JP2879448B2 - Bi-Pb-Sr-Ca-Cu-O based superconducting material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to Bi having a zero resistance critical temperature (Tc) of 108 K or more.
The present invention relates to a Pb-Sr-Ca-Cu-O-based superconducting material.

[Conventional technology]

In 1988, at the Institute for Materials Research, Bi-Sr-Ca-Cu-O
Was found to have a superconducting material of 105K (extrapolated from the experimental data).
It has been considered difficult to provide a Bi-Sr-Ca-Cu-O-based superconducting material having a good phase volume ratio with good reproducibility.

On the other hand, the inventor has converted Bi-Sr-Ca-Cu-O by a synthetic method.
We succeeded in providing a superconducting material showing Tc 107K in a system containing Pb, and filed a patent application in May 1988.

However, even in a system to which Pb is added, it is difficult to synthesize a superconducting material having a Tc of 107 K or more and a good volume fraction of a high Tc phase with good reproducibility. Few have been successful.

[Problems to be solved by the invention]

Y-Ba-Cu-O system or the Bi system discovered in 1988,
The Bi-Pb system has caused great repercussions inside and outside the country on the grounds that the Tc is higher than the liquid nitrogen temperature (77 K) and that superconductivity may be developed using liquid nitrogen. However, even in the case of superconductors using liquid nitrogen, it is true that the higher the critical temperature is higher than the temperature of liquid nitrogen, the more excellent the properties related to superconductivity and the better the stability of superconductivity in use. There has been a demand for a substance having a higher Tc.

The present inventor changes the molar ratios of the component elements charged and the heat treatment conditions in the Bi-Pb-Sr-Ca-Cu-O system in various ways. We studied and studied to provide superconductors with higher reproducibility and higher Tc.

[Means for solving the problem]

The present invention has been achieved as a result of the above research and relates to the following superconducting material.

(1) Bi-Pb-Sr-Ca-Cu-O-based oxide,
The ratio of the number of moles of the constituent elements Bi, Pb, Sr, Ca, Cu of the oxide is BinP
In the case of bmSrxCayCu ₂ (normalized with the number of moles of Cu being 2), 1.05 ≦ n ≦ 1.145 0.12 ≦ m ≦ 0.25 1.20 ≦ x ≦ 1.35 1.20 ≦ y 1.35 and the zero resistance critical temperature (Tc) of 108K or more Bi-Pb-Sr-Ca-Cu-O-based superconducting material (2) The molar ratio of the constituent elements Bi, Pb, Sr, Ca, and Cu is 1.05 <n≤1.12 0.15≤m≤0.23 1.25≤x≤ 1.35 Bi-Pb-Sr-Ca-Cu-O-based superconducting material according to claim 1, wherein y satisfies 1.25≤y≤1.35. In the above, (1) is Bi-Pb-Sr-Ca-Cu actually synthesized.
A sample having a high volume ratio of at least Tc108K is extracted from the -O-based superconducting material, and a sample that can be synthesized with good reproducibility is represented by the ratio of the number of moles of the element. Is the ratio of the number of moles.

The above compound can be produced by the following method.

That is, first, Bi ₂ O ₃ , SrCO ₃ , CaCO ₃ , CuO and PbO are used as starting materials, each of them is weighed and mixed at a desired ratio, or Bi, Pb,
A carboxylate such as oxalate containing Sr, Ca, and Cu in desired ratios is synthesized by a precipitation method. At this time, Bi, Sr, Ca, and Cu may be approximately the composition ratio of the target superconducting substance, but Pb is considerably evaporated by a heat treatment performed later, so that it is necessary to add Pb to the target composition ratio of Pb.

More specifically, in mixing the starting materials, the molar ratio of each element may be such that 1.00 <n <1.20 0.15 <m <0.60 1.15 <x <1.40 1.15 <y <1.40 based on Cu ₂ .

The mixed powder or carboxylate such as oxalate compounded as described above is then preferably calcined at about 800 ° C. or lower for several hours.
In the case of oxalate, it is preferable to calcine after thermal decomposition at about 250 ° C. Then after grinding this about 500kg / cm
Pressing at ² to form pellets and firing at 845 to 865 ° C.

〔Example〕

Example 1 Ammonium oxalate was added to a mixed aqueous solution of nitrates of Bi, Pb, Sr, Ca, and Cu, and the composition ratio of component elements was Bi _1.15 Pb _0.30.
Precipitate the oxalate of Sr _1.30 Ca _1.30 Cu _2.00 ,
After drying at 500 ° C., the mixture was pulverized and mixed, and heated in air at 800 ° C. for 12 hours in an electric furnace. This is crushed again and about 60
It was formed into a green compact pellet having a diameter of 20 mm and a thickness of 2 mm by a press of 0 kg / cm ² , and was fired at 850 ° C. for 24 hours in an electric furnace in the air. Next, the operation of the pulverization-press-compact pellets was repeated, and the mixture was calcined by heating in air in an electric furnace at 850 ° C. for 48 hours.

The result of analyzing this sample by ICAP was Bi _1.098 Pb _0.153 Sr _1.266 Ca _1.243 Cu _2.00 (normalized by the number of moles of Cu).

As shown in FIG. 1, the temperature change of the electric resistance dropped from about 130K and became zero at about 111K. Further, the X-ray diffraction pattern of this substance is as shown in FIG.
The phase was about 98%.

Example 2 Ammonium oxalate was added to a warm aqueous solution of each nitrate of Bi, Pb, Sr, Ca, and Cu, and the composition ratio of component elements was Bi _1.10 Pb _0.35.
Precipitate the oxalate of Sr _1.32 Ca _1.32 Cu _2.00 ,
After drying at 500 ° C., the mixture was pulverized and mixed, and heated in air at 800 ° C. for 12 hours in an electric furnace. This is crushed again and about 10
A green compact pellet having a diameter of 20 mm and a thickness of 2 mm was formed with a press of 00 kg / cm ² , and this was heated and fired in an electric furnace at 850 ° C. for 120 hours in the air. Analysis of this sample by ICAP (normalized by moles of Cu) Bi _1.075 Pb _0.165 Sr _1.298 Ca _1.285 Cu _2.00
Met.

As shown in FIG. 3, the temperature change of the electric resistance dropped from about 130K and became zero at about 112K. The results of measurement of the complex susceptibility of this substance are as shown in FIG.
As described above, it was confirmed that the superconductor was used. Further, the X-ray diffraction pattern of this substance is as shown in FIG.
The Tc phase was approximately 90%.

Example 3 In the same manner as in Example 1, the molar ratio of the component elements was changed to Bi.
Precipitate the acid salt of _1.10 Pb _0.26 Sr _1.25 Ca _1.25 Cu _2.00 , and otherwise exactly the same as Bi _1.058 Pb _0.168 Sr _1.221 Ca _1.213 Cu _2.00
Sample was obtained.

This sample has a zero resistance critical temperature of 108 K and X
From the line diffraction diagram, it was confirmed that the high Tc phase was about 80%.

Example 4 In the same manner as in Example 1, the molar ratio of the component elements was changed to Bi.
_1.18 Pb _0.34 Sr _1.25 Ca _1.35 Cu _2.00 Precipitate acid salt, and otherwise exactly the same Bi _1.145 Pb _0.204 Sr _1.203 Ca _1.313 Cu _2.00
Sample was obtained.

This sample had a zero resistance critical temperature of about 108 K, and the X-ray diffraction pattern confirmed that the high Tc phase was about 90%.

〔The invention's effect〕

The Bi-Pb-Sr-Ca-Cu-O-based material of the present invention has a superconducting critical temperature of at least 108K or more, and a preferable molar ratio of 110K or more.

The process for producing this material is easy and reproducible as described above.

[Brief description of the drawings]

FIG. 1 is an electrical resistance-temperature correlation diagram of the substance obtained in Example 1. FIG. 2 is an X-ray diffraction diagram of the same substance. FIG. 3 is an electrical resistance-temperature correlation diagram of the substance obtained in Example 2, and FIG. 4 is a complex susceptibility-temperature correlation diagram of the same substance. FIG. 5 is an X-ray diffraction diagram of the same substance.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Naoichi Yamamoto 1-2 Satakedai, Suita-shi, Osaka Satakedai Heights D-17-203 (56) References JP-A 1-275433 (JP, A) JP-A-2-248321 (JP, A) JP-A-2-141425 (JP, A) JP-A-2-289427 (JP, A) JP-A-3-5358 (JP, A) JP-A-2-192419 ( JP, A) JP-A-2-250217 (JP, A) JP-A-2-258666 (JP, A) JP-A-2-504261 (JP, A) Jpn. J. Appl. Phys. , 27, No. 7 (1988), p. L1225 to L1227 Jpn. J. Appl. Phys. , 27, No. 10 (1988), p. L1861 to L1863 Solid State Com m. , 68, No. 3 (1988), p. 327-330 Jpn. J. Appl. Phys. , 27, No. 11 (1988), p. L2067 to L2070 Jpn. J. Appl. Phys. , 28, No. 4 (1989), p. L576-L579

Claims (2)

(57) [Claims] Claims: 1. An oxide of the Bi-Pb-Sr-Ca-Cu-O system, wherein the molar ratio of the constituent elements Bi, Pb, Sr, Ca, Cu of the oxide is as follows:
_{Bi n Pb m Sr x Ca y} Cu 2 and the (to normalize the number of moles of Cu as a 2) a case 1.05 <n ≦ 1.145 0.12 ≦ m ≦ 0.25 1.20 ≦ x ≦ 1.35 1.20 ≦ y ≦ 1.35, and zero A Bi-Pb-Sr-Ca-Cu-O-based superconducting material having a critical resistance temperature (Tc) of 108K or more. 2. The Bi according to claim 1, wherein the molar ratio of the constituent elements Bi, Pb, Sr, Ca and Cu is 1.05 <n ≦ 1.12 0.15 ≦ m ≦ 0.23 1.25 ≦ x ≦ 1.35 1.25 ≦ y ≦ 1.35. -Pb-Sr-Ca-Cu-O-based superconducting material.