JP3015552B2 - LiTaO3 single crystal material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a single crystal material used in relates to raw materials used in the manufacture of single crystal, in particular produced by pulling oxide single crystals such as LiTaO ₃ by Czochralski .

[0002]

2. Description of the Related Art Conventionally, LiTaO ₃ , LiNb
As one method for producing an oxide single crystal such as O ₃ or Li ₂ B ₄ O ₇ , a pulling method called the Czochralski method is known. In the Czochralski method, a raw material is contained in a melting crucible made of a noble metal such as Pt or Pt-Rh, and the raw material is heated and melted by a heating means such as a high-frequency coil provided around the melting crucible. In this method, a single crystal is grown by bringing the seed crystal into contact with the melt and pulling it while rotating the seed crystal.

[0003]

In producing a LiTaO ₃ single crystal by the Czochralski method,
Irregular bubbles such as size, position and number may be generated in the obtained crystal, and such generation of bubbles has been one of the causes of lowering the production yield. Such randomly generated bubbles in the crystal are generally called all pores because they are generated in the entire interior. Such a bubble (hereinafter referred to as "all pores") may be generated when the temperature of the raw material melt fluctuates. However, at present, generation of all pores cannot be prevented only by controlling the temperature of the raw material melt. . Therefore, it has been desired to reduce the occurrence of such all pores as much as possible by studying other factors.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a LiTaO ₃ single crystal material capable of reducing the generation rate of all pores and improving the production yield.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for producing LiTaO ₃ single crystal by the Czochralski method, which comprises Ta ₂ O ₅ and Li ² CO ₃ which are industrially obtained as raw materials.
⁽³⁾ Focused on the particle size of the powder.

At present, LiTa by the pulling method is used.
As the O ₃ single crystal material, Ta ₂ O ₅ and Li ₂ CO
₃ are used. The particle size of Li ₂ CO ₃ is usually 20μ
It is considered to be a stable particle with a moisture absorption of about m. Ta ₂ O _{5, on the} other hand, has an average particle size on the order of submicrons (based on the aeration method) and is an active fine particle compared to Li ₂ CO ₃ . Therefore, L
Ta ₂ in the single crystal material in the production of iTaO ₃ single crystal
The average particle diameter of O ₅ and the total pore generation rate of the pulled LiTaO ₃ single crystal were compared and examined. As a result, when LiTaO ₃ single crystal is pulled up using Ta ₂ O ₅ powder having an average particle diameter (by aeration method) in the range of 0.70 to 0.80 μm, the number of occurrences of all pores is reduced. It turned out to be.

The average particle diameter of Ta ₂ O ₅ used as a LiTaO ₃ single crystal material is preferably 0.70 to 0.80 μm, and more preferably 0.70 to 0.75 μm. When melted in a Pt-Rh crucible, Ta ₂ O
_If the average particle size of ₅ is larger than 0.80 μm, it becomes difficult to dissolve at the time of heating, the gas is not sufficiently diffused from the inside of the melt, and bubbles (all pores) are easily generated. In heating for the same time, the smaller the particle size, the easier it is to dissolve,
_If the average particle diameter of ₂ O ₅ is smaller than 0.70 μm, the miscibility with Li ₂ CO ₃ becomes extremely poor, causing segregation of the material and resulting in a defective product in the final product.
Not preferred.

The relationship between the impurity content in the single crystal material and the rate of occurrence of all pores was examined, and the results are shown in FIGS. 2, 3 and 4. FIG. 2 is included as an impurity
Fig. 3 shows the relationship between the Si content and the incidence rate of all pores, Fig. 3 shows the relationship between the Al content contained as impurities and the incidence rate of all pores, and Fig. 4 shows the moisture content and the incidence rate of all pores. Are shown, respectively. As is clear from these figures, it is understood that factors other than the average particle diameter of Ta ₂ O ₅ do not affect the incidence rate of all pores.

[0009] The present invention, in producing a LiTaO ₃ single crystal by pulling method using Pt-Rh crucibles
In the LiTaO ₃ single crystal material mainly composed of Ta ₂ O ₅ and Li ₂ O ₃ used, the average particle diameter of Ta ₂ O ₅ (by aeration method) is set to 0.70 to 0.80 μm. I do.

[0010]

In the LiTaO ₃ single crystal material of the present invention thus constituted, by setting the average particle diameter of Ta ₂ O ₅ (by aeration method) to 0.70 to 0.80 μm,
While maintaining good mixing with Li ₂ CO _3, it can be easily dissolved at the time of heating, and gas can be sufficiently diffused from the inside of the melt at the time of melting.

As a result, the generation rate of all pores is reduced, and a high-quality LiTaO ₃ single crystal can be manufactured with a high yield.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

EXAMPLE As a melting crucible accommodating a single crystal material, (an outer diameter of 124
mm, height 122 mm, using a Pt-Rh crucibles thickness 2 mm (Rh content _{30%), Ta 2 O 5} ( average particle diameter 0.70
0.75 .mu.m, Mitsui Mining & Smelting Co., Ltd.) and Li ₂ CO ₃ each powder 8.9 kg, and then 57.0kg weighed and mixed in a V blender, then press them in advance at 70 kg / cm ² pressure of about ware After sintering, it was ground and stored in a melting crucible. The impurities contained in the single crystal material were combined with 2 ppm of Si, 1 ppm of Al, 1 ppm of Fe, 1 ppm of Cu,
And Nb was 5 ppm or less. Similarly, the water content of the single crystal material was 0.04% at the time of receiving the raw materials, and 0.04% at the time of weighing and mixing.

The above-mentioned single crystal material is heated and melted to a temperature of 1650 ° C. or more by a high-frequency coil provided around a Pt-Rh crucible, degassed for 1 hour to remove mixed air, and then cooled to <111. > Was blended with the melted raw material, and the LiTaO ₃ single crystal was pulled up while rotating the seed crystal at 10 rpm.

The pulling speed was 5.4 mm / hr, and the crystal was grown for 15 hours. The shoulder portion was formed by pulling up until the diameter of the crystal became 3 inches, and then the growth of the straight body was started. When the straight body was pulled up by about 80 mm, the single crystal grown from the raw material melt was cut off and cooled.

No bubbles or cracks were observed in the LiTaO ₃ single crystal thus obtained. Furthermore, a crystal having a diameter of 4 mm and a length of 75 mm was cut out in parallel with the pulling axis, and after polishing both end faces thereof, almost no distortion was observed when distortion was observed in the crystal longitudinal direction with a Twyman-Green interferometer.
High quality crystals with very little optical distortion were obtained.

When 138 Lot of LiTaO ₃ single crystal was pulled up using the single crystal material of the present invention including the above-mentioned embodiment, the number of bubbles (total pores) was 0.7%. %Met.

Comparative Example 1 As a LiTaO ₃ single crystal material, a Ta ₂ O ₅ powder having an average particle size (0.61 to 0.69 μm) not according to the present invention was used, and LiTaO ₃ was produced in the same manner as in Example 1. When the single crystal was pulled, the pulled LiTaO
_3. Bubbles (all pores) were generated in the single crystal.

[0019] Comparative Example 2 LiTaO ₃ single crystal material, the average particle diameter is not according to the invention (0.81~0.90μm) Ta ₂ O ₅ powder with, LiTaO ₃ single in the same manner as in Example 1 When the crystal was pulled, the pulled LiTaO ₃
Bubbles (all pores) were generated in the single crystal.

In addition, when the 307 Lot LiTaO ₃ single crystal using the Ta ₂ O ₅ powder having an average particle size not in accordance with the present invention, including Comparative Examples 1 and 2, was pulled up, bubbles (all pores) were observed. ) Has reached 6.2%.

FIG. 1 shows 138 Lo including the embodiment.
t and 307 Lot of L including Comparative Examples 1 and 2
When the iTaO ₃ single crystal was pulled, Ta ₂ O ₅
The relationship between the average particle size of the powder (by the aeration method) and the occurrence rate of all pores is shown. As is clear from FIG. 1, according to the present invention, the rate of occurrence of all pores is reduced from 6.2% to 0.2%.
It was reduced to 7%.

[0022]

As described above, according to the present invention, T
a ₂ average particle diameter of the O ₅ powder (by insufflation) from 0.70 to 0.8
By setting the thickness to 0 μm, the rate of generation of bubbles (all pores) in the pulled LiTaO ₃ single crystal can be reduced.
Good quality LiTaO ₃ single crystals can be obtained with high yield.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the average particle diameter of Ta ₂ O ₅ powder and the rate of occurrence of all pores.

FIG. 2 is a diagram showing the relationship between the content of Si contained as an impurity in Ta ₂ O ₅ powder and the incidence rate of all pores.

FIG. 3 is a graph showing the relationship between the content of Al contained as an impurity in Ta ₂ O ₅ powder and the rate of occurrence of all pores.

FIG. 4 is a graph showing the relationship between the water content of Ta ₂ O ₅ powder and the rate of occurrence of all pores.

Claims (1)

(57) [Claims] 1. A method for producing a LiTaO ₃ single crystal by a pulling method using a Pt-Rh crucible , Ta
In LiTaO ₃ single crystal material mainly composed of ₂ O ₅ and Li ₂ O _3, LiTaO ₃ single, characterized in that the average particle size of the Ta ₂ O ₅ and (by insufflation) and 0.70~0.80μm Crystal material.