JPH02199026A - Superconducting oxide - Google Patents

Abstract

PURPOSE:To provide a rare earth-alkaline earth-vanadium-based multiple oxide, a superconducting material having high-superconductivity critical temperature, giving excellent stability in the atmosphere at room temperature, having lamellar type perovskite crystal structure. CONSTITUTION:The objective superconducting oxide, a multiple oxide having lamellar-type perovskite crystal structure of the composition RxA1-xVyOz (R is at least one metal selected from Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; A is at least one metal selected from Mg, Ca, Sr and Ba; 0.05<=x<=0.5, pref. 0.05<=x<=0.3; 0.5<=y<=2, pref. 0.8<=y<=1.2; z<=5, pref. z<=4).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a superconducting material made of a vanadium-based composite oxide.

[Conventional technology] Many substances that exhibit superconductivity have been known for a long time.
Among alloy systems, it has been found that Nb-based alloys such as Nb 3 Ge and NbN exhibit a high superconducting critical temperature (hereinafter referred to as Tc). [＾ppHed Physi
Lett, 23 (1973) 480].

In addition, in recent years, some composite oxides with high Tc have been discovered, and in the La-Ba-Cu-0 system, Tc;
0K [Zeltschrift furphysl
, B 64 (19H) 189], Y-Ba-Cu-
In the 0 series, T c : 90K [Phys, Rev, L
ett., 5g (1987) 911], but these oxides are difficult to use practically because they react with moisture and carbon dioxide in the atmosphere and decompose.

Furthermore, it has been reported that Tc≧105 in the B1-5r-Ca-Cu-0 system [Jap, J.

or Appl, Phys, 27 (198g) 209
], When these composite oxides using copper have a low oxygen concentration and are used at high temperatures, the reduction of copper progresses and they no longer exhibit superconductivity.

[Problems to be Solved by the Invention] The present invention has been made in consideration of the above points.
The object of the present invention is to provide a superconducting oxide material having a high stability in the atmosphere.

[Means for Solving the Problems] As a result of intensive research to solve the above-mentioned problems, the present inventors have discovered that rare earth-alkaline earth-(nadium) complex oxides have a high superconducting critical temperature. Furthermore, the present inventors have discovered that the stability is excellent at room temperature in the atmosphere, and have completed the present invention.

That is, the superconducting oxide of the present invention has the following composition: Rx A + -x V yOz (wherein, R is YsLaSCesPr, Nd.

S m s E u s G d s T b SD
y SHo, Er.

At least one metal selected from Tm, Yb or Lu, A is M g s Ca s S r or B
0, 05≦x≦0.5 0, 5≦y≦2 2 ≦ 5 in at least one metal selected from a), and has a layered perovskite crystal structure. be.

Hereinafter, the superconducting oxide of the present invention will be explained in detail.

The superconducting composite oxide of the present invention is a composite oxide having a composition of Rx A + -x V y Oz. R is a rare earth element, specifically Y SL a s Ce s Pr
, Nd, Sms Eu, Gd, Tbs DY% HOl
One or more of the following can be used: A species or two or more species may be used.

The composition of R and A needs to be 0.05≦x≦0.5, preferably 0.05≦x≦0.3. If the value of Moreover, if the value of

Further, the composition of V needs to be 0.5≦y≦2, preferably 0.8≦y≦1.2. If the value of y is less than 0.5 or more than 2, an insulating crystal phase will be formed, which is not preferable.

Next, the composition of 0 (oxygen) needs to be Z≦5. Complex oxides having a perovskite crystal structure often have oxygen vacancies, and the superconducting oxide of the present invention is no exception. The amount of oxygen vacancies depends on the composition and synthesis conditions, and the superconductivity changes accordingly, but in order to generate a large amount of superconducting phase, the value of Z is 5.0 or less, preferably 4.0 or less. .

Furthermore, in the present invention, even if a small amount of impurities contained in ordinary reagents are present in the composite oxide, the performance is hardly affected.

Next, a method for producing a superconducting composite oxide of the present invention will be described, but the method is not particularly limited thereto.

The method for producing superconducting composite oxides of the present invention includes, for example, compounds such as rare earth oxides, carbonates, nitrates, and oxalates of rare earth elements, and oxides, carbonates, nitrates, etc. of alkaline earth elements. There is a synthesis method in which a compound and a vanadium compound such as vanadium sesquioxide are mixed in a predetermined amount and then heated at a predetermined temperature and atmosphere to perform a solid phase reaction.

Furthermore, a precipitating agent such as oxalic acid or ammonium carbonate is added to a mixture of aqueous solutions of soluble salts such as rare earth elements, alkaline earth elements, vanadium chlorides, and nitrates to cause coprecipitation, and then the coprecipitated compound is prepared. There is a method of synthesis by heating and pyrolysis.

The conditions for the heating reaction vary depending on the composition, but it is necessary to carry out the reaction at 1000° C. to 1200° C. in a predetermined atmosphere for at least 0.5 hours or more, preferably for 2 hours or more.

The composite oxide obtained as described above is pulverized by a pulverizing means such as a ball mill or a jet mill, if necessary, and then molded into a predetermined shape and sintered. The conditions for sintering vary slightly depending on the composition, but 100%
It is necessary to carry out the heating at 0°C to 1200°C for at least 0.5 hours or more, preferably for 2 hours or more.

By annealing the obtained composite oxide in a predetermined atmosphere and temperature, it is possible to control the composition of oxygen ions contained in the sample and further increase the volume fraction of superconducting oxide in the sample. .

In addition, in order to form the desired composite oxide on the substrate,
It is also possible to form by a sputtering method using the composite oxide as a target material, and it is also possible to form by a CVD method using constituent metals such as chlorides, bromides, and iodides.

[Example code] A more detailed explanation will be given below with reference to Examples.

Example 1 Praseodymium oxide 0.33 mol Strontium carbonate 0.33 mol Calcium carbonate 0.
After mixing 1 mol of 33 mol vanadium sesquioxide in a mortar, Ar99.95%, 020.0
It was baked at 1looo C. for 8 hours in a 5% atmosphere.

After crushing the obtained composite oxide in a mortar, 1 ton/C
Press molded at a pressure of s2, Ar99.95%, 02
(It was sintered at 00''C in a 1.05% atmosphere for 8 hours to obtain a disk-shaped sintered body.

This was annealed at 600° C. for 8 hours in an atmosphere of Ar 99.9% and 020.1%.

The composition of the Kono sintered body is Pro, 3i (Sro,

0Cao, 5) 0.67V102.96・
To measure resistance, cut out the sintered body into a rectangular parallelepiped, attach electrodes,
The test was carried out using a four-terminal method while flowing a current of lsA.

Figure 1 shows the temperature dependence of electrical resistance. From this figure, the temperature at which superconductivity begins is 1 in 52, and the temperature at which resistance becomes completely zero is 4.
It's on 5th.

FIG. 2 shows the X-ray diffraction pattern. From this result, the composite oxide is considered to have a layered perovskite crystal structure, with crystal lattice constants of -3,810A on the a-axis,
B axis - 3,831A, C axis - 11,665A and calculation saler.

Further, FIG. 3 shows the results of measuring the magnetic susceptibility using a SQUID magnetometer. A decrease in magnetic susceptibility is observed at 52, which coincides with the superconductivity onset temperature in the case of resistance measurements.

Examples 2-8 Ro, 33 (S r O,9 Ca o, s ) 0.
A 67VOZ-based composite oxide was synthesized by replacing R with various rare earth elements, and samples were prepared in the same manner as described in Example 1 above.

The temperature dependence of the electrical resistance of the obtained composite oxide was measured in the same manner as in Example 1, and the results are summarized in Table 1.

Table 1 Ro, 33 (S r O,5Ca o, s ) o,
atVOz Examples 9-15 Pro, 1 (A 1 o, s ・A 20.5
) 0.9 AI, A2 in VOz-based composite oxide
were synthesized using various alkaline earth metals, and samples were prepared in the same manner as described in Example 1 above.

The temperature dependence of the electrical resistance of the obtained composite oxide was measured in the same manner as in Example 1, and the results are summarized in Table 2.

Table 2 P r o,ss (A 1 o,s'
A2o,s) 0.6? The results of VOZ measurement are shown in Tables 3 and 4, respectively.

Table 3 Table 4 Examples 16-24 P rx (S rW Ca+-w )+-x Vy
Oz series 1 and YX (S rW Ca +-w)
+-x Vv Oz-based composite oxides were synthesized by changing the values of XsY and W, and samples were prepared in the same manner as described in Example 1 above. The temperature dependence of the electrical resistance of the obtained composite oxide was measured in the same manner as in Example 1 [Effects of the Invention] Because it maintains superconductivity up to 100%, it is extremely useful as an industrial material that can be used for a variety of purposes.

[Brief explanation of the drawing]

Figure 1 is a graph showing the resistance-temperature characteristics of the composite oxide of the present invention. Figure 2 is a graph showing the X-ray diffraction pattern of the composite oxide of the present invention.
FIG. 3, a graph taken using Ka line, is a graph showing the magnetic susceptibility-temperature characteristics of the composite oxide of the present invention. Patent applicant Asahi Kasei Industries Co., Ltd. Agent Patent attorney Hide Komatsu Agent Patent attorney Hiroshi Asahi

Claims (1)

[Claims] Composition R_xA_1_-_xV_yO_z (however,
R is Y, La, Ce, Pr, Nd, Sm, Eu, Gd,
At least one metal selected from Tb, Dy, Ho, Er, Tm, Yb or Lu, A is Mg, Ca, S
At least one metal selected from r or Ba)
0.05≦x≦0.50 0.5≦y≦2 z≦5 and having a layered perovskite crystal structure.