JP3157184B2 - Manufacturing method of high-density oxide superconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a composition represented by the formula Sm ₁ Ba ₂ C
The present invention relates to a method for producing a high-density oxide superconductor having a crystalline substance phase represented by u ₃ O _7-x as a main phase.

[0002]

_2. Description of the Related Art Conventionally, the composition formula Sm ₁ Ba ₂ Cu ₃ O
_In general, the following three methods are known as methods for producing a bulk oxide superconductor of a crystalline material phase represented by _7-x . In the first method, first, Sm ₁ Ba ₂ Cu ₃ O _7-x
, Sm ₂ O ₃ , BaCO ₃ and CuO powder are mixed at a predetermined ratio. After sintering this mixed powder at about 950 ° C. to 1000 ° C., it is pulverized to produce Sm ₁ Ba ₂ Cu ₃ O _7-x powder. Next, the prepared Sm ₁ Ba ₂ Cu ₃ O _7-x
A sintering method in which powder is press-molded and the molded body is fired at about 1000 ° C. to obtain an Sm ₁ Ba ₂ Cu ₃ O _7-x phase bulk body.

A second method is to use Sm ₁ Ba ₂ Cu ₃ O _7-x
Of Sm ₂ O ₃ , BaCO ₃ and CuO powder mixed at a predetermined ratio as a raw material of Sm ₁ Ba ₂ Cu ₃ O
_{The 7-x} powder is put into a platinum crucible and melted at 1400 ° C or higher. After melting, the melt is rapidly cooled, and the obtained sintered body is pulverized and press-molded. Next, this molding is fired at 1100 ° C. to 1200 ° C., and the peritectic reaction is allowed to proceed by slow cooling from 1100 ° C. or lower to obtain a Sm ₁ Ba ₂ Cu ₃ O _7-x phase bulk body. . The third method is Sm ₁ Ba ₂ Cu ₃ O
_7-x powder is press-molded, and the obtained molded body is heated to 1100 ° C.
It is fired at 1200 ° C. and decomposed into a Sm ₂ Ba ₁ Cu ₁ O ₅ phase and a liquid phase. Next, these are gradually cooled from 1100 ° C. or lower to allow the peritectic reaction to proceed, and to make Sm ₁ Ba ₂ Cu ₃ O _7-x
A partial melting method of obtaining a phase bulk body.

[0004] However, according to the sintering method and the partial melting method, the crystal grain size of the manufactured Sm ₁ Ba ₂ Cu ₃ O _7-x phase bulk material is determined by the raw material powder used. , That is, a high-density crystal could not be obtained. Further, according to the melting method, there is an industrial problem because it requires a severe step of melting the raw material powder at 1400 ° C. or higher and rapidly cooling the melt.

[0005]

An object of the present invention is to solve the above-mentioned problems of the prior art and to grow an Sm ₁ Ba ₂ Cu ₃ O _7-x phase bulk body having a large crystal grain size by a simple method. It is an object of the present invention to provide a method for producing an Sm ₁ Ba ₂ Cu ₃ O _7-x phase oxide superconducting bulk material that can be obtained.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and found that Sm ₂ O ₃ and Ba
₃ Cu ₅ a O _x mixed, 1100 ° C. those molded to 1200
After sintering at 1100 ° C. to increase the density, the mixture is gradually cooled from 1100 ° C. or lower to obtain an Sm ₁ Ba ₂ Cu ₃ O _7-x phase oxide superconducting bulk body comprising crystal grains which are significantly larger than those of the conventional method. Was obtained, and the present invention was able to be achieved.

That is, the present invention firstly provides a composition formula Sm
₁ is a method for producing an oxide superconductor having a crystalline material phase represented by ₁ Ba ₂ Cu ₃ O _7-x as a main phase, wherein a Ba compound as a raw material powder and a Cu compound are mixed at a predetermined ratio, The mixed powder is calcined and then pulverized.
m ₂ O ₃ was mixed and press molded at 1100 ° C.
Sm ₂ Ba ₁ Cu ₁ by firing at １1300 ° C.
The coexistence state of the O ₅ phase and the liquid phase is formed to increase the density,
The peritectic reaction is advanced by slow cooling after firing, and Sm ₁
A method for producing a high-density oxide superconductor, characterized by producing a bulk substance of a crystalline substance phase represented by Ba ₂ Cu ₃ O _7-x .

[0008] Secondly, the present invention is the production method according to the first aspect, wherein the slow cooling after firing is performed from 1100 ° C. or lower. In addition, BaCO ₃ , BaO, B
aO ₂ or Ba (NO ₃ ) ₂ ;
uO, Cu ₂ O or Cu _{(NO 3)} 2, as the Sm compound _{Sm 2 O 3, Sm (NO} 3) 3 · 5H 2 O or _{Sm 2 (C 2 O 4)} 3 · 10H 2 O , etc. be used Can be.

In the present invention, Sm ₁ B is gradually cooled from a firing temperature.
When growing the a ₂ Cu ₃ O _7-x phase, during the 1000 ℃ ~1080 ℃ more preferable that slow cooling at 0.5 ℃ / h~1 ℃ / h.

[0010]

According to the present invention, a bulk superconducting oxide having a main phase of 123 phase having a large crystal grain size is obtained by crystallizing a high-density body having a main phase of 211 phases. That is, by firing the molded body of the raw material powder at 1100 ℃ ~ 1300 ℃,
The 123 phase in the raw material powder is decomposed into a 211 phase and a liquid phase and densified, and this high-density body is gradually cooled in a furnace with a predetermined temperature gradient to control the growth of crystal faces and increase the coarseness. It is trying to make it.

If the firing temperature in the present invention is 1100 ° C. or lower, the 123 phase cannot be decomposed into 211 phase and the liquid phase. If the firing temperature is 1300 ° C. or higher, the liquid phase exudes and the shape is maintained. Can not be done.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by the following examples.

[0013]

Embodiment 1 One embodiment of the method for producing an oxide superconductor of the present invention will be described below.

As raw material powder, Sm ₂ O having an average particle size of 3 μm
_Three powders, BaO and CuO powders having an average particle diameter of 1 μm were prepared, and these were mixed at a ratio of Sm: Ba: Cu = 1.4: 2.2: 3.2. Next, the mixed powder was press-molded under a pressure of ² t / cm ² to obtain a pellet having a diameter of 2 inches and a thickness of 1 cm. The pellet was fired and cooled by the following program. First, heat so as to increase by 20 ° C. per minute, and when it reaches 1200 ° C., hold it at 1200 ° C. for 40 minutes, and then cool so as to decrease by 10 ° C. per minute.
When the temperature dropped to 00 ° C., the cooling rate was changed so as to decrease by 0.5 ° C. per hour, and when the temperature dropped to 960 ° C., the cooling rate was changed so that the temperature dropped by 10 ° C. per hour, and the temperature was cooled to room temperature. The temperature changes in the above program are all linear. By firing and cooling in this way, the peritectic reaction proceeds, and Sm ₁ Ba
An oxide superconducting bulk having a ₂ Cu ₃ O _7-x phase as a main phase was obtained. Sm ₁ Ba ₂ Cu ₃ O in the obtained bulk body
_{When the 7-x} grain size was measured, the height x width x height was 3mm x
The size was about 3 mm × 3 mm.

[0015]

Embodiment 2 Another embodiment of the method for producing an oxide superconductor of the present invention will be described below.

First, as a raw material powder, B having an average particle size of 1 μm
aCO ₃ and CuO were prepared, and these were converted to Ba: Cu =
Mix at a ratio of 1.0: 1.2 and mix this powder at 850 ° C for 10
Baked at 880 ° C. for 20 hours. After sintering, the obtained sintered body was pulverized to an average particle size of 1 μm, and Sm ₂ O ₃ powder having an average particle size of 1 μm was added to this powder with Sm: Ba: Cu =
The mixture was mixed at a ratio of 1: 1: 1.2. This mixed powder was prepared in Example 1.
A pellet was obtained in the same manner as described above, and the pellet was fired and cooled by the following program. First, heat to increase by 20 ° C per minute, and when it reaches 1250 ° C, keep it at 1250 ° C for 30 minutes, then 20 ° C per minute
Cool down at a rate of 1080 ° C, and change the cooling rate to 0.8 ° C per minute when the temperature drops to 1080 ° C.
When the temperature further decreased to 1000 ° C., the temperature was changed to 20 ° C. per minute, and the cooling rate was changed to cool to room temperature. The temperature changes in the above program are all linear. By firing and cooling in this way, the peritectic reaction was allowed to proceed to obtain an oxide superconducting bulk having a Sm ₁ Ba ₂ Cu ₃ O _7-x phase as a main phase.

Sm ₁ Ba ₂ Cu _{3 in the} obtained bulk body
When the O _7-x grain size was measured, the height × width × height was 10 mm
The size was about 10 mm x 3 mm.

[0018]

Embodiment 3 Another embodiment of the method for producing an oxide superconductor of the present invention will be described below.

In this embodiment, Sm ₂ O having an average particle size of 1 μm is used.
₃ An oxide superconductor Sm ₁ Ba ₂ Cu was prepared in the same manner as in Example 2 except that samarium oxalate was used instead of the powder.
An oxide superconducting bulk having a ₃ O _7-x phase as a main phase was obtained.

Sm ₁ Ba ₂ Cu _{3 in the} obtained bulk body
When the O _7-x grain size was measured, the height × width × height was 10 mm
The size was about 10 mm x 3 mm.

[0021]

Comparative Example As a comparative example of the present invention, an oxide superconductor was manufactured by a conventional manufacturing method, and its characteristics were examined.

Sm ₂ O having an average particle size of 1 μm as a raw material powder
₃ , BaO and CuO powders are prepared, and these are Sm:
The mixture was mixed at a ratio of Ba: Cu = 1.4: 2.2: 3.2. Next, the mixed powder was calcined at 900 ° C. for 10 hours, and then kept at 980 ° C. for 20 hours to prepare Sm ₁ Ba ₂ Cu ₃ O _7-x powder. Then, the powder was press-molded under a pressure of ² t / cm ² to obtain a pellet having a diameter of 2 inches and a thickness of 1 cm. The pellet was fired and cooled by the following program. First, it was baked at 1030 ° C. for 20 hours, and then cooled so as to decrease by 1 ° C. every hour. The temperature changes in the above program are all linear. By firing and cooling in this way, the peritectic reaction proceeds, and Sm
An oxide superconducting bulk having a ₁ Ba ₂ Cu ₃ O _7-x phase as a main phase was obtained. Sm ₁ Ba ₂ Cu in the obtained bulk body
_{When the 3} O _7-x grain size was measured, the length, width, and height were mm
The unit size could not be confirmed.

[0023]

According to the development of the present invention, it has become possible to produce an oxide superconductor having crystal grains which are significantly larger than those of an oxide superconductor produced by a conventional method. In addition, the present invention has a very high commercial value because it includes simple steps.

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Claims (2)

(57) [Claims] 1. A method for producing an oxide superconductor having a crystalline substance phase represented by a composition formula Sm ₁ Ba ₂ Cu ₃ O _7-x as a main phase, comprising a Ba compound and a Cu compound as raw material powders. Are mixed at a predetermined ratio, and the mixed powder is calcined and then pulverized. The powder obtained is further mixed with Sm ₂ O ₃ , and the press-molded body is calcined at 1100 ° C. to 1300 ° C. ₂ Ba ₁ Cu ₁ O ₅ phase and a liquid phase are formed together to form a coexistence state, and the density is increased. After baking, the peritectic reaction is advanced by slow cooling , and Sm ₁ Ba ₂ Cu ₃ O _7-x is used. A method for producing a high-density oxide superconductor comprising producing a bulk body of a crystalline substance phase represented by the formula. 2. The method according to claim 1, wherein the slow cooling after firing is performed from 1100 ° C. or lower.