JP2012250874A - Iridium crucible, and method for producing lithium tantalate single crystal using the same - Google Patents
Iridium crucible, and method for producing lithium tantalate single crystal using the same Download PDFInfo
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本発明はイリジウムルツボに関し、特に、チョクラルスキー法（Ｃｚ法）を用いたタンタル酸リチウム単結晶の製造に使用されるイリジウムルツボに関する。 The present invention relates to an iridium crucible, and more particularly to an iridium crucible used for producing a lithium tantalate single crystal using the Czochralski method (Cz method).
表面弾性波素子等に好適に用いられるタンタル酸リチウム単結晶は、一般にチョクラルスキー法によって製造されている。チョクラルスキー法によってタンタル酸リチウム単結晶を製造する場合には、（１）炉の中で、イリジウム製のルツボのまわりを耐火物で囲み、該ルツボ又は耐火物の上に、ルツボ上部の温度勾配を適切に保つための熱反射の機能を持たせたアフターヒーター、及び、アフターヒーター蓋を有する貴金属製の構造物を設置し、（２）原料となるタンタル酸リチウム結晶塊をルツボの中で加熱溶融し、（３）得られた融液に種結晶を浸漬した後に、（４）所定の回転数で、種結晶及びルツボを回転させながら該種結晶を静かに引き上げ、（５）種結晶の下にタンタル酸リチウムの単結晶を成長させるのが一般的である。 A lithium tantalate single crystal suitably used for a surface acoustic wave device or the like is generally manufactured by the Czochralski method. When producing a lithium tantalate single crystal by the Czochralski method, (1) Surrounding the iridium crucible with a refractory in a furnace, the temperature at the top of the crucible is placed on the crucible or the refractory. An after-heater with a function of heat reflection to keep the gradient appropriate, and a precious metal structure with an after-heater lid were installed, and (2) the lithium tantalate crystal mass as a raw material was placed in the crucible (3) After the seed crystal is immersed in the obtained melt, (4) the seed crystal is gently pulled up while rotating the seed crystal and the crucible at a predetermined rotational speed, and (5) the seed crystal. It is common to grow a single crystal of lithium tantalate underneath.
図４は、３６度回転Ｙ軸タンタル酸リチウムの単結晶、若しくは３８度回転Ｙ軸タンタル酸リチウムの単結晶の製造に用いられている、従来の、タンタル酸リチウム単結晶製造装置の縦概略断面図である。 FIG. 4 is a schematic vertical sectional view of a conventional lithium tantalate single crystal manufacturing apparatus used for manufacturing a single crystal of 36 ° rotated Y-axis lithium tantalate or a single crystal of 38 ° rotated Y-axis lithium tantalate. FIG.
図４に示されるように、従来のタンタル酸リチウムの単結晶製造装置は、耐火性ルツボ台２３と、ルツボ台２３の底部に設けられたアルミナ台２２と、アルミナ台２２上に設けられたルツボ２１と、ルツボ２１を囲む断熱材２４と、断熱材２４の上部に設けられた耐火性アルミナ２５を備え、更に、ルツボ２１の上方に設けられたアフターヒーターと称される円筒状の熱反射板２７と、アフターヒーター２７の蓋であるアフターヒーター蓋２８を備えている。必要に応じて、ルツボ２１の上部には、リフレクターと称されるドーナツ型で円板状の熱反射板２６を設けることもできる。 As shown in FIG. 4, the conventional apparatus for producing a single crystal of lithium tantalate includes a refractory crucible base 23, an alumina base 22 provided at the bottom of the crucible base 23, and a crucible provided on the alumina base 22. 21, a heat insulating material 24 surrounding the crucible 21, and a refractory alumina 25 provided above the heat insulating material 24, and a cylindrical heat reflector called an after heater provided above the crucible 21. 27 and an after heater lid 28 that is a lid of the after heater 27. If necessary, a donut-shaped and disk-shaped heat reflecting plate 26 called a reflector may be provided on the upper portion of the crucible 21.
図４に示されるように、耐火性ルツボ台２３の周囲には、加熱コイル２９が設けられ、ルツボ２１を誘導加熱し、ルツボ２１内の原料を融解して、融液３０を調製し、シードホルダー３１に取り付けた種結晶３２を融液３０に浸漬した後、種結晶３２を引き上げる。これによって、円錐状の肩部３５ａと円柱状の胴部３５ｂよりなる、タンタル酸リチウム単結晶３５が生成される。 As shown in FIG. 4, a heating coil 29 is provided around the refractory crucible base 23 to heat the crucible 21, melt the raw material in the crucible 21, prepare a melt 30, and seed after the seed crystal 32 attached to the holder 31 is immersed in the melt 30, pulling the seed crystal 32. As a result, a lithium tantalate single crystal 35 composed of a conical shoulder portion 35a and a cylindrical body portion 35b is generated.
近年、上記のような単結晶を製造するコストを低減するために、ルツボの使用回数をできる限り増やして長期間使用する試みがなされている。しかしながら、ルツボの使用回数を増加させるにつれてルツボの変形が進み、その変形の仕方によっては、歩留まりが低下したりボイド等が単結晶中に含まれたりするという問題があった。 In recent years, attempts have been made to increase the number of times the crucible is used as much as possible in order to reduce the cost of manufacturing the single crystal as described above. However, as the number of times the crucible is used increases, deformation of the crucible progresses, and depending on how the crucible is deformed, there is a problem in that the yield decreases and voids are included in the single crystal.
そこで、従来からルツボの改良について研究がなされ（例えば、特許文献１及び２）ているが、何れも融液の温度勾配を制御し、自然対流を強くすることに主眼がおかれており、ルツボ自身の構造を改良するものではない。したがってこれらの従来技術においては、ランガサイト単結晶について言及されているものの、異方性の強いタンタル酸リチウム結晶については全く言及されていない。 Therefore, research on the improvement of the crucible has been made conventionally (for example, Patent Documents 1 and 2). However, both of them focus on controlling the temperature gradient of the melt and strengthening the natural convection. It does not improve its structure. Therefore, in these prior arts, although mention is made of a langasite single crystal, there is no mention of a highly anisotropic lithium tantalate crystal.
しかしながら、タンタル酸リチウム結晶の様に異方性が強い場合には、タンタル酸リチウム融液が冷却される際、あるいは固体が加熱されて融液になる際に、前記異方性が原因となってルツボを変形させるという特有の問題がある。したがって、前記従来技術によって、タンタル酸リチウム単結晶の製造に使用するルツボの使用回数を増大させることは不可能であった。 However, when the anisotropy is strong like the lithium tantalate crystal, the anisotropy is caused when the lithium tantalate melt is cooled or when the solid is heated to become a melt. There is a unique problem of deforming the crucible. Therefore, it has been impossible to increase the number of times the crucible used for manufacturing the lithium tantalate single crystal is used by the conventional technique.
したがって本発明の第１の目的は、チョクラルスキー法を用いた、異方性の強い単結晶の製造に好適なイリジウムルツボを提供することにある。
本発明の第２の目的は、低コストで、ボイドのような欠陥のないタンタル酸リチウム単結晶を製造する方法を提供することにある。
Accordingly, a first object of the present invention is to provide an iridium crucible suitable for producing a highly anisotropic single crystal using the Czochralski method.
A second object of the present invention is to provide a method for producing a lithium tantalate single crystal that is low in cost and free from defects such as voids.
本発明者は、上記の諸目的を達成するために鋭意検討を重ねた結果、ルツボが横方向に変形しやすいことに着目し、ルツボ底面側の板厚を側面方向の板厚よりも薄くして、底面側に変形を逃がすようなルツボ構造とし、ルツボが横方向に変形することを防いだところ、これによって、歩留まりを低下させることなく使用回数を増大させることができるだけでなく、底面に滞留するような融液がなくなり、自然対流によってルツボ内の融液が均一になるので、ボイド等の欠陥が発生しなくなることを見出し、本発明に到達した。 As a result of intensive studies to achieve the above-mentioned objects, the present inventor has paid attention to the fact that the crucible is easily deformed in the lateral direction, and has made the plate thickness on the bottom side of the crucible thinner than the plate thickness in the side direction. The crucible structure that allows deformation to escape on the bottom side prevents the crucible from deforming in the lateral direction, which not only increases the number of uses without reducing the yield, but also stays on the bottom surface. Thus, the present inventors have found that defects such as voids do not occur because the melt in the crucible becomes uniform due to natural convection, and no defects such as voids occur.
即ち本発明は、チョクラルスキー法によって融液から単結晶を育成させるために使用するイリジウムルツボであって、側面のイリジウム金属の厚みと底面のイリジウム金属の厚みをそれぞれｔ、ｔ’としたとき、ｔ>ｔ’であることを特徴とするイリジウムルツボ、及び、該ルツボを使用してタンタル酸リチウムの単結晶を育成することを特徴とするタンタル酸リチウム単結晶の製造方法である。
本発明においては、ｔ’は0.5ｔ≦ｔ’≦0.95ｔの関係を満たすことが好ましく、ｔは1.5ｍｍ以上10.0ｍｍ以下であることが好ましい。また、底面の形状は、丸味を帯びていることが好ましい。
That is, the present invention is an iridium crucible used for growing a single crystal from a melt by the Czochralski method, wherein the thickness of the iridium metal on the side surface and the thickness of the iridium metal on the bottom surface are t and t ′, respectively. T> t ′, and a method for producing a lithium tantalate single crystal characterized by growing a lithium tantalate single crystal using the crucible and the crucible.
In the present invention, t ′ preferably satisfies the relationship of 0.5 t ≦ t ′ ≦ 0.95 t, and t is preferably 1.5 mm or greater and 10.0 mm or less. Moreover, it is preferable that the shape of a bottom face is roundish.
本発明によれば、低コストで、ボイドのような欠陥のないタンタル酸リチウム単結晶を製造することが可能になる。 According to the present invention, it becomes possible to produce a lithium tantalate single crystal free from defects such as voids at low cost.
以下、添付図面に基づいて、本発明の好ましい実施態様につき、詳細に説明する。 Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
図１及び図２は、側面の肉厚より底面の肉厚の方が薄い、本発明のイリジウムルツボである。本発明においては、単にルツボ底面の肉厚が側面の肉厚より薄ければ良く、それ以外の形状は特に限定されない。例えば、図１は底面が平坦である場合であり、図２の場合には底面が丸くなっている。図３は従来のルツボであり、側面の肉厚と底面の肉厚は同じである。 1 and 2 show the iridium crucible of the present invention in which the bottom wall thickness is thinner than the side wall thickness. In the present invention, it is only necessary that the thickness of the bottom surface of the crucible is thinner than the thickness of the side surface, and other shapes are not particularly limited. For example, FIG. 1 shows a case where the bottom surface is flat, and in FIG. 2, the bottom surface is rounded. FIG. 3 shows a conventional crucible, in which the side wall thickness and the bottom wall thickness are the same.
一般に、タンタル酸リチウムのような単結晶製造装置は、図４に示されるように、セラミックス製の耐火性ルツボ台２３と、該耐火性ルツボ台２３の底部に設けられたアルミナ台２２と、該アルミナ台２２上に設けられたルツボ２１と、該ルツボ２１を囲む断熱材２４と、ドーナツ型で円板状の熱反射板であるリフレクター２６と、該リフレクター２６の上方に設けられた円筒状の熱反射板であるアフターヒーター２７と、該アフターヒーター２７の蓋であるアフターヒーター蓋２８と、ルツボ台２３の周囲に設けられた加熱コイル２９を備えている。 In general, a single crystal manufacturing apparatus such as lithium tantalate, as shown in FIG. 4, includes a ceramic fireproof crucible base 23, an alumina base 22 provided at the bottom of the fireproof crucible base 23, A crucible 21 provided on an alumina table 22, a heat insulating material 24 surrounding the crucible 21, a reflector 26 which is a donut-shaped and disk-like heat reflecting plate, and a cylindrical shape provided above the reflector 26 An after heater 27 that is a heat reflecting plate, an after heater cover 28 that is a lid of the after heater 27, and a heating coil 29 provided around the crucible base 23 are provided.
本発明にかかるイリジウムルツボは、図４中のルツボ２１に相当する。タンタル酸リチウムの単結晶を製造する場合には、ルツボ２１を誘導加熱し、ルツボ１内の原料を融解して融液３０とし、シードホルダー３１に取り付けた種結晶３２であるタンタル酸リチウム単結晶を融液３０に浸漬して、シードホルダー３１を回転させながら、種結晶３２を引き上げる。これによって、円錐状の肩部３５ａと円柱状の胴部３５ｂよりなるタンタル酸リチウム単結晶３５が生成される。 The iridium crucible according to the present invention corresponds to the crucible 21 in FIG. In the case of producing a lithium tantalate single crystal, the crucible 21 is induction-heated, the raw material in the crucible 1 is melted to form a melt 30, and the lithium tantalate single crystal that is the seed crystal 32 attached to the seed holder 31. Is immersed in the melt 30 and the seed crystal 32 is pulled up while rotating the seed holder 31. As a result, a lithium tantalate single crystal 35 composed of a conical shoulder portion 35a and a cylindrical body portion 35b is generated.
本発明のイリジウムルツボは、ルツボ底面側の板厚を側面方向よりも薄くして板厚の薄い底面側に変形を逃がすようなルツボ構造となっているので、ルツボが横方向に変形し難い。これによって、歩留まりを低下させることなく使用回数を増大させることができる。また、底面に滞留するような融液がなくなり、自然対流によってルツボ内の融液が均一になるので、ボイド等の欠陥が発生しなくなる
以下、本発明を実施例に基づいて更に説明するが、本発明はこれによって何ら限定されるものではない。
The iridium crucible of the present invention has a crucible structure in which the plate thickness on the bottom surface side of the crucible is made thinner than the side surface direction and the deformation is released to the bottom surface side where the plate thickness is thin. As a result, the number of times of use can be increased without reducing the yield. Further, there is no melt that stays on the bottom surface, and the melt in the crucible becomes uniform by natural convection, so that defects such as voids do not occur.Hereinafter, the present invention will be further described based on examples. This invention is not limited at all by this.
図１に示された形状のイリジウムルツボであって、円筒部の板厚が２ｍｍ、底部の板厚１．５ｍｍ、内径１５０ｍｍ、高さ１５０ｍｍのイリジウム製ルツボを、図４に示された３８度回転Ｙ軸タンタル酸リチウム単結晶の製造装置にセットし、３８度回転Ｙ軸タンタル酸リチウム単結晶を製造した。使用したリフレクターのサイズは、外径１６０ｍｍ、内径１０５ｍｍ、厚さ２ｍｍであり、アフターヒーターとしては直径１５０ｍｍ、高さ１８０ｍｍのイリジウム製アフターヒーターを使用した。 1. An iridium crucible having the shape shown in FIG. 1 and an iridium crucible having a cylindrical portion thickness of 2 mm, a bottom portion thickness of 1.5 mm, an inner diameter of 150 mm, and a height of 150 mm is shown in FIG. It set to the manufacturing apparatus of the rotation Y-axis lithium tantalate single crystal, and produced the 38 degree rotation Y-axis lithium tantalate single crystal. The size of the reflector used was an outer diameter of 160 mm, an inner diameter of 105 mm, and a thickness of 2 mm. As the after heater, an iridium after heater having a diameter of 150 mm and a height of 180 mm was used.
具体的には、ルツボ内に、組成比がＬｉ／Ｔａ＝０．９４３（モル比）のＹ軸タンタル酸リチウムの焼成原料４５００ｇと結晶塊５５００ｇの合計１００００ｇを入れてルツボを加熱し、溶融した。溶融後、シードホルダーに取り付けた３８度回転Ｙ軸タンタル酸リチウムの種結晶を融液中に浸漬し、シードホルダーを７ｒｐｍの回転数で回転させながら種結晶をゆっくり引き上げて、直径が１００ｍｍで、円柱状の胴部の長さが約１１０ｍｍのタンタル酸リチウム単結晶のサンプルを製造した。 Specifically, a crucible was heated and melted by putting a total of 10,000 g of 4500 g of Y-axis lithium tantalate firing material having a composition ratio of Li / Ta = 0.944 (molar ratio) and a crystal mass of 5500 g into the crucible. . After melting, the 38 ° rotated Y-axis lithium tantalate seed crystal attached to the seed holder was immersed in the melt, and the seed crystal was slowly pulled up while rotating the seed holder at a rotation speed of 7 rpm. A sample of lithium tantalate single crystal having a columnar body length of about 110 mm was manufactured.
上記タンタル酸リチウム結晶の製造を、繰返し２００回実施した。その時の歩留まりは８０％で、得られた全てのタンタル酸リチウム単結晶サンプル中には、ボイドなどの欠陥（インクルージョンの発生）は認められなかった。また、２００回使用した後のルツボの形状は図５に示した通りであり、横方向へのルツボの広がりが少ないことが確認された。 The production of the lithium tantalate crystal was repeated 200 times. The yield at that time was 80%, and defects such as voids (occurrence of inclusion) were not observed in all the obtained lithium tantalate single crystal samples. Further, the shape of the crucible after being used 200 times is as shown in FIG. 5, and it was confirmed that there was little spread of the crucible in the lateral direction.
実施例１で使用されたイリジウムルツボを、円筒部の板厚が２ｍｍ、底部の板厚が１．９ｍｍのルツボに替えた他は実施例１と同様にしてサンプルを製造した。その時の歩留まりは８２％で、得られた全てのタンタル酸リチウム単結晶サンプル中には、ボイドなどの欠陥（インクルージョンの発生）は認められなかった。また、２００回使用した後のルツボの形状は図６に示した通りであり、横方向へのルツボの広がりが少ないことが確認された。 Samples were produced in the same manner as in Example 1 except that the iridium crucible used in Example 1 was replaced with a crucible having a cylindrical thickness of 2 mm and a bottom thickness of 1.9 mm. The yield at that time was 82%, and no defects such as voids (occurrence of inclusion) were observed in all the obtained lithium tantalate single crystal samples. Moreover, the shape of the crucible after being used 200 times is as shown in FIG. 6, and it was confirmed that the crucible did not spread in the horizontal direction.
図２に示された形状で、寸法及び板厚が実施例1で用いたイリジウムルツボと同じイリジウムルツボを用いた他は、実施例１と同様にしてサンプルを２００回製造した。その時の歩留まりは８６％で、得られた全てのタンタル酸リチウムの単結晶サンプル中には、ボイドなどの欠陥（インクルージョンの発生）は認められなかった。また、２００回使用した後のルツボの形状は図７に示した通りであり、横方向へのルツボの広がりが少ないことが確認された。 A sample was manufactured 200 times in the same manner as in Example 1 except that the same iridium crucible as that used in Example 1 was used in the shape shown in FIG. The yield at that time was 86%, and no defects such as voids (occurrence of inclusion) were observed in all the obtained single crystal samples of lithium tantalate. Moreover, the shape of the crucible after being used 200 times is as shown in FIG. 7, and it was confirmed that there is little spread of the crucible in the lateral direction.
実施例１で使用されたイリジウムルツボを、円筒部の板厚が３ｍｍ、底部の板厚が２.２５ｍｍのルツボに替えた他は実施例１と同様にして２００回サンプルを製造した。その時の歩留まりは８１％で、得られた全てのタンタル酸リチウム単結晶サンプル中には、ボイドなどの欠陥（インクルージョンの発生）は認められなかった。また、２００回使用した後のルツボの形状は図６に示した通りであり、横方向へのルツボの広がりが少ないことが確認された。 Samples were produced 200 times in the same manner as in Example 1, except that the iridium crucible used in Example 1 was replaced with a crucible having a cylindrical thickness of 3 mm and a bottom thickness of 2.25 mm. The yield at that time was 81%, and no defects such as voids (occurrence of inclusion) were observed in all the obtained lithium tantalate single crystal samples. Moreover, the shape of the crucible after being used 200 times is as shown in FIG. 6, and it was confirmed that the crucible did not spread in the horizontal direction.
比較例１
円筒部及び底部の板厚が共に2ｍｍである点だけが実施例１で用いたルツボと異なるルツボを使用した他は、実施例１と同様にして２００回サンプルを製造した。この時の歩留まりは７０％で、ルツボの使用回数が１５０回以降となったときに得られた全てのタンタル酸リチウム単結晶のサンプル中には、ボイドなどの欠陥（インクルージョンの発生）が認められた。また、２００回使用した後のルツボの形状は図８に示した通りであり、横方向へのルツボの広がりが大きいことが確認された。
Comparative Example 1
Samples were manufactured 200 times in the same manner as in Example 1 except that a crucible different from the crucible used in Example 1 was used only in that the thickness of both the cylindrical part and the bottom part was 2 mm. At this time, the yield was 70%, and all the lithium tantalate single crystal samples obtained when the crucible was used after 150 times showed defects such as voids (occurrence of inclusion). It was. Moreover, the shape of the crucible after being used 200 times is as shown in FIG. 8, and it was confirmed that the crucible spreads in the horizontal direction.
比較例２
円筒部の板厚が2ｍｍで底部の板厚が1ｍｍの、図１に示した形状のイリジウムルツボを使用した他は実施例１と同様にして、２００回サンプルを製造することを試みた。この時の歩留まりは８２％であり、得られた全てのタンタル酸リチウム単結晶サンプル中に、ボイドなどの欠陥（インクルージョンの発生）は認められなかったが、１６０回使用後には湯漏れが発生した（使用後のルツボ形状は図５と同様の形状であった）ので、それ以上同じルツボを使用して製造することはできなかった。
Comparative Example 2
An attempt was made to manufacture a sample 200 times in the same manner as in Example 1 except that an iridium crucible having the shape shown in FIG. 1 having a cylindrical thickness of 2 mm and a bottom thickness of 1 mm was used. The yield at this time was 82%, and no defects such as voids (occurrence of inclusion) were observed in all the obtained lithium tantalate single crystal samples, but after 160 times of use, hot water leaked. (The crucible shape after use was the same as that shown in FIG. 5), so it could not be produced using the same crucible.
比較例３
円筒部の板厚が１ｍｍで底部の板厚が０.７５ｍｍの、図１に示した形状のイリジウムルツボを使用した他は実施例１と同様にして、２００回サンプルを製造することを試みた。しかしながら、ルツボの板厚が薄いため結晶が溶融又は固化する際の応力に耐えられず、板厚２ｍｍ又は３ｍｍの時と比べるとルツボが加速的に変形し、３０回使用時には湯漏れが発生した。
Comparative Example 3
An attempt was made to manufacture samples 200 times in the same manner as in Example 1 except that an iridium crucible having the shape shown in FIG. 1 having a cylindrical thickness of 1 mm and a bottom thickness of 0.75 mm was used. . However, because the crucible plate is thin, it cannot withstand the stress when the crystal melts or solidifies, and the crucible deforms at an accelerated rate compared to when the plate thickness is 2 mm or 3 mm. .
実施例１、２及び比較例１、２の結果から、側面のイリジウムの厚みと底面のイリジウムの厚みをそれぞれｔ、ｔ’とした場合、ｔ’は0.5ｔ≦ｔ’≦0.95ｔであることが好ましい。
又、比較例３の結果から、側面のイリジウムの厚みが1ｍｍよりも小さいとルツボの変形が加速的に進み、湯漏れにつながることが判明した。又、実施例３で使用したルツボの底部の板厚が１．５ｍｍの場合も鑑みると、ルツボ側面の板厚ｔはｔ≧1.5ｍｍであることが好ましい。
一方、実施例３、４の比較から、ルツボ側面の板厚を厚くすればルツボの変形を低減する効果はあるものの、ルツボ側面の板厚を１．５ｍｍ以上としても歩留り等に大きな差は見られないことが判明した。これらの事実から、ｔ≧1.5ｍｍであれば良いことが分かるが、ルツボの材質が非常に高価なイリジウムであるため、10.0mmを越えると、価格競争力において不利となる。
From the results of Examples 1 and 2 and Comparative Examples 1 and 2, assuming that the thickness of the iridium on the side surface and the thickness of the iridium on the bottom surface are t and t ′, respectively, t ′ is 0.5t ≦ t ′ ≦ 0.95t. Is preferred.
Further, from the result of Comparative Example 3, it was found that when the thickness of the iridium on the side surface is smaller than 1 mm, the crucible deforms at an accelerated rate and leads to hot water leakage. In view of the case where the thickness of the bottom portion of the crucible used in Example 3 is 1.5 mm, the thickness t of the side surface of the crucible is preferably t ≧ 1.5 mm.
On the other hand, from the comparison of Examples 3 and 4, although increasing the thickness of the crucible side surface has the effect of reducing the deformation of the crucible, there is no significant difference in yield even when the thickness of the crucible side surface is 1.5 mm or more. It turned out not to be. From these facts, it can be understood that t ≧ 1.5 mm, but since the material of the crucible is very expensive iridium, if it exceeds 10.0 mm, it is disadvantageous in price competitiveness.
本発明によれば、異方性のあるタンタル酸リチウムの単結晶を、低コストでボイドのような欠陥なしに製造することが可能であるので、本発明は産業上極めて有意義である。 According to the present invention, since an anisotropic lithium tantalate single crystal can be produced at low cost and without defects such as voids, the present invention is extremely significant in industry.
２１ ルツボ
２２ アルミナ台
２３ ルツボ台
２４ 断熱材
２５ 耐火性アルミナ
２６ リフレクター
２７ アフターヒーター
２８ アフターヒーター蓋
２９ 加熱コイル
３０ 融液
３１ シードホルダー
３２ 種結晶
３５ タンタル酸リチウム単結晶
３５ａ タンタル酸リチウム単結晶の円錐状の肩部
３５ｂ タンタル酸リチウム単結晶の円柱状の胴部
21 crucible 22 alumina base 23 crucible base 24 heat insulating material 25 refractory alumina 26 reflector 27 after heater 28 after heater lid 29 heating coil 30 melt 31 seed holder 32 seed crystal 35 lithium tantalate single crystal 35a cone of lithium tantalate single crystal Shoulder 35b cylindrical body of lithium tantalate single crystal
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