JPH04110034A - Method and device for heat treatment - Google Patents

Abstract

PURPOSE:To highly control the excess and deficiency of oxygen in an oxide material by carrying out the process from heating to quenching by a horizontal furnace continuously in a controlled-oxygen partial pressure atmosphere. CONSTITUTION:A quenching part 2 is integrally hung down from one end of a horizontal furnace 1 for heating a sample. The oxygen partial pressure in the furnace 1 and quenching part 2 is controlled by an oxygen partial pressure control mechanism consisting of the oxygen inlet line 11 and nitrogen inlet line 12 on the inlet side and an evacuating line 13 (diffusion pump) on the outlet side. The heating by the furnace 1 and quenching are continuously carried out in the controlled-oxygen partial pressure atmosphere. Consequently, the oxide magnetic material and oxide superconducting material excellent in characteristics are stably produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat treatment method and a heat treatment apparatus for producing various oxide materials in a highly controlled oxygen partial pressure atmosphere.

[Summary of the invention]

The present invention achieves oxygen stoichiometry (
The present invention provides a heat treatment system that can highly control the amount of oxygen (excess or deficiency).

[Conventional technology]

Generally, in oxide magnetic materials and oxide superconducting materials, the amount of oxygen contained in the material greatly influences the physical properties of the material. For example, perovskite magnetic material (L
a +-, Ca , )zMn O3+, and 5rFeOz
-7 etc., the magnetic properties and electrical properties change significantly depending on the magnitude of the value of r. Furthermore, even in YBa2Cu+O□-4, which has attracted attention as an oxide superconductor in recent years, it exhibits superconductivity when the value of r is small, but as the value of r approaches 1, it becomes a semiconductor and no longer exhibits superconductivity. It is being

Therefore, in order to study the physical properties of the materials mentioned above,
It is required to precisely control the excess or deficiency of oxygen in the above material, so-called oxygen stoichiometry. Therefore, it is necessary to perform heat treatment in an atmosphere having a constant oxygen partial pressure at high temperature to bring the material into a predetermined oxygen-containing state, and then perform rapid quenching in order to freeze that state.

By the way, when heat-treating the above-mentioned material, it is preferable to use a horizontal furnace which is less affected by convection in terms of temperature controllability. When rapid quenching is performed after heat treatment in such a horizontal furnace, the heated material is usually removed from the furnace by opening the lid in an atmosphere with a predetermined temperature and oxygen partial pressure, and then placed in a cooling chamber. The method used is to drop it into a container.

However, in the rapid quenching method described above, since the material is heated in a predetermined atmosphere or exposed to the atmosphere for a short time, oxygen enters and exits.

For this reason, it is difficult to maintain a predetermined oxygen-containing state during heating.

On the other hand, there is a method of rapidly quenching the material by heat treating it in a vertical furnace. In this case, by rotating the vertical furnace, the heated material can be dropped into a cooling container, making it possible to rapidly quench the material without exposing it to the atmosphere. However, because
In a vertical furnace, the gas flow is introduced from the bottom, so the temperature inside the furnace cannot be controlled easily.

[Invention or problem to be solved]

As described above, the conventional processing methods are unsatisfactory in terms of maintenance of oxygen-containing state during heating, controllability of temperature, and control of oxygen partial pressure.

Therefore, the present invention has been proposed in view of the conventional situation, and is a heat treatment method that can highly control the oxygen stoichiometry of an oxide material and also allows easy temperature control and oxygen partial pressure control. The present invention also aims to provide a heat treatment apparatus.

[Failure to solve the problem]

In order to achieve the above object, the heat treatment method of the present invention includes:
The heat treatment apparatus of the present invention is characterized in that the steps from heating in a horizontal furnace to rapid quenching are performed continuously in an atmosphere of controlled oxygen partial pressure. A rapid quench section is provided integrally so as to hang down from one end of the horizontal furnace, and an oxygen partial pressure control means is provided for controlling the oxygen partial pressure of the horizontal furnace and the rapid quench section. It is something to do.

[Effect]

In the heat treatment method of the present invention, the steps from heating in a horizontal furnace to rapid quenching are performed continuously in an atmosphere of controlled oxygen partial pressure, so the sample is not exposed to the atmosphere and oxygen enters and exits. Never. Furthermore, since heating is performed in a horizontal furnace, temperature control is also easy.

Further, in the heat treatment apparatus of the present invention, the horizontal furnace and the rapid quench section are provided integrally, and the steps from heating to rapid quenching can be smoothly carried out simply by moving the sample.

〔Example〕

Hereinafter, specific embodiments to which the present invention is applied will be described with reference to the drawings.

FIG. 1 schematically shows the general configuration of the heat treatment apparatus used in this example. This heat treatment apparatus consists of a horizontally long horizontal furnace (1) arranged horizontally; It consists of a rapid quench part (2) integrally formed so as to hang down from one end.

The horizontal furnace (1) is provided with a coil (3) for high-frequency induction heating, for example, and the sample is heated and fired here. In addition, a sample holder (4) for placing a sample is inserted into this horizontal furnace (1), and this sample holder (4) can be moved without disturbing the atmosphere inside the furnace. The means 9 can be easily moved from the center of the horizontal furnace (1) to the rapid quench section (2) by, for example, a magnetic transfer mechanism. In the center of the sample holder (4) and the heating coil (3), temperature detection mechanisms (5), (6) consisting of, for example, thermocouples are provided. Based on the information from 6), horizontal furnace (1
) is connected to a temperature controller (7) which controls the temperature within the temperature range.

On the other hand, a cooling jacket (8) is provided around the bottom of the rapid quench section (2), and is sufficiently cooled by a cryogen (9). Then, rapid quenching is performed by dropping the sample into this rapid quenching section (2).

The horizontal furnace (1) and the rapid quench section (2) are integrally formed as described above, and the horizontal furnace (
The chamber 1) and the chamber of the rapid quench section (2) are not separated by a partition or the like and are completely connected.

However, since there is a large temperature difference between the horizontal furnace (1) and the rapid quench section (2), especially the rapid quench section (
In order to prevent the heat of the horizontal furnace (1) from being transmitted to the horizontal furnace (1), a cooling means is provided, for example, at the flange (10) connecting these.

The above-mentioned horizontal furnace (+) and rapid quench section (2) are provided with an oxygen partial pressure control mechanism for controlling the oxygen partial pressure in the atmosphere. This oxygen partial pressure control mechanism will be explained below.

The oxygen partial pressure control mechanism is roughly divided into an oxygen introduction system (11) and a nitrogen introduction system (12) on the inlet side, and a vacuum exhaust system (13) on the outlet side.

Then, from the inlet side, the oxygen-nitrogen mixed gas supplied from the oxygen introduction system (11) and the oxygen introduction system (12) is introduced into the furnace. That is, oxygen is filtered through the filter (1
4), solenoid valve (15), pneumatic valve (16), mass flow controller (17), and nitrogen is also supplied to the filter (18), solenoid valve (19), pneumatic valve (20), mass flow controller (21). ), respectively.
A pneumatic valve (22
) into the furnace.

Here, the mass flow controller (17) of the oxygen introduction system (+1) is designed to be switched to a three-stage type, with pneumatic valves (+6a), (16b), (+6
c) are connected in parallel via. For example, the first mass flow controller (17a) has a maximum of 200
CC/min, the second mass flow controller (+7b) controls the flow rate up to 20cc/min, and the third mass flow controller (17c) controls the flow rate up to 20C/min. It is possible to control the oxygen partial pressure to about 0.1%.

Further, the nitrogen introduction system (12) is connected to the oxygen introduction system (11) via an oxygen pump (23) and a check valve (24). This oxygen pump (23) controls the oxygen partial pressure in a low concentration region, and is a device that absorbs or discharges oxygen from the system by applying an external voltage to the normal zirconia sensor. be.

Therefore, it is effective for removing oxygen in the system or introducing a trace amount of oxygen.

On the other hand, the evacuation system (13) on the exit side is equipped with, for example, a diffusion pump (24), which also allows vacuum heat treatment. Furthermore, a Pirani gauge (thermal conduction vacuum gauge) (25) and an ion gauge (26) are installed between the diffusion pump (24) and the horizontal furnace (1).

Furthermore, for the purpose of confirming the equilibrium of the sample in the horizontal furnace (1) and understanding the residual oxygen partial pressure value of the furnace,
Zirconia oxygen partial pressure sensors (29) and (30) are placed at two locations on the inlet and outlet sides via air valves (27) or stop valves (28). These oxygen partial pressure sensors (29) and (30) measure the oxygen partial pressure at the inlet or outlet side to 0. It is possible to detect up to about 1 ppm, and it is also possible to monitor, for example, changes in the temperature of the atmosphere, the movement of oxygen from the sample due to the movement of the sample, etc.

The oxygen partial pressure control mechanism is provided with appropriate stop valves (SV) at various locations to maintain a high degree of vacuum within the system.

In the above-mentioned heat treatment apparatus, in order to heat and rapidly cool a sample, the sample holder (4) is first placed in the center of the horizontal furnace (1), and the sample is heat-treated in an atmosphere controlled by an oxygen partial pressure control mechanism. . After the prescribed heat treatment is completed, the sample holder (4) is placed in the rapid quench section (
2) and rotate this sample holder (4) to drop the sample into the rapid quench section (2). As a result, the steps from heat treatment in the horizontal furnace (1) to rapid quenching can be performed continuously in a controlled oxygen partial pressure atmosphere without being exposed to the atmosphere at all.

Incidentally, the above heat treatment apparatus requires a mechanism that allows the sample holder (4) to be moved without disturbing the atmosphere within the horizontal furnace (1) and rotated above the rapid quench section (2). . Therefore, the structure of a magnetic transfer mechanism (magnetic transfer funnel), which is an example of such a transfer mechanism, will be explained.

This magnetic transfer mechanism, as shown in FIGS. 2 and 3,
An inner magnet ring (33) supports a sample holder (4) on which a sample (31) is placed and holds an alumina outer cylinder (32) extending from the sample holder (4).
) and an outer magnet ring (34) for operating this inner magnet ring (33) by magnetic force, and these inner magnet ring (33) and outer magnet ring (34) are The containers are arranged concentrically with container partition walls (35) in between to maintain the atmosphere.

The inner magnet J nong (33) has a small diameter part (33a) having an inner diameter slightly larger than the outer diameter of the alumina outer cylinder (32), and an outer diameter part (33a) having an inner diameter slightly larger than the inner diameter of the container partition wall (35). The large diameter part (33a
), and an alumina outer cylinder (32
) or screws (36).

Furthermore, elongated magnets (37) are arranged at regular intervals on the surface of the large diameter portion (33a).

The outer magnet ring (34) has a width approximately equal to the large diameter portion (33a) of the inner magnet ring (33), and the inner magnet ring (33)
Each magnet (3
7), there are also multiple elongated magnets (
38) are equally spaced at predetermined intervals. This outer magnet ring (34) has an operating lever (
39) are provided.

Furthermore, a slide portion (
41) is rotatably attached, and this slide part (41
) is inserted through a pair of slide rails (42) arranged parallel to each other along the container partition wall (35), so that it can freely slide.

In addition, the container partition wall (35) is fixed to the side surface of the horizontal furnace (1) by the base end or the stainless steel flange (43), and the tip end is closed by the tip plate (44).
It is sealed so that the atmosphere inside the horizontal furnace (1) can be maintained reliably. In addition, a thermocouple (45) protected by a Teflon tube or the like is inserted from the tip plate (44).
This thermocouple (45) extends through the alumina outer cylinder (32) to the sample holder (4) while being protected by an alumina protection tube (46).

In the magnetic transfer mechanism having the above configuration, the slide portion (41
) and the outer magnet ring (34) along the slide rail (42) in the direction of arrow X, the inner magnet ring (33) also moves to the magnet (37).
and the magnet (38). Therefore, it becomes possible to transfer the sample holder (4) from outside the model reactor ().

On the other hand, when performing a rapid quench, the sample holder (4) is moved above the rapid quench section (2) by the above operation, and the operating lever (39) attached to the outer magnet ring (34) is moved to the arrow Y. Rotate in the direction. Then, as expected, magnet (37) and magnet (
Due to the magnetic coupling with the outer magnet ring (38), the inner magnet ring (33) rotates as the outer magnet ring (34) rotates.
) rotates, and of course the alumina outer cylinder (32) and sample holder (4) also rotate, and the sample (31) is dropped into the rapid quench section (2).

Next, as an application example of the present invention, an oxide superconductor was actually created using the above-mentioned apparatus, and its characteristics were evaluated.

Composition of Nd2O5, Cen2゜ and CuO with purity 99.99% (4N) Nd +, ssCeo, +aCu
04, respectively 61.912g and 5.5
08g.

15,909 g was accurately weighed and placed in a 500i polyethylene bottle, and whole milled for 20 hours with 100 Luconia holes and 150 ml of ethanol.

Thereafter, the sample solution was dried with hot air to obtain a powder in a mixed state.

Next, this powder was molded into a lot with a diameter of 12 mm (pressure: 1 t).
/cm), then calcined (T) at 900°C for 15 hours.
□It was performed in an atmosphere. After crushing this and molding it again,
Calcination (n) at 1050°C for 55 hours, 0. The test was carried out in an atmosphere, and then ground again to prepare a sample for firing. And the oxygen partial pressure control system we created this time (heat treatment equipment mentioned above)
I tried the following experiment using .

As shown in Figure 4, -dan sample (molded into 14X2X2)
was heated to 1150°C at a heating rate of 5°C/min, held at this temperature for 5 hours to form a single phase and sinter, and then
C/min, lower the temperature to a predetermined quench temperature T0, and use a mass flow controller (MFC) to maintain the above quench temperature T0 for at least 5 hours until the oxygen partial pressure in the system reaches a predetermined value. was held at At this time, the oxygen partial pressure was always monitored based on the outlet side.

Oxygen partial pressure on the outlet side or target quench oxygen partial pressure PO2
When this happens, turn off the furnace controller power, and at the same time, immediately move the magnetic transfer rod shown in Figures 2 and 3 to the rapid quench section (moving time is about 2 seconds), and rotate the alumina outside [(32). By doing so, the sample holder (4) was rotated and the sample was dropped.

At this time, a non-reactive platinum plate was used as a saucer in the rapid quench section (2). Further, the outside of the rapid quench section (2) was sufficiently cooled in advance with a cryogen of acetone and dry ice for at least one hour. If liquid nitrogen is used as a cryogen, oxygen, etc. in the atmosphere will liquefy and the flow rate may change or become dangerous, so it is best to avoid it.

As for the material of the cooling part, it is preferable to use quartz glass or, if other than quartz glass, to use copper, which has good thermal conductivity, in order to make it easier to see the inside state.

- As an example, the oxygen partial pressure at the time of quenching is 100 p.
FIG. 5 shows the temperature dependence of the electrical resistance of the sample in the low temperature range when the quench temperature is changed as pm (1, OX l O-' atmospheric pressure). Quench temperature or low temperature 7
As the temperature increases from 00°C to 1000°C, the electrical conductivity changes from semiconducting to metallic due to the effect of oxygen vacancies in the material (carrier doping effect).
The increase in electrical resistance is due to the slightly generated impurity phase (N d 2
It is also considered to be Ce 207 phase). Furthermore, a rapid decrease in electrical resistance is observed near 20, which is a superconducting transition.

Further, FIG. 6 shows the temperature dependence of the electrical resistance of the sample in the low temperature range when the quench temperature was set at 900° C. and the oxygen partial pressure during quenching was changed.

In this case as well, it can be seen that the electrical conductivity characteristics change depending on the oxygen partial pressure during quenching.

As described above, it can be seen that manufacturing oxide superconductors requires precise control of temperature and oxygen partial pressure, and also requires a system that can perform rapid quenching while maintaining a constant atmosphere.

Conversely, the heat treatment equipment used this time allows for precise control of temperature and oxygen partial pressure, which means that rapid quenching can be performed while keeping the atmosphere constant.

〔Effect of the invention〕

As is clear from the above explanation, in the heat treatment method of the present invention, the steps from heating to rapid quenching are performed continuously without being exposed to the atmosphere, so that the inadvertent entry and exit of oxygen can be suppressed. Rapid quenching is possible, and the amount of oxygen in the heated state can be maintained well.

Therefore, it is possible to stably produce oxide magnetic materials and oxide superconducting materials with excellent properties.

In addition, the heat treatment apparatus of the present invention has a structure in which the horizontal furnace and the rapid quench section are integrated, so it is possible to smoothly perform rapid quenching without oxygen entering and exiting, and the horizontal furnace can be used. This makes temperature control easy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of the configuration of a heat treatment apparatus to which the present invention is applied, FIG. 2 is a sectional view showing an example of the structure of a magnetic transfer mechanism, and FIG. 3 is a diagram taken along line A-A in FIG. FIG. Figure 4 is a diagram showing the temperature and oxygen partial pressure profiles in the actual heat treatment process, Figure 5 is a characteristic diagram showing the difference in temperature characteristics of electrical resistance of samples prepared by changing the heating temperature, and Figure 6 is a characteristic diagram showing the difference in temperature characteristics of electrical resistance of samples prepared with different oxygen partial pressures. l...Horizontal furnace 2...Rapid quench section 4...Sample holder 11...Oxygen introduction system patent applicant Sony Corporation representative Patent attorney Akira Kowa (2 others) Figure 1 degree [K ] Figure

Claims (2)

[Claims] (1) A heat treatment method characterized in that the steps from heating in a horizontal furnace to rapid quenching are performed continuously in an atmosphere of controlled oxygen partial pressure. (2) Equipped with a horizontal furnace that heats the sample and a rapid quench section that is integrally provided so as to hang down from one end of the horizontal furnace, and an oxygen partial pressure that controls the oxygen partial pressure of the horizontal furnace and the quick quench section. A heat treatment apparatus provided with a control means.