A kind of heterovalent ion co-doped garnet transparent scintillation ceramic and preparation method thereof

Abstract

The present invention belongs to the field of ceramic scintillators, and specifically discloses a heterovalent ion co-doped garnet transparent scintillating ceramic and a preparation method thereof; the ceramic structure has the following general formula: (R x A 3‑x‑ y A y ')(B 5‑z B' z ) 12 ; Wherein: R represents an activating ion and a sensitizer thereof, including at least one of Ce, Pr, Yb, and Cr elements; A is at least one of the rare earth elements Gd, Y, and Lu; A' represents a divalent cation, including at least one of the elements Mg, Ca, Sr, and Ba; B is at least one of the elements Al, Ga, and Sc; B' represents a tetravalent cation Si; x ranges from 0.0005 to 0.1, y ranges from 0.00005 to 0.01, and z ranges from 0.00005 to 0.01. The present invention uses a heterovalent ion to co-replace the balanced charge, so that the ceramic has the characteristics of high light yield, fast decay, and low afterglow. The ceramic is prepared based on a high-energy ball milling method to prepare powder, which is simple in process and can be mass-produced.

Description

Technical Field

[0001] The invention belongs to the field of ceramic scintillators, and specifically discloses a heterovalent ion co-doped garnet transparent scintillating ceramic and a preparation method thereof. Background Art

[0002] Scintillators are a type of material that can convert high-energy rays into visible / ultraviolet light. Based on this property, scintillators are widely used in high-energy physics, nuclear radiation detection, security inspection, medical diagnosis, industrial detection and other fields. Transparent ceramic scintillators are widely studied due to their excellent mechanical and mechanical properties, simple preparation process and low production cost. At the same time, transparent ceramics are more conducive to the preparation of high-doping concentration samples compared to single crystals, so transparent ceramic scintillators have extremely high application prospects.

[0003] In recent years, the research on garnet structure transparent scintillating ceramics has increased. This is because it belongs to the cubic crystal system, and its isotropic crystal structure avoids the scattering and birefringence of the material to the incident light, which is conducive to the preparation of highly transparent ceramics. For example, the Shanghai Institute of Ceramics, Chinese Academy of Sciences, prepared 3mR, 3nR': (A 1-m-n-x A' x )3(B y C 1-y )5O 12 Garnet structure (patent publication number: CN 101514100 B) high optical quality scintillating transparent ceramics, the transmittance of which in the visible light band can reach more than 80%. Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, based on Re x :(A 1-y B y ) m-x (C 1-z D z )8 -m O 12 Garnet structure (patent publication number: CN 103396121 A), adjusting the matrix ions, and preparing a new type of transparent scintillating ceramic by high-energy ball milling combined with multiple sintering methods.

[0004] However, because the radii of the coordinated atoms in the garnet structure are often similar, it is easy to form opposite occupancy, thereby generating antisite defects, resulting in strong afterglow of the scintillator, which affects the device application of the material. In order to solve the afterglow problem of garnet structure materials, relevant researchers and institutions have adopted different methods. The University of Tennessee in the United States optimized the afterglow performance of the scintillator by co-doping monovalent alkali metals in rare earth aluminum garnet (patent publication number: CN 110603310 A). General Motors used divalent ions as dopants (patent publication number: CN 103374351 B) to cause charge compensation, eliminate certain defects in the matrix conduction band, and reduce the afterglow of the material. Although the above work has greatly optimized the afterglow performance of the garnet scintillator, the light yield of the scintillator has also dropped significantly. Now it is necessary to find a solution to synergistically optimize the afterglow and light yield of the garnet scintillator. Summary of the invention

[0005] Based on the deficiencies in the prior art, the present invention discloses a heterovalent ion co-doped garnet transparent scintillation ceramic and a preparation method thereof.

[0006] The present invention includes the following technical solutions:

[0007] A heterovalent ion co-doped garnet transparent scintillating ceramic, the structure of which has the following general formula:

[0008] (R x A 3-x-y A y ')3(B 5-z B' z ) 12 ;

[0009] in:

[0010] R represents an active ion and a sensitizer thereof, comprising at least one of Ce, Pr, Yb, and Cr elements;

[0011] A is at least one of the rare earth elements Gd, Y, and Lu;

[0012] A' represents a divalent cation, including at least one of Mg, Ca, Sr, and Ba;

[0013] B is at least one of Al, Ga and Sc;

[0014] B' represents the tetravalent cation Si;

[0015] The x value range is between 0.0005-0.1, the y value range is between 0.00005-0.01, and the z value range is between 0.00005-0.01.

[0016] Preferably, the above-mentioned a kind of heterovalent ion co-doped garnet transparent scintillating ceramic, x=0.02, y=0.00075, z=0.0005, R is Ce, A is Gd, A' is Mg, B is Al, Ga; the ceramic composition is (Ce 0.02 G 2.97925 Mg 0.00075 )(Si 0.0005 Al 2.99975 Ga 1.99975 ) 12 .

[0017] Preferably, the above-mentioned a kind of heterovalent ion co-doped garnet transparent scintillating ceramic, x=0.02, y=0.005, z=0.0025, R is Ce, Yb, A is Gd, A' is Ca, B is Al, the ceramic composition is (Ce 0.015 Yb 0.005 G 2.975 Ca 0.005 )(Si 0.0025 Al 4.9975 ) 12 .

[0018] Preferably, the above-mentioned a kind of heterovalent ion co-doped garnet transparent scintillating ceramic, x=0.01, y=0.01, z=0.01, R is Ce, A is Gd, Lu, A' is Mg, Ca, B is Al, Ga, the ceramic composition is (Ce 0.01 Lu 0.5 G 2.48 Mg 0.005 Ca 0.005 )(Si 0.01 Al 2.495 Ga 2.495 ) 12 .

[0019] Furthermore, the above-mentioned a kind of heterovalent ion co-doped garnet transparent scintillating ceramic has a cubic garnet structure, isotropy, an average grain size of less than 10μm, and a 1mm thick sample has a visible light transmittance of more than 60%.

[0020] Furthermore, the above-mentioned heterovalent ion co-doped garnet transparent scintillating ceramic has a light yield of 21000ph / MeV~62000ph / MeV and a decay time as low as 24ns.

[0021] The present invention also discloses a method for preparing the above-mentioned heterovalent ion co-doped garnet transparent scintillation ceramic, comprising the following steps:

[0022] 1) Ingredients: Use high-purity oxide raw materials with a purity higher than 99.99%, according to (R x A 3-x-yA y ')(B 5-z B' z ) 12 Precisely weigh the powder according to the general structural formula ratio;

[0023] 2) Ball milling: The powders are mixed evenly based on high-energy ball milling. To avoid the introduction of other impurities, the ball milling jar and ball mill are made of alumina, and ethanol is used as the ball milling medium. To ensure the powders are mixed evenly, the ball milling speed is not less than 200rpm, and the ball milling time is not less than 10h;

[0024] 3) Pre-calcination: The milled slurry is dried and sieved, and pre-calcined at 600-1200°C for 2-8 hours to remove possible organic impurities and obtain a uniform and pure precursor;

[0025] 4) Molding: The green body is formed by a two-step molding method. First, the precursor is dry pressed for more than 1 minute at a pressure of not less than 10Mpa to prepare a green body with a preliminary shape, and then cold isostatic pressing is performed at ≥200Mpa for 2 minutes. At this time, the relative density of the green body should reach more than 55%;

[0026] 5) Sintering: The sintering method of the green blank is also a two-step sintering method. First, pressureless sintering is performed in an oxygen atmosphere at a sintering temperature of 1500°C-1700°C and a holding time of 2h-20h. Then, hot isostatic pressing is performed at a pressure of 140-180Mpa, a sintering temperature of 1500°C-1650°C and a holding time of 2h-4h to obtain a transparent ceramic sample.

[0027] 6) Annealing: In order to eliminate the oxygen vacancies and internal stress generated in the ceramic during the sintering process, the transparent ceramic sample is annealed in air or oxygen atmosphere. The annealing temperature is set at 1000°C-1400°C and the insulation time is 4h-24h.

[0028] Compared with the prior art, the present invention has the following outstanding beneficial effects:

[0029] The invention discloses a heterovalent ion co-doped garnet transparent scintillation ceramic and a preparation method thereof. The prepared transparent scintillation ceramic has a cubic garnet structure, isotropy, an average grain size of less than 10 μm, and a 1 mm thick sample has a visible light band transmittance of higher than 60%. The heterovalent ion co-doped garnet transparent scintillation ceramic prepared by the invention can achieve high light yield, reaching 24000ph / MeV~62000ph / MeV, and a decay time as low as 24ns. In addition, the invention adopts a high-energy ball milling method to prepare the powder, has a simple preparation process, and can achieve mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1The XRD diagrams of Examples 1, 2, 3 and Comparative Example 1 of the present invention are shown, with standard PDF cards attached. It can be seen that the ceramic samples all conform to the garnet structural characteristics and are all pure phases. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] x=0.02, y=0.00075, z=0.0005, R is Ce, A is Gd, A' is Mg, B is Al, Ga, the ceramic composition is (Ce 0.02 G 2.97925 Mg 0.00075 )(Si 0.0005 Al 2.99975 Ga 1.99975 ) 12

[0034] The commercially available micron-grade high-purity raw materials: Al2O3(5N), Gd2O3(5N), Ga2O3(5N), CeO2(5N), (C2H5O)4Si(4N), MgO(4N) ​​were accurately weighed in the above formula according to the stoichiometric ratio. Ethanol was used as the ball milling medium. A high-purity Al2O3 ball mill and corresponding ball mill were used. The ball milling speed was 200 rpm. The slurry was dried and passed through a 200-mesh sieve. The powder was pre-sintered at 800°C for 2h, and then dry-pressed and cold isostatically pressed to prepare a ceramic blank. The blank was first sintered at 1600°C for 10h in an atmosphere furnace with flowing oxygen, and then hot isostatically pressed at 1500°C for 2h. Finally, it was annealed at 1300°C for 10h in an air atmosphere to obtain the ceramic. The XRD of the ceramic sample is as follows Figure 1 As shown, XRD shows that the ceramic is a pure garnet phase, which matches well with the #46-0448 PDF card (ICDD-PDF library). The sample emission peak is located at 552nm, the transmittance of 1mm thick ceramic in the visible light band is greater than 61%, the absolute light output is 52000ph / MeV, the decay time is 64ns, and the 20ms afterglow is less than 0.04%.

[0035] Example 2

[0036] x=0.02, y=0.005, z=0.0025, R is Ce, Yb, A is Gd, A' is Ca, B is Al, the ceramic composition is (Ce 0.015 Yb 0.005 G 2.975 Ca 0.005 )(Si 0.0025 Al 4.9975 ) 12

[0037] The commercially available micron-grade high-purity raw materials: Al2O3(5N), Yb2O3(4N), Gd2O3(5N), CeO2(5N), (C2H5O)4Si(4N), CaO(4N) ​​were accurately weighed in the above formula according to the stoichiometric ratio. Ethanol was used as the ball milling medium. A high-purity Al2O3 ball mill and corresponding ball mill were used. The ball milling speed was 240 rpm. After the slurry was dried, it was passed through a 200-mesh sieve. The powder was pre-sintered at 900°C for 1h, and then dry-pressed and cold isostatically pressed to prepare a ceramic blank. The blank was first sintered at 1570°C for 10h in an atmosphere furnace with flowing oxygen, and then hot isostatically pressed at 1500°C for 2h. Finally, it was annealed at 1200°C for 10h in an oxygen atmosphere to obtain a ceramic sheet. The XRD of the ceramic sample is as follows Figure 1 As shown, XRD shows that the ceramic is a pure garnet phase, which matches well with the #46-0448 PDF card (ICDD-PDF library). The sample emission peak is located at 556nm, the transmittance of 1mm thick ceramic in the visible light band is greater than 75%, the absolute light output is 43000ph / MeV, the decay time is 43ns, and the 20ms afterglow is less than 0.035%.

[0038] Example 3

[0039] x=0.01, y=0.01, z=0.01, R is Ce, A is Gd, Lu, A' is Mg, Ca, B is Al, Ga, the ceramic composition is (Ce 0.01 Lu 0.5 G 2.48 Mg 0.005 Ca 0.005 )(Si 0.01 Al 2.495 Ga 2.495 ) 12

[0040] The commercially available micron-grade high-purity raw materials: Al2O3(5N), Gd2O3(5N), Ga2O3(5N), Lu2O3(5N), CeO2(5N), (C2H5O)4Si(4N), MgO(4N), CaO(4N) ​​were accurately weighed in the above formula according to the stoichiometric ratio, ethanol was used as the ball milling medium, a high-purity Al2O3 ball mill and corresponding ball mills were used, and the mixture was milled in a high-energy ball mill (ZQM-P2, Changsha Miqi Instrument Equipment Co., Ltd.)) ball milled for 10 hours, the ball mill speed was 360rpm, the slurry was dried and passed through a 200 mesh sieve, the powder was pre-sintered at 700℃ for 2 hours, and then formed into a ceramic blank by dry pressing and cold isostatic pressing. The blank was first sintered at 1550℃ in an atmosphere furnace with flowing oxygen for 4 hours, then hot isostatic pressed at 1500℃ for 2 hours, and finally annealed at 1150℃ for 24 hours in an oxygen atmosphere to obtain a ceramic sheet. XRD of the ceramic sample is as follows Figure 1 As shown, XRD shows that the ceramic is a pure garnet phase, which matches well with the #46-0448 PDF card (ICDD-PDF library). The sample emission peak is located at 564nm, and the transmittance of 1mm thick ceramic in the visible light band is greater than 82%, the absolute light yield is 38000ph / MeV, the decay time is 31ns, and the 20ms afterglow is less than 0.03%.

[0041] Comparative Example 1

[0042] x=0.02, y=0.00075, z=0, R is Ce, A is Gd, A' is Mg, B is Al, Ga, the ceramic composition is (Ce 0.02 G 2.97925 Mg 0.00075 )(Al3Ga2)O 12

[0043] Comparative Example 1 adopts the same preparation method as Experimental Example 1, except that Si element is not doped in the formula to balance the charge generated by Mg doping. Figure 1 As shown, XRD shows that the ceramic is a pure garnet phase, which matches well with the #46-0448 PDF card (ICDD-PDF library). At this time, the emission peak of the sample is 550nm, the transmittance of the ceramic in the visible light band at 1mm is greater than 60%, the absolute light output is 46000ph / MeV, the decay time is 65ns, and the 20ms afterglow is less than 0.04%.

[0044] It can be seen from the above embodiments that the present invention discloses a heterovalent ion co-doped garnet transparent scintillation ceramic and a preparation method thereof. The prepared transparent scintillation ceramic has a cubic garnet structure, isotropy, an average grain size of less than 10 μm, and a 1 mm thick sample has a visible light band transmittance of higher than 60%; the heterovalent ion co-doped garnet transparent scintillation ceramic prepared by the present invention can achieve high light yield, reaching 24000ph / MeV~62000ph / MeV, and the decay time can be as low as 24ns; and the present invention adopts a high-energy ball milling method to prepare the powder, the preparation process is simple, and mass production can be achieved.

[0045] The above are only a few preferred embodiments of the present invention, which are described in a more specific and detailed manner, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A heterovalent ion co-doped garnet transparent scintillating ceramic, characterized in that: Has the following chemical formula: (What 0.01 IU 0.5 Gd 2.48 Mg 0.005 That 0.005 )(And 0.01 the 2.495 Ga 2.495 )A 12 ; The method for preparing the above-mentioned heterovalent ion co-doped garnet transparent scintillating ceramic comprises the following steps: 1) Ingredients: Raw materials with micron-level purity higher than 99.99% including Al2O3, Gd2O3, Ga2O3, Lu2O3, CeO2, (C2H5O)4Si, MgO(4N), CaO are accurately weighed in stoichiometric ratio according to the above chemical formula; 2) Ball milling: using ethanol as the ball milling medium, using an Al2O3 ball milling jar and an Al2O3 ball mill, the above raw materials were ball milled in a high-energy ball mill for 10 h at a ball milling speed of 360 rpm to obtain a slurry; 3) Pre-calcination: After the slurry is dried, it is sieved through a 200-mesh sieve to obtain a powder, and the powder is pre-calcined at 700°C for 2 hours to obtain a precursor; 4) Molding: The green body is formed by a two-step molding method. First, the precursor is dry pressed for more than 1 minute at a pressure of not less than 10Mpa to prepare a green body with a preliminary shape, and then the green body is cold isostatically pressed for 2 minutes at a pressure of ≥200Mpa to make the relative density of the green body reach more than 55%; 5) Sintering: The green billet is first sintered at 1550℃ in an atmosphere furnace with flowing oxygen for 4h, and then hot isostatically pressed at 1500℃ for 2h; 6) Annealing: the sintered material is annealed at 1150° C. for 24 hours in an oxygen atmosphere to obtain the heterovalent ion co-doped garnet transparent scintillating ceramic.

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