JP2635677B2 - Method for producing oxide superconductor precursor - Google Patents

Description

The present invention relates to a method for producing a Y-Ba-Cu-O-based oxide superconductor precursor.

[Prior art and its problems] In recent years, oxide superconductors composed of rare earth elements such as Y ₁ Ba ₂ Cu ₃ O _7- δ (δ ≒ 0.2 to 0.3), alkaline earth metals, copper and oxygen have been discovered. I have. These oxide superconductors are liquid
A much economical compared to metal superconductors exhibiting superconductivity at conventional liquid He temperature for a superconductor with N ₂ temperature or higher
Use in various fields is being considered.

By the way, the above-mentioned oxide superconductors are brittle and cannot be plastically processed like metal materials.To process them into wires etc., powder metallurgy is mainly used, for example, Y ₂ O ₃ , BaCO ₃ , C
calcined raw material powder of uO, which pulverized and classified to calcined powder and without, or overmolding the powder onto a substrate, or distraction processed and filled into Ag tube or the like, which is then O ₂ containing A method of heating and sintering in an atmosphere to obtain an oxide superconducting molded body has been adopted.

However, in the above-mentioned calcined powder production, it takes a long time to pulverize and classify the calcined body, and the calcined powder obtained has a large variation in particle size, and further, impurities are mixed in from a grinder such as a ball mill. And so on.

For this reason, a spray heating reaction method has been proposed in which a raw material of an oxide superconductor is dissolved in a solvent, and this solution is atomized, supplied to a flame, and heated and reacted to produce a precursor of the oxide superconductor. ing.

This method has the advantage that the reaction time is very short and there is almost no contact with the container or jig, so that a precursor of high purity can be obtained.

By the way, in the case of the Y-Ba-Cu-O system, in the above-mentioned spray heating reaction method, each element of Y, Ba, and Cu is dissolved at an atomic ratio of 1: 2: 3 in each droplet constituting the atomized body. The elements Y, Ba, and Cu are heated by a flame and take in O ₂ in the droplet or in the atmosphere to react and react with the oxide superconductor represented by the chemical formula of Y ₁ Ba ₂ Cu ₃ O _X It becomes a body precursor.

The above-mentioned oxide superconductor precursor is subjected to a predetermined heat treatment in an oxygen-containing atmosphere, and Y ₁ Ba ₂ Cu ₃ O _7- δ (δ = 0.2 to 0.
3) The oxide superconductor represented by the chemical formula of 3) has an atomic ratio of Y, Ba, and Cu of the constituent elements of 1: 2: 3, respectively.
The superconducting characteristics are best exhibited when the ratio is.

However, the oxide superconductor precursor produced by the spray heating reaction method often becomes a complex oxide deficient or excess of rare earth elements such as Y, and such a precursor is high even when heat-treated in an oxygen-containing atmosphere. There is a problem that superconductivity cannot be obtained.

[Means and actions for solving the problem]

The present invention has conducted intensive studies in view of such circumstances, and has found that the supply ratio of H ₂ gas and O ₂ gas that generate a flame in the production of a Y-Ba-Cu-O-based oxide superconductor precursor by a spray heating reaction method. As a result, the present inventors have found that the amount of Y in the precursor to be produced is greatly affected by the above-mentioned method, and further studied this point. As a result, the method of the present invention can be achieved.

That is, the present invention weighs a compound containing an element such as Y, Ba, and Cu in a ratio of 1: 2: 3 of Y: Ba: Cu, respectively, dissolves each in a solvent, atomizes the solution, and sprays the solution in a flame. In the method of producing a precursor of the oxide superconductor represented by the chemical formula of Y ₁ Ba ₂ Cu ₃ O _X by heating the atomized material by the flame, the flame for heating the atomized material The supply ratio of hydrogen gas and oxygen gas for generation is 2.5 to 3.5 oxygen gas per 1 volume of hydrogen gas.
A method for producing an oxide superconductor precursor characterized by having a capacity.

In the present invention, examples of the compound containing each of the constituent elements of the oxide superconductor represented by the chemical formula of Y ₁ Ba ₂ Cu ₃ O _7- δ include, for example, acetate, nitrate, halide, and organic compound of Y, Ba, and Cu, respectively. Metal compounds and the like.

As a method of atomizing the compound in the present invention, for example, each of the compounds is dissolved in a solvent such as water,
A method of atomizing this with an ultrasonic nebulizer or the like is used.

As a method for continuously supplying the above-mentioned mist to the flame, it is preferable to transport the mist on a carrier gas such as air, O ₂ , N ₂ , Ar because the supply amount can be easily controlled. .

In the present invention, H ₂ gas is used as the fuel for the flame and O ₂ gas is used as the supporting gas, and the supply amounts of both are determined by the O ₂ / H ₂ volume ratio.
The reason for limiting the amount to 2.5 to 3.5 is that the amount of Y in the produced precursor is not contained in a predetermined amount outside the above range. That is, as shown in FIG. 2, Y, B contained in the precursor material
a, Cu, the atomic ratio of Ba and Cu among the atoms does not change at all by the capacity ratio of O ₂ / H ₂ , but the atomic ratio of Y greatly changes, and O ₂ / H ₂ is 2.5 to 3.5. Within the range, the atomic ratio of Y is
It is 0.9 to 1.1, which is almost a value close to 1.

Although the reason why the atomic ratio of Y greatly changes depending on the capacity ratio of O ₂ / H _{2 in} the above is not clearly understood, the flame temperature and the excess oxygen amount in the flame affect the supply amount to the precursor. It is thought that it is.

Y-Ba formed by heating with a flame in the present invention
-Cu-O superconductor precursor, the composite oxide of a plurality oxides having the composition of Y ₁ Ba ₂ Cu ₃ O _X is in an oxygen-containing atmosphere is heated to 850～1,000 ° C. this at a predetermined speed By gradually cooling, it forms a Y-Ba-Cu-O-based superconductor.

In the present invention, the flame temperature is set based on the supply amounts of the H ₂ gas and the O ₂ gas. However, it is preferable that the flame temperature be constantly measured and controlled because it varies depending on the supply amount of the mist as the raw material.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1 FIG. 1 is an explanatory view showing one example of a spray heating reaction apparatus used for carrying out the method of the present invention.

The spray heating reactor includes an ultrasonic nebulizer 2 for atomizing a solution 1 in which a raw material compound is dissolved, a carrier gas pipe 5 for conveying the raw material mist 3 to a burner 4, and a burner 4.
A YSZ (Y-stabilized zirconia) substrate 7 having a thickness of 0.5 mm to which the precursor 6 of the oxide superconductor which has been heated and reacted by the above method is attached.

In the present embodiment, Y (CH ₃ COO) ₃ .4H ₂ O and Ba are used as compounds containing the constituent elements of the Y—Ba—Cu—O-based superconductor.
Using (CH ₃ COO) ₂ .H ₂ O and Cu (CH ₃ COO) ₂ .H ₂ O, weigh each compound so that the molar ratio of Y: Ba: Cu is 1: 2: 3, This is dissolved in water with a composition of Y ₁ Ba ₂ Cu ₃ at a concentration of 0.04 mol /, and this solution 1 is placed in a container in an ultrasonic nebulizer 2, and ultrasonic vibration is applied thereto to atomize the solution 1. The raw material mist 3 was conveyed to the burner 4 by flowing N ₂ gas through the carrier gas pipe 5 at a flow rate of 0.6 / min.

The burner 4 has a quadruple-tube structure. The first nozzle of the central tube has N ₂ gas containing the mist 5 of the raw material, the second nozzle on the outer periphery thereof has H ₂ gas as fuel, and the third nozzle on the outer periphery thereof. Ar for sealing to protect the burner tip from flame heat
Gas, which has as jetting O ₂ gas combustion assisting from the fourth nozzle of the outermost layer, H ₂ jetted from the second nozzle
A flame 9 is generated by the gas and the O ₂ gas for combustion supporting ejected from the fourth nozzle, and the raw material mist 3 is heated in the flame 9 to reduce the Y-Ba-Cu-O-based superconductor precursor to 0.15%. g / min
The Y-Ba-Cu-O-based superconductor precursor 6 was deposited as a 0.1 mm thick film body 8 on a substrate 7 moving in the direction of the arrow disposed in front of the burner 4. .

In the above, the precursors 6 of the Y—Ba—Cu—O-based superconductor were generated by changing the supply ratio of the H ₂ gas and the O ₂ gas that generate the flame 9.

Each precursor of the Y-Ba-Cu-O-based superconductor thus obtained was heated at 950 ° C for 20 hours in an oxygen stream, and then heated at 950 ° C.
Slowly cooled at a rate of 2 ° C / min from ℃ to make a superconductor, Y
The amounts, _Tc and _Jc were measured.

 The results are shown in Table 1 together with the main production conditions.

As is clear from Table 1, the method of the present invention (1
~ 3) means that the atomic ratio of Y is in the range of 0.95 to 1.05
Both T _c and J _c showed high values. On the other hand, according to the comparison method (4,5), the atomic ratio of Y greatly deviates from 1.0 and T _c , J _c
Was low.

In the above embodiment, the Y-Ba-Cu-O-based superconductor precursor adhered on the substrate was heat-treated as it was to form a superconductor. A similar effect can be obtained by performing a heat treatment.

〔effect〕

According to the present invention the method as mentioned above, Y is represented by the chemical formula of Y ₁ Ba ₂ Cu ₃ O _X which is contained a predetermined amount Y-Ba-Cu-O
Y-Ba- obtained by subjecting a precursor of a system-based superconductor to a predetermined heat treatment in an oxygen-containing atmosphere is easily generated.
Cu-O-based superconductors, T _c, and has excellent properties such as J _c, exhibits the industrially remarkable effects.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one example of a spray heating reactor used to carry out the method of the present invention, and FIG. 2 is a diagram showing the O ₂ / H ₂ volume ratio of a flame and the atoms of Y, Ba, and Cu in a precursor. It is a figure showing the relation of a ratio. 1 ... solution, 3 ... mist of raw material, 6 ... Y-Ba-Cu-
O-based superconductor precursor.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-64-52071 (JP, A)

Claims (1)

(57) [Claims] A compound containing an element such as Y, Ba and Cu is weighed in a ratio of 1: 2: 3 of Y: Ba: Cu, respectively dissolved in a solvent, and the solution is atomized to form a flame. In the method for producing a precursor of an oxide superconductor represented by the chemical formula of Y ₁ Ba ₂ Cu ₃ O _X by heating the atomized material by the above-mentioned flame and heating the atomized material, The supply ratio of hydrogen gas and oxygen gas for flame generation is 2.5 to 3.5 oxygen gas to 1 volume of hydrogen gas.
A method for producing an oxide superconductor precursor, wherein the precursor is a capacity.