JPH05229823A - Production of oxide superconducting material - Google Patents

Abstract

PURPOSE:To provide a process suitable for the mass-production of a Ba-Sr-Cu-O superconductor having high quality. CONSTITUTION:A Ba-Sr-Cu-O oxide superconducting material is produced by using the carbonate, nitrate or oxalate of Ba and Sr and the carbonate, nitrate, oxalate or oxide of Cu or metallic Cu as starting raw materials, preparing a raw material composition containing 2.25-1.1mol of the alkaline earth metal (Ba and Sr) in total based on 1mol of copper, mixing the composition and baking at 900-1050 deg.C in an atmosphere having an oxygen partial pressure of >=5atm. As an alternative method, the superconducting material is produced by calcining the above mixture at 800-900 deg.C in air or in an atmosphere having an oxygen partial pressure of <=5atm and subjecting the product to the main baking at 900-1050 deg.C in an atmosphere having an oxygen partial pressure of >=5atm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a Ba-Sr-Cu-O-based superconducting material, and more particularly to producing an oxide superconducting material capable of obtaining a high-quality superconducting material with good mass productivity Regarding the method.

[0002]

2. Description of the Related Art As a method for producing a copper oxide superconducting material containing Ba, Sr, Cu and O as main components, a method of applying an ultrahigh pressure of tens of thousands of atmospheric pressure has been known so far. (For example, M.Takano et al. Physica C, 176 (1991), p.44.
1).

However, this method has a drawback that only a small sample can be manufactured because a high pressure of tens of thousands of atmospheric pressure is applied, and the operation of the apparatus is complicated and the mass productivity is poor due to the application of an ultrahigh pressure. Although the superconductor manufactured by this method showed a decrease in resistivity at low temperature, the resistivity did not become completely zero, and the superconductivity was not very good.

[0004]

As described above, the prior art has a drawback in that a high quality Ba-Sr-Cu-O 2 superconducting material can be obtained only with low mass productivity.

An object of the present invention is to solve the problems of the prior art and to provide a method for producing a high-quality Ba-Sr-Cu-O superconductor with good mass productivity. ..

[0006]

[Means for Solving the Problems] The above-mentioned purpose is Ba-Sr-Cu.
In the production of -O superconducting materials, the starting materials are the respective carbonates, nitrates, and oxalates of Ba and Sr, and the carbonates, nitrates, oxalates, oxides, or metallic Cu of Cu, and Adjust the raw material composition so that the total molar ratio of the earth metals (Ba and Sr) is 2.25 to 1.1 times that of copper, and after mixing, in an atmosphere with an oxygen partial pressure of at least 5 atm.
To provide a manufacturing method characterized by firing in a temperature range of 0 ℃ ~ 1050 ℃, or in the production of Ba-Sr-Cu-O-based superconducting material, the respective carbonates, nitrates of Ba and Sr, Starting material is oxalate and Cu carbonate, nitrate, oxalate, oxide or metallic Cu, and the total molar ratio of alkaline earth metals (Ba and Sr) is 2.25 to copper.
After adjusting the raw material composition and mixing so that it will be from 1.2 times to 1.1 times,
800 ° C in air or in an oxygen partial pressure atmosphere of 5 atm or less
To 900 ° C. in the temperature range, and then main firing in the temperature range of 900 ° C. to 1050 ° C. in an oxygen partial pressure atmosphere of 5 atm or more. it can.

[0007]

The main feature of the present invention is that the starting material composition is adjusted so that the total molar ratio of the alkaline earth metals (Ba and Sr) is 2.25 to 1.1 times that of Cu.
In the conventional superconducting material manufacturing method, the total molar ratio of alkaline earth metals was set to 1 or less with respect to Cu, but the ratio of alkaline earth metals in the components was significantly increased. ..

As a result, the superconducting material can be manufactured under a relatively low oxygen partial pressure atmosphere of about 5 atm.

The second manufacturing method of the present invention is characterized in that
This is to form a sintered body by pre-baking in air or 1-atmosphere oxygen before main baking in an oxygen partial pressure atmosphere of 5 atm or more, and then performing main baking. As a result, handling can be simplified when mass production is performed.

[0010]

EXAMPLES Hereinafter, the method for producing the oxide superconducting material of the present invention will be specifically described with reference to Examples.

[0011]

Example 1 Starting from BaCO ₃ , SrCO ₃ and CuO, the molar ratio of Ba: Sr: Cu was 0.7: 0.6: 1 (the molar ratio of alkaline earth metal to Cu was 1.3: 1). Weigh and mix, and then mold into pellets,
It was baked at 0 ° C. for 50 hours. The temperature dependence of the resistivity of the obtained sintered body is shown in FIG. From this result, it can be seen that the resistivity starts to decrease at about 26K and becomes completely zero at 5K.

[0012]

Example 2 Starting from BaCO ₃ , SrCO ₃ and metallic Cu, the molar ratio of Ba: Sr: Cu is 1.1: 0.7: 1 (the molar ratio of alkaline earth metal to Cu is 1.8: 1). And weighed and mixed. This powder was formed into pellets at a pressure of about 1 t / cm ² , and calcined in air at a temperature of 850 ° C. for 50 hours to sufficiently react. Next, the obtained sintered body was treated with Ar80% and O ₂ 2
At a total pressure of 250 atm (oxygen partial pressure of 50 atm) in 0% mixed gas
Main firing was performed at a temperature of 1000 ° C. for 50 hours. The temperature dependence of the resistivity of the obtained sintered body is shown in FIG. From the results in the figure, it can be seen that the resistivity starts to decrease at about 40K and becomes completely zero at 24K. FIG. 3 shows the temperature dependence of the magnetic susceptibility of this sintered body during cooling in a zero magnetic field and during cooling in a magnetic field under 10 Gauss. From the results in the figure, it can be seen that at a temperature of 24 K or less, the magnetic susceptibility is negative even during cooling in a magnetic field, and superconductivity is exhibited.
In addition, when this characteristic is compared with perfect diamagnetism, the Meissner volume fraction is 5% or more at 5K, which indicates that it is a bulk superconductor.

[0013]

Example 3 _{Ba (NO 3) 2, Sr} (NO 3) 2 and _{Cu (NO 3) 2 · 3H} 2
O 2 is used as a starting material, and the molar ratio of Ba: Sr: Cu is 1 :.
Weighed and mixed to be 1: 1 (molar ratio of alkaline earth metal to Cu is 2: 1). This powder is molded into pellets at a pressure of about 1 t / cm ² , and it is heated at a temperature of 800 ° C in oxygen at 1 atm for 50
It was calcined for an hour. The obtained sintered body is crushed and mixed to obtain about 1
Reformed into pellets at a pressure of t / cm ² , Ar 90%, O ₂ 10%
In this mixed gas, under a total pressure of 1000 atm (oxygen partial pressure of 100 atm), main firing was performed at a temperature of 1050 ° C for 50 hours. The temperature dependence of the resistivity of the obtained sintered body is shown in FIG. From the results in the figure, it can be seen that the resistivity starts to decrease at about 28K and becomes completely zero at about 10K.

[0014]

Example 4 Starting from BaC ₂ O ₄ , SrC ₂ O ₄ and CuO, the molar ratio of Ba: Sr: Cu is 0.8: 0.7: 1 (the molar ratio of alkaline earth metal to Cu is 1.5: 1). Weighed and mixed so that This powder was formed into pellets at a pressure of about 1 t / cm ² and pre-baked in oxygen at 4 atm at a temperature of 900 ° C. for 50 hours. The resulting sintered body was heated at a temperature of 1000 ° C under a total pressure of 250 atm (oxygen partial pressure of 50 atm) in a mixed gas of 80% Ar and 20% O _2.
Main firing was performed for 0 hours. The temperature dependence of the resistivity of the obtained sintered body is shown in FIG. From this result, it can be seen that the resistivity starts to decrease at about 35K and becomes completely zero at about 20K.

[0015]

As described above, by using the manufacturing method of the oxide superconducting material as the manufacturing method of the constitution of the present invention, the problems that the prior art had are solved and the oxygen partial pressure of 5 is obtained.
The superconducting material can be produced under a relatively low pressure of about 100 atm to 100 atm, which is advantageous in that it is simple and can be mass-produced.

Further, according to the method of the present invention,
A high quality superconducting material having a resistivity of 0 can be easily manufactured.

[Brief description of drawings]

FIG. 1 shows that the molar ratio of Ba: Sr: Cu in Example 1 is 0.7: 0.6:
The figure which shows the temperature dependence of the resistivity of the sintered compact sample of No. 1.

FIG. 2 shows a Ba: Sr: Cu molar ratio of 1.1: 0.7: in Example 2.
The figure which shows the temperature dependence of the resistivity of the sintered compact sample of No. 1.

FIG. 3 is a diagram showing temperature dependence of magnetic susceptibility of a sintered body sample of Example 2.

4 is a molar ratio of Ba: Sr: Cu in Example 3 of 1: 1: 1.
FIG. 6 is a graph showing the temperature dependence of the resistivity of the sintered body sample of FIG.

FIG. 5: The Ba: Sr: Cu molar ratio of Example 4 is 0.8: 0.7:
The figure which shows the temperature dependence of the resistivity of the sintered compact sample of No. 1.

Claims (2)

[Claims] 1. In the production of a Ba-Sr-Cu-O-based superconducting material, Ba, Sr carbonates, nitrates, and oxalates of Cu and carbonates, nitrates, oxalates, and oxides of Cu, respectively. Or the metal Cu as the starting material and the alkaline earth metal (Ba
And Sr), the raw material composition is adjusted so that the total molar ratio is 2.25 to 1.1 times that of copper, and after mixing, the temperature range is 900 ° C to 1050 ° C in an oxygen partial pressure atmosphere of 5 atm or more. A method for producing an oxide superconducting material, which comprises firing at. 2. In the production of a Ba-Sr-Cu-O superconducting material, each of Ba and Sr carbonates, nitrates and oxalates, and Cu carbonates, nitrates, oxalates and oxides. Or the metal Cu as the starting material and the alkaline earth metal (Ba
And Sr), the raw material composition is adjusted so that the total molar ratio is 2.25 to 1.1 times that of copper, and after mixing, 800 ° C to 900 ° C in air or in an oxygen partial pressure atmosphere of 5 atm or less. A method for producing an oxide superconducting material, which comprises calcining in a temperature range of 1 to 5 and then performing main firing in a temperature range of 900 ° C. to 1050 ° C. in an oxygen partial pressure atmosphere of 5 atm or more.