Scintillator crystal, method for manufacturing the same, and article containing the same

Abstract

This specification discloses rare earth oxyoltosilicate crystals having formula (1), where Lu is lutetium, A comprises a trivalent ion substitution selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or combinations thereof, B comprises a non-trivalent ion substitution selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof, and C is Ce 3+ Ce 4+ , Pr 3+ The activating cation substitution is selected from a combination thereof, where D comprises a monovalent halogen anion selected from F, Cl, Br, or a combination thereof, and E comprises a trivalent ion substitution selected from La, Sc, Y, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or any combination thereof.

Description

[Technical Field] 【0001】 This disclosure relates to scintillator crystals, methods for manufacturing the same, and articles containing the same. In particular, this disclosure relates to scintillator materials used for detecting ionizing radiation in nuclear imaging applications, especially in PET (positron emission tomography), TOF PET (time-of-flight positron emission tomography), and / or DOI TOF PET (depth-of-flight positron emission tomography) imaging. 【0002】 Lutetium oxyorthosilicate (LSO), or cerium (Ce 3+ Lu2SiO5 activated by ) is a well-known crystalline scintillator material and is widely used in medical imaging, such as gamma-ray detection in positron emission tomography (PET) and other applications. Due to its relatively high photoyield and short decay time, LSO is considered one of the most suitable materials for molecular imaging applications, particularly for time-of-flight PET (TOF PET). 【0003】 LSO scintillators are typically fabricated from single-crystal LSO grown from a molten material, for example, using the Czochralski method. For scintillator applications, it is often desirable to be able to grow large single crystals of LSO with specific scintillation performance parameters. The composition, size, and quality of the grown crystal can be greatly influenced by the stability of the growth process. 【0004】 While LSO scintillators with different dopant and co-dopant schemes have been well developed, efforts continue to develop rare-earth oxyoltosilicate scintillators with selected equivalent and heterovalent substitutions at different concentrations to improve scintillation properties for specific applications. [Overview of the Initiative] 【0005】 Rare earth oxyorthosilicate scintillators are commonly used in medical diagnostic applications, particularly in time-of-flight positron emission tomography. 【0006】 By selectively varying the molar ratio of polyvalent substitution ions in the scintillation composition of rare earth oxyorthosilicate crystals, the resulting crystals can show a significant increase in the scintillation light output of the material, energy resolution, coincidence time resolution, scintillation rise time, and improvement in decay time characteristics compared to compositions activated only with cerium and / or praseodymium without polyvalent substitution. The polyvalent ions can be incorporated into the crystal lattice at relatively low concentrations, typically at doping and co-doping levels commonly used (less than 1 atomic percent). Such substitutions, along with the stabilization of Ce 4+ in the crystal lattice, result in a change in the concentration ratio of Ce 3+ and Ce 4+ and lead to an improvement in scintillation performance. Also, the polyvalent ions can be incorporated at much higher concentrations, which are essential components of modified scintillator host lattices having different translational symmetries. By selecting a specific molar concentration ratio of polyvalent ions, it is possible to control the size of the crystal lattice unit cell and, in some cases, its strain, affect the segregation of specific ions from the melt during the crystal growth process, as well as modify the charge state of these ions and their positions at the crystal sites. 【0007】 The performance of the rare earth oxyorthosilicate compositions described in the disclosure of the present invention provides a significant improvement in the coincidence time resolution of the time-of-flight of a PET system. 【0008】 Disclosed herein are rare earth oxyorthosilicate crystals having the following formula (1). Lu 2(1-a-b-c-d) A 2a B 2b C 2c D 2d Si (1-x+y) E y O 5(1-z) (1) In the formula, Lu is lutetium, A comprises a trivalent ionic species selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or combinations thereof, B comprises a non-trivalent ionic species selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof, and C is Ce 3+ Ce 4+ , Pr 3+ A comprises an activated cation selected from a combination thereof, D comprises a monovalent halogen anion selected from F, Cl, Br, or a combination thereof, E comprises a trivalent ion selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or any combination thereof, a exists in amounts of 0.5 ≤ a ≥ 0; b exists in amounts of 0.5 ≤ b ≥ 0; c exists in amounts of 0.5 ≤ c ≥ 0.00001; d exists in amounts of 0.5 ≤ d ≥ 0; x exists in amounts of 0.05 ≤ x ≥ 0; y exists in amounts of 0.05 ≤ y ≥ 0; z exists in amounts of 0.2 ≤ z ≥ 0; the sum of a + b is always greater than 0; the sum of a + b + c + d is always less than 1; and A and C cannot be the same trivalent cation at the same time. 【0009】 This specification also discloses a method for producing rare earth oxyoltosilicate crystals, which includes producing a powder having the composition of the following formula (1). Lu 2(1-a-b-c-d) A 2a B 2b C 2c D 2d Si (1-x+y) E y O 5(1-z) (1) In the formula, Lu is lutetium; A comprises a trivalent ionic species selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or combinations thereof; B comprises a non-trivalent ionic species selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof; C is Ce 3+ Ce 4+ , Pr 3+ D comprises an activated cation selected from , or a combination thereof, where D comprises a monovalent halogen anion selected from F, Cl, Br, or a combination thereof; E comprises a trivalent ion selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or any combination thereof; a is present in amounts of 0.5 ≤ a ≥ 0; b is present in amounts of 0.5 ≤ b ≥ 0; c is present in amounts of 0.5 ≤ c ≥ 0.00001. The following conditions apply: a+b is present in an amount of 0.5≦d≧0; x is present in an amount of 0.05≦x≧0; y is present in an amount of 0.05≦y≧0; z is present in an amount of 0.2≦z≧0; the sum of a+b is always greater than 0; the sum of a+b+c+d is always less than 1; A and C cannot be the same trivalent cation at the same time; the powder is melted in a crucible at a temperature of 1500°C to 2300°C, and the crystals are pulled from the molten material using the Czochralski method or a similar technique. [Brief explanation of the drawing] 【0010】 [Figure 1] Figure 1 is a graph showing the afterglow for samples A, B, C, and the LSO reference. [Figure 2] Figure 2 is a graph showing the energy spectra of different compositions A, B, C, and LSO reference. [Figure 3] Figure 3 shows the simultaneous count resolution times for samples A, B, C, and the LSO reference. [Figure 4] Figure 4 shows that the relative concentration of oxygen vacancies (thermluminescence peak above 300K) is significantly reduced in the case of sample A compared to sample D (reference standard). [Figure 5] Figure 5 shows the thermal responses of samples A to D. [Figure 6] Figure 6 shows the radioluminescence of selected samples A to D. [Figure 7] Figure 7 shows the absorbance spectra of Ce3+ and Ce4+ for the selected samples A to D. [Modes for carrying out the invention] 【0011】 definition Rise time is the time interval during which the amplitude of the light pulse following the absorption of a gamma photon increases from 10% to 90% of its maximum value. 【0012】 A scintillation light pulse (flash) is typically characterized by a rapid increase in intensity over time (pulse rise time) followed by an exponential or multi-exponential decrease. The decay time of the scintillator is defined as the time it takes for the intensity of the light pulse to decrease to 1 / e of its maximum value. 【0013】 The optical output of most scintillators (the number of photons per 1 MeV of gamma energy absorbed by the scintillator) is a function of temperature. This is due to the fact that in scintillation crystals, radiative transitions involved in the generation of scintillation light compete with non-radiative transitions (no photogeneration). 【0014】 Synchronization time resolution (CTR) and synchronization time resolution (CRT) are interchangeable terms commonly used in positron emission tomography. 【0015】 This specification discloses rare-earth oxy-orthosilicate scintillator compositions (hereinafter referred to as "scintillator compositions") that contain ratios of trivalent, divalent, and monovalent ions incorporated into the crystal lattice as equivalent and heterovalent substitutions. As a result, the resulting scintillator single crystals exhibit a significant increase in scintillation light output, as well as improvements in energy resolution, temporal resolution, decay time, and rise time characteristics, compared to compositions activated solely with cerium and / or praseodymium without polyvalent substitution. 【0016】 Polyvalent ions can be incorporated into the crystal lattice at relatively low concentrations, typically at commonly used doping and co-doping levels (less than 1 atomic percent). As a result of some such substitutions, Ce in the crystal lattice 4+ Along with the stabilization of Ce 3+ and Ce 4+ This can lead to changes in enrichment ratios and improve scintillation performance. Furthermore, such substitutions may result in changes to the relative proportions of Ce1 and Ce2 crystal sites. Polyvalent ions can also be incorporated at much higher concentrations, becoming essential components of modified scintillator host lattices with different translational symmetries. 【0017】 By selecting a specific molar concentration ratio of polyvalent ions in rare-earth oxy-orthosilicates, the size of crystal lattice unit cells, and potentially their strain, can be controlled, influencing not only the segregation of specific ions from the molten material during the crystal growth process, but also altering the charge state of these ions and their positions at crystal sites. The performance of the rare-earth oxy-orthosilicate compositions described herein significantly improves the synchronization time-by-hour resolution for time-of-flight PET systems. This disclosure relates, in particular, to the control of the decay time, rise time, scintillation light output, and synchronization time-by-hour resolution of rare-earth oxy-orthosilicates. 【0018】 The present invention applies to methods for producing rare earth oxy-orthosilicate crystals by growing them from a molten material using the Czochralski method or other similar methods, some of which will be described in detail later. The molten composition includes the addition of polyvalent ions in carefully selected molar ratios. These ratios are calculated in relation to the molar concentrations of activator co-dopants such as cerium and / or praseodymium. The composition of the molten material and the growth process control parameters directly affect the thermodynamics of the crystal growth process, altering Marangoni convection, thermal convection, evaporation losses, and thermal decomposition of the molten material at different stages of the growth process. As a result, the stoichiometric composition of the grown crystal may differ significantly from that of the original molten material. 【0019】 Based on their ionic radius and electronic charge state, the crystallographic lattice symmetry of the resulting crystal can be modified by adding specific equivalent and heterovalent cations and anions to the molten material. These modifications elongate or contract crystal lattice sites, disrupting the periodic symmetry of the crystal. The presence of these modified lattice sites affects the incorporation of dopants and co-dopants in their immediate vicinity. Ionic radius can influence the segregation of specific dopants and co-dopants from the molten material within the lattice. This makes it possible to suitably increase the concentration of specific dopants and co-dopants that affect the scintillation properties of the material, while limiting the concentration of other dopants whose sole purpose is to alter the thermodynamics of the crystallization process. 【0020】 By selecting suitable equivalent and heterovalent ions at predetermined relative concentration ratios, the following results are obtained: • Changes in the concentration of ions incorporated into the crystal lattice during the crystal growth process. Changes in the distribution of trivalent and divalent ions between different crystallographic sites, such as rare earth element sites and oxy-orthosilicate crystal sites, as well as at interstitial positions that compensate for oxygen vacancy deficiencies. • Changes in the relative spatial distribution of trivalent and divalent ions, and the formation of predetermined clusters consisting of divalent, trivalent, and activated ions. • The electronic charge state of ions incorporated into rare-earth oxy-orthosilicate lattices, specifically, its influence on the charge state ratio of cerium 3+ and 4+ at both crystallographic sites Ce1 and Ce2. Control of cerium ion population at both Ce1 and Ce2 cerium crystallographic sites. 【0021】 In the thermodynamics of the growth process, there are statistical probabilities that lead to the depletion of specific ions, resulting in an imbalance in the charge state of defects within the lattice. This imbalance governs the selective incorporation of ion substitutions into specific crystallographic sites, which can then become rare-earth sites, oxyoltosilicate sites, or interstitial sites in order to restore charge balance. 【0022】 La 3+ Ce 3+ , Pr 3+ , Nd 3+ Sm 3+ ,EU 3+ , Gd 3+ , Tb 3+ Dy 3+ Ho 3+ Er 3+ , Tm 3+ Yb 3+ Lu 3+ , Sc 3+ , Y 3+ Trivalent cations like the monovalent element can primarily substitute for the rare earth components of rare earth oxyoltosilicate lattices. 3+ , Al 3+ In 3+ , Ga 3+ Sb 3+ Au 3+ , Bi 3+ , Rh 3+ This refers to the deficient orthosilicate SiO within the lattice of rare earth oxyorthosilicates. 4- Si in ionic complexes 4+These can be primarily substituted. These deficiencies may result from the loss of stoichiometric composition (which may be due to intentional compositional selection), the selection of growth process parameters, or evaporation and decomposition losses during the growth process. 【0023】 Be 2+ Mg 2+ Ca 2+ Sr 2+ Ba 2+ Zn 2+ , Cd 2+ Ni 2+ Divalent cations like these monovalent elements can be substituted to compensate for rare-earth oxyoltosilicate oxygen vacancies that occur during the growth process. 【0024】 F -1 Cl -1 , Br -1 , O -2 Anions such as Ce 3+ or Ce 4+ These can be added indirectly as commercially available chemical variant compounds of activators. These are typically commercially available as cerium(IV) fluoride (CeF4), cerium(III) chloride (CeCl3), cerium(III) bromide (CeBr3), cerium(IV) oxide (CeO2), cerium(III) oxide (Ce2O3), or combinations thereof. 【0025】 As for the monovalent element of the trivalent cation mentioned above, La 3+ Ce 3+ , Pr 3+ , Nd 3+ Sm 3+ ,EU 3+ , Gd 3+ , Tb 3+ Dy 3+ Ho 3+ Er 3+ , Tm 3+ Yb 3+ Lu 3+ , Sc 3+ , Y 3+or combinations thereof, can be incorporated into the lattice at higher concentrations and can expand or contract the crystal lattice of the rare earth oxyorthosilicate lattice unit cell. The cerium activator added to the melt can be incorporated into the lattice in the vicinity of these ions. As a result, the surroundings of cerium can create favorable conditions for cerium to change its charge state from 3+ to 4+. Cerium in the 4+ state allows for faster decay times and rise times in scintillation emission. Mg 2+ Ca 2+ and Sr 2+ divalent ions such as can also be incorporated into specific lattice positions based on their ionic radii. They can suitably modify the scintillation performance of the rare earth oxyorthosilicate scintillator by changing the occupancy numbers of two crystallographic sites of Ce 3+ in the oxyorthosilicate lattice. One of these sites results in fast scintillation emission with a decay time of less than 40 nanoseconds (ns), and the other results in slow emission exceeding 40 ns. Another result of these substitutions is charge state compensation. 【0026】 The addition of SiO2 at a specific concentration can be used to compensate for the incongruency of the melt that occurs in an oxygen-deficient environment during crystal growth. SiO2 is introduced as the orthosilicate anion SiO 4- . The melt of rare earth oxyorthosilicate can partially decompose under high temperature and oxygen-deficient atmospheres due to the volatility of the evaporation loss of SiO / SiO2. The oxygen deficiency in the melt due to the decomposition of the melt components can create thermally reversible defects such as oxygen vacancies in the resulting crystal lattice. These can be compensated by the controlled addition of oxygen at high temperatures and the incorporation of divalent ions (e.g., Mg 2+ Ca 2+ Sr 2+ or Ba 3+ ) into the lattice during the growth and post-growth processes. 【0027】 The Y listed above at a selected concentration ratio with respect to the concentration of the cerium activator 3+ , Gd 3+ , Al 3+ , Ga 3+ , In 3+ , or B 3+ and the use of other trivalent cations can compensate for the loss of Si 4- and O of the complex site 4+ in the SiO 2- complex. The selected trivalent cation replaces Si 4+ and creates an imbalance in the charge state. Electron transfer from Ce 3+ to the complex results in a stable Ce 4+ state and restores charge balance. 【0028】 In one embodiment, the scintillation composition has the following general chemical formula (1): Lu 2(1-a-b-c-d) A 2a B 2b C 2c D 2d Si (1-x+y) E y O 5(1-z) (1) and contains a rare earth oxyorthosilicate represented by. Here, A includes trivalent ion species (substitutions) selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or combinations thereof, B includes non-trivalent (e.g., monovalent or divalent) ion species (substitutions) selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof, and C includes Ce 3+ , Ce 4+ , Pr 3+It includes trivalent dopant (activated) cation substitutions such as ions, or combinations thereof; D includes monovalent halogen anions; E includes elements selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or combinations thereof; a exists in amounts of 0.5 ≤ a ≥ 0; b exists in amounts of 0.5 ≤ b ≥ 0; c exists in amounts of 0.5 ≤ c ≥ 0.00001; d exists in amounts of 0.5 ≤ d ≥ 0; x exists in amounts of 0.05 ≤ x ≥ 0; y exists in amounts of 0.05 ≤ y ≥ 0; z exists in amounts of 0.2 ≤ z ≥ 0; the sum of a + b is always greater than 0; and the sum of a + b + c + d is always less than 1. In one embodiment, the values ​​of a, b, c, and d are never simultaneously greater than or equal to 0.25, the maximum sum of a+b+c+d is in the range of 0.00001 to 0.4, preferably 0.00015 to 0.35, and x ≥ y. In one embodiment, the ratio of b:c in equation (1) may be 1:1 to 10:1, preferably 2:1 to 5:1, and the ratio of a:c in equation (1) may be 2.5:1 to 15:1, preferably 4:1 to 10:1. 【0029】 In equation (1), the term "x" represents the loss of silica and is always greater than "y". Here, y represents substitution by element E. The term "z" represents the loss of oxygen during manufacturing and signifies the presence of oxygen vacancies in the crystal. 【0030】 In one embodiment of formula (1), Lu is lutetium; A comprises a trivalent ion substitution selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or combinations thereof; B comprises a non-trivalent ion substitution selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof; C is Ce 3+ Ce 4+ , Pr 3+The cation substitution includes an activated cation substitution selected from a combination thereof; D includes a monovalent halogen anion; E includes a trivalent ion substitution (relative to silica) selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or any combination thereof; a is present in amounts of 0.5 ≤ a ≥ 0; b is present in amounts of 0.5 ≤ b ≥ 0; c is present in amounts of 0.5 ≤ c ≥ 0.00001; d is present in amounts of 0.5 ≤ d ≥ 0; x is present in amounts of 0.05 ≤ x ≥ 0; y is present in amounts of 0.05 ≤ y ≥ 0; z is present in amounts of 0.2 ≤ z ≥ 0; the sum of a + b is always greater than 0; the sum of a + b + c + d is always less than 1; and A and C cannot be the same trivalent cation at the same time. In one embodiment, A, C, and E cannot be the same trivalent cation at the same time. In another embodiment, the content of ion-substituted E(relative to Si) is defined by x≧y. 【0031】 In one embodiment, the rare earth oxyolthosilicate is a single crystal. In some embodiments, A is a trivalent cation of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or a combination thereof; B is a non-trivalent cation (e.g., monovalent or divalent cation) of Mg, Ca, Sr, Ba, Na, K, Rb, Mn, Cu, Zn, or a combination thereof; C is Ce 3+ Ce 4+ , Pr 3+ , or a combination thereof; D is a monovalent halogen anion such as F, Cl, Br, or a combination thereof. 【0032】 In one embodiment, A and C cannot be the same trivalent cation at the same time. For example, if A is a trivalent cation of Ce (e.g., Ce 3+ If C is the tetravalent cation of Ce (for example, Ce 4+ ) or the trivalent cation of Pr (for example, Pr 3+) is one of the following. In some embodiments, a is in an amount of 0.000001 to 0.25, preferably 0.001 to 0.2, preferably 0.01 to 0.15, preferably 0.05 to 0.1. In some embodiments, b is in an amount of 0.000001 to 0.25, preferably 0.001 to 0.2, preferably 0.01 to 0.15, preferably 0.05 to 0.1. In some embodiments, c is in an amount of 0.00002 to 0.35, preferably 0.001 to 0.3, preferably 0.002 to 0.2, preferably 0.01 to 0.15, preferably 0.05 to 0.1. In some embodiments, d is in an amount of 0.00002 to 0.35, preferably 0.001 to 0.3, preferably 0.002 to 0.2, preferably 0.01 to 0.15, preferably 0.05 to 0.1. In some embodiments, x is an amount of 0.00002 to 0.05, preferably 0.001 to 0.05, preferably 0.002 to 0.04, preferably 0.01 to 0.03, preferably 0.02 to 0.025. In some embodiments, y is an amount of 0.00002 to 0.05, preferably 0.001 to 0.04, preferably 0.002 to 0.03, preferably 0.01 to 0.025, preferably 0.015 to 0.025. In some embodiments, z is an amount of 0.00002 to 0.05, preferably 0.001 to 0.04, preferably 0.002 to 0.03, preferably 0.01 to 0.025, preferably 0.015 to 0.025. 【0033】 In some embodiments, La 3+ , Nd 3+ Sm 3+ ,EU 3+ , Gd 3+ , Tb 3+ Dy 3+ Ho 3+ Er 3+ , Tm 3+ Yb 3+ , Sc 3+ , Y 3+ , Al 3+ , Ga 3+ B 3+ In 3+ , Bi 3+ , Rh3+ Au 3+ ,Sb 3+ The addition of trivalent ions (not activated cation C), such as cerium, cerium, or combinations thereof, can be incorporated into the crystal lattice at a higher concentration, causing the crystal lattice unit cells to expand and contract as described above. In other words, trivalent ions that are not activated cation C cause dimensional changes in the crystal lattice unit cells. As a result, the environment around cerium can create favorable conditions for cerium to change its charge state from 3+ to 4+, which has a positive effect on the scintillation performance of the crystal. In other words, activated cation C changes its charge state from 3+ to 4+ when its nearest neighbor is one of the trivalent ion species A (e.g., trivalent cation A) or non-trivalent ion species B (e.g., monovalent cation B or divalent cation B). 【0034】 Cerium in the 4+ state allows for a faster decay time component of scintillation emission. Mg 2+ Ca 2+ Sr 2+ and Ba 2+ Divalent ions like these can be incorporated into specific lattice positions based on their ionic radii. These are Ce in rare earth oxyoltosilicate systems. 3+ The scintillation performance of rare-earth oxy-orthosilicate scintillators can be improved by changing the number of occupancies of two crystallographic sites. One of these sites results in fast scintillation emission with a decay time of less than 40 nanoseconds (ns), while the other results in slow emission exceeding 40 ns. 【0035】 In one embodiment, the molar ratio of trivalent cation A (in formula (1)) to activated ion C is greater than 0.1:1, preferably greater than 2:1, preferably greater than 4:1, preferably greater than 5:1, preferably greater than 8:1, and more preferably greater than 10:1. As described above, A and C cannot be the same trivalent cation at the same time. 【0036】 In another embodiment, the molar ratio of the non-trivalent (e.g., monovalent or divalent) cation B (in formula (1)) to the activated cation C is greater than 1:1, preferably greater than 1.5:1, preferably 2:1 or greater, preferably 3:1 or greater, preferably 4:1 or greater, and more preferably 5:1 or greater. In one embodiment, it may be desirable to simultaneously incorporate at least one trivalent cation A and at least two different monovalent or divalent cations (in addition to the activated trivalent or tetravalent cation C) into the crystal lattice. 【0037】 In a preferred embodiment, at least one trivalent cation A(La 3+ , Pr 3+ Ce 3+ , Nd 3+ Sm 3+ ,EU 3+ , Gd 3+ , Tb 3+ Dy 3+ Ho 3+ Er 3+ , Tm 3+ Yb 3+ , Sc 3+ , Y 3+ , Al 3+ , Ga 3+ B 3+ In 3+ , Bi 3+ Au 3+ Sb 3+ , Rh 3+ (or a combination thereof) activated cation C (Ce 3+ Ce 4+ , Pr 3+ With respect to ions (selected from any combination thereof), at least 1:1, preferably at least 5:1, more preferably at least 10:1 molar ratios are simultaneously incorporated, while at least two cations (Mg 2+ Ca 2+ Sr 2+ Ba 2+ kaNa 1+ , K 1+ , Rb 1+ Mn 2+ Mn 4+ Mn 7+ Cu2+ Cu 1+ Zn 2+ It may be desirable to incorporate (or a combination thereof) in a molar ratio of at least 2:1 relative to the activated cation C. 【0038】 In one embodiment, trivalent ion substitution A and divalent ion substitution B alter the distribution of cerium-doped rare-earth oxyorthosilicate cerium ions to mainly occupy Ce1 crystallographic sites. In another embodiment, trivalent ion substitution A and divalent ion substitution B alter the distribution of cerium-doped rare-earth oxyorthosilicate cerium ions to mainly occupy Ce1 crystallographic sites. 4+ To change the state of charge. 【0039】 In one embodiment, a method for producing a single crystal involves placing raw material powder in a crucible and heating it using induction heating. The powder has an average particle size in the range of 5 nanometers to 500 micrometers, preferably 10 nanometers to 50 micrometers, and more preferably 1 to 20 micrometers. The average particle size is determined by measuring the radius of gyration of the particles. Light scattering or electron microscopy can be used to determine the particle size. 【0040】 In one embodiment, nanometer and / or micrometer-sized particles can be manufactured (or purchased separately) and mixed together to form the composition of formula (1) above. For example, nanometer and / or micrometer-sized powder of rare earth oxy-orthosilicate can be mixed with other particles (e.g., metal oxide particles, dopant particles) in a desired stoichiometric amount to form an intimate mixture. The intimate mixture is then heated to a high temperature as detailed below to form a single crystal. In other words, nanometer and / or micrometer-sized metal oxide powders of Lu, A, B, and C, as well as silica (from formula (1)), can be mixed with (optionally) a C halide to produce an intimate mixture, which can then be heated as detailed below to form a single crystal. 【0041】 In one embodiment, lutetium oxide powder of nanometer or micrometer size is added to the blender or mixer in the stoichiometric ratios detailed above. Metal oxide powder or metal salt of nanometer or micrometer size (e.g., oxides or salts of Lu, A, and B) is added to the blender or mixer in the stoichiometric amounts listed above. Silica of nanometer or micrometer size may also be added to the blender or mixer. Activated cation C (also called a dopant) (also in nanometer or micrometer size particles) can be added to the blender or mixer in the form of a salt (e.g., in the form of a metal halide) or as a metal oxide. Other reactants listed above can also be added to the blender or mixer. The powders thus added to the blender or mixer are subjected to blending to form a close mixture. 【0042】 The powder obtained from a homogeneous mixture can first be mixed and, if necessary, further ground. The ground powder can then be subjected to any sieving process if it is desirable to use particles of a specific size. 【0043】 Next, the powder for producing rare earth oxy-orthosilicate is melted in an oxygen-containing atmosphere at a temperature of 1500°C to 2300°C, preferably 1800°C to 2200°C, to produce polycrystalline or single crystals that can be used as scintillators in the next step. 【0044】 Single crystals can be prepared by the Czochralski method, Bridgman method, Cairopolos method, and Bernoulli method. 【0045】 In the Czochralski process, the powder to be grown is melted in a suitable non-reaction vessel under a controlled atmosphere. The material is melted by controlling the furnace temperature up to 2100°C. The seed crystal is lowered to come into contact with the molten charge (molten raw material) for nucleation. The nucleated seed crystal is then pulled out of the molten material at a controlled rate. Using this method, large-diameter crystals can be grown. 【0046】 In the Bridgman (downward) technique, the material is melted in a vertical cylindrical container (called an ampoule) that is tapered in a narrow, conical shape. The container is slowly lowered from a high-temperature zone to a low-temperature zone in a furnace with temperatures up to 2100°C. The movement speed of such a process ranges from approximately 1 to 30 mm / hour. Crystallization begins at the tip and is usually continued by growth from the nuclei that were initially formed. The directional cooling process of the casting creates zones of aligned crystal lattices, thus allowing for the production of single crystals. 【0047】 In the Cairopolos method, crystals are grown with a larger diameter than in the two methods mentioned above. Similar to the Czochralski method, a seed crystal is brought into contact with the molten material, but the seed crystal is not pulled up very far during growth. That is, a portion of the seed crystal is melted, and a short, thin neck is grown. After this, the vertical movement of the seed crystal is stopped, and growth is continued by reducing the power input to the molten material. 【0048】 In the Bernoulli process (flame melting method), fine, dry powder of the material to be grown, measuring 1 to 20 micrometers in size, is shaken through a wire mesh and dropped through an oxygen-hydrogen flame. The powder melts, and a liquid film forms on top of the seed crystal. This gradually solidifies as the seed crystal slowly descends. The key to this method is balancing the raw material supply rate with the seed crystal's descent rate to maintain a constant growth rate and diameter. 【0049】 In one embodiment, rare earth oxyoltosilicate crystals are annealed for 10 to 80 hours at a temperature of 1200 to 1800°C in an oxygen-containing environment having more than 1% by weight of oxygen. 【0050】 The rare earth oxyoltosilicate crystals disclosed herein exhibit higher optical output than rare earth oxyoltosilicate crystals that do not contain polyvalent cation substitutions. For example, rare earth oxyoltosilicate crystals that do not contain polyvalent cation substitutions exhibit an optical output of less than 24,000 photons per MeV (ph / MeV), while rare earth oxyoltosilicate crystals containing polyvalent cation substitutions exhibit an optical output of more than 25,000 ph / MeV, preferably more than 27,000 ph / MeV, preferably more than 30,000 ph / MeV, preferably more than 31,000 ph / MeV, preferably more than 33,000 ph / MeV, and more preferably more than 34,000 ph / MeV. 【0051】 In one embodiment, a rare-earth oxyoltosilicate crystal containing the polyvalent ion substitutions disclosed herein exhibits a photoattenuation of less than 35 nanoseconds, preferably less than 33 nanoseconds, and more preferably less than 30 nanoseconds. In contrast, a single crystal without polyvalent cation substitutions has a decay time of more than 42 nanoseconds. 【0052】 In one embodiment, a rare-earth oxyoltosilicate crystal containing a polyvalent cation substitution as disclosed herein exhibits a percent energy resolution of 6.5 to 8.5%, preferably 6.75 to 7.50%, at 511 kiloelectron volts (keV). A rare-earth oxyoltosilicate crystal without a polyvalent cation substitution as disclosed herein exhibits a percent energy resolution of more than 9.4% at 511 kiloelectron volts (keV). 【0053】 The rare earth oxyoltholicates disclosed herein are illustrated by the following non-limiting examples. [Examples] 【0054】 Example 1 This example was performed to demonstrate the advantages of having polyvalent ions (tetravalent, trivalent, and divalent cations) substituted in rare earth oxyolthosilicates. 3+ The molar ratio of various trivalent cations (Y, Yb, Sc, Dy, and La) to the cation is 10:1, and each of the two or more divalent cations (Mg and Ca) is Ce 3+ Rare earth oxyoltosilicate crystals with a molar ratio of 2:1 to cations were prepared by the Czochralski process. The above ratio is for the molten state. The properties are shown in Table 1 below. 【0055】 [Table 1] 【0056】 Ce 3+ The co-doped, polyvalent ion-free reference composition exhibits a simultaneous resolution time (CRT) of 160 picoseconds (ps), a decay time of 42 nanoseconds (ns), an optical output (LO) of 25,000 ph / MeV, an energy resolution (ER) of 9.7%, and high afterglow. In contrast, rare-earth oxy-orthosilicate crystals containing polyvalent ion substitution (shown in Table 1) exhibit a CRT of 10⁵–120 picoseconds and a measured absolute optical output. 【0057】 Example 2 This embodiment demonstrates the linearity of samples A and B, which are detailed below. Sample A - Ce measured after heat post-treatment 3+ A polyvalent compound of formula 1 having a divalent cation substitution ratio of Mg2:1 and Ca2:1. 【0058】 Sample B - LSO Mg ratio of 0.25:1 measured after post-heat treatment. Tables 2 and 3 show the linearity for samples A and B, respectively. 【0059】 [Table 2] 【0060】 [Table 3] 【0061】 The composition of Equation 1 exhibits good energy linearity and energy resolution over a wide range of excitation energies. 【0062】 Example 3 These examples illustrate various properties of the following compositions. Samples A, B, and C shown in the following figure represent different compositions derived from formula (1) using different selected substitutions. 【0063】 Sample A - Composition of formula (1) after heat treatment, where Ce 3+ The molar ratios for divalent ion substitution are as follows: Mg 2:1, Ca 2:1. 【0064】 Sample B-LSO0.25:1, composition of formula (1) after heat treatment, Ce 3+ The molar ratio of divalent ion substitution for is as follows: Mg 0.25:1. 【0065】 Sample C - Composition of formula (1) after heat treatment, where Ce 3+ The molar ratio of divalent ion substitution for is as follows: Mg 2:1, Ca2:1, without heat treatment. 【0066】 Samples D and "ref" are rare-earth oxyoltosilicate materials that do not contain additional polyvalent ion substitutions. The properties of these rare-earth oxyoltosilicates (Samples A, B, C, D, and "ref") are shown in Figures 1-7. 【0067】 Figure 1 is a graph showing afterglow. Sample A, which includes polyvalent substitution and has undergone heat post-treatment, shows the lowest afterglow. 【0068】 Figure 2 is a graph showing the energy spectra measured under 662 keV excitation. Sample B shows the best relative optical output. 【0069】 Figure 3 shows the coincidence resolving time (CRT) for various samples. Sample A shows the best relative CRT. 【0070】 Figure 4 shows the relative concentration of oxygen vacancies (thermluminescence peaks above 300K). This concentration is significantly lower in sample A compared to sample D (reference standard). 【0071】 Figure 5 shows the thermal response of the compositions detailed above. Sample A exhibits significantly better light output stability compared to Sample C at temperatures above 300K, demonstrating the improvement in material performance due to thermal post-treatment after growth. 【0072】 Figure 6 shows the radioluminescence of the selected compositions. Sample A shows a slight shift in the UV region, which indicates an increase in the number of Ce1 sites relative to a decrease in the number of Ce2 sites compared to the reference sample D. This effect contributes to the shorter scintillation emission in the new composition. 【0073】 Figure 7 shows the absorption of materials described by formula (1) with different levels of trivalent and divalent substitution ratios. 4+ Stronger Ce between 220nm and 350nm 4+ O 2- It demonstrated charge transfer absorption. 【0074】 While the present invention has been described with reference to several embodiments, it will be understood by those skilled in the art that various modifications can be made without departing from the scope of the invention, and that equivalents can be used in place of certain elements. In addition, many modifications can be made without departing from the essential scope of the invention to adapt the teachings of the invention to specific situations or materials. Thus, the present invention is not limited to the specific embodiments disclosed as the best mode intended to carry out the invention, but is intended to include all embodiments encompassed in the appended claims.

Claims

[Claim 1] The following equation (1): Lu 2(1-a-b-c-d) A 2a B 2b C 2c D 2d Si (1-x+y) E y O 5(1-z) (1) Here, in the formula, Lu is lutetium, A contains trivalent ion substitution selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or combinations thereof, B contains non-trivalent ion substitution selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof, C contains activating cation substitution selected from Ce 3+ , Ce 4+ , Pr 3+ , or combinations thereof, D contains monovalent halogen anion substitution selected from F, Cl, Br, or combinations thereof, E contains trivalent ion substitution selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or combinations thereof, a is present in an amount of 0.5 ≦ a ≧ 0, b is present in an amount of 0.5 ≦ b ≧ 0, c is present in an amount of 0.5 ≦ c ≧ 0.00001, d is present in an amount of 0.5 ≦ d ≧ 0, x is present in an amount of 0.05 ≦ x ≧ 0, y is present in an amount of 0.05 ≦ y ≧ 0, z is present in an amount of 0.2 ≦ z ≧ 0, the sum of a + b is always greater than 0, the sum of a + b + c + d is always less than 1, and A and C cannot be the same trivalent cation simultaneously. A rare earth oxy-oltosilicate scintillator composition containing [the specified element]. [Claim 2] The scintillator according to claim 1, wherein the values ​​of a, b, c, and d are not all simultaneously 0.25 or greater, and the sum of a + b + c + d is in the range of 0.00001 to 0.

4. [Claim 3] The scintillator according to claim 1, wherein A is selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, or a combination thereof. [Claim 4] B is a monovalent or divalent cation selected from Mg, Ca, Sr, Ba, Na, K, Rb, Mn, Cu, Zn, or combinations thereof. D is an anion of F, Cl, Br, or a combination thereof. The scintillator according to claim 3. [Claim 5] A is the trivalent cation of Ce (Ce 3+ If ), then C is the tetravalent cation of Ce (Ce 4+ ) or the trivalent cation of Pr (Pr 3+ ) is one of the following: The scintillator according to claim 1. [Claim 6] The scintillator according to claim 1, wherein the trivalent ion other than the activated cation C causes a change in the dimensions of the crystal lattice. [Claim 7] The activated cation C is in its initial state Ce 3+ When this is the case, if its nearest neighbor is the trivalent ion-substituted A and the non-trivalent ion-substituted B, then its charge state is Ce 3+ From Ce 4+ The scintillator according to claim 4, which changes to the following. [Claim 8] The scintillator according to claim 1, wherein the molar ratio of trivalent ion-substituted A to activated cation C is greater than 0.1:1, and the molar ratio of non-trivalent ion-substituted B to activated cation C is greater than 1:

1. [Claim 9] The scintillator according to claim 8, wherein the content of ion-substituted E is defined by x ≥ y. [Claim 10] The scintillator according to claim 1, wherein the molar ratio of trivalent ion substitution A to activated cation substitution C is greater than 5:1, and the molar ratio of non-trivalent ion substitution B to activated cation substitution C is greater than 2:

1. [Claim 11] A contains at least one trivalent cation, B contains at least two different non-trivalent cations in its crystal lattice. The scintillator according to claim 1. [Claim 12] A trivalent cation substitution A is La 3+ , Pr 3+ Ce 3+ , Nd 3+ Sm 3+ , Eu 3+ , Gd 3+ , Tb 3+ , Dy 3+ Ho 3+ Er 3+ , Tm 3+ Yb 3+ , Sc 3+ , Y 3+ Al 3+ Ga 3+ , B 3+ In 3+ , Bi 3+ Au 3+ Sb 3+ , Rh 3+ From these, or combinations thereof, selected in a molar ratio of at least 10:1 with respect to activated cation-substituted C, Non-trivalent cation-substituted B is Mg 2+ Ca 2+ , Sr 2+ Ba 2+ Na 1+ _K 1+ , Rb 1+ Mn 2+ ,Cd 2+ ,Cd 1+ , Zn 2+ , or a combination thereof, selected in a molar ratio of at least 2:1 with respect to activated cation-substituted C, The scintillator according to claim 11. [Claim 13] The scintillator generates an optical output exceeding 25,000 ph / MeV. The scintillator according to claim 1. [Claim 14] The scintillator produces a light attenuation of less than 35 nanoseconds. The scintillator according to claim 8. [Claim 15] The scintillator generates a simultaneous time interval resolution of less than 200 picoseconds. The scintillator according to claim 8. [Claim 16] The scintillator according to claim 1, wherein the trivalent ion substitution A and the divalent ion substitution B alter the cerium ion distribution of the cerium-doped rare-earth oxyorthosilicate and cause it to predominantly occupy the Ce1 crystallographic site. [Claim 17] The trivalent ion substitution A and the divalent ion substitution B replace the cerium ions of the cerium-doped rare earth oxyoltosilicate with Ce 4+ The scintillator according to claim 8, which predominantly changes the charge state. [Claim 18] A method for producing rare earth oxyoltosilicate scintillators: In the manufacturing process, the following equation (1): Lu 2(1-a-b-c-d) A 2a B 2b C 2c D 2d Si (1-x+y) E y O 5(1-z) (1) Here, in the formula, Lu is lutetium, A comprises a trivalent ion substitution selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Sc, Y, Al, Ga, B, In, Bi, Sb, Au, Rh, or combinations thereof, B comprises a non-trivalent ion substitution selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof, and C is Ce 3+ Ce 4+ , Pr 3+ The cation substitution includes an activated cation substitution selected from a combination thereof, where D is a monovalent halogen anion selected from F, Cl, Br, or a combination thereof, where E is a trivalent ion substitution selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or any combination thereof, where a is present in an amount of 0.5 ≤ a ≥ 0, b is present in an amount of 0.5 ≤ b ≥ 0, c is present in an amount of 0.5 ≤ c ≥ 0.00001, d is present in an amount of 0.5 ≤ d ≥ 0, x is present in an amount of 0.05 ≤ x ≥ 0, y is present in an amount of 0.05 ≤ y ≥ 0, z is present in an amount of 0.2 ≤ z ≥ 0, the sum of a + b is always greater than 0, the sum of a + b + c + d is always less than 1, and A and C cannot be the same trivalent cation at the same time. Using a mixture of raw materials to produce the composition, The aforementioned raw materials are melted in a crucible at a temperature of 1500°C to 2300°C, and, Crystals are pulled from the molten material in an oxygen-containing atmosphere using one of the following methods: the Czochralski method, the Bridgman method, the Cairopolos method, or the Bernoulli method. A method that includes doing so. [Claim 19] The method according to claim 18, further comprising annealing the rare earth oxy-olt silicate scintillator in an oxygen-containing environment at a temperature of 1200 to 1800°C for 10 to 80 hours. [Claim 20] The method according to claim 18, wherein the molar ratio of trivalent ion-substituted A to activated cation-substituted C is greater than 3:1, and the molar ratio of non-trivalent ion-substituted B to activated cation-substituted C is greater than 1.5:

1. [Claim 21] The method according to claim 18, wherein the molar ratio of trivalent ion substitution A to activated cation substitution C is greater than 5:1, and the molar ratio of non-trivalent ion substitution B to activated cation substitution C is greater than 2:

1. [Claim 22] A radiation detector using the scintillator described in claim 1. [Claim 23] A radiation detector according to claim 22, used in positron emission tomography or time-of-flight positron emission tomography.

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