KR0144718B1 - Method for manufacturing y-super conductor - Google Patents

Abstract

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Description

Method of manufacturing Y-based high temperature superconductor

1 shows the crystal structure of the Y-Ba-Cu-O-based high-temperature superconductor, where a is a tetragonal structure, b is a tetragonal structure,

The second turning is a graph showing the relative density of YBa ₂ Cu ₃ O _x (Relative Intensity) on the time of the synthesis in YBa ₂ Cu ₃ O _x high-temperature superconductor based synthesis each helium, oxygen, air atmosphere, 850 ℃.

The present invention relates to a method for synthesizing a YBa ₂ Cu ₃ O _x system high temperature superconductor, and more particularly, characterized in that the heat treatment is carried out in an inert gas nitrogen or helium atmosphere.

In general, YBa ₂ Cu ₃ O _x -based high-temperature superconductor has two crystal structures according to the amount of oxygen, that is, orthorhombic structure when the amount of oxygen is x6.5, and tetragonal when x≤6.5. ) Has a structure. Y-Ba-Cu-O-based high-temperature superconductor is a single-phase compound having a composition ratio of cations of Y: Ba: Cu = 1: 2: 3, and the composition formula is YBa ₂ Cu ₃ O _x , which makes bulk of the high temperature superconductor. The amount of oxygen in time varies from x = 6.0 to x = 7.0 depending on temperature and oxygen partial pressure.

Therefore, since the YBa ₂ Cu ₃ O _x system high temperature superconducting 123 phase has a tetragonal structure, a method of obtaining 123 pairs by heat treatment in an air or oxygen atmosphere has been used. That is, conventionally, the synthesis was heat-treated in an air or oxygen atmosphere for 20 hours at 900 ℃ and sintering for 20 hours at 950 ℃.

However, the inventors of the present invention promote the formation rate and grain growth of the YBa ₂ Cu ₃ O _x system 123 phase _by performing heat treatment in nitrogen or helium atmosphere, which is an inert gas, than in the air or oxygen atmosphere, which is a conventional method. It can be lowered, found to achieve densification to complete the present invention.

That is, the 123 phase of YBa ₂ Cu ₃ O _x system has a tetragonal structure regardless of the atmosphere at 850 ℃. As the oxygen partial pressure decreases, the equilibrium oxygen content of the 123 phase decreases, increasing the number of oxygen vacancies of the tetragonal structure. The unit volume also increases. As shown in FIG. 1, in the tetragonal structure of 123 phase, the four sides of the base surface become a place where oxygen atoms can enter, so if the air or oxygen atmosphere used for heat treatment in the conventional method is changed to helium or nitrogen atmosphere, the tetragonal structure The concentration of oxygen vacancies at the base of is increased and the diffusion of material through the oxygen vacancies is much easier.

In addition, when the amount of oxygen in the phase 123 is changed from x = 7.0 to x = 6.0, the oxidation number of Cu ions is +2.33 to +1.06, thereby increasing the effective radious of Cu ions.

In other words, as the amount of oxygen in the steel 123 decreases, the volume of the tetragonal structure increases, which facilitates the diffusion of the material. Therefore, the present invention can easily perform synthesis and sintering of the Y-based superconductor by using helium or nitrogen atmosphere, which is an inert atmosphere instead of air or oxygen atmosphere, and can lower the synthesis and sintering temperature.

In the high temperature superconductor of the present invention, YBa ₂ Cu ₃ O _x was used as a basic composition to prepare a specimen using a solid phase method of a ceramic process. That is, Y ₂ O ₃ (99.9%), BaCO ₃ (99%), CuO (99.9%) were weighed in a molar ratio and then used for 4 hours using a Taflon Jar in a planetary mill. Mixed.

At this time, acetone was used as a solvent, and YTZ ball was used as a medium. The dried powder was synthesized in nitrogen or helium atmosphere at 830-850 ° C. for 5-10 hours, and then heat-treated at 450 ° C. for 30 minutes, and then the dried calcined powder was dried in a press 12 mm in diameter and thickness 2 It was molded to mm and sintered at 840 to 860 ° C. for 5 to 10 hours in nitrogen or helium atmosphere, and then heat-treated at 600 ° C. oxygen atmosphere for 4 hours.

The effects of the conventional heat treatment method and the heat treatment method of the present invention in the production of YBa ₂ Cu ₃ O _x high temperature superconductor can be seen from the following experiment.

Experimental Example 1

Relative density of YBa ₂ Cu ₃ O _x phase according to the change of synthesis time when Y ₂ O ₃ , BaCO ₃ and CuO were weighed in molar ratio, mixed and dried, and the dried powder was synthesized at 850 ° C. under helium, oxygen and air atmosphere, respectively. Was measured.

Relative intensity was determined using the following equation after measuring the height of the diffraction line with the largest intensity among the diffraction lines of each material.

Relative Density = I ₁₂₃ / (I ₁₂₃ + I _Y + I _B + I _C )

I ₁₂₃ : XRD line at 2θ = 32.88 °

I _Y : XRD line at 2θ = 29.35 °

I _B : XRD line at 2θ = 24.0 °

I _C : XRD diffraction line at 2θ = 39.0 °

As a result, as shown in FIG. 2, it can be seen that the relative density is higher in the helium atmosphere than in the air or oxygen atmosphere, indicating that the 123 phase is synthesized faster than in the existing atmosphere at the same synthesis temperature Rather, the synthesis temperature can be lowered.

Experimental Example 2

After weighing Y ₂ O ₃ , BaCO ₃ , CuO in a molar ratio, in each of the atmospheres shown in Table 1, calcining at 830-850 ° C., sintering at 840-860 ° C. and heat treatment at 600 ° C. were carried out. Got.

Each specimen was subjected to a levitation experiment in a general manner and the results and the Tc of each specimen were measured and listed in Table 1.

As can be seen from the description of Table 1, when the atmosphere of calcination and sintering in the helium atmosphere it can be seen that the result of the reversal is very good and a high Tc specimen can be prepared. Therefore, it was found that the high temperature superconductor produced by the method of the present invention is superior to the high temperature superconductor produced by the conventional method.

As described above, by changing the air or oxygen atmosphere to an inert atmosphere nitrogen or helium at the time of manufacturing the high temperature superconductor of the Y-based, the synthesis and sintering temperatures are 830-850 ° C and 840- It can be lowered to 860 ℃, in the same synthesis and sintering degree 123 phase can be synthesized faster than in the conventional atmosphere, and the densification and grain growth of the sintered specimen is promoted.

Claims (2)

YBa ₂ Cu ₃ O _{x A method} for producing a high temperature superconductor, wherein the calcination and sintering process is performed in an inert atmosphere of a helium or nitrogen atmosphere. The method according to claim 1, wherein the synthesis and sintering are performed for 5 to 10 hours at 830 to 850 캜 and 840 to 860 캜, respectively.

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