JP2006036614A - Method and apparatus for producing crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently produce a triglycine sulfate (TGS) crystal which is largely grown in a-axis and c-axis directions while suppressing the growth in b-axis direction. <P>SOLUTION: After growing a TGS-based seed crystal C1 to some degree in a first raw material solution 1s, the growing seed crystal C1 is moved into a second raw material solution 2s containing a dopant in a different concentration and grown in the second raw material solution 2s, without continuously growing the seed crystal in the same raw material solution. The seed crystal is largely grown in a specified direction by repeating the process mentioned above. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a crystal manufacturing method and a crystal manufacturing apparatus, and more particularly to a crystal manufacturing method and a crystal manufacturing apparatus that can manufacture a crystal that has grown greatly in a specific direction.

A crystal manufacturing method is known in which crystals are grown by gradually lowering the temperature of the raw material solution (see, for example, Non-Patent Document 1).
On the other hand, studies have been made on the crystal habit of TGS (Triglycine Sulfate) crystals (for example, see Non-Patent Documents 2, 3, and 4).

Shinichiro Takasu “Physical Engineering Experiment 12 Basic Crystal Growth Technology”, University of Tokyo Press, May 30, 1980, p. 53-56 `` Ferroelectric Domain Structure and Internal Bias Field in DL-α-Alanine-Doped Triglycine Sulfate '' Japanese Journal of Appllied Physics, Vol.30, No.12A, December 1991, pp.3445-3449 `` Growth and morphology of triglycine sulfate (TGC) crystals '' Journal of Materials Science Letters, 8 (1989), pp.1348-1349 B. Brezina, M. Havrankova `` L-Alanine Distribution in the Growth Pyramids of TGS Crystal and its Influence on the Growth, Switching and Domain Structure '' Crysral Res. Technol

Since the polarization direction of the TGS-based crystal is the b-axis direction, the TGS-based crystal has a flat plate shape in which the a-axis direction and the c-axis direction are plane directions and the b-axis direction is a thickness direction (that is, a flat plate shape having a wide b-plane). And used as a pyroelectric element. In the TGS crystal, an equivalent crystal can be obtained regardless of whether it is large in the a-axis and c-axis directions or large in the b-axis direction.
However, in the case of a LATGS or DLATGS crystal in which TGS is doped with L-α-alanine as an impurity, the a-axis direction and the c-axis direction are set as the plane direction and the b-axis depending on in which region the crystal grows with respect to the seed crystal. Even in the case of a plate-shaped crystal whose direction is the thickness direction, the characteristics are different. This is described in Non-Patent Document 2 (however, the crystal called DLATGS in Non-Patent Document 2 is a TGS-based crystal having D-α-alanine and L-α-alanine as dopants, Unlike DLATGS, where hydrogen is replaced with deuterium to increase the temperature).
The purpose of doping L-α-alanine is to obtain a stable polarization state, which depends on the internal bias generated inside the crystal by L-α-alanine. This is described in Non-Patent Document 2 and Non-Patent Document 4. The growth region where the internal bias becomes large is a limited region, and a particularly large internal bias can be obtained in a region grown on a plane perpendicular to the (0, -1, 0) axis.
That is, in order to further increase the internal bias of the crystal to be grown (to efficiently derive the effect of introducing a dopant), a plane perpendicular to the (0, -1, 0) axis is used as a seed crystal, and a crystal is formed in a region above it. It is important to grow. Therefore, in order to obtain such a crystal efficiently, it is required to increase the area of the plane perpendicular to the (0, -1, 0) axis.
Accordingly, an object of the present invention is to provide a crystal manufacturing method and a crystal manufacturing apparatus capable of manufacturing a crystal that has grown greatly in a specific direction.

According to a first aspect, the present invention provides a seed crystal in a first raw material solution for crystal growth, and then transfers the growing seed crystal to a second raw material solution having a composition different from that of the first raw material solution for further crystal growth. A crystal production method is provided.
As a result of intensive research by the present inventor, when a seed crystal is put in a raw material solution, the growth rate in a specific crystal axis direction is initially high and the growth rate in other crystal axis directions is low, but after the crystal habit appears. It was found that the growth rate in each crystal axis direction maintained the crystal habit. Furthermore, when the growing seed crystal is transferred into a raw material solution having a composition different from that of the first raw material solution, the growth rate in a specific crystal axis direction is increased again, the growth rate in the other crystal axis direction is decreased, and the crystal habit is eventually reduced. After appearing, it was found that the growth rate in each crystal axis direction maintained the crystal habit.
Therefore, in the crystal manufacturing method according to the first aspect, when seed crystals are grown to some extent in the first raw material solution instead of continuing to grow seed crystals in the same raw material solution, the second raw material solution having a different composition is introduced. Transfer and grow seed crystals during growth. As a result, it is possible to grow a crystal while maintaining a high growth rate in a specific crystal axis direction and a low growth rate in other crystal axis directions. Therefore, it is possible to efficiently produce a crystal that has grown greatly in a specific direction. .
The same kind of operation may be repeated such that when the growing seed crystal is grown to some extent in the second raw material solution, the growing seed crystal is transferred and grown in the third raw material solution having a different composition. Further, the same kind of operation may be repeated such that when the growing seed crystal is grown to some extent in the second raw material solution, the growing seed crystal is grown back into the original first raw material solution.

In a second aspect, the present invention provides the crystal manufacturing method having the above structure, wherein the second raw material solution has a crystal component or dopant concentration different from that of the first raw material solution. .
As a result of intensive research by the present inventor, when a seed crystal is put in a raw material solution, the growth rate in a specific crystal axis direction is initially high and the growth rate in other crystal axis directions is low, but after the crystal habit appears. It was found that the growth rate in each crystal axis direction maintained the crystal habit. Furthermore, when the growing seed crystal is transferred into a raw material solution having a different concentration of crystal component or dopant from the initial raw material solution, the growth rate in a specific crystal axis direction is increased again, while the growth rate in the other crystal axis direction is decreased. After the crystal habit appeared, it was found that the growth rate in each crystal axis direction maintained the crystal habit.
Therefore, in the crystal manufacturing method according to the second aspect, when the seed crystal is grown to some extent in the first raw material solution instead of continuing to grow the seed crystal in the same raw material solution, the concentration of the crystal component or dopant differs. 2 The seed crystal is grown and grown in the raw material solution. As a result, it is possible to grow a crystal while maintaining a high growth rate in a specific crystal axis direction and a low growth rate in other crystal axis directions. Therefore, it is possible to efficiently produce a crystal that has grown greatly in a specific direction. .

In a third aspect, the present invention provides a TGS-based crystal seed crystal in a first raw material solution containing a triglycine sulfate (TGS) -based crystal component and a dopant for crystal growth, and then the first raw material solution and the crystal component. Alternatively, the present invention provides a crystal manufacturing method characterized in that a seed crystal during growth is transferred to a second raw material solution having a different dopant concentration and further crystal growth is performed.
As a result of intensive research by the present inventor, when a seed crystal is put in a raw material solution, the growth rate in a specific crystal axis direction is initially high and the growth rate in other crystal axis directions is low, but after the crystal habit appears. It was found that the growth rate in each crystal axis direction maintained the crystal habit. Furthermore, when the growing seed crystal is transferred into a raw material solution having a different concentration of crystal component or dopant from the initial raw material solution, the growth rate in a specific crystal axis direction is increased again, while the growth rate in the other crystal axis direction is decreased. After the crystal habit appeared, it was found that the growth rate in each crystal axis direction maintained the crystal habit.
Therefore, in the crystal manufacturing method according to the third aspect, if the TGS seed crystal is grown to some extent in the first raw material solution rather than continuing to grow the seed crystal in the same raw material solution, the concentration of the crystal component or dopant is increased. The growing seed crystal is transferred and grown in a different second raw material solution. As a result, a crystal can be grown while maintaining a high growth rate in the a-axis direction and the c-axis direction and a low growth rate in the b-axis direction. Therefore, a TGS system that has grown greatly in the a-axis direction and the c-axis direction. Crystals can be produced efficiently. That is, a TGS crystal suitable for use as a pyroelectric element can be efficiently produced.
The same kind of operation may be repeated such that when the growing seed crystal is grown to some extent in the second raw material solution, the growing seed crystal is transferred and grown in the third raw material solution having a different composition. Further, the same kind of operation may be repeated such that when the growing seed crystal is grown to some extent in the second raw material solution, the growing seed crystal is grown back into the original first raw material solution.
Note that the polarization direction can be controlled by adding a dopant.

In a fourth aspect, the present invention provides a crystal manufacturing method, wherein the dopant is L-α-alanine in the crystal manufacturing method having the above-described configuration.
In the crystal manufacturing method according to the fourth aspect, instead of continuing to grow seed crystals in the same raw material solution, when a TGS seed crystal is grown to some extent in the first raw material solution containing L-α-alanine as a dopant, The seed crystal during growth is transferred and grown in a second raw material solution that does not contain L-α-alanine or has a different concentration. As a result, a crystal can be grown while maintaining a high growth rate in the a-axis direction and the c-axis direction and a low growth rate in the b-axis direction. Therefore, a TGS system that has grown greatly in the a-axis direction and the c-axis direction. Crystals can be produced efficiently. That is, a TGS crystal suitable for use as a pyroelectric element can be efficiently produced.

In a fifth aspect, the present invention provides a first tank for storing a first raw material solution, a second tank for storing a second raw material solution having a composition different from that of the first raw material solution, and the first raw material solution. Seed crystal holding means for holding a seed crystal; raw material solution changing means for transferring a growing seed crystal from the first raw material solution to the second raw material solution; and temperature control means for controlling the temperature of the raw material solution A crystal manufacturing apparatus is provided.
In the crystal manufacturing apparatus according to the fifth aspect, the crystal manufacturing method having the above configuration can be suitably implemented.

  According to the crystal manufacturing method and the crystal manufacturing apparatus of the present invention, it is possible to manufacture a crystal that has grown greatly in a specific direction. For example, it is possible to efficiently produce a TGS-based crystal that is suitable for use as a pyroelectric element and has grown greatly in the a-axis direction and the c-axis direction.

  Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is a configuration explanatory view showing a crystal manufacturing apparatus 100 according to the first embodiment.
The crystal manufacturing apparatus 100 includes a semicylindrical first tank 1v that stores a first raw material solution 1s, and a semicylindrical second tank 2v that stores a second raw material solution 2s having a composition different from that of the first raw material solution 1v. A first stirrer 1r that stirs the first tank 1v, a second stirrer 2r that stirs the second tank 2v, a first holder 1h that holds the first seed crystal C1, and a second seed crystal C2. A second holding tool 2h that holds the first holding tool 1h, a second lift 2f that moves the second holding tool 2h up and down, a first raw material solution 1s, and a second raw material solution. The temperature control tank 4 for controlling the temperature of 2 s, the heater 3 for not lowering the temperature of the upper part of the temperature control tank 4, and the central axis of the cylindrical shape combining the first tank 1v and the second tank 2v are the rotation axes As well as the first lift 1f and the second lift 2f. A turntable 5 which lifting, and comprises a support base 6 which rotatably supports the turntable 5.

FIG. 2 is a flowchart illustrating the crystal manufacturing process according to the first embodiment.
In step S1, the first holding jig 1h and the second holding jig 2h are pulled up to a position where the lower end is not immersed in the raw material solution, and the turntable 5 is removed.

In step S2, the first seed crystal C1 is held at the lower end of the first holding jig 1h, and the second seed crystal C2 is held at the lower end of the second holding jig 2h.
For example, the first seed crystal C1 and the second seed crystal are DLATGS crystals having a (0-10) plane with a certain area. As a specific example, it is a DLATGS crystal having a flat plate shape having a length in the a-axis direction of 10 mm × a length in the c-axis direction of 10 mm × a thickness in the b-axis direction of 0.8 mm. Adhere these with adhesive tape.

In step S3, the 1st raw material solution 1s is put into the 1st tank 1v, and the 2nd raw material solution 2s is put into the 2nd tank 2v.
For example, the first raw material solution 1s is an aqueous solution containing a TGS crystal component such that the molar ratio is glycine: sulfuric acid = 3: 1 and 5 mol% of L-α-alanine as a dopant. The second raw material solution 2s is an aqueous solution containing a TGS crystal component such that the molar ratio is glycine: sulfuric acid = 3: 1 and 30 mol% of L-α-alanine as a dopant.

In step S4, the turntable 5 is set on the temperature control tank 4 so as to be placed on the support base 6, and the temperature in the temperature control tank 4 is set to a predetermined temperature.
For example, the temperature is 40 ° C.

  In step S5, the first holding jig 1h and the second holding jig 2h are pulled down, and as shown in FIG. 1, the first seed crystal C1 is put into the first raw material solution 1s, and the second seed crystal C2 is put into the second raw material solution 2s. Put in.

In step S6, crystals are grown while the temperature in the temperature control tank 4 is lowered. Moreover, the 1st raw material solution 1s is stirred with the 1st stirrer 1r suitably, and the 2nd raw material solution 2s is stirred with the 2nd stirrer 2r.
For example, the rate of lowering the temperature is 0.03 ° C./day to 0.3 ° C./day.
In step S7, step S6 is continued until crystal habit appears in any of the growing seed crystals C1 and C2, and if crystal habit appears, the process proceeds to step S8.
For example, in the case of the tabular TGS-based seed crystal exemplified in step S2, the growth rate in the direction in which the growing crystal plate expands is monitored, and when the growth rate slows down, it is determined that crystal habit has appeared, and step S8. Proceed to

In step S8, the first holding jig 1h and the second holding jig 2h are pulled up to a position where the lower end is not immersed in the raw material solution as shown in FIG. 3, and the turntable 5 is rotated 180 ° as shown in FIG. As shown in FIG. 5, the first holding jig 1h and the second holding jig 2h are pulled down to a position where the lower end is immersed in the raw material solution. That is, the growing first seed crystal C1 is put in the second raw material solution 2s, and the growing second seed crystal C2 is put in the first raw material solution 1s.
Note that the heater 3 has an upper portion of the temperature control tank 4 to prevent the growing seed crystals C1 and C2 from cracking due to a temperature difference when the first holding jig 1h and the second holding jig 2h are pulled up. It is warm. If the temperature can be controlled so that the growing seed crystals C1 and C2 are not broken by the temperature difference when the first holding jig 1h and the second holding jig 2h are pulled up, the heater 3 may be omitted.

In step S9, the crystal is grown while lowering the temperature in the temperature control tank 4 by the heater 3. Moreover, the 1st raw material solution 1s is stirred with the 1st stirrer 1r suitably, and the 2nd raw material solution 2s is stirred with the 2nd stirrer 2r.
In step S10, step S9 is continued until a crystal habit appears in any of the growing seed crystals C1 and C2, and if a crystal habit appears, the process proceeds to step S11.

  In step S11, the growing first seed crystal C1 is put in the first raw material solution 1s and the growing second seed crystal C2 is put in the second raw material solution 2s by the reverse operation of step S8. Then, the process returns to step S6.

  Note that Steps S6 to S11 are repeated, and when the growing seed crystals C1 and C2 are grown to a required size, the process is terminated, and the grown crystals are taken out.

  According to the crystal manufacturing apparatus 100, a crystal greatly grown in a specific direction can be efficiently manufactured. For example, it is possible to efficiently produce a TGS-based crystal that is suitable for use as a pyroelectric element and has grown greatly in the a-axis direction and the c-axis direction.

  Instead of moving the seed crystal up and down and rotating, the raw material solution may be moved up and down and rotating.

  Three or more raw material solutions having different compositions may be prepared and grown while cyclically transferring seed crystals.

  In addition to the LATGS crystal, the present invention can also be applied to the production of crystals such as DLATGS crystal and TGSP crystal.

  The crystal production method and the crystal production apparatus of the present invention can be used to produce a TGS crystal having a shape suitable as a pyroelectric element.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory view showing a crystal manufacturing apparatus according to Example 1; FIG. 3 is a flowchart showing a crystal manufacturing process according to Example 1. It is explanatory drawing which shows the state which pulled up the seed crystal. It is explanatory drawing which shows the state which rotated the seed crystal. It is explanatory drawing which shows the state which pulled down the seed crystal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1s 1st raw material solution 1v 1st tank 1h 1st jig 2s 2nd 2nd raw material solution 2v 2nd tank 2h 2nd jig 3 Heater 4 Temperature control tank 5 Turntable 6 Support stand C1 1st seed crystal C2 2nd seed crystal 100 Crystal production equipment

Claims (5)

  A method for producing a crystal, comprising putting a seed crystal in a first raw material solution and growing the crystal, and then transferring the growing seed crystal to a second raw material solution having a composition different from that of the first raw material solution to further grow the crystal.   2. The crystal manufacturing method according to claim 1, wherein the second raw material solution has a concentration of a crystal component or a dopant different from that of the first raw material solution.   A TGS-based crystal seed crystal is put into a first raw material solution containing a triglycine sulfate (TGS) -based crystal component and a dopant to grow a crystal, and then a second raw material solution having a concentration of the crystal component or dopant different from that of the first raw material solution A method for producing a crystal, comprising transferring a seed crystal during growth to crystal growth.   The crystal manufacturing method according to claim 3, wherein the dopant is L-α-alanine.   A first tank for storing a first raw material solution, a second tank for storing a second raw material solution having a composition different from that of the first raw material solution, and a seed crystal holding for holding a seed crystal in the first raw material solution Characterized by comprising: means; a raw material solution changing means for transferring the seed crystal during growth from the first raw material solution into the second raw material solution; and a temperature control means for controlling the temperature of the raw material solution. Manufacturing equipment.

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