JP2013155425A - Target for making superconductive thin film, method of manufacturing the same, and method of manufacturing oxide superconductive wire rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a target which is not easily cracked in a process of forming a superconductive thin film by a PLD method, and a method of manufacturing the same.SOLUTION: A target for making a superconductive thin film includes a rare earth oxide superconductive sintered body expressed by REBaCuO(RE is one or more elements selected from rare earth elements), and is composed of a sintered body made by sintering a compact of a calcined body of raw material powder including an RE compound, a Ba compound and a Cu compound. The surface of the target is irradiated with a laser beam. The sintered body is composed of an aggregate of a plurality of flat particles, and the plurality of flat particles are piled up while arranging flat surfaces thereof in a direction parallel to the surface and are sintered so as to integrate boundaries of the particles with each other.

Description

  The present invention relates to a target for producing a superconducting thin film, a method for producing the same, and a method for producing an oxide superconducting wire.

The RE-123 oxide superconductor (REBa ₂ Cu ₃ O _x : RE is one or more elements selected from rare earth elements) exhibits superconductivity at a liquid nitrogen temperature and has a low current loss. Is processed into a superconducting wire to produce a superconducting conductor or a superconducting coil for supplying power. As a method for processing this oxide superconductor into a wire, an oxide superconducting thin film is formed on a base material of a metal tape via an intermediate layer, and a stabilization layer is formed on the oxide superconducting thin film. It has been implemented.
The oxide superconducting thin film formed on the oxide superconducting wire is excellent in crystal orientation and must be a thin film free of impurities to obtain excellent superconducting properties. In FIG.

  Pulsed laser deposition (PLD), which is known as one of the technologies for forming oxide superconducting thin films, irradiates a target with a pulsed laser, and is ablated (evaporated and eroded) from the target by the laser irradiation. This is a thin film production technique in which target constituent particles are deposited on a substrate by bringing a jet of plumes of atoms, molecules or fine particles into contact with the substrate, and is applied to the production of semiconductors and oxide superconducting thin films. In addition, when a thin film is produced from a target, there is little compositional deviation between the target and the thin film, so that the PLD method is superior to other thin film production processes when transferring a complicated chemical composition. .

By the way, when producing a superconducting thin film using the PLD method, a sintered compact target obtained by mixing a RE compound, a Ba compound and a Cu compound, molding a calcined calcined powder, and firing the molded body is obtained. It is used.
In general, it is considered that a dense oxide superconducting layer can be formed by using pulverized powder and increasing the density of the sintered body as a sintered body target of this type, so that the particle size is 50 μm or less. A technique for obtaining a sintered body target by performing primary pulverization and then secondary pulverization so that the particle size is 15 μm or less, and compacting and firing the secondary pulverized powder is known (see Patent Document 1).

JP 2009-215629 A

A sintered body made of constituent element particles of an oxide superconductor has a property that cracks easily occur due to stress caused by mechanical impact or thermal expansion. In particular, in the laser vapor deposition method, when the target is irradiated with a high-power pulse laser beam, the target is likely to crack due to the stress due to thermal expansion. There is a problem that the growth of the thin film becomes difficult. Moreover, as a result, continuous film formation becomes difficult, and there is a possibility that it may be a hindrance when a long oxide superconducting wire is manufactured.
In order to prevent the target from cracking, conventionally, a method of improving the mechanical strength of the target by using an organic binder or bonding a backing plate for mounting the target has been performed. There is a high risk of increasing the manufacturing cost, and there is a problem that the number of steps increases.

  The present invention has been made in view of the conventional situation as described above, and is a target for producing a superconducting thin film that is capable of producing a superconducting thin film that is not easily cracked in the film formation process by the PLD method and has excellent superconducting properties And it aims at provision of the manufacturing method.

In order to solve the above problems, a superconducting thin film production target of the present invention is a rare earth oxide superconducting sintered material represented by REBa ₂ Cu ₃ O _x (RE is one or more elements selected from rare earth elements). A superconducting thin film production target comprising a sintered body obtained by firing a compact of a calcined body of a raw material powder containing an RE compound, a Ba compound, and a Cu compound, wherein the surface is irradiated with laser light, The sintered body is an aggregate of a plurality of flat particles, and the plurality of flat particles are stacked with their flat surfaces aligned in a direction along the surface and sintered. .

When the raw material powder containing the RE compound, Ba compound and Cu compound is calcined, flat particles grow as the rare earth oxide superconductor crystal grows. When the calcined body is fired as a compact, the flat particles become flat. A sintered body having an appropriate gap between the particles can be obtained by aligning and aligning the flat surfaces in a direction parallel to the surface.
When a target as a sintered body having gaps between particles is irradiated with laser light, the surface is liquefied, and a jet (plume) of atoms, molecules or fine particles of the material constituting the target is generated by ablation. Here, the presence of the gaps between the flat particles makes it difficult for the breakage of the particles to be transmitted to the whole, and even if some breakage occurs, it is possible to prevent the target from being cracked. Further, since adjacent particles are strongly bonded to each other by sintering, it is possible to prevent the crack from spreading due to the presence of the bonded portion, and thus it is possible to provide a target that is difficult to break even when irradiated with laser light. For this reason, since a stable plume can be generated for a long time, an oxide superconducting thin film can be generated for a long time with a stable film thickness when manufacturing a long oxide superconducting wire.

In the present invention, the density of the sintered body can be set to 63% or more and 78% or less.
If the density of the sintered body is in the range of 63 to 78%, there is an appropriate gap between the particles constituting the target. Therefore, when a plume is generated by irradiating a laser beam, the grain boundary between the particles is formed. It is difficult to cause breakage, and even if some breakage occurs, there is little possibility of being transmitted to the whole, and as a result, it is difficult to cause cracks in the target.
In the present invention, the particle diameter of the plurality of particles constituting the sintered body can be 20 μm or more.
The particles constituting the sintered body preferably have a particle size of 20 μm or more. If the sintered body is a particle having a particle size of 20 μm or more, it has an appropriate gap and can have a target density.

The method for producing a target for producing a superconducting thin film according to the present invention includes a calcining step of calcining a raw material powder containing an RE compound, a Ba compound, and a Cu compound to obtain a calcined body, and crushing the calcined body to pulverized powder. The REBa ₂ Cu ₃ O _x (RE is a rare earth element) is obtained by a pulverizing step of obtaining a molded body by molding the pulverized powder, and a firing step of firing the molded body to obtain a sintered body. A target for producing a superconducting thin film for producing a target including a rare earth oxide sintered body represented by one or more elements selected from within, wherein the rare earth oxidation is performed by a grinding step after the calcining step. A flat pulverized powder of a product is obtained, and this pulverized powder is uniaxially pressed in a molding process to obtain a compacted body in which a plurality of flat pulverized powders are aligned in a direction parallel to the surface, and the compacted body is sintered to obtain a target. It is characterized by

When the raw material powder containing the RE compound, Ba compound, and Cu compound is calcined, flat particles grow as the crystal of the rare earth oxide superconductor grows, and further, the particles are compacted and sintered. A sintered body having an appropriate gap between the particles can be obtained by bonding and integrating the flat surfaces of the particles in a direction parallel to the surface.
When a target as a sintered body having gaps between particles is irradiated with laser light, the surface is liquefied, and a jet (plume) of atoms, molecules or fine particles of the material constituting the target is generated by ablation. Here, the presence of the gaps between the flat particles makes it difficult for the particles to break down, and a target that can prevent the entire target from cracking even if a portion of the breakage occurs can be obtained. In addition, since the adjacent target is strongly bonded to each other by sintering, it is possible to provide a target that is hard to break even when irradiated with laser light because the presence of this bonded portion prevents cracks from spreading. . For this reason, since a stable plume can be generated for a long time, it is possible to provide a target capable of generating a long-time oxide superconducting thin film with a stable film thickness when manufacturing a long oxide superconducting wire.

The present invention is characterized in that a sintered body having a density of 63% or more and 78% or less is obtained by firing the compacted body.
If the density of the sintered body is in the range of 63 to 78%, there is an appropriate gap between the particles constituting the target. Therefore, when a plume is generated by irradiating a laser beam, the grain boundary between the particles is formed. It is difficult to cause breakage, and even if some breakage occurs, there is little possibility of being transmitted to the whole, and as a result, it is difficult to cause cracks in the target.
The method for producing an oxide superconducting wire of the present invention uses a base material provided with an intermediate layer and the target according to any one of the above, irradiating the surface of the target with laser light, and applying target constituent particles to the intermediate The oxide superconducting layer is formed by depositing on the layer.

Since the superconducting thin film target of the present invention has a lower density as a sintered body than the conventional dense high-density target, it is difficult to spread fine cracks when irradiated with laser light during the PLD method. Therefore, a target that can stably generate a plume can be obtained. For this reason, a film can be formed for a long time, and a target capable of producing an oxide superconducting thin film having a stable film thickness when producing a long oxide superconducting wire can be provided.
In addition, a long oxide superconductor having excellent superconducting characteristics can be produced using this target.

The perspective view which shows an example of the target for superconducting thin film preparation concerning this invention. The elements on larger scale of the target. The front view which shows one schematic structure of the film-forming apparatus provided with the target which concerns on this invention. The side view which shows schematic structure of the film-forming apparatus shown in FIG. The perspective view which shows the principal part schematic structure of the film-forming apparatus shown in FIG. FIG. 4 is a perspective view showing an example structure of an oxide superconducting wire that is a target when the film is formed by the film forming apparatus shown in FIG. 3. The figure which shows the X-ray-diffraction pattern of the ground powder for target manufacture manufactured in the Example. The structure expansion photograph of the ground powder for target manufacture manufactured in the example.

Hereinafter, a target for producing a superconducting thin film and a method for producing the same according to the present invention will be described with reference to the drawings.
The target for producing a superconducting thin film according to the present invention is used as a target when an oxide superconducting thin film is formed using a pulse laser deposition method (PLD method). This target includes a rare earth oxide superconducting sintered body and calcining a raw powder containing a rare earth compound, a Ba compound and a Cu compound to obtain a calcined body one or more times, and a calcined body Are pulverized to obtain a pulverized powder, a molding process for molding the pulverized powder to obtain a molded body, and a firing process for firing the molded body to obtain a sintered body. For example, as shown in FIG. 1, the target 11 is made of a disk-shaped sintered body.

The rare earth oxide superconducting sintered body included in the target 11 is an RE-123 oxide superconductor represented by REBa ₂ Cu ₃ O _x (RE is one or more elements selected from rare earth elements). As the constituent element RE, Y, La, Nd, Sm, Eu, Er, Gd, and the like can be given. The RE-123 oxide superconductor is preferably Y123 (YBa ₂ Cu ₃ O _x ) or Gd123 (GdBa ₂ Cu ₃ O _x ).

In addition to the sintered body represented by the composition formula of REBa ₂ Cu ₃ O _x , the target 11 is derived from a rare earth element compound, a Ba compound, and a Cu compound as raw materials used in manufacturing this target. Of different phases may be contained. Here, the heterogeneous phase is a phase having a composition ratio different from that of the sintered body represented by the composition formula of the target REBa ₂ Cu ₃ O _{x as} a parent phase, and is not a composition ratio of RE ₁ Ba ₂ Cu ₃ O _x . This means that RE, Ba, and Cu are complex oxides, or individual oxide particles of RE, Ba, and Cu, or two or more complex oxide particles of these elements.

Further, when an artificial pin is introduced into the oxide superconducting thin film, an artificial pin material may be added to the target. As the artificial pin material introduced into the oxide superconducting thin film, a substance represented by a general formula of ABO _{3 having} a perovskite structure is applied, and examples thereof include BaZrO ₃ (BZO) and BiFeO ₃ (BFO). Y ₂ O ₃ , SnO ₂ , BaSnO _{3 and the} like can also be applied. Since the artificial pin material can be contained in an amount of about 10% by volume or less with respect to the oxide superconducting thin film, particles of these elements may be included in the target in advance.

In the present invention, the density of the target 11 is required to be in the range of 63% or more and 78% or less. Further, as an example, when the particles R constituting the target 11 are enlarged, they are flat-shaped particles as shown in FIG. 2, and these particles R face their flat surfaces R1 in the vertical direction, in other words, the surfaces R1. Are aligned so as to be substantially parallel to the surface of the target 11, and the length direction of each particle R faces the direction indicated by the arrow A in FIG. Has been. Note that, in FIG. 2, in order to easily understand the stacked state of the particles R, an aggregate of particles R having substantially the same size is shown in a simplified manner. However, the structure of the sintered body actually obtained is such that, as shown in the structure photograph in FIG. It is a sintered body structure with a semi-molten state and an integrated shape.
In FIG. 2, an arrow A indicates the pressing direction during molding, and in the case of the disk-shaped target 11 illustrated in FIG. 1, the thickness direction indicates a downward direction. For this reason, in the target 11, the plurality of particles R constituting the target 11 are integrated in a state where the flat surfaces R <b> 1 of the particles R are aligned with the surface parallel to the surface of the target 11. Note that it is not necessary for all the particles R in the target 11 to be oriented in the same direction, and it is sufficient that more than half of the particles R are oriented substantially parallel to the surface.
The target 11 in this example is preferably an aggregate of particles R each having a particle diameter of 20 μm or more, and if the aggregate of particles R having a size in this range, the density is 63% or more and 78%. The following organization is obtained.

In the case of the target 11 having the structure of this example, when the surface is irradiated with laser light in the film formation process of the PLD method, the heat generated on the surface of the target is changed to a high density target such as a density of 90% or more. Compared to the inside is difficult. For this reason, internal stress due to thermal expansion hardly occurs, and generation of cracks can be suppressed. Further, the vicinity of the surface of the target is liquefied at the melting temperature or higher when irradiated with laser light, but liquefaction hardly occurs even in a deep portion inside the target. For this reason, it is avoided that the surface shape of the target 11 largely changes due to bumping of the liquid part inside.
As a result, the target 11 can maintain a smooth surface during the film formation process by the PLD method, and can stably generate plumes, and the fine powder and liquid phase can be generated from the surface by the above-mentioned bumping. It is less likely to scatter due to the phenomenon, and adhesion of particles and droplets to the surface of the deposited superconducting thin film can be prevented.
In addition, droplets are generated on the surface of the deposited superconducting thin film because the heat of the target surface generated by laser light diffusion diffuses to the inside of the target and bumps (expands) inside the target. It can be presumed that one reason is that the coarse particles in the vicinity are blown off and taken into the thin film as droplets.
On the other hand, the target 11 of the present invention has a density of 63 to 78% as described above as compared with a high-density target, and the surface heat is difficult to diffuse inside, so there is a possibility that bumping will occur inside. From this point of view, the occurrence of droplets can be effectively suppressed.
Due to these effects, according to the target 11, an oxide superconducting thin film having excellent surface properties and superconducting characteristics and with reduced film thickness unevenness can be formed for a long time.

When the density exceeds 78% in the target, the density of the target becomes too high, and the surface heat due to the laser light irradiation is easily transmitted to the inside. In addition, there is a high possibility of causing droplet adhesion.
In addition, the particle diameter of the particle having a particle diameter of 20 μm or more is preferably 20 μm or more and 500 μm or less, more preferably 20 μm or more and 100 μm or less. If the particle diameter is out of the above range, it is difficult to obtain a target density, and there is a possibility that target cracking and adhesion of particles and droplets may increase during the film formation process by the PLD method.

Next, an example of a method for manufacturing a target according to the present invention will be described. In the manufacturing method of this example, the target is manufactured by a mixing process, a calcining process, a pulverizing process, a molding process, and a baking process. Hereinafter, each process will be described sequentially.
[1] Mixing process In order to manufacture the target, raw materials corresponding to the composition of the oxide superconducting thin film to be manufactured are prepared. Since the oxide superconducting thin film to be manufactured in this embodiment is an oxide superconducting thin film having a composition ratio of REBa ₂ Cu ₃ O _x , the RE compound, the Ba compound, and the Cu compound are used as raw materials. A target is manufactured using raw materials.
As RE compounds, Ba compounds, and Cu compounds, rare earth oxides, Ba carbonates, and Cu oxides are desirable in view of availability of raw materials and cost.
Among them, Y ₂ O ₃ , BaCO ₃ , and CuO are preferably used when an oxide superconducting thin film having a composition ratio of YBa ₂ Cu ₃ O _x is used. Further, Gd ₂ O ₃ , BaCO ₃ , and CuO are preferably used when an oxide superconducting thin film having a composition ratio of GdBa ₂ Cu ₃ O _x is used. Further, BaO can be used instead of BaCO ₃ .
And _Y 2 _{O 3} powder below, using BaCO ₃ powder and CuO powder is described as an example a case of manufacturing a target.
Y ₂ O ₃ powder, BaCO ₃ powder and CuO powder as raw materials are weighed and mixed so that the ratio of Y: Ba: Cu is 1: 2: 3, and the solvent is mixed with a mixing device such as a wet ball mill device. Grind and mix while adding. This pulverization and mixing can be performed for several hours to several tens of hours.
When the raw materials are weighed and mixed, Y ₂ O ₃ powder, BaCO ₃ powder and CuO powder are in a ratio of Y: Ba: Cu in the range of 1: 2 ± 0.1: 3 ± 0.2. As such, they may be weighed and mixed.

[2] Calcining step Next, a first calcining step is performed in which the pulverized and mixed powder is calcined at 950 to 1000 ° C. for several hours to several tens of hours in an oxygen-containing atmosphere. Next, the obtained calcined body is pulverized and mixed while adding a solvent by a mixing apparatus such as a wet ball mill apparatus. This pulverization and mixing can be performed for several hours to several tens of hours, for example, about 6 to 24 hours. Thereafter, a second calcining step of calcining the pulverized and mixed powder at 950 to 1000 ° C. for several hours to several tens of hours in an oxygen-containing atmosphere is performed as necessary. In this step, the oxygen-containing atmosphere may be an atmosphere containing about 10 to 30% oxygen or air.
[3] Crushing step Thereafter, the calcined product is again pulverized and mixed with a mixing device such as a wet ball mill device while adding a solvent to obtain a pulverized powder. This pulverization and mixing can be performed for several hours to several tens of hours.

[4] Molding step Next, after the pulverized powder is dried, it is sized using a sieve to collect the pulverized powder to be provided to the molded body. Here, the particle size of the collected pulverized powder substantially corresponds to the crystal particle size of the finally obtained sintered body. Therefore, in this step, pulverized powder having a particle size of 20 μm or more is collected. In order to obtain this pulverized powder, the pulverized powder is sieved to prepare a pulverized powder for each particle diameter, and a pulverized powder having a particle diameter of 20 μm or more may be used. Specifically, a pulverized powder having a particle size of 20 μm to 500 μm can be used as the pulverized powder having a particle size of 20 μm or more. Alternatively, pulverized powder having a particle size of 20 to 100 μm can be used.
The collected pulverized powder is press-molded into a target shape, for example, a disk shape.

Here, the molding conditions (temperature / time, press pressure, etc.) are not particularly limited. Further, the pulverized powder may be mixed with a binder and molded.
When the pulverized powder is accommodated in a mold and pressed in a uniaxial direction, the flat particles R are arranged so that their flat surfaces are perpendicular to the pressing direction as shown in FIG. There is a strong tendency to pressurize in an aligned state. For this reason, as shown in FIG. 2, in the state of being the target 11, many particles R are oriented so that the flat surface R <b> 1 is aligned with a surface parallel to the surface of the target 11.
In the calcining step, when the aggregate of Y ₂ O ₃ powder, BaCO ₃ powder, and CuO powder is calcined, the rare earth oxide particles that are produced are ab surfaces due to the crystal structure of the oxide superconductor. Flat particles R preferentially grown so as to become wider are generated.
In order to obtain such particles, the calcining temperature is preferably set to be slightly higher than the calcining temperature in the case of manufacturing this kind of generally known target. The calcining conditions for producing a normal target for forming an oxide superconducting thin film are about 860 to 960 ° C. in the Y system, but calcining in a higher temperature range, for example, about 950 to 1000 ° C. Is preferred. Even in the case of using other rare earth oxides other than the Y-based oxide, it is generally preferable to calcine in the range of 950 to 1000 ° C. In addition, in order to make the rare earth oxide particle | grains produced | generated flat, you may perform high temperature baking about 950-1000 degreeC in the baking process mentioned later.
When the flat-shaped particles R as described above are inserted into the mold and pressed in a uniaxial direction, the flat-shaped particles R are preferentially aligned and overlapped, and folded as shown in FIG. It tends to be pressurized as it is.
[5] Firing step The firing step can be performed at 950 to 1000 ° C for several hours to several tens of hours in an oxygen-containing atmosphere, and the target can be obtained by this firing step. Here, as shown in FIG. 2, the compact compacted in a folded state is slightly melted and bonded and integrated in the overlapping portion of the particles R, and the flat surface R1 of each particle R has a disk shape. The target 1 is sintered in a state aligned in a direction parallel to the surface of the target 1. As a result, a target for forming a rare earth oxide superconducting thin film having the structure shown in the structure photograph of FIG.

Next, an example of a laser vapor deposition apparatus provided with the target according to the present invention, an oxide superconducting thin film produced using the laser vapor deposition apparatus, and an oxide superconducting wire provided with the same will be described.
FIG. 3 is a front view showing a schematic configuration of a laser vapor deposition apparatus provided with a target according to the present invention, FIG. 4 is a side view showing a schematic configuration of the vapor deposition apparatus, and FIG. 5 is a perspective view showing a main part of the vapor deposition apparatus. is there.
One structural example of the oxide superconducting wire 1 to be manufactured using the laser vapor deposition apparatus A configured as shown in FIGS. 1 to 3 is shown in FIG. Note that the oxide superconducting wire shown in FIG. 6 is an example of a target for forming an oxide superconducting layer using the target according to the present invention, and is not limited to the laminated structure described below.
The oxide superconducting wire 1 of this example has an intermediate layer 3 including an alignment layer 4 and a cap layer 5, an oxide superconducting thin film 6, a first stabilizing layer 7, and a second layer above a tape-like substrate 2. The stabilization layer 8 is laminated in this order. The oxide superconducting wire 1 is used as an oxide superconducting conductor with its peripheral surface covered with an insulating coating layer (not shown).

In order to make the oxide superconducting wire 1 having flexibility, the base material 2 is made of a tape-like heat-resistant metal, for example, a nickel alloy such as Hastelloy (trade name, manufactured by Haynes, USA).
As the intermediate layer 3, a structure including an underlayer, an alignment layer 4, and a cap layer 5 described below can be applied as an example.
In the case of providing an underlayer, a multi-layer structure of a diffusion preventing layer and a bed layer, which will be described below, or a structure composed of one of these layers can be used.
The underlayer is a single-layer or multi-layer structure made of silicon nitride (Si ₃ N ₄ ), aluminum oxide (Al ₂ O ₃ , also referred to as “alumina”), GZO (Gd ₂ Zr ₂ O ₇ ), or the like. Is desirable.
The bed layer is, for example, a rare earth oxide such as yttria (Y ₂ O ₃ ), and more specifically, Er ₂ O ₃ , CeO ₂ , Dy ₂ O _3, Er ₂ O ₃ , Eu ₂ O ₃ , Ho ₂ O _3, can be exemplified _La 2 _{O 3,} etc., it can be adopted these single layer or multilayer structure.

Specifically, the alignment layer 4 includes Gd ₂ Zr ₂ O ₇ , MgO, ZrO ₂ —Y ₂ O ₃ (YSZ), SrTiO ₃ , CeO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O ₃ , Examples thereof include metal oxides such as Zr ₂ O ₃ , Ho ₂ O ₃ and Nd ₂ O ₃ . The alignment layer 4 may be a single layer or a multilayer structure.
The alignment layer 4 is formed by a physical vapor deposition method such as sputtering, vacuum vapor deposition, laser vapor deposition, electron beam vapor deposition, or ion beam assisted vapor deposition (hereinafter abbreviated as IBAD); chemical vapor deposition (CVD). Method); organometallic coating pyrolysis method (MOD method); lamination can be performed by a known method for forming an oxide thin film such as thermal spraying. Among these methods, the metal oxide layer formed by the IBAD method is particularly preferable because of its high crystal orientation and high effect of controlling the crystal orientation of the oxide superconducting layer and the cap layer.

The cap layer 5 is epitaxially grown on the surface of the alignment layer 4 and then undergoes a process of grain growth (overgrowth) in the lateral direction (plane direction), and crystal grains are selectively grown in the in-plane direction. Those formed are preferred. Such a cap layer 5 may have a higher in-plane orientation degree than the orientation layer 4. Specifically as the cap layer _{5, CeO 2, LMO (LaMnO} 3), Y 2 O 3, Al 2 O 3, Gd 2 O 3, may be exemplified _Zr 2 _{O 3} or the like.
The oxide superconducting thin film 6 is made of a material composed of REBa ₂ Cu ₃ O _x (RE represents one or more rare earth elements such as Y, La, Nd, Sm, Er, Gd), specifically, Y123 (YBa ₂ Cu ₃ O _x ) or Gd123 (GdBa ₂ Cu ₃ O _x ).
In this embodiment, the oxide superconducting thin film 6 can be formed by a PLD method to be described later using a film forming apparatus A having a configuration described later. The oxide superconducting thin film 6 has a thickness of about 0.5 to 5 μm and preferably a uniform thickness.

  The first stabilization layer 7 formed so as to cover the upper surface of the oxide superconducting thin film 6 is made of Ag or an Ag alloy, and the second stabilization layer 8 is made of a highly conductive metal material. Although it does not specifically limit as a metal material which comprises the 2nd stabilization layer 8, Copper alloys, such as copper, brass (Cu-Zn alloy), and Cu-Ni alloy, are preferable. When the oxide superconducting wire 1 is used for a superconducting fault current limiter, the second stabilization layer 8 is made of a high resistance metal material, and for example, a Ni-based alloy such as Ni—Cr can be used.

In this embodiment, the oxide superconducting thin film 6 of the oxide superconducting wire 1 can be manufactured using a laser deposition apparatus A described below.
The laser vapor deposition apparatus A of the present embodiment directs a jet (plume) of constituent particles struck or evaporated from the target 11 by laser light onto the substrate, and the oxide superconducting thin film 6 formed by the deposition of the constituent particles is applied to the substrate. It is an apparatus for performing a laser vapor deposition method (PLD method) formed above. The laser vapor deposition apparatus A of this embodiment is used when the oxide superconducting thin film 6 is formed on the base material 2 from the state of the laminate in which the intermediate layer 3 is formed by the above-described various methods. it can.

As shown in FIGS. 3 to 5, the laser deposition apparatus A includes a traveling device 10 for traveling the tape-shaped substrate 2 in its longitudinal direction, a target 11 installed on the lower side of the traveling device 10, In order to irradiate the target 11 with laser light, a laser light source 12 provided outside the processing container (vacuum chamber) 18 is provided as shown in FIG. Here, the target 11 is constituted by a target according to the present invention.
The traveling device 10 includes, for example, turning member groups 16 and 17 which are a collection of turning reels for guiding the tape-like substrate 2 that travels along the film formation region 15. , 17 is configured as an apparatus capable of guiding the base material 2 so as to form a plurality of lanes of the base material 2 in the film forming region 15 around the base material 2.

The traveling device 10 and the target 11 are accommodated in a processing container 18, and the processing container 18 is a container that partitions the outside and the film formation space, has airtightness, and has a high vacuum inside. Therefore, the structure has pressure resistance. An exhaust means 19 for exhausting the gas in the processing container is connected to the processing container 18, and in addition, a gas supply means for introducing a carrier gas and a reactive gas is formed in the processing container. The supply means is omitted, and only the outline of each device is shown.
The base material 2 is wound around a supply reel 20 provided inside the processing container 18 so that the necessary length can be fed out. The base material 2 fed out from the supply reel 20 is alternately wound around a turning member group 16 in which a plurality of turning reels 16a are coaxially arranged adjacently and a turning member group 17 in which a plurality of turning reels 17a are arranged coaxially adjacently. It is hung. These turning member groups 16 and 17 are arranged apart from each other inside the processing vessel 18, and the base material 2 is arranged so as to form a plurality of parallel lanes 2A therebetween. The base material 2 is the turning member group. It is configured to be pulled out from 17 and taken up on a take-up reel 21.

Further, turning member groups 16 and 17 and a rectangular box-shaped heater box 23 surrounding the periphery thereof are provided inside the processing container 18, and the base material 2 fed out from the supply reel 20 is an inlet on one side of the heater box 23. The base member 2 is configured to pass through the portion 23 a and reach the turning member group 16, and the base material 2 drawn out from the turning member group 17 is taken up on the take-up reel 21 side through the outlet portion 23 b on the other side of the heater box 23. It is like that. In the apparatus shown in the figure, the heater box 23 is provided to control the temperature of the film forming region 15, but the heater box 23 may be omitted.
A disk-shaped target 11 according to the present invention is provided below an intermediate position between the turning member groups 16 and 17. The target 11 is mounted on and supported by a disk-shaped target holder 25. The target holder 25 is rotatably supported (rotatable) by a support rod 26 attached to the central portion of the lower surface thereof, and is further reciprocated (not shown). 2 is supported by the moving mechanism so as to be able to reciprocate horizontally in the Y ₁ and Y ₂ directions (front-rear direction along the lane 2A of the base member 2 formed between the turning member groups 16 and 17) shown in FIG. The position of the laser beam applied to the surface of the target 11 can be appropriately changed by the rotational movement of the target holder 25 and the reciprocating back and forth movement by these mechanisms.

  An opening 23 c is formed on the lower surface of the heater box 23 above the target 11 so as to correspond to the entire width of the plurality of lanes 2 </ b> A where the base material 2 travels between the turning member groups 16 and 17. Further, in the heater box 23, a heating device 27 such as a hot plate is disposed inside the opening 23c, and the base material 2 that travels in a plurality of lanes between the turning member groups 16 and 17 is disposed on the back side thereof. To be heated to a desired temperature. The heating device 27 may be any device as long as it can heat the base material 2 from the back side thereof, but a general heater composed of a metal disk incorporating a current-carrying electric heater can be used.

As shown in FIG. 1, in the processing container 18, an irradiation window 30 is formed on a side wall 18 </ b> A located on one side of the target 11 with the target 11 as a center so as to face the target 11. An ablation laser light source 12 is disposed outside the irradiation window 30 via a condenser lens 32 and a reflection mirror 33.
As the laser light source 12 for ablation, a laser light source showing a good energy output as a pulse laser such as an excimer laser or a YAG laser can be used. As an output of the laser light source 12, for example, a laser light source having an energy density of about 1 to 5 J / cm ² and a pulse frequency of 200 to 600 Hz can be used.
In the film forming apparatus A shown in FIG. 1, an infrared radiation thermometer 36 for measuring the temperature of the laser light irradiation region on the target surface is installed inside the processing container 18 and obliquely above the target 11. Has been.

Below, the method to manufacture the oxide superconducting thin film 6 using the laser vapor deposition apparatus A shown in FIGS. 3-5 is demonstrated.
In order to form the oxide superconducting thin film 6, a tape-shaped base material in which the intermediate layer 3 is formed on the base material 2 by the various film forming methods described above is used.
After the tape-shaped base material is wound around the take-up reel 21 from the supply reel 20 via the turning member groups 16 and 17 as shown in FIG. 4 or 5, and the target 11 is mounted on the target holder 25, The inside of the processing container 18 is depressurized.
After reducing the pressure to the target pressure, the laser light source 12 collects and irradiates the surface of the target 11 with pulsed laser light.

When the pulsed laser beam from the laser light source 12 is focused and irradiated on the surface of the target 11, the constituent particles on the surface portion of the target 11 are beaten or evaporated to generate a jet (plume) 29 of the constituent particles from the target 11. The oxide superconducting thin film 6 can be formed by depositing the target particles on the cap layer 5 of the tape-like base material 2 that forms and runs the lane 2A.
Here, in the laser vapor deposition apparatus A of this example, since the target 11 is constituted by the target of the present invention, the target 11 is difficult to break when irradiated with laser light, and the target is formed throughout the entire film formation process. 11 The surface can be maintained in a smooth state. For this reason, the plume 29 can be stably generated toward the substrate 2, and the scattering of fine particles and liquid phase from the target surface is suppressed, and the adhesion of particles and droplets and the film thickness unevenness are reduced. An oxide superconducting thin film having excellent characteristics can be formed.

  The superconducting thin film preparation target and the manufacturing method thereof according to the present invention have been described above. In the above-described embodiment, each part constituting the superconducting thin film preparation target and each process constituting the superconducting thin film preparation target are examples. Therefore, it can be appropriately changed without departing from the scope of the present invention. Moreover, in the said embodiment, although the target based on this invention is applied to the laser deposition apparatus of the multi lane system which a base material drive | works multiple lanes, the single lane system laser vapor deposition which a base material drive | works a single lane You may apply to an apparatus.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these Examples.
“Test Example 1”
In order to manufacture the target according to the present invention, first, Y ₂ O ₃ powder, BaCO ₃ powder and CuO powder are weighed so as to have a ratio of Y: Ba: Cu = 1: 2: 3, and φ100 mm alumina The pot was ground and mixed for 48 hours using φ10 mm alumina balls and hexane as a solvent. Each powder used was a powder that passed through 300-μm eyes through a sieve.
The mixture was dried and calcined at 950 ° C. in an oxygen-existing atmosphere for 24 hours. The diffraction pattern was evaluated with respect to the obtained calcined powder by a powder X-ray diffractometer using CuKα rays. The result is shown in FIG. In the X-ray diffraction pattern shown in FIG. 7, high peaks were observed at 2θ values of around 7 °, 23 °, 39 °, and 47 °. It was confirmed that the strength was high. The presence of the 00l diffraction peak indicates that the oxide superconductor crystals constituting the calcined powder have grown in the ab plane.

Next, this calcined body was roughly pulverized to obtain a pulverized powder. In this pulverization step, the particle size distribution may be wide as long as the particle size is 500 μm or less. When using a ball mill, the grinding time is shortened so that the particles are not made finer than necessary.
Subsequently, this pulverized powder was sized using a sieve, and pulverized powders A, B, C, D, E, and F having an average particle diameter shown in Table 1 described later were collected. The collected pulverized powder is formed into a disk shape having a thickness of 4 to 6 mm by a press pressure shown in Table 1 by a uniaxial press using a φ100 mm mold, and sintered at 950 ° C. for 48 hours in the presence of oxygen to be sintered. A target consisting of When crystal grains grow during this firing, the crystal grains are oriented by applying pressure in a uniaxial direction.
In order to confirm the state, a part of the sintered body was cut out and the structure was observed with an electron microscope. The result is shown in FIG. From the structure observation in FIG. 8, it can be seen that when the surface of the sintered body constituting the target was pressed in a uniaxial direction, the crystal grains could be oriented in a plane parallel to the surface. For example, when grain growth occurs in the ab plane of the oxide superconductor, the crystal grains are arranged so that the ab planes are stacked vertically in the direction perpendicular to the surface (surface irradiated with laser light), and the compression direction (surface From the direction, the structure looks like a grid.

<Evaluation>
The press pressure applied during pressing according to the type of pulverized powders A to F used, and the average value (%) of the relative density after sintering are shown in Table 1 described later. The pulverized powders A and B are powders that have passed through a sieve having an opening of 20 μm. The pulverized powders A and B have a particle size of less than 20 μm. The pulverized powders C and D are obtained by removing the powder remaining on the sieve having an opening of 20 μm, and the pulverized powder of less than 20 μm is removed. The particle size of the pulverized powders C and D is 20 to 500 μm. The pulverized powders E and F are obtained by removing the powder remaining on the sieve having an opening of 100 μm, and the pulverized powder having a particle diameter of less than 100 μm is removed. The particle size of the pulverized powders E and F is 100 to 500 μm.
In addition, from the observation result of the sintered body before sintering and the sintered body after sintering, although the sintered body has particles more strongly bonded to each other than the molded body, its crystal particle size and the particle size of the pulverized powder Were substantially the same, and it was confirmed that the particle size distribution during molding was maintained after sintering.
Using the sintered body obtained as described above as a target, the laser vapor deposition method described below was performed to obtain an oxide superconducting thin film.

"Deposition of oxide superconducting thin films"
An amorphous Al ₂ O ₃ diffusion-preventing layer (a-Al ₂ O _{3) is} formed on a tape-shaped base material having a width of 10 mm, a thickness of 0.1 mm, and a length of 10 m made of Hastelloy C-276 (trade name of Haynes, USA). 80 nm), an amorphous Y ₂ O ₃ bed layer (a-Y ₂ O ₃ thickness 30 nm), an MgO intermediate layer (IBAD-MgO thickness 10 nm) by ion beam assisted deposition, A tape-shaped substrate on which a cap layer (thickness: 300 nm) of CeO ₂ by the PLD method was prepared. Using this base material, an oxide superconducting thin film (YBa ₂ Cu ₃ O _x ) was produced by laser vapor deposition using the target created in Test Example 1 using a laser vapor deposition apparatus having the structure shown in FIGS. .
The oxide superconducting thin film is formed by using an excimer laser (KrF: 248 nm) as a laser light source, an energy density of 3.0 J / cm ² , a linear speed of 30 m / h when moving the tape substrate, and a pulse laser Deposition of superconducting oxide thin film on the cap layer to a film thickness of 1500 nm with a repetition frequency of 300 Hz, a heating temperature of the tape-shaped substrate with a hot plate of 800 ° C., and the number of lanes of the substrate arranged between the turning members is 5 lanes Went.
The state of target cracking after this film formation was investigated. The target crack means a case where a visible crack that crosses the target is generated by visual observation.

From the results shown in Table 1, since the relative density of the samples using the pulverized powders of Samples A and B having a particle diameter of less than 20 μm is as high as 88% and 92%, the target is sintered or in the vapor deposition apparatus. It was found that cracking is likely to occur during heating. Moreover, when the target was installed in the laser vapor deposition apparatus and the film-forming experiment was conducted, the target was cracked by laser irradiation.
On the other hand, samples C to F using pulverized powder having a particle size of 20 to 500 μm and a particle size of 100 to 500 μm have a relatively low relative density of 63% to 78%. I understand that I can do it. In Samples C and D, a target having a desired density of 75 to 78% could be obtained.
In addition, samples E and F were hard to harden even when pressure was applied because of the high proportion of coarse particles in the pulverized powder, and it was difficult to produce molded bodies. However, it was possible to produce a molded body with some corners missing. In Samples E and F, the average value of the relative density was low, and the deposition rate during film formation was lower than that of Samples C and D, and the film thickness was less than half during the same deposition time. For this reason, since the manufacturing time is doubled in terms of increasing the film forming speed, it is considered that the use of samples E and F is more disadvantageous in terms of manufacturing efficiency than the use of samples C and D.

  DESCRIPTION OF SYMBOLS A ... Laser vapor deposition apparatus, 1 ... Oxide superconducting wire, 2 ... Base material, 2A ... Lane, 4 ... Intermediate layer, 5 ... Cap layer, 6 ... Oxide superconducting thin film, 7 ... 1st stabilization layer, 8 ... Second stabilizing layer, 11 ... target, 12 ... laser light source, 15 ... deposition region, 16, 17 ... turning member group, 16a, 17a ... turning reel, 18 ... processing vessel, 19 ... evacuation means, 20 ... supply Reel, 21 ... take-up reel, 23 ... heater box, 25 ... target holder, 26 ... support rod, 27 ... heating device, 29 ... jet (plume).

Claims (6)

A raw powder containing a rare earth oxide superconducting sintered body represented by REBa ₂ Cu ₃ O _x (RE is one or more elements selected from rare earth elements), and containing RE compound, Ba compound, and Cu compound A target for producing a superconducting thin film consisting of a sintered body obtained by firing a compact of a calcined body, the surface being irradiated with laser light,
The sintered body is composed of an aggregate of a plurality of flat particles, and the plurality of flat particles are stacked with their flat surfaces aligned in a direction parallel to the surface and sintered. A target for producing a superconducting thin film.   The superconducting thin film production target according to claim 1, wherein the density of the sintered body is 63% or more and 78% or less.   The target for producing a superconducting thin film according to claim 1 or 2, wherein the plurality of particles constituting the sintered body have a particle size of 20 µm or more. A calcining step of obtaining a calcined body by calcining a raw material powder containing an RE compound, a Ba compound, and a Cu compound, a crushing step of crushing the calcined body to obtain a pulverized powder, and molding the pulverized powder. It is represented by REBa ₂ Cu ₃ O _x (RE is one or more elements selected from rare earth elements) by a molding process for obtaining a molded body and a firing process for firing the molded body to obtain a sintered body. A method for producing a target for producing a superconducting thin film for producing a target containing a rare earth oxide sintered body,
A flat pulverized powder of rare earth oxide is obtained by the pulverization process after the calcining process, and the pulverized powder is uniaxially pressed in the molding process to obtain a compacted body in which a plurality of flat pulverized powders are aligned in a direction parallel to the surface. A method for producing a target for producing a superconducting thin film, characterized in that the compact is sintered and used as a target.   The method for producing a target for producing a superconducting thin film according to claim 4, wherein the compacted body is sintered into a sintered body having a density of 63% or more and 78% or less.   Using the base material provided with the intermediate layer and the target according to any one of claims 1 to 3, the surface of the target is irradiated with laser light, and target constituting particles are deposited on the intermediate layer to form an oxide. A method for producing an oxide superconducting wire characterized by forming a superconducting layer.