JPH0796451B2 - Method for producing oxide superconductor composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an oxide superconducting material used in various superconducting application devices and superconducting elements.

(Prior Art) As superconducting materials, various materials such as metal element superconducting materials, compound superconducting materials, and alloy superconducting materials are known. Superconducting materials are used to make electronic devices such as Josephson devices, coils for superconducting magnets, and various sensors.

By the way, the superconducting transition temperature T above the boiling point of liquid nitrogen (77k)
It is known that Tc of LnBa ₂ Cu ₃ O _7-y having c changes by substituting Cu with a transition metal Co. This
A compound having an arbitrary Tc can be synthesized according to the substitution amount of Co, and expectations for it as a practical material for various sensors are increasing.

(Problems to be Solved by the Invention) LnBa ₂ (Cu _1-x CO _x ) ₃ O _7-y has an arbitrary Tc depending on the substitution amount of Co.
However, there is a problem that the critical current density (Jc) is generally low because of its large dependence on the magnetic field. Therefore, an object of the present invention is to provide a superconducting composition capable of changing Tc, having a small magnetic field dependency and a high Jc, and a method for producing the same.

(Means for Solving the Problems) The present invention is LnBa ₂ (Cu _1-x Co _x ) ₃ O _7-y (where n is Y, La, Nd, S).
m, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), and 0 <x ≦ 0.2 in the oxide superconductor composition.
In addition, the raw materials are adjusted so that the molar ratio of the oxide superconductor composition is −0.1 ≦ y ≦ 0.1 and the metal ion of the above composition, and high-pressure oxygen treatment is performed after firing. It is a method for producing a characteristic oxide superconductor.

(Example) As a starting material, barium carbonate (BaC
O ₃ ), yttrium oxide (Y ₂ O ₃ ), cupric oxide (Cu
O) and cobalt oxide (CoO) are used, and each is weighed so as to be in the composition range of the present invention. In YBa (Cu _1-x CO _x ) ₃ O _7-y , a single-phase composition cannot be obtained in the range of x> 0.2. Next, each of the weighed materials was wet mixed in a ball mill and then calcined at 800 to 850 ° C. This powder was crushed using a mortar, an organic binder was put therein, and the powder was sized and then pressed to prepare a disk having a diameter of 16 mm and a thickness of 1.5 mm. Next, the samples in the composition range of the present invention were sintered in oxygen at a temperature of 850 to 900 ° C. for 4 hours. This was subjected to high-pressure oxygen treatment in oxygen at 100 to 150 atm at a temperature of 300 to 400 ° C for 40 to 50 hours.

The result of measuring the value of y in the composition formula by non-dispersive infrared spectroscopy using a fired body that had been subjected to high-pressure oxygen treatment was −0.
A value of 1 ≦ y ≦ 0.1 was shown.

The resistivity was measured by the DC four-terminal method. Gold was attached to the electrodes by a sputtering method, and gold wires were used as leads.

Furthermore, the ratio of the superconducting phase at 4.2K was measured by measuring the AC susceptibility.

The AC susceptibility was measured by putting a sample in a coil and measuring the change in the L component. Change the L component of the sample to the same volume, ΔL at 4.2K of lead of the same shape at 10
It was set to 0, and the ratio of the superconducting phase was calculated. These measurements were performed from room temperature to helium temperature (4.2K).

For example, a composition of YB _a2 (Cu _0.95 Co _0.05 ) ₃ O _7-y shows a large magnetic field dependence on a magnetic field of 0.1, 1, 10 Oe as shown in FIG. However, when this was subjected to high-pressure treatment in oxygen at 100 atm, for example, the magnetic field dependence decreased and Tc rose from 60K to 80K, as shown in FIG. Moreover also Jc of 10K at a lower temperature than the Tc increases from 500A / cm ² to 900A / cm ² was confirmed.

Also, when Ln is La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, the same result as Y was obtained.

(Effects of the Invention) As described in the examples, the composition synthesized according to the production method of the present invention has less dependence on the magnetic field than the conventional material, and therefore is very practical as a superconducting material and its production method. Is.

[Brief description of drawings]

FIG. 1 is a diagram showing a temperature change of an AC susceptibility of a fired body produced by a conventional manufacturing method. FIG. 2 is a diagram showing a temperature change of the AC susceptibility during firing according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshimi Kubo, 5-33-1 Shiba, Minato-ku, Tokyo, NEC Corporation (72) Inventor, Mikio Takano 17, Uzumaya, Touramachi, Ukyo-ku, Kyoto (72) Inventor Yasuo Takeda 736-5 Kanonji-cho, Tsu-shi, Mie Prefecture (72) Toshio Takada 1 Nishisenouchi-cho, Kitashirakawa, Sakyo-ku, Kyoto-shi, Kyoto (56) Reference Japanese Patent Laid-Open No. 63-291817 (JP, 63-291817) A) Jpn. J. Appl. Phys. , Vol. 26, No. 12, P.I. L2087-L2090 (1987) Jpn. J. Appl. Phys. , Vol. 26, No. 10, P. L1667-L1669 (1987)

Claims (1)

[Claims] 1. LnBa ₂ (Cu _1-x Co _x ) ₃ O _7-y (where n is Y, L
a, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, one or more kinds, moles of metal ions having a composition represented by 0 <x ≦ 0.2 and −0.1 ≦ y ≦ 0.1) Adjust the raw materials so that the ratio becomes
After the firing, a heat treatment is carried out in high-pressure oxygen at 100 atm or higher, which is a method for producing an oxide superconductor.