JPH03183654A - Production of oxide superconductor - Google Patents

Abstract

PURPOSE:To simplify the device system and to improve the critical current density at the time of heat-treating a sample such as oxide superconducting powder or the film of the oxide superconducting sample formed on a substrate in an oxygen-contg. atmosphere by impressing a high gravity field resulting from the centrifugal force on the sample. CONSTITUTION:An oxide superconducting powder sample, the sample obtained by press-forming oxide superconducing powder or the film of the oxide superconducting sample formed on a substrate are heat-treated in the atmosphere of oxygen or air to produce a bulky or thin-film oxide superconductor. In this case, a sample 15 is placed in a ceramic housing 10 and heated by a heater 12 outside the housing 10, and the housing 10 is rotated on its rotation axis by a rotating device 18. Consequently, the sample is sintered by a simplified device system under the conditions where a high gravity field is impressed, and a high-density oxide superconductor excellent in the crystallinity and orientational property and with the critical current density improved is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing an oxide superconductor, and in particular to improvements in manufacturing an oxide superconductor under load application in order to improve its properties.

[Prior Art] When obtaining an oxide superconductor, there is generally a difference between obtaining it as a bulk or as a thin film formed on a substrate. When obtaining an oxide superconductor as a bulk,
A process is adopted in which superconductor powder is press-molded in advance and then sintered in an oxygen or air atmosphere, and then gill! In order to obtain such a material, a high frequency sputtering method, a vapor deposition method, an MBE method, etc. are employed.

However, the oxide superconductor produced in this way also
The critical temperature at which it becomes superconducting is close to the liquefaction temperature of liquid nitrogen, which is a practical cooling medium, so it has disadvantages such as not having a sufficient salinity margin and poor composition uniformity. Considering the field of application, etc., the critical current density is far from the practical level.

On the other hand, even under these circumstances, it has been known for a long time that sintering while applying a load can improve the final properties of the manufactured oxide superconductor, and therefore, based on this knowledge, A so-called hot press method has been proposed.

In other words, this is a method of sintering a sintered sample while intentionally applying weight to it using a mechanical loading device with a weight.

[Problems to be Solved by the Invention] It is true that the hot pressing method described above provides a higher critical current density than would otherwise be possible. However, it is still not at a satisfactory level, and above all, there are problems with the equipment system itself for implementing this method.

In other words, whether a weight is used or a press mechanism such as a hydraulic system is used in place of the weight, the equipment that applies weight to the sample is extremely large, and it is necessary to devise ways to apply the load evenly. It is. In balance, this hot pressing method may no longer be useful.

Additionally, if the orientation of the sintered oxide superconductor is improved and the crystals are well aligned, a high critical current density tends to be obtained, but as in this hot pressing method, simply adding weight There is no guarantee that they will improve.

The present invention has been made in view of the conventional circumstances, and it involves applying a load during the manufacturing process in order to improve the orientation and crystallinity of the manufactured oxide superconductor and thereby improve the critical current density. The purpose of the present invention is to provide a new manufacturing method that can meet such demands with a simple equipment system.

[Means for Solving the Problems] In order to achieve the above object, the present invention first takes a superconducting powder sample, a press-molded superconducting powder sample, or an oxide superconducting sample formed into a film on a substrate in an oxygen or atmospheric atmosphere. As an improvement in the production of bulk or thin film oxide superconductors by heat treatment, we propose a manufacturing method in which the heat treatment is performed while applying a high gravity field due to centrifugal force to the sample.

Here, when obtaining a bulk oxide superconductor sample from a superconducting powder sample or a sample obtained by press-molding superconducting powder, the above heat treatment is a so-called sintering process; The heat treatment for the oxide U conductor sample is a so-called post-annealing heat treatment performed to incorporate oxygen into the sample.

Furthermore, in the present invention, a thin film-like oxide superconductor is manufactured by sputtering an appropriate material according to the composition of the oxide superconductor to be obtained by high-frequency sputtering and depositing the oxide superconductor on a substrate. As an improvement in this case, we propose a method in which the target material is sputtered while applying a high gravity field due to centrifugal force to the substrate and the oxide superconductor deposited on it.

[Function] As described above, according to the present invention, in the case of heat treatment such as sintering and annealing, and in the case of high frequency sputtering, the high load to be applied to the sample being processed is due to centrifugal force. Obtained by a high gravity field based on

Therefore, it is not only possible to increase the density of the oxide superconductor manufactured according to the magnitude of the centrifugal force, but also to increase the density of the oxide superconductor produced in accordance with the magnitude of the centrifugal force. Since a stable high load can be applied to the substrate, the orientation and crystallinity can also be improved. Naturally, the advantage of high critical current density that the conventional hot pressing method had can be similarly obtained in the present invention, and when combined with the above-mentioned physical properties, the properties are even more excellent.

On the other hand, the device system itself for generating centrifugal force, that is, the device system itself for realizing the present invention, can be obtained extremely easily and compactly using known existing techniques, and furthermore, Even if the weight changes, the device that implements this method does not require changes to the size or weight of the device system itself.Centrifugal force is generated by the rotational angular velocity of the sample or substrate support part. This is because, if necessary, it can be obtained steplessly.

[Example] Figures 1A and 1B show an example of an apparatus configuration for obtaining a bulk oxide superconductor by sintering according to the present invention.

First, a space 1 having a width in the circumferential direction and the radial direction inside.
There is a housing 10 made of ceramics having a plurality of 1 in the circumferential direction. In FIG. 18, FIG. 1B is a partial sectional view taken along line B-B, and FIG. 1B shows one of the plurality of spaces 11 described above in an enlarged manner.

The housing 10 is used for loading and unloading a sample 15, which will be described later.
It is constructed by removably fitting two housing halves IL, IL2 in the axial direction, and each half 10-. ,1
0-2 are each shaped like a circular tray with an appropriate depth, and the above-mentioned space 11 is formed by fitting their opening edges together in the axial direction. Of course, an appropriate seal is applied between the mating edges using known technology,
Assemble with screws, etc.

As shown particularly in FIG. 1B, inside the space ll, both edges in the circumferential direction are sandwiched between a pair of plate-shaped ceramic heaters 12, 12, and the cross section is trapezoidal block-shaped and has high thermal conductivity. There is a high-temperature sample stage 13, and this sample stage 13 is also bored with an elliptical through hole that is elongated in the axial direction.
A sample 15 to be sintered is contained therein.

As sample 15, any oxide superconductor that has been proposed until recently may be used, but for example, YBa is a typical example.
Examples include those obtained by press-molding 2Cu3 powder in advance.

The sample stage 13 is equipped with a temperature sensor 14 in order to monitor a heating temperature suitable for the sample 15.

The remaining portion of the space 11 containing the above-mentioned components is filled with a heat insulating material 16 as required.

The center of the ceramic housing 10 is fixed to a rotating shaft 17, and this rotating shaft 17 is connected to a rotational drive device 18 such as a motor.
Rotationally driven by.

In addition, electric power is supplied to the ceramic heaters 12, 12 housed inside the ceramic housing 10 assembled by combining the two hands 1o-+ and to-2, using an external heater power source. A detected temperature signal from the temperature sensor 14 attached to the sample stage 13 is supplied from the temperature sensor 19 through the slip ring part 20 of a known structure and through the lead wires 21 and 21 passing inside the axis of the rotating shaft 17. is applied from a lead wire passing inside the rotating shaft 1 through a slip ring section 20 to a control device 22 that controls the system.

In this embodiment, since a so-called platinum sensor is used as the temperature sensor 14, a bias current is supplied to it from an externally provided constant current source 14° via the slip ring section 20.

In such a device system, under the command of the control device 22,
The output current value of the heater power source 19 is controlled so that the optimum temperature for sintering is applied to the sample 15, and the sample 13 is brought to the optimum temperature by the ceramic heater, which is a heater that converts electricity to heat. While maintaining the heated 'villainy',
In addition, if the rotation speed of the motor 18 is specified by the control device 22 so as to obtain a high gravity field of the required size,
The desired sintering process can be performed on the sample 13 while a high gravity field of an optimal size is applied to the sample 13 by centrifugal force.

In principle, the centrifugal force applies an extremely uniform load to the sample 13, so that the orientation and crystallinity of the sample 13 are extremely good. Naturally, the physical sintering density also increases, and the critical current density in an electrical sense also improves.

In the experiments conducted by the present inventor, the above sintering was carried out under the supply of oxygen through the axial through hole opened in the rotating shaft 17, but it may also be possible to perform the sintering in an atmospheric atmosphere.

Furthermore, in the present invention, since a necessary high load can be applied to the sample during manufacture, there is no need, in principle, to use a sample that has been press-formed in advance. It is true that if it is press-formed in advance, it will be easier to attach it to the sample stand, but if it is made of a stable material that can withstand heat treatment, such as zirconia, silicon nitride, or silicon carbide, then this will be suitable. By making a frame or box and placing the oxide superconducting powder in it, it becomes easy to install it inside the device, so press molding can be omitted, and even though The same effect as sintering after press forming can be obtained.

FIG. 2 shows another example of a device configuration for realizing the method of the present invention. Although the size itself may be slightly larger than that of the device shown in the first figure, the wiring structure for the rotating parts is much more compact. It's getting easier.

In this example as well, the same reference numerals are used for each component used in the first example.
Heater 1 as a heating source that heats at least the sample 15
2. . . . are exposed to the outside of the cella main ivy housing 10.

That is, in this case, the ceramic housing IO holding the sample 15 via the sample stage 13 without using a heat insulating material is installed in several internal spaces 11 in the circumferential direction (also in the axial direction for loading and unloading the sample). Butt half 10−+,
10-2), a fixed heater block 23 is provided so as to surround but not touch it, and the heater 12. ...is provided. However, of course, these installation positions are concentrated in positions close to the sample 15 within the housing 10, and therefore near the periphery of the housing.

Even with such a device system, when sintering the oxide superconducting sample 15 that has been press-formed in advance, the motor 18 is naturally controlled by the control device 22 (see FIG. 1), which is not shown in this figure. Rotate at high speed, and heater 1
2. By applying appropriate power to..., the sample 15 is
can be heated to an appropriate temperature.

Therefore, it is possible to perform sintering in a state where the necessary high gravity field is applied using a simple equipment system, resulting in high density, good crystallinity and orientation, and the critical current density has been improved to a practical level or a value sufficiently close to it. A physical superconductor can be obtained.

However, compared to the apparatus system shown in the first figure, in the case of the apparatus shown in the second figure, the information electrically extracted from inside the housing is basically obtained through a slip ring attached to the sample stage 3 and to the rotating shaft 17. The structure becomes simpler and the number of failure factors is reduced.

Depending on the material to be sintered, the heater 12,
Even if it is necessary to change the amount of heat required for..., with the configuration of the second illustrated apparatus, it is possible to cope with such a large change in the required amount of heat simply by replacing the heater block 23.

Above, examples have been described in which the method of the present invention is applied to the final production of a bulk oxide superconductor. The present invention can be similarly applied to cases in which heat treatment as so-called post-annealing is applied to an oxide superconductor formed in the form of a thin film on a substrate by various conventional methods.

That is, the formed oxide superconductor, together with the substrate, is fixed as a sample on the sample stage 13 of the apparatus shown in No. 1.2, and is heated to a high temperature by centrifugal force while introducing oxygen into the processing chamber (space 11). The desired annealing can be carried out while the pile is heated by heater 12 and 9 in a gravity field, and the final oxide superconductor produced is It can improve the physical and electrical properties of the body.

Furthermore, the present invention can be applied not only to heat treatment but also to the production of a thin film oxide superconductor on a suitable substrate by high frequency sputtering.

FIG. 3 shows an example of the configuration of a device system suitable for such a case.

Components corresponding to those in the previous embodiment will be described with the same reference numerals, and the housing 10 is similarly made of a suitable ceramic and consists of a pair of halves that are axially abutted against each other to close the interior. Body 10-+, 10-2
It consists of

Inside the internal space 11, substrate supports 24 containing heaters 12 are provided at several locations in the circumferential direction on the inner surface of the housing peripheral wall via heat insulating materials 16, and a substrate 25 is mounted on these.

The housing receives rotational drive from a rotational drive device 18 including a motor etc. at one end of its rotating shaft (center shaft) 17, but a magnetic fluid seal 26 is provided in the hollow portion at the other end. , a high frequency electrode 27 is fixedly fitted in the axial direction along the central axis.

The outer peripheral surface of the large end of the high-frequency electric field Fi 27 that fits into the housing also serves as a support for the material to be sputtered, that is, the target material 28 .

Further, the rotating shaft 17 is also fitted into a vacuum evacuation device 30 via a magnetic fluid seal 29, and the vacuum evacuation device 30 is inserted into the space within the housing 10 through the hollow center of the rotating shaft 17 using a known mechanism. The part 11 can be drawn to a desired degree of vacuum, and a gas suitable for the sputtering environment, such as Ar gas, can be fed into the space 11.

The power supply line to the heater 12 installed on the substrate support stand 25 and the information extraction line from the temperature sensor 13 are connected via a slip ring part 20 provided on the outer peripheral surface of the rotating shaft fitted into the vacuum device 30 side. , is connected to a control device (not shown) (see FIG. 1).

With such a device structure, when the housing 10 is rotated at a desired speed by the rotary drive device 18, that is, in a high gravity field environment due to centrifugal force, a predetermined distance between the high frequency electrode 17 and the ground can be maintained. A desired oxide superconductor thin film is formed on the substrate 25 by applying high-frequency power to generate plasma in the space 11 in the housing as a reaction chamber and sputtering the target material using excited ions. can be deposited.

The oxide superconductor thin film deposited and formed on the substrate 25 in this manner also has excellent superconducting properties such as critical current density because it was formed under a continuous and sufficiently high gravitational field. It becomes something.

In addition, when performing heat treatment according to the apparatus shown in Figure 1.2, in addition to the heater shown in the diagram, lasers and infrared rays can also be considered as heating sources, and even if these are directly irradiated onto the sample. good.

[Effects] As described above, according to the present invention, a high gravity field is generated using centrifugal force, and the oxide superconductor is sintered or annealed under this high gravity field, or by high frequency sputtering method. Since it is possible to deposit or form a film on a substrate, it is possible to reliably obtain an oxide superconductor with high physical density and good crystallinity and orientation, and its critical current density is at or very close to a practical level. The value can be increased.

Furthermore, since centrifugal force is used to generate a high gravitational field, the device system itself for realizing the method of the present invention can be easily constructed using existing machining and assembly techniques. Compared to the conventional hot press method, which applies a high load, the device configuration is much simpler and smaller.

In particular, even if the required load changes, if centrifugal force is used as in the present invention, all that is needed is to adjust the rotational angular velocity of the oxide superconducting sample or the substrate on which the oxide superconductor is deposited, and the There is no need to prepare weights of different sizes, and an extremely uniform load condition on the sample can be easily achieved without special or delicate adjustment means.

Claims (4)

[Claims] (1) By heat-treating an oxide superconducting powder sample, a press-molded sample of oxide superconducting powder, or an oxide superconducting sample formed into a film on a substrate in oxygen or air atmosphere, a bulk or thin oxide can be formed. 1. A method for producing an oxide superconductor, comprising: performing the heat treatment while applying a high gravity field due to centrifugal force to the sample. (2) The heat source for the heat treatment is provided inside the housing containing the sample and near the sample, and is an electricity-to-heat converter that rotates together with the sample as the housing rotates. The method for manufacturing an oxide superconductor according to claim 1, characterized in that the oxide superconductor is a type heater. (3) The heat source for the heat treatment is an electricity-to-calorific conversion type that is fixedly installed outside the rotating housing that houses the sample and surrounds the housing without touching it. The method for producing an oxide superconductor according to claim 1, wherein the method is a heater. (4) Sputtering an appropriate target material according to the composition of the oxide superconductor to be obtained by high-frequency sputtering,
A method for producing a thin film of an oxide superconductor on a substrate by depositing the oxide superconductor on the substrate, the method comprising: sputtering the target material on the substrate and depositing it on the substrate; A method for manufacturing an oxide superconductor, characterized in that the process is performed while applying a high gravity field due to centrifugal force to the oxide superconductor.