JPH06183822A - Method of rapid synthesis of bi-based superconductor - Google Patents

Abstract

PURPOSE:To provide a method of synthesis capable of synthesizing a Bi-based superconductor of oxide of 2,223 phase having no 2,212 phase of by-product in a short time. CONSTITUTION:Raw material powder Bi2O3, PbO and CaCO3 or Bi2O3, PbO and Ca(NO3)2.4H2O is mixed, heated and melted at >=900 deg.C, then retained for a short time and quenched to give Bi-Pb-Ca-O-based activated powder. On the other hand, raw material powder SrCO3, CaCO3 and CuO or Sr(NO3)2, Ca(NO3)2.4H2O and CuO is mixed, heated and melted at >=1,200 deg.C, retained for a short time and quenched to give Sr-Ca-Cu-O-based activated powder. The Bi-Pb-Ca-O-based activated powder is mixed with the Sr-Ca-Cu-O-based activated powder, heat-treated in an oxygen-containing atmosphere and then quenched to synthesize 2,223 phase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synthesizing an oxide, and more particularly to a method for synthesizing a 2223 phase of a Bi-based oxide superconductor in a short time without generating a different phase.

[0002]

BACKGROUND OF THE INVENTION Bi system superconductor T _c (critical temperature) 1
2223 phase with 10K and 221 with T _c 80K
Two phases are known. Conventionally, 2223 of Bi-based superconductor
Conventional solid phase methods have been used in phase synthesis. This method uses raw material powders (usually Bi ₂ O ₃ , PbO, SrCO ₃ , C
aCO ₃ , CuO powder), mixed, calcined and fired 22
23 phases are synthesized. However, at present, a considerably long firing time of 100 hours or more is required (for example, Reference 1: LR Yuan, K. Kurosawa, Y. Takigawa, M. Okuda,
H. Naito, K. Nakahigashi, S. Nakanishi, T. Matsush
ita, Jpn. J. Appl. Phys., Vol. 30, No. 9A, 1545-15
48 (1991)). 222 from some groups recently
The three phases are Pb-Bi-Ca-O and Sr-Ca-Cu-O.
(Reference 2: R. Liang, H. Ishi, H. Kawaji, M. Itoh
and T. Nakamura, Jpn. J. Appl. Phys ,. Vol. 29, N
o.8, 1412-1414 (1990)) or Pb-Bi-Cu
-O and Sr-Ca-Cu-O (Reference 3: S. Hontsu,
O.Nishibuchi, T. Horiuchi, K.Ogura, J. Ishii, T.
Kawai and S. Kawai, Jpn. Appl. Phys., Vol. 31 (1992)
pp. 47-48), the composition was separated and calcined to reduce the main firing time.
However, the total heat treatment time from the actual starting mixture to the 2223 phase synthesis starting from the calcination to the main firing is almost unchanged. In addition, 22 synthesized by these methods
The present situation is that the 23-phase is somewhat mixed with a different phase.

[0003]

In the conventional solid phase method, for example, as in Reference 1, the synthesis of the 2223 phase requires a considerably long time. Also, by using the composition separation method (references 2 and 3), the time required for the main firing could be shortened, but a long time is still required to make the precursor, and the total 2223 phase synthesis time is required. Has not been shortened. Therefore, an object of the present invention is to solve the problems of the conventional solid phase method and composition separation method, and to provide a method for synthesizing a Bi-based superconductor composed of a 2223 phase single layer in a short time.

[0004]

In the rapid method for synthesizing a Bi-based superconductor according to the present invention which has achieved the above object, a predetermined amount of raw material powders of Bi, Pb and Ca and carbonate or nitrate raw material powders are used. After mixing, these raw material powders are heated and melted at a temperature of 900 ° C. or more in order to uniformly melt them, and after holding for a short time, rapidly cooled and crushed to obtain Bi-Pb-Ca.
In order to obtain an —O-based activation powder, and to mix a predetermined amount of raw material powders Sr, Ca, and Cu oxides and carbonate or nitrate raw material powders, to uniformly melt these raw material powders.
It is heated and melted at a temperature of 00 ° C. or higher, and then held for a short time, preferably within 60 minutes, then rapidly cooled and crushed to obtain Sr.
-Ca-Cu-O-based activation powder was obtained, and the above Bi-Pb
-Ca-O-based activation powder and Sr-Ca-Cu-O-based activation powder are mixed and heat-treated in an atmosphere containing oxygen, and then preferably heat-treated at a temperature of 850 ° C or lower in a low oxygen partial pressure atmosphere. Or a heat treatment in air at a temperature of 880 ° C. or lower, followed by rapid cooling to synthesize the 2223 phase.

In the method of the present invention, the raw material powder is melted by heating and held for a short time, but the holding time is short, preferably within 60 minutes. Since it evaporates and Pt and Bi, which are the materials of the crucible, react with each other, it is usually held for about 10 minutes.

Further, the Bi-Pb-Ca-O-based heating melting temperature and the Sr-Ca-Cu-O-based heating melting temperature are 900 ° C or higher and 1200 ° C or higher, respectively.
This is for uniformly melting Pb-Ca-O or Sr-Ca-Cu-O.

According to the method of the present invention described above,
As shown by comparing the conventional method in phase synthesis with the method of the present invention, in the conventional solid phase method, it takes a long time of 100 hours or more to synthesize 2223 phase, and in the composition separation method, the firing time is shortened. However, it takes a long time to make the precursor for calcination, and it takes a long time as a whole. On the other hand, the composition separation method for preventing the formation of the byproduct 2212 phase and the active raw material powder are used. By combining the obtained melt cooling methods, the 2223 phase without the by-product 2212 phase can be synthesized in a short time.

[Table 1]

[0008]

EXAMPLES The present invention will now be described with reference to examples.

[0009] Example _{1 Bi 1.8 Pb 0.3 Sr 1.9 Ca} 1.9 Cu 3 O y synthetic Bi _1.8 Pb _0.3 Ca _0.8 O _p and Sr _1.9 Ca _1.1 Cu
₃ O _q is a raw material powder of purity 99.9% Bi ₂ O ₃ , Pb
O, SrCO ₃ , CaCO ₃ , and CuO were used for synthesis. Bi _1.8 Pb _0.3 Ca _0.8 O _p is 15.78
97 g of Bi ₂ O ₃ , 2.5214 g of PbO and 3.0148 g of CaCO ₃ were weighed, sufficiently mixed, heated and melted at 1000 ° C. for 10 minutes, and then rapidly cooled for synthesis. Sr _1.9 Ca _1.1 Cu ₃ O _q is 11.2830
g of SrCO ₃ , 4.4287 g of CaCO ₃ and 9.5993 g of CuO were weighed, sufficiently mixed, heated and melted at 1400 ° C. for 10 minutes, and then rapidly cooled for synthesis. Obtained by melt quenching, Bi _{1. 8} Pb _0.3 Ca _0.8
O _p and Sr _1.9 Ca _1.1 Cu ₃ O _q were crushed respectively, and each crushed powder (activated powder) was converted into Bi _1.8
Pb _0.3 Sr _1.9 Ca _1.9 Cu ₃ O _y was weighed and mixed to form pellets having a diameter of 20 mm × 2 mm. The pellets were placed in a low oxygen pressure atmosphere (argon gas:
Oxygen = 93: 7) (Po ₂ = 7%) was heat-treated at 845 ° C. for 24 hours and rapidly cooled at a rate of 10 ³ ° C./sec. This is reground, molded further at 845 ° C., a heat treatment and then rapidly cooled 12 hours or 24 hours, Bi _1.8 of 2223 monolayers
Pb _0.3 Sr _1.9 Ca _1.9 Cu ₃ O _y was synthesized.

FIG. 1 shows the Bi thus synthesized.
_{1.8 Pb 0.3 Sr 1.9 Ca 1.9 Cu} 3 shows the O _y X-ray diffraction pattern of. Further, FIG. 2 shows the relationship between temperature and magnetic susceptibility. It can be seen from the result of X-ray diffraction that the magnetic susceptibility begins to drop sharply at a boundary of about 110 K as the temperature lowers, and this sample is composed of 2223 single phase. Similarly, the pellet was heated in air at 862 ° C. for (24 + 24) hours to obtain 2223 phase single phase Bi _1.8 Pb _0.3 Sr _1.9 Ca.
_1.9 Cu ₃ O _y could be obtained.

Example 2 Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y (0.2≤x≤
Synthesis of _{0.4) Bi 2-x Pb x} Ca 0.8 O y and Sr ₂ Ca _1.2 Cu ₃ O
_w was synthesized under the same conditions as in Example 1, and the same procedure was followed to obtain Bi _2-x Pb _x Sr ₂ Ca ₂ Cu ₃ O _y (x in the formula:
Indicates 0.2 or 0.4).

[0012] Example _{3 Bi 1.8 Pb 0.3 Sr 1.9 Ca} 1.9 Cu 3 O synthesis by nitrate raw material powder of _{y Bi 1.8 Pb 0.3 Ca 0.8 O} p and Sr _1.9 Ca _1.1 Cu
₃ O _q is a raw material powder with a purity of 99.9% Bi ₂ O ₃ , PbO, S
_{r (NO 3) 2, Ca} (NO 3) 2 · 4H 2 O, CuO
Were synthesized respectively. Bi _1.8 Pb _0.3 Ca _0.8
O _p is Bi ₂ O ₃ of 15.7897g, PbO of 2.5214, Ca (NO ₃₎ of 7.1112g ₂ · 4H ₂ O
Was used under the same conditions as in Example 1. Sr _1.9 C
a _1.1 Cu ₃ O _q is 16.1745 g of Sr (NO ₃ ).
_2, Ca (NO ₃₎ of 10.4463g ₂ · 4H ₂ O,
Synthesis was performed under the same conditions as in Example 1 using 9.5993 g of CuO. Bi _1.8 Pb _0.3 S
r _1.9 Ca _1.9 Cu ₃ O _y was synthesized.

[0013]

It is true that the conventional composition separation method shortened the firing time, but it took several tens of hours to prepare the precursor for the firing, and considering the production time of synthesis, It's not getting shorter. According to the present invention, the precursor preparation time for the main firing can be shortened from several tens of hours to only about 10 minutes, and the economical efficiency in the industry can be improved considerably. Furthermore, comparing the characteristics and the degree of single phase of the synthesized sample with those published in the paper so far, XRD and SQUI
From the result of D, it was found that the superconducting property was better and the phase was more single phase.

[Brief description of drawings]

FIG. 1 2223 single-phase Bi _1.8 Pb _0.3 Sr _1.9 Ca
It is an X-ray diffraction _{pattern of 1.9} Cu ₃ O _y .

FIG. 2 2223 single-phase Bi _1.8 Pb _0.3 Sr _1.9 Ca
₉ is a graph showing the relationship between the temperature and magnetic susceptibility of _1.9 Cu ₃ O _y .

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Furuya 1-14-3 Shinonome, Koto-ku, Tokyo Metropolitan Institute of Superconductivity Technology Research Center for Superconductivity Engineering (72) Inventor Tsuru Shiobara Koto-ku, Tokyo Shinonome 1-14-3, Foundation Law Institute for Superconductivity Engineering, Superconductivity Research Institute

Claims (6)

[Claims] 1. A mixture of Bi, Pb and Ca oxides and a predetermined amount of a raw material powder of carbonate or nitrate is mixed at 900 ° C.
The mixture is heated and melted at the above temperature, then held for a short time, then rapidly cooled and pulverized to obtain an activated powder of Bi-Pb-Ca-O system, while raw material powders Sr, Ca and Cu oxides and carbonates or nitrates. Mix a predetermined amount of raw material powder, 1200 ℃
After being heated and melted at the above temperature, and then held for a short time, it is rapidly cooled and pulverized to obtain an Sr-Ca-Cu-O-based activated powder. The Bi-Pb-Ca-O-based activated powder and the Sr- C
A rapid method for synthesizing a Bi-based superconductor characterized in that an a-Cu-O-based activated powder is mixed, heat-treated in an atmosphere containing oxygen and then rapidly cooled to synthesize a 2223 phase. 2. The rapid method for synthesizing a Bi-based superconductor according to claim 1, wherein the holding time is within 60 minutes. 3. The Bi-based superconductor according to claim 1, wherein the heating and melting to obtain the activated powder of Bi—Pb—Ca—O system is performed by heating at 900 ° C. or higher. Rapid synthetic method. 4. The Bi-based superconductor according to claim 1, wherein the heating and melting to obtain the Sr—Ca—Cu—O-based activated powder is performed by heating to 1200 ° C. or higher. Rapid synthetic method. 5. The heat treatment is performed in a low oxygen partial pressure atmosphere.
The method for rapid synthesis of a Bi-based superconductor according to any one of claims 1 to 4, wherein the method is performed at 850 ° C or lower. 6. The rapid synthesis method of a Bi-based superconductor according to claim 1, wherein the heat treatment is performed in air at 880 ° C. or lower.