JPH0237624A - Manufacture of flake-shaped oxide superconductor - Google Patents

Abstract

PURPOSE:To control the orientation of the crystal by once heating and melting a material containing the component element of an oxide superconductor with the desired composition, coagulating and cooling it in one direction from one end side of the length direction of the half-melted state or the melted state, then crushing it. CONSTITUTION:A raw material 2 containing the component element of an oxide superconductor with the desired composition is filled in a boat 1, it is heated and melted in an electric furnace 3, a cord 4 is wound on a drum 5 to move the boat 2 when the half-melted state or the melted state is attained. The raw material 2 in the melted state starts to be coagulated and cooled in one direction from the pulling side due to this shift, the raw material 2 is formed into a slender crystal structure in the length direction when it is continuously cooled to the other end. It is heat-treated at a relatively low temperature in the oxygen containing atmosphere, it is then crushed to obtain an oriented flake-shaped oxide superconductor. The axis-oriented flake-shaped oxide superconductor is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing oriented flaky oxide superconductors.

(Prior art) In the conventional manufacturing method of an oxide superconductor (striated body) made of rare earth elements, alkaline earth metals, Cu, etc., and oxygen, oxides, carbonates, etc. containing the constituent elements of the oxide superconductor are A secondary raw material powder (pre-sintered powder) obtained by weighing and mixing the primary raw materials so as to have a superconducting composition and pre-sintering them was used.

The method of obtaining a filament using this pre-sintered powder is to fill a metal pipe with the pre-sintered powder, and then subject it to plastic processing such as drawing, extrusion, rolling, and swaging to form a composite material with a desired shape and one dimension. It is generally known to produce a wire and then heat treat it in an oxygen-containing atmosphere.

In addition, conventionally, the calcined powder is compacted and then heat-treated in an oxygen-containing atmosphere to obtain a bulk body.

On the other hand, for example, the crystal structure of a YBaCuO-based superconductor has been clarified, and it is known that it is layered and current flows much more easily in the a-b plane than in the C-axis direction.

(Problem to be Solved by the Invention) However, since the crystal orientation of the calcined powder of the oxide superconductor precursor obtained by the conventional method as described above is random, There was a drawback that a molded article having a high critical current density (Jc) could not be obtained.

(Objective of the Invention) An object of the present invention is to provide a method for producing a flake-like oxide superconductor that is capable of controlling crystal orientation in the conventional oxide superconductor production method (solid phase method) of powder compaction and heat treatment. It is in.

(Means for Solving the Problems) The method for producing a flaky oxide superconductor of the present invention includes Bi
Or, after once heating and melting a substance containing constituent elements of an oxide superconductor with a desired composition consisting of rare earth elements, alkaline earth metals, copper, and oxygen, from one end in the length direction from a semi-molten state or a molten state. It is characterized by being solidified and cooled in the same direction, and then pulverized.

The method of the present invention will be explained focusing on the case of YBaCuO superconductor.

Figure 1 shows an example of unidirectional solidification and cooling. In this case, a raw material 2 containing constituent elements of an oxide superconductor with a desired composition is placed in a bowl 1-1, and then heated and melted in an electric furnace 3. do. In addition, when the raw material 2 is Y-based, the range is 950 to 1200.
It becomes a semi-molten state at about 1200°C and becomes a molten state at 1200°C or more. However, if the temperature is raised too much, the reaction with the constituent materials of the boat 1 will be intense, so it is better to keep it below 1500°C.When the raw material 2 reaches a predetermined temperature at which it is semi-molten or molten, the rope 4 is moved to the drum 5. Wind it up and move the boat l to the right side in Figure 1.

In this case, it is preferable to use a pre-fired material as the raw material 2.

The material of the boat 1 is desirably one that reacts with the raw material as little as possible, such as PT or PT gold alloy.

boat! The moving speed of can be determined as appropriate, but it is preferably about several tens of μ/S. In this case, since the temperature gradient inside the electric furnace 3 is as shown in Fig. The raw material 2 in this state begins to solidify and cool unidirectionally from the withdrawal side. When continuously cooled to the other end, the raw material 2 becomes a crystal structure elongated in the length direction. Each crystal grain has a flake shape with the length direction being the a-b plane and the thickness direction being the c-axis direction.

Next, these are heat treated at a relatively low temperature in an oxygen-containing atmosphere,
Thereafter, pulverization yields oriented flaky oxide superconductors. Note that if this unidirectional solidification and cooling operation is performed in an oxygen-containing atmosphere, flaky oxide superconductors can be obtained simply by pulverizing without subsequent heat treatment.

Heating methods are not limited to electric furnaces, for example, high frequency induction heating,
Means such as infrared heating can be used as appropriate.

In addition, in the case of YBa 2 Cu z 07-5 superconductor, it is desirable that the composition of the starting material be slightly richer in Cu or in larger amounts in Cu and Ba. The reason is Y: Ba
: When Cu is 1+2:3 (molar ratio), a different phase (YxBaCuOs) is generated during the solidification and cooling process, which tends to deteriorate the properties.

The raw material 2 of the oxide superconductor in the present invention is not limited to Y-based materials, but may also be B 1-3r-Ca-Cu-0-based materials, T2-based materials, and the like.

(Example) Using Y2O3, BaCO3, and CuO powders as raw materials
:Ba:Cu=l :2:3.5 (molar ratio). After mixing, this mixture was heated at 920℃ x 20h.
Temporary firing was carried out in r, Ot air flow (4 g/m1n). The pre-fired raw material thus obtained was heated and melted in the manner shown in FIG. 1, and unidirectionally solidified and cooled. At this time, as boat 1, l
A PT product measuring 0 mm x 5 mm (depth) x 50 mm I2 was used, and the test was carried out in 02 air flow (4 I2/m1n). Further, the moving speed of the boat 1 was set to 100 μ/S. The temperature gradient is 100°C/cm. The thus obtained bulk body was taken out and ground in an automatic mortar for 15 minutes. As a result, the thickness #
A flaky oxide superconductor with a length of 20μ and a length of lOO~300μ was obtained.

When the obtained flaky oxide superconductor was subjected to X-ray diffraction, it was confirmed that the thickness direction was the C-axis direction. Mao,
Raw materials of the same composition are heated at 950°C, 1050°C, 115°C.
The results were almost the same when unidirectional solidification and cooling was performed from a semi-molten state at 0°C, and when unidirectional solidification and cooling was performed from a molten state at 1250°C and 1350°C.

After filling this flaky oxide superconductor into an Ag vibe with an outer diameter of 10 mmΦ and an inner diameter of 5 mmΦ.

External diameter: 0.4m by swaging and groove roll rolling
It was made into a composite line of mφ. After that, it was heat-treated at 850° C. for 4 hr in a 0□ air flow (4 g/ml), and then slowly cooled at a rate of 2° C./min. When the critical current density Jc of the superconducting wire thus obtained was measured, it was found to be 18,500 A/cm"LN2
1, which was 0G, is a boat 2, a raw material 3 containing the constituent elements of the oxide superconductor is an electric furnace 4, and a rope 5 is a drum.
When it was filled into a vibrator and processed into a composite wire, and then heat treated, the Jc was 1500A/cm" L N 20
It had a low value of G.

(Effects of the Invention) According to the manufacturing method of the present invention, an axially oriented flake-like oxide superconductor can be obtained, which can be used to produce various shapes such as wire rods and thick films with improved critical current density (Jc). W4 can be easily processed and has a remarkable industrial effect.

[Brief explanation of the drawing]

Claims (1)

[Claims] A material containing constituent elements of an oxide superconductor having a desired composition is heated and melted, then solidified and cooled in one direction from one end in the longitudinal direction from a semi-molten state or a molten state, and then pulverized. A method for producing a flaky oxide superconductor.