JPH01172212A - Easily sinterable superconducting material - Google Patents

Abstract

PURPOSE:To provide an easily sinterable superconducting material exhibiting high critical current density by increasing the density by heat-treating and sintering a specified compsn. obtd. by adding a compd. contg. Ag, Pb, etc., in a liquid state to a rare earth element-alkaline earth element-Cu-O compd. CONSTITUTION:The title easily sinterable material has a compsn. consisting of 4-15atom.% rare earth element, 8-25atom.% alkaline earth element, 12-30atom.% Cu, 0.01-5atom.% additional element, and residual atom.% O. The material is produced by heat-treating after admixing a compd. contg. the additional element in the liquid state. Said rare earth element is at least one kind among Y, La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu. Said alkaline earth metal is at least one kind among Ca, Sr, and Ba. Said additional element is at east one kind among Ag, Pb, Ta, Nb, Sb, Bi, V, W, Mo, Cr, Ge, and Sn.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is an easy-to-use material that can be made of rare earth-alkaline earth to copper-oxygen compounds, which can be highly densified and can have a high critical current density. Concerning sinterable superconducting materials.

(Prior art) Many materials have been known to exhibit superconductivity, and among alloys, Nb-based alloys such as NbzGe 'P NbN have a high superconducting S critical temperature (hereinafter referred to as Tc). It was reported about 10 years ago that Nb and Ge have a Tc of 23.6 K (Applied
Physics Lett, 23480 (1973)
] Until recently, no substance with higher Tc was known. Recently, it has been reported that a Ba-La-Cu-0-based composite oxide has a Tc as high as 30 (Zeitschrift fur Physik).

B 64.189 (1986)), and a Y-Ba-Cu-0 Kenhokuai compound having a Tc higher than the boiling point of liquid nitrogen was reported (Phys.

Rev, Lett, 58 911 (1987))
, In addition, the rare earth -B a -Cu -0 Kenhokugo product in which the Y site is replaced with another rare earth element is also Y-Ba-Cu-
It has been reported that it has Tc comparable to that of the 0 prefecture Hokuai product (Jap, J, Appl, Phys, 26 L85
6 (1987)).

When applied to superconducting magnets, Josephson elements, etc., these rare earth - Ba - Cu - 0 Kenhokugo products use liquid helium as a refrigerant, which is expensive and problematic in terms of resources, unlike conventional superconducting materials. There is no need for this, and liquid nitrogen, which is inexpensive and abundant in resources, can be used. however,
Rare earth-alkaline earth-controlled oxygen-based compounds have poor sinterability and can only yield materials with low density. Therefore, the contact area between particles becomes smaller and the critical current density (
(hereinafter referred to as Jc) also becomes low. Densification of rare earth-alkaline earth-controlled oxygen based compounds is required to obtain materials with practical Jc.

[Problem that the invention seeks to solve]

The present invention has been made in consideration of the above points, and has a high Jc
The object of the present invention is to provide an easily sinterable superconducting material that can impart the following properties.

[Means to solve the problem]

As a result of intensive research to solve the above problems, the present inventors found that in rare earth-alkaline earth-controlled oxygen-based compounds, Ag + Pb, Ta, Nb, Sb,
Bt.

V + W + Mo + Cr + Ge or S
The inventors discovered that an easily sinterable superconducting material was obtained by adding and mixing compound n in liquid form and heat-treating the mixture, and that a high Jc was developed by sintering and densifying the material, leading to the completion of the present invention. .

That is, the easily sinterable superconducting material of the present invention has an RC of 4 to 15% as an atomic percentage, where R is Y or La.

Nd, Sum, Eu lGd + Dy + Ho
+ Er + Tm, at least one rare earth element selected from Yb or Lu), 8 to 25% alkaline earth metal (however, the alkaline earth metal is at least one selected from Ca + Sr or Ba). ), 12-30
% Cu, 0.01~5% additive element M (however, the old A
gr Pb, Ta, Nb.

Sb, Bi + V + W * Mo + Cr
*At least one selected from Ge or Sn)
, and the remainder essentially consist of oxygen, and is an easily sinterable material that is heat-treated by adding and mixing a compound containing an additive element in a liquid state.

Hereinafter, the easily sinterable superconducting material of the present invention will be explained in detail.

The easily sinterable superconducting material in the present invention includes Y + La + Nd + Sm + Eu + as rare earth elements.
Gd + Dy.

One or more of Ho + Er + Trl+ Yb and Lu can be used, and the content thereof is 4 to 15% in terms of atomic percentage. If the atomic percentage is less than 4% or more than 15%, a large amount of crystal layers that do not exhibit superconductivity will be generated, resulting in a decrease in Jc, which is not preferable. Therefore, the atomic percentage of rare earth elements is 4
It is preferably ~15%, more preferably 6~15%.
It is 12%.

Alkaline earth metals include Ca + Sr and Ba
One or more of them can be used, and the content is from 8 to 25% in terms of atomic percentage. If the atomic percentage is less than 8%, a superconducting phase may not be generated, and if it exceeds 25%, a large amount of insulating phase will be generated, so Jc
Therefore, the atomic percentage of the alkaline earth metal is preferably 8 to 25%, more preferably 10 to 20%. The copper content is 12-30% in atomic percentage. If the atomic percentage is less than 12% or more than 30%, a large amount of crystalline phase that does not exhibit superconductivity will be generated, resulting in a decrease in Jc, which is preferable. Therefore, the atomic percentage of copper is 12
It is preferably ~30%, more preferably 18%.
~25%.

The additive elements in the present invention include Ag, Pb, T
a.

Nb, Sb, Bi + VtWtMo
, Cr + Ge or Sn, and the amount thereof is 0.01 to 5% as an atomic percentage. Atomic percentage is 06
If it is less than 0.01%, it is not possible to obtain a high-density superconducting material, and if it exceeds 5%, an insulator phase is generated and Jc becomes small, which is not preferable. Therefore, the percentage of these additional elements is preferably 0.01 to 5%, more preferably 0.05 to 3%. 4 In addition, in the present invention, the compound containing the above-mentioned additive element is liquefied and added to the rare earth-alkaline earth-controlled oxygen-based composite oxide powder or the raw material mixture of the superconductor, mixed uniformly, and heated. By processing, it can be made into an easily sinterable superconducting material.

Next, a method for manufacturing the easily sinterable superconducting material of the present invention will be described, but the method is not particularly limited thereto. One method is to synthesize a rare earth-alkaline earth-controlled oxygen compound in advance and then add a liquid compound containing the additive element of the present invention. As a method for synthesizing rare earth-alkaline earth-controlled oxygen compounds, for example, compounds such as rare earth oxides, nitrates, chlorides, carbonates, and oxalates are combined with alkaline earth metals such as calcium, strontium, and barium. After mixing predetermined amounts of compounds such as oxides, nitrates, chlorides, carbonates, and succinates, and copper compounds such as cupric oxide, cupric carbonate, and cupric nitrate, the mixture is heated at a predetermined temperature and at a predetermined temperature. Solid phase reaction by heating under atmosphere or by adding a precipitant such as oxalic acid or ammonium carbonate to a mixture of aqueous solutions of soluble salts such as chlorides or nitrates of rare earth elements, alkaline earth metals or copper. There is a method of synthesis by co-precipitating and then heating and decomposing the coprecipitated compound. Next, the compound containing the additive element of the present invention is added in liquid form to the rare earth-alkaline earth-controlled oxygen compound powder obtained by the above method and mixed uniformly. Compounds containing the additive element include alcoholades, carboxylates, bisbenzene series, phthalocyanine complexes, which are soluble in organic solvents such as hydrocarbons, ketones, alcohols, ethers, or halogen compounds. Alkyl compounds, aryl compounds, cyclopentadienyl complexes, organometallic compounds such as acetylacetone complexes and ethylenediaminetetraacetic acid complexes, or carbonyl compounds, chlorides, bromides, iodides,
It is at least one kind selected from inorganic compounds consisting of nitrates and perchlorates.

If the compound containing the above additive element is liquid, it can be added as is to the powder of the rare earth-alkaline earth-copper-oxygen compound and mixed uniformly. but,
In order to achieve more uniform dispersion, it is preferable to dissolve the compound in an organic solvent and then mix. If the compound is a solid, a method of dissolving it in a suitable organic solvent and then mixing it is required. In order to obtain an easily sinterable superconducting material, it is necessary to uniformly disperse the additive element in the form of fine particles, and this can be achieved by adding a compound containing the additive element in liquid form and then heat-treating it at an appropriate temperature. Can be done. When an organic solvent is used, the heat treatment temperature may be at least the temperature at which the organic solvent evaporates, and at the temperature at which the rare earth-alkaline earth-controlled oxygen-based compound does not sinter.

Other methods for producing the easily sinterable superconducting material of the present invention include:
There is a method in which a compound containing the additive element of the present invention as described above is uniformly mixed in a liquid state into a raw material such as a rare earth compound, an alkaline earth metal, or a copper compound, and then heat-treated at an appropriate temperature. The temperature in this case is rare earth - alkaline earth -
The heat treatment may be performed at a temperature not lower than that at which a copper-oxygen compound or its precursor is generated, preferably at a temperature of 500° C. or higher.

The easily sinterable superconducting material obtained by the above method can be sintered at a relatively low temperature, and by sintering at a temperature of 930°C or higher, it becomes a high-density superconductor with a density of 95% or more of the theoretical density. materials can be obtained.

Such a high-density superconducting material has high mechanical strength and can increase Jc.

Additionally, the additive elements of the present invention have the effect of pinning magnetic flux and can improve Jc in a magnetic field, so they are considered to be effective in application to superconducting magnets and electrical wiring.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

Example 1 Yttrium oxide 8.48 g, barium sulfate 39.
After mixing 20 g and 17.90 g of cupric oxide in a mortar, they were fired in air at a temperature of 960° C. for 12 hours.

The obtained composite oxide was pulverized with a jet mill to obtain powder with an average particle size of 3 μm. 0.0 to 95 g of the composite oxide 1.
After adding 10 mg of a toluene solution in which 0.5 g of tetraisopropoxygermanium was dissolved and mixing in an agate mortar, the toluene was removed by evaporation and heated at a temperature of 100° C. for 30 minutes.

The obtained powder was press-molded into a disk shape at a pressure of 2 tons/-, then sintered and annealed in an oxygen flow at a temperature of 940°C for 24 hours, and then cooled at 60°C/hour. .

The density of the sintered body was 6.03 g/cm'. Next, the sintered body was cut into a rectangular parallelepiped shape, an electrode was attached thereto, and Jc was measured in liquid nitrogen and found to be 210 OA/cd.

Further, as a result of measuring the electrical resistance while flowing a current of 10 mA using the four-probe method, the superconducting critical temperature (hereinafter referred to as Tc) was 91.

Further, the transverse rupture strength was 25 kgf/mu''.

Examples 2 to 11 In Example 1, tetraphenyl lead, pentaethoxy tantalum,
Powders were made and sintered using the same method but with the addition of pentaethoxyniobium, triethoxyantimony, triethoxyvanadyl, pentaethoxytungsten, tetraethoxytin, bisbenzene molybdenum, bisbenzene chromium, or triphenyl bismuth. After making it into a body, the same measurements as in Example 1 were performed. The results are shown in Table 1.

Comparative Example 1 A sintered body was measured using the same method as in Example 1 except that tetraisopropoxygermanium was not added, and the same measurements were performed. The results are shown in Table 1.

Further, the transverse rupture strength was 3.5 kgf/1 m''.

Margin Example 13 In Example 1, 0.05 g of silver nitrate was used instead of tetraisopropoxygermanium, and 20 n+j of methanol was added.
? A powder was prepared in the same manner except that it was added after being dissolved in a sintered body, and then the same measurements as in Example 1 were performed.

The density of the sintered body was 6.13 g/am3, Tc was 92, and JC was 2330 A/cd.

Example 14 In Example 1, 0.05 g of bismuth trichloride was used instead of tetraisopropoxygermanium, and 20 g of acetone was added.
A powder was prepared by the same method except that it was added after being dissolved in mf, and after making a sintered body, the same measurements as in Example 1 were performed.

The density of the sintered body is 6.02 g/am3, Tc is 91, and Jc is 1870A/+J! Met.

Example 15 A composite oxide was synthesized using 6.37 g of erbium oxide instead of yttrium oxide in Example 1, and 1.94 g of the composite oxide, 0.03 g of pentaethoxyniobium, and 0.03 g of tetraisopropoxygermanium were synthesized. A powder was prepared by the same method except that it was added after being dissolved in 20 ml of toluene, and after making a sintered body, the same measurements as in Example 1 were performed.

The density of the sintered body was 6.09 g/am'', Tc was 93, and Jc was 206 OA/cd.

Example 16 Gadolinium oxide 6.05g, barium carbonate 13.15g
After mixing g and 7.95 g of cupric oxide in a mortar,
Further, a solution of 0.6 g of lead acetate trihydrate dissolved in 20 liters of ethanol was added, and the ethanol was evaporated to dryness while mixing. Then, heat treatment was performed at a temperature of 900°C to obtain a composite oxide consisting of gadolinium-barium-copper-oxygen. The composite oxide was made into powder with an average particle size of 3 μm using a jet mill, and then press-molded into a disk shape at a pressure of 2 tons/d.

The compact was sintered and annealed in a flow of oxygen at a temperature of 950° C. for 24 hours, followed by cooling at a rate of 60° C./min.

The density of the sintered body was 6.07 g/cA'. Tc measured in the same manner as in Example 1 was 92, and Jc was 19.
It was 90A/cJ.

〔Effect of the invention〕

As explained above, since the easily sinterable superconducting material according to the present invention can be made highly dense, it has high mechanical strength and can have a high critical current density. Therefore, it can be applied to various uses and is extremely useful industrially.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] (1) The composition expressed in atomic percentage is 4-15% rare earth elements, 8-25% alkaline earth metals, 12-30% copper, 0.01-5% additional elements, and the balance is substantially oxygen (however, rare earth elements , Y, La, Nd, Sm, E
One or more elements selected from u, Gd, Dy, Ho, Er, Tm, Yb and Lu; Alkaline earth metals are one or more elements selected from Ca, Sr and Ba; addition Elements are Ag, Pb, Ta, Nb, Sb, B
i, V, W. It is at least one element selected from Mo, Cr, Ge, and Sn. ), an easily sinterable superconducting material characterized in that a compound containing an additive element is added and mixed in a liquid state and then heat treated.