JPH05124816A - Oxide superconductor, multi component oxide superconducting material and its production - Google Patents

Abstract

PURPOSE:To provide the novel oxide superconductor and multiple oxide superconducting material which can be synthesized under a low oxygen partial pressure and the process for production thereof. CONSTITUTION:This oxide superconductor is expressed by chemical formula Pb2Ba3-x-yCaxLnyCu3O8+ or -z. This Ln is at least one kind of lanthanoid and Y and the range of (x), (y), (z) is 0<x<=1.2, 0.3<=y<=1, 0<=z<=1. The process for production of the oxide superconductor consists in weighing Pb, Ba, Ca, Ln (one kind of lanthanoid and Y), oxide or carbonate of Cu at prescribed molar ratios and mixing and molding these materials, then calcining the mixture at 600 to 800 deg.C, pulverizing and molding the calcined mixture and subjecting the molding to normal calcination at 650 to 800 deg.C and under the low oxygen partial pressure (<=0.01atm.).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide superconductor, a composite oxide superconducting material and a method for producing the same, and particularly to an oxidation applicable to all fields such as energy-related technology and electronic technology utilizing the superconducting phenomenon. And a method for producing the same.

[0002]

Many oxide superconductors have been invented since (La, Sr) ₂ CuO ₄ was discovered as the first high temperature oxide superconductor in 1986. In 1987, the evaporation temperature of liquid nitrogen, which was relatively easy to handle as a refrigerant, was 77K.
Yba ₂ Cu ₃ with superconducting transition temperature (Tc) above
O ₇ was invented and expanded the range of practical use. And the highest Tc at the moment is Tl ₂ Ba ₂ Ca ₂ Cu ₃ O ₁₀ T
c (zero) is set to 127K. By the way, all of the above oxide superconductors need to be synthesized (heat treatment) in an oxidizing atmosphere, and to be used in combination with metals and semiconductors, there are restrictions on the metal / semiconductor material, and sufficient heat treatment is required. However, there is a problem that an oxide superconductor with incomplete characteristics will be formed. Therefore, the invention of an oxide superconductor that can be synthesized under low oxygen partial pressure is desired. To date, Pb ₂ Sr ₂ Ln _1-x Ca _x Cu ₃ has the highest Tc as an oxide superconductor that can be synthesized under low oxygen partial pressure.
O ₈ ± _y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and the Tc thereof is 80K or less according to many reports.

[0003]

As described above, Pb ₂ Sr ₂ Ln _1-x C has the highest characteristics (Tc) among conventional oxide superconductors that can be synthesized under low oxygen partial pressure.
a _x Cu ₃ O ₈ ± _y and Tc (onset) is 84K (reference: J.S. Xue et al .: Phys)
ica C 166 (1990) 29. ), But most are below 80K. Generally, higher Tc is more practically advantageous, and the invention of a superconductor having higher Tc is desired. In addition, a lower synthesis temperature is more advantageous in terms of production energy cost, and in the case of a substance containing an element (or compound) that evaporates at a relatively low temperature such as Pb, composition control is easy. Also desirable from the point.

An object of the present invention is to provide a new oxide superconductor, a composite oxide superconducting material which can be synthesized under a low oxygen partial pressure and a method for producing the same.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0006]

In order to achieve the above object, the invention of claim 1 provides a chemical composition formula Pb ₂ Ba _3-xy Ca.
an oxide superconductor represented by _{x Ln y Cu 3 O 8 ±} z, wherein Ln is at least one of the lanthanides and Y, x, y, z range is 0 <x ≦ 1.2, 0 .3
It is characterized in that ≦ y ≦ 1 and 0 ≦ z ≦ 1.

A second aspect of the present invention is a composite oxide superconducting material mainly comprising the oxide superconductor according to the first aspect.

The invention of claim 3 is the method for producing an oxide superconductor according to claim 1, wherein Pb, Ba, Ca, Ln (one of lanthanoid and Y), Cu oxide or carbonate is predetermined. 600-8 by weighing, mixing and molding to the molar ratio
650 after calcination at 00 ° C, then crushing and molding
It is characterized in that the main calcination is carried out at ˜800 ° C. and under a low oxygen partial pressure (0.01 atm or less).

A fourth aspect of the present invention is the method for producing an oxide superconductor according to the first aspect, wherein Pb, Ba, Ca, Ln (one of lanthanoid and Y), Cu oxide or carbonate is predetermined. 600-8 by weighing, mixing and molding to the molar ratio
650 after calcination at 00 ° C, then crushing and molding
〜800 ° C, main calcination under low oxygen partial pressure (0.01 atm or less), pulverization and molding again, and main calcination again at 650-800 ° C, low oxygen partial pressure (0.01 atm or less), ,
An annealing treatment is performed at 300 to 550 ° C. under a low oxygen partial pressure.

A fifth aspect of the present invention is a method for producing a complex oxide superconducting material mainly comprising the oxide superconductor according to the first aspect, wherein Pb, Ba, Ca, Ln (one of lanthanoid and Y), Cu oxide or carbonate, a composite material are weighed, mixed and molded in a predetermined molar ratio, calcined at 600 to 800 ° C., then crushed and molded, and then 650 to 800.
C., main calcination under a low oxygen partial pressure, and if necessary, crush and mold again after the main calcination, 650-800.degree. C., main calcination again under a low oxygen partial pressure, and further 300-550.degree. C., low It is characterized in that the annealing treatment is performed under an oxygen partial pressure.

[0011]

According to the above-mentioned means, the chemical formula Pb ₂ Ba _3-xy C is used.
a _x Ln _y Cu ₃ O ₈ complex oxide superconducting material to the oxide superconductor or a main component thereof is expressed by ± _z is 65
Synthesis is possible at a low temperature of 0 to 800 ° C. (under low oxygen partial pressure = 0.01 atm or less), and this temperature range is Pb ₂ Sr ₂
In the case of Ln _1-x Ca _x Cu ₃ O _y , 850 to 950 ° C.
(In an oxygen atmosphere of 01 atm)). Also, Tc (onset) is 86K and Pb ₂ Sr ₂ Y _1-x C
It is equal to or higher than that of a _x Cu ₃ O _y .

Then, the range of x and y is set to 0 <x ≦ 1.
2. The reason for setting 0.3 ≦ y ≦ 1 is that if it deviates from this range, the superconducting property is deteriorated, or the superconducting property is lost. In particular, y is less than 0.3 (y <
0.3) and y is greater than 1 (1 <y),
Lanthanoid ion Ln ³⁺ (or yttrium ion Y
³⁺ ) and barium ion Ba ²⁺ and calcium ion Ca
^It is considered that the overall balance of the valence with ²⁺ becomes unbalanced and an appropriate superconducting carrier concentration cannot be obtained.

The temperatures of the calcination, the main calcination and the annealing treatment are 600 to 800 ° C., 650 to 800 ° C. and 3 respectively.
The reason for limiting the temperature to 00 to 550 ° C. is as follows.

In the case of calcination, the reaction does not proceed sufficiently if the calcination temperature is lower than 600 ° C. Further, at a temperature exceeding 800 ° C., a stable phase is formed at a relatively high temperature, which hinders the formation of the superconductor phase of the composition of the present invention during the main firing.
In the case of the main firing, at a temperature lower than 650 ° C., the superconductor phase of the composition of the present invention cannot be sufficiently generated. Also, 8
By firing at a temperature above 00 ° C., the superconductor phase of the composition of the present invention once formed is decomposed. In the case of annealing treatment, in the temperature range below 300 ° C and above 550 ° C,
An appropriate equilibrium oxygen partial pressure cannot be obtained in the relationship between the sample and the firing atmosphere, and the oxygen content of the sample cannot be controlled to an appropriate amount.

In this way, new oxide superconductors and composite oxide superconducting materials can be synthesized under low oxygen partial pressure.

[0016]

EXAMPLES Examples of the present invention will be described below. Example 1 Lead oxide PbO (or PbO ₂ ), barium carbonate BaCO ₃ (or barium oxide BaO), calcium carbonate CaCO ₃ , yttrium oxide Y ₂ O ₃ (or lanthanoid oxide), copper oxide CuO (or CuO). ₂ ) in a molar ratio of Pb: Ba: Ca: Y: Cu = 2.0: 2.0:
Weighed to be 0.5: 0.5: 3.0 and mixed well. After molding at a pressure of about 1 ton / cm ² , calcination was performed at 700 ° C. in the air (or in an argon gas flow) for 10 hours. Next, after crushing and molding again at a pressure of about ² ton / cm ² , main firing was performed at 740 ° C. in an argon gas flow for 10 hours. Next, annealing treatment was performed at 400 ° C. for 20 hours in an argon gas flow. When the composition analysis of this sintered sample was performed, it was found that the composition of the entire sample was P
b: Ba: Ca: Y: Cu = 1.9: 2.0: 0.5: 0.
It was 5: 3.0 (molar ratio).

The characteristics of the sample of Example 1 are shown in FIGS. FIG. 1 is a resistance-temperature characteristic diagram. The Tc (onset) of the sample obtained from this is 82K and the Tc (zero) is 72K.
It was K. Further, FIG. 2 shows the result of the DC susceptibility measurement, and the Tc obtained from this was 81K.

The composition of the sample of Example 1 Pb, Ba, C
The results obtained by changing the molar ratio of a, Y and Cu are shown in Table 1A,
1B, 1C, and 1D, which are shown in a composition diagram as shown in FIG. In FIG. 3, a frame (a) is a superconducting region, a ● symbol indicates superconductivity at 80K to 86K, a Δ symbol indicates superconductivity at 70K to 79K, and a □ symbol indicates 60K. ~ 69K indicates superconductivity, and x indicates no superconductivity.

[0019]

[Table 1A]

[0020]

[Table 1B]

[0021]

[Table 1C]

[0022]

[Table 1D]

In Tables 1A, 1B, 1C and 1D, Tc
When (K) is 80, it means that it shows superconductivity at 80K to 86K, when it is 70, it means that it shows superconductivity at 70K to above 79K, and when it is 60, it shows superconductivity at 60K to above 69K. It means that. The cross mark indicates that superconductivity is not exhibited.

Example 2 The same raw material as in Example 1 was used, and in order to compensate for the scattering of Pb during firing, Pb was present in excess of the desired composition (Pb: Ba: Ca: Y: in molar ratio). C
u = 2.4: 2.0: 0.3: 0.7: 3.0) and mixed well. After molding at a pressure of about 1 ton / cm ² , calcination was performed at 700 ° C. in the air (or in an argon gas flow) for 10 hours. Then crush it to about 2
After molding again at a pressure of ton / cm ² , main firing was performed at 740 ° C. in an argon gas flow for 10 hours. Furthermore, crushing and molding are performed, and at 740 ° C. in an argon gas flow, 1
Firing was performed for 0 hours. Next, annealing treatment was performed at 400 ° C. for 20 hours in an argon gas flow. When the composition of this sintered sample was analyzed, it was found that the composition of the entire sample was Pb: Ba: Ca: Y: Cu = 2.0: 2.0: 0.
It was 3: 0.7: 3.0 (molar ratio). In addition, as a result of X-ray diffraction measurement, it was found that almost a single phase was obtained.

As in the case of Example 1, the results of resistance-temperature characteristic test and DC susceptibility measurement are shown in Tables 1A, 1B, 1C,
Superconducting properties similar to 1D were obtained.

Example 3 Using the same raw material as in Example 1, the molar ratio of Pb: Ba: Ca: Y: Cu = 2.0:
Weighed to be 1.5: 1.0: 0.5: 3.0 and mixed well. After molding at a pressure of about 1 ton / cm ² , 700
Calcination was carried out for 10 hours in the atmosphere (or in an argon gas flow) at 0 ° C. Next, after crushing and molding again at a pressure of about ² ton / cm ² , at 720 ° C. in an argon gas flow, 1
The main firing was performed for 0 hours. Next, annealing treatment was performed at 400 ° C. for 20 hours in an argon gas flow. When the composition of this sintered sample was analyzed, the composition of the entire sample was Pb: Ba: Ca: Y: Cu = 1.9: 1.5: 1.
It was 0: 0.5: 3.0 (molar ratio).

FIG. 4 shows the resistance-temperature characteristic of the sample of the third embodiment.
Shown in. The Tc (onset) obtained from this was 86K.

Example 4 Lead oxide PbO (or Pb
O ₂ ), barium carbonate BaCO ₃ (or barium oxide Ba
O), calcium carbonate CaCO ₃ , yttrium oxide Y ₂
O ₃ (or lanthanoid oxide), copper oxide CuO (or CuO ₂ ) and silver oxide AgO (or Ag ₂ O, or silver Ag) in a molar ratio of Pb: Ba: Ca: Y: Cu: Ag =
Weighed so as to be 2.0: 2.0: 0.5: 0.5: 3.0: 0.5 and mixed well. After molding at a pressure of about 1 ton / cm ² , calcination was performed at 700 ° C. in the air (or in an argon gas flow) for 10 hours. Next, crush, about 2 to
After molding again at a pressure of n / cm ² , firing was carried out at 740 ° C. in an argon gas flow for 10 hours. Next, an annealing treatment was performed for 20 hours in a 400 ° C. argon gas flow.

The resistance-temperature characteristics of the sample of this example are shown in FIG. The resistivity was smaller than that when Ag was not added (Example 1).

The novel oxide superconductor and composite oxide superconducting material of the present invention can be applied to energy-related technology and electronic technology utilizing the superconducting phenomenon.

Although the present invention has been specifically described based on the embodiments, it is needless to say that the present invention is not limited to the above embodiments and various modifications can be made without departing from the scope of the invention. Absent.

[0032]

As described above, according to the present invention, new oxide superconductors and composite oxide superconducting materials can be synthesized under a low oxygen partial pressure.

[Brief description of drawings]

FIG. 1 is a diagram showing resistance-temperature characteristics of a sample of Example 1 of the present invention,

FIG. 2 is a diagram showing the results of DC susceptibility measurement of the sample of Example 1 of the present invention,

FIG. 3 is a table 1A, 1B, 1C, 1 of the first embodiment of the present invention.
A diagram showing the composition of the sample shown in D,

FIG. 4 is a graph showing resistance-temperature characteristics of a sample of Example 3 of the present invention,

FIG. 5 is a diagram showing resistance-temperature characteristics of a sample of Example 4 of the present invention.

[Explanation of symbols]

●: Superconductivity is shown at 80K to 86K, Δ: Superconductivity is shown at 70K to upper 79K, □: Superconductivity is shown at 60K to upper 69K, × ... Superconductivity is not shown.

Front page continuation (72) Inventor Takaaki Ikemachi 1-14-3 Shinonome, Koto-ku, Tokyo Inside the Superconducting Engineering Research Center, International Superconductivity Technology Center (72) Inventor Shinichi Koriyama 1-14, Shinonome, Koto-ku, Tokyo No. 3 International Superconducting Industrial Technology Research Center, Superconducting Engineering Laboratory (72) Inventor Nao Yamauchi 1-14-3 Shinonome, Koto-ku, Tokyo Inside Superconducting Engineering Research Institute, International Superconducting Industrial Technology Center

Claims (5)

[Claims] 1. The chemical formula Pb ₂ Ba _3-xy Ca _x Ln _y Cu ₃
An oxide superconductor represented by O ₈ ± _z , wherein Ln
Is at least one of lanthanoid and Y,
The range of x, y, z is 0 <x ≦ 1.2, 0.3 ≦ y ≦ 1,
An oxide superconductor characterized in that 0 ≦ z ≦ 1. 2. A composite oxide superconducting material mainly comprising the oxide superconductor according to claim 1. 3. The chemical formula Pb ₂ Ba _3-xy Ca _x Ln _y Cu ₃
Is represented by O ₈ ± _z , and Ln is at least one of lanthanoid and Y, and the range of x, y, z is 0 <x ≦
1.2, 0.3 ≦ y ≦ 1, 0 ≦ z ≦ 1, a method for manufacturing an oxide superconductor, comprising Pb, Ba, Ca, Ln (one of lanthanoid and Y), and Cu oxide Alternatively, a carbonate is weighed, mixed and molded in a predetermined molar ratio to obtain 600 to 8
650 after calcination at 00 ° C, then crushing and molding
~ 800 ° C under low oxygen partial pressure (0.01 atm or less), main calcination, if necessary, crushing and molding again, and 650 ~ 800 ° C under low oxygen partial pressure (0.01 atm or less) again main baking. A method for producing a featured oxide superconductor. 4. The chemical formula Pb ₂ Ba _3-xy Ca _x Ln _y Cu ₃
Is represented by O ₈ ± _z , and Ln is at least one of lanthanoid and Y, and the range of x, y, z is 0 <x ≦
1.2, 0.3 ≦ y ≦ 1, 0 ≦ z ≦ 1, a method for manufacturing an oxide superconductor, comprising Pb, Ba, Ca, Ln (one of lanthanoid and Y), and Cu oxide Alternatively, a carbonate is weighed, mixed and molded in a predetermined molar ratio to obtain 600 to 8
650 after calcination at 00 ° C, then crushing and molding
~ 800 ℃ under low oxygen partial pressure (0.01 atm or less) main firing, if necessary, crush and shape again, 650 ~ 800 ℃ under low oxygen partial pressure (0.01 atm or less) again main firing, A method for producing an oxide superconductor, which comprises performing an annealing treatment at 300 to 550 ° C. under a low oxygen partial pressure. 5. The chemical formula Pb ₂ Ba _3-xy Ca _x Ln _y Cu ₃
Is represented by O ₈ ± _z , and Ln is at least one of lanthanoid and Y, and the range of x, y, z is 0 <x ≦
1.2, 0.3 ≦ y ≦ 1, 0 ≦ z ≦ 1, a method for manufacturing an oxide superconductor, comprising Pb, Ba, Ca, Ln (one of lanthanoid and Y), and Cu oxide Alternatively, carbonates and complex substances are weighed, mixed and molded in a predetermined molar ratio,
Preliminarily calcined at 600 to 800 ° C., then crushed and molded, then calcinated at 650 to 800 ° C. under low oxygen partial pressure, and if necessary, crushed and molded again at 650 to 850
Main firing again at 800 ° C under low oxygen partial pressure, and further 30
A method for producing an oxide superconductor, which comprises performing an annealing treatment at 0 to 550 ° C. under a low oxygen partial pressure.