7 was synthesized.

FIG. 9 is a diagram showing the powder X-ray diffraction pattern of this sample. Similar to Example 1, the diffraction pattern reveals that tetragonal TI Ba2 Ca, Y6,3 Cu20. The existence of was confirmed.

Moreover, FIG. 10 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 88°C.

Example 6 Tjl 20s, BaO2, Cab as starting materials.

Using Cub, Y2Q, T II, B a,
The ratio of Ca + Y and Cu was 1:2:0.65:0.
A sample was prepared under the same conditions as in Example 2, except that a mixed powder was prepared at a ratio of 35=2. As a result, TJ? B
An oxide superconductor having the composition a 2 Ca o, b, Yo, sqc u 207 was synthesized.

FIG. 11 is a diagram showing the powder X-ray diffraction pattern of this sample. As in Example 1, the presence of tetragonal Tjl Ba2Cao6sYo, 1sCu20t was confirmed by the diffraction pattern.

Moreover, FIG. 12 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 85°C.

Example 7 The same procedure as Example 6 was carried out except that the mixed powder raw materials were made with a ratio of T, Ba, Ca, Y, and Cu of 1:2:0 and 6:0.4:2. Samples were prepared under the following conditions. As a result, Tfl Ba2Cao, 6Y0.4 Cu20t
An oxide superconductor with the following composition was synthesized.

FIG. 13 is a diagram showing the powder X-ray diffraction pattern of this sample. As in Example 1, the presence of tetragonal Tfl Ba, Cao, a yo4Cu, o was confirmed by the diffraction pattern.

Moreover, FIG. 14 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 75°C.

Example 8 In the same manner as in Example 1 except that Y2O was replaced with DYzOi, Tf), Ba, Ca, Dy, and Cu were mixed in an atomic ratio of 1:2:0. A mixed powder raw material containing the powders at a ratio of 9:o and 1:2 was prepared. This was molded under the same conditions as in Example 1 and fired under the same conditions as in Example 1 except that the firing temperature was 885°C to prepare a sample. As a result, TD Ba
An oxide superconductor with the composition 2Cao9DYo, r Cuz 07 was synthesized.

FIG. 15 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal Tp B a2
The presence of Cao, 9 D yo, I Cu207 was confirmed.

Moreover, FIG. 16 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 70°C.

Example 9 The ratio of Tj, Ba, Ca, Dy, and Cu of the mixed powder raw material was set to 1:2:o, 8:0.2:2, and the firing temperature was set to 90
A sample was prepared under the same conditions as in Example 8 except that the temperature was 0°C. As a result, Tl)Ba2Cao,s D)'0.
An oxide superconductor with the composition 2Cu2O7 was synthesized.

FIG. 17 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal TI Baz
Cao, s D) 10.2 The presence of Cu207 was confirmed.

Moreover, FIG. 18 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 70°C.

Example 10 "f, Ba, Ca, Dy of mixed powder raw material.

A sample was prepared under the same conditions as in Example 9, except that a mixed powder was prepared with the ratios of Cu and Cu being 1:2:0.7:Q and 3:2. As a result, Tfl Ba2Cao, 7DY
o3Cu20? An oxide superconductor with the following composition was synthesized.

FIG. 19 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal Tll B a
The presence of 2 Cao7DYo and i Cu207 was confirmed.

Moreover, FIG. 20 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 80°C.

Example 11 Y 'x O3 was replaced with HO203 in the same manner as in Example 1. A mixed powder raw material containing a proportion of
An oxide superconductor with the following composition was synthesized.

FIG. 21 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal TI Ba2C
The presence of ao, g Ho,...Cu2O7 was confirmed.

Moreover, FIG. 22 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 75°C.

Example 12 A mixed powder was prepared by changing the ratio of T, Ba, Ca, Ho, and Cu of the mixed powder raw materials to 1:2:0.6:0.4:2, and the firing temperature was 900°C. A sample was prepared under the same conditions as in Example 11.

As a result, Tp B a2 Cao, 'b Hoo, 4 Cu20
An oxide superconductor with the composition '7 was synthesized.

FIG. 23 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal TI Ba2C
The presence of ao, 6Ho (1,4Cu2O7) was confirmed.

Moreover, FIG. 24 is a diagram showing temperature changes in magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was approximately 90°C.

Example 13 Y2O, Er20. In the same manner as in Example 1 except that TJ, Ba, Ca, Er, and Cu were replaced with
:2:0.9:0. A mixed powder raw material containing 2 parts of This was molded and fired under the same conditions as in Example 8 to prepare a sample. As a result, an oxide superconductor having the composition TIBa2Cag, Ero1Cu207 was synthesized.

FIG. 25 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal Tl Ba2
The presence of cao, 9 E To, I Cu207 was confirmed.

Moreover, FIG. 26 is a diagram showing temperature changes in magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 65°C.

Example 14 T, Ba, Ca, Er of mixed powder raw materials.

A sample was prepared in the same manner as in Example 13, except that the ratios of Cu and Cu were 1:2:Q, 8:0.2:2, and the firing temperature was 890°C. As a result, TI) Ba2 Ca6
．． An oxide superconductor with the composition B E ro, 2 Cu207 was synthesized.

FIG. 27 is a diagram showing the powder X-ray diffraction pattern of the sample shown in FIG. 1. The diffraction pattern reveals that the tetragonal TI [3'
a2Ca6. @ E ro, the existence of 2 Cuz 07 was confirmed.

Moreover, FIG. 28 is a diagram showing temperature changes in magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 70°C.

Example 15 7. of mixed powder raw material The same procedure as in Example 13 was carried out, except that the ratio of p, Ba, Ca, Er, and Cu was 1:2:0.7:0.3:2 to prepare a mixed powder, and the firing temperature was 900°C. Samples were prepared under the following conditions.

As a result, an oxide superconductor with the following composition was synthesized: TI Ba2 Cao, y E ro, s Cu, and Or.

FIG. 29 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal Tjl Ba2
Cag, t E rr), s Cu2 o7 was confirmed.

Moreover, FIG. 30 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 80°C.

Example 16 TI, Ba, Ca, Tm, and Cu were mixed in an atomic ratio of 1 in the same manner as in Example 1 except that Y2O was replaced with Tm20m.
:2:0.9:0.1:2 mixed powder raw materials were prepared. This was molded and fired under the same conditions as in Example 8 to prepare a sample. As a result, TIBa2CaO,9Tmo,,Cu20
An oxide superconductor with a composition of t was synthesized.

FIG. 31 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal Tp Ba2
The presence of Can, q Tmo, 1 Cu20t was confirmed.

Moreover, FIG. 32 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 72°C.

Example 17 T, Ba, Ca, Yb, and Cu were mixed in an atomic ratio of 1:1 in the same manner as in Example 1 except that Y2O2 was replaced with Yb2O3.
A mixed powder raw material containing the powder at a ratio of 2:0.9:0.1:2 was prepared. This was molded and fired under the same conditions as in Example 8 to produce a sample. As a result, oxide superconductors having the compositions of TpBa2Cao, Ybo, and ICL207 were synthesized.

FIG. 33 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals a tetragonal T'j7. Ba
The presence of 2Cao9Ybo, +Cu20t was confirmed.

Moreover, FIG. 34 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 75°C.

Example 18 Y2O, Lu20. In the same manner as in Example 1 except that TJ7. A mixed powder raw material containing Ba, Ca, Lu, and Cu in an atomic ratio of 1:2:0.9:0, 1:2 was prepared. This was molded and fired under the same conditions as in Example 8 to prepare a sample. As a result, T(l B a 2 Cao9L uo, I CL12
An oxide superconductor with the composition 07 was synthesized.

FIG. 35 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal TI Ba2C
The presence of ao, e Luo, + Cu2O7 was confirmed.

Moreover, FIG. 36 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 77°C.

Example 19 Conditions were the same as in Example 18, except that a mixed powder was produced with the ratio of T, Ba, Ca, Lu, and Cu in the mixed powder raw materials being 1:2:0.8:0.2:2. A sample was prepared. As a result, Tl)Ba2Ca(1,s Luo,z Cu2O7
An oxide superconductor with the following composition was synthesized.

FIG. 37 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal TJ Ba2
The presence of C1o,aLuo,2Cu2O7 was confirmed.

Moreover, FIG. 38 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 80°C.

Example 20 A mixed powder was prepared by changing the ratio of Tf, Ba, Ca, Lu, and Cu of the mixed powder raw materials to 1:2:0.7:0.3:2, and the firing temperature was 890°C. A sample was prepared under the same conditions as in Example 13.

As a result, an oxide superconductor having the composition T(l Ba2Cao7L uo, 3 Cuz 07) was synthesized.

FIG. 39 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal TI Ba2
The presence of Cao, Luo, s Cuz 07 was confirmed.

Moreover, FIG. 40 is a diagram showing temperature changes in magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 80°C.

Example 21 Example 1 except that Y 203 was replaced with T b a 07
Similarly, T, Ba, Ca, Tb, and Cu were mixed in an atomic ratio of 1:2:0. A mixed powder raw material containing H at a ratio of 9:CI and 1:2 was prepared. This was molded and fired under the same conditions as in Example 8 to prepare a sample. As a result, an oxide superconductor having the composition Tjl Ba2 CaO, Tbo, + Cu207 was synthesized.

FIG. 41 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal Tll Baz
The presence of Ca(+,,Tbo,l(:u20v) was confirmed.

Moreover, FIG. 42 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 77°C.

Example 22 In the same manner as in Example 1 except that Y2O was replaced with G d 203, Tp, Ba, Ca, Gd, and Cu were mixed in an atomic ratio of 1:2:0.9:0.1:2. A mixed powder raw material containing the following proportions was prepared. This was molded and fired under the same conditions as Jitszetsuta 8 to prepare a sample. As a result, an oxide superconductor having the composition of Tp Ba2Cao, e Gdo, + CLJ207 was synthesized.

FIG. 43 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal TI Ba2
The presence of Cao, Gdo, t Cuz 07 was confirmed.

Moreover, FIG. 44 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 80°C.

Example 23 Mixed powder raw materials T, Ba, Ca, Gd, and Cu (7
) A sample was prepared under the same conditions as in Example 22, except that mixed powders were prepared at a ratio of 1:2:O, SO, 2:21: and the firing temperature was set at 900'C.

As a result, an oxide superconductor having the composition of TI Ba2Cao, aGdo, and 2Cu2O7 was synthesized.

FIG. 45 is a diagram showing the powder X-ray diffraction pattern of this sample. Due to the diffraction pattern, the tetragonal system TI B a2
Cao, +s G do, z The presence of CL1207 was confirmed.

Moreover, FIG. 46 is a diagram showing temperature changes in magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 70°C.

Example 24 Conditions were the same as in Example 23, except that a mixed powder was produced with the ratio of Tp, Ba, Ca, Gd, and Cu in the mixed powder raw materials being 1:2:0.7:0.3:2. A sample was prepared. As a result, an oxide superconductor having the composition Tl)Ba2Cao7Gdo, iCu20t was synthesized.

FIG. 47 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal T(l Ba2
The presence of Cao7Gdo and 3Cu207 was confirmed.

Moreover, FIG. 48 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 60°C.

Example 25 In the same manner as in Example 1 except that Y 20 s was replaced with Nd2O, T, Ba, Ca, Nd, and Cu were mixed in an atomic ratio of 1:2:0.9:0.1:2. A mixed powder raw material containing the following proportions was prepared. This was molded and fired under the same conditions as in Example 8 to produce a sample. As a result, TI B a2 Cao, s Ndo, I CL120
An oxide superconductor with a composition of 7 was synthesized.

FIG. 49 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern shows that the tetragonal Tl7Ba2
The presence of Cao, gNdo, and ICu207 was confirmed.

Moreover, FIG. 50 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 82°C.

Example 26 T p , B a + Ca + N of mixed powder raw material
A sample was prepared under the same conditions as Example 25, except that the ratio of d + and Cu was 1:2:o, 8:0.2:2, and the firing temperature was 890"C. did.

As a result, an oxide superconductor having a composition of TI Ba2 CaO, a Ndo, and 2Cu20t was synthesized.

FIG. 51 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal TI Ba2
The presence of Cao, aNdo, and 2Cu207 was confirmed.

Moreover, FIG. 52 is a diagram showing temperature changes in the magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 90°C.

Example 27 A mixed powder was prepared by changing the ratio of T, Ba, Ca, Nd, and Cu of the mixed powder raw materials to 1:2:0.7:0.3:2, and the firing temperature was 895°C. A sample was prepared under the same conditions as in Example 25.

As a result, Tl7 Ba2Ca, , Nd0. An oxide superconductor with a composition of , Cu2O, was synthesized.

FIG. 53 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern reveals that the tetragonal TJII B
The existence of a2Cao7Ndo, i Cuz 07 was confirmed.

Moreover, FIG. 54 is a diagram showing temperature changes in magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 90°C.

Example 28 Tj, Ba, Ca, Pr, and Cu were mixed in an atomic ratio of 1:2:0.9:0.1:2 in the same manner as in Example 1, except that Y2O2 was replaced with P r ,, O++. A mixed powder raw material containing the following ratio was prepared. This was molded and fired under the same conditions as in Example 8 to produce a sample. As a result, Tit B 82 Ca(+, g ProlCL12
An oxide superconductor with a composition of 07 was synthesized.

FIG. 55 is a diagram showing the powder X-ray diffraction pattern of this sample. The diffraction pattern shows that the tetragonal TI B a2
The presence of Cao,, P r o, + Cuz 07 was confirmed.

Moreover, FIG. 56 is a diagram showing temperature changes in magnetic susceptibility of this sample using the AC magnetic susceptibility method. From this figure, it was confirmed that the critical temperature of this sample was about 75°C.

Thus, the oxide superconductors synthesized in these examples are 7j7 Ba2CaCu20. It was confirmed that this material has a tetragonal crystal structure in which some of the Ca sites are substituted with rare earth elements, and a high critical temperature can be obtained.

Although Ba was used as the AE element in the above embodiments, an oxide superconductor with a high critical temperature can be obtained even if part or all of Ba is replaced with Sr. In addition, regarding the RE element, not only these but also other RE elements may be used as well.
An oxide superconductor with a tetragonal crystal structure in which some of the sites are substituted with rare earth elements can be obtained. For example, R
Even when La and Ce are used as the E source, oxide raw materials such as La2O5 and CeO2 can be used as starting materials in the same manner as in the above embodiments, and the same level as in the above embodiments can be used as in the above embodiments. It is possible to create a sample having a high critical temperature Tc.

Further, in the above embodiment, the case where m and n are 1 has been described, but the number of openings may be two or more, m may be 2, and n may be 1 or 2 or more. Such an oxide superconductor is produced by adding CuO and/or TR20i when preparing a mixed powder raw material so that the content ratio of each metal element becomes the desired composition ratio of the oxide superconductor. By doing so, it can be created in the same manner as in the above embodiment.

[Effect of the invention] According to this invention, T l) A E 2 Ca e Cu , ++ O
y or Tl)2 AE2 Can Cua++ O
It is possible to easily synthesize a completely new oxide superconductor having a tetragonal crystal structure in which a part of the Ca sites in y are replaced with an element represented by RE.

The oxide superconductor according to the present invention has a high critical temperature, a Josephson element having a Josephson junction, and a 5QUI
It is expected to be applied to DC superconducting quantum interferometers), superconducting power generators, and superconducting power storage with low energy loss, as well as the practical application of superconducting devices in various fields such as power transmission cables with low energy loss. It is expected that this will contribute.

[Brief explanation of drawings]

Figure 1, Figure 3, Figure 5, Figure 7, Figure 9, Figure 11,
Figure 13, Figure 15, Figure 17, Figure 19, Figure 21,
Figure 23, Figure 25, Figure 27, Figure 29, Figure 31,
Figure 33, Figure 35, Figure 37, Figure 39, Figure 41,
Figure 43, Figure 45, Figure 47, Figure 49, Figure 51,
53 and 55 are diagrams showing powder X-ray diffraction patterns of samples manufactured by the method according to the present invention; FIG. 2, FIG. 4, FIG. 6, FIG. 8, and FIG. , Fig. 12, Fig. 14, Fig. 16, Fig. 18, Fig. 20, Fig. 22, Fig. 24, Fig. 26, Fig. 28, Fig. 30, Fig. 32, Fig. 34, Fig. Figures 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, and 56 show the critical temperatures of these samples. FIG.

Claims (8)

[Claims] (1) General formula Tl_mAE_2(Ca_1_-_x, RE_x)_n
Cu_n_+_1O_y (However, AE is Ba and Sr
represents at least one element selected from S
Represents one or more elements selected from c, Y, and lanthanoids, x is within the range of 0<x<1, m is 1 or 2, n is an integer of 1 or more, and y is An oxide superconductor characterized in that the number is sufficient to satisfy valence requirements. (2) Tl_mAE_2Ca_nCu_n_+_1O_
The oxide superconductor according to claim 1, which has a tetragonal crystal structure in which a part of the Ca sites in y are substituted with an element represented by RE. (3) The AE is Ba, the RE is Y, and x is 0<
The oxide superconductor according to claim 1 or 2, wherein x is within the range of x<0.5. (4) General formula TlBa_2Ca_1-_xY_xCu_
2O_y (where x is within the range of 0<x<0.5, and y is a sufficient number to satisfy the valence requirement). The oxide superconductor described. (5) A step of preparing a raw material containing Tl, AE, Ca, RE and Cu in an atomic ratio of substantially m:2:n(1-x):nx:(n+1); represents Ba or Sr, RE represents one or more elements selected from Sc, Y, and lanthanoids, and x represents 0<x<
1, m is 1 or 2, and n is an integer of 1 or more), and firing the mixture in an oxygen-containing atmosphere. Method. (6) Production of the oxide superconductor according to claim 5, wherein AE in the raw material is Ba, RE is Y, and x is within the range of 0<x<0.5. Method. (7) The raw material contains Tl, AE, Ca, RE, and Cu in an atomic ratio of substantially 1:2:(1-x):x:2 (where x is 0<x<0.5) ) The method for producing an oxide superconductor according to claim 5, wherein the oxide superconductor is contained in a proportion of: (8) The method for producing an oxide superconductor according to any one of claims 5 to 7, wherein the firing step is performed at a temperature within a range of 800 to 950°C.