JPH07133181A - Method and device for hydrothermal synthesis - Google Patents

Abstract

PURPOSE:To provide a hydrothermal synthesis and a device therefor capable of improving a growing efficiency and making the characteristics of an objective substance uniform. CONSTITUTION:This hydrothermally synthetic device 1 is provided with a growing vessel 10 and a pressure vessel 20, and the growing vessel 10 is housed in the pressure vessel 20. A hydraulic medium 40 is filled the pressure vessel 20, and the growing vessel 10 is surrounded with the hydraulic medium 40. A baffle plate 30 is arranged in the growing vessel 10. A flange 16 is disposed at an outer peripheral wall part, and this flange part 16 is located at the almost same height with the baffle plate 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrothermal synthesis method and an apparatus used for the hydrothermal synthesis method. More specifically, the low temperature part and the high temperature part in a growing container are made uniform in temperature without a temperature gradient. The present invention relates to a hydrothermal synthesis method and a hydrothermal synthesis apparatus that can perform the same.

[0002]

2. Description of the Related Art Conventionally, hydrothermal synthesis has been known as one of methods for synthesizing new substances, removing impurities from incomplete crystals, modifying minerals, and growing single crystals of various substances. There is. For example, in growing a single crystal by this hydrothermal synthesis method, a seed crystal is hung in a low temperature part of a growth container, a high temperature part is filled with a raw material, and a dilute solution of a predetermined alkali or salt is injected, and the temperature is increased. A single crystal is grown by precipitating a predetermined substance (culture) on the seed crystal by utilizing the difference in solubility due to the difference.

At this time, the solute filled in the high temperature part and dissolved from the raw material is transported and deposited near the seed crystal in the low temperature part by thermal convection generated in the dilute solution due to the temperature difference between the high temperature part and the low temperature part. In order to improve the growth efficiency of the single crystal, it is important to keep the temperature difference between the high temperature portion and the low temperature portion constant and also keep the temperature distribution in each region uniform. Therefore, in general, a baffle plate is arranged in the growth container to divide the growth container into a high temperature part and a low temperature part.

[0004]

However, in such conventional hydrothermal synthesis, since the reaction is carried out under high temperature and high pressure, the growth container is usually housed in a pressure container,
An appropriate pressure medium (hereinafter referred to as "pressure medium") is filled between the pressure vessel and the growth vessel to protect the growth vessel, and in this case, the heat supplied for hydrothermal synthesis is It will be transmitted to the growth container via a pressure medium. Therefore, in hydrothermal synthesis, if an attempt is made to provide a temperature difference between the low temperature part and the high temperature part of the growth container, of the pressure medium surrounding the growth container,
A temperature difference is also given between the pressure medium surrounding the low temperature part and the pressure medium surrounding the high temperature part, but thermal convection occurs in the pressure medium due to this temperature difference.

Since the thermal convection of the pressure medium occurs from the high temperature part (lower part of the growth container) toward the low temperature part (upper part of the growth container), a temperature gradient is generated particularly in the low temperature part (part where the single crystal is grown). However, there is a problem in that the growth rate is different between seed crystals, the grown single crystals are not uniform in size, and the crystallinity is different between the single crystals. The present invention has been made in view of the above problems of the prior art, and an object thereof is to improve a growth efficiency and to homogenize the characteristics of a target substance, and a hydrothermal synthesis method. It is to provide a device for use.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventor has achieved the above problems by providing a member for suppressing heat convection of a pressure medium in a growth container and / or a pressure container. The inventors have found that they can be solved and completed the present invention. Therefore, the hydrothermal synthesis method of the present invention is a method for accommodating a growth vessel in a pressure vessel and performing hydrothermal synthesis,
The water filled in the gap between the pressure vessel and the growth vessel is provided with convection prevention means for preventing convection in the vertical direction and propagating the pressure in the vertical direction, and the vertical direction in the growth vessel. Further, the apparatus for hydrothermal synthesis of the present invention is a device used for hydrothermal synthesis provided with a growth vessel and a pressure vessel for accommodating the same, in the outer peripheral part of the growth vessel and / Alternatively, a flange portion is provided on the inner peripheral portion of the pressure vessel, and the flange portion is positioned at substantially the same height as the baffle plate disposed in the growing vessel.

[0007]

In the hydrothermal synthesis apparatus of the present invention, the outer peripheral portion of the growing container and / or the inner peripheral portion of the pressure container is provided with a flange portion, and the mounting position thereof is substantially the same as that of the baffle plate installed in the growing container. I adjusted it to be Therefore, under hydrothermal synthesis, the thermal convection generated in the pressure medium that is injected into the pressure vessel and surrounds the growth vessel is suppressed by the flange portion, and the temperature difference of the pressure medium between the upper side and the lower side of the flange portion is small. To be kept.

Since the flange portion is located at substantially the same height as the baffle plate installed in the growing container, an appropriate temperature difference is maintained above and below the baffle plate in the growing container. Therefore, the reaction efficiency of hydrothermal synthesis can be improved, and in growing a single crystal, the size of the obtained single crystal can be made uniform, and the characteristics such as its crystallinity can also be made uniform.

The hydrothermal synthesis apparatus of the present invention will be described in detail below. The apparatus for hydrothermal synthesis of the present invention comprises a growth container filled with a reaction material, and a pressure container for accommodating and protecting the growth container therein. The shape of the growth container itself is
The shape is not particularly limited, and may have various shapes such as a cube, a rectangular parallelepiped, a triangular prism, and a polygonal prism, but the uniformity of pressure inside the growth container, the uniformity of pressure applied from outside the growth container, and the uniform heat transfer into the container. In consideration of the property, the columnar shape is preferable.

The material of the growth container is not particularly limited, but the corrosion resistance, heat resistance, pressure resistance and the like depending on the kind of substance to be obtained by hydrothermal synthesis, the raw material used for growth, the solvent, etc. It is necessary to select the provided materials. For example,
For growing a ZnO single crystal, it is preferable to use Ag or Pt.

A baffle plate is installed inside the growing container to divide the growing container into a low temperature part and a high temperature part. This baffle plate is installed to suppress the thermal convection of the solvent injected into the growth container and maintain the temperature difference between the low temperature part and the high temperature part, and has a through hole. The porosity can be appropriately changed depending on the kind of the material to be grown, but in the case of growing a ZnO single crystal, it is 3 to 10.
% Is preferable. Further, the material of the baffle plate is not particularly limited and may be appropriately selected in consideration of heat resistance, corrosion resistance and the like depending on the kind of the substance to be obtained and the like as in the above-mentioned growth container.

Next, the pressure vessel may be any one capable of accommodating a growth vessel and canceling the pressure generated inside the growth vessel to protect the growth vessel, and an autoclave is representatively exemplified.

Next, the flange portion which characterizes the hydrothermal synthesizing apparatus of the present invention will be described. The flange portion is provided on the outer peripheral wall portion of the growth container or the inner peripheral wall portion of the pressure container, but may be provided on both the outer peripheral wall portion and the inner peripheral wall portion. The flange portion is arranged at substantially the same height as the baffle plate installed inside the growing container, that is, near the boundary between the low temperature part and the high temperature part in the growing container.

The flange portion suppresses heat convection generated under hydrothermal conditions in the pressure medium interposed between the outer peripheral wall portion of the growth container and the inner peripheral wall portion of the pressure container, and the upper and lower sides of the flange portion are suppressed. The temperature difference between the pressure medium and the side is maintained. And
Since the flange part is located at almost the same height as the baffle plate installed in the growing container, an appropriate temperature difference (temperature difference between the low temperature part and the high temperature part) is maintained above and below the baffle plate in the growing container. It will be.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the apparatus for hydrothermal synthesis of the present invention. In FIG. 1, the hydrothermal synthesis apparatus 1 includes a growing container 10 and a pressure container 20, and the growing container 10 is housed in the pressure container 20. Further, the pressure vessel 20 is filled with the pressure medium 40, and the growth vessel 10 has the pressure medium 4
Surrounded by 0s.

A baffle plate 30 is arranged inside the growing container 10, and the baffle plate 30 divides the inside of the growing container 10 into a low temperature part 12 and a high temperature part 14. The temperature difference between the high temperature section 14 and the low temperature section 12 can be provided by an electric furnace (not shown) having at least two heating zones surrounding the hydrothermal synthesis apparatus 1.

A flange portion 16 is provided on the outer peripheral wall portion of the growth container 10, and the flange portion 16 is located at substantially the same height as the baffle plate 30. Therefore, during hydrothermal synthesis, the high temperature part 1 of the pressure medium 40 is
Even if a thermal convection is generated due to a temperature difference between the pressure medium 42 surrounding (contacting) 2 and the pressure medium 44 surrounding the low temperature portion 14, this heat convection is suppressed by the flange 16 and the pressure medium Four
The temperatures of 2 and 44 are not the same. Therefore, during the hydrothermal synthesis, the temperature difference between the pressure media 42 and 44 is kept substantially constant, and as a result, the temperature difference between the low temperature part 12 and the high temperature part 14 in contact with the pressure media 42 and 44 is also kept constant. You will be drunk. In this way, the temperature difference between the low temperature portion 12 and the high temperature portion 14 is kept substantially constant during the hydrothermal synthesis and growth, so that the efficiency of the hydrothermal synthesis reaction can be improved.

Example 1 A ZnO single crystal was grown using the hydrothermal synthesis apparatus 1 described above. At this time, the seed crystal 5 suspended on the platinum frame 3 was placed in the low temperature portion 12, and the ZnO sintered body 7 was placed in the high temperature portion 14. In addition, in the growth container 10, 3 mol / l KOH and 1.5 mol / l
Alkaline solvent composed of LiOH of No. 2 was injected, the porosity of the baffle plate 30 was set to 5%, and distilled water was used as the pressure medium 40. The shape of the growth container 10 has an inner diameter of 30 mm.
× Almost cylindrical with a height of 300 mm, the internal volume is about 25
0 ml, and the shape of the pressure vessel 20 is an inner diameter of 32 mm x
It has a height of 330 mm and an internal volume of about 320 ml.
The gap between the flange portion 16 and the inner peripheral wall portion of the pressure vessel 20 is about 0.1 mm. Furthermore, the height of the frame 3 is 140 mm.

The temperature of the low temperature portion 12 was raised so that it was always lower than the temperature of the high temperature portion 14, and the temperature of the low temperature portion 12 was raised to 380 ° C and the temperature of the high temperature portion 14 was raised to 395 ° C. At this time, the growth container 10
The internal pressure is 850 kg / cm ² . In this state, steady operation was carried out for 14 days, after which the temperature was lowered to room temperature and the ZnO single crystal was taken out. Of the seed crystals 5, the seed crystals arranged at the uppermost part of the frame 3 and the seed crystals arranged at the lowermost part of the frame 3 were observed for the degree of growth, and the obtained results are shown in Table 1. Note that the temperature difference between the uppermost temperature and the lowermost portion is Δθ, and the temperature difference between the uppermost portion and the high temperature portion 14 is ΔT.

(Comparative Example 1) The same operation as in Example 1 was repeated, except that a growth container having no flange portion 16 was used, and the results obtained are shown in Table 1. (Example 2) The temperature of the low temperature part 12 was 380 ° C, the temperature of the high temperature part 14 was 400 ° C, and the pressure in the growth container 10 was 88.
The same operation as in Example 1 was repeated except that the amount was 0 kg / cm ^2, and the results obtained are shown in Table 1. (Comparative Example 2) The same operation as in Example 2 was repeated, except that a growing container in which the flange portion 16 was not provided was used.
The obtained results are shown in Table 1.

[0021]

[Table 1]

As is clear from Table 1, when the container for hydrothermal synthesis of the present invention was grown, a large temperature gradient was not generated in the low temperature part, and the obtained ZnO single crystals were well sized. You can see that

The present invention has been described above with reference to the embodiments.
The present invention is not limited to this, and various modifications can be made within the scope of the gist of the present invention. For example, the hydrothermal synthesis apparatus of the present invention can be used not only for growing a ZnO single crystal but also for various treatments utilizing a hydrothermal synthesis reaction. Further, the flange portion 16 may be provided on the inner peripheral wall portion of the pressure container 20, or may be provided on both the outer peripheral wall portion of the growth container 10 and the inner peripheral wall portion of the pressure container 20. Furthermore,
The gap between the flange portion 16 and the inner peripheral wall portion of the pressure vessel 20 and the like can be appropriately changed depending on the type of the target hydrothermal synthesis treatment and the dimensions of the growing vessel and the like.

[0024]

As described above, according to the present invention,
Since a member for suppressing thermal convection of the pressure medium is provided in the growth vessel and / or the pressure vessel, a hydrothermal synthesis method and a hydrothermal synthesis apparatus capable of improving reaction efficiency and homogenizing the characteristics of a target substance are provided. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the hydrothermal synthesis apparatus of the present invention.

[Explanation of symbols]

1 hydrothermal synthesis device, 3 frames, 5 seed crystals, 7 ZnO sintered body, 10 growth container, 12
Low temperature part, 14 High temperature part, 16 Flange part, 20
Pressure vessel, 30 baffle plate, 40 pressure medium

Claims (2)

[Claims] 1. A method for hydrothermally synthesizing a growth container in a pressure container, wherein water filled in a space between the pressure container and the growth container is prevented from convection in the vertical direction and the vertical direction. A hydrothermal synthesis method, characterized in that a convection preventing means for propagating the pressure is provided in the void portion to make a temperature difference in the vertical direction in the growth container. 2. An apparatus used for hydrothermal synthesis comprising a growing container and a pressure container accommodating the growing container, wherein a flange portion is provided on an outer peripheral portion of the growing container and / or an inner peripheral portion of the pressure container. An apparatus for hydrothermal synthesis characterized in that the flange portion is located at substantially the same height as the baffle plate arranged in the growing container.