JP4228609B2 - Cerium-activated gadolinium silicate single crystal - Google Patents
Cerium-activated gadolinium silicate single crystal Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
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。この珪酸ガドリニウム単結晶等は、希土類酸化物の酸化ガドリニウムと珪素酸化物の二酸化珪素を原料として、チョクラルスキー法等の原料融液から単結晶を育成する方法によって製造される。更に、一般には希土類珪酸塩単結晶に蛍光中心としてＣｅ等の添加物をドープしている。蛍光減衰時間等のシンチレータ特性には、構成元素以外の希土類元素及び遷移金属等の不純物が悪影響を与えると考えられ、それらの不純物元素を低減した９９．９９重量％以上の高純度原料（Ｇｄ2Ｏ3、ＳｉＯ2等）を使用して結晶育成が行なわれている。
【０００３】
【発明が解決しようとする課題】
従来の珪酸ガドリニウム単結晶等の希土類珪酸塩単結晶をシンチレータとして用いた場合の発光減衰曲線は２成分からなり、減衰の速い成分（Ｆａｓｔ成分）は３０〜６０ｎｓ、遅い成分（Ｓｌｏｗ成分）は４００〜６００ｎｓであり、その減衰の速い成分（Ｆａｓｔ成分）と遅い成分（Ｓｌｏｗ成分）の出力比（存在比）はそれぞれ７０〜８０％：３０〜２０％程度であった。このため蛍光減衰時間の短縮化が望まれるＰＥＴ（陽電子放出核種断層撮像装置、Ｐｏｓｉｔｒｏｎｅｍｉｓｓｉｏｎ ｃｏｍｐｕｔｅｄ ｔｏｍｏｇｒａｐｈｙ）用シンチレータでは発光減衰曲線の遅い成分（Ｓｌｏｗ成分）のみを高速化させ、その出力比（存在比）を低減することが望まれていた。
本発明は発光減衰曲線の遅い成分（Ｓｌｏｗ成分）を低減し、蛍光減衰時間を短縮化することを特徴とする希土類珪酸塩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】
本発明は、特定の不純物を添加した希土類珪酸塩単結晶、すなわちＡｌを５ｐｐｍ以上５０ｐｐｍ以下含有させることにより蛍光減衰時間を短縮化することを特徴とする希土類珪酸塩単結晶である。なお、上記希土類珪酸塩単結晶は、Ｃｅをドープした珪酸ガドリニウム単結晶である。
【０００５】
【発明の実施の形態】
本発明者らは、希土類珪酸塩単結晶の発光減衰曲線の２成分：減衰の速い成分（Ｆａｓｔ成分）及び遅い成分（Ｓｌｏｗ成分）とそれぞれの出力比（存在比）と、その原料である希土類珪酸塩単結晶中の不純物濃度について検討した結果、特定の不純物元素を含有させることが、育成した単結晶の特性に影響することを見いだし本発明に達した。すなわち珪酸ガドリニウム単結晶中にＡｌを０．４ｐｐｍを超えて５０ｐｐｍ以下含有させることによって発光減衰曲線の遅い成分（Ｓｌｏｗ成分）を低減し、蛍光減衰時間の短縮化が図られ、シンチレータ特性を向上できることがわかった。
【０００６】
本発明における希土類珪酸塩単結晶中のＡｌの含有量は５ｐｐｍ〜４０ｐｐｍの範囲、最も好ましくは１０〜３０ｐｐｍの範囲である。
【０００７】
不純物Ａｌの含有量が０．４ｐｐｍ以下の場合、発光減衰曲線における遅い成分（Ｓｌｏｗ成分）は低減されず、蛍光減衰時間は短縮化されない。一方、不純物Ａｌの含有量が０．４ｐｐｍを超えると、発光減衰曲線における遅い成分（Ｓｌｏｗ成分）が低減され、蛍光減衰時間は短縮化される。しかし、不純物Ａｌの含有量が５０ｐｐｍを超えると、蛍光出力が急激に減少し劣化する。
【０００８】
本発明の希土類珪酸塩単結晶は、珪酸ガドリニウム単結晶以外の、一般式Ｌｎ２−ｘＣｅｘＳｉＯ５（但し、Ｌｎ＝Ｓｃ、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ、Ｅｕ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ及びＬｕからなる群より選ばれる少なくとも１種の元素を表し、ｘ＝０〜２の値である）で示される希土類珪酸塩単結晶についても、同様の結果となる。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Ｐ２１／ｃに属する。
【０００９】
【実施例】
本発明を実施例に基づいて具体的に説明する。原料として酸化ガドリニウム（Ｇｄ２Ｏ３、９９．９９重量％）、二酸化珪素（ＳｉＯ２、９９．９９重量％）、酸化セリウム（ＣｅＯ２、９９．９９重量％）、及び酸化アルミニウム（Ａｌ２Ｏ３、９９．９９重量％）を使用して、チョクラルスキー法によって単結晶を育成した。単結晶から１０×１０×１０ｍｍ３の試料を採取して、シンチレータのエネルギースペクトル（１３７Ｃｓ）及びデジタルオシロにより発光減衰曲線を測定し、蛍光減衰時間、減衰成分の存在比（Ｆａｓｔ成分／Ｓｌｏｗ成分）、及び蛍光出力をまとめて表１に示した。ただし、それぞれの実施例について３本の単結晶を育成し、その平均値を示した。なお、本実施例は好適な一例を示すもので、本発明はこれらの実施例に限定されるものではない。
【００１０】
（参考例１）
Ｃｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶を以下のようにして作製した。酸化ガドリニウムを２５７３．５ｇ、二酸化珪素を４２６．５ｇ、酸化セリウムを５．９ｇ、そして酸化アルミニウムを０．００７５ｇ秤量して混合し、１２００℃で焼成した後直径１００ｍｍのＩｒるつぼにチャージし、原料融液１９５０℃、種結晶の回転数３０ｒｐｍ、引き上げ速度２ｍｍ／ｈの条件で、原料の８０重量％が結晶化した段階で引き上げを完了し、直径５０ｍｍの単結晶を育成した。作製した結晶中のＡｌ濃度測定を、誘導結合プラズマ（ＩＣＰ：Ｉｎｄｕｃｔｉｖｅｌｙ Ｃｏｕｐｌｅｄ Ｐｌａｓｍａ）質量分析法を用いて測定した結果、０．６ｐｐｍであった。
【００１１】
（実施例２）
Ｃｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶を以下のようにして作製した。酸化ガドリニウムを２５７３．５ｇ、二酸化珪素を４２６．５ｇ、酸化セリウムを５．９ｇ、そして酸化アルミニウムを０．３ｇ秤量して混合し、１２００℃で焼成した後直径１００ｍｍのＩｒるつぼにチャージし、原料融液１９５０℃、種結晶の回転数３０ｒｐｍ、引き上げ速度２ｍｍ／ｈの条件で、原料の８０重量％が結晶化した段階で引き上げを完了し、直径５０ｍｍの単結晶を育成した。作製した結晶中のＡｌ濃度測定を、誘導結合プラズマ（ＩＣＰ）質量分析法を用いて測定した結果、２４ｐｐｍであった。
【００１２】
（実施例３）
Ｃｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶を以下のようにして作製した。酸化ガドリニウムを２５７３．５ｇ、二酸化珪素を４２６．５ｇ、酸化セリウムを５．９ｇ、そして酸化アルミニウムを０．５６２５ｇ秤量して混合し、１２００℃で焼成した後直径１００ｍｍのＩｒるつぼにチャージし、原料融液１９５０℃、種結晶の回転数３０ｒｐｍ、引き上げ速度２ｍｍ／ｈの条件で、原料の８０重量％が結晶化した段階で引き上げを完了し、直径５０ｍｍの単結晶を育成した。作製した結晶中のＡｌ濃度測定を、誘導結合プラズマ（ＩＣＰ）質量分析法を用いて測定した結果、４５ｐｐｍであった。
【００１３】
比較例として、実施例と同様にＣｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶の場合の例を説明する。原料として実施例で使用したものと全く同じ（精製ロット番号も同じ）酸化ガドリニウム（Ｇｄ２Ｏ３、９９．９９重量％）と、二酸化珪素（ＳｉＯ２、９９．９９重量％）、酸化セリウム（ＣｅＯ２、９９．９９重量％）及び酸化アルミニウム（Ａｌ２Ｏ３、９９．９９重量％）を使用して、チョクラルスキー法によって単結晶を育成した。単結晶から１０×１０×１０ｍｍ３の試料を採取して、シンチレータのエネルギースペクトル（１３７Ｃｓ）及びデジタルオシロにより発光減衰曲線を測定し、蛍光減衰時間、減衰成分の存在比（Ｆａｓｔ成分／Ｓｌｏｗ成分）、及び蛍光出力をまとめて表１に示した。ただし、それぞれの条件について３本の単結晶を育成し、その平均値を示した。
【００１４】
（比較例１）
Ｃｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶を以下のようにして作製した。酸化ガドリニウムを２５７３．５ｇ、二酸化珪素を４２６．５ｇ、そして酸化セリウムを５．９ｇ秤量して混合し、１２００℃で焼成した後直径１００ｍｍのＩｒるつぼにチャージし、原料融液１９５０℃、種結晶の回転数３０ｒｐｍ、引き上げ速度２ｍｍ／ｈの条件で、原料の８０重量％が結晶化した段階で引き上げを完了し、直径５０ｍｍの単結晶を育成した。作製した結晶中のＡｌ濃度測定を、誘導結合プラズマ（ＩＣＰ）質量分析法を用いて測定した結果、０ｐｐｍであった。
【００１５】
（比較例２）
Ｃｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶を以下のようにして作製した。酸化ガドリニウムを２５７３．５ｇ、二酸化珪素を４２６．５ｇ、酸化セリウムを５．９ｇ、そして酸化アルミニウムを０．００２５ｇ秤量して混合し、１２００℃で焼成した後直径１００ｍｍのＩｒるつぼにチャージし、原料融液１９５０℃、種結晶の回転数３０ｒｐｍ、引き上げ速度２ｍｍ／ｈの条件で、原料の８０重量％が結晶化した段階で引き上げを完了し、直径５０ｍｍの単結晶を育成した。作製した結晶中のＡｌ濃度測定を、誘導結合プラズマ（ＩＣＰ）質量分析法を用いて測定した結果、０．２ｐｐｍであった。
【００１６】
（比較例３）
Ｃｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶を以下のようにして作製した。酸化ガドリニウムを２５７３．５ｇ、二酸化珪素を４２６．５ｇ、酸化セリウムを５．９ｇ、そして酸化アルミニウムを０．６５ｇ秤量して混合し、１２００℃で焼成した後直径１００ｍｍのＩｒるつぼにチャージし、原料融液１９５０℃、種結晶の回転数３０ｒｐｍ、引き上げ速度２ｍｍ／ｈの条件で、原料の８０重量％が結晶化した段階で引き上げを完了し、直径５０ｍｍの単結晶を育成した。作製した結晶中のＡｌ濃度測定を、誘導結合プラズマ（ＩＣＰ）質量分析法を用いて測定した結果、５２ｐｐｍであった。
【００１７】
（比較例４）
Ｃｅ濃度０．４８ｍｏｌ％の珪酸ガドリニウム単結晶を以下のようにして作製した。酸化ガドリニウムを２５７３．５ｇ、二酸化珪素を４２６．５ｇ、酸化セリウムを５．９ｇ、そして酸化アルミニウムを０．８７５ｇ秤量して混合し、１２００℃で焼成した後直径１００ｍｍのＩｒるつぼにチャージし、原料融液１９５０℃、種結晶の回転数３０ｒｐｍ、引き上げ速度２ｍｍ／ｈの条件で、原料の８０重量％が結晶化した段階で引き上げを完了し、直径５０ｍｍの単結晶を育成した。作製した結晶中のＡｌ濃度測定を、誘導結合プラズマ（ＩＣＰ）質量分析法を用いて測定した結果、７０ｐｐｍであった。
【００１８】
【表１】
比較例１、２に示したように、不純物Ａｌの濃度が低いと発光減衰曲線の遅い成分（Ｓｌｏｗ成分）は低減されず、蛍光減衰時間は短縮化されない。一方、参考例１、実施例２及び３に示したように、不純物Ａｌ濃度が０．４ｐｐｍを越すとＳｌｏｗ成分の存在比は低減し、その結果蛍光減衰時間は大きく短縮化される。しかし、比較例３、４に示したように、不純物Ａｌの濃度が５０ｐｐｍを越すと蛍光減衰時間は短縮化されるが、蛍光出力が急激に低下し、シンチレータ特性が劣化する。不純物Ａｌ濃度を５ｐｐｍ以上５０ｐｐｍ以下の範囲に存在させることにより、シンチレータ特性を保ちながら蛍光減衰時間を短縮化させることができ、これによりＰＥＴ装置の高速診断化を図ることができる。
【００２０】
【発明の効果】
本発明による希土類珪酸塩単結晶は発光減衰曲線の遅い成分（Ｓｌｏｗ成分）を低減し、蛍光減衰時間の短縮化を図ることができる。[0001]
BACKGROUND OF THE INVENTION
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. The gadolinium silicate single crystal or the like is manufactured by a method of growing a single crystal from a raw material melt such as the Czochralski method using gadolinium oxide as a rare earth oxide and silicon dioxide as a silicon oxide as raw materials. Further, generally, a rare earth silicate single crystal is doped with an additive such as Ce as a fluorescent center. It is considered that impurities such as rare earth elements other than constituent elements and transition metals adversely affect the scintillator characteristics such as fluorescence decay time, and a high-purity raw material (Gd 2 ) of 99.99% by weight or less in which those impurity elements are reduced. O 3 , SiO 2, etc.) are used for crystal growth.
[0003]
[Problems to be solved by the invention]
When a rare earth silicate single crystal such as a conventional gadolinium silicate single crystal is used as a scintillator, the emission decay curve is composed of two components, a fast decay component (Fast component) is 30 to 60 ns, and a slow component (Slow component) is 400. The output ratio (abundance ratio) of the fast decaying component (Fast component) and the slow slowing component (Slow component) was about 70 to 80%: 30 to 20%, respectively. For this reason, in a PET (Positron emission computed tomography) scintillator for which shortening of the fluorescence decay time is desired, only the slow component of the emission decay curve (Slow component) is accelerated, and its output ratio (existence ratio) It has been desired to reduce this.
The present invention provides a rare earth silicate single crystal characterized by reducing a slow component of the emission decay curve (Slow component) and shortening the fluorescence decay time.
[0004]
[Means for Solving the Problems]
The present invention is a rare earth silicate single crystal to which a specific impurity is added, that is, a rare earth silicate single crystal characterized by shortening the fluorescence decay time by containing 5 ppm to 50 ppm of Al. Incidentally, the rare earth silicate single crystal, Ru gadolinium silicate single crystal der doped with Ce.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The inventors of the present invention have two components of the emission decay curve of a rare earth silicate single crystal: a fast decay component (Fast component) and a slow component (Slow component), their respective output ratios (abundance ratios), and the rare earth that is the raw material. As a result of examining the impurity concentration in the silicate single crystal, it was found that the inclusion of a specific impurity element affects the characteristics of the grown single crystal, and the present invention has been achieved. That is, by containing Al in the gadolinium silicate single crystal in excess of 0.4 ppm to 50 ppm, the slow emission decay curve component (Slow component) can be reduced, the fluorescence decay time can be shortened, and the scintillator characteristics can be improved. I understood.
[0006]
The content of Al in the rare earth silicate single crystal in the present invention is in the range of 5 ppm to 40 ppm, and most preferably in the range of 10 to 30 ppm.
[0007]
When the content of the impurity Al is 0.4 ppm or less, the slow component (Slow component) in the emission decay curve is not reduced, and the fluorescence decay time is not shortened. On the other hand, when the content of the impurity Al exceeds 0.4 ppm, a slow component (Slow component) in the emission decay curve is reduced, and the fluorescence decay time is shortened. However, if the content of the impurity Al exceeds 50 ppm, the fluorescence output decreases rapidly and deteriorates .
[0008]
Rare earth silicate single crystal of the present invention, other than gadolinium silicate single crystal, the formula Ln 2-x Ce x SiO 5 ( where, Ln = Sc, Y, La , Ce, Pr, Nd, Pm, Sm, Eu, The same applies to the rare earth silicate single crystal represented by at least one element selected from the group consisting of Tb, Dy, Ho, Er, Tm, Yb, and Lu, where x = 0 to 2. Result. 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 P21 / c.
[0009]
【Example】
The present invention will be specifically described based on examples. As raw materials, gadolinium oxide (Gd 2 O 3 , 99.99% by weight), silicon dioxide (SiO 2 , 99.99% by weight), cerium oxide (CeO 2 , 99.99% by weight), and aluminum oxide (Al 2 O) 3 , 99.99 wt%) were used to grow single crystals by the Czochralski method. A sample of 10 × 10 × 10 mm 3 is taken from a single crystal, the emission spectrum is measured by the scintillator energy spectrum ( 137 Cs) and a digital oscilloscope, the fluorescence decay time, the abundance ratio of the decay component (Fast component / Slow component) ) And fluorescence output are shown together in Table 1. However, three single crystals were grown for each example, and the average value was shown. In addition, a present Example shows a suitable example, This invention is not limited to these Examples.
[0010]
( Reference Example 1)
A gadolinium silicate single crystal having a Ce concentration of 0.48 mol% was prepared as follows. 2573.5 g of gadolinium oxide, 426.5 g of silicon dioxide, 5.9 g of cerium oxide, and 0.0075 g of aluminum oxide were weighed and mixed, fired at 1200 ° C., charged into an Ir crucible having a diameter of 100 mm, Pulling was completed when 80 wt% of the raw material was crystallized under the conditions of the melt at 1950 ° C., the seed crystal rotation speed of 30 rpm, and the pulling speed of 2 mm / h, and a single crystal having a diameter of 50 mm was grown. The Al concentration in the produced crystal was measured using an inductively coupled plasma (ICP) mass spectrometry, and found to be 0.6 ppm.
[0011]
(Example 2)
A gadolinium silicate single crystal having a Ce concentration of 0.48 mol% was prepared as follows. 2573.5 g of gadolinium oxide, 426.5 g of silicon dioxide, 5.9 g of cerium oxide, and 0.3 g of aluminum oxide were weighed and mixed, baked at 1200 ° C., and charged into an Ir crucible having a diameter of 100 mm. Pulling was completed when 80 wt% of the raw material was crystallized under the conditions of the melt at 1950 ° C., the seed crystal rotation speed of 30 rpm, and the pulling speed of 2 mm / h, and a single crystal having a diameter of 50 mm was grown. As a result of measuring the Al concentration in the produced crystal using inductively coupled plasma (ICP) mass spectrometry, it was 24 ppm.
[0012]
(Example 3)
A gadolinium silicate single crystal having a Ce concentration of 0.48 mol% was prepared as follows. 2573.5 g of gadolinium oxide, 426.5 g of silicon dioxide, 5.9 g of cerium oxide, and 0.5625 g of aluminum oxide were weighed and mixed, fired at 1200 ° C., and charged into an Ir crucible having a diameter of 100 mm. Pulling was completed when 80 wt% of the raw material was crystallized under the conditions of the melt at 1950 ° C., the seed crystal rotation speed of 30 rpm, and the pulling speed of 2 mm / h, and a single crystal having a diameter of 50 mm was grown. As a result of measuring the Al concentration in the produced crystal using inductively coupled plasma (ICP) mass spectrometry, it was 45 ppm.
[0013]
As a comparative example, an example in the case of a gadolinium silicate single crystal having a Ce concentration of 0.48 mol% will be described as in the example. Gadolinium oxide (Gd 2 O 3 , 99.99 wt%), silicon dioxide (SiO 2 , 99.99 wt%), cerium oxide (exactly the same as those used in the examples as raw materials) CeO 2, 99.99 wt%) and aluminum oxide (Al 2 O 3, using 99.99% by weight), were grown single crystal by the Czochralski method. A sample of 10 × 10 × 10 mm 3 is taken from a single crystal, the emission spectrum is measured by the scintillator energy spectrum ( 137 Cs) and a digital oscilloscope, the fluorescence decay time, the abundance ratio of the decay component (Fast component / Slow component) ) And fluorescence output are shown together in Table 1. However, three single crystals were grown for each condition and the average value was shown.
[0014]
(Comparative Example 1)
A gadolinium silicate single crystal having a Ce concentration of 0.48 mol% was prepared as follows. 2573.5 g of gadolinium oxide, 426.5 g of silicon dioxide, and 5.9 g of cerium oxide were weighed and mixed, baked at 1200 ° C., charged into an Ir crucible having a diameter of 100 mm, raw material melt at 1950 ° C., seed crystal Under the conditions of 30 rpm and a pulling speed of 2 mm / h, pulling was completed when 80% by weight of the raw material was crystallized, and a single crystal having a diameter of 50 mm was grown. As a result of measuring the Al concentration in the produced crystal using inductively coupled plasma (ICP) mass spectrometry, it was 0 ppm.
[0015]
(Comparative Example 2)
A gadolinium silicate single crystal having a Ce concentration of 0.48 mol% was prepared as follows. 2573.5 g of gadolinium oxide, 426.5 g of silicon dioxide, 5.9 g of cerium oxide, and 0.0025 g of aluminum oxide were weighed and mixed, fired at 1200 ° C., and charged into an Ir crucible having a diameter of 100 mm. Pulling was completed when 80 wt% of the raw material was crystallized under the conditions of the melt at 1950 ° C., the seed crystal rotation speed of 30 rpm, and the pulling speed of 2 mm / h, and a single crystal having a diameter of 50 mm was grown. As a result of measuring the Al concentration in the produced crystal using inductively coupled plasma (ICP) mass spectrometry, it was 0.2 ppm.
[0016]
(Comparative Example 3)
A gadolinium silicate single crystal having a Ce concentration of 0.48 mol% was prepared as follows. 2573.5 g of gadolinium oxide, 426.5 g of silicon dioxide, 5.9 g of cerium oxide, and 0.65 g of aluminum oxide were weighed and mixed, fired at 1200 ° C., and charged into an Ir crucible having a diameter of 100 mm. Pulling was completed when 80 wt% of the raw material was crystallized under the conditions of the melt at 1950 ° C., the seed crystal rotation speed of 30 rpm, and the pulling speed of 2 mm / h, and a single crystal having a diameter of 50 mm was grown. It was 52 ppm as a result of measuring Al concentration in the produced crystal | crystallization using the inductively coupled plasma (ICP) mass spectrometry.
[0017]
(Comparative Example 4)
A gadolinium silicate single crystal having a Ce concentration of 0.48 mol% was prepared as follows. 2573.5 g of gadolinium oxide, 426.5 g of silicon dioxide, 5.9 g of cerium oxide, and 0.875 g of aluminum oxide were weighed and mixed, fired at 1200 ° C., and charged into an Ir crucible having a diameter of 100 mm. Pulling was completed when 80 wt% of the raw material was crystallized under the conditions of the melt at 1950 ° C., the seed crystal rotation speed of 30 rpm, and the pulling speed of 2 mm / h, and a single crystal having a diameter of 50 mm was grown. As a result of measuring the Al concentration in the produced crystal by using inductively coupled plasma (ICP) mass spectrometry, it was 70 ppm.
[0018]
[Table 1]
As shown in Comparative Examples 1 and 2, when the concentration of impurity Al is low, the slow emission decay curve component (Slow component) is not reduced, and the fluorescence decay time is not shortened. On the other hand , as shown in Reference Example 1, Examples 2 and 3, when the impurity Al concentration exceeds 0.4 ppm, the abundance ratio of the Slow component is reduced, and as a result, the fluorescence decay time is greatly shortened. However, as shown in Comparative Examples 3 and 4, when the concentration of the impurity Al exceeds 50 ppm, the fluorescence decay time is shortened, but the fluorescence output is drastically lowered and the scintillator characteristics are deteriorated. By allowing the impurity Al concentration to be in the range of 5 ppm or more and 50 ppm or less, the fluorescence decay time can be shortened while maintaining the scintillator characteristics, thereby enabling high-speed diagnosis of the PET apparatus.
[0020]
【The invention's effect】
The rare earth silicate single crystal according to the present invention can reduce the slow emission decay curve component (Slow component) and shorten the fluorescence decay time.
Claims (1)
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| JP2002221536A JP4228609B2 (en) | 2002-07-30 | 2002-07-30 | Cerium-activated gadolinium silicate single crystal |
| US10/621,350 US6926847B2 (en) | 2002-07-30 | 2003-07-18 | Single crystals of silicates of rare earth elements |
| DE10334513A DE10334513B4 (en) | 2002-07-30 | 2003-07-29 | A process for producing a single crystal of a cerium-doped gadolinium silicate |
| FR0309375A FR2843131B1 (en) | 2002-07-30 | 2003-07-30 | RARE EARTH ELEMENTS SILICATE MONOCRYSTAL AND SCINTILLATOR CONTAINING SAME |
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