JPH038722A - Production of superconducting film - Google Patents

Abstract

PURPOSE:To obtain a superconducting film having sufficiently high critical current density of 110K phase having the highest critical temperature by depositing an oxide film having specific compositional ratios of metallic elements on a substrate and synthesizing a Pb-doped Bi-type superconducting film from the deposited film. CONSTITUTION:In the process for depositing a Bi-type lamellar perovskite superconducting film, a film having compositional ratios Bi:Pb:Sr:Ca:Cu=1:s:t:u:v (0.6<s<0.9; 0<t<1.5; 0<n<1.5; 1.0+v<3.0) is deposited on a substrate. A single phase having high Tc can be produced in a short time by calcining the deposited film.

Description

Detailed Description of the Invention [Summary] The present invention relates to a method for manufacturing a Bi-based layered perovskite-type high-Tc phase superconducting film, in which a required amount of Pb is doped to form a high-Tc phase, and the Cu content is Optimize high Tc
The purpose is to provide a method for manufacturing a superconducting film that can generate a single phase in a short firing time, and in the process of manufacturing a Bi-based layered perovskite superconducting film, the superconducting film is placed on a substrate. An oxide film for synthesizing the superconducting film is formed by a superconducting film manufacturing method in which the metallic element component of the oxide is represented by the following 2.

Bi:Pb:Sr:Ca:Cu=1:s:L:u:v
However, 0.6<s<0.9. 0<t<1.
5 (Field of Industrial Application) The present invention relates to an improvement in a method for manufacturing a Bi-based conductive film. In particular, it relates to improvements in increasing critical temperature and critical current density.

[Prior Art] As a method for producing a Bi-based superconductor doped with PB, [1i20. ,PbO,5rCO,,
- Funatsuri is the process of mixing powders such as CaC0, CUO, etc., and performing calcination, pulverization, powder compaction, and main firing. The mixing ratio of raw material powders when synthesizing the 110 K phase, which has the highest critical temperature of Bi-based superconductors, is Bi:Pb:Sr:Ca.
:Cu ratio is approximately 1.8:0.34:1.9:2.
It is said that a ratio of about 0:3.0 is good.

[Problems to be solved by the present invention]

It is known that a Bi-based superconducting film has superconducting phases with different critical temperatures (Tc) depending on the number of Cu-0 planes included in the unit cell. So far, formula B
In izSrzCaa-+CunOx, a phase of Tc.10 K for n=1, a phase of Tc.80 for n.2, and a phase of Tc.110 for n.3 are known. Practically speaking, it is desirable to synthesize the 11OK phase, which has the highest critical temperature, but even if the stoichiometric composition of the 110K phase is simply adjusted, the 80K phase is likely to be synthesized. This is CaO
If there is, the firing temperature range (850-870°C
), this is thought to be because the 80 K phase is first stably generated and requires a firing time of over 100 hours to change to the desired 110 K phase.

Takano et al. (Jpn, J, Appl, Phys, 27.19
88. L1041) is a Bi-based superconductor, and it has been reported that 110 is easily generated in a phase ratio axis by adding pbo. Furthermore, the table etc. (Jpn, J, Appl
, Phys, 27.1988. L1476) is 110
Attempting to make the K phase a single phase, the ratio of Bi:Pb:Sr:Ca:Cu was 184:0.34:1.91:2.0.3:3.0
It has been found that a bulk of approximately 100χ of the 110 K phase can be obtained when the temperature is 6.

In normal thin film formation methods (sputtering method, vapor deposition method, etc.),
After depositing the film on the substrate, a heat treatment is applied to synthesize a superconducting film, but in the process, a considerable amount of Pb evaporates, leaving a sufficient amount of 1
No phase is generated in 10. For these issues, p.
It was pointed out that a certain amount of 110 K phase can be synthesized by adding a large amount of b (Appl, Phys,
Lett, 54 pp, 1362-1364.1
989). However, in a film containing a large amount of Pb, needle-like crystals precipitate during firing, making it difficult to synthesize the 110 K phase as a single phase. When the homogeneity of the film becomes t-membered, the critical current density also decreases significantly, making it a major problem to improve the homogeneity of the film.

[Means to solve the problem]

In the process of manufacturing a Bi-based layered perovskite superconducting film, the present invention involves depositing an oxide film on a substrate for synthesizing the superconducting film, in which the composition of the metal element of the oxide is expressed in % by the following formula: This is achieved by a method of manufacturing a superconducting film having the following formula: %::.

In the process of depositing a Bi layered perovskite superconducting film, the present invention deposits slightly more Cu than the stoichiometric composition, while adding Pb in an amount of 0.6 to 0.9 to Bi. , a sufficient amount of 11 with a short firing time.
It is characterized by synthesizing a phase into 0.

The present invention relates to a method for manufacturing a Bi-based superconducting film containing PB, in which PB is added to Bi in a range of 0.6 to 0.9 to form a superconducting phase with a critical temperature of 110. The object of the present invention is to provide a method for manufacturing a superconducting film that has a high critical temperature and a high critical current density by forming a thin film containing a large amount of superconducting material, excellent homogeneity, and high density in a short time.

The reason why Pb is added here in a much larger amount than the optimum addition amount for the bulk is that in thin films, Pb easily evaporates during firing, so in order to promote the formation of a phase in 110, it is necessary to add 0 to 0 to Bi. This is because it is not effective unless .6 or more is added. Further, the reason why the addition amount is 0.9 or less is to suppress partial melting of the film during firing and variations in film composition.

To deposit such a film, pb and Cu must be added during deposition.
It is practical to form a multilayer film in which a B1-5r-Ca-Cu-0 layer and a layer containing PbO and CuO at high concentrations are laminated to prevent loss of PbO and CuO.

(Function) In the present invention, an amorphous film to which a relatively large amount of Pb is added and a slightly large amount of Cu, which easily evaporates during firing, is deposited on a substrate, and then by short firing, a Bii We have synthesized peropskite-type superconductors.

This method makes it difficult to synthesize the 80 K phase during firing,
A thin film containing a large amount of 110 phase, excellent homogeneity, and high density can be formed in a short time. Therefore, films with high critical temperatures and current densities can be synthesized.

〔Example〕

The film was deposited by RF magnetron sputtering.

Spack conditions are shown in Table I.

Table 1 Spuck conditions Substrate temperature 400°C Sputter gas Ar:O□-2:1 Svantha gas pressure IPa High frequency power 75-100W Deposition rate
80 people/min film thickness
0.85μm target has Bi:Sr:Ca:Cu=3:2:
Oxide target I and Pb with a composition ratio of 2:3
0X target ■ and CuO target ■ were used.

Each target was alternately sputtered onto an MgO substrate heated to 400'C, and B1-3r-Ca-Cu
-0 layer pbo, 1 layer, and CuO layer were deposited in multiple layers.

As target ■ [fi:Sr:Ca:Cu=3:
The reason why Bi was increased to 2:2:3 is because bismuth oxide is difficult to deposit. When deposited with Target I, the film composition is 110K phase stoichiometric 2
:2: It becomes close to 2+3. The thickness of each layer is as follows.

B1-5r-Ca-Cu-0 layer: 2000 p
bo layer: 300 people CuO layer = 300 people Each layer was deposited two or more times to obtain a film with a thickness of 1 μm. The results of compositional analysis of the deposited thin film by IcP are as follows.

Bi:Pb:Sr:Ca:Cu=1. O;0.8:1.
It can be seen that 0:1.0:1.6Bi was appropriately placed and Cu was contained in a larger amount than the stoichiometric composition. The above multilayer film was fired in the air at 850°C for 1 hour to obtain a superconducting film. The X-ray diffraction pattern (CuKα) of the obtained film was
As shown in the figure. MgO is diffraction due to Mgo substrate, L is low Tc
The diffraction pattern is due to the phase, and the others are due to the light Tc sum. It can be seen that the film consists of almost a single high-temperature sum. Further, FIG. 2 shows the microstructure of the film as observed by SEM.

It can be seen that the scale-like superconducting crystals overlap with each other in C-axis orientation. Figure 3 shows the temperature change in electrical resistance measured by the DC 4-terminal method. The electrical resistance suddenly decreased from around 120 K and reached zero at 106.5 K. Also, the critical current density is 5.8xlO' at 77.3 K.
A/cm", which is sufficiently large.

[Comparative Example-1] Film with a large amount of PB added (composition ratio immediately after deposition is Bi:P)
b:Sr:Ca:Cu=1.0:1.1:1.0:1.
FIG. 4 shows the X-ray diffraction pattern when a film (0:1.7) was fired at 850° C. for 1 hour. Even if it is fired under the same conditions as the actual Mm example mentioned above, the proportion of the 110 phase does not increase much. In addition, when observing the film with a scanning electron microscope, it was found that C
Large needle-like crystals of a-CuO were observed. 77.3
The critical current density at K is 0.8xlO' A/c+w
”, which is very inferior to the films shown in Examples.

[Comparative Example-2] Film with a small amount of pb added (composition ratio immediately after deposition is Bi:Pb
:Sr;Ca:Cu=1. O:0.6:1. O+1. O
:1.5) when fired at 850'C for 1 hour
The line diffraction pattern is shown in FIG. In this film also 11
0 The proportion of K phase does not increase much. In addition, when observing the film with a scanning electron microscope, no needle-shaped crystals were observed, but
It can be seen that the film is not C-axis oriented and the density of the film is significantly lower than that of the example. The critical current density at 77.3 k is 1.4xlO' A/cm2, which is inferior to the films shown in Examples.

〔Effect of the invention〕

As explained above, according to the present invention, 1, which has the highest critical temperature among the Bii layered perovskite superconductors,
Phase 10 can be synthesized with high purity in a short time, and a Bi-based layered perovskite superconducting film having a sufficiently high critical temperature and a sufficiently large critical 111j flow density can be formed.

[Brief explanation of drawings]

Figure 1 shows the X-ray diffraction pattern of the film obtained according to the present invention, Figure 2 shows the fine structure of the film obtained according to the present invention, and Figure 3 shows the X-ray diffraction pattern of the film obtained according to the present invention. FIGS. 4 and 5 are diagrams showing changes in electrical resistance with temperature; and FIGS. 4 and 5 are diagrams showing X-ray diffraction patterns of films obtained by the comparative example method. ] October 19, 1989 Display of the case 1989 O1 Patent Application No. 144503 Name of the invention Person who amends the manufacturing method of a superconducting membrane Relationship to the case Patent applicant Address Kamiodanaka, Nakahara-ku, Yozaki City, Kanagawa Prefecture Name <522) Fujitsu Limited Representative Takashi Yamamoto

Claims (1)

[Claims] In the process of manufacturing a Bi-based layered perovskite superconducting film, an oxide film is deposited on a substrate to synthesize the superconducting film, and the components of the metal elements of the oxide are as follows: A method for producing a superconducting film characterized by being represented by the following formula. Bi:Pb:Sr:Ca:Cu:1:s:t:u:v However, 0.6<s<0.9, 0<t<1.5 0<u<1.5, 1.0<v <3.0