JPH07133182A - Hydrothermal synthesis and growth vessel for hydrothermal synthesis - Google Patents

Abstract

PURPOSE:To obviate the formation of unnecessary deposits at the time of hydrothermal synthesis and to facilitate maintenance by disposing a solute capturing member for selectively capturing solute near the focusing point of solute transporting flow. CONSTITUTION:This growth vessel 10 for hydrothermal synthesis has internally a baffle plate 13 and is segmented to a low-temp. part 15 and a high-temp. part 17 by the baffle plate 13. ZnO sintered compacts 5 which are an example of the growth product are packed in the high-temp. part 17 and ZnO seed crystals 3 are hung down in the low-temp. part 15. The deposit capturing net 30 is disposed. The dissolved ZnO is transported from the high-temp. part 17 to the low-temp. part 15 through the through holes 13p of the baffle plate 13 by the thermal convection generated by a temp. difference between the low-temp. part 15 and the high-temp. part 17. The supersatd. components of the dissolved ZnO grow the seed crystals 3 by precipitating on the seed crystals 3 and pass the deposit capturing net 30. The remaining parts of the supersatd. components of the ZnO precipitated on the seed crystals 3 precipitate selectively on the capturing net 3 at the time of passing the capturing net 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 a container used in the hydrothermal synthesis method, and more specifically to a hydrothermal synthesis method in which unnecessary precipitates are less likely to deposit and adhere during hydrothermal synthesis. And a container for hydrothermal synthesis.

[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, an appropriate raw material is filled in a high temperature part, and a dilute solution of a predetermined alkali or salt is injected. The single crystal is grown by precipitating a predetermined substance on the seed crystal by utilizing the difference in solubility due to the temperature difference.

At this time, the solute dissolved from the raw material is transported to the low temperature part by thermal convection caused by the temperature difference between the high temperature part and the low temperature part, and thereafter, the solute in the supersaturated low temperature part of the solute, Precipitates on the seed crystal and grows the seed crystal.

[0004]

However, in such a conventional hydrothermal synthesis method, the solute that is in a supersaturated state at a low temperature part is not only on the seed crystal but also on the precious metal that suspends the seed crystal. Wires, the frame that fastens this noble metal wire, and the inner wall of the growth container were sometimes deposited as precipitates.

When it is deposited on the noble metal wire, there is a problem that the deposit contacts the seed crystal to be grown and inhibits its growth. When it is deposited on the frame or the inner wall of the growth container, it has a problem. In the next single crystal growth, the precipitate must be removed, and there is a problem that the time loss becomes large. Furthermore, if a precipitate is formed in the gap between the inner wall of the growth container and the frame, it is difficult to remove the frame from the growth container.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is not to generate unnecessary precipitates in hydrothermal synthesis, which is excellent in growth efficiency, and An object of the present invention is to provide a hydrothermal synthesis method and a hydrothermal synthesis growth container that are easy to maintain.

[0007]

As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above-mentioned problems can be solved by using a specific precipitate trapping member (solute trapping member). The present invention has been completed. Therefore, the hydrothermal synthesis method of the present invention is a solute that selectively collects solutes in the vicinity of the focusing point of the solute transport flow generated by thermal convection due to the temperature difference between the high temperature part and the low temperature part in the growth container. It is characterized in that a collecting means is provided to prevent crystals from precipitating on the inner wall of the growth container.

Further, the hydrothermal synthesis growth container of the present invention is a growth container used for hydrothermal synthesis, comprising a baffle plate and a precipitate collecting member, the interior of which is a low temperature part and a high temperature part by the baffle plate. It is characterized in that the precipitate collecting member is disposed in the low temperature portion.

[0009]

In the hydrothermal synthesis growth container of the present invention, the specific precipitate-collecting member is arranged near the focusing point of the solute transport flow (heat convection due to the temperature difference between the high temperature part and the low temperature part). I chose Therefore, unnecessary deposits that have conventionally been deposited on the inner wall of the growth container during hydrothermal synthesis are selectively collected by this deposit collection member.

That is, for example, in the growth of a single crystal by the hydrothermal synthesis method, the solute dissolved from the raw material filled in the high temperature part located in the lower part of the growth container has a temperature difference from that in the low temperature part located in the upper part. Due to the resulting heat convection, it rises through the baffle plate, and the supersaturated component of the solute is deposited on the seed crystal arranged in the low temperature part. After that, the residual solute that was not completely precipitated on the seed crystal further rises, contacts the inner wall of the top of the growth container, and inverts downward, but at this time, the residual solute is selected as the precipitate collecting member. To be collected.

Therefore, for example, in growing a single crystal by the hydrothermal synthesis method, it is possible to prevent deposits from adhering to a precious metal wire or the like on which the seed crystal is suspended and hindering the growth of the seed crystal. It is also unnecessary to remove the deposited deposits.

The hydrothermal synthesis growth container of the present invention will be described in detail below. The growth container of the present invention contains a baffle plate and a precipitate collecting member. Here, the shape of the growing container is not particularly limited, and may be a cube, a rectangular parallelepiped, or a cube.
Although various shapes such as a prism and a polygonal column can be adopted, a columnar shape is preferable in view of the uniformity of pressure in the growth container and the uniformity of heat transfer into the growth container.

The material of the growth container is not particularly limited, but a material having corrosion resistance, heat resistance and pressure resistance is selected according to the type of substance to be obtained by hydrothermal synthesis, the solvent and the like. There is a need. For example, for growing a ZnO single crystal, it is preferable to use Ag or Pt.

As described above, the baffle plate is installed inside the growing container, and the inside of the growing container is divided into the low temperature part and the high temperature part by the baffle plate. This baffle plate is installed in order 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 according to the kind of the substance to be subjected to the hydrothermal synthesis treatment, but when growing a ZnO single crystal, it is preferably about 3 to 10%. The material of the baffle plate is not particularly limited, and may be appropriately selected in consideration of heat resistance, corrosion resistance, etc., depending on the type of substance to be obtained, etc., as in the above-mentioned growth container.

Next, the precipitate collecting member is arranged at a low temperature portion inside the growth container, and preferably, the position where the solute transport flow (heat convection) exceeds the suspension position of the seed crystal (seed crystal). It is located on the upper side) and near the focusing point of this solute transport flow. Typically, the position where this collecting member is arranged is near the top of the growing container. Typically, when the size of the growing container is 30 mm inside diameter x 350 mm in height, 5 to 25 mm from the top of the growing container. It is better to place it at a certain position. Further, by providing a spherical projection on the top of the growth container, the path of the solute transport flow can be controlled so as to selectively pass through the precipitate collecting member arranged near the top, so that the top of the growth container is It is preferably formed in this way.

The shape of the deposit collecting member is not particularly limited, but it is preferable that a plurality of linear members are combined, and a typical example is a blind shape or a net shape. Further, the material of the linear member is not particularly limited and can be appropriately changed according to the intended hydrothermal synthesis treatment, the solvent used, etc., but a noble metal such as Ag or Pt is preferable, and H ₂ O ₂ When using such an oxygen generating agent, Pt is preferable.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings with reference to the accompanying drawings. FIG. 1 shows an embodiment of the hydrothermal synthesis growth container of the present invention. In the figure, the growth container 1 is provided with a baffle plate 13 inside and is divided into a low temperature part 15 and a high temperature part 17 by this baffle plate 13. The high temperature part 17 is filled with a ZnO sintered body 5 which is an example of a grown product, the low temperature part 15 is hung with the ZnO seed crystal 3, and a precipitate collecting net 30 is provided. Has been.

The seed crystal 3 is fastened to and suspended from a noble metal frame 20 by a noble metal wire 7. And
The top portion 22 of the frame 20 is formed in an annular shape, and the precious metal deposit collecting net 30 is fastened to the annular top portion 22 via the noble metal wire 7. In this embodiment, the annular top 2 to which the precipitate collecting net 30 is fastened
Although 2 and the frame 20 are integrally formed, they may be formed separately and the annular member 22 to which the precipitate collecting net 30 is fastened may be placed on the frame 20. Further, through holes 13p and 13h are formed in the baffle plate 13, and thermal convection occurs through these through holes 13p and 13h.

FIG. 2 is a cross-sectional explanatory view showing how molten ZnO is transported during hydrothermal synthesis using the growth container 1. As shown by the arrow F in the figure, the dissolved Zn
O is transported from the high temperature portion 17 to the low temperature portion 15 through the through hole 13p of the baffle plate 13 by thermal convection caused by the temperature difference between the low temperature portion 15 and the high temperature portion 17. Then, the supersaturated portion of the dissolved ZnO is deposited on the seed crystal 3 to grow the seed crystal 3 and passes through the deposit collection net 30.

When passing through the deposit collecting net 30,
The ZnO supersaturated residue deposited on the seed crystal 3 is selectively deposited on the collection net 30. Therefore, seed crystal 3
Other than the above, for example, between the noble metal wire 7 of the frame 20 and between the frame 20 and the inner wall of the growth container 10, extra Zn is added.
O (precipitate) does not adhere, and it is possible to prevent growth of the seed crystal 3 or to wash the growth container 10 for each lot.

Then, the dissolved ZnO is collected net 30.
After passing through, it reaches the top 10t of the growth container 10, is inverted and descends, and returns to the high temperature part 17 through the through hole 13h of the baffle plate 13. At this time, due to the curved surface formed by the top portion 13t, the ZnO transport flow F is smoothly inverted, and ZnO can be better prevented from adhering to the vicinity of the top portion.

(Example 1) Using the above-mentioned growth container 10, Z
An nO single crystal was grown. At this time, the shape of the growing container 10 has an inner diameter of 30 mm and a height of 350 mm and an inner volume of about 250 mm.
ml. A ZnO sintered body was used as a growth raw material for 200 times.
g as a seed crystal 3 and 1 × 1 × 10 mm ZnO
Ten columnar crystals were suspended. The deposit collection net 30 is A
15 g from the top 10t of the growth container 10
It was arranged at a position of mm. The open rate of the baffle plate 13 is 5%.

In the growth vessel 10, 3 mol / l KOH
An alkaline solvent composed of 1.5 mol / l of LiOH was injected at a rate of about 80% of the free internal volume of the growth container 10. The growing container 10 was housed in an autoclave (not shown), and distilled water as a pressure medium was injected into the autoclave at a rate of about 70% of the free internal volume of the autoclave.

Then, the temperature of the low temperature section 15 is raised so that the temperature of the low temperature section 15 is always lower than that of the high temperature section 17, and the temperature of the low temperature section 15 is adjusted to 38.
The high temperature part 17 at 0 ° C. was heated to 395 ° C. and maintained as it was for 14 days. Then, the temperature was lowered to room temperature and the ZnO single crystal was taken out. Does not precipitate on seed crystal 3,
As a result of measuring the weight of ZnO attached to the growth container 10 and the frame, the attached amount was 0.8 g.

(Comparative Example 1) The same operation as in Example 1 was repeated except that the precipitate collecting net 30 was not used and the growth container 10 had a flat top. The amount of ZnO attached was 9.0 g. From this, it can be seen that the use of the hydrothermal growth container of the present invention can significantly reduce the amount of extra ZnO deposited.

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 growth container of the present invention can be used for various hydrothermal growths other than ZnO single crystal growth. Further, the planar shape of the top portion 22 for fastening the deposit collecting net 30 may be not only circular but also polygonal such as quadrangular and hexagonal. Furthermore, the top 10t of the growth container 10 does not necessarily have to be spherical, and may be flat.

[0027]

As described above, according to the present invention,
Since a specific precipitate collecting member is used, a hydrothermal synthesis method and a growth container for hydrothermal synthesis that are excellent in growth efficiency without generating unnecessary precipitates during hydrothermal synthesis and are easy to maintain are provided. be able to.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a growth container of the present invention.

FIG. 2 is a cross-sectional explanatory diagram showing a ZnO transport flow during hydrothermal synthesis.

[Explanation of symbols]

10 growth container, 10 t top part, 13 baffle plate, 15 low temperature part, 17 high temperature part, 20 frame, 30 deposit collection net

Claims (7)

[Claims] 1. A solute trapping means for selectively trapping a solute is provided in the vicinity of a focus point of a solute transport flow generated by thermal convection caused by a temperature difference between a high temperature part and a low temperature part in a growth container. A method for hydrothermal synthesis characterized by preventing crystals from precipitating on the inner wall of a growth container. 2. A growth container used for hydrothermal synthesis, comprising a baffle plate and a precipitate collecting member, the interior of which is divided into a low temperature part and a high temperature part by the baffle plate, and in this low temperature part, the above A growth container for hydrothermal synthesis, comprising a deposit collection member. 3. The growth container according to claim 2, wherein the precipitate collecting member is arranged near the focusing point on the upper side of the seed crystal of the solute transport flow. 4. The growth container according to claim 2, wherein the precipitate collecting member is arranged near the top of the low temperature portion. 5. The growth container according to any one of claims 2 to 4, wherein the deposit collecting member is made of a noble metal wire. 6. The growth container according to claim 2, wherein the deposit collecting member is composed of a net made of a noble metal. 7. The growing container according to any one of claims 2 to 6, characterized in that the top part thereof is provided in a spherical shape.