JP2773482B2 - Manufacturing method of oxide superconducting material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to Tl-Bi-Ca-
The present invention relates to a method for producing an Sr—Cu—O-based superconducting material.

[0002]

2. Description of the Related Art In recent years, ceramic superconducting materials, that is, oxide superconducting materials, have attracted attention as superconducting materials exhibiting higher critical temperatures. Among them, Tl (thallium) is a material showing the highest critical temperature of about 120 K among the currently known superconducting materials, and the practical use of this material is expected.

[0003] Among such Tl-based superconducting materials, Tl
-The composition ratio of the Bi-Sr-Ca-Cu-O system is Tl.
(+ Bi): Ca: Sr: Cu is about 1: 2: 2: 3
It is known that there are a superconducting phase of 1223 phase, and a superconducting phase of 1122 phase having a composition ratio of about 1: 1: 2: 2. The 1223 phase superconducting phase is
It shows a higher critical temperature than the 1122 phase superconducting phase.

[0004] Therefore, in order to obtain a high critical temperature, an oxide or a carbonate of each metal is mixed and sintered at a compounding ratio such that it becomes such a 1223 phase. Since Tl is an element having a high volatility, it is general to set the blending composition ratio in a larger amount than the superconducting composition ratio.

[0005]

However, in such a conventional manufacturing method, a desired superconducting phase of 122 is required.
It is known that in addition to the three phases, a significant proportion of the 1122 phases are formed.

An object of the present invention is to provide a Tl-Bi capable of generating more superconducting phases having a high critical temperature.
An object of the present invention is to provide a method for producing a -Ca-Sr-Cu-O-based superconducting material.

[0007]

According to the production method of the present invention, the composition of each element is Tl: Bi: Ca: Sr:
When expressed as Cu = a: b: c: d: 2 (molar ratio),
1.0 <a <2.0, 0.1 <b <0.6, 0.6 <c
From the raw materials satisfying <1.4, 1.6 <d <2.4, (Tl _{1 -x} , Bi _x ) Ca _U S at a critical temperature of 60 K or more
r _V Cu _W O _Z (where x, u, v, w and z are
0.1 <x <0.5, 0.6 <u <1.4, 1.6 <v
First, a superconductive phase of 1122 phases represented by the composition of <2.4, 1.6 <w <2.4, and 5 <z <9 is satisfied) is generated.

Next, Ca: C is used per mole of the 1122 phase.
u: Tl = f: g: h (molar ratio) (where f, g and h are 0.8 <f <1.2, 0.8 <g <1.2 and 0.1 <h < 1.0)
a, was added Cu and Tl, the critical temperature 100K _{higher, (Tl 1 - x, Bi} x) Ca U Sr V Cu W O
_Z (where x, u, v, w and z are 0.1 <x <
0.5, 1.6 <u <2.4, 1.6 <v <2.4,
A superconducting phase of 1223 phase represented by the composition of 2.6 <w <3.4, and 7 <z <11, respectively) is generated.

[0009]

According to the production method of the present invention, a 1122 phase superconducting phase is first generated from a raw material having a specific composition, and Ca, Cu and Tl are converted into a mixture of oxides or carbonates or a calcined powder of the mixture. In addition, a superconducting phase of 1223 phase is generated. According to the manufacturing method of the present invention, a superconducting phase of 1223 phases can be generated in a larger ratio than in the conventional manufacturing method. Therefore, according to the manufacturing method of the present invention, a Tl-based oxide superconducting material having a higher critical temperature can be manufactured.

[0010]

According to the present invention, a superconducting phase of 1223 phase having a high critical temperature can be produced in a larger proportion. Therefore, a Tl-based oxide superconducting material having a high critical temperature as a whole can be obtained.
The possibility of practical use of the oxide superconducting material can be enhanced.

[0011]

EXAMPLE First, as shown in the third, fourth and fifth rows of Table 1, the weights were weighed so that the ratios of Sr, Ca and Cu were obtained, mixed, and then pelletized. ° C
For 24 hours.

This is crushed, weighed again so as to have a ratio as shown in the first to fifth columns, and after mixing,
It was pelletized, sealed in an Au capsule, and sintered at 850 ° C. After sintering, this was pulverized into powder. This is a powder.

In addition to the above powder, the sixth powder in Table 1
Each raw material was weighed at the ratio of Ca and Cu shown in the row and the seventh row, mixed, pelletized, and sintered at 800 ° C. for 24 hours. After sintering, this was pulverized into powder.
This is a powder.

The powder was added to the powder so as to have a ratio as shown in Table 1, and the Tl oxide powder was weighed such that the Tl became the same as the mole number shown in the eighth example of Table 1. To mix and pelletize. After encapsulating these pellets in Au capsules, they were sintered at 880 ° C.
Three phases were obtained.

FIG. 1 shows the temperature dependency of the magnetic susceptibility of the thus obtained sintered body. FIG. 2 shows an X-ray diffraction pattern obtained by pulverizing the obtained sintered body and analyzing the powder by X-ray diffraction.

As shown in FIGS. 1 and 2, the obtained superconducting phase has a lattice constant a = 3.8 ° and C = 15.3 °.
It can be seen that it is almost single-phased into 1223 phases represented by. In FIG. 2, the indexed value indicates the peak of the 1223 phase, and the arrowed value indicates the peak of the 1122 phase.

Hereinafter, the samples of Nos. 2 to 11 shown in Table 1 also generate a superconducting phase in the same manner as described above.
The result was that the single phase was substantially converted into 223 phases.

[0018]

[Table 1]

For comparison, the conventional direct synthesis method used
23 superconducting phases were produced. SrCO ₃ : CaC
It was weighed so that O ₃ : CuO = 2: 2: 3, mixed, pelletized, and sintered at 800 ° C. for 24 hours.
This is crushed to obtain Tl ₂ O ₃ : Bi ₂ O ₃ : SrC
O ₃ : CaCO ₃ : CuO = 1.6: 0.4: 2: 2:
3 and weighed and mixed, then pelletized to A
and sealed at 880 ° C.

FIG. 3 shows an X-ray diffraction pattern of the sample thus obtained. As shown in FIG. 3, the obtained sample was found to contain a considerable amount of 1122 phases in addition to the 1223 phases.

As is apparent from the above results, the production method according to the present invention can preferentially generate the 1223 phase having a high critical temperature. Therefore, an oxide superconducting material having a high critical temperature can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing the temperature dependence of the magnetic susceptibility of a superconducting material manufactured in an example according to the present invention.

FIG. 2 is a diagram showing an X-ray diffraction pattern of a superconducting material produced in an example according to the present invention.

FIG. 3 is a view showing an X-ray diffraction pattern of a superconducting material produced in a comparative example.

Claims (1)

(57) [Claims] 1. A method for producing a Tl—Bi—Ca—Sr—Cu—O-based superconducting material, wherein the composition of each element is Tl: Bi: Ca: Sr: Cu =
When expressed as a: b: c: d: 2 (molar ratio), 1.0
<A <2.0, 0.1 <b <0.6, 0.6 <c <1.
4,1.6 <from raw material to be d <2.4, at a critical temperature above _{60K, (Tl 1 - x,} Bi x) Ca U Sr V C
u _W O _Z (where x, u, v, w and z are 0.1
<X <0.5, 0.6 <u <1.4, 1.6 <v <2.
4,1.6 <w <2.4, and 5 <z <9), respectively, and a step of generating a 1122 phase superconducting phase represented by the following composition: Tl = f:
g: h (molar ratio) (where f, g and h are 0.8
<F <1.2, 0.8 <g <1.2 and 0.1 <h <
1.0)), Ca, Cu and T
l, and at a critical temperature of 100 K or more, (Tl _{1 -x} ,
_{Bi x) Ca U Sr V Cu} W O Z ( wherein, x, u,
v, w and z are 0.1 <x <0.5, 1.6 <u <
2.44, 1.6 <v <2.4, 2.6 <w <3.4, and 7 <z <11). Prepare,
A method for producing an oxide superconducting material.