JP2002208322A - Oxide superconducting synthetic powder and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide superconducting synthetic powder of (BiPb)2Sr2Ca2 Cu3OX system that is capable of increasing further the critical current density of the oxide superconducting cable material that is manufactured by PIT method which is a representative manufacturing method of oxide superconducting cable material. SOLUTION: In the oxide superconducting synthetic powder, a peak having 3 or more peak strength ratio when the peak strength on the face of Ca2PbO4 (110) is made 100, exists between the peak of (110) face of Ca2PbO4 and the peak of Ca2PbO4 (020) face, when the measurement of the diffraction X-ray strength using CuK α beam is made. By using this oxide superconducting synthetic powder, the critical current density of the oxide superconducting cable material manufactured by PIT method can be further increased. As a manufacturing method of the oxide superconducting synthetic powder having the above peak, the material powder is fired in the oxidation gas flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an oxidized superconducting synthetic powder used for producing a Bi (Pb) 2223-based oxide superconducting wire capable of obtaining a high critical current density and a method for producing the same.

[0002]

2. Description of the Related Art At present, the following methods are mainly used for producing oxide superconductors into wires. 1. 1. PIT (Powder in Tube) method 2. Coating method Next, an outline of each method will be described.

[0003] 1. In the PIT method, a metal which does not react with the oxide superconductor even when heated together with the oxide superconductor is prepared as a matrix (for example, Ag or an Ag alloy). Next, a tube is made of this metal, and the tube is filled with the oxide superconductor powder. And it is a method of processing into a fine wire while repeating drawing, rolling and heat treatment. This PIT method mainly uses (BiPb)
_This is a method suitable for producing a ₂ Sr ₂ Ca ₂ Cu ₃ Ox-based oxide superconducting wire. This is because Bi-based oxide superconductors have the feature that crystal grains grow in a plate shape.
When a method of stretching in the longitudinal direction such as the method is applied, plate-like crystal grains are easily aligned in the longitudinal direction. On the other hand, since the superconducting current has a property of easily flowing in the longitudinal direction of the plate-like crystal, a wire having good superconducting properties can be manufactured at a relatively low cost by the PIT method.

[0004] 2. Is a method of adding a suitable organic binder to an oxide superconductor powder to form a paste, coating the surface of an Ag tape, and heat treating the Ag tape to obtain a wire. This method is mainly Bi
_This is a method suitable for producing a ₂ Sr ₂ Ca ₁ Cu ₂ O _y -based oxide superconducting wire.

[0005] 3. The thin-film method is to form an intermediate layer with good compatibility, such as having a low lattice constant and a low reactivity, close to the oxide superconductor on a metal tape wire, and forming an oxide superconductor layer on the intermediate layer. This is a method of laminating wires. This method is mainly suitable for producing a Y ₁ Ba ₂ Cu ₃ O _z -based oxide superconducting wire. Because the Y ₁ Ba ₂ Cu ₃ O _z -based oxide superconductor is compared with the Bi-based oxide superconductor,
Since the two-dimensionality of crystals and crystal growth is weak, for example, the PI
It is difficult to apply the T method. In this thin film method, the properties of the intermediate layer have a great influence on the superconductivity. For example, I
BAD (Ion Beam Assist Depos)
The YSZ two-dimensional film is formed as an intermediate layer by the (Ition) method, and Y ₁ B deposited and deposited thereon is formed.
a ₂ Cu ₃ O _z superconducting properties of the oxide superconductor has been confirmed that dramatically improved. However, long wire manufacturing technology is still under development, and a wire having a length necessary for practical use has not been obtained at present.

[0006] The above description has been given of the current method of manufacturing a typical oxide superconducting wire. However, considering the ease of manufacturing, the manufacturing cost, and the superconducting characteristics, it is considered that the most practical level is as follows. PIT method. At present, the critical current density is 20,000-25,000 A / c
m ² , but practically 350,000
A characteristic of 0 A / cm ² or more is desired.

[0007]

SUMMARY OF THE INVENTION Ag as a matrix
Alternatively, in the PIT method using an Ag alloy, when an attempt is made to further increase the critical current density, finally, depending on the properties of the oxide superconductor powder filled in the metal tube, that is, the oxide superconducting synthetic powder, It is known that the superconducting properties such as the critical current density of the obtained oxide superconducting wire greatly change. However, it has not been clarified yet what kind of properties of the oxide superconducting synthetic powder can be used to obtain an oxide superconducting wire having a high critical current density. The present invention has been made under the above-mentioned background, and mainly comprises (BiPb) ₂ S
An object of the present invention is to provide an oxide superconducting synthetic powder which greatly contributes to an improvement in critical current density in an r ₂ Ca ₂ Cu ₃ O _x -based oxide superconducting wire and a method for producing the same.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a characteristic to be satisfied by the oxide superconducting synthetic powder, an X-ray diffractometer is used to convert CuKα radiation into X-rays. When X-ray irradiation is performed at an incident angle θ, the peak of the (110) plane of Ca ₂ PbO ₄ and Ca ₂
1 at 2θ between the peak of the PbO ₄ (020) plane
The inventors have found that it is important to contain a substance having a peak at 7.70 ° to 17.90 °, and have completed the present invention.

That is, the first invention is directed to a Bi—Pb—Sr—Ca— using Ag or Ag alloy as a matrix.
Measurement of diffracted X-ray intensity when irradiating CuKα ray to the oxide superconducting synthetic powder using an X-ray diffractometer using an oxide superconducting synthetic powder used in the production of a Cu-based oxide superconducting wire When the results are shown in a graph in which the vertical axis represents the diffraction X-ray intensity and the horizontal axis represents the diffraction angle, (1) of Ca ₂ PbO ₄
The peak intensity of the Ca ₂ PbO ₄ (110) plane is 1 between the peak of the 10) plane and the peak of the Ca ₂ PbO ₄ (020) plane.
The oxide superconducting synthetic powder is characterized in that there is a peak having a peak intensity ratio of 3 or more when it is set to 00.

[0010] The second invention is the irradiation of the CuKα line, when irradiated with a incident angle theta, between the peaks of the Ca ₂ PbO ₄ (020) plane of the (110) plane of the Ca ₂ PbO ₄ The existing peak is 17.70 ° to 1 at 2θ.
7. An oxide superconducting synthetic powder according to the first invention, which is located at a position of 90 °.

[0011] A third aspect of the present invention is that the peak of the (110) plane of Ca ₂ PbO ₄ and the Ca ₂ P
a bO ₄ (020) plane oxide superconducting synthetic powder according to the first invention, characterized in that the peak of PbO is present between the peaks of.

According to a fourth aspect of the present invention, there is provided an oxide superconducting wire manufactured using the oxide superconducting synthetic powder according to any one of the first to third aspects and using Ag or an Ag alloy as a matrix. It is.

The fifth invention is a process for producing the above-mentioned oxide superconducting synthetic powder, which comprises mixing powders of a Bi compound, a Pb compound, a Sr compound, a Ca compound and a Cu compound, at a temperature of 750 to 850 ° C. for 10 hours. A method for producing an oxide superconducting synthetic powder according to the first to third aspects of the present invention, wherein firing is performed in an oxidizing gas flow for up to 20 hours.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted various trials and errors in order to solve the above-mentioned problems. As a result, when an oxide superconducting synthetic powder is produced by the method described below, It was discovered that the oxide superconducting wire used greatly contributed to the improvement of the critical current density. Hereinafter, the manufacturing method will be described first.

(Raw material preparation and mixing step) Bi compound,
Powders of the Pb compound, the Sr compound, the Ca compound and the Cu compound are mixed so as to have a desired molar ratio. At this time, Bi ₂ O ₃ as a Bi compound, PbO as a Pb compound, SrCO ₃ as a Sr compound, CaCO ₃ , CaO, Ca (OH) ₂ as a Ca compound, C
CuO was preferred as the u compound. In addition to the above-mentioned raw materials, Bi, Pb, Sr, C
Raw materials prepared by adjusting each element of a and Cu to have a required molar ratio were also preferable.

(Calcination Step) The mixed raw material powder was calcined under the following conditions. The calcination temperature is preferably 750 to 850 ° C, more preferably 600 to 1,000 ° C, and the calcination time is 3 to 50 hours.
As the calcining atmosphere, a gas having an oxygen (partial pressure of 20%) or a gas having an oxygen partial pressure of at least 50 ml / min or more per 1 cubic meter of the calcining furnace was maintained. By this step, calcined powder was obtained.

(Pulverizing / Drying Step) The calcined powder obtained in the calcining step was put into a ceramic spot together with a pulverizing medium such as a Zr ball and an organic solvent such as toluene, and set on a turntable to perform ball pulverization. . The purpose of this grinding is
The calcined powder is finely ground to improve uniformity,
The purpose is to increase the thermal reactivity in the subsequent firing. The slurry calcined powder that has been pulverized is dried by a dryer.

(Recalcining Step) The calcined powder that has been dried is calcined again. The calcination temperature, calcination time, and calcination atmosphere were the same as those in the first calcination step. Through this step, a recalcined powder was obtained.

(Remilling / Drying Step) The recalcined powder obtained in the recalcining step was ground and dried again. The grinding and drying conditions were the same as those of the first grinding and drying step.

(Repeating process of re-calcination, re-crushing and drying) The re-calcined powder having been dried is repeatedly subjected to the steps of re-calcination, re-grinding and drying as appropriate. An oxide superconducting synthetic powder sample was obtained.

(Measurement of Characteristics of Oxide Superconducting Synthetic Powder Sample and Measurement of Diffraction X-ray Intensity) The oxide superconducting synthetic powder sample obtained in the above-mentioned oxide superconducting synthetic powder manufacturing process was formed into a wire and the superconducting properties were measured. Simultaneously with the measurement, the relationship between the measurement result of the diffraction X-ray intensity when the oxide superconducting synthetic powder was irradiated with CuKα radiation using an X-ray diffractometer and the superconductivity was examined. As a result of this study, the present inventor has succeeded in finding the relationship between the measurement result of the diffraction X-ray intensity and the superconductivity as described below.

FIG. 1 shows the diffraction X-ray intensity of the oxide superconducting synthetic powder sample having good superconducting properties when 2θ is in the range of 17 ° to 19 °. However, FIG. 1 is a graph showing a chart in which the horizontal axis represents the diffraction angle 2θ with respect to the incident angle θ to the powder sample, and the vertical axis represents the intensity of the diffracted X-rays. The diffracted X-ray intensity is the peak of the (110) plane of Ca ₂ PbO ₄ , that is, 2θ: about 17.6 ° (hereinafter referred to as “peak”), and the peak of the (020) plane of Ca ₂ PbO ₄ , that is, 2θ: 18.1 ° (hereinafter referred to as “peak”),
And 2θ: 17.8 ° (hereinafter referred to as “peak”), having three main peaks. (However, the value of the peak value fluctuates by about ± 1% due to the difference in the type of the X-ray diffractometer, the calibration method, and the like.) Among these, the presence and intensity of the peak have a large correlation with the superconductivity of the sample. The present inventors have found that the strength of the oxide superconducting synthetic powder sample varies greatly depending on the manufacturing process, and have completed the present invention.

That is, when the above oxide superconducting synthetic powder sample is formed into a wire, when a sample in which the presence of a peak is not confirmed is formed into a wire, the critical current density is 9,600 A / cm ^2.
On the other hand, when the peak intensity is 100 and a sample having a peak intensity ratio of 3 or more is made into a wire, the critical current density shows a remarkable improvement of 31,000 A / cm ² or more. . Further, when the peak intensity is set to 100 and a sample having a peak intensity ratio of 8 or more is formed into a wire, the critical current density exceeds 35,000 A / cm ² which is practically desired, and is 37,000 A. /
cm ² or more are shown, when the ratio of the intensity is linear Zaika samples with 28, the critical current density was also found to exhibit 52,000A / cm ² or more. Here, a method of obtaining the ratio of peak to peak intensity will be described with reference to FIGS. However, FIG. 2 shows a process of calculating a peak-to-peak intensity ratio described later in FIG. First, in FIG. 1, [diffraction X-ray intensity of the peak] = peak intensity + background, [diffraction X-ray intensity of the peak] = intensity of the peak + intensity of the foot of the peak at the position of the peak + background, it is conceivable that. Here, the value of the background is the average value of the diffracted X-ray intensities in the range of 18.99 ° to 19.00 ° where 2θ does not exist. (This value is indicated by a two-dot chain line in FIG. 2.) Next, the intensity of the skirt portion of the peak at the peak position is determined by applying the Lorentz function to the peak, the peak 3 position of the function, 2θ = 17. It can be obtained by calculating the intensity at 8 °. (The value of the Lorentz function is indicated by the dotted line in FIG. 2.)
Is obtained as a part of a solid line in. That is, the peak-to-peak intensity ratio may be calculated as follows. Intensity ratio = [(Diffraction X-ray intensity of the peak-Intensity of the foot of the peak at the position of the peak-Background) / (Diffraction X-ray intensity of the peak-Background)] × 100 And the intensity of this peak is PbO. Therefore, it is considered that the presence of PbO plays an important role in the remarkable improvement of the critical current density in the present invention.

On the other hand, the peak intensity fluctuates greatly in the manufacturing process of the oxide superconducting synthetic powder sample, and if the manufacturing conditions described later are not satisfied, the sample has no peak. The oxide superconducting synthetic powder sample having the peak-to-peak intensity ratio of 3 or more is subjected to a calcination step while maintaining the flow of the gas having an atmospheric partial pressure (oxygen partial pressure of 20%) or higher. It is formed remarkably when the sample is calcined. Then, it is necessary to keep the flow of the gas at a sufficient level and to continue the flow from the start of the first calcination to the end of the last calcination. That is, it is important to keep the flow of the gas constantly when the sample is being heat-treated. Conversely, it was also found that a sample having an intensity ratio of the peak of 3 or more was not generated in a closed space where there was no exchange of atmosphere with the outside or under a flow of a non-oxidizing gas such as 100% nitrogen and 100% Ar.

The formation mechanism of the above-described oxide superconducting synthetic powder sample and the mechanism of its contribution to the superconducting properties are not completely clear, but are inferred as follows. That is, it is very difficult to convert a so-called Bi2223-based superconductor containing no Pb into a single phase into a high-temperature phase having a critical temperature of around 120 K by firing for a short time. However, it is known that this problem can be solved by adding Pb to Bi (Pb) 2223 system. On the other hand, by adding Pb, depending on the heat treatment temperature and time of the sample, C
Various Pb compounds such as a ₂ PbO ₄ , PbO, PbO ₂ , Pb ₃ O ₄ , and Pb ₂ O ₃ are formed.

Here, the existence form of the oxide superconducting synthetic powder sample is not a single phase of the Bi2223-based high-temperature phase but a Bi (Pb) 2212-based, Ca ₂ PbO ₄ , CaCu
It is constituted as a mixture of unreacted phases mainly composed of O ₂ .
The oxide superconducting synthetic powder sample composed of such an unreacted phase is filled in an Ag or Ag alloy tube, and in the process of repeating each process such as rolling, drawing, and heat treatment, Bi (Pb) 2223, which is a high temperature phase. The formation of a single phase into the system proceeds. In this process, when PbO, whose role has not been emphasized in the past, is present in a predetermined amount or more, the generation reaction of the high-temperature phase is stabilized at the interface with Ag or the Ag alloy as a matrix, and the superconducting property in this part is stabilized. Is greatly improved, and it can be considered that the formation of a single phase into the Bi (Pb) 2223 system proceeds in a favorable and nearly perfect manner in a portion other than the interface. Then, if an oxide superconducting wire is manufactured by using, for example, the PIT method using the oxide superconducting synthetic powder prepared in the above step, an oxide superconducting wire having a high critical current density can be obtained.

(Example) Bi ₂ O ₃ , PbO, SrCO ₃ , CaC having a purity of 3N or more and a median particle size of 1 to several μm
Each raw material powder of O ₃ and CuO was converted to Bi: Pb: Sr: Ca:
Cu = 1.85: 0.35: 1.90: 2.05: 3.
The components are weighed and mixed so that the composition ratio becomes 05. Next, the mixed raw material powder was calcined under the following conditions. Calcination temperature is 750
８850 ° C., calcination time is 10-20 hours, calcination atmosphere is 100% oxygen gas, and 5 l / min, 2 l, as shown in FIG.
/ Min, 1 l / min, 0.5 l / min, 0.1 l
/ Min, and 0.05 l / min, and 6 types of calcined powder were obtained. The calcined powder was put in a ceramic spot together with a grinding medium such as a Zr ball and an organic solvent (toluene), set on a rotating table, and ground with a ball, followed by drying with a dryer. In this embodiment,
This operation cycle of calcination-pulverization-drying was performed under the same conditions for 3 cycles.
This was repeated twice to obtain six types of oxide superconducting synthetic powder samples (samples 1 to 6) shown in FIG.

Next, these six types of samples were formed into wires, and their superconducting characteristics were measured. At the same time, the diffraction X-ray intensity was measured. First, measurement of superconducting characteristics will be described. 1.2 g of each of the six samples was weighed and filled into a cylindrical rubber mold having a hollow part of 3.8 mm x 95 mmL and a thickness of 10 mm. Seal both ends of the rubber mold with rubber stoppers,
After closing the gap using vinyl tape to prevent water from entering, press molding with a maximum isostatic pressure of 1.5 ton / cm ² using a cold isostatic press (CIP) to obtain about 1.95φ ×
A 90 mmL molded body was obtained. This molded body is treated with an inner diameter of 2.0
It is inserted into an Ag pipe having an outer diameter of 3.0 mmφ × 100 mmL, drawn, rolled, and then subjected to a heat treatment at 835 to 845 ° C. for a total of 150 hours. A 2 mm tape-shaped Ag-sheathed oxide superconducting wire was obtained. In this wire, the superconducting portion of the cross section has a width of about 4.0 mm and a thickness of about 0.0 mm.
7 mm. The measurement was performed using a four-terminal method, and a current value when a voltage of 1 μV / cm was generated between the voltage terminals was defined as a critical current value. The result is shown in FIG.

Next, the measurement of the diffraction X-ray intensity by the X-ray diffractometer will be described. The following conditions were set using RINT-1000 manufactured by Rigaku Corporation as an X-ray diffractometer. X-ray used: CuKα Measurement environment: tube Cu tube voltage 40 kV Sampling width 0.002 ° Scanning speed 0.050 ° Diverging slit 1/2 ° Scattering slit 1/2 ° Receiving slit 0.15mm Monochrome receiving slit 0.45mm Measurement Range: 17 to 19 ° (2θ) 4 g of each of the above six types of samples is weighed and filled into a 15 mmφ mold. Then, a sample obtained by pressurizing and compacting at a uniaxial pressure of 5 kg / cm ² was used as a sample for measuring diffraction X-ray intensity.
The measurement was performed with a line diffractometer. Figure 3 shows the measurement results.
Shown in From the measurement results, the peak intensity was 10
FIG. 5 shows the result of calculating the ratio of the peak intensities when 0 was set.
It was shown to. From the above results, when a sample having a peak intensity ratio of 3 or more was formed into a wire, the critical current density was 31,0.
It was found to show a remarkable improvement of more than 00 A / cm ² . Further, when the peak intensity is set to 100 and a sample having a peak intensity ratio of 8 or more is formed into a wire, the critical current density is 35,000 A, which is practically desired.
/ Cm ² and shows the 37,000A / cm ² or more beyond, when the ratio of the intensity is linear Zaika samples with 28, the critical current density was also found to exhibit 52,000A / cm ² or more.

(Comparative Example) Bi ₂ O ₃ , PbO, SrC
The raw material powders of O ₃ , CaCO ₃ and CuO are converted to Bi: Pb: S
r: Ca: Cu = 1.85: 0.35: 1.90: 2.
Weigh and mix to obtain a composition ratio of 05: 3.05.
Next, the mixed raw material powder was calcined under the following conditions. The calcination temperature is 750-850 ° C, the calcination time is 10-20 hours,
The calcination was performed in a closed furnace without circulation of atmosphere to the outside to obtain a calcined powder. For the obtained calcined powder, under the same conditions as in the example,
An operation cycle of calcination-pulverization-drying was repeated to obtain a comparative sample.

The comparative sample was formed into a wire in the same manner as the example sample, and the superconducting characteristics were measured. At the same time, the diffraction X-ray intensity was measured. As a result, the critical current value is 27
A, the critical current density was 9,600 A / cm ² , and the measurement result of the diffraction X-ray intensity was as shown in FIG. From the above, the peak of the (110) plane of the Ca ₂ PbO ₄ and Ca ₂
Between the peak of the PbO ₄ (020) plane and Ca ₂ PbO ₄
When the peak intensity of the (110) plane was set to 100, even if the oxide superconducting synthetic powder sample having no peak having a peak intensity ratio of 3 or more was formed into a wire, a high critical current density could not be obtained. .

[0032]

As described in detail above, the PIT method
Superconductivity such as critical current density of manufactured oxide superconducting wire
(BiPb) with the aim of improving the conductivity_TwoS
r_TwoCa _TwoCu_ThreeO_xOxide superconducting synthetic powder
Measure the diffraction X-ray intensity using CuKα radiation for the synthetic powder.
When this happens, the peak is increased from 17.75 ° to 17.85 ° in 2θ.
The use of synthetic powder characterized by having
Greatly improve the critical current density of the oxide superconducting wire
Can be realized and can reach the practical level.
Was.

[Brief description of the drawings]

FIG. 1 shows (BiPb) ₂ Sr ₂ C according to an embodiment of the present invention.
It is a graph showing a chart of measurement example of the diffracted X-ray intensity in a ₂ Cu ₃ O _x based oxide superconducting synthetic powder.

FIG. 2 shows (BiPb) ₂ Sr ₂ C according to an embodiment of the present invention.
From the measurement results of the diffracted X-ray intensity in a ₂ Cu ₃ O _x based oxide superconducting synthetic powder is a graph describing a method for determining the ratio of the peak intensity.

FIG. 3 is a graph showing a chart of an example of measurement results of diffraction X-ray intensities of oxide superconducting synthetic powder samples 1 to 6 according to an example of the present invention.

FIG. 4 shows (BiPb) ₂ Sr ₂ C according to a comparative example of the present invention.
It is a graph showing a chart of measurement example of the diffracted X-ray intensity in a ₂ Cu ₃ O _x based oxide superconducting synthetic powder.

FIG. 5 is a graph showing the relationship between the oxygen gas flow rate in the atmosphere during calcination and the peak intensity ratio of the obtained sample in the preparation of oxide superconducting synthetic powder samples 1 to 6 according to the example of the present invention.
It is a figure which shows the table | surface which described the relationship with the critical current value and critical current density of the oxide superconducting wire produced from the obtained sample.

Claims (5)

[Claims] 1. An oxide superconducting synthetic powder used in the production of a Bi-Pb-Sr-Ca-Cu-based oxide superconducting wire using Ag or an Ag alloy as a matrix, using an X-ray diffractometer. , The oxide superconducting synthetic powder
When the measurement result of the diffraction X-ray intensity at the time of irradiating the Kα ray is shown in a graph in which the vertical axis represents the diffraction X-ray intensity and the horizontal axis represents the diffraction angle, the peak of the (110) plane of Ca ₂ PbO ₄ is obtained. And Ca ₂ PbO
₄ between the (020) plane peak and Ca ₂ PbO ₄ (11
0) An oxide superconducting synthetic powder characterized in that there is a peak having a peak intensity ratio of 3 or more when the peak intensity of the plane is 100. In the irradiation device according to claim 2, wherein the CuKα line, when irradiated with a incident angle theta, the peak of the (110) plane of the Ca ₂ PbO ₄ and Ca ₂ PbO
₄ The peak existing between the peak on the (020) plane is 2θ
The oxide superconducting synthetic powder according to claim 1, wherein the powder is located at a position of 17.70 ° to 17.90 °. 3. The method according to claim ₂ , wherein the irradiation with the CuKα ray comprises adding Ca ₂
Peak of (110) plane of PbO ₄ and Ca ₂ PbO ₄ (02
2. The oxide superconducting synthetic powder according to claim 1, wherein a peak of PbO exists between the peak of the 0) plane and the peak of the PbO. 4. An oxide superconducting wire produced by using the oxide superconducting synthetic powder according to any one of claims 1 to 3 and using Ag or an Ag alloy as a matrix. 5. The method for producing an oxide superconducting synthetic powder, comprising mixing powders of a Bi compound, a Pb compound, a Sr compound, a Ca compound, and a Cu compound, and mixing the powder at a temperature of 750 to 85.
The method for producing an oxide superconducting synthetic powder according to any one of claims 1 to 3, wherein the firing is performed in an oxidizing gas flow at 0 ° C for a time of 10 to 20 hours.