JP2003277199A - METHOD FOR PRODUCING Bi-BASED OXIDE SUPERCONDUCTING WHISKER - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the growth speed of a whisker is low in a conventional production method for a Bi-based oxide superconducting whisker, in which Al is generally added to only its raw material. <P>SOLUTION: A method for producing the Bi-based oxide superconducting whisker is characterized by including a process for melting an oxide raw material having a composition of Bi-Sr-Ca-Cu-Al, a process for rapidly cooling the obtained melt by allowing the melt to flow on an iron plate on which an Al<SB>2</SB>O<SB>3</SB>powder is sprayed beforehand and putting the melt between the iron plate and another iron plate, and a process for heat treating the rapidly cooled glassy body obtained. The whisker is obtained at an extremely high growth speed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a Bi-based oxide superconducting whisker.

[0002]

2. Description of the Related Art Bi-based superconducting whiskers have excellent crystallinity and are excellent in examining the characteristics and structure of Bi-based superconductors. As a conventional method for producing a Bi-based oxide superconducting whisker, there is a method of adding Al only to a raw material and quenching a melt of the raw material to heat-treat a glassy quenched body.

In Japanese Patent Laid-Open No. 6-92799, B
An oxide raw material having a composition of i-Sr-Ca-Cu-Al is melted, and the melt is rapidly cooled to obtain a quenched body and a precursor substance which becomes Al ₂ O ₃ after heat treatment are mixed substantially uniformly. , A method of heat treating the mixture is shown.

[0004]

According to the above conventional method, only whiskers having a low growth rate can be obtained. Then, the subject of this invention is providing the manufacturing method of Bi type oxide superconducting whisker which can obtain a whisker with a growth rate higher than before.

[0005]

In order to solve the above-mentioned problems, a method for producing a Bi-based oxide superconducting whisker according to claim 1 is an oxide raw material having a composition of Bi-Sr-Ca-Cu-Al. The step of melting, the step of pouring the obtained melt on an iron plate on which Al ₂ O ₃ powder has been sprayed beforehand, and quenching by sandwiching it with another iron plate, and the obtained glass-quenched body A heat treatment step.

Further, in the method for manufacturing the Bi-based oxide superconducting whiskers according to claim 2, the heat treatment step of the glass quenching body according to claim 1 is performed at an oxygen flow rate of 20 to 200 ml / min.
It is characterized in that it is performed in a temperature range of 00 to 1000 ° C.

The present invention is most characterized in that an oxide raw material melt having a composition of Bi-Sr-Ca-Cu-Al is poured onto an iron plate on which Al ₂ O ₃ powder has been sprinkled.
As a result, Al ₂ O ₃ is planted on the surface of the quenched body.

The method of quenching the obtained melt is arbitrary, but it is necessary that most of the melt becomes a glassy solidified product by quenching. A small amount of crystals may be mixed into the glass-like solidified product, but the smaller the amount of crystals, the better.

Although any method may be used for heat-treating the quenched glass body, the heat treatment is performed in an oxygen atmosphere in the embodiment of the present invention. Further, at that time, the oxygen flow rate is 20 to 200.
ml / min is preferred.

The temperature of the heat treatment can be arbitrarily selected according to the composition ratio of the composition and the like, but it is 800 to 1000.
When the temperature is set to ° C, whiskers are easily formed. A more preferable temperature is 860 to 880 ° C, and a particularly preferable temperature is 867 ° C.

Al ₂ O ₃ powder has a thickness of 50 μm to 0.01 μm.
It is desirable to include the particle size in the range of.

Bi-based oxide superconducting whiskers include
There are 2212 phases and 2212 phases mixed with 2223 phases. Further, the 2212 phase whiskers can be further converted into the 2223 phase by further heat treatment.

It is considered that by adding Al ₂ O ₃ to the raw material and directly adding Al ₂ O ₃ to the surface of the glass quenching body when manufacturing the quenching body, a base on which whiskers easily grow is formed. To be

[0014]

EXAMPLES Examples of the present invention will be described below.

Bi ₂ O ₃ (purity 98%), SrCO ₃ (purity 95%), CaCO ₃ (purity 99.5%), CuO
(Purity of 90%) and Al ₂ O ₃ (Purity of 99.9%) are mixed to prepare a composition of Bi: Sr: Ca: Cu: Al = 1:
A raw material powder having a ratio of 1: 1: 2: 0.75 was obtained. This raw material powder was melted at 1100 ° C. for 30 minutes. The obtained melt was poured onto an iron plate previously sprayed with Al ₂ O ₃ ,
A glass quenching body was produced by quickly sandwiching it with another iron plate. Whiskers were obtained by putting this glass-quenched body in an electric furnace in an oxygen atmosphere and heat-treating it at 850 to 900 ° C. for 24 hours. A more preferable heat treatment temperature is 860 to 880 ° C, and a particularly preferable temperature is 867 ° C.

Comparative Examples 1 and 2 are shown below for reference.

Comparative Example 1 Using the material powder of the example, Al ₂
O ₃ without adding, to prepare a previous glass quenching body was subjected to heat treatment using a glass quench body sprinkled Al ₂ o ₃ powder on its glass quenching thereof. As a result, no growth of whiskers was observed. From this, when manufacturing the glass quenching body
The point of the present invention is to implant the l ₂ O ₃ powder inside the glass quenching body.

Comparative Example 2 A material other than Al ₂ O ₃ was blended in the raw materials of Example to obtain a composition of B.
A raw material powder having i: Sr: Ca: Cu = 1: 1: 1: 2 was obtained. A quenched glass body was produced under the same conditions as in the example, and heat-treated. Then, whiskers having a high growth rate, though inferior to the examples, grew.

Critical temperature of whiskers obtained in Examples
(Tc) is about 8 as a result of measurement by resistance temperature characteristics.
It was 0K. Also, the superconducting phase is 110K phase (Bi₂S
r₂Ca ₂Cu₃) And 80K phase (Bi₂Sr₂CaCu₂)
The abundance ratio from the resistance temperature characteristics is 110K phase: 80
Phase K = 100: 1. Obtained whisker criticality
Current density is different, but about 10^FourA / cm²And
It

[0020]

According to the method for producing the Bi-based oxide superconducting whiskers of the present invention, whiskers having a higher growth rate and a higher critical current density Jc can be obtained.

That is, the growth rate was 0.1 mm / h or less in the method in which Al ₂ O ₃ was not sprayed on the surface of the quenched body, but was 0.3 mm / h in the present invention.

The critical current density Jc is 1 × 1 in the present invention.
It was 0 ⁴ A / cm ² or more (60 K).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme coat (reference) H01B 13/00 565 H01B 13/00 565D F term (reference) 4G047 JA02 JA06 JC10 KC05 LA02 LB04 4G048 AA05 AB01 AB06 AC04 AD01 AE05 4G077 AA04 BC58 CA04 CA08 JA01 JB02 JB07 5G321 AA05 CA04 DB01 DB17 DB31 DB47

Claims (2)

[Claims] 1. A step of melting an oxide raw material having a composition of Bi-Sr-Ca-Cu-Al, and pouring the obtained melt on an iron plate on which Al ₂ O ₃ powder has been previously sprayed. A method for producing a Bi-based oxide superconducting whisker, which comprises a step of quenching by sandwiching it with another iron plate and a step of heat-treating the obtained quenched glass body. 2. The step of heat-treating the quenched glass body is 800 to 1000 ° C. at an oxygen flow rate of 20 to 200 ml / min.
2. The Bi according to claim 1, wherein
-Based oxide superconducting whisker manufacturing method.