JPH10194744A - Oxide superconductor and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an oxide superconductor excellent in superconducting characteristics, moldable in a short baking time and to provide a method for producing the oxide superconductor. SOLUTION: An oxide superconductor is produced by using a raw material having the same composition as that in which a part of Bi or a part of both Bi and Pb contained in a Bi-2223 phase consisting essentially of Bi-Pb-Sr-Ca-Cu is substituted with V. A material obtained by adding V to a material having the same composition as that of the Bi-2223 phase consisting essentially of Bi-Pb-Sr-Ca-Cu is used as a raw material to produce an oxide superconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a Bi-Pb-Sr
The present invention relates to a -Ca-Cu-O-based oxide superconductor and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Problems to be Solved by Bi
The -Sr-Ca-Cu into oxide superconductor mainly _{is, Bi 2 Sr 2 Ca 2 Cu} 3 O z (z is a number close to 10) superconducting phase represented by the (Bi-2223 phase) Bi
_{2 Sr 2 Ca 1 Cu 2 O} y (y is a number close to 8) Two superconducting phases of the superconducting phase represented by (Bi-2212 phase) is present. Among them, for the Bi-2223 phase,
It has a high critical temperature and a high critical current density, and is considered to be the most suitable as a material for a superconducting wire among many oxide superconductors.

When producing an oxide superconductor containing a superconducting phase called Bi-2223 phase, a small amount of Pb (lead) is replaced with Bi (bismuth) in order to obtain a high-purity material, and (Bi, Pb) ) material composition as _{2 Sr 2 Ca 2 Cu 3 O} z is synthesized. The effect of substituting Pb in this way is considered to make the Bi-2223 phase exist stably. However, even for a material in which Pb is substituted, firing for a very long time (100 hours or more) is required to increase the purity.

Heretofore, attempts have been made to introduce various elements other than Pb for the purpose of stabilizing the phase or improving the superconducting characteristics, but none of them has been particularly effective. Some experiments have been attempted on V (vanadium) among such elements. References describing the above are listed below.

(1) PCWFung et al., “VANADIUM SUB
STITUTED 2212 AND 2223 SUPERCONDUCTING CERAMICS
”, Solid State Communications, Vol.75, NO.3, 199
0, pp.211-216 (2) B. Chanda et al., “Heat conduction in vanadiu
m substitute (Bi _0.8 Pb _0.2-y V _y ) ₂ Sr ₂ Ca ₂ Cu ₃ O _X s
intered pellets between 10 and 150K ”, Cryogenics 1
993 Vol.33, No10, pp.980-985 (3) B. Chanda et al., “Normal state thermoelectri
c power of vanadium-substituted (Bi _0.8 Pb
_0.2-y V _y ) ₂ Sr ₂ Ca ₂ Cu ₃ O _X superconducting pellets
Physica C 232 (1994), pp.136-144 (4) NV Minh et al., “EFECTS OF VANADIUM ON THE
SUPERCONDUCTING PROPERTIES OF Bi-Pb-Sr-Ca-Cu-O SYS
TEM ", Physica C 235-240 (1994), pp. 1435-1436 (5) G. Narsinga Rao et al.," LEMA and Irreversibil
ity Line Studies onVanadium Doped Bi (2223) superco
nducting system ”, Physica C 235-240 (1994), pp.
2031-2033 (6) B. Chanda et al., “Mixed State Thermoeledtric
Power of Vanadium Substituted 2223 (Bi, Pb) Superc
onducting Polycrystalline Cuprates ”, Journal of S
uperconductivity, Vol.9, No.2, 1996, pp.181-185 (7) Youmo Li et al., “Comparative Study on the D
oping Effect of 3d Elements in Bi _1.5 Pb _0.2 Sr ₂ Ca
₂ Cu _2.8 M _0.2 O _y (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni,
or Zn), Journal of Superconductivity, Vol. 9, No.
3, 1996, pp.201-203 (8) MEYakinci et al., "Synthesis of melt-quench
ed Bi _1.7 V _0.3 Sr ₂ Ca ₂ Cu ₃ O _{10 + y} superconducting gla
ss-ceramics ”, JOURNAL OF MATERIALS SCIENCE 31 (1
996), pp.2865-2871 However, in these documents, no particular effect has been observed because the addition or substitution of the V element is inappropriate.

For example, references (1), (5) and
(8) contains (Bi_2-xV_x) Sr _TwoCa_TwoCu_ThreeO_z
Replaces V with Bi instead of Pb without including Pb as in
Material is synthesized, but the critical temperature is also (Bi,
Pb)_TwoSr_TwoCa_TwoCu_ThreeO_zNot high and low compared to
It becomes a mixed sample with the Bi-2212 phase at the critical temperature.

References (2), (3) and (6)
Contains (Bi_0.8Pb_0.2-xV_x) _TwoSr_TwoCa_TwoCu
_ThreeO_zA sample in which V is replaced with a part of Pb as in
Have been. However, the superconducting properties shown here are
An adverse effect such that the critical temperature decreases with an increase in the amount of V
Can be seen. Further, the firing time of the sample is 100 hours at 840 ° C.
If you spend more time (from reference (2))
Has not been able to obtain a single-phase Bi-2223 phase
(See FIG. 1 in Reference (2): Bi-2212 phase)
Peak is visible).

References (4) and (7) also state that
(Bi, Pb) materials to replace the Cu (copper) as _{2 Sr 2 Ca 2 Cu 3- x} V X O z have been synthesized.
In these cases, the critical temperature has the same performance as the sample without V addition, but it is considered that a very long baking time is required to obtain such characteristics (Reference (4): 170 hours) , Reference (7): 150 hours).

In addition, an application filed by a part of the inventor of the present application (JP-A-6-316417) discloses a method of adding Sr-VO to form a single phase. 100 to obtain the Bi-2223 phase
A firing time of at least one hour is required.

As described above, Pb-substituted Bi-22
The 23 phase is a material suitable for a superconducting wire using a silver coating method or the like, and has very high characteristics, but the length of the firing time significantly reduces productivity.

It is therefore an object of the present invention to provide an oxide superconductor having excellent superconducting properties which can be formed in a short firing time, and a method for producing the same.

[0012]

Means for Solving the Problems The present inventors have proposed (B
A sample was synthesized by substituting or adding various elements to i, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _z by various methods, and a sample was synthesized.
As a result, they found a new method of introducing V element and succeeded in greatly reducing the firing time by the method.

The method of manufacturing the oxide superconductor of the present invention to which the newly discovered method of introducing V element is applied is as follows.

According to one embodiment of the present invention, there is provided a method for manufacturing an oxide superconductor, comprising the steps of: replacing a part of Bi contained in a Bi-2223 phase containing Bi-Pb-Sr-Ca-Cu as a main component with V; The production is performed using a raw material having the same composition ratio as in the above.

In the method described in the aforementioned reference, P
This is a method in which all of b is replaced with V or only a part of Pb is replaced with V. Such a replacement method has no effect on shortening the firing time. On the other hand, when Bi alone or a part of both Bi and Pb is replaced with V as in the present invention, the firing time can be greatly reduced, and the productivity can be significantly improved.

Here, the Bi-2223 phase usually indicates a composition of (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _Z , but generally, Bi _1.8 Pb _0.4 Sr _2.0 Ca _2.2
It is used as the Cu _{3. 0} O _Z composition.

Further, according to another aspect of the present invention, there is provided a method of manufacturing an oxide superconductor, wherein V is added to a material having the same composition ratio as a Bi-2223 phase containing Bi-Pb-Sr-Ca-Cu as a main component. This is a method of producing using the added material as a raw material.

For example, the composition of the target superconducting phase (the superconducting phase composition of the final product) is Bi _1.8 Pb _0.4 Sr _2.0 C
When a _2.2 Cu ₃ O _z (z is a number close to 10), the element ratio of the starting material is set to Bi _1.8 Pb _0.4 Sr _2.0 Ca _2.2
Bi, Pb, S like Cu ₃ O _z + V _u (u is a ratio)
r, Ca, and Cu are the same as the target composition, and V
This is a method of adding an element.

In the above-mentioned references, the ratio of a certain element is reduced by the V substitution amount, but such a substitution method has no effect on shortening the firing time. On the other hand, the starting material having the same element ratio as the target composition as in the present invention has V
When is added, the firing time is greatly reduced, and the productivity can be significantly improved.

As described above, by replacing the V element with a specific element or by adding V further, it has a critical temperature of about 110 K and contains Bi-Pb-Sr-Ca-Cu as a main component. Bi-2
The calcination time of the 223 phase can be reduced to about half of the conventional time.

In addition, such a method of introducing the V element can disperse the V element or the V compound in the superconducting material without lowering the superconducting characteristics, particularly the critical temperature.

The inventors of the present application have added, in addition to this V element,
It has also been found that when B (boron) is further added, the effect of shortening the firing time is further promoted.

The amount of B added is 0.1 mol or more and 0.2 mol per 1 mol of a raw material having a predetermined composition ratio.
It is desirable to add 1 or less. 0.1 m of B
The reason for setting the sintering time to less than 0.1 mol is that the effect of shortening the firing time is not sufficient if the amount is less than 0.1 mol.
This is because if added in excess of the above, the superconducting properties deteriorate.

The element V is desirably added in an amount of 0.1 mol or more and 0.3 mol or less per 1 mol of a raw material having a predetermined composition ratio. The reason why the addition amount of V is 0.1 mol or more and 0.3 mol or less is that if it is less than 0.1 mol, the effect of shortening the sintering time is not sufficient, and if it exceeds 0.3 mol, the superconducting properties deteriorate.

The oxide superconductor of the present invention formed by the above two aspects has a Bi-2223 phase mainly composed of Bi-Pb-Sr-Ca-Cu,
A feature is that a part of Bi contained in the phase is replaced with V.

Further, not only a part of Bi but also a part of Pb may be substituted with V. Further, B may be further added.

It is desirable that the element ratio between Bi and V contained in the Bi-2223 phase is 0.05 <V / (Bi + V) <0.22. If the element ratio between Bi and V is 0.05 or less, the effect of shortening the firing time is not sufficient,
If it is 0 or more, the superconducting properties deteriorate.

Bi and P contained in Bi-2223 phase
The element ratio between b and V is 0.04 <V / (Bi + Pb + V)
<0.20 is desirable. This Bi, Pb and V
If the element ratio is 0.04 or less, the effect of shortening the firing time is not sufficient, and if it is 0.20 or more, the superconducting properties are deteriorated.

[0029]

The method and results of experiments conducted by the present inventors will be described below.

Bi ₂ O ₃ , PbO, Sr
Using CO ₃ , CaCO ₃ , CuO, V ₂ O ₅ , and B ₂ O ₃ , the basic composition ratio was set to Bi _1.8 Pb _0.4 Sr _2.0 Ca _2.2 C
and examines each element substitution and addition effect of V elements for this composition as u _{3. 0} O _y. The sample was mixed by changing only the composition, and heat-treated in air at 780 ° C. × 8 hours, pulverized, 785
Heat treatment at 8 ° C. × 8 hours, pulverization, heat treatment at 790 ° C. × 8 hours, and pulverization were performed in this order. At this stage, the Bi-2223 phase was not contained in any sample of any composition, and only the Bi-2212 phase having a low critical temperature was contained. The treated powder was pelletized by a press machine, and the heat treatment time was changed at 838 ° C. in the atmosphere to change Bi-2 in the sample.
The amount of 223 phase formed was adjusted.

The proportion of each phase was determined by the diffraction peak (115) line (2θ = 2 in the Bi-2223 phase) obtained from the powder X-ray diffraction (using Cu-Kα ray as the X-ray) pattern.
6.2 °, which appears at 2θ = 27.5 ° in the Bi-2212 phase).

The sample Bi _1.8 into which V and B are not introduced
The _{Pb 0.4 Sr 2.0 Ca 2.2 Cu 3.0} O y and Comparative Example 1.

Example 1 Composition (Bi _1.8-x V _x ) Pb _0.4 Sr _2.0 Ca _2.2 Cu in which Bi element is partially substituted with V with respect to the above basic composition
_3.0 O _y (x = 0.1, 0.2, 0.3, 0.4, 0.
The powder having 5) was mixed, and a sample was prepared in the above process. FIG. 1 shows the relationship between the firing time of these samples at 838 ° C. in the air and the ratio of the Bi-2223 phase contained in the samples.
Shown in

As can be seen from FIG. 1, in Comparative Example 1 (composition not containing V), the ratio of the Bi-2223 phase still contained in the sample after sintering for 150 hours was 50%, whereas V Was replaced with Bi, Bi-222
It can be seen that the ratio of the three phases increases in a short time. It can also be seen that the generation rate is accelerated as the substitution amount increases.

Table 1 below shows the relationship between the V substitution amount and the critical temperature at a firing time of 150 hours (hours). Thereby, the sintering time can be reduced, and the critical temperature can be set to a value equivalent to that of the comparative example.
+ V) is desirably about 0.05 or more and about 0.2 or less.

[0036]

[Table 1]

Example 2 A composition (Bi _1.8-x V _x ) (Pb _0.4-z V) in which both of the Bi and Pb elements were partially replaced with V with respect to the above basic composition.
In _{z) Sr 2.0 Ca 2.2 Cu 3.0} O y, x = 0.082 as a combination of x and z, and z = 0.018,
x = 0.164, z = 0.036, x = 0.245,
z = 0.555, x = 0.327, z = 0.073
And five kinds of powders having x = 0.409 and z = 0.091 were mixed, and the formation ratio of the Bi-2223 phase at 838 ° C. in the atmosphere was examined in the same manner as in Example 1. Figure 2 shows the result.
Shown in

As can be seen from FIG. 2, even in this substitution pattern, Bi-
It can be seen that the formation of the 2223 phase is greatly promoted.

Table 2 below shows the relationship between the V substitution amount and the critical temperature at a firing time of 100 hours. Thereby, the sintering time can be shortened, and the critical temperature can be set to the same value as the comparative example. The substitution amount of V is V / (Bi + Pb +
It can be said that V) is desirably about 0.04 or more and about 0.2 or less.

[0040]

[Table 2]

[0041] For the basic composition of the comparative example described above, the composition by replacing part of Pb element in _{V Bi 1.8 (Pb 0. 4-} z V z) Sr 2.0 Ca 2.2 Cu
A powder having _3.0 O _y (z = 0.1, 0.25, 0.3) is mixed, and Bi-222 at 838 ° C. in the atmosphere is also mixed.
The formation ratio of three phases was examined. The result is shown in FIG.

As can be seen from FIG. 3, in this substitution pattern, the formation of the Bi-2223 phase is suppressed as the V amount increases. This allows P
It can be said that substituting only b with V has an adverse effect on the effect of shortening the firing time. Therefore, a composition that does not contain Pb, or a composition that reduces Pb and replaces V instead of Pb, as shown in the above-mentioned references, may not be appropriate for shortening the firing time. Recognize.

[0043] Example 3 while maintaining the ratio to each element of the above-described basic composition, extra composition plus V element Bi _1.8 Pb _0.4 Sr _2.0 Ca _2.2
Cu _3.0 O _y + V _x (x = 0.1, 0.2, 0.3,
0.4), and mixed in the same manner as above.
The formation ratio of the Bi-2223 phase at 8 ° C. was examined. FIG. 4 shows the results.

As can be seen from FIG. 4, in the composition to which V is added extra, the formation of the Bi-2223 phase is greatly promoted. For example, in the case of adding x = 0.2, the reaction takes about 70 hours. It can be seen that the firing is completed and the required firing time is shortened.

Table 3 below shows the relationship between the V substitution amount and the critical temperature at a firing time of 100 hours. Thereby, the amount of V that can reduce the firing time and make the critical temperature equivalent to that of the comparative example is 1 mol of the superconducting composition.
0.1 mol or more and 0.3 mol or less (the above x =
0.1 to 0.3).

[0046]

[Table 3]

[0047]Example 4 Composition with only B added to the above basic composition (Comparative Example
Becomes: Bi_1.8Pb _0.4Sr_2.0Ca_2.2Cu_3.0O
_y+ B_0.1) And a composition (Bi_1.8
Pb_0.4Sr_2.0Ca_2.2Cu_3.0O_y+ V_z+
B_0.1, Z = 0.1, 0.2), and mix
An experiment was performed. FIG. 5 shows the result.

As can be seen from FIG. 5, in the sample to which only B was first added, there was almost no change as compared with the basic composition sample (Comparative Example 1). On the other hand, in the sample to which V and B were added at the same time, it can be seen that the required baking time was shorter than that in Comparative Example 1 or the sample to which only V was added. It can be said that the simultaneous addition of B in addition to V further promotes the formation of the Bi-2223 phase.

Also, Bi _1.8 Pb _0.4 Sr _2.0 Ca _2.2 C
u _3.0 O _y + V _0.2 + B _w and V amount are fixed, and the amount of B is w
= 0.1, 0.2, 0.3, w = 0.
The samples of 1 and 0.2 show a critical temperature of 107 K at a firing time of 100 hours, but when w = 0.3, the temperature becomes about 100 K. It can be said that it is below.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0051]

As described above, according to the method of introducing the V element or the B element shown in the present invention, Bi-Pb-Sr-
The firing time of the Bi-2223 phase containing Ca-Cu as a main component is greatly reduced, and the manufacturing time when manufacturing a product using this superconductor is greatly reduced.

[Brief description of the drawings]

FIG. 1 shows firing time and Bi-2 in Example 1 of the present invention.
It is a graph which shows the relationship with 223 phase ratio.

FIG. 2 shows the firing time and Bi-2 in Example 2 of the present invention.
It is a graph which shows the relationship with 223 phase ratio.

FIG. 3 is a graph showing a relationship between a firing time and a Bi-2223 phase ratio in a comparative example.

FIG. 4 shows firing time and Bi-2 in Example 3 of the present invention.
It is a graph which shows the relationship with 223 phase ratio.

FIG. 5 shows the firing time and Bi-2 in Example 4 of the present invention.
It is a graph which shows the relationship with 223 phase ratio.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhiko Hayashi 1-3-1 Shimaya, Konohana-ku, Osaka-shi In Osaka Works, Sumitomo Electric Industries, Ltd. 35 Kawauchi Residence 1-201

Claims (11)

[Claims] 1. An oxide superconductor having a Bi-2223 phase containing Bi-Pb-Sr-Ca-Cu as a main component, wherein a part of Bi contained in the Bi-2223 phase is substituted by V. An oxide superconductor, characterized in that: 2. The method according to claim 1, wherein a part of Pb contained in the Bi-2223 phase is substituted with V.
2. The oxide superconductor according to claim 1. 3. The method according to claim 1, wherein B is added.
The oxide superconductor according to claim 1. 4. The element ratio between Bi and V contained in the Bi-2223 phase is 0.05 <V / (Bi + V) <0.2.
2. The oxide superconductor according to claim 1, wherein: 5. The element ratio of Bi, Pb and V contained in the Bi-2223 phase is 0.04 <V / (Bi + Pb +
3. The oxide superconductor according to claim 2, wherein V) <0.20. 6. Oxidation produced by using a raw material having the same composition ratio as a composition obtained by substituting a part of Bi contained in a Bi-2223 phase containing Bi-Pb-Sr-Ca-Cu as a main component with V. Of manufacturing superconductors. 7. An oxide superconductor manufactured using a material obtained by adding V to a material having the same composition ratio as that of a Bi-2223 phase containing Bi-Pb-Sr-Ca-Cu as a main component as a raw material. Manufacturing method. 8. The method for producing an oxide superconductor according to claim 6, wherein B is added to said raw material. 9. V is 0.1 m with respect to 1 mol of the raw material.
The method for producing an oxide superconductor according to any one of claims 6 and 7, characterized by being added in an amount of not less than ol and not more than 0.3 mol. 10. B is 0.1 to 1 mol of the raw material.
The method for producing an oxide superconductor according to claim 8, wherein the oxide superconductor is added in an amount of not less than 0.2 mol and not more than 0.2 mol. 11. An oxide superconductor characterized by adding a V compound when producing an oxide superconductor having a Bi-2223 phase containing Bi-Pb-Sr-Ca-Cu as a main component. Manufacturing method.