JP2003151386A - Polycrystalline thin film and oxide superconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxide superconductor with high critical current density capable of preventing burning by forming an oxide superconductive layer on a polycrystalline thin film with superior conductivity having a crystalline structure with an aligned crystal orientation. SOLUTION: The oxide superconductor 22 is provided with a polycrystalline base material A having conductivity, the polycrystalline thin film B formed on a film forming face of the polycrystalline base material A and having a pyrochlore type crystalline structure represented by a composition formula of AMO A represents one type selected from Tl, Bi, Pd, Cd, Y and RE (rare earth elements), and M represents one type selected from Tc, Ru, Rh, Pd, Re Os, Ir and Pt}, and the oxide superconductive layer C formed on the polycrystalline thin film B.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polycrystalline thin film having a crystal structure with a well-arranged crystal orientation and excellent conductivity, and a crystal structure with such a well-arranged crystal orientation, and having excellent conductivity. The present invention relates to an oxide superconducting conductor having an oxide superconducting layer formed on a polycrystalline thin film and having excellent superconducting properties.

[0002]

2. Description of the Related Art The oxide superconductor discovered in recent years is an excellent superconductor exhibiting a critical temperature exceeding the liquid nitrogen temperature. At present, this type of oxide superconductor is a practical superconductor. There are various problems to be solved for use as One of the problems is that the oxide superconductor has a low critical current density. The problem that the critical current density of the oxide superconductor is low is largely due to the existence of electrical anisotropy in the crystal itself of the oxide superconductor. It is easy to pass electricity in the a-axis direction and b-axis direction of
It is known that it is difficult to pass electricity in the axial direction. From such a viewpoint, in order to form an oxide superconductor on a substrate and use it as a superconducting conductor, an oxide superconductor in a good crystal orientation is formed on the substrate, and,
It is necessary to orient the a-axis or b-axis of the crystal of the oxide superconductor in the direction in which electricity is intended to flow and the c-axis of the oxide superconductor in the other direction.

Therefore, conventionally, on a base material such as a metal tape,
A sputtering apparatus is used to coat an intermediate layer having a good crystal orientation such as MgO or SrTiO ₃ and an oxide superconducting layer is formed on this intermediate layer. However, the oxide superconducting layer formed on the intermediate layer of this kind by a sputtering apparatus is an oxide superconducting layer (for example, a critical current density of several hundred thousand A) formed on a single crystal substrate made of these materials.
/ Cm ²⁾ much lower critical current density than (e.g., 1
000-10,000 A / cm ² ). This is considered to be due to the reason explained below.

In FIG. 9, an intermediate layer 102 is formed on a polycrystalline base material 101 such as a metal tape by a sputtering device.
The cross-sectional structure of the oxide superconducting conductor in which the oxide superconducting layer 103 is formed on the intermediate layer 102 by a sputtering apparatus is shown. In the structure shown in FIG. 9, the oxide superconducting layer 3 is in a polycrystalline state, and a large number of crystal grains 104 are randomly bonded. One of these grains 104
Looking at each one individually, although the c-axis of the crystal of each crystal grain 104 is oriented to a certain degree perpendicular to the substrate surface,
The axes and b-axis are thought to be oriented in random directions.

As described above, each crystal grain of the oxide superconducting layer has a
When the orientations of the axis and the b-axis become disordered, the quantum coupling property of the superconducting state is lost at the grain boundaries where the crystal orientation is disturbed, and as a result, the superconducting properties, especially the critical current density, are likely to decrease. The oxide superconductor is in a polycrystalline state in which the a-axis and the b-axis are not oriented because the intermediate layer 102 formed thereunder is in the polycrystalline state in which the a-axis and the b-axis are not oriented. In addition, the oxide superconducting layer 103
It is considered that this is because the oxide superconducting layer 103 grows so as to match the crystal of the intermediate layer 102 when the film is deposited.

Therefore, the present inventors previously used a special method to improve the orientation of the a-axis and the b-axis on the polycrystalline substrate Y.
If an intermediate layer of SZ (yttrium-stabilized zirconia) is formed and an oxide superconducting layer is formed on this intermediate layer,
It has been found that an oxide superconducting conductor exhibiting a good critical current density can be manufactured, and regarding this technique, Japanese Patent Application No. 4-2
No. 93464, Japanese Patent Application No. 8-214806, Japanese Patent Application No. 8-272606, Japanese Patent Application No. 8-27.
A patent application has been filed in the specification of No. 2607 and the like.

The techniques according to these patent applications are oblique to the normal to the film-forming surface of the polycrystalline base material made of a metal tape when forming a film on the polycrystalline base material using a YSZ target. By performing an ion beam assist method of simultaneously irradiating an ion beam such as Ar ⁺ at an incident angle of 50 to 60 degrees, YSZ crystals with poor crystal orientation are selectively removed, and YSZ with good crystal orientation is This is a technique in which crystals can be selectively deposited, and as a result, a polycrystalline thin film of YSZ can be formed as an intermediate layer having excellent orientation. When a YSZ polycrystalline thin film is formed by such a method, in order to improve the surface smoothness of the polycrystalline thin film,
It has been found that it is preferable to form the film at a low temperature of about room temperature. It is a YSZ polycrystalline thin film at 500 ° C to 1000 ° C.
When the film is formed at a high temperature of ℃, the crystal grains of YSZ become coarse, which causes the surface roughness of the polycrystalline thin film to increase.
The surface becomes uneven. This is because if the surface state of the polycrystalline thin film is poor, the film quality of the oxide superconducting layer formed on the polycrystalline thin film deteriorates, that is, the crystal orientation is disturbed, which is not preferable.

[0008]

By the way, according to the above technique, it is possible to obtain a polycrystalline YSZ thin film in which the a-axis and the b-axis are favorably oriented, and an oxide superconducting layer is formed on this polycrystalline thin film. The oxide superconducting conductor obtained as described above can exhibit a good critical current density, but since the polycrystalline thin film as the intermediate layer is an insulator, the metal formed above and below the polycrystalline thin film is The polycrystalline substrate made of tape and the oxide superconducting layer are electrically insulated. The oxide superconducting conductor in which the polycrystalline base material and the oxide superconducting layer are thus insulated is advantageous in some applications, but may cause a problem when used as a large-capacity conductor. When a large amount of current is passed through the above oxide superconducting conductor, the superconducting state may become unstable due to thermal agitation, in which case it may be necessary to let the current escape to the polycrystalline substrate. However, if the polycrystalline thin film as the intermediate layer is an insulator as described above, the electric current cannot escape to the polycrystalline base material, and the element is burned out.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a polycrystalline thin film having a crystal structure with a well-defined crystal orientation and excellent conductivity. Further, by forming an oxide superconducting layer on a polycrystalline thin film having a crystal structure with such a well-arranged crystal orientation and excellent conductivity, an oxide superconducting conductor having a high critical current density and capable of preventing burnout can be obtained. One of the purposes is to obtain.

[0010]

In order to solve the above-mentioned problems, the polycrystalline thin film of the present invention has a composition formula of AMO formed on the film-forming surface of a conductive polycrystalline substrate (provided that In the composition formula, A is Tl, Bi, Pb, Cd, Y, R
One kind selected from E (rare earth element) is shown, and M is
One kind selected from Tc, Ru, Rh, Pd, Re, Os, Ir and Pt is shown. ) Has a pyrochlore type crystal structure. As the above RE (rare earth element), Sc, La, Ce, Pr, Nd,
Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
It is used by appropriately selecting from m, Yb and Lu.

The above-mentioned pyrochlore type crystal structure is A ₂ M ₂
The composition formula of O ₇ (where A is T
1, Bi, Pb, Cd, Y, and RE (rare earth elements) are shown as one kind, and M is Tc, Ru, Rh, P.
One kind selected from d, Re, Os, Ir and Pt is shown. ) Is preferable. The polycrystalline thin film having the above structure preferably has a resistivity at room temperature of 10 ⁻⁴ to 10 ⁻⁶ Ω · m, and dρ / dT> 0 (ρ is resistivity and T is temperature). In the polycrystalline thin film having the above structure, the grain boundary tilt angle formed by the same crystal axis of each crystal grain of the polycrystalline thin film along a plane parallel to the film formation surface of the polycrystalline base material is 30 degrees or less. Preferably.

In order to solve the above-mentioned problems, the oxide superconducting conductor of the present invention is formed of a conductive polycrystalline base material and a film-forming surface of the polycrystalline base material. (Where A is Tl, Bi,
One of Pb, Cd, Y and RE (rare earth elements) is selected, and M is Tc, Ru, Rh, Pd, Re and O.
One kind selected from s, Ir, and Pt is shown. ), A polycrystalline thin film having a pyrochlore type crystal structure, and an oxide superconducting layer formed on the polycrystalline thin film.

The pyrochlore type polycrystal thin film formed on the polycrystal substrate is advantageous in various points over the conventional YSZ polycrystal thin film when the oxide superconducting layer is provided thereon. Conceivable. First, the lattice constant of ZrO ₂ , which is the main component in YSZ crystals, is 5.14Å.
In the face-centered cubic lattice of O _2, the distance between the atom located at the center of the face and the atom located at the corner of the face (closest interatomic distance) is 3.63Å (0.363 nm),
The lattice constant of the Ru ₂ Bi ₂ O ₇ crystal is 10.3Å (1.03
nm) and the closest interatomic distance is 3.64Å (0.3
64 nm), for which Y ₁ Ba ₂ Cu ₃ O _7-x
The closest interatomic distance of the oxide superconductor with the following composition is 3.8
Considering that it is 1Å (0.381 nm), YS
It is considered that the polycrystalline thin film of the Ru ₂ Bi ₂ O ₇ complex oxide is more advantageous than the polycrystalline thin film of Z in terms of crystal matching. That is, when depositing the atoms of the polycrystalline thin film by carrying out the ion beam assist method, it is considered that the closer the distance between the closest atoms is, the easier the regular deposition of the atoms is. Further, since Ru ₂ Bi ₂ O ₇ has a pyrochlore type crystal structure, another crystal lattice similar to that in the pyrochlore type crystal structure is Bi ₂ Ir ₂ O ₇ (closest interatomic distance 3.65Å ( 0.365 nm)), Pb
₂ Os ₂ O ₇ (closest interatomic distance 3.67Å (0.367
nm)), Pb ₂ Re ₂ O ₇ (closest interatomic distance 3.68)
Å (0.368 nm)) having a pyrochlore type crystal structure represented by any of the composition formulas can be applied.

In addition to these, pyrochlore type crystals
Bi having a structure₂Rh₂O₇, Bi₂Os₂
O₇, Bi₂Re₂O₇ , Pb₂Rh₂O₇ , Pb₂Ru₂O₇
  , Pb₂Ir₂O₇, Gd₂Rh₂O₇, Gd₂Ru₂O₇,
Gd₂Ir₂O₇, Gd₂Os₂O ₇, Gd₂Re₂O₇Nozu
You may employ | adopt the thing shown by the composition formula of either. In addition,
Furthermore, it is assumed that it has a pyrochlore type crystal structure.
Then, the relative ratio of the above A and the above M constituting the above composition formula is
Not only 1: 1 but 0.1: 0.9 to 0.9: 0.1
Any relative ratio can be adopted within the range. Na
In this case, if the crystal structure is not always pyrochlore type,
No defect, defective fluorite type or rare earth C type
However, even in that case, the cubic crystal is maintained.
If it is, it is effective.

Furthermore, since the polycrystalline thin film used in the present invention is required to have conductivity in addition to having a pyrochlore type crystal structure, the composition formula of AMO (where A is Tl , Bi, Pb, C
d represents one selected from Y, RE (rare earth elements), M represents Tc, Ru, Rh, Pd, Re, Os, I
One kind selected from r and Pt is shown. A compound having a pyrochlore type crystal structure represented by (4) is preferably used. A polycrystalline thin film having a pyrochlore type crystal structure represented by such an AMO composition formula has a resistivity at room temperature of about 10 ⁻⁴ to 10 ⁻⁶ Ω · m, and generally dρ / d.
Since T> 0 (ρ is resistivity and T is temperature), the resistivity further decreases at low temperature. Therefore, it sufficiently functions as a stabilizing conductive film provided between the oxide superconducting layer of the oxide superconducting conductor used in a cooling environment such as liquid nitrogen temperature and the polycrystalline substrate. In the composition formula of the above AMO, in particular, the above A
When Bi or Pb is selected as, dρ / dT> 0
It is more preferable because the above tendency is remarkable. On the other hand, a conductive oxide thin film which has been generally known from the past is InO ₂ --S
Although many materials having semiconducting conductivity, such as n ₂ O ₃ , have a dρ / dT <0 in these conventional conductive oxide thin films, and the resistance increases at low temperatures, so the liquid nitrogen temperature It is difficult to use as a stabilizing conductive film of a superconducting conductor used in a cooling environment such as.

[0016]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the polycrystalline thin film of the present invention is formed on a conductive base material. In FIG. 1, A is a conductive tape-shaped polycrystalline base material, and B is a polycrystalline base material. The polycrystalline thin film formed on the upper surface of the base material A is shown. The polycrystalline base material A can be used in various shapes such as a plate material, a wire material, and a tape material, and the polycrystalline base material A can be silver, platinum, stainless steel,
It is made of a material having conductivity and heat resistance, such as a metal material such as Ni alloy such as copper or hastelloy.

The polycrystalline thin film B of this embodiment is made of A ₂ M ₂ O.
₇ (where A is Tl,
One kind selected from Bi, Pb, Cd, Y, and RE (rare earth elements) is shown, and M is Tc, Ru, Rh, Pd, R.
One kind selected from e, Os, Ir and Pt is shown. ), A large number of crystal grains 20 of an aggregate of fine crystals having a cubic pyrochlore type crystal structure are joined and integrated with each other through crystal grain boundaries.
The c-axis of the crystal axis of 0 is oriented at right angles to the upper surface (deposition surface) of the base material A, and the a-axis and the b-axis of the crystal axes of the respective crystal grains 20 are oriented in the same direction. Are in-plane oriented. Further, the c-axis of each crystal grain 20 is oriented at right angles to the (upper surface) film formation surface of the polycrystalline base material A.
The angle between the a-axis (or b-axis) of each crystal grain 20 is 30 (grain boundary tilt angle K shown in FIG. 2).
It is joined and integrated within a range of, for example, within a range of 15 to 25 degrees.

Further, a polycrystalline thin film B having a pyrochlore type crystal structure represented by the above composition formula A ₂ M ₂ O ₇
Is electrically conductive. The polycrystalline thin film B is made of a material having conductivity because an oxide superconducting layer is formed on the polycrystalline thin film B to form a superconducting conductor as described later, and the oxide superconducting conductor has a large capacity. This is because when the superconducting state becomes unstable due to thermal agitation when an electric current is applied, the electric current can be released to the polycrystalline base material A through the polycrystalline thin film B.

The polycrystalline thin film B has a resistivity of 1 at room temperature.
It is preferable that it is 0 ⁻⁴ to 10 ⁻⁶ Ω · m and that dρ / dT> 0 (ρ is resistivity and T is temperature). When the resistivity of the polycrystalline thin film B at room temperature exceeds 10 ⁻⁴ Ω · m, the stability is lost due to insufficient electric conductivity when the temperature is further lowered. In the above composition formula AMO, in particular, the above A
When Bi or Pb is selected as, dρ / dT> 0
It is more preferable because the above tendency is remarkable.

In addition to Ru ₂ Bi ₂ O ₇ , Pb ₂ Bi _{2 is} used as a pyrochlore type composite oxide constituting the crystal grains 20.
O ₇ , Ir ₂ Bi ₂ O ₇ , Os ₂ Bi ₂ O ₇ , Re ₂ Bi ₂ O
₇ , Ru ₂ Pb ₂ O ₇ , Os ₂ Pb ₂ O ₇ , Re ₂ Pb ₂ O ₇ ,
A composite oxide having a composition of Rh ₂ Pb ₂ O ₇ and Ir ₂ Pb ₂ O ₇ can be applied. The resistivity at room temperature of the polycrystalline thin film B of the complex oxide having the composition Ru ₂ Bi ₂ O ₇ is 7 × 10 ⁻⁶ Ω.
・ M, and the resistivity at liquid nitrogen temperature is 1 × 10 ^-6 Ω ・ m
The resistivity of the polycrystalline thin film B of the composite oxide having the composition of Bi ₂ Rh ₂ O ₇ at room temperature is 3 × 10 ⁻⁵ Ω · m, and the resistivity at the liquid nitrogen temperature is 4 × 10 ^−6. Ω · m and Bi ₂ I
The resistivity of the polycrystalline thin film B of the composite oxide having the composition r ₂ O ₇ at room temperature is 2 × 10 ⁻⁵ Ω · m, and the resistivity at the liquid nitrogen temperature is 2 × 10 ⁻⁶ Ω · m. , Pb ₂ Ru ₂ O ₇ has a resistivity of 5 × 1 at room temperature of the polycrystalline thin film B of the composite oxide.
0 ^-6 Ω · m, liquid nitrogen temperature resistivity is 8 × 10 ^-7
Ω · m.

The crystal lattice of the pyrochlore type complex oxide has eight unit lattices in which oxygen ions are ⅛ deficient from the fluorite structure, and has a periodic structure in which the unit lattices are stacked in the vertical and horizontal directions and the depth direction as shown in FIG. have. Therefore, since the unit cell is regarded as a unit cell in the field of X-ray analysis when eight unit cells are overlapped, the lattice constant as the unit cell is 10.3, but the width of the unit cell is 5.15Å ( 0.5
15nm) and the closest interatomic distance is 3.64Å
(0.364 nm).

Pyrochlore-type complex acid used in the present invention
As a compound, Ru₂Bi₂O₇Outside of, Ir₂Bi₂O
₇(Closest interatomic distance 3.65Å (0.365nm),
Lattice constant 10.33), Os₂Pb₂O₇(The closest atom
Distance 3.67Å (0.367nm), lattice constant 10.3
8), Re₂Pb₂O₇(The closest interatomic distance is 3.68Å
(0.368 nm), lattice constant 10.41), Ru₂P
b₂O₇(Closest interatomic distance 3.62Å (0.362n
m), lattice constant 10.25), Rh₂Bi₂O₇(Closest
Atomic distance 3.62Å (0.362 nm), lattice constant 1
0.24), Ir₂Gd₂O ₇(Closest interatomic distance 3.6
2Å (0.362nm), lattice constant 10.25)
You may use this.

When depositing the unit cell of the above complex oxide by the ion beam assisted method under the conditions described later, the closest atomic distance is important, and this value is Y ₁ Ba ₂ C.
a lattice constant of an oxide superconductor having a composition of u ₃ O _7-x 3.81;
Of the closest atomic distance of 3.81Å (0.381 nm), the closest atomic distance is 3.81Å (0.381 nm)
It is desirable to be as close as possible or equivalent to.

Further, as the one having the other pyrochlore type crystal structure, Tl, Bi, Pb, Cd, Y, R
One kind of element A selected from E (rare earth elements) and T
The relative ratio of one element M selected from among c, Ru, Rh, Pd, Re, Os, Ir, and Pt is not limited to 1: 1, but is 0.1: 0.9 to 0.9. An arbitrary relative ratio can be adopted within the range of 0.1.

In addition, even if the closest interatomic distance in the composite oxides of the above compositions is slightly different from the closest interatomic distance of the oxide superconductor, other characteristics such as high speed growth during film formation are obtained. Since there are some films that can be formed, it is needless to say that the complex oxides having various compositions described above can be appropriately selected and used for the purpose of the present invention.

Next, an apparatus and method for manufacturing the above-mentioned polycrystalline thin film B will be described. FIG. 4 shows an example of an apparatus for producing the polycrystalline thin film B, and the apparatus of this example has a structure in which an ion source for ion beam assist is provided in a sputtering apparatus. The apparatus of this example supports the tape-shaped polycrystalline base material A and can feed the tape-shaped polycrystalline base material A onto the base material holder 23 which can be heated to a desired temperature. Base material delivery bobbin 2
4 and a tape-shaped polycrystalline base material A on which a polycrystalline thin film is formed
A base material take-up bobbin 25 for winding up the base material, a plate-like target 36 arranged diagonally above the base material holder 23 at a predetermined interval, and toward the lower surface of the target 36 diagonally above the target 36. The sputter beam irradiation device 38 arranged is opposed to the side of the base material holder 23 at a predetermined interval, and the target 3
6 and the ion source 39 arranged apart from each other are housed in a film forming processing container 40 capable of being evacuated.

The base material holder 23 has a heater inside so that the tape-shaped polycrystalline base material A fed onto the base material holder 23 can be heated to a desired temperature as required. There is. The base material holder 23 is rotatably attached to the support body 23a by a pin or the like, and the tilt angle can be adjusted. The base material holder 23 as described above is arranged in the optimum irradiation region of the ion beam irradiated from the ion source 39 in the film formation processing container 40. In the polycrystalline thin film manufacturing apparatus of this example, the tape-shaped polycrystalline substrate A is continuously fed from the substrate feeding bobbin 24 onto the substrate holder 23, and the polycrystalline thin film is formed in the optimum irradiation region. Bobbin 2 for winding the polycrystalline base material A
By winding the film at 5, it is possible to continuously form a film on the polycrystalline base material A. This base material winding bobbin 25
Are arranged outside the optimum irradiation area.

The target 36 is for forming a desired polycrystalline thin film, and has the same or similar composition as the polycrystalline thin film having a desired composition.
Specifically, the target 36 is Ru ₂ Bi ₂ O ₇ , Pb.
₂ Bi ₂ O ₇ , Os ₂ Bi ₂ O ₇ , Ir ₂ Bi ₂ O ₇ , Re ₂ B
A target of the composite oxide represented by any one of the composition formulas of i ₂ O ₇ or a target having a composition containing a large amount of elements among these three constituent elements which are likely to scatter when formed into a film. To use. Such a target 3
Reference numeral 6 is attached to a target support 36a that is rotatably held by a pin or the like, and the tilt angle can be adjusted.

In addition to the above composition, Rh ₂ Pb ₂ O ₇ ,
Os ₂ Pb ₂ O ₇ , Ir ₂ Pb ₂ O ₇ , Ru ₂ Pb ₂ O ₇ ,
A target of a pyrochlore type complex oxide represented by any one of the composition formulas of Re ₂ Pb ₂ O ₇ may be adopted. Furthermore, as having a pyrochlore type crystal structure,
One element A selected from Tl, Bi, Pb, Cd, Y and RE (rare earth elements) and Tc, Ru, Rh and P
The relative ratio of one element M selected from d, Re, Os, Ir, and Pt is not limited to 1: 1 but is 0.1: 0.9.
A target having an arbitrary relative ratio in the range of up to 0.9: 0.1 can be appropriately adopted.

The sputter beam irradiation device (sputter means) 38 is capable of irradiating the target 36 with an ion beam to knock out the constituent particles of the target 36 toward the polycrystalline base material A. The ion source 39 has substantially the same structure as the sputter beam irradiation device 38, and is configured to house an evaporation source inside the container and to provide a grid for applying a drawing voltage in the vicinity of the evaporation source. . Then, a part of the atoms or molecules generated from the evaporation source is ionized, and the ionized particles are controlled by an electric field generated by a grid and irradiated as an ion beam. There are various methods for ionizing particles, such as a DC discharge method, a high frequency excitation method, and a filament method. The filament type is a method in which a tungsten filament is electrically heated to generate thermoelectrons, which are then collided with evaporated particles in a high vacuum to be ionized. In the polycrystal thin film manufacturing apparatus of this aspect, the ion source 39 having the internal structure shown in FIG. 5A is used. The ion source 39 includes a grid 46, a filament 47, Ar gas, Kr gas, and Xe inside a cylindrical ion chamber 45.
The ion chamber 4 is provided with a gas introduction pipe 48 and the like.
Ions can be emitted from the beam port 49 at the tip of the beam 5 in a beam shape substantially in parallel.

As shown in FIG. 5, the ion source 39 has its central axis S incident on the upper surface (deposition surface) of the polycrystalline base material A (deposition surface (formation surface of the polycrystalline base material A)). They are inclined and opposed to each other at an angle formed by a perpendicular line (normal line) H of the upper surface) and the center line S. The incident angle θ is preferably in the range of 50 to 60 degrees, more preferably in the range of 55 to 60 degrees, most preferably around 55 degrees. Therefore, the ion source 39 is arranged so as to be able to irradiate the ion beam at a certain incident angle θ with respect to the normal line H of the film formation surface of the polycrystalline base material A. The incident angle of such an ion beam is related to the technique that the present inventors have previously applied for a patent. The ion beam applied to the polycrystalline substrate A by the ion source 39 is an Ar gas ion beam, a Kr gas ion beam, a Xe gas ion beam, or these Ar gas, Kr gas, and Xe gas. A mixed ion beam of two or more combinations, eg A
A mixed ion beam of r gas and Kr gas can be used.

A rotary pump 51 and a cryopump 52 for bringing the inside of the film forming processing container 40 into a low pressure state such as a vacuum, and an atmosphere gas supply source such as a gas cylinder are connected to the film forming processing container 40. A low pressure state such as a vacuum inside the film formation processing container 40, and
Argon gas or other inert gas atmosphere can be used. Further, in the film formation processing container 40, a current density measuring device (not shown) for measuring the current density of the ion beam in the container 40, and a pressure gauge 55 for measuring the pressure in the container 40. Is attached. In the polycrystalline thin film manufacturing apparatus of this example, the base material holder 23 is supported by the support member 23 with pins or the like.
Although the tilt angle can be adjusted by being rotatably attached to a, the angle adjustment mechanism is attached to the support portion of the ion source 39 to adjust the tilt angle of the ion source 39 so that the incident angle of the ion beam can be adjusted. However, the angle adjusting mechanism is not limited to this example, and it goes without saying that various structures can be adopted.

Next, using the apparatus having the above structure, the polycrystalline substrate A
The case of forming the pyrochlore type polycrystalline thin film B of the above-mentioned composition such as Ru ₂ Bi ₂ O ₇ will be described below. In order to form a polycrystalline thin film on the tape-shaped polycrystalline substrate A, the target 36 made of the complex oxide described above is used, and the inside of the film formation processing container 40 accommodating the polycrystalline substrate A is vacuumed. The polycrystalline substrate A is sent out from the substrate delivery bobbin 24 to the substrate holder 23 at a predetermined speed, and the ion source 39 and the sputter beam irradiation device 38 are operated. When the target 36 is irradiated with an ion beam from the sputter beam irradiation device 38, the constituent particles of the target 36 are knocked out and fly onto the polycrystalline base material A. Then, the constituent particles struck from the target 36 are deposited on the polycrystalline base material A sent to the base material holder 23, and at the same time, from the ion source 39, for example, Ar
⁺ Ion beam, Kr ⁺ ion beam,
Ion beam Xe ⁺ ions, or, by irradiating a mixed ion beam of Kr ⁺ and Xe ⁺ ions forming a polycrystalline thin film having a desired thickness, the substrate tape-shaped polycrystalline substrate A after the film formation, Take up on the take-up bobbin 25.

[0034] The incident angle θ at the time of irradiating wherein ion beam, good Mashiku 50 degrees, 60 degrees or less range, and most preferably 55 degrees. Here, when θ is 90 degrees, the c-axis of the above-mentioned polycrystalline thin film of the composite oxide is not oriented. Further, when θ is 30 degrees, the polycrystalline thin film of the complex oxide described above does not even have c-axis orientation. If the ion beam irradiation is carried out at an incident angle in the above-mentioned preferable range, the c-axis of the crystal of the above-mentioned polycrystalline thin film of the composite oxide stands. By performing the sputtering while irradiating the ion beam at such an incident angle, the a-axis and the b-axis of the crystal axes of the polycrystalline thin film of the complex oxide formed on the polycrystalline base material A are in the same direction. Can be oriented in the plane along a plane parallel to the upper surface (deposition surface) of the polycrystalline substrate A.

Further, when forming the polycrystalline oxide thin film B of the complex oxide described above, the temperature of the polycrystalline base material A and the ion beam energy of the assisting ion beam are within the specified range in addition to the irradiation angle of the assisting ion beam. It is preferable to set to. It is preferable that the temperature of the polycrystalline base material A is heated to an appropriate temperature of 600 ° C. or lower to form a film, and 90 ° C. is set in order to reduce the grain boundary tilt angle to 25 ° or less from the results of Examples described later. As described above, the temperature is preferably 500 ° C. or less, and is 200 in order to surely set the grain boundary tilt angle to 20 ° or less within this range.
More preferably in the range of ℃ or more and 400 ℃ or less, 300 ℃
Is most preferred. Here, the temperature of 90 ° C. does not require special heating of the substrate, and the device installation environment is at room temperature.
Due to the ion beam irradiating the substrate and the residual heat of the device,
It is the temperature when the substrate is naturally heated.

The ion beam energy has a grain boundary tilt angle of 30.
It is preferably 150 eV or more and 300 eV or less in order to set the grain boundary angle to 20 degrees or less, but 1 to set the grain boundary tilt angle to 20 degrees or less.
A range of 75e or more and 225eV or less is preferable, and 200
eV is most preferred.

By forming a film on the polycrystalline substrate A by the ion assist method with the temperature and the ion beam energy in these ranges, the pyrochlore type polycrystalline thin film B can be formed with good orientation.

1 and 2, Ru ₂ Bi ₂ O ₇ was formed by the above method.
3 shows a polycrystalline base material A on which a polycrystalline thin film B of the above-mentioned complex oxide is deposited. Although FIG. 1 shows a state in which only one layer of crystal grains 20 is formed, it goes without saying that the crystal grains 20 may have a multilayer structure.

The inventors of the present invention assume the following as a factor for adjusting the crystal orientation of the polycrystalline thin film B. The unit cell of the crystal of the polycrystalline thin film B of Ru ₂ Bi ₂ O ₇ is
As shown in FIG. 5 (b), it has an equiaxed face-centered cubic pyrochlore structure, and in this crystal lattice, the substrate normal direction is the <100> axis and the other <010> axes. And <
The 001> axes are all in the direction shown in FIG. Considering an ion beam that is obliquely incident on these directions with respect to the substrate normal, the incident light is incident on the origin O of FIG. 5B along the diagonal direction of the unit lattice, that is, along the <111> axis. In that case, the incident angle is 54.7 degrees. Here, as described above, having good crystal orientation in the incident angle range of 50 to 60 degrees means that the ion beam channel can be used when the incident angle of the ion beam is at or near the above 54.7 degree. Rings most effectively occur, and in the crystal deposited on the polycrystalline base material A, only stable atoms are likely to remain selectively due to the arrangement relationship on the upper surface of the polycrystalline base material A that matches the above angle. As a result, other disordered atomic arrangements that are unstable are sputtered away by the ion beam sputtering effect, and as a result, only crystals of atoms with good orientation are selectively left and deposited. I presume.

Further, even if the polycrystalline thin film B of Ru ₂ Bi ₂ O ₇ is formed under the above conditions, the polycrystalline base material A at the time of film formation
Unless the temperature and the energy of the ion beam at the time of ion beam assist are set within the above-specified range, a sufficient ion beam channeling effect cannot be obtained. Therefore, it is important that the three conditions of the ion beam assist angle, the temperature of the polycrystalline base material A, and the ion beam energy described above are all aligned within a prescribed preferable range.

Next, FIG. 6 and FIG. 7 show an embodiment of the oxide superconducting conductor according to the present invention. The oxide superconducting conductor 22 of this embodiment has a tape-shaped polycrystalline base material A and The polycrystalline thin film B is formed on the upper surface of the polycrystalline base material A, and the oxide superconducting layer C is formed on the upper surface of the polycrystalline thin film B. The polycrystalline base material A and the polycrystalline thin film B are made of the same material as the material described in the above example, and the crystal grains 20 of the polycrystalline thin film B have the grain boundary tilt angle 25 as shown in FIGS. The crystal orientation is within a degree, preferably 17 to 20 degrees.

Next, the oxide superconducting layer C is formed of Ru.₂Bi₂O₇
Of the polycrystal thin film B of FIG.
The c-axis of the crystal grain 21 is arranged at right angles to the upper surface of the polycrystalline thin film B.
The a-axis and the b-axis of the crystal grains 21 ...
As in the case of the polycrystalline thin film B, the surface along the surface parallel to the upper surface of the base material
The grain boundary tilt angle K ′ that is internally oriented and formed by the crystal grains 21 is
It is set within 30 degrees. Constituting this oxide superconducting layer
The oxide superconductor is Y₁Ba₂Cu₃O_7-x, Y₂Ba_FourC
u₈O_x, Y₃Ba₃Cu₆O_xOr (Bi,
Pb)₂Ca₂Sr ₂Cu₃O_x, (Bi, Pb)₂Ca₂Sr
₃Cu_FourO_xComposition or Tl₂Ba ₂Ca₂Cu₃
O_x, Tl₁Ba₂Ca₂Cu₃O_x, Tl₁Ba₂Ca₃Cu_Four
O_xOxides with a high critical temperature represented by
Conductors, but other oxide-based superconductors of these examples
Needless to say, may be used.

The oxide superconducting layer C is formed, for example, on the above-mentioned polycrystalline thin film B by a film forming method such as sputtering or laser vapor deposition.
Since the oxide superconducting layer C formed on the polycrystalline thin film B is formed so as to match the orientation of the polycrystalline thin film B of the pyrochlore type complex oxide such as u ₂ Bi ₂ O _7, Since it has excellent quantum coupling property and there is almost no deterioration of superconducting property at the grain boundary, it becomes easy to pass electricity in the length direction of the polycrystalline base material A, and the YSZ polycrystalline thin film provided on the polycrystalline base material A sufficiently high critical current density equal to or higher than that of the oxide superconducting layer obtained by forming the above is obtained.

As a constituent material of the polycrystalline thin film B, a pyrochlore type represented by the composition formula A ₂ M ₂ O ₇ having conductivity such as Ru ₂ Bi ₂ O ₇ rather than YSZ which is an insulator. Is preferred, and therefore YSZ
Than the one that has an oxide superconducting layer on the polycrystalline thin film of
Towards the Ru ₂ Bi ₂ O _7, etc. of the A ₂ M ₂ O ₇ becomes pyrochlore-type polycrystalline thin film on a B represented by the composition formula that provided an oxide superconductor layer, a current of a large capacity in the oxide superconductor This is because, when the superconducting state becomes unstable due to thermal agitation when energized, a current can be released to the polycrystalline base material A through the polycrystalline thin film B. Further, since the polycrystalline thin film B having the pyrochlore type crystal structure represented by the above composition formula of AMO has a metallic transport property, the polycrystalline base material A having conductivity and the oxide are described below. When it is provided as an intermediate layer between the superconducting layer C and the superconducting layer C, the electrical resistance of the intermediate layer at low temperatures can be reduced.

Further, the polycrystalline thin film B having the pyrochlore type crystal structure represented by the composition formula of AMO has a resistivity at room temperature of about 10 ⁻⁴ to 10 ⁻⁶ Ω · m, and generally dρ / Some of them show dT> 0 (ρ is resistivity and T is temperature). Therefore, the resistivity further decreases at low temperature, so that the oxide superconducting conductor 22 of the oxide superconducting conductor 22 used in a cooling environment such as liquid nitrogen temperature is used. It can sufficiently function as a stabilizing conductive film provided between the layer C and the polycrystalline base material A. Since the polycrystalline thin film B made of the pyrochlore type complex oxide represented by the composition formula A ₂ M ₂ O ₇ has high heat resistance and has a smooth surface, the oxide superconducting layer C and the polycrystalline base material A are Even if it is provided between the oxide superconducting conductor and the oxide superconducting conductor, the superconducting property of the oxide superconducting conductor is not deteriorated and the above-mentioned function can be provided.

Next, an apparatus for forming the oxide superconducting layer C will be described. FIG. 8 shows an example of an apparatus for forming an oxide superconducting layer by a film forming method, and FIG. 8 shows a laser vapor deposition apparatus. The laser deposition apparatus 60 of this example has a processing container 61, and the deposition processing chamber 6 inside the processing container 61.
The tape-shaped polycrystalline base material A and the target 63 can be installed on the second substrate 2. That is, a base 64 is provided at the bottom of the vapor deposition processing chamber 62, and the polycrystalline base material A can be installed on the upper surface of the base 64 in a horizontal state and is supported diagonally above the base 64. A target 63 supported by a holder 66 is provided in an inclined state, the polycrystalline base material A is sent from a drum-shaped tape feeding device 65a onto a base 64, and is wound on a drum-shaped tape winding device 65a. It is configured to be able to. The processing container 61 is connected to a vacuum exhaust device 67 through an exhaust hole 67a so that the inside of the processing container 61 can be depressurized to a predetermined pressure.

The target 63 has a composition similar to or close to that of the oxide superconducting layer C to be formed, or a sintered body of a complex oxide containing a large amount of components that easily escape during film formation or an oxide superconducting material. It consists of a plate such as a body. The base 64 has a built-in heater so that the polycrystalline base material A can be heated to a desired temperature. On the other hand, a laser emitting device 68, a first reflecting mirror 69, a condenser lens 70, and a second reflecting mirror 71 are provided on the side of the processing container 61, and the laser beam generated by the laser emitting device 68 is processed by the processing container. The target 63 can be focused and irradiated through a transparent window 72 attached to the side wall of 61. The laser emitting device 68 is preferably a device such as an excimer laser having a short wavelength and a high light absorption efficiency on the target surface.

Next, a case where the oxide superconducting layer C is formed on the polycrystalline thin film B of the pyrochlore type complex oxide such as Ru ₂ Bi ₂ O ₇ will be described. After the polycrystalline thin film B having the composition of Ru ₂ Bi ₂ O ₇ is formed on the polycrystalline base material A as described above, the oxide superconducting layer is formed on the polycrystalline thin film B. When the oxide superconducting layer is formed on the polycrystalline thin film B, the laser deposition apparatus 6 shown in FIG. 8 is used in this embodiment.
Use 0. Polycrystalline substrate A on which polycrystalline thin film B is formed
Is installed on the base 64 of the laser vapor deposition apparatus 60 shown in FIG. 8, and the vapor deposition processing chamber 62 is decompressed by a vacuum pump. Here, if necessary, oxygen gas may be introduced into the vapor deposition processing chamber 62 to create an oxygen atmosphere in the vapor deposition processing chamber 62. Further, the heater of the base 64 is operated to heat the polycrystalline base material A to a desired temperature.

Next, laser light was generated from the laser light emitting device 68.
Focus the laser beam on the target 63 in the deposition chamber 62.
Irradiate. This makes the constituent particles of the target 63
The particles are unwound or evaporated and the particles are deposited on the polycrystalline thin film B.
accumulate. Here, the substrate temperature is set to 700 to 800 ° C.
It is preferable. Here, when the constituent particles are deposited, Ru₂Bi
₂O₇Even if the polycrystalline thin film B of the
Oxide formed on the polycrystalline thin film B because it is oriented
The c-axis, a-axis, and b-axis of the crystal of the superconducting layer C are also formed in the polycrystalline thin film B.
It is epitaxially grown and crystallized so as to match. Change
To Ru₂Bi₂O₇The closest atomic spacing of the polycrystalline thin film B of
3.64Å (0.364 nm) and Y₁Ba₂Cu₃
O_7-xClosest interatomic distance of oxide superconductors of different composition 3.
Since it is close to 81Å (0.381 nm), it is epitaxial.
Acid with good crystal orientation as a result of smooth growth
A compound superconducting layer C is obtained.

The oxide superconducting layer C formed on the above-mentioned polycrystalline thin film B is in a polycrystalline state. In each of the crystal grains of the oxide superconducting layer C, as shown in FIG. In the thickness direction of the polycrystalline base material A, the c-axis, which is hard to pass electricity, is oriented, and in the longitudinal direction of the polycrystalline base material A, the a axes or the b axes are oriented. Therefore, the obtained oxide superconducting layer is excellent in the quantum coupling property at the crystal grain boundaries and has little deterioration in the superconducting properties at the crystal grain boundaries. Therefore, it is easy to flow electricity in the plane direction of the polycrystalline base material A, and the critical current density Excellent results are obtained.

Further, the oxide superconducting conductor 22 of this embodiment is used.
Is a conductive tape-shaped polycrystalline base material A, a polycrystalline thin film B formed on the upper surface of the polycrystalline base material A, and an oxide superconducting layer C formed on the upper surface of the polycrystalline thin film B. In addition, since the polycrystalline thin film B has a pyrochlore type crystal structure represented by the composition formula of AMO, it has electrical conductivity, and therefore the oxide superconducting conductor 22 is When used as a large-capacity conductor, when a large-capacity current is passed through the conductor 22, the current is passed through the polycrystalline thin film B to the polycrystalline base material A when the superconducting state becomes unstable due to thermal agitation. Since it can be released, it is advantageous because it can prevent burnout.

[0052]

(Example) Using a polycrystalline thin film manufacturing apparatus having the structure shown in FIG. 4, the inside of the film forming processing container of this manufacturing apparatus was evacuated by a rotary pump and a cryopump to obtain 3.0 × 10 ^{−. The} pressure was reduced to ⁴ Torr (399.9 × 10 ⁻⁴ Pa). The tape-shaped substrate has a width of 10 mm and a thickness of 0.
A Hastelloy C276 tape having a surface of 5 mm and a length of 100 cm, which had been mirror-polished, was used. The target is Ru
₂ Bi ₂ O ₇ made of a complex oxide is used, the sputtering voltage is 1000 V, the sputtering current is 100 mA, and the incident angle of the Ar ⁺ ion beam generated from the ion source is the normal to the film-forming surface of the substrate. On the other hand, the temperature is set to 55 degrees, the ion beam transport distance is set to 40 cm, the assist voltage of the ion source is set to 200 eV, and the temperature of the base tape is set to 3
Set at 00 ° C, and in the atmosphere 133.3 × 10 ^-4 Pa
(1 × 10 ⁻⁴ Torr) of oxygen is flowed to deposit target constituent particles on the base material, and at the same time, is irradiated with an ion beam to form a film-shaped Ru ₂ Bi ₂ O ₇ polycrystal with a thickness of 1.0 μm. A thin film was formed.

The obtained polycrystalline thin film of Ru ₂ Bi ₂ O ₇ was subjected to X-ray diffraction by the θ-2θ method using CuKα rays, and was obtained from the pole figure of Ru ₂ Bi ₂ O ₇ . Ru ₂
The full width at half maximum corresponding to the grain boundary tilt angle of the Bi ₂ O ₇ polycrystalline thin film was about 15 degrees. Although it tried to produce a polycrystalline thin film of Ru ₂ Bi ₂ O ₇ in the same conditions by setting the incident angle of the ion beam 60 degrees, good orientation Ru ₂ Bi ₂ O ₇
Of Ru ₂ having a good orientation, although it is slightly deteriorated in the sample obtained when it is set to 50 degrees.
Bi ₂ O ₇ could be obtained. In addition, less than 50 degrees and 60
Although the incident angle exceeding 100 degrees has not been tested, from the accumulation of the technology according to the patent application of the present inventors, the incident angle of the ion beam in the ion beam assist method,
Even if the incident angle is set to less than 50 degrees and more than 60 degrees,
It can be easily estimated that an intermediate layer having good orientation cannot be obtained. The resistivity of the obtained Ru ₂ Bi ₂ O ₇ polycrystalline thin film at room temperature was measured to be 7 × 10 ⁻⁶ Ω · m.
The resistivity at the liquid nitrogen temperature was measured and found to be 1 × 10 ⁻⁶ Ω · m.

Next, an oxide superconducting layer was formed on the polycrystalline thin film of Ru ₂ Bi ₂ O ₇ by using a laser vapor deposition apparatus having the structure shown in FIG. 8 to prepare an oxide superconducting conductor. Here, a target made of an oxide superconductor having a composition of Y ₁ Ba ₂ Cu ₃ O _7-x was used as the target. Further, the inside of the vapor deposition processing chamber was depressurized to 26.6 Pa (2 × 10 ⁻¹ Torr), and laser vapor deposition was performed at a substrate temperature of 700 ° C. A KrF excimer laser with a wavelength of 248 nm was used as a laser for target evaporation. Then, heat treatment was performed at 400 ° C. for 60 minutes in an oxygen atmosphere. The obtained oxide superconducting conductor has a width of 1.0 cm and a length of 100 cm. This oxide superconducting conductor was immersed in liquid nitrogen, and the critical current density was determined for the central portion of 10 mm in width and 10 mm in length by the 4-terminal method. Jc = 1.0 × 10 ⁶
An excellent value of (A / cm ² ) could be obtained.

(Comparative Example) YSZ on Hastelloy C276 tape was carried out in the same manner as in the above example except that the polycrystalline thin film manufacturing apparatus having the structure shown in FIG. 4 was used and YSZ (yttrium-stabilized zirconia) was used as the target. Was formed into a polycrystalline thin film. The resistivity of the obtained YSZ polycrystalline thin film was measured at room temperature to be 10 MΩ · m, and the resistivity at liquid nitrogen temperature was measured to be 20.
It was 0 MΩ · m. Next, an oxide superconducting conductor was produced by forming an oxide superconducting layer on the above-mentioned YSZ polycrystalline thin film in the same manner as in the above example, using the laser vapor deposition apparatus having the configuration shown in FIG. The oxide superconducting conductor obtained in the comparative example was immersed in liquid nitrogen, and the width of the central portion was 10 m by the 4-terminal method.
When the critical current density was determined for the part having a length of m and a length of 10 mm, a value of Jc = 0.9 × 10 ⁶ (A / cm ² ) could be obtained.

From the above results, the oxide superconducting conductor of the example in which the oxide superconducting layer was formed on the Ru ₂ Bi ₂ O ₇ polycrystalline thin film having excellent crystal orientation and conductivity was YSZ polycrystalline. It was demonstrated that an excellent critical current density equal to or higher than that of the oxide superconducting conductor of the comparative example in which the oxide superconducting layer was formed on the thin film was obtained.

[0057]

As described above, the polycrystalline thin film of the present invention has the composition formula of AMO (where A is the same as the composition formula
Represents one kind selected from Tl, Bi, Pb, Cd, Y and RE (rare earth elements), and M represents Tc, Ru and R
One kind selected from h, Pd, Re, Os, Ir, and Pt is shown. ), It has a pyrochlore type crystal structure, and therefore has a crystal structure with a uniform crystal orientation and excellent conductivity. Further, the oxide superconducting conductor of the present invention has a polycrystalline base material having conductivity and a pyrochlore type crystal structure represented by the composition formula of MO formed on the deposition surface of the polycrystalline base material. Since it has the polycrystalline thin film which it has and the oxide superconducting layer formed on this polycrystalline thin film, it has a high critical current density. Also, when this oxide superconducting conductor is used as a large-capacity conductor, when a large-capacity current is passed through this conductor, the current is passed through the polycrystalline thin film when the superconducting state becomes unstable due to thermal agitation. Since it can be released to the polycrystalline base material, it is advantageous because it can prevent burnout.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cross section of an embodiment of a polycrystalline thin film of a pyrochlore type complex oxide formed on a conductive substrate.

FIG. 2 is an enlarged plan view showing crystal grains of the polycrystalline thin film shown in FIG. 1, crystal grain directions thereof and grain boundary tilt angles.

FIG. 3 is a conceptual diagram showing a crystal lattice of a pyrochlore type polycrystalline thin film having a composition of Ru ₂ Bi ₂ O ₇ .

FIG. 4 is a configuration diagram showing an example of an apparatus for producing a polycrystalline thin film according to the present invention.

5A is a configuration diagram showing an example of an ion source of the apparatus shown in FIG. 4, and FIG. 5B is an explanatory diagram of an ion beam incident angle.

6 is a configuration diagram showing an oxide superconducting layer formed on the polycrystalline thin film shown in FIG.

7 is an enlarged plan view showing crystal grains of the oxide superconducting layer shown in FIG. 6, the crystal axis direction thereof, and a grain boundary inclination angle.

8 is a configuration diagram showing an example of an apparatus for forming an oxide superconducting layer on the polycrystalline thin film shown in FIG.

FIG. 9 is a cross-sectional view showing an example of a conventional oxide superconducting conductor.

[Explanation of symbols]

A ... Polycrystalline base material, B ... Polycrystalline thin film, C ... Oxide superconducting layer, H ... Normal line, K ... Grain boundary tilt angle, 20 ... Crystal grain, 22
... Oxide superconducting conductor.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 39/24 H01L 39/24 B

Claims (4)

[Claims] 1. A composition formula of AMO formed on a film-forming surface of a polycrystalline base material having conductivity (wherein A is Tl, Bi, Pb, Cd, Y, RE (rare earth). Element) selected from the group consisting of Tc and R
One kind selected from u, Rh, Pd, Re, Os, Ir and Pt is shown. ), Which has a pyrochlore type crystal structure. 2. The resistivity at room temperature is 10 ⁻⁴ to 10 ⁻⁶ Ω · m.
And dρ / dT> 0 (ρ is resistivity, T is temperature)
2. The polycrystalline thin film according to claim 1, wherein 3. The grain boundary tilt angle formed by the same crystal axis of each crystal grain of the polycrystalline thin film along a plane parallel to the deposition surface of the polycrystalline base material is set to 30 degrees or less. The polycrystalline thin film according to claim 1 or 2, which is characterized. 4. A polycrystalline base material having conductivity, and a composition formula of AMO formed on the film formation surface of the polycrystalline base material (wherein A is Tl, Bi, Pb, C
d represents one selected from Y, RE (rare earth elements), M represents Tc, Ru, Rh, Pd, Re, Os, I
One kind selected from r and Pt is shown. ) A polycrystalline thin film having a pyrochlore type crystal structure and an oxide superconducting layer formed on the polycrystalline thin film, and an oxide superconducting conductor.