JPH0310083A - Method for manufacturing superconducting membrane - Google Patents

Abstract

PURPOSE:To produce a superconducting film improved in critical temp. and critical current density by controlling the components of metallic elements in an oxide film by a specific equation at the time of synthesizing a Bi-type lamellar Perovskite-type superconducting film on a substrate. CONSTITUTION:In a process for producing a Bi-type lamellar Perovskite-type superconducting film, a film of oxides for synthesizing the above superconducting film is deposited on a substrate, and the components of the metallic elements of the oxides are controlled so that they satisfy the relations in an equation B:Pb:Sr:Ca:Cu=s:t:1:u:v (where the symbols (s), (t), (u), and (v) stand for >0 to <1.5, >0.5 to <1.5, >0 to <1.5, and >1.5 to <1.7, respectively). By forming the superconducting film in which large amounts of Pb are added and Cu content is slightly increased as mentioned above, the Bi lamellar Perovskite-type superconducting film having sufficiently high critical current density as well as sufficiently high critical temp. can be formed.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a method for manufacturing a Bi-based superconducting film with the addition of PB, by adding a large amount of PB and making the composition ratio of Cu slightly higher than the stoichiometric composition. The purpose is to provide a manufacturing method for forming a superconducting film containing many superconducting phases with a critical temperature of 110, a high critical temperature, and a large critical current density in a short time. In the process of manufacturing a film, an oxide film for synthesizing the superconducting film is deposited on a substrate, and the composition of the metal element of the oxide is expressed by the following formula: Constructed by the manufacturing method.

(Industrial Application Field) The present invention relates to an improvement in a method for manufacturing a bismuth-based Bi-based superconducting film. In particular, it relates to improvements in increasing critical temperature and critical current density.

[Conventional technology]

As a method for producing a Bi-based superconductor doped with pb, Bito, pbo, SrCO3C are used as starting materials.
The process of mixing powders such as aC01 and CUO, calcination, pulverization, powder compaction, and main firing is - Funatsuri. The mixing ratio of raw material powders when synthesizing the 110 K phase, which has the highest critical temperature in the Bi-based conductor, is Bi:Pb:Sr:Ca:C.
The ratio of u is approximately 1.8:0.34:1.9:2.0:
It is said that it is good to set it to about 3.0.

[Problem to be solved by the 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-+CuaOx, a phase of τC=10 for n·1, a phase of Tc=80 for n·2, and a phase of Tc=110 K for n=3 are known. Practically speaking, it is desirable to synthesize the 110 phase, which has the highest critical temperature, but even if the stoichiometric composition of the 110 K phase is simply adjusted, the 80 K phase is easily synthesized.
If O is present, the firing temperature range (850-870"
This is thought to be because in C), the 80 K phase is first stably generated and requires a firing time of over 100 hours to change to the desired 110 phase.

Takano et al. (Jpn, J, Appl, Phys, 27, 19
8B, L1041) reported that by adding pbo, a Bi-based superconductor, 110 is relatively easily produced. Furthermore, the table etc. (Jpn, J, Appl
, Phys, 27, 1988. L1476) is 110
Attempting to make the phase into a single phase, the ratio of Bi:Pb:Sr:Ca:Cu was 1.84:0.34:1.91:2.03:3.06
It has been found that a 110 K phase with a bulk of approximately 100 χ can be obtained when .

In normal thin film formation methods (sputtering method, vapor deposition method, etc.),
After depositing the film on the substrate, heat treatment is applied to synthesize a superconducting film, but in the process, a considerable amount of PB evaporates, and C
u also evaporated slightly. When the amount of Cu decreased, an 80 K phase was synthesized even if the amount of Pb added was optimized, and it was difficult to synthesize a 110 K phase as a single phase.

[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: The present invention, which is achieved by a method for manufacturing a superconducting film represented by the formula %::, involves adding more Pb than the optimum amount of Pb in the bulk in the step of depositing a Bi-based layered perovskite superconducting film. Furthermore, by depositing more Cu than the stoichiometric composition, a sufficient amount of 110 phase is synthesized even if PB evaporates during the heat treatment after deposition.

In order to deposit such a sufficient film, Pb
B1-5r-Ca-Cu-
It is realistic to form a multilayer film in which a 0 layer and a layer containing a high concentration of PbO and CuO are laminated.

[Effect]

In the present invention, a relatively large amount of Pb is added and an amorphous film with a slightly large amount of Cu that evaporates during firing is deposited on the substrate, and then a Bi-based layer is formed by short firing. Synthesize perovskite superconductors.

With this method, it is difficult to synthesize the 80 phase during firing, and the 1
The 10 K phase can be synthesized as almost a single phase. Therefore, a film with a high critical temperature and current density can be synthesized while suppressing the reaction between the substrate and the superconducting film.

〔Example〕

The film was deposited by RF magnetron sputtering.

The sputtering conditions are shown in Table 1.

Table 1 Sputtering conditions Substrate temperature 400°C Sputtering gas A':0□-2:1 Sputtering 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 ■ and pb with a composition ratio of 2:3
o, Targetera II) and CuO target ■ were used.

Each target was alternately sputtered onto a substrate heated to 400'C, and B1-5r-Ca-Cu
A -0 layer, a PbO□ layer, and a CuO layer were deposited in multiple layers. Target ■Bi:Sr:Ca:Cu=3:2:2
The reason why Bi was increased so that the ratio was 3 was because bismuth oxide is difficult to deposit. When deposited with target I, the film composition is 110 phase chemical l film composition '2:2:
'The ratio will be close to 2:3. The thickness of each layer is as follows: B1-5r-Ca-Cu-0 layer: 2000
Layer: 300 CuON: 300 Each layer was laminated twice, and the composition of the obtained thin film was as follows as a result of ICP analysis.

Bi:Pb:Sr:Ca:Cu=1. O:0.8:1.
It can be seen that 0:1.0:1.6B1 was properly placed and contained more Cu 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 is shown in FIG. 1, and it can be seen that the film consists of almost a single high-temperature phase. Further, FIG. 2 shows the fine structure of the film by SEM observation, and it can be seen that the scale-like superconducting crystals are C-axis oriented and overlapped. FIG. 2(b) is an enlarged view of FIG. 2(a).

Figure 3 shows the temperature change in electrical resistance using the DC four-terminal method.The electrical resistance suddenly decreases from around 120,
．． At 5, the electrical resistance became zero. Further, the critical current density was 5.8xlO'A/cII'' at 77.3K, which was sufficiently large.

[Comparative example]

Bi:Pb composition ratio of CuO is almost equal to stoichiometric composition
:Sr:Ca:Cu=1. O:1.0:1.0:1.1
Figure 4 shows the X-ray diffraction pattern of a film obtained by firing a film of 1.5 at 850'C for 1 hour. , it turns out that it does not increase. This is considered to be because Cu evaporates during firing and is lost from the film, causing the composition to deviate from the conditions under which a phase is formed in 110. 77.3K
The critical type 2it density in is 1.2xlO' A/cm
This is inferior to the membranes shown in Examples by one-fourth or less.

〔Effect of the invention〕

As explained above, according to the present invention, 110 has the highest critical temperature among Bii-like perovskite superconductors.
B that can synthesize K phase with high purity and in a short time, has a sufficiently high critical temperature, and has a sufficiently large critical type 2it density.
An i-layer perovskite superconducting film can be formed.

[Brief explanation of drawings]

Fig. 1 shows the X-ray diffraction pattern of the film obtained according to the present invention, Fig. 2 shows the fine structure of the film obtained by SEM observation of the film obtained according to the present invention, and Fig. 3 shows the X-ray diffraction pattern of the film obtained according to the present invention. FIG. 4 is a diagram showing the temperature change in electrical resistance of the obtained film. FIG. 4 is a diagram showing the X-ray diffraction pattern of the film obtained by the method of the comparative example. Procedural amendment (method) % formula % Name of the invention Method for manufacturing superconducting membranes 3゜Relationship with the case Patent application address Address 1-5 Kamiodanaka, Nakahara-ku, Yozaki-shi, Kanagawa Name (522) Fujitsu Stock Company representative Takuma Yamamoto 4゜

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=s:t:l:u:v However, 0<s<1.5, 0.5<t<1.5 0<u<1.5, 1.5<v <1.7