JP2555505B2 - Metal oxide material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel metal oxide material having superconductivity, and in particular, the present invention relates to sensors, electronic devices, computers, medical equipment, magnets, power transmission lines, which use superconductivity. The present invention relates to a metal oxide material that can be used in various fields such as energy equipment and voltage standards. The present invention is particularly effective when used as a bulk material, and the material of the present invention can also be used in the form of bonding or dispersion with another oxide or metal.

[0002]

2. Description of the Related Art Oxide superconductors containing copper, which have been discovered one after another in recent years, have a Tc that greatly exceeds the conventionally known superconducting critical temperature (Tc) of niobium and the like. Applied research is underway. Bi-based, Tl-based, Pb-based, Y-based, La-based, and the like are known as the oxide superconductor containing copper. Among such copper-containing oxide superconductors, Sr, Ln (Y or lanthanoid element), Cu
And a superconductor consisting of oxygen, Japanese
Journal Applied Physics V
ol. 26 L804 (1987), Solid St
ate Communications Vol. 63
535 (1987), and Proceedings of the Autumn Meeting of the Physical Society of Japan, 1990, 3rd Volume, 243 pages, 2p-PS-30.
, YSr ₂ Cu ₃ O _y superconductor is known. Also, Chemistry of Material
s Vol. 1331 (1989), YSr ₂ Cu
_3-x MOy (M = Al, Fe, Co or Pb, 0.
It is known that the composition is 4 ≦ x ≦ 1.0).

[0003]

[Problems to be solved by the invention] However,
Since the Bi-based, Tl-based, and Pb-based superconducting materials have a large specific gravity of 7 to 8 g / cm ³ , the total weight of the superconducting materials increases when they are used in bulk material applications (for example, shield materials). The problem is that Further, among the conventional examples, the Sr-based 123 phase material has a smaller specific gravity than the above materials, but a large amount of impurities are mixed in, the synthesis is difficult, and the T
There is a problem that c is low (at most about 20K). For example, Japanese Journal Appli
Physics Vol. 26 L804 (19
87) and Solid State Communicat
ions Vol. With the composition of 63 535 (1987), a good single-phase sample represented by YSr ₂ Cu ₃ O _y cannot be synthesized, and SrCuO ₂ , Sr ₂ Cu
O ₃ , Y ₂ SrO ₄ , Y ₂ CuO ₅ , SrCu ₂ O _2, Sr _1.75 Cu ₃ O _{5.13, and the} like were deposited as impurities in large amounts, and were not usable. That is, S
In the case of the r-type 123 phase, although it was satisfactory in terms of weight reduction, the ratio of the superconducting material in the composite was extremely small and it could not be used. Also, the above-mentioned Physical Society of Japan 1
The sample of the 1993 Autumn Subcommittee Lecture Proceedings, Third Volume, page 243, was synthesized by a special apparatus of 70 Kbar and 13800 ° C., which is not generally available, and was not suitable for application. Also, the temperature at which the resistivity becomes zero (zero resistance temperature) even when synthesized with such a special device.
Was about 20K. Also, Chemistry of
Materials Vol. 1331 (1989)
Material has superconductivity when M = Co or Fe, but has a low zero resistance temperature of about 10K and a superconductor volume fraction of 2%.
However, it was not suitable for use as a superconducting material.

Therefore, an object of the present invention is to provide a superconducting material of good quality and containing few impurities, which can be synthesized without using such a special synthesizer of ultrahigh pressure. Another object of the present invention is to provide a material having a high superconducting transition temperature and a large superconducting volume fraction, and having excellent characteristics as a superconducting material. In addition, the above-mentioned YBa ₂
Currently known stable copper oxide superconducting materials such as Cu ₃ O _y are Bi-based, Tl-based, and Pb-based materials, but all have a specific gravity of 7 to 8 g / cm ^3. When used as a shield material, which is an application example as a bulk material, the weight has been considerably increased. Therefore, another object of the present invention is to provide a material having a lower specific gravity than these existing copper oxide superconductors. Another object of the present invention is to provide a highly safe material that does not contain a large amount of highly toxic heavy metals such as Bi-based, Tl-based, and Pb-based materials, and barium carbonate as a raw material such as Y-based material. It is to provide materials that do not use toxic raw materials such as. In addition, YBa ₂ Cu ₃ O _y, which is a representative of Y series,
Is easily decomposed into Y ₂ O ₃ , BaCO ₃ and CuO by water and water vapor, which has been a serious problem in use and in manufacturing a thin film device. Therefore, another object of the present invention is to provide a material having excellent water resistance which is hardly affected by moisture or water vapor. Furthermore, YBa ₂ Cu
_{In the case of 3} O _y , there was a problem that oxygen was released at high temperature and the characteristics were deteriorated. For example, YBa at room temperature
₂ Cu ₃ O _y had oxygen depleted at 900 ° C. of 1 in y and 2.4% in weight change. Therefore, another object of the present invention is to provide a material from which oxygen hardly escapes at high temperature.

[0005]

The above objects can be achieved by the present invention described below. That is, in the present invention, the composition formula is Ln.
In the metal oxide material expressed as _{a Sr b Cu 3-x Re} x O c, 2.7 ≦ a + b ≦ 3.3,0.8 ≦ a ≦
1.2, 6 ≦ c ≦ 9 and 0.05 ≦ x ≦ 0.4,
A metal oxide material, wherein Ln is one or more kinds of elements or atomic groups selected from the element group of Y element and lanthanoid element.

[0006]

According to the present invention, the specific gravity is as light as ⁵ to 6 g / cm ³ by selecting the composition ratio of the constituent elements,
Moreover, the superconducting transition temperature is 20K or higher, preferably 25K.
The above metal oxide materials are provided. Further, the metal oxide material of the present invention has a structure similar to that of YSr ₂ Cu ₃ O _y which can be generally synthesized only under the condition of ultrahigh pressure, but the metal oxide material can be synthesized even under 1 atmospheric pressure. In addition, the characteristics as a superconductor can be improved.
This can be achieved by selecting a specific transition metal for the element substituting the Cu site and optimizing the substitution amount.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The metal oxide material of the present invention may be any one as long as it has the above-mentioned composition, and a preferable material in the present invention is:
= 1 and b = 2, and Ln is a metal oxide material having Y, Ho, Dy, or Gd. Further, as a suitable material, the crystal lattice is tetragonal or orthorhombic,
The metal oxide material has the above-described composition and has a lattice constant (c) of 11 Å or more and 12 Å or less. Suitable materials are also metal oxide materials of the above composition which have superconductivity at temperatures above 20 Kelvin, particularly preferably above 25 Kelvin.

As a method for producing the metal oxide material of the present invention as described above, any reaction and sintering method by heating from raw material powder, which is generally used for so-called ceramic materials, is used. You can An example of such a method is Material Research Bu.
lletin vol.8, p.777 (1973), Sol
id State Communication 1st
Volume 7, page 27 (1975), Zeitschriftf
ur Physik B Vol. 64, p. 189 (1986)
Year), Physical Review Letter
s Vol. 58, No. 9, p. 908 (1987) and the like, and these methods are now known as qualitatively extremely general methods. In particular, when using the metal oxide material of the present invention as a substrate for a superconducting electronic device,
A method in which the raw material powder is melted at a high temperature using a flux or the like and then a single crystal is grown is also useful.

When the metal oxide material of the present invention is used for a thin film electronic element or a shield material, a sputtering method such as high frequency sputtering or magnetron sputtering using a target containing raw materials, electron beam evaporation,
MBE method, other vacuum deposition method or cluster ion beam method, CVD method using gas as a raw material, or plasma CVD
The metal oxide material of the present invention can be formed into a thin film on a substrate or a superconducting thin film by a method or the like. The copper oxide material of the present invention thus obtained has a particularly high superconducting transition temperature. The superconducting transition temperature at this time is up to ten and several K to 70K, although it depends on x of Re. Therefore,
The metal oxide superconductor of the present invention can be used not only at liquid helium temperature but also by a simple cooler.

Further, all the raw materials used for the metal oxide material of the present invention are inexpensive, the raw material cost is low, and the metal oxide material of the present invention can be provided at low cost.
Further, the material of the present invention is relatively stable in the air and less deteriorated, and further, because it does not use a toxic material such as a heavy metal as a raw material, it is highly safe. Further, the specific gravity of the metal oxide material of the present invention is in the range of 5 to 6 g / cm ³ , which is about 20 to 30% lighter than the existing copper oxide superconductor. This is particularly effective when the metal oxide material of the present invention is used as a shield or bulk material for magnetic levitation. Further, the metal oxide material of the present invention has the property of being less susceptible to the effects of moisture and water vapor, which makes it possible to expand the use conditions and applications of the material and increase the durability,
Furthermore, the surface condition is stable in device fabrication, which is advantageous. Further, the metal oxide material of the present invention is less likely to release oxygen at high temperatures, and is effective in use and material preparation.

[0011]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. Example 1 and Comparative Example _Y 2 _O 3 as a 1-6 _{material, SrCO 3, Cuo, ReO 3} ,
Al ₂ O ₃ , MnO ₂ , NiO, Fe ₂ O ₃ and Co ₂
Using O ₃ , these were weighed to a suitable composition ratio and dry-mixed. Each of these mixtures has a diameter of 10 mm and a thickness of 1 m.
m in the form of pellets, the formed products were placed on alumina boats, respectively, and reacted and sintered in the air or at 950-1100 ° C. in air or oxygen to give the copper oxides of Examples and Comparative Examples of the present invention. Prepared respectively. With respect to these samples thus formed, the electrical resistivity was measured by four terminals and the magnetic susceptibility was measured by SQUID in the temperature range from room temperature to liquid helium temperature. Table 1 shows the composition ratio of the copper oxide of Example 1 and its transition temperature (K). Further, Table 2 shows the charged compositions and electrical characteristics of the oxides of Comparative Examples 1 to 6.
Since the composition ratio was measured by EPMA, there may be an error of about 20% in the amount of oxygen.

[0012]

[Table 1]

[0013]

[Table 2]

From Table 1, the materials of the examples of the present invention have Tc = 2.
It becomes a superconductor having a temperature of 0K or higher, and is particularly excellent in characteristics as a superconductor. As is clear from the comparative example shown in Table 2,
It can be seen that when the element substituting the Cu site is other than Re, the material formed does not show a superconducting transition, or even if it shows, Tc is as low as 10 K or less. FIG. 2 shows an X-ray diffraction pattern of the metal oxide material formed in Example 1. From this figure, the sample of Example 1 has a = b = 3.8.
It can be seen that it is a tetragonal crystal having a lattice constant of 3Å and c = 11.5Å. Further, FIG. 3 shows a graph of temperature dependence of electric resistivity of this sample. As a result, the superconducting transition starts at about 40K and the resistance becomes zero at 35K. This shows that the metal oxide material of the present invention becomes a superconductor at a temperature much higher than the liquid helium temperature.

Further, FIG. 4 shows the measurement results showing the temperature dependence of the magnetic susceptibility of the metal oxide material formed in Example 1. From this, it can be seen that the sample of Example 1 exhibits the Meissner effect from 35K and the superconductor integration rate at 10K exceeds 20%. These results are shown in the Chemistry of Materials Vo shown in FIG.
l. 1331 (1989), YSr ₂ C
Comparing with the data of u _3-x Fe _x O _y , it can be seen that the zero resistance temperature and the superconducting volume fraction of the material of the present invention are much higher. Further, for example, the specific gravity of the material of Example 1 is 5.5 g / cm ^3, which is about 30% lighter than the existing copper oxide superconductor, for example, YBa ₂ Cu ₃ O ₇ .

Further, FIG. 5 shows the metal oxide material formed in Example 1, and FIG. 6 shows YBa ₂ Cu ₃ O ₇ as a comparative example.
The X-ray-diffraction result about the endurance test result with respect to the water | moisture content of a material is shown. Here, the durability test was performed by leaving each material in steam under conditions of 40 ° C. and 50 hours. As a result, no change is seen in the X-ray pattern in FIG.
In YBa ₂ Cu ₃ O ₇ in FIG. 6, the original structure is almost lost, and peaks due to BaCO ₃ , Y ₂ O ₃ and CuO are seen. Therefore, YBa ₂ Cu ₃ O ₇ does not exhibit superconductivity at all. FIG. 7 shows Example 1 after this durability test.
The measurement result of electric low efficiency of the material of is shown. From this figure, the superconductivity is almost unchanged, showing the good durability of the material of the present invention against moisture. Further, the Bi type, which is a representative of other oxide superconducting materials, is considered to be weaker to moisture than the Y type. Table 1 shows the deterioration of Tc due to the water resistance test of Example 1. As a result, it can be seen that the material of the present invention has excellent water resistance. Furthermore, FIG. 8 shows the measurement results of TG-DTA of the material of Example 1. During this measurement,
The sample used was 50.4 mg. From this figure, the loss of oxygen in the metal oxide material of the present invention at 900 ° C. is 1 by weight.
%, Which is approximately 0.34 when expressed by oxygen in the composition formula.
Met. This is 2.4% by weight change in the case of YBa ₂ Cu ₃ O ₇ of the comparative example, which is about 1/3 of 1 in the case of being expressed by oxygen, and the metal oxide material of the present invention. It can be seen that in the case of, the deterioration due to the escape of oxygen is less. still,
The results shown in FIGS. 5, 7, and 8 are similarly observed in the other examples.

Examples 2 to 4 and Comparative Examples 7 to 12 Y ₂ O ₃ , Ho ₂ O ₃ , Ga ₂ O ₃ and ReO as raw materials.
₃ , SrCO ₃ and CuO were used, and these were weighed in an appropriate composition ratio and dry-mixed. These mixtures were reacted and sintered in the same manner as described above to prepare copper oxides of Examples of the present invention and Comparative Examples, and electric resistivity and magnetic susceptibility were measured. Table 3 shows the composition ratios of the copper oxides of Examples 2 to 4 and their transition temperatures (K). Further, Table 4 shows Comparative Examples 7 to 12
2 shows the charging composition and electrical characteristics of the copper oxide. Since the composition ratio was measured by EPMA, there may be an error of about 20% in the amount of oxygen. It can be seen from Table 3 that all the metal oxide materials within the composition ratio used in the present invention are superconductors with Tc = 20K or more. In the materials of Comparative Examples other than the composition ratios used in the present invention shown in Table 4, the temperature at which the superconducting transition did not occur or the superconducting transition occurred to zero resistance was 10 K or less. Also, the superconductor volume fraction was 3% or less, and the characteristics were poor. In addition, in the same manner as described in Example 1 in the right column of Table 3, T when water resistance test was performed
shows deterioration of c. As a result, it can be seen that the material of the present invention has excellent water resistance.

[0018]

[Table 3]

[0019]

[Table 4]

Examples 5 to 6 and Comparative Examples 13 to 26 The materials shown in Tables 5 and 6 were reacted and sintered in the same manner as described above using the necessary materials, and the copper used in the Examples and Comparative Examples of the present invention. An oxide was prepared. The X-ray diffraction patterns of the materials listed in Examples 5 to 6 are almost the same as those in FIG. 2, and it can be seen that similar structures are obtained. As for the temperature dependence of these magnetic susceptibility, as shown in FIG. 4, the superconductor integral ratio exceeded 10%, and the characteristics were good. From Table 5 and Table 6, regarding the element Re used in the composition ratio of YSr ₂ Cu _3−x Re _x O _y , the range of X with good superconducting properties is as follows: 0.05 ≦ x ≦ 0.4 In addition, in the same manner as described in Example 1, the right column of Table 5 shows deterioration of Tc when the water resistance test is performed. As a result, it can be seen that the material of the present invention has excellent water resistance.

[Table 5]

[0021]

[Table 6]

[0022]

(Effects) (1) Unlike the superconducting materials which can be synthesized only under an ultrahigh pressure, the metal oxide material of the present invention can be synthesized stably under atmospheric pressure. (2) The metal oxide material of the present invention is a superconducting material having a superconducting transition temperature far exceeding the liquid helium temperature and a superconducting volume fraction exceeding 10%. Therefore, the metal oxide material of the present invention can be used with an easy cooling device. (3) The metal oxide material of the present invention has the lowest specific gravity among the stable copper oxide superconductors known to date, and is particularly effective when used as a bulk material. (4) When synthesizing the metal oxide material of the present invention, compared with other copper oxide superconductors, the raw material used is not a heavy metal, barium carbonate, or other highly toxic one, and is therefore safe. It is cheap. (5) The metal oxide material of the present invention is excellent in durability against moisture and water vapor, and can be used under various conditions and applications. In addition, the surface of the material is stable, so that it can be used as a device material. It can be used effectively. (6) Since the metal oxide material of the present invention has little oxygen desorption even at high temperatures, it is useful because there are few measures against oxygen depletion in production as well as in use.

[Brief description of drawings]

FIG. 1 Chemistry of Material
s Vol. 1331 (1989)
_{Sr 2 Cu 3-x Fe x} O y data.

FIG. 2 YSr ₂ Cu _2.7 Re _0.3 O of Example 1
X-ray diffraction pattern of _7.0 . The X-ray at this time is CuK.
α rays were used.

FIG. 3 is YSr ₂ Cu _2.7 Re _0.3 O of Example 1.
The graph of the temperature dependence of the electrical resistivity of _7.0 .

FIG. 4 YSr ₂ Cu _2.7 Re _0.3 O of Example 1
The graph of the temperature dependence of the magnetic susceptibility of _7.0 .

5: YSr ₂ Cu _2.75 Re _{0.25 of} Example 1 FIG.
X-ray diffraction patterns before and after steam treatment of O _7.2 .

FIG. 6 is an X-ray diffraction pattern before and after steam treatment of YBa ₂ Cu ₃ O _y of a comparative example.

FIG. 7: YSr ₂ Cu _2.75 Re _{0.25 of} Example 1
The graph of the temperature dependence of the electrical resistivity of O _7.2 before and after the steam treatment.

8: YSr ₂ Cu _2.75 Re _{0.25 of} Example 1 FIG.
TG-DTA graph for O _7.2 .

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 39/12 ZAA C04B 35/00 ZAAK

Claims (4)

(57) [Claims] 1. The composition formula is Ln _a Sr _b Cu _3-x Re _x.
In the metal oxide material represented by O _c , 2.7 ≦ a +
b ≦ 3.3, 0.8 ≦ a ≦ 1.2, 6 ≦ c ≦ 9 and 0.
05 ≦ X ≦ 0.4, and Ln is one or more kinds of elements or atomic groups selected from the element group of Y element and lanthanoid element, a metal oxide material. 2. The metal oxide material according to claim 1, wherein a = 1, b = 2, and Ln is any one of Y, Ho, Dy, and Gd. 3. The metal oxide material according to claim 1, wherein the crystal lattice is tetragonal or orthorhombic, and the lattice constant (c) is 11 Å or more and 12 Å or less. 4. The metal oxide material according to claim 1, which has superconductivity at a temperature of 20 Kelvin or more.