JPH0464269A - Manufacture of oxide superconductor and manufacture of oxide superconducting thin film - Google Patents

Abstract

PURPOSE:To avoid high pressure heat treatment or drastic heat treatment by heat-treating a molded body of a chemical compound containing Ln-Ba-Cu without oxygen in an ambient atmosphere containing oxygen. CONSTITUTION:A molded body of a chemical compound whose main components include Ln, Ba, and Cu but no oxygen is heat-treated in an oxygen-contained ambient atmosphere or it is heat-treated in an oxygen-contained atmosphere as well after an alloy thin film 4 mainly comprising Ln, Ba and Cu is deposited on the substrate where La is one or more elements in calcium (Ca), yttrium (Y), scandium (Sc) and lanthanum series. This construction makes it possible to obtain a simplified method which does not call for a high pressure oxygen heat treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing an oxide superconductor having a high critical temperature and a method for producing an oxide superconducting thin film. Niobium nitride (N b N) and germanium niobium (NbsG) are used as type binary compounds.
e) etc. (The superconducting transition temperature of these materials is at most 24 f = -
A high-temperature superconductor based on Ba-La-Cu-0 was proposed [J, G, Bednorz and K, A;-Mul
ler, 7-foot system 717z
eitshrift Fur Physik B)-
Condensed Matter, vol. 64.1
89-193 (1986) L Saraban - YIBa2Cu a with higher superconducting critical temperature
O? -X system (123 system) was discovered [M, ni, W
uJ, R, Ashburn, C,J, Torng,
P, H, Hor, R, L, Meng, L, Gao,
Z, J, Huang, Y, Q, Wang
and C0W, Chu, 7 (Physical Review Letters)
Letters) Vol. 58, 908 (1987
)]. Subsequently, recently Y+B consisting of the same Y, Ba, and CU
A system of aaCu40v, s*x (124 system) was discovered in a thin film [A, F, Marshall, R, W, Ba
rton K, Char, A, Kaitulnik,
B, Oh, R, H, Hammond and S
, S. Laderman, 74 Physical Review B (Physical Review B) Vo
I, 37.9353 (1988)]. The details of the superconducting mechanism of this type of material are not clear.The transition temperature may be higher than room temperature, and it is expected that it will have more promising properties as a high-temperature superconducting material than conventional binary compounds. The 123 series is an oxygen-deficient type and is unstable in the surrounding atmosphere, whereas the 124 series has an extremely stable crystal structure.

Problems to be Solved by the Invention However, in the production of the Chigetsu 24 series, in the case of an oxide superconductor as a fired body, heat treatment under an oxygen pressure of several tens of atmospheres is required. Furthermore, in the case of manufacturing oxide superconducting thin films, heat treatment with rapid temperature increases and decreases is required, making it impossible to apply them to devices in combination with other types of materials.The present invention solves these conventional problems. The present invention aims to provide a method for producing an oxide superconductor that does not require high pressure, and a method for producing an oxide superconductor thin film that does not require rapid temperature increases.

Means for Solving the Problems In order to achieve the above objects, the method of manufacturing an oxide superconductor and the method of manufacturing an oxide superconducting thin film Lt of the present invention,
The power to heat-treat a molded body of an oxygen-free compound whose main components are Ln, Ba, and Cu in an oxygen-containing atmosphere.
An alloy thin film mainly composed of Ln, Ba, and Cu is deposited on the substrate, and after the thin film is deposited, it is heat-treated in an atmosphere containing oxygen.4 Here, Ln is Ca, Y, Sc, and one or more elements of the lanthanum series. In general, heat treatment under high pressure oxygen is required to obtain the 124 series.
Since the oxide powders of Cu and Cu are weighed and mixed, uncontrollable oxygen is inevitably present in the molded product, so seeds of the 123 series are created in addition to the 124 series (＼
In order to suppress the growth of the 123 series and grow only the 124 series, heat treatment is required under high pressure oxygen. The method for producing an oxide superconductor of the present invention is as follows: Ln-Ba-C which does not contain oxygen
Since the molded body of the compound u is heat-treated in an atmosphere containing oxygen, oxygen is not constantly supplied to the metal element from the temperature rising stage of heat treatment, and the 124-series, which has a lower crystallization temperature than the 123-series, is selectively grown. By simply setting the heat treatment temperature to the crystallization temperature of the 124 series, high-quality 124 series can be produced without heat treatment under high pressure oxygen.

In the production of 124 series thin films, compared to the production of fired bodies, the thin film bundle is limited by the substrate, so the reason is not clear.Rikishi.Heat treatment under high pressure oxygen is not necessary.During heat treatment, A rapid temperature rise/temperature cooling process was essential.This process is also thought to be used to suppress the growth of the 123 series and encourage the growth of the 124 series, due to the presence of uncontrollable oxygen in the thin film, as in the case of the above-mentioned compact. . In contrast to the conventional method for manufacturing 124-based thin films, the method for manufacturing oxide superconducting thin films of the present invention deposits an alloy thin film of Ln, Ba, and Cu on a substrate, and heat-treats it in an oxygen-containing atmosphere, making adjustments difficult. No possible oxygen exists in the thin film, and oxygen is supplied from outside the thin film in the required amount to Ln, Ba, and CU, and only the 124 series grows by adjusting the composition of the metal elements and adjusting the heat treatment temperature.

Example An embodiment of the present invention will be described below.

First, the present inventors manufactured ItY-Ba-Cu-〇-based superconductor by firing.For both thin films, YBa2
cu30〒-x (123 series) and YBa2Cu2O
The process of crystal growth of 7, 6, (124 series) has been investigated in detail9.As a result, in order to selectively grow 124 series, amorphous molded bodies and thin films containing at least Y, Ba, and Cu are heat-treated. We found that the method of adding force <, there is a decisive difference between manufacturing the 124 series as a fired body and manufacturing it as a thin film. In the case of fired products, high-pressure oxygen heat treatment at 800 to 1000°C and several tens of atmospheres is essential. - People In the case of thin films, the heat treatment temperature is the same as that of the fired body.Although instantaneous heating and rapid cooling (quenching) to liquid nitrogen temperature are indispensable, especially in the production of oxide superconducting thin films, the rapid temperature rise and fall processes are When considering applications in combination with other types of materials, the response and
This extremely narrows the scope of application.

Therefore, the present inventors (L) Y, Ba, Cu at the weighing stage,
As a result of various studies such as a mixture ratio of 0, wind, cloud, and surrounding gas, we newly discovered that when heat-treating compacts and thin films that do not contain oxygen, the high-pressure heat treatment and rapid heat treatment described above can be avoided. FIG. 1 shows a schematic process diagram of a method for producing a 124-based oxide superconductor. In the same figure, it is not clear why the 124-series sintered oxide superconductor 2 was easily produced by subjecting the oxygen-free compact 1 to the normal oxygen heat treatment. be done. In other words, the molded body before heat treatment does not contain oxygen.Oxygen is supplied as the temperature rises during the heat treatment stage.Number of oxygen ions that combine with copper ions from the 123 system in the crystal unit This may be because the 124 series (copper ion valence; average valence of 2.33 for the 123 series and 2.25 for the 124 series), which has a lower valence, is easier to form as a crystal first, or because it is formed before the 123 series. However, Example 1 In this example, we will explain the manufacturing method of oxide superconductors. First, we will try two manufacturing methods of oxide superconductors. Sample a is made of Y2O3, BaCO5, and CuO. Y the powder
:Ba: Cu = 1: 2: Weighed, mixed well, and pressed into a disk shape with a diameter of 5 mB and a thickness of 3 mm.Sample b is Y, BaF.
2. Each powder of Cu is Y: Ba: Cu=1:
2: Weigh and mix well so that the ratio is 4. Sample a
Samples a and b were first heat treated in an oxygen atmosphere of 1 atm for 950 ＼ 5 hours. Figure 2 shows the X-ray diffraction spectra of samples a and b after the oxygen heat treatment. Shown below. Figure 2(a)
shows the spectrum of sample a, and Figure 2 (b) shows the spectrum of sample b, which is oxide superconductor 2. Sample a is YBa2Cus○? This is an X-ray diffraction spectrum consistent with the -X structure (123 system). -Human Sample b has an X-ray diffraction spectrum that matches the YBa2cuaOr, s-x structure (124 system) Regarding superconducting properties, sample a shows semiconducting properties without superconductivity, whereas sample b is the superconducting transition temperature 83K,
Sample a exhibits superconducting properties with a zero resistance temperature of 79 K. Sample A could not have been obtained without oxygen heat treatment at 10 atm or higher. 1<Cu/
It was found that the 124 series can be stably obtained in the range of (Y1Ba)≦1.5. During production (Table 1) It was necessary to rapidly heat-treat the oxide amorphous thin film.This rapid temperature rise was caused by an oxygen atmosphere, and could be considered a reduction process to expel oxygen from the thin film.Therefore, the present inventors We have invented a method for manufacturing oxide superconducting thin films that does not involve such a rapid reduction and temperature rise process, and a schematic diagram of the process is shown in Figure 3.

In this example, we will attempt to manufacture thin films under two different conditions.
The thin film was manufactured using high-frequency magnetron sputtering.Sample C uses Y as a sputtering target.
- Using Ba-Cu-0 oxide fired body, gas pressure 0.5
Unheated MgO (1
00) Even with the amorphous thin film obtained by depositing about 5,000 people on a substrate, the composition of the target was adjusted, and the composition ratio in the film of sample C was Y: Ba: Cu = 1:
Make the ratio 2:4 9 people Sample d is Y-Ba
-Cu alloy target was sputtered under 100 W of high-frequency power in an argon gas atmosphere with a gas pressure of 0.5 Pa, and approximately 5,000 sputters were deposited on an unheated Mg0 (100) substrate 3. This is the alloy thin film 4. By adjusting the composition ratio of the target, the composition ratio in the film of sample d becomes Y: Ba: Cu=1+
Sample C and sample d were then heat-treated at the same time in an oxygen atmosphere of 1 atm.The heating rate and cooling rate during the heat treatment were both 4.
00 °C/hr and L for 30 minutes at 800 °C.The temperature was kept constant.The X-ray diffraction spectrum after heat treatment was
As shown in the figure. Figures 4(a) and 4(b) show the spectra of samples c and cl, respectively. The X-ray diffraction pattern [(Figure 4(a)] obtained from sample C is weak and almost amorphous. Figure 4(b)] shows the C-axis orientation of the 124-based crystal structure.For sample C, the temperature was 100 °C/
The 124 series could not be obtained without a rapid cooling process at a temperature increase rate of more than miη, and only the 123 series could be obtained at a heat treatment temperature of 850 °C or higher. The inventors found that the temperature ranged from 700 to 850 t:
The present inventors have discovered that the 124 series can be made stable with high purity when the following conditions apply.
The present inventors found that the 124 series can be stably obtained in the range of Cu/(Y+B a)≦1.5.
It was found that the critical current density of the 124-based superconductor increases when Ca is substituted with a. The present inventors have also found that the amount of substitution of hca with Y is effective when it is less than 15% of Y, which may be due to the increase in the area occupied. A similar effect can be obtained by using Sc and one or more elements of the lanthanum series in place of Y as =Ln.

Effects of the Invention As described above, the method for producing an oxide superconductor according to the present invention (
The present invention provides a simplified method for producing YBa2cuaQ7.6.X series that does not require high-pressure oxygen heat treatment and has great industrial value. YBa2Cu407 does not require a heat treatment process of cooling down!・It provides a method for producing x-based thin films, and has great industrial value in that it can be applied to devices that are combined with other types of materials.

[Brief explanation of the drawing]

FIG. 1 is a schematic process diagram of the method for producing an oxide superconductor in an example of the present invention. FIGS. 2(a) and 2(b) are
Figure 3 is a process outline of the method for producing an oxide superconducting thin film in an example of the present invention. Figures 4 (a) and (b) are X-ray diffraction spectra of an oxide superconducting thin film in an example of the present invention. be. 1... Molding #, 2... Oxide superconductor 3...
・Substrate, 4... Alloy thin 111L5... Oxide superconducting thin 8 Name of agent Patent attorney Shigetaka Awano Haka 1 person molding dedication Figure 2 e YO day a OCu Vigilance 9381 Yū@P ☆Y day Q2CU40? , 5 + 1 (124 series) ↓ Normal oxygen heat treatment method law reading i oil brewing;

Claims (2)

[Claims] (1) The main components are Ln, barium (Ba) and copper (Cu)
1. A method for producing an oxide superconductor, which comprises heat-treating a molded body of an oxygen-free compound consisting of ) in an oxygen-containing atmosphere. Here, Ln is calcium (Ca), yttrium (Y
), scandium (Sc), and one or more elements of the lanthanum series. (2) A method for producing an oxide superconducting thin film, which comprises depositing an alloy thin film made of Ln, Ba, and Cu on a substrate, and heat-treating the film in an oxygen-containing atmosphere after the thin film is deposited. Here, Ln is one or more elements of Ca, Y, Sc, and lanthanum series.