JP4867380B2 - Superconducting wire, manufacturing method thereof and superconducting equipment - Google Patents

Description

The present invention relates to a superconducting wire containing (Bi, Pb) 2223 (referring to (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _{10 + δ} , hereinafter the same), a method for manufacturing the same, and a superconducting device. , Pb) The present invention relates to a superconducting wire having a high orientation of the 2223 crystal and a high critical current, a manufacturing method thereof, and a superconducting device.

  A superconducting wire containing (Bi, Pb) 2223 is known as an oxide superconducting wire having a high critical temperature and a high critical current. Such a superconducting wire containing (Bi, Pb) 2223 is formed by filling a raw material powder into a metal sheath, plastically processing the metal sheath filled with the raw material powder to form a tape-like wire, and heat-treating the obtained wire. Then, the raw material powder in the wire is sintered to form (Bi, Pb) 2223 which is a good superconducting phase (see, for example, Patent Document 1 and Patent Document 2). The plastic working is a general term for processing in which a metal sheath filled with a raw material powder is plastically deformed to form a wire rod, and includes wire drawing, rolling, pressing, and the like.

  Here, in order to further increase the critical current of the superconducting wire containing (Bi, Pb) 2223, it is necessary to further increase the orientation of the (Bi, Pb) 2223 crystal. Specifically, by aligning the plane formed by the crystal axes a and b of the (Bi, Pb) 2223 crystal and the tape surface of the wire so as to be substantially parallel, the criticality of the wire is obtained. The current is increased.

However, until now, studies on the orientation of (Bi, Pb) 2223 crystals have not been sufficiently conducted, and for this reason, development of a method for producing a superconducting wire having a high orientation of (Bi, Pb) 2223 crystals has progressed. There wasn't.
Japanese Patent Laid-Open No. 03-138820 Japanese Patent Laid-Open No. 04-292812

  It is an object of the present invention to provide a superconducting wire having a high (Bi, Pb) 2223 crystal orientation and a high critical current, a method for producing the same, and a superconducting device.

The present invention, (Bi, Pb) A method of manufacturing a superconducting wire including _{2223, Bi2212 (Bi 2 Sr 2} CaCu 2 O 8 + refers to _[delta], hereinafter the same) and a metal pipe raw material powder containing a Pb compound A step of drawing a metal pipe filled with raw material powder to form a clad wire, a step of bundling a plurality of clad wires to form a multi-core wire, and a multi-core wire To produce (Bi, Pb) 2212 ((Bi, Pb) ₂ Sr ₂ CaCu ₂ O _{8 + δ} , hereinafter the same) from Bi2212 and a Pb compound, and a multifilamentary wire that has been subjected to a plurality of heat treatments A step of forming a tape-shaped wire by rolling the wire and a step of sintering the wire to generate (Bi, Pb) 2223, and in the step of sintering the wire during the temperature rise (Bi , Pb) 221 A method for producing a superconducting wire characterized in that a Pb compound and Bi 2212 are produced from 2 and (Bi, Pb) 2212 is produced again from the Pb compound and Bi 2212 formed during the temperature rise.

  In the method for producing a superconducting wire according to the present invention, in the step of sintering the wire, the oxygen gas partial pressure in the atmosphere from 600 ° C. to 800 ° C. during the temperature rise is set to 1 kPa or more, and from 600 ° C. to 800 ° C. during the temperature rise. The rate of temperature rise up to 20 ° C./hr to 200 ° C./hr can be set.

Further, the present invention is a superconducting wire that includes a filament containing (Bi, Pb) 2223 manufactured by the above manufacturing method , and the ratio of (Bi, Pb) 2223 in the filament is 98% or more, This is a superconducting wire having an average misalignment angle of (Bi, Pb) 2223 of 10.3 ° or less . Moreover, this invention is a superconducting apparatus containing said superconducting wire.

  ADVANTAGE OF THE INVENTION According to this invention, the superconducting wire which has the high orientation of (Bi, Pb) 2223 crystal and high critical current, its manufacturing method, and a superconducting apparatus can be provided.

  The method for producing a superconducting wire according to the present invention is a method for producing a superconducting wire containing (Bi, Pb) 2223, the step of filling a raw material powder containing Bi2212 and a Pb compound into a metal pipe, and the filling of the raw material powder A step of forming a clad wire by drawing a metal pipe formed, a step of forming a multi-core wire by bundling a plurality of clad wires, and a heat treatment of the multi-core wire to form Bi2212 and a Pb compound ( (Bi, Pb) 2212 generating step (referred to as a heat treatment step hereinafter) and a step of forming a tape-shaped wire rod by rolling a multi-core wire subjected to a plurality of heat treatments (referred to as a rolling step, hereinafter the same). , And (Bi, Pb) 221 during the temperature increase in the sintering step, including the step of sintering the wire to produce (Bi, Pb) 2223 (hereinafter referred to as the sintering step). From to produce a Pb compound and Bi2212, Pb compounds formed during heated and again Bi2212 (Bi, Pb), characterized in that to produce 2212.

In order to increase the critical current of a superconducting wire containing (Bi, Pb) 2223, it is necessary to increase the orientation of (Bi, Pb) 2223 crystals. The (Bi, Pb) 2223 is composed of (Bi, Pb) 2212 and alkaline earth oxides (for example, (Ca, Sr) CuO ₂ , (Ca, Sr) ₂ CuO ₃ , (Ca , Sr) ₁₄ Cu ₂₄ O ₄₁ , and so on)). Therefore, it is considered that the orientation of the (Bi, Pb) 2223 crystal can be increased by increasing the orientation of the (Bi, Pb) 2212 crystal.

  In the present invention, the Pb compound contained in the raw material powder is dissolved in Bi2212 contained in the raw material powder, and (Bi, Pb) 2212 is generated by the heat treatment step of the multi-core wire before rolling. The (Bi, Pb) 2212 crystal is a plate-like crystal whose principal surface is a plane parallel to the plane formed from the crystal axis a and the crystal axis b. , Pb) The 2212 crystal is oriented so that its main surface is substantially parallel to the tape surface of the wire (width × length direction, hereinafter the same), and the orientation becomes high.

  However, since the rolling process is performed at a very large pressure, the (Bi, Pb) 2212 crystal is reduced in crystallinity (meaning the order of atomic arrangement in the crystal, the same applies hereinafter) by this rolling process, Cracks occur.

  Therefore, in order to recrystallize the (Bi, Pb) 2212 crystal in which the crystallinity is reduced or cracks are generated, a Pb compound is generated and precipitated from (Bi, Pb) 2212 during the temperature increase in the sintering process. Bi2212 is generated once by this, and then the Pb compound is dissolved again in this Bi2212, so that the crystals with reduced or broken crystallinity recombine with each other, resulting in high orientation and high crystallinity. (Bi, Pb) 2212 crystals are obtained. The highly oriented (Bi, Pb) 2212 crystal thus obtained reacts with an alkaline earth oxide to produce a highly oriented (Bi, Pb) 2223 crystal, which is a superconducting wire having a high critical current. Is considered to be obtained.

Here, the Pb compound is not particularly limited as long as it is produced in the production method according to the present invention, but representative examples include Ca ₂ PbO ₄ , (Bi, Pb) 3221 ((Bi, Pb) ₃ Sr. ₂ Ca ₂ CuO _y , the same shall apply hereinafter).

In the sintering step of the method for producing a superconducting wire according to the present invention, the temperature rise and sintering of the wire are performed in a mixed gas atmosphere of oxygen gas and inert gas. Here, the inert gas is not particularly limited as long as it is a gas that does not react with the wire, but nitrogen gas, argon gas, and the like are preferably used. In this sintering step, the oxygen gas partial pressure in the atmosphere from 600 ° C. to 800 ° C. during the temperature rise is preferably 1 kPa or more. Since the valence of Pb in (Bi, Pb) 2212 is 2 ⁺ , the valence of Pb in the Pb compound is 4 ⁺ , and therefore, by increasing the oxygen gas partial pressure in the temperature rising atmosphere, the Pb compound Precipitation is promoted.

  In the sintering step of the method for producing a superconducting wire according to the present invention, the rate of temperature rise from 600 ° C. to 800 ° C. during temperature rise is preferably 20 ° C./hr or more and 200 ° C./hr or less. The temperature range from 600 ° C. to 800 ° C. is a temperature range in which a Pb compound is easily generated and precipitated. When the rate of temperature rise is less than 20 ° C./hr, other compounds (for example, Ca—Sr—Cu—O-based compounds) are produced as large lumps together with the Pb compound. When the rate of temperature rise exceeds 200 ° C./hr, the production and precipitation of the Pb compound is reduced.

  Here, (Bi, Pb) 2212 is generated again by dissolving the Pb compound in Bi 2212 again from Bi 2212 and the Pb compound generated by the precipitation reaction of the Pb compound from (Bi, Pb) 2212.

  As described above, Pb compound and Bi2212 are produced from (Bi, Pb) 2212, and (Bi, Pb) 2212 is produced again from Pb compound and Bi2212, so that the crystallinity is lowered in the rolling process. Alternatively, the broken (Bi, Pb) 2212 is regenerated, and (Bi, Pb) 2212 having high orientation and crystallinity is obtained. As the sintering further proceeds, a highly oriented and highly crystalline (Bi, Pb) 2223 is obtained by a reaction between the highly oriented (Bi, Pb) 2212 and an alkaline earth oxide. High superconducting wire can be obtained.

  The sintering temperature in the sintering step of the method for producing a superconducting wire according to the present invention is a temperature range in which (Bi, Pb) 2223 is generated by the reaction between (Bi, Pb) 2212 and an alkaline earth oxide. Although there is no particular limitation, 810 ° C. or higher and 835 ° C. or lower is preferable from the viewpoint of promoting the formation of (Bi, Pb) 2223. Further, the oxygen gas partial pressure in the atmosphere during sintering after raising the temperature to the sintering temperature is not particularly limited, but a viewpoint of sufficiently generating (Bi, Pb) 2223 and suppressing the generation of other compounds. From 4 kPa to 8 kPa is preferable. The sintering time is not particularly limited, but is preferably 10 hours or longer and 20 hours or shorter from the viewpoint of sufficiently generating (Bi, Pb) 2223 and suppressing the generation of other compounds.

  In the sintering process of the method for producing a superconducting wire according to the present invention, the rate of temperature increase from 600 ° C. to 800 ° C. is 20 ° C./hr to 200 ° C. in an atmosphere having an oxygen gas partial pressure of 7 kPa or more. (Bi, Pb) 2212 can be generated again within 2 hours after reaching the sintering temperature by increasing the sintering temperature to 810 ° C. or more and 835 ° C. or less. (Bi, Pb) 2223 can be sufficiently generated in about 10 hours after reaching the above. If this second generation of (Bi, Pb) 2212 is delayed more than 2 hours after reaching the sintering temperature, the generation of other compounds (for example, Ca—Sr—Cu—O-based compounds) increases, and ( Bi, Pb) 2223 is also delayed.

  In the method of manufacturing a superconducting wire according to the present invention, the rolling step and the sintering step can be performed twice or more in order to increase the ratio of (Bi, Pb) 2223.

  In the sintering step of the method of manufacturing a superconducting wire according to the present invention, a Pb compound is generated and precipitated from (Bi, Pb) to form Bi2212, or a Pb compound is dissolved in Bi2212 (Bi, Pb). Whether 22212 is produced can be determined by measuring the wire during the sintering process by the XRD (referred to as X-ray diffraction, hereinafter the same) method.

  In the sintering process, when the temperature was raised from 600 ° C. to 800 ° C. so that the temperature rising rate was 50 ° C./hr in an atmosphere having an oxygen gas partial pressure of 8 kPa, The X-ray diffraction measurement result of the raw material powder in the wire at temperature is shown in FIG.

In XRD using K _alpha line of Cu, with reference to FIG. 1 (a), respectively in the diffraction angle 2 [Theta] = 17.5 ° and _{2θ = 18.0 ° Ca 2 PbO 4} (110) plane and (020 ) Appears, and a diffraction peak derived from the (110) plane of (Bi, Pb) 3221 appears at 2θ = 17.75 °.

  Referring to FIG. 1B, a diffraction peak derived from the (200) plane of Bi2212 and (Bi, Pb) 2212 appears at 2θ = 33.0 °, and (Bi, Pb) A diffraction peak derived from the (020) plane of 2212 appears. This is because the crystal structure of Bi2212 is tetragonal, whereas the crystal structure of (Bi, Pb) 2212 is orthorhombic, so that a diffraction peak derived from the (200) plane appears for Bi2212. On the other hand, for (Bi, Pb) 2212, diffraction peaks derived from the (200) plane and the (020) plane appear.

Referring to FIG. 1A, Pb compound (Bi, Pb) 3221 is generated from 600 ° C. to 750 ° C. during the temperature increase, and Ca ₂ PbO ₄ is generated from 750 ° C. to 800 ° C. To do. That is, it can be seen that Pb compounds (Bi, Pb) 3221 and Ca ₂ PbO ₄ are generated in the temperature range from 600 ° C. to 800 ° C. during the temperature rise.

  Referring to FIG. 1B, there is a wide diffraction peak indicating (Bi, Pb) 2212 at room temperature (RT in FIG. 1) and at 500 ° C. during the temperature rise. The diffraction peak sharpened from 600 ° C. to 750 ° C. during the temperature rise, and the peak position was 2θ = 33.0 °. This corresponds to the position of the diffraction peak derived from the (200) plane of Bi2212 or (Bi, Pb) 2212. On the other hand, no diffraction peak was observed at the position of the diffraction peak derived from the (020) plane of (Bi, Pb) 2212. That is, it can be seen that from 600 ° C. to 750 ° C. during the temperature increase, a Pb compound was generated from (Bi, Pb) 2212 and deposited, and Bi 2212 was generated.

  Next, from 800 ° C. to 830 ° C. during the temperature rise, the position of the diffraction peak (2θ = 33.0 °) derived from the (200) plane of Bi 2212 or (Bi, Pb) 2212 and (Bi, Pb) 2212 A diffraction peak having a peak position at any position (2θ = 33.1 °) of the diffraction peak derived from the (020) plane was obtained. That is, it can be seen that (Bi, Pb) 2212 is generated again from 800 ° C. to 830 ° C. during the temperature rise.

  Further, from 500 ° C. to 830 ° C. during the temperature increase, the diffraction peaks derived from (Bi, Pb) 2212 and Bi 2212 steepened and the half width was reduced, so that (Bi, Pb) 2212 to Pb compound and It can be understood that the crystallinity of (Bi, Pb) 2212 was improved by Bi 2212 being produced and further through the reaction process in which (Bi, Pb) 2212 was produced again from the Pb compound and Bi 2212.

Here, the method for preparing the raw material powder containing Bi2212 and the Pb compound used in the method for producing a superconducting wire according to the present invention is not particularly limited, but Bi ₂ O ₃ , PbO, and SrCO ₃ as raw materials are not particularly limited. , CaCO ₃ and CuO, Bi: Pb: Sr: Ca: Cu = 1.7 to 1.8: 0.3 to 0.35: 2.0: 2.0: 3.0 It is obtained by mixing at a molar ratio and sintering at 700 ° C. to 850 ° C. for 10 to 40 hours in an air atmosphere or a reduced pressure atmosphere at least once. For example, a powder obtained by mixing the above five kinds of raw material powders in the above molar ratio is subjected to two heat treatments of 700 ° C. × 8 hours and 800 ° C. × 10 hours, or three times of 840 ° C. × 4 hours. The raw material powder can be prepared by performing a heat treatment. Here, the raw material powder is preferably pulverized after each heat treatment.

  Further, by injecting an aqueous nitric acid solution in which the above-mentioned kind of raw material powder is dissolved in the above molar ratio into a heated furnace, evaporation of moisture in the aqueous nitric acid solution, generation of oxide by thermal decomposition of nitrate, and The raw material powder can also be prepared by a spray pyrolysis method in which the raw material powder is instantly generated by the reaction between oxides. Further, in order to adjust the constituent phase of the raw material powder, the raw material powder obtained by the spray pyrolysis method is subjected to a heat treatment of at least 750 ° C. to 840 ° C., oxygen gas partial pressure of 8 kPa to 100 kPa, and 2 hours to 10 hours. It may be performed once.

  Since the superconducting wire according to the present invention is manufactured by the above-described manufacturing method, the orientation of (Bi, Pb) 2223 crystal contained in the superconducting wire is high and the critical current is high.

  Moreover, since the superconducting device according to the present invention includes a superconducting wire having a high orientation of (Bi, Pb) 2223 crystal and a high critical current as described above, it has excellent superconducting characteristics. Here, the superconducting device is not particularly limited as long as it includes the superconducting wire, and examples thereof include a superconducting cable, a superconducting coil, a superconducting transformer, a superconducting current limiter, and a superconducting power storage device.

  The superconducting wire according to the present invention and the manufacturing method thereof will be described more specifically based on the following examples.

Example 1
Five kinds of powders of Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ and CuO as raw materials are used as Bi: Pb: Sr: Ca: Cu = 1.7 to 1.8: 0.3 to 0.35. : 2.0: 2.0: 3.0 in a molar ratio of 2 at 700 ° C. × 8 hours and 800 ° C. × 10 hours in the atmosphere (oxygen gas partial pressure 21 kPa, nitrogen gas partial pressure 79 kPa) The raw material powder was prepared by performing the heat treatment twice. Here, after each heat treatment, the raw material powder was crushed into powder. The raw material powder thus prepared was subjected to XRD analysis, and Bi2212 was the main phase.

  After filling this raw material powder into a silver pipe having a diameter of 46 mm, the silver pipe filled with the raw material powder was drawn to obtain a clad wire having a diameter of 3 mm. The 55 clad wires were bundled and drawn to obtain a multifilament wire in which the raw material powder became a filament core and was coated with silver.

  Next, the multi-core wire was heat-treated at 760 ° C. for 2 hours in a mixed gas atmosphere having an oxygen gas partial pressure of 0.1 kPa and a nitrogen gas partial pressure of 99.9 Pa. An XRD analysis of the filament of the raw material powder in the multifilamentary wire after the heat treatment revealed that (Bi, Pb) 2212 was produced.

  Next, the heat-treated multi-core wire is first-rolled, and a tape shape having a width of 4.00 mm, a thickness of 0.240 mm, and a length of 100 mm in which a 55-core filament is coated with silver at a silver ratio of 1.7. Wire (hereinafter referred to as primary rolled wire). In addition, silver ratio means ratio of the area of the silver part with respect to the area of the filament part in the cross section (width x thickness cross section) of a wire.

Next, in the primary rolled wire, the temperature rising atmosphere from 600 ° C. to 800 ° C. is a mixed gas atmosphere having an oxygen gas partial pressure of 1 kPa and a nitrogen gas partial pressure of 99 kPa, and the temperature rising rate from 600 ° C. to 800 ° C. The temperature was raised to 50 ° C./hr and sintering was performed at 830 ° C. for 15 hours (hereinafter referred to as primary sintering). At the time of temperature increase in the primary sintering, the wire arranged in the heat treatment furnace is irradiated with 25 keV synchrotron radiation X-rays, and the transmitted diffracted light is read by IP (image plate, the same applies hereinafter), By performing IP image analysis, the presence or absence of diffraction peaks derived from (Bi, Pb) 3221 and Ca ₂ PbO ₄ which are Pb compounds inside the filament of the wire being heated, Bi 2212 and (Bi, Pb) 2212 The presence or absence of the derived diffraction peak was examined.

During the temperature increase in the primary sintering, a diffraction peak derived from the (110) plane of (Bi, Pb) 3221 which is a Pb compound and (110) of Ca ₂ PbO ₄ in the temperature range of 600 ° C. to 800 ° C. At least one of diffraction peaks derived from the plane and the (020) plane was observed. Further, in the temperature range of 700 ° C. to 750 ° C., a diffraction peak derived from the (200) plane of Bi2212 was observed, but a diffraction peak derived from the (020) plane of (Bi, Pb) 2212 was not observed. . From these facts, it can be seen that the Pb compound and Bi2212 were formed in the temperature range of 600 ° C. to 800 ° C. during the temperature increase in the primary sintering. The wire obtained by the primary sintering (hereinafter referred to as primary wire) has a ratio of (Bi, Pb) 2223 in the filament of 94%, and the average misalignment angle α of (Bi, Pb) 2223 crystals is 10. It was 3 °. The primary wire had a critical current of 25A.

  Here, the (Bi, Pb) 2223 ratio of the filament is the diffraction peak intensity derived from the (0012) plane of Bi2212 and (Bi, Pb) 2212 and the diffraction peak derived from the (0014) plane of (Bi, Pb) 2223. It is calculated as a percentage of the diffraction peak intensity derived from the (0014) plane of (Bi, Pb) 2223 with respect to the total intensity.

  Further, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal means the surface formed by the a axis and the b axis of each (Bi, Pb) 2223 crystal and the tape surface (width × length direction) of the wire. This is the average angle formed with the surface. The smaller the average misorientation angle α of (Bi, Pb) 2223 crystal, the higher the orientation of (Bi, Pb) 2223 crystal. The average misorientation angle α of the (Bi, Pb) 2223 crystal is calculated as ½ of the half width of the diffraction peak derived from the (0024) plane of (Bi, Pb) 2223.

The critical current of the wire was measured in a self-magnetic field at a temperature of 77 K by the four probe method. Here, the critical current was defined as a current when a voltage of 1 × 10 ⁻⁶ V was generated per 1 cm of the superconducting wire.

Next, the above-described primary wire is subjected to secondary rolling at a rolling reduction of 10%, and a tape-like wire having a width of 4.1 mm, a thickness of 0.23 mm, and a length of 100 mm (hereinafter referred to as a secondary rolled wire) is obtained. Obtained. The rolling reduction is the following formula (1)
Reduction ratio (%) = {1- (Thickness of wire after rolling) / (Thickness of wire before rolling)} × 100
... (1)
Is defined by

  Next, the above-mentioned secondary rolled wire is sintered for the second time (hereinafter referred to as secondary sintering) under a mixed gas atmosphere of oxygen gas partial pressure of 8 kPa and nitrogen gas partial pressure of 92 kPa at 828 ° C. for 30 hours. Then, a superconducting wire containing (Bi, Pb) 2223 (hereinafter also referred to as final wire) was obtained.

  The average misalignment angle α of the (Bi, Pb) 2223 crystal in the filament of the final wire obtained as described above was equivalent to that of the primary wire, but the (Bi, Pb) 2223 ratio was 98%. As a result, the critical current of the final wire became 87A. The results are summarized in Table 1.

(Example 2)
In the same manner as in Example 1 except that, during the primary sintering, the temperature was raised from 600 ° C. to 800 ° C. as a mixed gas atmosphere having an oxygen gas partial pressure of 4 kPa and a nitrogen gas partial pressure of 96 kPa ( A superconducting wire containing Bi, Pb) 2223 was produced. During the temperature increase in the primary sintering, a Pb compound and Bi2212 were generated in a temperature range of 600 ° C. to 800 ° C. The ratio of (Bi, Pb) 2223 in the filament of the primary wire is 96%, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal is 10.0 °, and the critical current of the primary wire is 31A. It was. The average misalignment angle α of the (Bi, Pb) 2223 crystal in the filament of the final wire was the same as that of the primary wire, but the ratio of (Bi, Pb) 2223 was improved to 99%. The critical current was 97A. The results are summarized in Table 1.

(Example 3)
During the primary sintering, the temperature rising atmosphere from 600 ° C. to 800 ° C. is a mixed gas atmosphere having an oxygen gas partial pressure of 8 kPa and a nitrogen gas partial pressure of 92 kPa, and the temperature rising rate from 600 ° C. to 800 ° C. is 20 ° C. / A superconducting wire containing (Bi, Pb) 2223 was produced in the same manner as in Example 1 except that the temperature was raised to be hr. During the temperature increase in the primary sintering, a Pb compound and Bi2212 were generated in a temperature range of 600 ° C. to 800 ° C. The ratio of (Bi, Pb) 2223 in the filament of the primary wire is 86%, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal is 9.0 °, and the critical current of the primary wire is 33A. It was. The average misalignment angle α of the (Bi, Pb) 2223 crystal in the filament of the final wire was the same as that of the primary wire, but the ratio of (Bi, Pb) 2223 was improved to 99%. The critical current of was 124A. The results are summarized in Table 1.

Example 4
In the same manner as in Example 1 except that, during the primary sintering, the temperature was raised from 600 ° C. to 800 ° C. as a mixed gas atmosphere having an oxygen gas partial pressure of 8 kPa and a nitrogen gas partial pressure of 92 kPa ( A superconducting wire containing Bi, Pb) 2223 was produced. During the temperature increase in the primary sintering, a Pb compound and Bi2212 were generated in a temperature range of 600 ° C. to 800 ° C. The ratio of (Bi, Pb) 2223 in the filament of the primary wire is 88%, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal is 8.8 °, and the critical current of the primary wire is 42A. It was. Further, the ratio of (Bi, Pb) 2223 in the filament of the final wire was 99%, and the critical current of the final wire was 130A. The results are summarized in Table 1.

  1 and the description thereof are based on the result of XRD measurement of the filament raw material powder in the wire at the time of temperature increase in the primary sintering performed in this example. Specifically, in the primary sintering step of the present embodiment, a wire is installed in a heat treatment furnace that can change the gas atmosphere, and the diffracted light transmitted by applying 25 keV synchrotron radiation X-rays to the wire is transmitted to an IP (image plate). , The same applies hereinafter) and image analysis of the IP was performed to perform XRD measurement inside the filament of the wire being heated.

(Example 5)
During the primary sintering, the temperature rising atmosphere from 600 ° C. to 800 ° C. is a mixed gas atmosphere having an oxygen gas partial pressure of 8 kPa and a nitrogen gas partial pressure of 92 kPa, and the temperature rising rate from 600 ° C. to 800 ° C. is 200 ° C. / A superconducting wire containing (Bi, Pb) 2223 was produced in the same manner as in Example 1 except that the temperature was raised to be hr. During the temperature increase in the primary sintering, a Pb compound and Bi2212 were generated in a temperature range of 600 ° C. to 800 ° C. The ratio of (Bi, Pb) 2223 in the filament of the primary wire is 90%, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal is 8.6 °, and the critical current of the primary wire is 38A. It was. The ratio of (Bi, Pb) 2223 in the filament of the final wire was 98%, and the critical current of the final wire was 128A. The results are summarized in Table 1.

(Example 6)
During the primary sintering, the temperature rising atmosphere from 600 ° C. to 800 ° C. is a mixed gas atmosphere having an oxygen gas partial pressure of 8 kPa and a nitrogen gas partial pressure of 92 kPa, and the temperature rising rate from 600 ° C. to 800 ° C. is 250 ° C. / A superconducting wire containing (Bi, Pb) 2223 was produced in the same manner as in Example 1 except that the temperature was raised to be hr. During the temperature increase in the primary sintering, a Pb compound and Bi2212 were generated in a temperature range of 600 ° C. to 800 ° C. The ratio of (Bi, Pb) 2223 in the filament of the primary wire is 94%, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal is 9.6 °, and the critical current of the primary wire is 24A. It was. The ratio of (Bi, Pb) 2223 in the filament of the final wire was 98%, and the critical current of the final wire was 98A. The results are summarized in Table 1.

(Example 7)
In the same manner as in Example 1 except that, during the primary sintering, the temperature was raised from 600 ° C. to 800 ° C. as a mixed gas atmosphere having an oxygen gas partial pressure of 12 kPa and a nitrogen gas partial pressure of 88 kPa ( A superconducting wire containing Bi, Pb) 2223 was produced. During the temperature increase in the primary sintering, a Pb compound and Bi2212 were generated in a temperature range of 600 ° C. to 800 ° C. The ratio of (Bi, Pb) 2223 in the filament of the primary wire is 85%, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal is 9.0 °, and the critical current of the primary wire is 45A. It was. The ratio of (Bi, Pb) 2223 in the filament of the final wire was 99%, and the critical current of the final wire was 118A. The results are summarized in Table 1.

(Example 8)
In the same manner as in Example 1 except that, during the primary sintering, the temperature was raised from 600 ° C. to 800 ° C. as a mixed gas atmosphere having an oxygen gas partial pressure of 21 kPa and a nitrogen gas partial pressure of 79 kPa ( A superconducting wire containing Bi, Pb) 2223 was produced. During the temperature increase in the primary sintering, a Pb compound and Bi2212 were generated in a temperature range of 600 ° C. to 800 ° C. The ratio of (Bi, Pb) 2223 in the filament of the primary wire is 83%, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal is 8.6 °, and the critical current of the primary wire is 47A. It was. The ratio of (Bi, Pb) 2223 in the filament of the final wire was 99%, and the critical current of the final wire was 121A. The results are summarized in Table 1.

(Comparative Example 1)
Example 1 is the same as Example 1 except that during the primary sintering, the temperature was raised from 600 ° C. to 800 ° C. as a mixed gas atmosphere having an oxygen gas partial pressure of 0.01 kPa and a nitrogen gas partial pressure of 99.99 kPa. Similarly, a superconducting wire containing (Bi, Pb) 2223 was produced. In order to prevent the filaments in the wire from melting, the atmosphere at the time of temperature rising above 810 ° C. and sintering was a mixed gas atmosphere having an oxygen gas partial pressure of 8 kPa and a nitrogen gas partial pressure of 92 kPa.

  In the superconducting wire of this comparative example, the ratio of (Bi, Pb) 2223 in the filament of the primary wire is 92%, and the average misalignment angle α of the (Bi, Pb) 2223 crystal is as large as 10.4 °. The critical current of the primary wire was as low as 18A. Further, the ratio of (Bi, Pb) 2223 in the filament of the final wire was improved to 98%, but the critical current of the final wire was 80A. The results are summarized in Table 1.

In this comparative example, with reference to FIG. 2 (a), diffraction peaks derived from (Bi, Pb) 3221 and Ca ₂ PbO ₄ which are Pb compounds are not seen from 600 ° C. to 800 ° C. during temperature rise. It was. That is, it was found that no Pb compound was generated in the temperature range from 600 ° C. to 800 ° C. during the temperature increase.

In addition, referring to FIG. 2B, a wide diffraction peak indicating (Bi, Pb) 2212 exists at 600 ° C. during the temperature rise from room temperature (RT in FIG. 2). The diffraction peak sharpened from 600 ° C. to 830 ° C. during the temperature increase, and the peak was divided into two. The peak positions were 2θ = 33.0 ° and 2θ = 33.1 °. These correspond to the positions of the diffraction peak derived from the (200) plane of Bi2212 or (Bi, Pb) 2212 and the diffraction peak derived from the (020) plane of (Bi, Pb) 2212, respectively. That is, it can be seen that (Bi, Pb) 2212 was always present from 600 ° C. to 800 ° C. during the temperature increase. Therefore, the presence or absence of Bi2212 could not be confirmed, but during the temperature increase from 600 ° C. to 800, (Bi, Pb) 3221 and Pb compound of Ca ₂ PbO ₄ were not generated, and Pb was (Bi, Pb). 2212 was found to be doped.

  As is apparent from Table 1, in Examples 1 to 8, in the primary sintering step, Pb compound and Bi 2212 were generated from (Bi, Pb) 2212 during the temperature increase, and Pb formed during the temperature increase. By generating (Bi, Pb) 2212 again from the compound and Bi 2212, the average misorientation angle of the (Bi, Pb) 2212 crystal in the filament of the primary wire is reduced, and the (Bi, Pb) of the primary wire is reduced. The smaller the average misorientation angle of the 2212 crystal, the smaller the average misorientation angle of the (Bi, Pb) 2223 crystal. It can be seen that the smaller the average misorientation angle of the (Bi, Pb) 2223 crystal and the higher the ratio of (Bi, Pb) 2223 in the filament, the higher the critical current of the primary wire and the final wire.

  In particular, as shown in Examples 3 to 5, 7 and 8, the wire material was heated in the primary sintering step in an atmosphere having an oxygen gas partial pressure of 7 kPa or more, and during this temperature increase from 600 ° C. to 800 ° C. By setting the rate of temperature rise at 20 ° C./hr to 200 ° / hr, the average misalignment angle α of (Bi, Pb) 2223 crystals in the primary wire is reduced to less than 10.0 °. The critical current of the wire could be 33 A or more, and a final wire having a high critical current exceeding 120 A could be obtained.

  On the other hand, in Comparative Example 1, since the Pb compound is not generated during the temperature increase in the primary sintering step, the average orientation deviation angle α of the (Bi, Pb) 2223 crystal formed is large. The critical current of the wire and the final wire became low.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. 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.

It is a figure which shows the diffraction peak by the XRD measurement of the raw material powder in the filament of the wire at the time of the temperature rising in the sintering process of the manufacturing method of the superconducting wire concerning this invention. Here, (a) shows a diffraction peak derived from a Pb compound, and (b) shows a diffraction peak derived from Bi2212 and (Bi, Pb) 2212. It is a figure which shows the diffraction peak by the XRD measurement of the raw material powder in the filament of a wire when it heats up in a low oxygen gas partial pressure atmosphere in the sintering process of the manufacturing method of a superconducting wire. Here, (a) shows a diffraction peak derived from a Pb compound, and (b) shows a diffraction peak derived from Bi2212 and (Bi, Pb) 2212.

Claims (5)

A method of manufacturing a superconducting wire containing (Bi, Pb) 2223,
A step of filling a metal pipe with a raw material powder containing Bi2212 and a Pb compound, a step of forming a clad wire by drawing the metal pipe filled with the raw material powder, and bundling a plurality of the clad wires A step of forming a multi-core wire by drawing, a step of heat-treating the multi-core wire to generate (Bi, Pb) 2212 from the Bi2212 and the Pb compound, and rolling the multi-core wire that has been heat-treated A step of forming a tape-like wire rod, and a step of generating (Bi, Pb) 2223 by sintering the wire rod,
In the step of sintering the wire, Pb compound and Bi 2212 are generated from the (Bi, Pb) 2212 during the temperature rise, and again (Bi, Pb) from the Pb compound and the Bi 2212 formed during the temperature rise. 22. A method of manufacturing a superconducting wire characterized by generating 2212.   2. The method of manufacturing a superconducting wire according to claim 1, wherein, in the step of sintering the wire, an oxygen gas partial pressure in an atmosphere from 600 ° C. to 800 ° C. during the temperature rise is 1 kPa or more.   2. The superconducting wire according to claim 1, wherein in the step of sintering the wire, a rate of temperature increase from 600 ° C. to 800 ° C. during the temperature increase is 20 ° C./hr or more and 200 ° C./hr or less. Production method. A superconducting wire comprising a filament containing (Bi, Pb) 2223 produced by the production method according to any one of claims 1 to 3 ,
The ratio of the (Bi, Pb) 2223 in the filament is 98% or more,
A superconducting wire in which an average orientation deviation angle of the (Bi, Pb) 2223 crystal is 10.3 ° or less .   A superconducting device comprising the superconducting wire according to claim 4.

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