CN117888200A - Novel bismuth germanate scintillation crystal material with high radiation damage resistance and preparation method - Google Patents
Novel bismuth germanate scintillation crystal material with high radiation damage resistance and preparation method Download PDFInfo
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- 239000013078 crystal Substances 0.000 title claims abstract description 127
- 229910052797 bismuth Inorganic materials 0.000 title claims abstract description 76
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 239000000463 material Substances 0.000 title claims abstract description 73
- 230000005855 radiation Effects 0.000 title claims abstract description 44
- 238000002360 preparation method Methods 0.000 title abstract description 6
- 229910052684 Cerium Inorganic materials 0.000 claims abstract description 8
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 30
- 150000001875 compounds Chemical class 0.000 claims description 27
- 229910052697 platinum Inorganic materials 0.000 claims description 21
- 238000002844 melting Methods 0.000 claims description 10
- 230000008018 melting Effects 0.000 claims description 10
- 238000002156 mixing Methods 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 7
- 238000005303 weighing Methods 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000007788 liquid Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 238000010309 melting process Methods 0.000 claims description 3
- 238000003825 pressing Methods 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 239000000155 melt Substances 0.000 claims description 2
- 229910009111 xH2 O Inorganic materials 0.000 claims description 2
- 238000002474 experimental method Methods 0.000 abstract description 4
- 238000003384 imaging method Methods 0.000 abstract description 3
- 238000009206 nuclear medicine Methods 0.000 abstract description 3
- 238000004020 luminiscence type Methods 0.000 description 11
- 230000000052 comparative effect Effects 0.000 description 9
- NKTZYSOLHFIEMF-UHFFFAOYSA-N dioxido(dioxo)tungsten;lead(2+) Chemical compound [Pb+2].[O-][W]([O-])(=O)=O NKTZYSOLHFIEMF-UHFFFAOYSA-N 0.000 description 9
- 238000012360 testing method Methods 0.000 description 8
- 150000002500 ions Chemical class 0.000 description 6
- 230000007547 defect Effects 0.000 description 5
- YBMRDBCBODYGJE-UHFFFAOYSA-N germanium oxide Inorganic materials O=[Ge]=O YBMRDBCBODYGJE-UHFFFAOYSA-N 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 5
- 229910005793 GeO 2 Inorganic materials 0.000 description 4
- ZMIGMASIKSOYAM-UHFFFAOYSA-N cerium Chemical compound [Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce][Ce] ZMIGMASIKSOYAM-UHFFFAOYSA-N 0.000 description 3
- 230000005284 excitation Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- 238000000137 annealing Methods 0.000 description 2
- 229910000420 cerium oxide Inorganic materials 0.000 description 2
- 238000001748 luminescence spectrum Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- YZCKVEUIGOORGS-OUBTZVSYSA-N Deuterium Chemical compound [2H] YZCKVEUIGOORGS-OUBTZVSYSA-N 0.000 description 1
- 229910052693 Europium Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- -1 cerium is introduced Chemical class 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 229910052805 deuterium Inorganic materials 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- OGPBJKLSAFTDLK-UHFFFAOYSA-N europium atom Chemical compound [Eu] OGPBJKLSAFTDLK-UHFFFAOYSA-N 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000002688 persistence Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 230000036962 time dependent Effects 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052724 xenon Inorganic materials 0.000 description 1
- FHNFHKCVQCLJFQ-UHFFFAOYSA-N xenon atom Chemical compound [Xe] FHNFHKCVQCLJFQ-UHFFFAOYSA-N 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/22—Complex oxides
- C30B29/32—Titanates; Germanates; Molybdates; Tungstates
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
- C30B15/20—Controlling or regulating
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- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
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Abstract
The invention relates to the technical field of scintillation crystals, in particular to an IPC C30B29, and more particularly relates to a novel bismuth germanate scintillation crystal material with high radiation damage resistance and a preparation method thereof. The invention provides a novel bismuth germanate scintillation crystal material with high radiation damage resistance, which has the general formula: a xBi4‑xGe3O12; wherein x is more than or equal to 0.0001 and less than or equal to 5; a is one or more combinations of Ce, ca, la, nd. The bismuth germanate scintillation crystal material provided by the invention does not generate extra scintillation slow component while greatly improving the radiation damage resistance, and scintillation afterglow and instrument electronic noise are at the same level. Can be used for occasions with extremely high requirements on the irradiation resistance of materials, such as high-energy physical experiments, nuclear medicine imaging and the like.
Description
Technical Field
The invention relates to the technical field of scintillation crystals, in particular to an IPC C30B29, and more particularly relates to a novel bismuth germanate scintillation crystal material with high radiation damage resistance and a preparation method thereof.
Background
The scintillating material emits pulsed visible light under the action of high-energy ray particles (X-rays, gamma particles, neutrons, etc.), a process known as scintillation luminescence. The related information such as the energy of the high-energy particles which act on the scintillating material can be deduced by measuring parameters such as the luminous intensity, the time characteristic and the like of the scintillating material through a proper photoelectric detector. Therefore, the scintillation material is widely applied in the fields of high-energy physical experiments, nuclear medicine imaging, prospecting, space exploration and the like.
In 1973, m.j.weber found that scintillation luminescence Luminescence of Bi4Ge3O12:Spectral and decay properties,M.J.Weber and R.R.Monchamp.,J.Appl.Phys.,Vol.44,No.12(1973)5495, of bismuth germanate (Bi 4Ge3O12) crystals under the action of X-rays opened the study of bismuth germanate as a scintillation material. The bismuth germanate crystal has no deliquescence, high density and high detection efficiency on rays, and the luminous wavelength of the bismuth germanate crystal is matched with that of a common photoelectric detector. Bismuth germanate crystals have been widely used today after decades of development.
The scintillation material can cause irradiation damage after being irradiated by high-dose high-energy rays. The most direct manifestation of radiation damage is a decrease in the scintillation luminous intensity of the scintillation material; serious irradiation damage will lead to failure of the scintillation material. Therefore, reducing the radiation damage of the scintillation material, that is, improving the radiation damage resistance of the scintillation material, is particularly important for the practical application of the scintillation material.
Radiation damage to the scintillation material is believed to be caused by defects present inside the scintillation material. The raw materials for synthesizing bismuth germanate crystals generally adopt high-purity Bi 2O3 and GeO 2 powder, and the components are easily deviated due to inconsistent volatilization of the materials at high temperature, so that the artificially synthesized bismuth germanate crystals contain a large number of point defects which are invisible to naked eyes. The point defects cause that bismuth germanate crystals generate a large amount of color centers after being irradiated by high-energy rays, and the scintillation performance is greatly reduced.
Xie Youyu et al [ improving the radiation damage resistance technique of Bismuth Germanate (BGO) crystals, application number: 90102951.3, publication No.: CN1060687a proposes doping europium (Eu) into pure bismuth germanate crystals in order to improve their resistance to irradiation damage. Xie Youyu et al show that: the luminous intensity of the pure bismuth germanate crystal after 10 gray (Gy) dose irradiation is reduced by more than 70%; the irradiation damage resistance of bismuth germanate after Eu is introduced is improved: the luminescence intensity of the bismuth germanate crystal added with 100ppm is reduced by about 40% after 10 gray (Gy) dose irradiation, irradiation damage is still large, and Eu introduction can cause a slow component of 4 ms, which will cause signal accumulation, limiting the use of the material. Although bismuth germanate scintillation crystals have been widely used, the problem of poor radiation damage resistance has not been solved effectively A Study on Radiation Damage in BGO and PWO-IICrystals,Fan Yang et al.,Journal of Physics:Conference Series404(2012)012025.
Disclosure of Invention
In order to solve the problems in the prior art, the first aspect of the invention provides a novel bismuth germanate scintillation crystal material with high radiation damage resistance, which has the following general formula:
AxBi4-xGe3O12
Wherein x is more than or equal to 0.0001 and less than or equal to 5;
further preferably, x is more than or equal to 0.0001 and less than or equal to 3; in a preferred embodiment, x=0.004, x=0.02 or x=0.12.
A is one or more combinations of Ce, ca, la, nd.
According to the invention, ce 3+ ions are doped in the bismuth germanate crystal, so that the defect in the crystal is compensated and inhibited by cerium oxide, the radiation damage resistance of the bismuth germanate crystal is improved, and meanwhile, slow scintillation and luminescence can not be caused. The inventor finds that the common BGO (bismuth germanate crystal) has poor radiation damage resistance, can be quickly failed in a high-dose radiation environment, greatly improves the radiation resistance after cerium with proper concentration is introduced, is equivalent to the radiation resistance of lead tungstate (lead tungstate is a scintillation crystal with good radiation resistance, and does not cause slow luminescence when cerium is introduced, unlike Eu doping). The novel high radiation damage resistance bismuth germanate scintillation crystal has greatly improved radiation damage resistance compared with Eu doped bismuth germanate crystal (the radiation damage is less than 5% and far better than Eu doped 40% when the abscissa is 10 gray shown in figure 1), and does not cause slow luminescence (figure 6).
The second aspect of the invention provides a preparation method of a novel bismuth germanate scintillation crystal material with high radiation damage resistance, which comprises a pulling method or a descending method.
Preferably, the specific steps of the pulling method comprise the following steps:
S1: drying the high purity compound; weighing and mixing the high-purity compound according to the molar ratio of elements in the general formula A xBi4-xGe3O12, pressing into a block, and transferring the block into a platinum crucible;
s2: placing the platinum crucible in a crystal growth furnace of a Czochralski method, starting a power supply, melting lump materials in the platinum crucible, and preserving heat until the components fully react;
S3: slowly lowering the bismuth germanate seed crystal until the bismuth germanate seed crystal is contacted with the melt liquid surface formed by the lump materials; slowly reducing the power of the growth furnace to carry out lifting rotation, starting to grow crystals, and reducing the power of the growth furnace until the temperature reaches the room temperature after the growth is finished, so as to obtain the novel bismuth germanate scintillation crystal material with high radiation damage resistance.
Preferably, the specific steps of the descent method include the following steps:
m1: drying the high purity compound; weighing and mixing the high-purity compound according to the molar ratio of each element in the general formula A xBi4-xGe3O12, and transferring the high-purity compound into a thin-wall platinum crucible;
M2: placing bismuth germanate seed crystal at one end of a thin-wall platinum crucible, and sealing; placing the sealed crucible seed crystal end downwards in a crystal growth furnace by a descending method, starting the crystal growth furnace, and heating and melting materials;
M3: the melting process ensures that the high-purity compound is completely melted and a part of the seed crystal is melted, after the temperature is kept for a period of time, the temperature gradient of a crystal growth interface is set, the crucible is slowly lowered, and the crystal growth is started; and slowly reducing the furnace temperature until the room temperature after the crystal growth is finished, and obtaining the novel bismuth germanate scintillation crystal material with high radiation damage resistance.
Preferably, the high purity compounds include a compound of a, a compound of Bi, and a compound of Ge; the purity of the high purity compound is not lower than 99.999%.
Preferably, the source of the compound of A is Ce, ca, la, nd high-purity oxide or carbonate; taking Ce as an example, the high-purity oxide from which the Ce is derived is CeO 2 or Ce 2(CO3)3xH2 O.
Preferably, the Bi compound is Bi 2O3.
Preferably, the Ge compound is GeO 2.
Preferably, the pulling speed in the step S3 is 1-6 mm/h, and the rotating speed is 6-10 revolutions/min; it is further preferable that the pulling speed is 2mm/h and the rotation speed is 8 rpm.
Preferably, the cavity temperature of the growth furnace in M3 is set to be 150 higher than the melting point of bismuth germanate.
Preferably, the temperature gradient of the crystal growth interface is set in the M3 to be 30-40 /cm; further preferably, it is 35 /cm.
Preferably, the descending speed of the crucible in the M3 is 0.1-1.5 mm/h; further preferably, the thickness is 0.5mm/h.
Advantageous effects
1. According to the invention, ce 3+ ions are doped in the bismuth germanate crystal, so that the defect in the crystal is compensated and inhibited by cerium oxide, the radiation damage resistance of the bismuth germanate crystal is improved, and meanwhile, slow scintillation and luminescence can not be caused.
2. According to the invention, by doping Ce 3+ ions, namely cerium is introduced, the scintillation luminescence is partially quenched, so that the luminescence intensity is reduced, and the detector can be prevented from being saturated under the action of particles with high energy.
3. The preparation method is simple and efficient.
4. The novel bismuth germanate scintillation crystal material with high radiation damage resistance does not generate extra scintillation slow component, and scintillation afterglow and instrument electronic noise are at the same level.
5. The novel bismuth germanate scintillation crystal material with high radiation damage resistance prepared by the invention can be used for occasions with extremely high requirements on the radiation resistance of the material, such as high-energy physical experiments, nuclear medicine imaging and the like.
Drawings
Fig. 1 is a graph showing the comparison of the radiation damage resistance of lead tungstate crystals, the novel bismuth germanate scintillation crystal material with high radiation damage resistance prepared in comparative example 1 and example 2.
Fig. 2 is an optical transmittance of the novel bismuth germanate scintillation crystal materials with high resistance to irradiation damage prepared in example 1 and example 2.
Fig. 3 is a multi-channel spectrum of the novel bismuth germanate scintillation crystal material with high resistance to radiation damage prepared in comparative example 1 (a) and example 2 (b).
Fig. 4 is a measurement result of scintillation afterglow after X-ray irradiation of the novel bismuth germanate scintillation crystal material with high resistance to radiation damage prepared in example 2.
Fig. 5 is a scintillation decay time test result of the bismuth germanate scintillation crystal material prepared in comparative example 1 (a).
Fig. 6 is a scintillation decay time test result of the novel bismuth germanate scintillation crystal material with high radiation damage resistance prepared in the example 3 (b).
Fig. 7 is an X-ray excitation scintillation luminescence spectrum of the novel bismuth germanate scintillation crystal materials with high resistance to irradiation damage prepared in example 1 and example 3.
Detailed Description
Example 1
Drying Bi 2O3GeO2 and CeO 2 with purity not lower than 99.999% at 200 for 48 hours; weighing and mixing the dried Bi 2O3GeO2 and CeO 2 according to the molar ratio of each element in the general formula Ce 0.004Bi3.996Ge3O12, pressing into blocks, and transferring the blocks into a platinum crucible; placing the platinum crucible in a crystal growth furnace of a Czochralski method, starting a power supply, melting lump materials in the platinum crucible, and preserving heat until the components fully react; and growing the crystal by a pulling method. The pulling speed was 2mm per hour, and the seed rotation speed was 8 revolutions per minute. After the pulling is finished, the power of the growth furnace is slowly reduced to 25 . Taking out the crystal, and the crystal is transparent, has no inclusion and no growth stripes. And annealing and processing the material into a hexahedral polished cube with the side length of 17 mm, thereby obtaining the novel bismuth germanate scintillation crystal material with high radiation damage resistance.
Example 2
The embodiment of example 2 is the same as that of example 1, except that the general formula Ce 0.02Bi3.986Ge3O12.
Example 3
Drying Bi 2O3GeO2 and CeO 2 with purity not lower than 99.999% at 200 for 48 hours; weighing and mixing the dried Bi 2O3GeO2 and CeO 2 according to the molar ratio of each element in the general formula Ce 0.12Bi3.88Ge3O12, fully mixing and transferring the mixture into a thick-wall platinum crucible, placing the thick-wall platinum crucible filled with Bi 2O3GeO2 and CeO 2 into an intermediate frequency melting furnace for melting, and transferring the melted feed liquid into the thin-wall platinum crucible; placing bismuth germanate seed crystal at one end of a thin-wall platinum crucible, and sealing; placing the sealed crucible seed crystal end downwards in a crystal growth furnace by a descending method, starting the crystal growth furnace, and heating and melting materials; the melting process ensures that the high-purity compound is completely melted and a part of the seed crystal is melted, after the temperature is kept for a period of time, the temperature gradient of a crystal growth interface is set to 35 /cm, the crucible is slowly lowered, and the crystal growth is started; and slowly reducing the furnace temperature until the temperature reaches 25 after the crystal growth is finished, stripping the thin-wall platinum crucible, and taking out the crystal. The crystal is yellowish, has no inclusion and no growth stripes, and the novel bismuth germanate scintillation crystal material with high radiation damage resistance is obtained. The crystals were cut into 2 mm thick slices. The polished large end face is used for scintillation performance measurement.
Comparative example 1
Drying Bi 2O3 and GeO 2 with purity not lower than 99.999% at 200 for 48 hours; weighing and mixing the dried Bi 2O3 and GeO 2 according to the molar ratio of each element in the general formula Bi 4Ge3O12, fully mixing, briquetting, loading into a platinum crucible, placing the platinum crucible into a crystal growth furnace of a Czochralski method, starting a power supply, melting lump materials in the platinum crucible, and preserving heat until each component fully reacts; and growing the crystal by a pulling method. The pulling speed was 2mm per hour, and the seed rotation speed was 8 revolutions per minute. After the pulling is finished, the power of the growth furnace is slowly reduced to 25 . Taking out the crystal, annealing and processing the crystal into a hexahedral polished cube with the side length of 17 mm, wherein the crystal is colorless and transparent, has no inclusion and no growth stripes, and thus the novel bismuth germanate scintillation crystal material with high radiation damage resistance is obtained.
Performance testing
1. Testing light output
The light output was measured according to GBT13181 method. After the lead tungstate crystal, the novel bismuth germanate scintillation crystal material with high radiation damage resistance prepared in the example 2 and the bismuth germanate scintillation crystal material prepared in the comparative example 1 are irradiated by the same irradiation dose, the light output of the lead tungstate crystal, the novel bismuth germanate scintillation crystal material with high radiation damage resistance prepared in the example 2 and the bismuth germanate scintillation crystal material prepared in the comparative example 1 is measured, and the result is shown in fig. 1.
As can be seen from fig. 1, the irradiation damage resistance of the bismuth germanate crystal with the general formula Ce 0.02Bi3.98Ge3O12 obtained in example 2 is greatly improved compared with that of comparative example 1 under the same irradiation dose. In order to further clarify, fig. 1 also shows the irradiation damage of the lead tungstate crystal under the same condition (the irradiation damage resistance of the lead tungstate crystal is very good, and the lead tungstate crystal is generally used for manufacturing a scintillation detector [ The CMS experiment AT THE CERN LHC, the CMS Collaboration et al.,2008JINST 3S08004] under a high dose irradiation environment, and the irradiation damage resistance of the bismuth germanate scintillation crystal material prepared in example 2 is equivalent to that of the lead tungstate crystal, and is a scintillation material with excellent irradiation damage resistance.
2. The optical transmittance was measured using a dual beam spectrophotometer (light source below 340 nm (including deuterium lamp) and light source above 340 nm (xenon lamp)), and the result is shown in fig. 2.
As can be seen from fig. 2, in the general formula Ce xBi4-xGe3O12, the absorption band edge of the bismuth germanate crystal is red-shifted as x increases. The light transmittance is more than 72 percent.
3. Testing multiple energy spectra
The multichannel spectra of the scintillation crystal materials of comparative example 1 and example 2 were tested using gamma rays as excitation sources according to the GBT13181 method, and the multichannel spectra and peak channel values of the scintillation crystal materials were recorded, and the results are shown in fig. 3.
The peak channel value of the multi-channel spectrum corresponds to the luminous intensity of the scintillation material. As can be seen from fig. 3, the light emission intensity of the bismuth germanate scintillation crystal material of the general formula Ce 0.02Bi3.98Ge3O12 in example 2 is equivalent to 50% of that of the pure bismuth germanate crystal. The Ce 3+ ions are introduced into the bismuth germanate crystal to adjust the scintillation luminous intensity of the bismuth germanate crystal, so that the saturation of the photoelectric detector caused by the overlarge energy of high-energy particles is avoided.
4. Measuring scintillation persistence
The method for testing the scintillation afterglow comprises the following steps: the scintillator and photomultiplier tube (PMT) are air coupled together and placed in a dark box, and after high voltage, the PMT collects dark noise signals of the PMT without X-ray irradiation. Next, using a signal generator to drive an X-ray tube to generate X-rays (tungsten target, tube voltage 50KV and current 80 microamps), irradiating a scintillator for 60 seconds, and then closing the X-rays; and collecting the output signal of the PMT during X-ray irradiation, and continuously collecting the output signal of the PMT for 5 seconds after the X-ray is turned off. Finally, the output signal of PMT is amplified and discriminated and then is input into a counter, and the relative values of afterglow intensities of different growth modes at the test temperature (22.5 ) are obtained. The results are shown in FIG. 4.
As can be seen from fig. 4, the scintillation afterglow after the bismuth germanate crystal is introduced into Ce 3+ ion is at the same level as the electronic noise, showing that the scintillation afterglow of the material is negligible.
5. Testing scintillation decay time
The scintillation decay time L.M.Bollinger and G.E.Thomas.,Measurement of the Time Dependence of Scintillation Intensity by aDelayed Coincidence Method.Rev.Sci.Instrum.32,1044(1961), is measured using a time-dependent single photon counting method and the results are shown in fig. 5 and 6.
As can be seen from fig. 5 and 6, the scintillation crystal material in example 3 has a slightly faster scintillation decay time than comparative example 1, and the bismuth germanate crystal does not cause slow luminescence after Ce 3+ ions are introduced.
6. The X-ray excitation scintillation luminescence spectrum was measured according to the GBT13181 method and the results are shown in FIG. 7.
Claims (10)
1. The novel bismuth germanate scintillation crystal material with high radiation damage resistance is characterized by having the following general formula:
AxBi4-xGe3O12
Wherein x is more than or equal to 0.0001 and less than or equal to 5;
a is one or more combinations of Ce, ca, la, nd.
2. The novel bismuth germanate scintillation crystal material with high radiation damage resistance according to claim 1, wherein x is more than or equal to 0.0001 and less than or equal to 3.
3. A method of preparing a bismuth germanate scintillation crystal material as claimed in any one of claims 1 to 2, comprising a pulling or dropping method.
4. The method for preparing bismuth germanate scintillation crystal material as recited in claim 3, wherein the specific steps of the pulling method include the following steps:
S1: drying the high purity compound; weighing and mixing the high-purity compound according to the molar ratio of elements in the general formula A xBi4-xGe3O12, pressing into a block, and transferring the block into a platinum crucible;
s2: placing the platinum crucible in a crystal growth furnace of a Czochralski method, starting a power supply, melting lump materials in the platinum crucible, and preserving heat until the components fully react;
S3: slowly lowering the bismuth germanate seed crystal until the bismuth germanate seed crystal is contacted with the liquid level of the melt melted by the lump material; slowly reducing the power of the growth furnace, simultaneously pulling and rotating, and starting to grow crystals; and after the growth is finished, reducing the power of a growth furnace until the temperature reaches the room temperature, and obtaining the novel bismuth germanate scintillation crystal material with high radiation damage resistance.
5. The method for preparing bismuth germanate scintillation crystal material as recited in claim 3, wherein the specific steps of the descent method include the following steps:
m1: drying the high purity compound; weighing and mixing the high-purity compound according to the molar ratio of each element in the general formula A xBi4-xGe3O12, and transferring the high-purity compound into a thin-wall platinum crucible;
M2: placing bismuth germanate seed crystal at one end of a thin-wall platinum crucible, and sealing; placing the sealed crucible seed crystal end downwards in a crystal growth furnace by a descending method, starting the crystal growth furnace, and heating and melting materials;
M3: the melting process ensures that the high-purity compound is completely melted and a part of the seed crystal is melted, after the temperature is kept for a period of time, the temperature gradient of a crystal growth interface is set, the crucible is slowly lowered, and the crystal growth is started; and slowly reducing the furnace temperature until the room temperature after the crystal growth is finished, and obtaining the novel bismuth germanate scintillation crystal material with high radiation damage resistance.
6. The method for producing a bismuth germanate scintillation crystal material as recited in claim 4 or 5, wherein the high-purity compound includes a compound of a, a compound of Bi, and a compound of Ge; the purity of the high purity compound is not lower than 99.999%.
7. The method of preparing bismuth germanate scintillation crystal material as recited in claim 6, wherein the source of the compound of A is Ce, ca, la, nd high purity oxide; the high-purity oxide of Ce element source is CeO 2 or Ce 2(CO3)3xH2 O.
8. The method for preparing bismuth germanate scintillation crystal material as recited in claim 4, wherein the pulling speed in S3 is 1-6 mm/h, and the rotation speed is 6-10 rpm.
9. The method for preparing bismuth germanate scintillation crystal material as recited in claim 5, wherein a temperature gradient of a crystal growth interface is set in M3 to be 30-40 /cm.
10. The method for producing a bismuth germanate scintillation crystal material as claimed in claim 5, wherein the crucible descending speed in M3 is 0.1 to 1.5mm/h.
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