JP3707750B2 - Method for producing calcium fluoride crystals - Google Patents
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- JP3707750B2 JP3707750B2 JP13651596A JP13651596A JP3707750B2 JP 3707750 B2 JP3707750 B2 JP 3707750B2 JP 13651596 A JP13651596 A JP 13651596A JP 13651596 A JP13651596 A JP 13651596A JP 3707750 B2 JP3707750 B2 JP 3707750B2
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【０００１】
【発明の属する技術分野】
本発明は、フッ化カルシウム単結晶の製造方法に関するものである。
【０００２】
【従来の技術】
従来、光学系で使用されるフッ化カルシウム単結晶（ＣａＦ2）は、主にブリッジマン法（ストックバーガー法またはルツボ降下法と呼ばれる）で製造されている。
可視ないし赤外域で使用されるフッ化カルシウム単結晶の原料にはおもに天然の蛍石あるいはそれを用いた合成蛍石の粉砕品とフッ素化剤であるスカベンジャーとを所定量混合したものを使用する。しかし、紫外ないし真空紫外域で使用されるフッ化カルシウム単結晶の育成を目的とする場合は、天然の蛍石あるいは合成蛍石の粉砕品を原料とすると、紫外ないし真空紫外域に吸収があるため使用できない。 従って、化学合成で作られたフッ化カルシウム高純度粉末原料とスカベンジャーとを混合して使用することが一般的となっている。原料は粉末の形で使用しても良いが、嵩比重の関係から熔融したときの目減りが激しいので、カレットを使用することが一般的である。カレットは、上記の高純度原料粉末を一度熔融して得られた塊を粉砕して得られる。
【０００３】
育成装置の中に上記原料を充填した育成用ルツボを置き、育成装置内を１０-5〜１０-6Ｔｏｒｒの真空雰囲気に保つ。次に育成装置内の温度を徐々に上げ原料とスカベンジャーを反応させた後、さらにフッ化カルシウムの融点以上（１３７０℃〜１４５０℃）まで徐々に昇温し、過剰なスカベンジャーと反応生成物とを揮発させると共に、原料を熔融する。結晶成長段階では、０．１〜５ｍｍ／Ｈ程度の速度で育成用ルツボを引き下げることにより、ルツボの下部から徐々に結晶化させフッ化カルシウム単結晶を得る。
【０００４】
【発明が解決しようとする課題】
上記の様に粉末の原料を用いてブリッジマン法でフッ化カルシウム単結晶を製造する場合、粉末原料は融解および結晶化すると体積が粉末状態のほぼ１／３に減少してしまうため、半融処理あるいはカレット等の前処理をした前処理品の原料で育成用ルツボを充填後、フッ化カルシウム単結晶を育成していた。しかし、半融処理を行うと育成炉の効率的な運用ができず、また、カレットを用いた場合でも不純物の混入による原料純度の低下、作業効率が悪い等の問題があった。
【０００５】
したがって、従来の半融処理あるいはカレット等の原料を用いたフッ化カルシウム単結晶の育成では、高純度なフッ化カルシウム単結晶を効率よく得ることができなかった。
本発明は上記の問題点に鑑みてなされたものである。すなわち、高純度なフッ化カルシウム単結晶を効率よく得ることが可能な、フッ化カルシウム単結晶の製造方法を提供することを目的とするものである。
【０００６】
【課題を解決するための手段】
本発明者らは、スカベンジャーにより生成した酸化物、揮発性の不純物および過剰なスカベンジャーが育成装置の内部を著しく汚染し、育成装置の温調機構に支障をきたすだけでなく、残存することで育成したフッ化カルシウム単結晶に吸収ピークを生成し、内部品質に悪影響を及ぼす原因になると考えた。
【０００７】
また、大量のフッ化カルシウムとスカベンジャーとを混合し、育成用ルツボに充填すると原料とスカベンジャーの粒度の違いにより、混合が不十分になり、偏析が起こり易く、フッ化カルシウム単結晶の内部品質の低下をもたらしていた。
そこで、本発明では、育成の前段階でスカベンジャーを用いた前処理を行い、
高純度の前処理品を得る。これにより、育成装置の汚染が防止され、不純物が少なく高純度なフッ化カルシウム単結晶が製造できる。
【０００８】
また、この前処理に使用する前処理用ルツボを多段階ルツボとすることで、一度に複数の前処理品の製造が可能となる。
本発明により育成されたフッ化カルシウム単結晶は、高純度であり、レンズ、窓材、プリズム等の光学系に有用である。
【０００９】
【発明の実施の形態】
本発明の前処理は、育成ルツボに充填する際の充填率をあげる他に、原料を高純度化し、フッ化カルシウム単結晶の内部品質を向上させる目的で行う。
前処理用の電気炉装置（図３、但し、真空排気系を省略した概念図）内に、高純度フッ化カルシウム粉末原料（原料）とスカベンジャーとを混合して充填した前処理用ルツボを置き、装置内を脱酸素雰囲気にして熔融する。このとき、酸化物、揮発性の不純物（反応生成物）を除去するために1０-5〜１０-6Ｔｏｒｒの真空雰囲気に保つ。装置温度は徐々に上げていき、原料とスカベンジャーの反応する温度、すなわちスカベンジャーの分解温度からその温度＋１００℃まで上げ、例えばフッ化鉛（ＰｂＦ2）を用いた場合は８００℃〜９００℃で一旦保持し、さらに原料の融点以上の温度１３７０℃〜１４５０℃まで昇温する。そこで、過剰なスカベンジャーと反応生成物とを揮発させると共に原料を熔融した後、徐々に温度を降下させ熔融物を固化し、前処理品を得るものである。
【００１０】
この様な熔融スケジュールとすることで、高純度な前処理品を得ることができる。また、原料の前処理を専用の前処理装置で行うことにより、前処理に伴って発生する反応生成物や過剰なスカベンジャーが育成装置の内部を汚染することを防げるため、育成装置の温調機構に支障をきたすことがなく、高純度なフッ化カルシウム単結晶を製造することができる。さらに、育成装置との分業が可能となり、育成装置の効率的な運用が可能になる。
【００１１】
なお、スカベンジャーはテフロン、フッ化鉛、フッ化コバルト、フッ化マンガン等が考えられ、保持時間および熔融時間は、混合物の容積に合わせて任意に設定する。これらスカベンジャーの混合比は、化学反応性を加味し、原料のフッ化カルシウムに対して０．１〜５．０ｍｏｌ％が好ましい。
また、前処理用ルツボを多段階ルツボとすることで、効率よく前処理品を得ることができる。ところが、気密性を高くかつ多段階とすると、各段で生成した反応生成物の除去が効率よくできず、前処理品の内部品質の低下をもたらす。さらに、熱伝導の関係から前処理用ルツボの上段ほど温度が高く、フッ素が欠乏し、下段ほど未反応なスカベンジャーが残存する問題も生じ、結果として高品質な前処理品が得られなかった。
【００１２】
そこで、本発明らは原料とスカベンジャーの反応を妨げず、各段で生成した反応生成物および過剰なスカベンジャーを除去できる程度の気密性の多段階ルツボを検討した結果、各段をねじ止めで固定することが有用であることを実験的に見出した。また、各段の固定の気密性が高い場合は、各ルツボにスリットを設けて、気密性を調整する。
【００１３】
本発明の多段階ルツボを用いた熔融は前記熔融スケジュールで行うが、反応を均等に促進させるために上段と下段の温度差が８０℃以下となるようにヒートバランスをモニターしながら行う。これにより、各段における前処理品がほぼ等しく、高品質・高均質になる。
前処理用ルツボの形状は、育成ルツボへの充填率が高くなるように、特に底の形状を加味し、工夫する。多段階ルツボにおいては、最下段を育成ルツボの底の形状と一致させる。
【００１４】
例えば、軸芯を共通にして上下方向に積み重ねられた上部開放の複数のルツボから構成し、下段のルツボに積み重ねられる上段のルツボはその底部を下段のルツボの開放上端部にねじ込んで取り付ける構造を有し、最上段のルツボには開放上端部に蓋をねじ込んで取り付け、最下段のルツボは育成用ルツボと同一形状の角度を有するコーン形状をした構造とする。
【００１５】
ただし、熔融に至る昇温の際、育成ルツボで前処理品が熱膨張し、育成ルツボを破損する恐れがあるのでこれを考慮し、前処理用ルツボの内容積比は育成ルツボより小さく、好ましくは９０％程度とする。
なお、前処理用ルツボの材質は育成ルツボと同様にフッ化カルシウムと反応せず、かつ濡れ性の低い物であれば黒鉛に限定することなく、窒化ホウ素製のものでも可能であることは言うまでもなく、各ルツボの積み重ねる数は必要量に応じて選択する。
【００１６】
以上の様に、本発明の多段階ルツボを用いて前処理品を作製すると、フッ化カルシウム粉末とスカベンジャーとを一度に大量に混合せずに済み、少量ずつ十分に混合が行えるため、各段ごとに反応の局在化がない高品質・高均質な前処理品が得られる。また、得られる一枚一枚の前処理品を軽く、扱い易くすることができ、これを育成用ルツボに充填することにより、原料の充填効率を格段に上げ、口径および高さの大きいフッ化カルシウム単結晶を製造することができる。
【００１７】
【実施例】
［実施例１］
図１は本発明に係る黒鉛製の多段階ルツボの実施例を示す。図面によればこの発明に係る前処理用ルツボ１は多段階ルツボであり、複数の上部開放の黒鉛製のルツボ２を軸方向に重ね合わせる構造となっている。各ルツボ２の底部には凸部２ａが設けられており、この凸部を各ルツボ２の上部開放端部２ｂにねじ込みにより積み重ねられることによって、合計６個のルツボより多段階ルツボが構成されている。そして、その最上段のルツボには下側に凸部３ａを突設した蓋３がねじ込みにより取り付けられている。また、その最下段のルツボ４の内底部は、予め育成用ルツボの底のコーン部形状と同一の角度形状に加工されている。さらに、育成用ルツボへの充填の作業性および前処理品の熱膨張を考慮して、各ルツボ２の内径は育成用ルツボの内径より２０ｍｍ小さい口径でφ２３０ｍｍとなっている。
【００１８】
次に、前記多段階ルツボを用いて、前処理品を作製する。図２は図１の多段階ルツボを用いて作製した前処理品の形状である。
高純度フッ化カルシウム粉末とスカベンジャー（ＰｂＦ2）、１．０ｍｏｌ％との混合原料をそれぞれ８から１０ｋｇづつ各ルツボ内に収容させ、順に積み重ね、最上段には蓋をする。この多段階ルツボをルツボ支持台上に設置して電気炉装置内に収納した。この電気炉装置は、各ルツボが同一の温度になるよう、内部に黒鉛製の発熱体を設置したものを使用した。複数の黒鉛製発熱体を軸方向に多段階に設置して、装置内部の均熱長を長くした。
【００１９】
前処理は電気炉装置内部を１０-5〜１０-6Ｔｏｒｒの真空に排気した後、装置温度を徐々に上げ原料とスカベンジャーの反応温度８００℃〜９００℃で８時間保持後、さらに原料の融点以上１３７０℃〜１４５０℃まで徐々に昇温し、過剰なスカベンジャーと反応生成物とを揮発させると共に原料を８時間、熔融して行った。ただし、熔融温度が高すぎると原料の揮発が激しくなるばかりか、フッ素が選択的に揮発してしまうので注意し、最上段と最下段の温度差が８０℃以下になるように熱電対でモニターしながら黒鉛製発熱体を制御し、熔融した。次に、徐々に温度を降下させ熔融物を固化し、フッ化カルシウム単結晶育成用の前処理品を得た。
【００２０】
得られた前処理品は、無色透明で泡などの異物はなく、偏析が認められず高均質で、残留鉛濃度をＩＣＰ−ＡＥＳで分析した結果、全て検出限界である２０ｐｐｍ以下の高品質であった。また、ルツボの位置による差もなかった。
なお、本実施例における前処理品の形状は、下部に段差を設けることにより持ち運びの際の作業性を向上させた。
［実施例２］
実施例１で得られた前処理品を用いてフッ化カルシウム単結晶の製造を行った。
【００２１】
得られた６枚の前処理品をそのまま育成用ルツボに充填し、それを育成装置の中に置き、育成装置内を１０-5〜１０-6Ｔｏｒｒの真空雰囲気に保つ。フッ化カルシウム多結晶の融点以上１３７０℃〜１４５０℃まで徐々に昇温し、前処理品を熔融する。続いて０．１〜５ｍｍ／Ｈ程度の速度で育成用ルツボを引き下げることにより、ルツボの下部から徐々に結晶化させフッ化カルシウム単結晶を製造した。
【００２２】
得られたフッ化カルシウム単結晶は不純物が少なく、また、体積変化が小さいために、充填した前処理品に相当する大きさの高純度なフッ化カルシウム単結晶を育成することができた。
また、熔融の際の反応生成物が発生しないため、育成装置内の汚染が防止され、温調機構も正常に機能し、消耗品の寿命が延びた。
［比較例］
高純度フッ化カルシウム粉末とスカベンジャー（ＰｂＦ2）、１．０ｍｏｌ％との混合原料を育成用ルツボに直接収容させた場合、その充填量はルツボいっぱいにいれた場合でも２０ｋｇであった。このルツボを育成装置内に収納させた。以下、実施例１と同様の熱処理を行い、そのまま引き続いて実施例２に示したようなフッ化カルシウム単結晶の製造を行った。
【００２３】
この結果得られたフッ化カルシウム単結晶は、前処理品を用いて育成した場合に比べて、１／３の重量しかなく、大きな単結晶が得られないため生産性が著しく悪かった。また、育成装置内が揮発したスカベンジャーや反応生成物によって汚染されてしまった。この汚染のため、装置の温調機構に支障をきたした。
【００２４】
【発明の効果】
本発明によれば、育成の前段階でスカベンジャーを用いた前処理を行い、高純度の前処理品を用いることにより、育成装置の汚染が防止され、不純物が少なく高純度なフッ化カルシウム単結晶が製造できる。
また、多段階ルツボを用いて良質なフッ化カルシウム育成用前処理品を作製することにより、育成用ルツボの原料充填率を上げるのみならず、育成装置の汚染を防止し、育成装置の効率的な運用が可能となる。
【図面の簡単な説明】
【図１】 多段階ルツボの断面図
【図２】 前処理品の断面図
【図３】 電気炉装置の概念図
【符号の説明】
１ 前処理用ルツボ
２ ルツボ
３ 蓋
４ 最下段のルツボ
５ ヒーター
６ ルツボ支持台
７ 断熱材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a calcium fluoride single crystal.
[0002]
[Prior art]
Conventionally, calcium fluoride single crystals (CaF 2 ) used in optical systems are mainly manufactured by the Bridgman method (referred to as the stock burger method or the crucible descent method).
The raw material of calcium fluoride single crystal used in the visible or infrared region is mainly a mixture of natural fluorite or a synthetic fluorite pulverized product and a scavenger as a fluorinating agent. . However, for the purpose of growing calcium fluoride single crystals used in the ultraviolet or vacuum ultraviolet region, if natural fluorite or synthetic fluorite pulverized products are used as raw materials, there is absorption in the ultraviolet or vacuum ultraviolet region. Therefore, it cannot be used. Therefore, it is common to use a mixture of a calcium fluoride high-purity powder material made by chemical synthesis and a scavenger. The raw material may be used in the form of a powder, but cullet is generally used because it is drastically reduced when melted due to the bulk density. The cullet is obtained by pulverizing a lump obtained by once melting the high-purity raw material powder.
[0003]
A growth crucible filled with the above raw material is placed in the growth apparatus, and the inside of the growth apparatus is maintained in a vacuum atmosphere of 10 −5 to 10 −6 Torr. Next, after gradually raising the temperature in the growing apparatus and reacting the raw material and the scavenger, the temperature is gradually raised to the melting point of calcium fluoride (1370 ° C. to 1450 ° C.), and the excess scavenger and reaction product are removed. While volatilizing, the raw material is melted. In the crystal growth stage, the growing crucible is pulled down at a speed of about 0.1 to 5 mm / H to gradually crystallize from the lower part of the crucible to obtain a calcium fluoride single crystal.
[0004]
[Problems to be solved by the invention]
When a calcium fluoride single crystal is produced by a Bridgman method using a powder raw material as described above, the volume of the powder raw material is reduced to about 1/3 of the powder state when melted and crystallized. A calcium fluoride single crystal was grown after filling a growth crucible with a raw material of a pretreated product that had been treated or pretreated such as cullet. However, when semi-melting treatment is performed, the growth furnace cannot be operated efficiently, and even when cullet is used, there are problems such as a decrease in raw material purity due to contamination of impurities and poor work efficiency.
[0005]
Therefore, in conventional growth of calcium fluoride single crystals using raw materials such as semi-melting or cullet, high-purity calcium fluoride single crystals could not be obtained efficiently.
The present invention has been made in view of the above problems. That is, an object of the present invention is to provide a method for producing a calcium fluoride single crystal capable of efficiently obtaining a high-purity calcium fluoride single crystal.
[0006]
[Means for Solving the Problems]
The present inventors have developed not only the oxide generated by the scavenger, volatile impurities and excessive scavenger significantly contaminated the inside of the growth apparatus, but also hindering the temperature control mechanism of the growth apparatus, and the growth is caused by remaining. It was thought that an absorption peak was generated in the obtained calcium fluoride single crystal, and the internal quality was adversely affected.
[0007]
Also, when a large amount of calcium fluoride and scavenger are mixed and filled in the growing crucible, mixing is insufficient due to the difference in the particle size of the raw material and the scavenger, and segregation is likely to occur. It was causing a decline.
Therefore, in the present invention, pretreatment using a scavenger is performed at the stage before the growth,
A high-purity pretreatment product is obtained. Thereby, contamination of the growing apparatus is prevented, and a high-purity calcium fluoride single crystal with few impurities can be produced.
[0008]
Further, by making the pretreatment crucible used for the pretreatment a multi-stage crucible, a plurality of pretreatment products can be manufactured at a time.
The calcium fluoride single crystal grown by the present invention has high purity and is useful for optical systems such as lenses, window materials, and prisms.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The pretreatment of the present invention is carried out for the purpose of increasing the filling rate when filling the growing crucible and improving the internal quality of the calcium fluoride single crystal by increasing the purity of the raw material.
A pretreatment crucible filled with a mixture of high-purity calcium fluoride powder material (raw material) and a scavenger is placed in the pretreatment electric furnace (Fig. 3, but the conceptual diagram omitting the vacuum exhaust system). The inside of the apparatus is melted in a deoxygenated atmosphere. At this time, a vacuum atmosphere of 10 −5 to 10 −6 Torr is maintained in order to remove oxides and volatile impurities (reaction products). The temperature of the apparatus is gradually increased, and the temperature at which the raw material and the scavenger react, that is, the scavenger decomposition temperature is raised to the temperature + 100 ° C. For example, when lead fluoride (PbF 2 ) is used, And the temperature is raised to 1370 ° C. to 1450 ° C. above the melting point of the raw material. Therefore, after volatilizing excess scavengers and reaction products and melting the raw material, the temperature is gradually lowered to solidify the melt to obtain a pre-processed product.
[0010]
By setting it as such a melting schedule, a highly purified pre-processed product can be obtained. In addition, by performing the pretreatment of the raw material with a dedicated pretreatment device, it is possible to prevent reaction products and excessive scavengers generated during the pretreatment from contaminating the inside of the growth device. Therefore, it is possible to produce a high-purity calcium fluoride single crystal. Furthermore, division of labor with the training apparatus becomes possible, and efficient operation of the training apparatus becomes possible.
[0011]
The scavenger may be Teflon, lead fluoride, cobalt fluoride, manganese fluoride, etc., and the holding time and melting time are arbitrarily set according to the volume of the mixture. The mixing ratio of these scavengers is preferably 0.1 to 5.0 mol% with respect to the raw material calcium fluoride in consideration of chemical reactivity.
Moreover, a pre-processed product can be obtained efficiently by using a multi-stage crucible as the pre-processing crucible. However, if the airtightness is high and multistage, the reaction product generated in each stage cannot be efficiently removed, resulting in a decrease in the internal quality of the pretreated product. In addition, due to heat conduction, the upper stage of the pretreatment crucible has a higher temperature, lack of fluorine, and the lower stage has a problem that unreacted scavengers remain, resulting in failure to obtain a high-quality pretreatment product.
[0012]
Therefore, the present inventors investigated a multi-stage crucible that is tight enough to remove reaction products and excess scavengers generated at each stage without interfering with the reaction between the raw material and the scavenger, and fixed each stage with screws. It was found experimentally that it is useful to do. Further, when the airtightness of each stage is high, a slit is provided in each crucible to adjust the airtightness.
[0013]
Melting using the multi-stage crucible of the present invention is carried out according to the above-described melting schedule, and is performed while monitoring the heat balance so that the temperature difference between the upper and lower stages is 80 ° C. or less in order to promote the reaction evenly. Thereby, the pre-processed product in each stage is almost equal, and it becomes high quality and high homogeneity.
The shape of the pretreatment crucible is devised in consideration of the shape of the bottom in particular so that the filling rate into the growing crucible is increased. In a multi-stage crucible, the bottom is matched with the shape of the bottom of the growing crucible.
[0014]
For example, it is composed of a plurality of upper open crucibles stacked in the vertical direction with a common shaft core, and the upper crucible stacked on the lower crucible is attached by screwing the bottom part to the open upper end of the lower crucible. The uppermost crucible has a structure in which a lid is screwed onto the open upper end, and the lowermost crucible has a cone shape having the same angle as the growing crucible.
[0015]
However, when the temperature rises up to melting, the pre-treated product may thermally expand with the growing crucible, and the growing crucible may be damaged. Therefore, the internal volume ratio of the pre-processing crucible is smaller than that of the growing crucible. Is about 90%.
Needless to say, the material of the pretreatment crucible is not limited to graphite as long as it does not react with calcium fluoride and has low wettability as in the case of the growing crucible. The number of crucibles to be stacked is selected according to the required amount.
[0016]
As described above, when preparing a pre-processed product using the multi-stage crucible of the present invention, it is not necessary to mix a large amount of calcium fluoride powder and scavenger at a time, and each stage can be sufficiently mixed. A high-quality, high-homogeneous pre-processed product with no localized reaction can be obtained. In addition, each pre-processed product obtained can be made light and easy to handle, and by filling this into a growing crucible, the raw material filling efficiency can be remarkably increased, and the fluorination has a large diameter and height. A calcium single crystal can be produced.
[0017]
【Example】
[Example 1]
FIG. 1 shows an embodiment of a graphite multi-stage crucible according to the present invention. According to the drawings, the pretreatment crucible 1 according to the present invention is a multi-stage crucible, and has a structure in which a plurality of open graphite crucibles 2 are overlapped in the axial direction. A convex portion 2a is provided at the bottom of each crucible 2, and a multi-stage crucible is constituted by a total of six crucibles by stacking this convex portion on the upper open end 2b of each crucible 2 by screwing. Yes. And the lid | cover 3 which protruded the convex part 3a on the lower side is attached to the uppermost crucible by screwing. Further, the inner bottom portion of the lowermost crucible 4 is processed in advance into the same angular shape as the cone portion shape of the bottom of the growing crucible. Further, considering the workability of filling the growing crucible and the thermal expansion of the pre-processed product, the inner diameter of each crucible 2 is φ230 mm, which is 20 mm smaller than the inner diameter of the growing crucible.
[0018]
Next, a pre-processed product is produced using the multistage crucible. FIG. 2 shows the shape of a pre-processed product produced using the multistage crucible of FIG.
A mixed raw material of high-purity calcium fluoride powder, scavenger (PbF 2 ), and 1.0 mol% is accommodated in each crucible in an amount of 8 to 10 kg, stacked in order, and the top is covered. The multistage crucible was placed on a crucible support and stored in an electric furnace apparatus. The electric furnace apparatus used was a graphite heating element installed inside so that each crucible had the same temperature. A plurality of graphite heating elements were installed in multiple stages in the axial direction to increase the soaking length inside the apparatus.
[0019]
The pretreatment is performed by evacuating the interior of the electric furnace apparatus to a vacuum of 10 −5 to 10 −6 Torr, then gradually increasing the apparatus temperature and holding the reaction temperature between the raw material and the scavenger at 800 ° C. to 900 ° C. for 8 hours, and then the melting point of the raw material The temperature was gradually raised to 1370 ° C. to 1450 ° C. to volatilize excess scavengers and reaction products, and the raw materials were melted for 8 hours. However, if the melting temperature is too high, not only will the raw material volatilize, but fluorine will also volatilize selectively, and monitor with a thermocouple so that the temperature difference between the top and bottom stages is 80 ° C or less. The graphite heating element was controlled and melted. Next, the temperature was gradually lowered to solidify the melt, and a pretreated product for growing a calcium fluoride single crystal was obtained.
[0020]
The obtained pretreated product is colorless and transparent, free from foreign matters such as bubbles, is highly homogeneous without segregation, and analyzed by ICP-AES for residual lead concentration. there were. There was no difference depending on the position of the crucible.
In addition, the shape of the pre-processed product in a present Example improved the workability | operativity at the time of carrying by providing a level | step difference in the lower part.
[Example 2]
A calcium fluoride single crystal was produced using the pretreated product obtained in Example 1.
[0021]
The obtained 6 pre-treated products are filled in a growing crucible as it is, placed in a growing apparatus, and the inside of the growing apparatus is maintained in a vacuum atmosphere of 10 −5 to 10 −6 Torr. The pretreatment product is melted by gradually raising the temperature from the melting point of calcium fluoride polycrystal to 1370 ° C. to 1450 ° C. Subsequently, the growing crucible was pulled down at a speed of about 0.1 to 5 mm / H to gradually crystallize from the lower part of the crucible to produce a calcium fluoride single crystal.
[0022]
Since the obtained calcium fluoride single crystal has few impurities and a small volume change, it was possible to grow a high-purity calcium fluoride single crystal having a size corresponding to that of the filled pretreatment product.
Further, since no reaction product is generated during melting, contamination in the growing apparatus is prevented, the temperature control mechanism functions normally, and the life of the consumables is extended.
[Comparative example]
When a mixed raw material of high-purity calcium fluoride powder, scavenger (PbF2), and 1.0 mol% was directly stored in the growing crucible, the filling amount was 20 kg even when the crucible was filled. This crucible was housed in the growing apparatus. Thereafter, the same heat treatment as in Example 1 was performed, and the calcium fluoride single crystal as shown in Example 2 was subsequently produced as it was.
[0023]
As a result, the calcium fluoride single crystal obtained had a weight of only 1/3 compared with the case where it was grown using a pretreated product, and a large single crystal could not be obtained. Moreover, the inside of the growing apparatus has been contaminated by volatilized scavengers and reaction products. This contamination has hindered the temperature control mechanism of the device.
[0024]
【The invention's effect】
According to the present invention, pretreatment using a scavenger is performed in a pre-growth stage, and the use of a high-purity pretreatment product prevents contamination of the growth apparatus, and high purity calcium fluoride single crystal with less impurities Can be manufactured.
In addition, by preparing a high quality pretreatment product for growing calcium fluoride using a multi-stage crucible, not only the raw material filling rate of the growing crucible is increased, but also the contamination of the growing apparatus is prevented and the growing apparatus is efficiently used. Operation becomes possible.
[Brief description of the drawings]
[Fig. 1] Cross-sectional view of a multi-stage crucible [Fig. 2] Cross-sectional view of a pre-processed product [Fig. 3] Conceptual diagram of an electric furnace apparatus [Explanation of symbols]
1 crucible for pretreatment 2
Claims (5)
真空加熱炉内で、育成用ルツボに入れた前記前処理品を、フッ化カルシウムの融点以上の温度で熔融した後、前記育成用ルツボを引き下げ、前記前処理品を前記育成用ルツボの下部から徐々に結晶化させてフッ化カルシウム結晶を得る育成工程と、
を含むフッ化カルシウム単結晶の製造方法。In a vacuum heating furnace, after deoxidizing the mixture of calcium fluoride raw material and scavenger in a multi-stage crucible in which a plurality of crucibles are combined up and down, the reactant is melted at a temperature above the melting point of calcium fluoride. A pre-treatment step of gradually crystallization to obtain a pre-treatment product,
In the vacuum heating furnace, after melting the pretreatment product placed in the growth crucible at a temperature equal to or higher than the melting point of calcium fluoride, the growth crucible is pulled down, and the pretreatment product is removed from the lower part of the growth crucible. A growth step of gradually crystallization to obtain calcium fluoride crystals;
The manufacturing method of the calcium fluoride single crystal containing this.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13651596A JP3707750B2 (en) | 1996-05-30 | 1996-05-30 | Method for producing calcium fluoride crystals |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13651596A JP3707750B2 (en) | 1996-05-30 | 1996-05-30 | Method for producing calcium fluoride crystals |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09315893A JPH09315893A (en) | 1997-12-09 |
| JP3707750B2 true JP3707750B2 (en) | 2005-10-19 |
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| JP13651596A Expired - Lifetime JP3707750B2 (en) | 1996-05-30 | 1996-05-30 | Method for producing calcium fluoride crystals |
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Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH10260349A (en) * | 1997-03-18 | 1998-09-29 | Nikon Corp | Image formation optical system for ultraviolet-ray laser |
| JP3337638B2 (en) * | 1997-03-31 | 2002-10-21 | キヤノン株式会社 | Method for producing fluoride crystal and method for producing optical component |
| JP4154744B2 (en) * | 1997-12-01 | 2008-09-24 | 株式会社ニコン | Calcium fluoride crystal production method and raw material treatment method |
| US5978070A (en) * | 1998-02-19 | 1999-11-02 | Nikon Corporation | Projection exposure apparatus |
| JP3631063B2 (en) * | 1998-10-21 | 2005-03-23 | キヤノン株式会社 | Method for purifying fluoride and method for producing fluoride crystal |
| US6537372B1 (en) | 1999-06-29 | 2003-03-25 | American Crystal Technologies, Inc. | Heater arrangement for crystal growth furnace |
| US6602345B1 (en) | 1999-06-29 | 2003-08-05 | American Crystal Technologies, Inc., | Heater arrangement for crystal growth furnace |
| EP1154046B1 (en) | 2000-05-09 | 2011-12-28 | Hellma Materials GmbH & Co. KG | Fluoride crystalline optical lithography lens element blank |
| WO2002031232A1 (en) | 2000-10-13 | 2002-04-18 | Corning Incorporated | Method and device for producing optical fluoride crystals |
| JP4524527B2 (en) * | 2001-01-31 | 2010-08-18 | 三菱マテリアル株式会社 | Method for producing Langasite single crystal |
| US6605149B2 (en) * | 2002-01-11 | 2003-08-12 | Hemlock Semiconductor Corporation | Method of stacking polycrystalline silicon in process for single crystal production |
| JP2003238152A (en) | 2002-02-19 | 2003-08-27 | Canon Inc | Method for making crystal |
| JP4694447B2 (en) * | 2006-09-06 | 2011-06-08 | 株式会社トクヤマ | Raw material pretreatment crucible |
| JP5191153B2 (en) * | 2007-03-26 | 2013-04-24 | 株式会社トクヤマ | Regeneration method of heat insulating material used for heating and melting furnace for metal fluoride |
| KR101469502B1 (en) * | 2013-07-16 | 2014-12-05 | 한국세라믹기술원 | High temperature chemical vapor deposition apparatus for growing single crystal |
| CN107723787A (en) * | 2017-10-20 | 2018-02-23 | 苏州奥趋光电技术有限公司 | A kind of multisection type crucible device for aluminum-nitride single crystal growth |
| KR102233907B1 (en) * | 2019-09-18 | 2021-03-30 | 주식회사 에스엠랩 | Crucible and crucible assembly for preparing cathode active material |
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1996
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