Scintillator crystals, methods of manufacture thereof, and articles comprising same

Abstract

Disclosed herein is a rare earth oxyorthosilicate crystal of formula (1) Lu2 (1-a-b-c-d) A2aB2bC2c D2 dSi (1-x + y) EyO5 (1-z) (1) wherein Lu is lutetium; a comprises a trivalent ion substitution selected from the group consisting 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 comprises a non-trivalent ion substitution selected from the group consisting of Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or a combination thereof; c comprises an activating cation substitution selected from Ce < 3 + >, Ce < 4 + >, Pr < 3 + >, or a combination thereof; d comprises a monovalent halogen anion substitution selected from F, Cl, Br, or a combination thereof; e comprises a trivalent ion substitution selected from the group consisting of La, Sc, Y, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or any combination thereof.

Description

[0001] background This disclosure relates to scintillator crystals, methods of manufacturing the same, and articles comprising the same. In particular, this disclosure relates to scintillator materials for detecting ionizing radiation in nuclear imaging applications, particularly PET (positron emission tomography), TOF PET (time-of-flight positron emission tomography), and / or DOI TOF PET (interactive depth time-of-flight positron emission tomography) imaging.

[0002] Lutene oxide orthosilicate (LSO) or cerium oxide (Ce) 3+ Activated Lu₂SiO₅ 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. At least in part due to its relatively high light output 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 made from single-crystal LSOs grown from melt using processes such as the Czochralski process. For scintillator applications, it is generally desirable to grow large single crystals of LSOs with specific scintillation performance parameters. The composition, size, and quality of the grown crystal can be significantly affected by growth stability.

[0004] Despite the successful development of LSO scintillators with different dopants and co-doped schemes, ongoing efforts are being made to develop rare-earth oxygen orthosilicate scintillators with different concentrations of selected equivalent and heterovalent substitutions to improve scintillation properties for specific applications.

[0005] Overview Rare-earth oxygen orthosilicate scintillators are commonly used in medical diagnostic applications, particularly in time-of-flight positron emission tomography (TOF).

[0006] Selective alteration of the molar ratio of polyvalent substituents in the scintillation composition of rare-earth oxygen orthosilicate crystals can result in crystals exhibiting significantly increased scintillation output, improved energy resolution, coincidence time resolution, scintillation rise time, and decay time characteristics compared to compositions activated only with cerium and / or praseodymium without polyvalent substitution. Polyvalent ions can be incorporated into the lattice at relatively low concentrations, typically at commonly used doping and co-doping levels (below 1 atomic%). Such substitution can lead to Ce... 3+ and Ce 4+ Changes in concentration ratio and Ce in the crystal lattice 4+Stabilization is used to improve scintillation performance. Multivalent ions can also be incorporated at much higher concentrations, where they become integral components of the modified scintillator host lattice with different translational symmetries. By selecting a specific molar concentration ratio of multivalent ions, the size of the crystal lattice units and, in some cases, their deformation can be controlled to influence the segregation of certain ions from the melt during crystal growth, as well as to alter the charge state of these ions and their positions in the crystallization sites.

[0007] The rare-earth oxygen orthosilicate compositions described in this invention provide a significant improvement in the time-of-flight resolution of PET systems.

[0008] This paper discloses a rare earth oxygen orthosilicate crystal with 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) Where Lu is lutetium; A includes trivalent ions 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 includes non-trivalent ions selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof; C includes ions selected from Ce... 3+ Ce 4+ Pr 3+ Activated cations or combinations thereof; D contains monovalent halide anions selected from F, Cl, Br or combinations thereof; E contains trivalent ions selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh or any combination thereof; a With 0.5 ≤ a Quantities ≥ 0 exist; b With 0.5 ≤ b Quantities ≥ 0 exist; c With 0.5 ≤ c A quantity ≥ 0.00001 exists; d With 0.5 ≤ d Quantities ≥ 0 exist; x With 0.05 ≤ x Quantities ≥ 0 exist; y With 0.05≤ y Quantities ≥ 0 exist; z With 0.2 ≤ z Quantities ≥ 0 exist; among them a + bThe sum is always greater than 0; and among them a + b + c + d The sum is always less than 1; and A and C cannot be the same trivalent cation at the same time.

[0009] This article also discloses a method for manufacturing rare earth oxygen orthosilicate crystals, which includes manufacturing a powder having the composition of 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) Where Lu is lutetium; A includes trivalent ions 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 includes non-trivalent ions selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof; C includes ions selected from Ce... 3+ Ce 4+ Pr 3+ Activated cations or combinations thereof; D contains monovalent halide anions selected from F, Cl, Br or combinations thereof; E contains trivalent ions selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh or any combination thereof; a With 0.5 ≤ a Quantities ≥ 0 exist; b With 0.5 ≤ b Quantities ≥ 0 exist; c With 0.5 ≤ c A quantity ≥ 0.00001 exists; d With 0.5 ≤ d Quantities ≥ 0 exist; x With 0.05 ≤ x Quantities ≥ 0 exist; y With 0.05≤ y Quantities ≥ 0 exist; z With 0.2 ≤ z Quantities ≥ 0 exist; among them a + b The sum is always greater than 0; and among them a + b + c + d The sum of all ions is always less than 1; and 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 crystals are pulled from the melt using the Czeklaussky technique or a similar technique. Brief description of the attached diagram Figure 1 It is a graph depicting the afterglow of samples A, B, C, and LSO references; Figure 2 It is a graph depicting the energy spectra of different compositions A, B, C and LSO references; Figure 3 Describe the coincidence resolution times of samples A, B, C, and the LSO reference; Figure 4 The results show that, compared with sample D (standard reference), the relative concentration of oxygen vacancies (thermoluminescence peak above 300 K) is significantly reduced in sample A. Figure 5 Describe the thermal response of samples A–D; Figure 6 Depict the radioluminescence of selected samples A–D; and Figure 7 Depicting Ce of selected samples A–D 3+ Ce 4+ Optical absorption spectrum.

[0011] Detailed Explanation definition Rise time is the time interval during which the amplitude rises from 10% of its maximum value to 90% of the light pulse after the absorption of the gamma photon.

[0012] A scintillating 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 a scintillator is defined as the time after which the intensity of the light pulse returns to 1 / e of its maximum value.

[0013] The light output (number of photons / MeV of absorbed gamma energy in the scintillator) of most scintillators is a function of temperature. This is caused by the fact that in scintillating crystals, radiative transitions responsible for producing scintillating light compete with non-radiative transitions (which do not produce light).

[0014] Coincidence time resolution (CTR) and coincidence resolution time (CRT) are commonly used interchangeable terms in positron emission tomography (PET).

[0015] This article discloses a rare-earth oxygen orthosilicate scintillator composition (hereinafter referred to as the scintillator composition), in which the ratio of trivalent, divalent and monovalent ions incorporated into the lattice as equivalent and heterovalent substitutions allows the obtained scintillator single crystal to exhibit a significant increase in scintillator output, improved energy resolution, temporal resolution, decay time and rise time characteristics compared with compositions activated only with cerium and / or praseodymium without multivalent substitutions.

[0016] Multivalent ions can be incorporated into the crystal lattice at relatively low concentrations, typically at commonly used doping and co-doping levels (below 1 atomic%). Several such substitutions can result in Ce... 3+ and Ce 4+ Changes in concentration ratio and Ce in the crystal lattice 4+ Stabilization improves scintillation performance. Further consequences of such substitution can lead to variations in the relative number of Ce1 and Ce2 crystallization sites. Multivalent ions can also be incorporated at much higher concentrations, becoming integral components of the modified scintillator host lattice with different translational symmetries.

[0017] By selecting a specific molar ratio of multivalent ions in rare-earth oxygen orthosilicates, the size of the crystal lattice units and, in some cases, their deformation can be controlled to influence the segregation of certain ions from the melt during crystal growth, as well as to alter the charge state of these ions and their positions at crystallization sites. The properties of the rare-earth oxygen orthosilicate compositions described in this disclosure provide significant improvements in time-of-flight PET systems in terms of time resolution. This disclosure particularly relates to the control of the decay time, rise time, and scintillation output of rare-earth oxygen orthosilicates in terms of time resolution.

[0018] This invention relates to methods for preparing rare-earth oxygen orthosilicate crystals grown from melt using the Czeklauski method or other similar methods, some of which are described in detail below. The melt composition comprises carefully selected molar ratios of added multivalent ions. These ratios are calculated relative to the molar concentrations of activator co-dopersants such as cerium and / or praseodymium. The melt composition and growth process control parameters have a direct impact on the thermodynamics of the crystal growth process, altering Marangoni flow, as well as thermal convection, evaporation losses, and thermal decomposition of the melt at different stages of growth. Therefore, the stoichiometry of the grown crystal can differ significantly from the composition of the original melt.

[0019] The lattice symmetry of the resulting crystal can be altered by adding certain equivalent and heterovalent cations and anions to the melt based on their ionic radii and electronic charge states. These modifications cause the lattice sites to stretch or contract, thus disrupting the periodic symmetry of the crystal. The presence of these modified lattice sites affects the incorporation of dopants and co-dops in their direct vicinity. Ionic radii can influence the segregation of certain dopants and co-dops from the melt within the lattice. It is then advantageous to increase the concentration of certain dopants and co-dops that affect the scintillation properties of the material and limit the concentration of others, solely to alter the thermodynamics of the crystallization process.

[0020] The selection of preferred equivalent and heterovalent ions at a predetermined relative concentration ratio results in: • The change in the concentration of ions placed in the crystal lattice during the crystal growth process. • By altering the distribution of trivalent and divalent ions at different crystallization sites within rare earth sites and oxygen orthosilicate crystals, as well as in interstitial sites compensating for oxygen vacancy defects, • By altering the relative spatial distribution of trivalent and divalent ions, certain predetermined clusters of divalent, trivalent, and activator ions can be formed. • It affects the electronic charge state of ions incorporated into rare earth oxygen orthosilicate lattices, especially the charge state ratio of cerium 3+ and 4+ in both Ce1 and Ce2 crystallization sites. • Control the number of cerium ions at both Ce1 and Ce2 crystallization sites.

[0021] In the thermodynamics of the growth process, there exists a statistical probability of causing defects of specific ions and thus charge state imbalances in the lattice, in order to control the incorporation of selected ion substitutions that are conducive to restoring the charge balance in the lattice at certain crystallization sites (which may be rare earth sites, oxygen orthosilicate sites, or interstitial sites).

[0022] Monovalent elements with trivalent cations, such as: 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+ It can primarily replace the rare earth components in rare earth oxygen orthosilicate lattices. B 3+ Al 3+ In 3+ Ga 3+ Sb 3+ Au 3+ Bi 3+ ,Rh 3+ It can primarily replace the missing SiO2 in the crystal lattice of rare-earth oxygen orthosilicates. 4- Si in ionic complex 4+ These defects can result from stoichiometric losses (which may be attributed to intentional compositional choices), the selection of growth process parameters, or losses due to evaporation and decomposition during the growth process.

[0023] Monovalent elements with divalent cations, such as Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Zn 2+ Cd 2+ Ni 2+ It can replace and compensate for rare earth oxygen orthosilicate oxygen vacancies generated during the growth process.

[0024] Anions, such as: F -1 Cl -1 ,Br -1 O -2 Can be used as Ce 3+ or Ce 4+ Commercial chemical variants of the activator are added indirectly. These are typically available commercially 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] The monovalent elements with trivalent cations mentioned above include 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 cause the crystal lattice of rare-earth oxygen orthosilicate units to expand or contract. Cerium activators added to the melt can be incorporated into the lattice near these ions. Therefore, the surrounding environment of cerium can create favorable conditions for cerium to change its charge state from 3+ to 4+. The 4+ state of cerium results in faster decay and rise times in scintillation emission. Divalent ions, such as Mg... 2+ Ca 2+ and Sr 2+ They can also be incorporated into certain lattice sites based on their ionic radii. They can be modified by changing Ce... 3+The number of two crystalline sites in the oxygen orthosilicate lattice is used to advantageously alter the scintillation properties of rare-earth oxygen orthosilicate scintillators. One of these sites produces fast scintillation emission with a decay time of less than 40 nanoseconds (ns), while the other produces slow scintillation emission with a decay time of more than 40 ns. Another result of these substitutions is charge state compensation.

[0026] The addition of certain concentrations of SiO2 can be used to compensate for melt incongruity that occurs in an oxygen-deficient environment during crystal growth. SiO2 acts as the orthosilicate anion. 4- Incorporating into the lattice. Due to the volatility of SiO / SiO2 evaporation loss, rare-earth oxygen orthosilicate melts can partially decompose under high temperatures and oxygen-deficient atmospheres. Oxygen deficiency in the melt caused by the decomposition of melt components can create thermally reversible defects, such as oxygen vacancies in the resulting lattice. These can be addressed during and after growth by controlled addition of oxygen at elevated temperatures and by introducing divalent ions, such as those mentioned earlier (e.g., Mg). 2+ Ca 2+ 、Sr 2+ Or Ba 3+ It is incorporated into the lattice to compensate.

[0027] Y 3+ Gd 3+ Al 3+ Ga 3+ In 3+ Or B 3+ The use of the other trivalent cations listed above at selected concentration ratios relative to the cerium activator concentration can compensate for SiO₂ 4- Si at the complex site 4+ and O 2- The loss. The selected trivalent cations replace Si. 4+ This causes an imbalance in the charge state. From Ce 3+ Electron transfer to the complex brings stability to Ce. 4+ The state is restored and the charge balance is restored.

[0028] In one embodiment, the scintillation composition comprises a rare-earth oxygen orthosilicate described by the 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) Where Lu is lutetium; A includes trivalent ionic compounds (substitutions) containing rare earth metals 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 includes non-trivalent (e.g., monovalent or divalent) ionic compounds (substitutions) selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof; C includes trivalent dopant (activated) cation substitutions, such as Ce. 3+ Ce 4+ Pr 3+ Ions or combinations thereof; D contains monovalent halide anions; E contains elements selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh or combinations thereof; a With 0.5 ≤ a Quantities ≥ 0 exist; b With 0.5 ≤ b Quantities ≥ 0 exist; c With 0.5 ≤ c A quantity ≥ 0.00001 exists; d With 0.5 ≤ d Quantities ≥ 0 exist; x With 0.05 ≤ x Quantities ≥ 0 exist; y ≤ 0.05 y Quantities ≥ 0 exist; z With 0.2 ≤ z Quantities ≥ 0 exist; among them a + b The sum is always greater than 0; and among them a + b + c + d The sum is always less than 1. In one implementation, a、 b, c and d Each of the values ​​in the set is not simultaneously equal to 0.25 or greater, and a + b + c + d The maximum value of the sum ranges from 0.00001 to 0.4, preferably between 0.00015 and 0.35; and x≥y In one implementation, in equation (1) b:c The ratio can be from 1:1 to 10:1, preferably from 2:1 to 5:1, while in formula (1) a:c The ratio can be from 2.5:1 to 15:1, preferably from 4:1 to 10:1.

[0029] In equation (1), the term “x” represents silicon dioxide loss and is always greater than “y”, where y represents substitution by element E. The term “z” represents oxygen loss during manufacturing and implies 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, 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; C comprises a trivalent ion substitution selected from Ce 3+ Ce 4+ Pr 3+ Activated cation substitutions of or combinations thereof; D contains monovalent halide anion substitutions selected from F, Cl, Br or combinations thereof; E contains trivalent ion substitutions selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh or any combination thereof (for silicon dioxide). a With 0.5 ≤ a Quantities ≥ 0 exist; b With 0.5 ≤ b Quantities ≥ 0 exist; c With 0.5 ≤ c A quantity ≥ 0.00001 exists; d With 0.5 ≤ d Quantities ≥ 0 exist; x With 0.05 ≤ x Quantities ≥ 0 exist; y With 0.05≤ y Quantities ≥ 0 exist; z With 0.2 ≤ z Quantities ≥ 0 exist; among them a + b The sum is always greater than 0; and among them a + b + c + d The sum is always less than 1; and A and C cannot both be the same trivalent cation. In one embodiment, A, C, and E cannot both be the same trivalent cation. In another embodiment, the content of ion-substituted E (for Si) is determined by... x≥y definition.

[0031] In one embodiment, the rare-earth oxygen orthosilicate 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 combinations 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 combinations thereof; C is Ce 3+ Ce 4+ Pr 3+Or a combination thereof; while D is a monovalent halide anion, such as, for example, F, Cl, Br or a combination thereof.

[0032] In one implementation, A and C cannot both be the same trivalent cation. For example, if A is a trivalent cation of Ce (e.g., Ce... 3+ If C is a tetravalent cation of Ce (e.g., Ce), then C will be a tetravalent cation of Ce (e.g., Ce). 4+ ) or trivalent cations of Pr (e.g., Pr 3+ In some implementation schemes, a The amount is from 0.000001 to 0.25, preferably from 0.001 to 0.2, preferably from 0.01 to 0.15, and most preferably from 0.05 to 0.1. In some embodiments, b The amount is from 0.000001 to 0.25, preferably from 0.001 to 0.2, preferably from 0.01 to 0.15, and most preferably from 0.05 to 0.1. In some embodiments, c The amount is 0.00002 to 0.35, preferably 0.001 to 0.3, preferably 0.002 to 0.2, preferably 0.01 to 0.15, and preferably 0.05 to 0.1. In some embodiments, d The amount is 0.00002 to 0.35, preferably 0.001 to 0.3, preferably 0.002 to 0.2, preferably 0.01 to 0.15, and preferably 0.05 to 0.1. In some embodiments, x The amount is 0.00002 to 0.05, preferably 0.001 to 0.05, preferably 0.002 to 0.04, preferably 0.01 to 0.03, and preferably 0.02 to 0.025. In some embodiments, y The amount is 0.00002 to 0.05, preferably 0.001 to 0.04, preferably 0.002 to 0.03, preferably 0.01 to 0.025, and preferably 0.015 to 0.025. In some embodiments, z The amount is 0.00002 to 0.05, preferably 0.001 to 0.04, preferably 0.002 to 0.03, preferably 0.01 to 0.025, and preferably 0.015 to 0.025.

[0033] In some implementations, trivalent ions (which are not activated cations C), such as La 3+ 、Nd 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ Ho 3+ Er 3+ Tm 3+ Yb 3+ ,Sc3+ Y 3+ Al 3+ Ga 3+ B 3+ In 3+ Bi 3+ ,Rh 3+ Au 3+ Sb 3+ The addition of cerium, or combinations thereof, at a higher concentration, incorporates it into the crystal lattice and can cause the crystal lattice units to expand or contract as described above. In other words, it is not the trivalent ions of the activated cation C that cause the size change of the crystal lattice units. Therefore, the surrounding environment of cerium can create favorable conditions for cerium to change its charge state from 3+ to 4+, and this has a positive effect on the scintillation properties of the crystal. In other words, when the nearest neighbor of the activated cation C is one of a trivalent ion class A (e.g., trivalent cation A) or a non-trivalent ion class B (e.g., monovalent or divalent cation B), the activated cation C changes its charge state from 3+ to 4+.

[0034] Cerium in its 4+ state causes a faster decay time component in scintillation emission. Divalent ions, such as Mg... 2+ Ca 2+ 、Sr 2+ and Ba 2+ They can be incorporated into certain lattice sites based on their ionic radii. They can be incorporated by changing Ce... 3+ The number of two crystallization sites in the rare-earth oxygen orthosilicate lattice can be used to advantageously alter the scintillation properties of the rare-earth oxygen orthosilicate scintillator. One of these sites produces fast scintillation emission with a decay time of less than 40 nanoseconds (ns), while the other produces slow scintillation emission with a decay time of more than 40 ns.

[0035] In one embodiment, the molar ratio of trivalent cation A to activated ion C (in formula (1)) 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 mentioned 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 to the activated cation C (in formula (1)) is greater than 1:1, preferably greater than 1.5:1, preferably greater than or equal to 2:1, preferably greater than or equal to 3:1, preferably greater than or equal to 4:1, and more preferably greater than or equal to 5:1. In one embodiment, it may be desirable to simultaneously incorporate at least one trivalent cation A (in addition to the activated trivalent or tetravalent cation C) and at least two different monovalent or divalent cations into the crystal lattice.

[0037] In a preferred embodiment, it may be desirable to use relative to the activated cation C (selected from Ce)3+ Ce 4+ Pr 3+ The molar ratio of at least one trivalent cation A (selected from La) is at least 1:1, preferably at least 5:1, and more preferably at least 10:1. 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), and simultaneously incorporate at least two cations (selected from Mg) 2+ Ca 2 + 、Sr 2+ Ba 2+ Na 1+ K 1+ 、Rb 1+ Mn 2+ Mn 4+ Mn 7+ Cu 2+ Cu 1+ Zn 2+ (or combinations thereof), each having 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 cerium ion distribution in cerium-doped rare-earth oxygen orthosilicates to predominantly occupy Ce1 crystallization sites. In another embodiment, trivalent ion substitution A and divalent ion substitution B alter the cerium ion distribution in cerium-doped rare-earth oxygen orthosilicates to predominantly occupy Ce1 crystallization sites. 4+ Charge state.

[0039] In one embodiment, in a method for manufacturing a single crystal, a powder of raw material is placed in a crucible and heated using induction heating. The average particle size of the powder ranges from 5 nanometers to 500 micrometers, preferably from 10 nanometers to 50 micrometers, and more preferably from 1 to 20 micrometers. The radius of gyration of the particles is measured to determine the average particle size. Light scattering or electron microscopy can be used to determine the particle size.

[0040] In one embodiment, nano and / or micron-sized particles can be manufactured (or purchased separately) and blended together to form the composition of formula (1) above. For example, nano and / or micron-sized powders of rare earth oxygen orthosilicates can be blended with other particles (e.g., metal oxide particles, dopant particles) in desired stoichiometric amounts to form an intimate mixture. This intimate mixture is then heated to the temperature described in detail below to form a single crystal. In other words, nano and / or micron-sized metal oxide powders of Lu, A, B, C, and silicon dioxide (from formula (1)) can be blended with halides of C (if desired) to produce an intimate mixture, which is then heated as described in detail below to form a single crystal.

[0041] In one embodiment, nano- or micro-sized lutetium oxide powder is added to the dopant or mixer in the stoichiometric ratios detailed above. Nano- or micro-sized metal oxide powder or metal salts (e.g., oxides or salts of Lu, A, and B) are added to the dopant or mixer in the stoichiometric amounts listed above. Nano- or micro-sized silica may also be added to the dopant or mixer. Activated cation C (also called a dopant) (also nano- or micro-sized particles) may be added to the dopant or mixer in the form of a salt (e.g., a metal halide) or as a metal oxide. Other reactants listed above may also be added to the dopant or mixer. The powder thus added to the dopant or mixer is then blended to form a close mixture.

[0042] The powder obtained from this close mixture can be first mixed and optionally further pulverized by grinding. If it is desired to use particles of a specific size, the pulverized powder can then be subjected to an optional sieving process.

[0043] The powder used to manufacture rare earth oxygen orthosilicates is then melted in an oxygen-containing atmosphere at a temperature of 1500°C to 2300°C, preferably 1800°C to 2200°C, to prepare polycrystalline or single-crystal materials that can be used as scintillators in the next stage.

[0044] Single crystals can be prepared using the Czeklauski method, Bridgman technique, Kyropoulos technique, and Verneuil technique.

[0045] In the Czeklaussky process, the powder to be grown is melted in a suitable non-reactive vessel under a controlled atmosphere. The material is melted by controlling the furnace temperature to a maximum of 2100°C. A seed crystal is lowered to contact the molten charge for nucleation. The nucleated seed crystal is then pulled out of the melt at a controlled rate. This method can be used to grow large-diameter crystals.

[0046] In the Bridgman (pulling method) technique, material is melted in a vertical cylindrical container (called an ampoule) that tapers to a pointed apex. The container is slowly lowered from the hot zone of a furnace at a temperature up to 2100°C into a cold zone. The movement rate of this process ranges from approximately 1 to 30 mm / hr. Crystallization begins at the tip and typically continues by growth from the initially formed nuclei. Due to the orientation of the casting and the controlled cooling process, oriented lattice regions are formed. In other words, single crystals can be produced.

[0047] In the Kyropoulos technique, the crystal grows with a larger diameter than in the two methods mentioned above. As in the Czeklaussky process, the seed crystal is also brought into contact with the melt and is not raised too much during growth; that is, a portion of the seed crystal is allowed to melt and grow a short, narrow neck. Thereafter, the vertical movement of the seed crystal is stopped, and growth continues by reducing the power input to the melt.

[0048] In the Verneuil technique (flame melting), fine dry powder of the material to be grown, ranging in size from 1 to 20 micrometers, is agitated through a wire mesh and allowed to fall through an oxyhydrogen flame. The powder melts and forms a liquid film on top of the seed crystal. This film gradually freezes as the seed crystal slowly descends. The technique involves balancing the charge feed rate and the seed crystal descent rate to maintain a constant growth rate and diameter.

[0049] In one embodiment, rare earth oxygen orthosilicate crystals are annealed in an oxygen-containing environment at a temperature of 1200 to 1800°C for a period of 10 to 80 hours, wherein the oxygen-containing environment contains more than 1% by weight of oxygen.

[0050] Compared to rare-earth oxygen orthosilicate crystals without polyvalent cation substitution, the rare-earth oxygen orthosilicate crystals disclosed herein exhibit increased light output. For example, rare-earth oxygen orthosilicate crystals without polyvalent cation substitution exhibit light output of less than 24,000 photons / MeV (ph / MeV), while rare-earth oxygen orthosilicate crystals with polyvalent cation substitution exhibit light output greater than 25,000 ph / MeV, preferably greater than 27,000 ph / MeV, more preferably greater than 30,000 ph / MeV, more preferably greater than 31,000 ph / MeV, more preferably greater than 33,000 ph / MeV, and more preferably greater than 34,000 ph / MeV.

[0051] In one embodiment, rare-earth oxygen orthosilicate crystals containing polyvalent ion substitutions disclosed herein exhibit light decay times of less than 35 nanoseconds, preferably less than 33 nanoseconds, and more preferably less than 30 nanoseconds. Conversely, single crystals without polyvalent cation substitutions have decay times greater than 42 nanoseconds.

[0052] In one embodiment, rare-earth oxygen orthosilicate crystals containing the polyvalent cations substituted herein exhibit an energy resolution percentage of 6.5% to 8.5%, preferably 6.75% to 7.50%, at 511 keV. Rare-earth oxygen orthosilicate crystals not containing the polyvalent cations substituted herein exhibit an energy resolution percentage of greater than 9.4% at 511 keV.

[0053] The rare earth oxygen orthosilicates disclosed herein are illustrated by the following non-limiting examples. Example

[0054] Example 1 This example demonstrates the advantages of multivalent ion (tetravalent, trivalent, and divalent cation) substitution in rare earth oxygen orthosilicates. Various trivalent cations (Y, Yb, Sc, Dy, and La) with Ce were prepared in a 10:1 ratio using the Czeklauski method. 3+ The molar ratio of cations and the presence of two or more cations each having a 2:1 ratio with Ce 3+ Rare earth oxygen orthosilicate crystals with divalent cations (Mg and Ca) in molar ratio. The ratios specified above are in the molten state. Properties are shown in Table 1 below.

[0055] Table 1 .

[0056] Using Ce 3+ The reference composition, co-doped and without any multivalent ions, exhibited a coincidence 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 persistence. In contrast, rare-earth oxygen orthosilicate crystals containing multivalent ion substitutions (as shown in Table 1) exhibited CRTs of 105 to 120 picoseconds and measured absolute optical outputs.

[0057] Example 2 This example demonstrates the linearity of samples A and B, which are detailed below.

[0058] Sample A – a multivalent composition of Formula 1, measured relative to Ce after thermal post-processing. 3+ The divalent cation substitution ratio is Mg 2:1, Ca 2:1.

[0059] Sample B - LSO Mg 0.25:1 ratio measured after heat treatment. Tables 2 and 3 show the linearity of samples A and B, respectively.

[0060] Table 2 *Nphe is the number of photoelectrons. *NpheMeV is the number of photoelectrons per MeV.

[0061] Table 3 The composition of Formula 1 exhibits good energy linearity and energy resolution over a wide range of excitation energies.

[0062] Example 3 These examples demonstrate the various properties of the following compositions. Samples A, B, and C presented in the figure below depict different compositions derived from formula (1) using different selected substitutions.

[0063] Sample A - a composition of formula (1) after heat treatment, thereby undergoing divalent ion substitution relative to Ce after annealing in an oxygen-rich atmosphere. 3+ The molar ratios are as follows: Mg 2:1, Ca 2:1.

[0064] Sample B - LSO 0.25:1 heat-processed composition of formula (1), whereby divalent ions are substituted relative to Ce. 3+ The molar ratios are as follows: Mg 0.25:1.

[0065] Sample C - a composition of formula (1) after heat treatment, thereby achieving divalent ion substitution relative to Ce without heat treatment. 3+ The molar ratios are as follows: Mg 2:1, Ca 2:1.

[0066] Samples D and "ref" are rare-earth oxygen orthosilicate materials without additional polyvalent ion substitution. The properties of these rare-earth oxygen orthosilicates (samples A, B, C, D, and "ref") show... Figure 1-7 middle.

[0067] Figure 1 This is a graph depicting the afterglow. Sample A, containing polyvalent substitutions and after thermal post-processing, exhibits the lowest afterglow.

[0068] Figure 2 This is a graph depicting the energy spectrum measured under 662 keV excitation. Sample B exhibits the best relative light output.

[0069] Figure 3The coincidence resolution time (CRT) of various samples was plotted. Sample A exhibited the best relative CRT.

[0070] Figure 4 This shows the relative concentration of oxygen vacancies (thermoluminescence peak above 300 K). Compared to sample D (standard reference), this concentration is significantly lower in sample A.

[0071] Figure 5 The thermal response of the compositions detailed above is depicted. Compared to sample C, sample A exhibits significantly better light output stability at temperatures above 300 K, indicating improved material properties following thermal post-growth processing.

[0072] Figure 6 The radiative emission of the selected compositions was depicted. Compared to sample D (comparative standard), sample A exhibited a slight shift in the UV range, indicating an increase in the number of Ce1 sites relative to the reduced number of Ce2 sites. This effect explains the shorter scintillation emission in the new composition.

[0073] Figure 7 The absorption of the material of formula (1) with different levels of trivalent and divalent substitution ratios is depicted. Higher concentrations of Ce... 4+ It exhibits strong charge transfer Ce in the range of 220 nm to 350 nm. 4+ O 2- absorb.

[0074] Although the invention has been described with reference to some embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for its elements without departing from the scope of the invention. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the invention without departing from its essential scope. Therefore, the invention is not intended to be limited to the specific embodiments disclosed as the best mode for carrying out the invention, but rather the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A rare earth oxyorthosilicate scintillator composition having 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) wherein Lu is Lutetium; A comprises 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 non-trivalent ion substitution selected from Mg, Ca, Sr, Ba, Li, Na, K, Rb, Mn, Cu, Zn, or combinations thereof; C comprises activating cation substitution selected from Ce 3+ , Ce 4+ , Pr 3+ , or combinations thereof; D comprises monovalent halide anion substitution selected from F, Cl, Br, or combinations thereof; E comprises 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; wherein a + b the sum of always is greater than 0; and wherein a + b + c + d the sum of always is less than 1; and wherein A and C cannot be the same trivalent cation at the same time.

2. The scintillator of claim 1, wherein a, b, c and d each have a value that is not equal to 0.25 or greater, and wherein a + b + c + d the sum of the values ranges from 0.00001 to 0.

4.

3. The scintillator of 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 combinations thereof.

4. The scintillator of claim 3, wherein B is a monovalent or divalent cation selected from Mg, Ca, Sr, Ba, Na, K, Rb, Mn, Cu, Zn, or combinations thereof; and wherein D is an anion of F, CI, Br, or combinations thereof.

5. The scintillator of claim 1, wherein if A is a trivalent cation of Ce (Ce 3+ ), then C will be a tetravalent cation of Ce (Ce 4+ ) or a trivalent cation of Pr (Pr 3+ ).

6. The scintillator of claim 1, wherein trivalent ions other than the activating cation C induce a dimensional change in the lattice.

7. The scintillator of claim 4, wherein when the activating cation C is initially Ce 3+ when its nearest neighbor is a trivalent ion substitution A and a non-trivalent ion substitution B, its charge state is changed from Ce 3+ to Ce 4+ .

8. The scintillator of claim 1, wherein the molar ratio of trivalent ion substitution A to activating cation C is greater than 0.1 : 1, and wherein the molar ratio of non-trivalent ion substitution B to activating cation C is greater than 1 :

1.

9. The scintillator of claim 8, wherein the content of ionically substituted E is defined by x > y E < 0.

005.

10. The scintillator of claim 1, wherein the molar ratio of trivalent ion substitution A to activating cation substitution C is greater than 5: 1, and wherein the molar ratio of non-trivalent ion substitution B to activating cation substitution C is greater than 2:

1.

11. The scintillator of claim 1, wherein A comprises at least one trivalent cation in the lattice, and wherein B comprises at least two different non-trivalent cations.

12. The scintillator of claim 11, wherein the trivalent cation substitution A is selected from 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 combinations thereof, at a molar ratio of at least 10: 1 relative to the activating cation substitution C, and wherein the non-trivalent cation substitution B is selected from Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Na 1+ , K 1+ , Rb 1+ , Mn 2+ , Cu 2+ , Cu 1+ , Zn 2+ or combinations thereof, each at a molar ratio of at least 2: 1 relative to the activating cation substitution C.

13. The scintillator of claim 1, wherein the scintillator produces a light output greater than 25,000 ph / MeV.

14. The scintillator of claim 8, wherein the scintillator produces a light decay less than 35 nanoseconds.

15. The scintillator of claim 8, wherein the scintillator produces a coincidence resolving time less than 200 picoseconds.

16. The scintillator of claim 1, wherein trivalent ion substitution A and divalent ion substitution B alter the cerium ion distribution of the cerium-doped rare earth oxyorthosilicate to predominantly occupy the Cel crystalline site.

17. The scintillator of claim 8, wherein the trivalent ion substitution A and the divalent ion substitution B change the cerium doped rare earth oxyorthosilicate cerium ions to predominantly Ce 4+ Charge state.

18. A method of making a rare earth oxyorthosilicate scintillator, comprising: a mixture of raw materials that yields a composition of formula (1) in the method of manufacture: 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) wherein 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; C comprises an activating cation substitution selected from Ce 3+ , Ce 4+ , Pr 3+ , or combinations thereof; D comprises a monovalent halide anion selected from F, Cl, Br, or combinations thereof; E comprises a trivalent ion substitution selected from La, Sc, Y, Gd, Al, Ga, In, B, In, Bi, Sb, Au, Rh, or any combination 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; wherein a + b the sum of always is greater than 0; and wherein a + b + c + d the sum of always is less than 1; and wherein A and C cannot be the same trivalent cation at the same time; melting the raw materials in a crucible at a temperature of 1500 °C to 2300 °C; and pulling a crystal from the melt in an oxygen-containing atmosphere using one of Czochralski, Bridgeman, Kyropoulos, and Verneuil techniques.

19. The method of claim 18, further comprising annealing the rare earth oxyorthosilicate scintillator in an oxygen-containing environment at a temperature of 1200 to 1800 °C for a period of 10 to 80 hours.

20. The method of claim 18, wherein the molar ratio of trivalent ion substitution A to activating cation substitution C is greater than 3: 1, and wherein the molar ratio of non-trivalent ion substitution B to activating cation substitution C is greater than 1.5:

1.

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

1.

22. A radiation detector using the scintillator of claim 1.

23. The radiation detector of claim 22, used for positron emission tomography or time-of-flight positron emission tomography.

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