JPS63206393A - Production of single crystal - Google Patents

Abstract

PURPOSE:To improve the production efficiency of single crystal in the production of a compound oxide single crystal containing boron as a constituent element by pulling up process, by adding a specific impurity to decrease the viscosity of molten liquid. CONSTITUTION:In the production of a compound oxide single crystal containing boron as one of constituent elements, the crystallization raw material is added with a specific impurity to decrease the viscosity of molten liquid of the boron- containing compound oxide at the production temperature of the above oxide single crystal. The specific impurity is preferably Pb, Bi, As, Ga, their oxides or their arbitrary mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention particularly relates to an oxide containing B as one of its constituent elements.
This invention relates to a method for efficiently producing single crystals by a pulling method.

(Prior Art and Problems to be Solved by the Invention) β-BaBtO4 is a nonlinear optical crystal that has attracted attention in recent years. The compound with the stoichiometric composition aBtO4 is 9
The crystallographic atomic structure changes with a boundary temperature of 25°C (so-called phase transformation). In this case, the high-temperature phase crystal at 925°C or higher is α type (denoted as α-BaBaOa), and the low-temperature phase crystal at 925°C or lower is β type. type (denoted as β-BaBxOn),
As mentioned above, the promising optical crystals are:
Among these, it is the β type. This is because the high-temperature phase α-Bat
This is because te4 has a center of symmetry, but β-BaB, 04 has no center of symmetry due to atomic displacement, and therefore nonlinear characteristics occur.

To obtain Ba8gO4 crystals, it is generally used as the base material! 1acO* and B2O. are mixed in a molar ratio of 1:1 and heated and melted to form BaCO3+ BgOs → BaBgOn + Co
! By the reaction ↑, a BaBtOn melt is obtained.
This melt is single-crystalized by a pulling method etc. to obtain BaBz
Obtain an O4 single crystal.

By the way, as mentioned above, < BaCO3 and B, 0. When the ratio is 1:1, the melting temperature of the base material is 1095°C, and conversely, when a melt heated above this temperature is cooled, crystallization starts at 1095°C. However, since the crystals in this case are crystallized at temperatures above 925°C, α
-It crystallizes as BaBtOa.

Furthermore, this solidified crystal was cooled until the crystal temperature reached 92
When the temperature drops below 5° C., the phase transforms to β-BaBtO4, but as mentioned above, the direction of the change in the constituent atoms varies depending on the location. In other words, since "domains" are formed, uniform β-Ba with atoms displaced in one direction throughout the crystal.
It is difficult to transform BzO4, and even if it transforms, its uniformity is poor, making it impossible to obtain a high-quality single crystal.

In this case, a high-quality single crystal is β-Ba with “no domain”.
It is a dge4 crystal. This problem can be avoided and high quality β-
To obtain a Batte 4 single crystal, prepare a melt at 925°C or lower and cool it to directly produce β-BaB.
A possible method is to crystallize a YO04 single crystal. β-Bai whose entire atomic structure is uniform due to the change from liquid to solidification
This is because a t'4 single crystal can be obtained extremely easily.

By the way, methods for lowering the melt temperature of the base material (melt temperature during crystal production) include (a) the so-called self-flux method, in which the blending ratio of the base materials is shifted;
-flux) and (b) a completely different flux (f) in addition to the base material.
There is a flux method that adds lux).

In the case of BaBgOi, to realize the self-flux method, B! 0. For example, Na, GO, etc. may be added to realize the flux method. In either case, a molten liquid state can be realized at a temperature of 925° C. or lower.

However, with either method, lowering the temperature of the melt creates new and significant problems.

That is, B, 0.0. The viscosity increases at low temperatures and is as high as 230 poise at 900°C, so the viscosity of the melt is also high, resulting in poor heat conduction and making it impossible to efficiently obtain large single crystals. Specifically, when the pulling method (Chickralski or chiroporous method) is carried out from such a melt, the rate is 0.1 to 0.0% per hour.
The problem is that the growth rate is extremely slow, and it is difficult to obtain high-quality crystals that are free of inclusions such as air bubbles caused by large crystals and water contained in ados.

Furthermore, LiJ, which has piezoelectricity, is another B-containing compound.
There is 40t. In this case, there is no need to lower the melt temperature due to phase transformation, but from another point of view, a large amount of 8
30. Requires. That is, the base material LigCOs
By mixing and Btus at a molar ratio of 1:2 and heating at 917°C or higher, LigCOs + 28tus → Li8BaOy+
A molten liquid of LiJ40 is formed by the reaction of COg ↑, and it is made into a single crystal by a pulling method or the like.

In this case, B2O. requires twice the amount of other base materials (Li!(:Os)), and the temperature during crystal pulling is 917°C.
Because it is directly above the molten liquid, the viscosity of the molten liquid is as high as 200 to 230 poise.According to experiments, in order to obtain large crystals that do not contain inclusions such as bubbles, a viscous molten liquid of this level requires a This required an extremely slow pulling speed of .3 to 1.0 m, resulting in extremely poor production efficiency.

As can be seen from the various examples above, B20. Since the viscosity of crystal changes greatly with temperature, other conditions such as crystal pulling temperature and pulling speed are specified, which becomes a constraining factor in achieving optimal conditions including production efficiency. Wata.

(Object of the invention) The present invention was proposed to improve the above-mentioned drawbacks, and its purpose is to reduce the high viscosity of the melt when growing an oxide single crystal containing B as one of its constituent elements. The objective is to realize a low-viscosity raw material melt that solves certain problems and to produce B oxide single crystals with high efficiency.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides, when manufacturing a composite oxide single crystal containing boron as one of the constituent elements, at a temperature at which the oxide single crystal is manufactured. The gist of the invention is a method for producing a single crystal, which is characterized by adding a specific impurity that reduces the viscosity of a boron-containing complex oxide melt.

The present invention provides B20. By adding specific impurities, the viscosity at the liquidus temperature Tg during crystal production of a melt mainly composed of
The most important feature is to reduce the viscosity of the melt at the liquidus temperature Tg.

In addition, conventionally, specific impurity elements are added to change the properties of the resulting single crystal, but specific impurities are also added to reduce the viscosity of the melt in which the crystal grows. There is no report.

Next, examples of the present invention will be described. It should be noted that the embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the spirit of the present invention.

[Example 1] BaB104 is a mixture of BaCO5 and B20. molar ratio 1:1
When heated, it undergoes congruent melting at 1095°C and crystallizes as α-BaBiO4, and below about 925°C, the crystal structure does not have central symmetry and belongs to the practically meaningful space group R8. β-BaBaO1 undergoes a phase metamorphosis. Here, due to the problems explained in the prior art section, in order to efficiently produce high-quality β-Baboo4 crystals, the melt temperature must be below 925°C.For this purpose, the above-mentioned Using the self-flux method, B2O.
It is possible to increase the temperature of the melt and lower the temperature of the melt.

However, B2O. The viscosity of is ~110 at 1000℃
Poise is as high as ~230 poise at 900°C, so it is 81
0. The viscosity of the low-temperature melt increases significantly, making it unsuitable for crystal growth. Therefore, Btus (Pb), which is a mixture of 5 mol% pbo in a, O, used, is used as a starting material, and the molar ratio of BaCO5 and this Btus (Pb) is 1:1. The temperature Tg was lowered to ~920°C. As a result, the viscosity of the melt in this case was 20 to 2 S poise, which was about 1710 smaller than the viscosity in the case without pbo addition, and as a result of increased heat conduction, production of single crystals became extremely easy.

[Example 2] In Example 1, the so-called self-flux (
Although this is a self-flux method, there is a method of lowering the liquidus temperature using a flux as a method of obtaining crystals after phase transformation. Several fluxes are possible for producing 810g of β-fia, but here we use Na1C
Using O3 X BaCO5+ 7 Na1CO3+ Z Btus
In the raw material mixture of (Pb), 27≦X≦32.17≦
y≦22. A solution with a molar ratio of Z-50 was mixed with B2O. β-Ba
A BgOa single crystal could be grown. The viscosity of the solution at this time is 1/2 compared to when using non-additive BtO.
The size of the crystal was 1/10, so a large single crystal could be easily obtained.

In the above embodiments, the case of the self-flux method was explained, but it is easy to understand that low temperature and low viscosity can be achieved by the flux method as well.

In this way, by mixing other elements that lower the viscosity with Btus used as the base material (such as 82O
．． is written as BzOs(X), and the case of x-pb was described in the previous embodiment. ), self-flux method, or flux method, a low-viscosity melt can be achieved even at low temperatures, and therefore high-quality β-BaB*Os single crystals can be obtained easily and efficiently.

[Example 3] In Example 1.2, B, 0. A low-temperature, low-viscosity solution was achieved by mixing Pb (added in the form of PbO) with Pb.
B2O. in which 2.5 mol% of Bi (or Bit's) was mixed instead of bo. When using BxOs, the viscosity is about 100 poise in the temperature range of 920 to 850°C, and the viscosity of BxOs without additives is about 172, and As (or As103) is added to 0.
．． B mixed with 8 mol%, 0. When using , the viscosity is ~130
Poise, the viscosity is reduced to about 60%, Example 1.2
β-Batte4 single crystal could be efficiently obtained in the same manner as above.

Ga and its oxides at 8.0. A similar effect was obtained when added to

Note that it is also possible to use two or more of Pb, Bi, As, Ga, or their oxides □ as additives.

(Effect of the invention) As explained above, β-BaB10. A melt at 925° C. or lower is required to produce a single crystal, and it is essential for crystal growth to minimize the viscosity of this melt. This is because high viscosity results in poor heat conduction (the crystal growth rate must be slowed down), and to solve this problem, lowering the viscosity of the melt is important for efficient crystal production. According to the present invention, the viscosity of the liquid is reduced by 1/2 to 1/1 (b) compared to the case without additives by mixing specific additive elements to the main raw materials B and 0. There is an advantage that it can be done.

In addition, in the examples, Pb (PbO) was used as a specific additive element.
.

An example was given in which Bi (BiOs) and ^S (^5g0s) were set as mol% as described, but the present invention does not specify this mixing ratio. The goal is to reduce the viscosity of Therefore, as can be seen from the examples, instead of using pre-mixed BIOs (X), adding specific elements in the form of metals or oxides to the melt that can produce β-BaBgOa single crystals has no effect. It's the same. Furthermore, although the optical refractive index of β-Ba8gO4 thus obtained increased slightly, other properties did not change at all.

In addition, B oxide crystals other than β-BaB*04 (for example,
It can be easily inferred that the present invention is also applicable to Li*B40y shown in the conventional example. That is, Li
When using a large amount of Btus as a base material such as J<Ov, being able to reduce the viscosity of the melt at low temperatures increases the degree of freedom in optimizing manufacturing conditions, and is practical.
Needless to say, it is even more effective.

Claims (3)

[Claims] (1) When producing a complex oxide single crystal containing boron as one of the constituent elements, certain impurities are added to reduce the viscosity of the complex oxide melt containing boron at the temperature at which the oxide single crystal is produced. A method for producing a single crystal, characterized in that a single crystal is added. (2) When producing a single crystal When forming a melt of complex oxide, P is added as an impurity to reduce the viscosity of the melt.
2. The method for producing a single crystal according to claim 1, wherein any one or more of Bi, As, Ga, or oxides thereof are mixed. (3) Pb, Bi, As as impurities in B_2O_3
, Ga, PbO, Bi_2O_3, As_2O_3, G
The method for producing a single crystal according to claim 1, characterized in that the single crystal is produced using B_2O_3, which is a mixture of any one or two or more of a_2O_3, as a raw material.