JP3914269B2 - Rare earth silicate single crystal - Google Patents
Rare earth silicate single crystal Download PDFInfo
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- JP3914269B2 JP3914269B2 JP5967394A JP5967394A JP3914269B2 JP 3914269 B2 JP3914269 B2 JP 3914269B2 JP 5967394 A JP5967394 A JP 5967394A JP 5967394 A JP5967394 A JP 5967394A JP 3914269 B2 JP3914269 B2 JP 3914269B2
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- plane
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- rare earth
- earth silicate
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【０００１】
【産業上の利用分野】
本発明は、シンチレータ等に用いられる希土類珪酸塩単結晶に関する。
【０００２】
【従来の技術】
珪酸ガドリニウム単結晶等の希土類珪酸塩単結晶は、シンチレータ、蛍光体等として広く用いられている。
この単斜晶系に属する珪酸ガドリニウム単結晶等は、シンチレータ等に用いられる場合、一般に円柱あるいは直方体の形状のものが使用される。実際には更に、１面〜全面を鏡面研磨し、鏡面研磨を施した一面を除いて反射材を塗布あるいは巻き付けた状態で、反射材の無い面を光電子増倍管に密着させて使用される。
この単結晶はへき開性が強く（１００）面に沿って割れ易い等の性質を持ち、比較的脆弱な結晶である。そのため、結晶育成冷却時や加工時に割れが発生し易く、一般に、へき開面に平行な平面を有する形状に加工する方法が用いられる。
【０００３】
【発明が解決しようとする課題】
しかし、この従来法では、へき開面に平行な平面を切断をしたり研磨したりする際に、この加工面がへき開面（（１００）面）に完全に一致しないことをによる、へき開面の剥がれが発生する場合があり、平滑な加工面が得られないという問題があった。
本発明は、希土類珪酸塩単結晶を加工する場合に、へき開面近傍の切断面の角度を選択して加工を行うことにより、剥がれの無い平滑な加工面を持つ単結晶を提供するものである。
【０００４】
【課題を解決するための手段】
上記目的を達成するために、本発明者らは、希土類珪酸塩単結晶を切断する場合の、加工面のへき開面（（１００）面）からの傾きの角度と剥がれの発生状況の関係について検討した。その結果、加工面がへき開面（（１００）面）からずれていても、傾きの角度が５°以上であればへき開面の剥がれを防止できることを見だすことによって、本発明は成されたものである。
【０００５】
【作用】
希土類珪酸塩単結晶を加工する場合において、へき開面（（１００）面）に最も近い加工面のへき開面からの傾きの角度を５°以上にし加工を行うことによりへき開面の剥がれを防止できる原因は次のように考えられる。
希土類珪酸塩単結晶の材料力学特性を調べた結果、希土類珪酸塩単結晶には塑性変形を示す方向があることがわかった。その塑性変形は、単結晶のへき開面（（１００）面）に垂直方向に荷重し［００１］軸方向に引っ張りの応力が作用する場合に発生する。また、へき開割れの破壊靱性値は（０１０）面よりも（００１）−１７°面（［００１］軸を法線方向とする面）の方が約１桁小さく、へき開割れは（０１０）面側からよりも（００１）−１７°面側から発生し易いこともわかった。
希土類珪酸塩単結晶のこれらの材料特性から、へき開面（（１００）面）は（１００）面（（００１）−１７°面）側から非常に剥がれ易い。したがって、切断加工する場合に加工面がへき開面（（１００）面）からわずかにずれた面（特に［００１］軸と傾きを成す方向にずれた面）であると、へき開面の剥がれが非常に発生し易いと考えられる。しかし、切断加工面がへき開面からずれるほど加工面におけるへき開面の剥がれは発生しなくなると考えられる。実際には一定角度以上ずらすことにより、へき開面の剥がれの発生は防止することができる
。すなわち、へき開面（（１００）面）との傾きの角度が５°以上の面を加工面に選択して加工することによって、加工面におけるへき開面の剥がれを確実に防止することができた。
【０００６】
珪酸ガドリニウム単結晶以外の、化１の一般式
【化１】
Ｒ2 ＳｉＯ5
（但し、ＲはＬａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、Ｙ、Ｓｃから選ばれて成る１種以上の希土類元素）
で示される希土類珪酸塩単結晶についても、結晶の力学特性は同様であり、同様の結果となる。
更に、これらの希土類珪酸塩単結晶にＣｅ等の希土類元素やＣｒ等の鉄属遷移金属をドープした場合も、効果は同様である。
以上の希土類珪酸塩単結晶は、珪酸ガドリニウム単結晶の結晶構造と同じ結晶構造を持ち、その構造は空間群Ｐ２／ｃに属する。
【０００７】
【実施例】
比較例１
セリウム付活珪酸ガドリニウム単結晶（Ｃｅ：Ｇｄ2 ＳｉＯ5 ）の場合の例を説明する。寸法２０×２０×１０ｍｍ3 で２０×２０ｍｍ3 面が２面鏡面の直方体の試料を加工した。
目的とするサイズの試料が十分採取できる大きさの、へき開面に平行な引上軸で育成した結晶ブロックについて、結晶ブロックの端部に発生した或いは発生させたへき開面（（１００）面）の割れ、またはシードのへき開面に互いに垂直になるような２対向面でブロックを切断した。そして、最後にへき開面に平行に１対向面（２０×２０ｍｍ3 ）を切断した。しかし、へき開面に平行に切断したはずの面には、切断後面の端部に剥がれが発生した。その後この面の研磨を行ったが、新たに剥がれが発生し、平滑な加工面が得られなかった（図２）。そこで、その面をＸ線カット面検査機によって調べた結果、任意のｘ及びｙ方向についてそれぞれ２°及び１°３０’ずつずれていた。
【０００８】
比較例２
比較例１と同様に、セリウム付活珪酸ガドリニウム単結晶について、寸法２０×２０×１０ｍｍ3 で２０×２０ｍｍ3 面が２面鏡面の直方体の試料を加工した。
目的とするサイズの試料が十分採取できる大きさの、へき開面に平行な引上軸で育成した結晶ブロックについて、結晶ブロックの端部に発生した或いは発生させたへき開面（（１００）面）の割れ、またはシードのへき開面に平行になるように、結晶ブロックの表面を薄く切断した。切断した面をＸ線カット面検査機によって調べた結果、任意のｘ及びｙ方向についてそれぞれ１°４０’及び２°１０’ずつずれていた。そこで正確なへき開面に互いに垂直な２対向面でブロックを切断し、最後に正確なへき開面に平行に１対向面（２０×２０ｍｍ3 ）を切断した。その結果、切断後のへき開面の剥がれが無く、その後の鏡面研磨加工でも剥がれが発生しない試料を作成することができた（図２）。
【０００９】
実施例
比較例と同様に、セリウム付活珪酸ガドリニウム単結晶について、寸法２０×２０×１０ｍｍ3 で２０×２０ｍｍ3 面が２面鏡面の直方体の試料を加工した。目的とするサイズの試料が十分採取できる大きさの、へき開面に平行な引上軸で育成した結晶ブロックについて、結晶ロックの端部に発生した或いは発生させたへき開面（（１００）面）の割れに平行な面から任意の方向に適当に傾けた面に、互いに垂直な２対向面でブロック切断し、最後にこの傾けた面に平行に１対向面、（２０×２０ｍｍ3 ）を切断した。このへき開面に最も近い加工面には、へき開面の剥がれが発生しなかった。また、その後の鏡面研磨によっても、剥がれは発生することなく、平滑な加工面が得られた（図１）。そこで、その面をＸ線カット面検査機によって調べた結果、（１００）面から任意のｘ及びｙ方向に
、それぞれ５°及び２°ずつずれていた。
【００１０】
【発明の効果】
本発明の単結晶の加工方法により、へき開面のある単結晶について、へき開面の剥がれの無いへき開面に近い加工面を持つ試料を採取することができる。また、一般にへき開性のある単結晶は、引上軸をへき開面に平行にして育成されるため、容易にへき開面の方向を把握でき、面倒な方位だしをすること無く、かつ形状的に採取効率良く試料を加工採取することができる。
上記のへき開面からの傾きは、５°以上であれば最大の９０°まで、加工時のへき開面の剥がれ等は発生しない。
【図面の簡単な説明】
【図１】実施例において加工した結晶の斜視図。
【図２】比較例１において加工した結晶の斜視図。[0001]
[Industrial application fields]
The present invention relates to a rare earth silicate single crystal used for scintillators and the like.
[0002]
[Prior art]
Rare earth silicate single crystals such as gadolinium silicate single crystals are widely used as scintillators, phosphors and the like.
When the gadolinium silicate single crystal belonging to the monoclinic system is used for a scintillator or the like, a cylinder or a rectangular parallelepiped is generally used. Actually, one surface to the entire surface is mirror-polished, and the surface without the reflecting material is used in close contact with the photomultiplier tube in a state where the reflecting material is applied or wound except for one surface subjected to the mirror-polishing. .
This single crystal is a relatively fragile crystal that has a high cleavage property and is easily broken along the (100) plane. Therefore, cracks are likely to occur during crystal growth cooling and during processing, and generally a method of processing into a shape having a plane parallel to the cleavage plane is used.
[0003]
[Problems to be solved by the invention]
However, in this conventional method, when the plane parallel to the cleaved surface is cut or polished, the processed surface does not completely coincide with the cleaved surface ((100) surface). In some cases, a smooth processed surface cannot be obtained.
The present invention provides a single crystal having a smooth processed surface without peeling by selecting an angle of a cut surface in the vicinity of a cleavage plane when processing a rare earth silicate single crystal. .
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors examined the relationship between the angle of inclination of the processed surface from the cleavage plane ((100) plane) and the occurrence of peeling when cutting a rare earth silicate single crystal. did. As a result, the present invention has been made by finding that even if the processed surface is deviated from the cleaved surface ((100) surface), the cleaved surface can be prevented from peeling off if the inclination angle is 5 ° or more. It is.
[0005]
[Action]
Reasons for preventing peeling of the cleavage plane when machining the rare-earth silicate single crystal by making the machining surface closest to the cleavage plane ((100) plane) an inclination angle of 5 ° or more from the cleavage plane. Is considered as follows.
As a result of examining the material mechanical properties of the rare earth silicate single crystal, it was found that the rare earth silicate single crystal has a direction of plastic deformation. The plastic deformation occurs when a tensile stress is applied in the [001] axial direction when a load is applied perpendicularly to the cleavage plane ((100) plane) of the single crystal. In addition, the fracture toughness value of cleavage cracks is about an order of magnitude smaller in the (001) -17 ° plane (plane with the [001] axis as the normal direction) than in the (010) plane, and the cleavage crack is in the (010) plane. It was also found that it is more likely to occur from the (001) -17 ° plane side than from the side.
From these material characteristics of the rare earth silicate single crystal, the cleavage plane ((100) plane) is very easy to peel off from the (100) plane ((001) -17 ° plane) side. Therefore, when the cut surface is a surface slightly shifted from the cleaved surface ((100) surface) (particularly a surface shifted in a direction inclined with respect to the [001] axis), the cleaved surface is extremely peeled off. It is thought that it is easy to occur. However, it is considered that the cleaved surface does not peel off as the cut surface is displaced from the cleaved surface. Actually, the cleaved surface can be prevented from peeling off by shifting it by a certain angle or more. That is, it was possible to reliably prevent the cleaved surface from being peeled off on the processed surface by selecting and processing the surface having an inclination angle of 5 ° or more with the cleaved surface ((100) surface).
[0006]
General formula of chemical formula 1 other than gadolinium silicate single crystal
R 2 SiO 5
(Where R is one or more rare earth elements selected from La, Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc)
As for the rare earth silicate single crystal represented by the formula, the mechanical properties of the crystal are the same, and the same result is obtained.
Furthermore, the same effect is obtained when these rare earth silicate single crystals are doped with a rare earth element such as Ce or an iron group transition metal such as Cr.
The above rare earth silicate single crystal has the same crystal structure as that of the gadolinium silicate single crystal, and the structure belongs to the space group P2 / c.
[0007]
【Example】
Comparative Example 1
An example in the case of a cerium-activated gadolinium silicate single crystal (Ce: Gd 2 SiO 5 ) will be described. A rectangular parallelepiped sample having a dimension of 20 × 20 × 10 mm 3 and a 20 × 20 mm 3 surface being a double mirror surface was processed.
For a crystal block grown with a pull-up axis parallel to the cleavage plane that is large enough to collect a sample of the desired size, the cleavage plane ((100) plane) generated or generated at the end of the crystal block The block was cut at two opposing surfaces that were perpendicular to the cracked or cleaved surface of the seed. Finally, one opposing surface (20 × 20 mm 3 ) was cut parallel to the cleavage plane. However, the surface that should have been cut parallel to the cleavage plane was peeled off at the end of the cut surface. Thereafter, this surface was polished, but new peeling occurred and a smooth processed surface could not be obtained (FIG. 2). Therefore, as a result of examining the surface with an X-ray cut surface inspection machine, the surface was shifted by 2 ° and 1 ° 30 ′ in any x and y directions, respectively.
[0008]
Comparative Example 2
In the same manner as in Comparative Example 1, a cerium-activated gadolinium silicate single crystal was processed into a rectangular parallelepiped sample having a dimension of 20 × 20 × 10 mm 3 and a 20 × 20 mm 3 surface having a two-sided mirror surface.
For a crystal block grown with a pull-up axis parallel to the cleavage plane that is large enough to collect a sample of the desired size, the cleavage plane ((100) plane) generated or generated at the end of the crystal block The surface of the crystal block was thinly cut so as to be parallel to the crack or the cleavage plane of the seed. As a result of examining the cut surface with an X-ray cut surface inspection machine, it was shifted by 1 ° 40 ′ and 2 ° 10 ′ in any x and y directions, respectively. Therefore, the block was cut with two opposing surfaces perpendicular to the accurate cleavage surface, and finally one opposing surface (20 × 20 mm 3 ) was cut in parallel with the accurate cleavage surface. As a result, it was possible to produce a sample in which the cleaved surface was not peeled after cutting, and no peeling occurred even in the subsequent mirror polishing process (FIG. 2).
[0009]
Example In the same manner as in the comparative example, a cerium-activated gadolinium silicate single crystal was processed into a rectangular parallelepiped sample having a dimension of 20 × 20 × 10 mm 3 and a 20 × 20 mm 3 plane having a two-sided mirror surface. For a crystal block grown with a pull-up shaft parallel to the cleavage plane that is large enough to collect a sample of the desired size, the cleavage plane ((100) plane) generated or generated at the end of the crystal lock Block cutting was performed with two opposing surfaces perpendicular to each other on a surface appropriately inclined in an arbitrary direction from a surface parallel to the crack, and finally one opposing surface (20 × 20 mm 3 ) was cut in parallel with this inclined surface. . No peeling of the cleaved surface occurred on the processed surface closest to the cleaved surface. Further, even with the subsequent mirror polishing, a smooth processed surface was obtained without causing peeling (FIG. 1). Therefore, as a result of examining the surface with an X-ray cut surface inspection machine, the surface was shifted by 5 ° and 2 ° in arbitrary x and y directions from the (100) surface, respectively.
[0010]
【The invention's effect】
According to the method for processing a single crystal of the present invention, a sample having a processed surface close to a cleaved surface with no cleavage of the cleaved surface can be collected for a single crystal having a cleaved surface. In general, cleaved single crystals are grown with the pulling axis parallel to the cleaved surface, so the direction of the cleaved surface can be easily grasped, and it is collected in a shape without troublesome orientation. Samples can be processed and collected efficiently.
If the inclination from the cleaved surface is 5 ° or more, the cleaved surface is not peeled off during processing until the maximum 90 °.
[Brief description of the drawings]
FIG. 1 is a perspective view of a crystal processed in an example.
2 is a perspective view of a crystal processed in Comparative Example 1. FIG.
Claims (3)
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5967394A JP3914269B2 (en) | 1994-03-30 | 1994-03-30 | Rare earth silicate single crystal |
| US08/413,287 US5667583A (en) | 1994-03-30 | 1995-03-30 | Method of producing a single crystal of a rare-earth silicate |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5967394A JP3914269B2 (en) | 1994-03-30 | 1994-03-30 | Rare earth silicate single crystal |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2003315670A Division JP3627749B2 (en) | 2003-09-08 | 2003-09-08 | Rare earth silicate single crystal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH07267794A JPH07267794A (en) | 1995-10-17 |
| JP3914269B2 true JP3914269B2 (en) | 2007-05-16 |
Family
ID=13119954
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5967394A Expired - Lifetime JP3914269B2 (en) | 1994-03-30 | 1994-03-30 | Rare earth silicate single crystal |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3914269B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4622329B2 (en) * | 2003-07-24 | 2011-02-02 | 日立化成工業株式会社 | Rare earth silicate single crystal and method for producing rare earth silicate single crystal |
-
1994
- 1994-03-30 JP JP5967394A patent/JP3914269B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| JPH07267794A (en) | 1995-10-17 |
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