CN115637148B - Lithium thallium co-doped sodium-based halogen scintillation crystal, preparation method and application - Google Patents
Lithium thallium co-doped sodium-based halogen scintillation crystal, preparation method and application Download PDFInfo
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Abstract
The application provides a lithium thallium co-doped sodium-based halogen scintillation crystal, a preparation method and application thereof, wherein the composition general formula of the lithium thallium co-doped sodium-based halogen scintillation crystal is as follows: (Na) 1‑a‑b‑c 6 Li a Tl b M c ) X is a group; x is one or more of F, cl, br, I; m is Ca, sr, mg or Ba; wherein a is more than 0 and less than or equal to 0.2, b is more than 0 and less than or equal to 0.01,0, and c is more than 0 and less than or equal to 0.05. The lithium thallium co-doped sodium-based halogen scintillation crystal not only concentrates lithium and thallium dopants, but also introduces alkaline earth metal ions for doping, and can realize synchronous improvement of gamma energy resolution and neutron-gamma discrimination capability by introducing alkaline earth metal ions. The scintillation crystal has the advantages of high light output, high energy resolution, excellent neutron/gamma ray discrimination capability and the like, and can be applied to the fields of petroleum exploration wells, security inspection, industrial detection and the like.
Description
Technical Field
The application relates to the field of crystal growth technology and radiation detection, in particular to an alkaline earth metal doped lithium thallium co-doped sodium-based halogen scintillation crystal, a preparation method and application.
Background
The neutron detection technology has important functions in the aspects of homeland security, petroleum exploration well and the like. 3 The neutron detector of He gas has the advantages of high detection efficiency, simple structure, stable performance and the like, and is widely used. Rapid development of neutron detection technology 3 He gas demand has proliferated and is subject to national export restrictions in the united states, russia and the like, 3 he gas deficiency, commonly used 3 He detectors are likely to be replaced in the future. Accordingly, neutron detection materials are being studied in a large number of ways, for example: lithium glass, 6 Powder of LiF and ZnS (Ag), 6 LiI: eu crystal, etc. The lithium glass is transparent, low in production cost and short in response time, but the neutron light yield is low, and the light yield is 4,000 photons/neutron. 6 The powder of LiF and ZnS (Ag) has a light yield of up to 160,000photons/neutron under neutron irradiation, but a long response timeCannot be made into single crystals, and the neutron detection efficiency is not 20%. 6 The LiI-Eu crystal has high thermal neutron detection efficiency, but has decay time as long as 1.4s and strong deliquescence.
On the other hand, almost all neutron radiation is accompanied by gamma radiation, and development of neutron technology has put new demands on neutron detection technology. The neutron/gamma dual-detection material with high detection efficiency, strong discrimination capability and low cost becomes an important requirement of the market. In the recent past, 6 LiCaAlF 6 :Eu、Cs 2 6 LiYCl 6 ce and other series of neutron/gamma double detection scintillation crystals are reported. 6 LiCaAlF 6 Eu crystal in 252 Neutron light yield at Cf was 29,000photons/neutron, but gamma detection was weak. Cs (cells) 2 6 LiYCl 6 Ce crystal has excellent capability of detecting and discriminating gamma rays, fast neutrons and slow neutrons, and has wide attention and commercialization. However, cs 2 6 LiYCl 6 Ce also has the problems of high raw material cost, inconsistent melting and the like. NaI Tl is the most widely used scintillation crystal material for gamma ray detection at present, and in 2017, yang et al, santa-Gobi Inc., france will 6 Li is introduced into the NaI-Tl scintillation crystal in a co-doped mode, so that neutron/gamma dual-mode detection is realized. NaI: tl prepared by Bridgman method, 6 the Li crystal performance is equivalent to that of standard NaI: tl crystal, 2% 6 Neutron-gamma discrimination capability of Li doped crystal and Cs of same size 2 6 LiYCl 6 Ce crystals are close, and the discrimination quality factor is about 4. NaI is equal to Tl, and the total content of the catalyst, 6 the Li crystal has low cost of raw materials, simple crystal structure and commercial prospect of large-scale application. However, the energy resolution of the crystal is poor, and further optimization is needed for neutron-gamma dual detection with high requirements, and the discrimination quality factor is further improved.
It should be noted that the information disclosed in the above background section is only for enhancing understanding of the background of the application and thus may include information that does not form the prior art that is already known to those of ordinary skill in the art.
Disclosure of Invention
Aiming at the problems in the prior art, the application aims to provide a lithium thallium co-doped sodium-based halogen scintillation crystal, a preparation method and application thereof.
The first aspect of the application provides a lithium thallium co-doped sodium-based halogen scintillation crystal, which has the following general formula: (Na) 1-a-b-c 6 Li a Tl b M c )X；
X is one or more of F, cl, br, I;
m is Ca, sr, mg or Ba;
wherein a is more than 0 and less than or equal to 0.2, b is more than 0 and less than or equal to 0.01,0, and c is more than 0 and less than or equal to 0.1.
According to a first aspect of the application, 0.001 < c.ltoreq.0.05.
According to a first aspect of the present application, the scintillation crystal is (Na 1-a-b-c 6 Li a Tl b Sr c ) I, wherein c is more than 0 and less than or equal to 0.001.
According to the first aspect of the application, the energy resolution of the full-function peak of the scintillation crystal at 662keV is less than or equal to 5.4%.
According to a first aspect of the present application, the scintillation crystal is (Na 1-a-b-c 6 Li a Tl b Ca c ) X, wherein c is more than 0 and less than or equal to 0.002.
According to a first aspect of the application, the lithium thallium co-doped sodium-based halogen scintillation crystal is a single crystal.
According to a second aspect of the present application, there is provided a preparation method for preparing the lithium thallium co-doped sodium-based halogen scintillation crystal, comprising the steps of:
according to the general formula (Na) 1-a-b-c 6 Li a Tl b M c ) X respectively weighing sodium iodide, lithium halide, thallium halide and halogenated alkaline earth metal;
mixing the weighed raw materials, placing the raw materials into a crucible and sealing;
vertically placing the sealed crucible in a growth furnace, and heating the crucible to 700-900 ℃;
the crucible descends in the growth furnace at a descending speed of 2-6 mm/h after the raw materials are melted;
and after the crystal growth is finished, the growth furnace is cooled to room temperature, and the crucible is taken out to obtain the lithium thallium co-doped sodium-based halogen scintillation crystal.
According to a second aspect of the application, the crucible bottom has a capillary tube holding a seed crystal.
According to a third aspect of the application, an application is provided, wherein the lithium thallium co-doped sodium-based halogen scintillation crystal is applied to neutron detection or gamma-neutron dual-mode detection.
The lithium thallium co-doped sodium-based halogen scintillation crystal disclosed by the application is not only concentrated in lithium and thallium dopants, but also doped with alkaline earth metal ions, and can realize the improvement of gamma energy resolution and neutron-gamma discrimination capability by introducing alkaline earth metal ions.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the application and together with the description, serve to explain the principles of the application and, together with the description, further features, objects and advantages of the application, will become apparent from a reading of the following detailed description of non-limiting embodiments, taken in conjunction with the accompanying drawings. It is evident that the drawings in the following description are only some embodiments of the present application and that other drawings may be obtained from these drawings without inventive effort for a person of ordinary skill in the art. Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus a repetitive description thereof will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities.
FIG. 1 is a flow chart of a method for preparing a lithium thallium co-doped sodium base halogen scintillation crystal according to an embodiment of the application;
FIG. 2 is a physical diagram of a lithium thallium co-doped sodium-based halogen scintillation crystal prepared by the preparation method of different embodiments of the application;
FIG. 3 shows an embodiment of the present application (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) I crystal with undoped NaI: 6 an X-ray excitation emission spectrum of Li, tl crystals;
FIG. 4 shows an embodiment of the present application (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) I crystal with undoped NaI: 6 gamma energy spectrum of Li, tl crystal;
fig. 5 and 6 are undoped NaI: 6 neutron spectrum and gamma spectrum of Li and Tl crystal, and calculated discrimination capability FOM value scattered point spectrum of the two;
FIGS. 7 and 8 are diagrams of an embodiment of the present application (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) A neutron spectrum and a gamma spectrum of the I crystal and a discrimination capability FOM value scattered point spectrum calculated by the neutron spectrum and the gamma spectrum of the I crystal;
FIG. 9 shows an embodiment of the present application (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) I crystal with undoped NaI: 6 a scintillation decay time diagram of the Li, tl crystal;
FIG. 10 shows an embodiment of the present application (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) X and undoped NaI: 6 an X-ray excitation emission spectrum of Li, tl crystals;
FIG. 11 shows an embodiment of the present application (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) X crystal with undoped NaI: 6 gamma energy spectrum of Li, tl crystal;
FIGS. 12 and 13 are diagrams of an embodiment of the present application (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) Neutron spectrum and gamma spectrum of the crystal and the calculated discrimination capability FOM value scattered point spectrum of the neutron spectrum and the gamma spectrum;
FIG. 14 shows an embodiment of the present application (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) X crystal with undoped NaI: 6 scintillation decay time diagram of Li, tl crystals.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments may be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "examples," "particular examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present specification. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples and the features of the different embodiments or examples presented in this specification may be combined and combined by those skilled in the art without contradiction.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the expressions of the present specification, the meaning of "plurality" is two or more unless otherwise specifically defined.
Throughout the specification, when a device is said to be "connected" to another device, this includes not only the case of "direct connection" but also the case of "indirect connection" with other elements interposed therebetween. In addition, when a certain component is said to be "included" in a certain device, unless otherwise stated, other components are not excluded, but it means that other components may be included.
Terms representing relative spaces such as "lower", "upper", and the like may be used to more easily describe the relationship of one device to another device as illustrated in the figures. Such terms refer not only to the meanings indicated in the drawings, but also to other meanings or operations of the device in use. For example, if the device in the figures is turned over, elements described as "under" other elements would then be described as "over" the other elements. Thus, the exemplary term "lower" includes both upper and lower. The device may be rotated 90 deg. or at other angles and the terminology representing relative space is to be construed accordingly.
Although the terms first, second, etc. may be used herein to connote various elements in some instances, the elements should not be limited by the terms. These terms are only used to distinguish one element from another element. For example, a first interface, a second interface, etc. Furthermore, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including" specify the presence of stated features, steps, operations, elements, components, items, categories, and/or groups, but do not preclude the presence, presence or addition of one or more other features, steps, operations, elements, components, items, categories, and/or groups. The terms "or" and/or "as used herein are to be construed as inclusive, or meaning any one or any combination. Thus, "A, B or C" or "A, B and/or C" means "any of the following: a, A is as follows; b, a step of preparing a composite material; c, performing operation; a and B; a and C; b and C; A. b and C). An exception to this definition will occur only when a combination of elements, functions, steps or operations are in some way inherently mutually exclusive.
Although not differently defined, including technical and scientific terms used herein, all terms have the same meaning as commonly understood by one of ordinary skill in the art to which this specification belongs. The term addition defined in the commonly used dictionary is interpreted as having a meaning conforming to the contents of the related art document and the current hint, so long as no definition is made, it is not interpreted as an ideal or very formulaic meaning too much.
Aiming at the problems in the prior art, the application provides a lithium thallium co-doped sodium-based halogen scintillation crystal, a preparation method and application thereof, wherein the composition general formula of the lithium thallium co-doped sodium-based halogen scintillation crystal is as follows: (Na) 1-a-b-c 6 Li a Tl b M c ) X is a group; x is one or more of F, cl, br, I; m is Ca, sr, mg or Ba; wherein a is more than 0 and less than or equal to 0.2, b is more than 0 and less than or equal to 0.01,0, and c is more than 0 and less than or equal to 0.05. The lithium thallium co-doped sodium-based halogen scintillation crystal provided by the application is doped with alkaline earth metal ions besides concentrated lithium and thallium dopants, and can realize improvement of gamma energy resolution and neutron-gamma discrimination capability by introducing alkaline earth metal ions, and the scintillation crystal has the advantages of high light output, high energy resolution, excellent neutron/gamma ray discrimination capability and the like, and can be applied to the fields of petroleum exploration wells, security inspection, industrial detection and the like.
FIG. 1 is a flow chart of a method for preparing a lithium thallium co-doped sodium-based halogen scintillation crystal according to an embodiment of the application, wherein the method comprises the following steps:
s10: according to the general formula (Na) 1-a-b-c 6 Li a Tl b M c ) X respectively weighing sodium iodide, lithium halide, thallium halide and halogenated alkaline earth metal; in the actual preparation, preferably sodium iodide (NaI), lithium halide 6 LiX), thallium halide (TlX) and alkaline earth halide have a purity of 99.9% or more. The application adopts 6 Li and Tl ions are used as an activator of the lithium thallium co-doped sodium base halogen scintillation crystal, 6 li and Tl ions in the form of halides, e.g 6 LiI and TlI are incorporated into the feedstock. Likewise, alkaline earth metal ions (Ca, sr, mg, ba) are employed as dopants for lithium thallium co-doped sodium based halogen scintillation crystals, the alkaline earth metal ions being incorporated into the feedstock in the form of halides MX.
S20: mixing the weighed raw materials, placing the raw materials into a crucible and sealing; the crucible can be a quartz crucible, the shape of the crucible can be cylindrical, square column or conical, and preferably, a capillary tube for fixing seed crystal is arranged at the bottom of the crucible, so that the growth of the lithium thallium co-doped sodium-based halogen scintillation crystal is facilitated.
S30: vertically placing the sealed crucible in a growth furnace, and heating the crucible to 700-900 ℃;
s40: the crucible descends in the growth furnace at a descending speed of 2-6 mm/h after the raw materials are melted;
s50: and after the crystal growth is finished, the growth furnace is cooled to room temperature, and the crucible is taken out to obtain the lithium thallium co-doped sodium-based halogen scintillation crystal.
Fig. 2 is a physical diagram of a lithium thallium co-doped sodium halogen scintillation crystal prepared by the preparation method according to different embodiments of the application, and the scintillation crystal prepared by the method has the following composition general formula:
(Na 1-a-b-c 6 Li a Tl b M c )X；
x is one or more of F, cl, br, I;
m is Ca, sr, mg or Ba;
wherein a is more than 0 and less than or equal to 0.2, b is more than 0 and less than or equal to 0.01,0, and c is more than 0 and less than or equal to 0.1. Preferably, 0.001 < c.ltoreq.0.05. The lithium thallium co-doped sodium-based halogen scintillation crystal is a single crystal.
The following further illustrates the lithium thallium co-doped sodium-based halogen scintillation crystal of the application and its preparation method. It is to be understood that the examples are provided for further illustration of the present application and are not to be construed as limiting the scope of the present application.
Example 1: growth NaI:0.2at% TlI,1.0at% 6 LiI，0.05at％SrI 2 A crystal having a crystal composition of the formula (Na 0.9875 6 Li 0.01 Tl 0.002 Sr 0.0005 )I
Growth 6 Li doping concentration of 1.0%, tl doping concentration of 0.2%, srI 2 Alkaline earth metal doped NaI with doping concentration of 0.06%: 6 li, tl crystals. 81.0g of NaI was weighed out, 6 0.73g of LiI, 0.36g of TlI and 0.94g of SrI are fully mixed and put intoA flat bottom quartz crucible and sealing;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to ensure that the temperature reaches 750 ℃ and is kept for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the quartz crucible in the furnace body at the reducing speed of 2mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at a speed of 15 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals. Similarly, the grown crystals were transparent and crack-free, and contained no inclusions.
It is noted that the alkaline earth doping concentration in each example was obtained by ICP-OES testing.
Example 2: growth NaI:0.1at% TlI,1.0at% 6 LiI，0.1at％SrI 2 A crystal of the general formula (Na) 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 )I。
Growth 6 Li doping concentration of 1.0%, tl doping concentration of 0.1%, srI 2 Alkaline earth metal doped NaI with doping concentration of 0.1%: 6 li, tl crystals. 81.93g of NaI is weighed out, 6 LiI0.76 g，TlI 0.18g，SrI 2 after 0.19g of the mixture is fully mixed, the mixture is placed into a flat-bottom quartz crucible and sealed;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to enable the temperature to reach 800 ℃ and preserving heat for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the quartz crucible in the furnace body at the reducing speed of 4mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at a speed of 10 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals.
Grown (Na) 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) The I crystal is transparent and has no crack and no inclusion. The crystals were tested for their properties after cutting, grinding and polishing. FIG. 3 shows the structure of example 1 (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) I crystal and NaI doped: 6 an X-ray excitation emission spectrum of Li, tl crystals; as can be seen from FIG. 3, the structure of the alkaline earth doped crystal is similar to that of the doped crystal, (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) The X-ray excitation emission peak of the I crystal is located at 415 nm. FIG. 4 shows (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) I crystal with undoped NaI: 6 gamma energy spectrum of Li, tl crystal; it can be seen that the method consists of 137 In the pulse height spectrum of Cs radioactive source excitation, (Na) 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) The energy resolution of the full-energy peak of the I crystal at 662keV is about 5.4%; compared to undoped NaI: 6 the resolution of Li, tl crystals (7.0%) is significantly improved.
Fig. 5 and 6 are undoped NaI: 6 neutron spectrum and gamma spectrum of Li and Tl crystal, and calculated discrimination capability FOM value scattered point spectrum of the two; fig. 7 and 8 are (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) And I neutron spectrum and gamma spectrum of the crystal, and the calculated discrimination capability FOM value scattered point spectrum of the neutron spectrum and the gamma spectrum of the crystal. Typically, the neutron and gamma ray resolving power of a crystal is characterized by FOM values. As can be seen, (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) I crystal and undoped NaI: 6 the FOM values corresponding to the Li and Tl crystals are 5.72 and 4.56 respectively, namely the neutron and gamma ray discrimination capability of the crystal after the alkaline earth metal Sr is doped is improved.
No other properties of the crystal after alkaline earth doping, such as changes in properties such as decay time, were observed. As shown in FIG. 9 (Na 0.988 6 Li 0.01 Tl 0.001 Sr 0.001 ) I crystal with undoped NaI: 6 the scintillation decay time of the Li and Tl crystals can be well fitted by a double exponential function, and the fast component of the decay time is 210ns and accounts for 8%; the slow component is 1250ns, 92%, and undoped NaI: 6 the Li and Tl crystals have little difference in performance, so that the alkaline earth metal doping forms new defects in the lithium thallium co-doped sodium-based halogen scintillation crystal, the energy nonlinear response of the crystal is optimized, the energy resolution of the scintillation crystal and the neutron/gamma discrimination capability are well improved, and other performances are not influenced.
Example 3: growth NaI 0.1at% TlBr 8at% 6 LiCl，0.1at％CaI 2 A crystal having a crystal composition of the formula (Na 0.918 6 Li 0.08 Tl 0.001 Ca 0.001 )X
Growth 6 Li doping concentration of 8%, tl doping concentration of 0.1%, caI 2 Alkaline earth metal doped NaI with doping concentration of 0.1%: 6 li, tl crystals. 80.72g of NaI is weighed out, 6 LiCl1.95 g，TlI 0.19g，CaI 2 after 0.17g of the mixture is fully mixed, the mixture is put into a flat-bottom quartz crucible and sealed;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to enable the temperature to reach 800 ℃ and preserving heat for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the quartz crucible in the furnace body at the reducing speed of 3mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at the speed of 8 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals. The grown crystal is transparent and has no cracks and no inclusion.
Example 4: growth NaI:0.2at% TlI,1.0at% 6 LiI，0.2at％CaI 2 A crystal of the general formula (Na) 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 )I
Growth 6 Li doping concentration of 1.0%, tl doping concentration of 0.2%, caI 2 Alkaline earth metal doped NaI with doping concentration of 0.2%: 6 li, tl crystals. 81.61g of NaI was weighed out, 6 LiI0.73 g，TlI0.37g,LaI 3 0.32g and fully mixing, putting into a flat bottom quartz crucible and sealing;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to ensure that the temperature reaches 750 ℃ and is kept for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the quartz crucible in the furnace body at the reducing speed of 2mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at a speed of 15 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals.
Grown (Na) 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) The X crystal is transparent and has no crack and no inclusion. FIG. 10 shows (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) X and undoped NaI: 6 an X-ray excitation emission spectrum of Li, tl crystals; (Na) 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) The X-ray excitation emission peak of the X-crystal is located at 420 nm. Experimental results prove that different dopants and different doping concentrations have no influence on the X-ray luminescence spectrum of the crystal. FIG. 11 is (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) X crystal with undoped NaI: 6 gamma energy spectrum of Li, tl crystal; from the following components 137 The pulse height spectrum of Cs radioactive source excitation is visible, (Na) 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) The energy resolution of the full-energy peak of the X crystal at 662keV is about 6.1% higher than undoped NaI: 6 the resolution of Li, tl crystals 7.0%, experimental results prove that the doping of alkaline earth Ca effectively optimizes the crystalsEnergy resolution.
Fig. 12 and 13 show (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) FOM scatter plot of crystals. As shown in FIG. 3, (Na) 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) The screening capability FOM value of the X crystal is 5.85, which is higher than that of undoped NaI: 6 of Li, tl crystal (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) X (4.56), it can be seen that alkaline earth Ca doping effectively enhances the resolving power of neutrons and gamma rays of the crystal.
Likewise, other properties of the alkaline earth Ca doped crystals did not show significant changes, as shown in fig. 14 (Na 0.986 6 Li 0.01 Tl 0.002 Ca 0.002 ) X crystal with undoped NaI: 6 a scintillation decay time diagram of the Li, tl crystal; doping of the alkaline earth metal Ca shortens the scintillation decay time of the crystal but has little effect. The scintillation decay time of the crystal sample can be well fitted by a double exponential function, and the fast component of the decay time is 215ns and accounts for 10%; the slow component is 1240ns, accounting for 90%.
Example 5: growth NaI:0.2at% TlCl 1.0at% 6 LiI，0.4at％BaI 2 The crystal composition formula is (Na 0.984 6 Li 0.01 Tl 0.002 Ba 0.004 )X
Growth 6 Li doping concentration of 1.0%, tl doping concentration of 0.2%, baI 2 Alkaline earth metal doped NaI with doping concentration of 0.04%: 6 li, tl crystals. 81.18g of NaI was weighed out, 6 LiI 0.73g，TlCl0.26 g,SmI 2 after being fully mixed, 0.86gg is put into a cylindrical quartz crucible and sealed;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to enable the temperature to reach 900 ℃ and preserving heat for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the crucible in the furnace body at the reducing speed of 5mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at a speed of 20 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals. Similarly, the alkaline earth metal Ba doped crystal is transparent and has no cracks and no inclusion.
Example 6: growth NaI 0.2at% TlI,2at% 6 LiF,0.1at％MgI 2 A crystal having a crystal composition of the formula (Na 0.977 6 Li 0.02 Tl 0.002 Mg 0.001 )X
Growth 6 The doping concentration of Li is 2.0%, the doping concentration of Tl is 0.2%, mgI 2 Alkaline earth metal doped NaI with doping concentration of 0.1%: 6 li, tl crystals. 82.22g of NaI was weighed out, 6 LiF0.82 g，TlI 0.37g，MgI 2 after 0.16g of the mixture is fully mixed, the mixture is put into a cone-bottom quartz crucible and sealed;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to keep the temperature at 850 ℃ for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the quartz crucible in the furnace body at the reducing speed of 1mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at a speed of 15 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals.
Example 7: growth NaI 0.1at% TlI 8at% 6 LiCl，0.1at％MgI 2 A crystal having a crystal composition of the formula (Na 0.918 6 Li 0.08 Tl 0.001 Mg 0.001 )X
Growth 6 Li doping concentration is 8%, tl doping concentration is 0.1%, mgI 2 Alkaline earth metal doped NaI with doping concentration of 0.1%: 6 li, tl crystals. 80.73g of NaI is weighed out, 6 LiCl1.95 g，TlI 0.19g,MgI 2 0.16g, fully mixing, and putting into a cone bottom quartz crucibleAnd sealing;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to enable the temperature to reach 800 ℃ and preserving heat for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the quartz crucible in the furnace body at the reducing speed of 3mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at the speed of 8 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals.
Example 8: growth NaI 0.2at% TlBr,2at% 6 LiI，0.01at％MgI 2 A crystal having a composition formula (Na 0.9779 6 Li 0.02 Tl 0.002 Mg 0.0001 )X
Growth 6 Li doping concentration of 0.1%, tl doping concentration of 0.2%, mgI 2 Alkaline earth metal doped NaI with doping concentration of 0.01%: 6 li, tl crystals. 82.09 g of NaI was weighed out in a glove box, 6 LiI0.47 g，TlI 0.32g，ScI 3 after 0.16g of the mixture is fully mixed, the mixture is put into a cone-bottom quartz crucible;
vertically placing the sealed quartz crucible in the middle of a crystal growth furnace by a descending method; heating the crystal growth furnace to keep the temperature at 850 ℃ for a certain time until the raw materials are completely melted and uniformly mixed; and regulating the position and the furnace temperature of the crucible, reducing the temperature of the bottom of the crucible to about the melting point of the scintillation crystal, then reducing the quartz crucible in the furnace body at the reducing speed of 5mm/h, and starting nucleation and growth of the crystal from the bottom of the crucible until the melt is completely solidified and crystallized.
The furnace temperature is reduced at a speed of 5 ℃/h, and when the thermocouple is cooled to room temperature, the alkaline earth metal doped NaI is taken out: 6 li, tl crystals. Examples 6 to 8 are alkaline earth Mg doped lithium thallium co-doped sodium based halogen scintillation crystals of varying content, as such, alkaline earth Mg doped crystals are transparent and crack free, free of inclusion. Thus, it can be seen that theThe method provided by the application can obtain different alkaline earth metal doped lithium thallium co-doped sodium-based halogen scintillation crystals, and the alkaline earth metal doped lithium thallium co-doped sodium-based halogen scintillation crystals have better neutron and gamma ray resolving power.
The foregoing is a further detailed description of the application in connection with the preferred embodiments, and it is not intended that the application be limited to the specific embodiments described. It will be evident to those skilled in the art that the application is not limited to the details of the foregoing illustrative embodiments, and that the present application may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Claims (9)
1. The lithium thallium co-doped sodium-based halogen scintillation crystal is characterized by comprising the following general formula: (Na) 1-a-b-c 6 Li a Tl b M c )X；
X is one or more of F, cl, br, I;
m is Ca, sr, mg or Ba;
wherein a is more than 0 and less than or equal to 0.2, b is more than 0 and less than or equal to 0.01,0, and c is more than 0 and less than or equal to 0.1.
2. The lithium thallium co-doped sodium-based halogen scintillation crystal of claim 1, wherein c is 0.001 < 0.05.
3. The lithium thallium co-doped sodium-based halogen scintillation crystal of claim 1, wherein the scintillation crystal is (Na 1-a-b-c 6 Li a Tl b Sr c ) I, wherein c is more than 0 and less than or equal to 0.001.
4. The lithium thallium co-doped sodium-based halogen scintillation crystal of claim 3, wherein the scintillation crystal has an energy resolution of the full-energy peak at 662keV of 5.4% or less.
5. The lithium thallium co-doped sodium-based halogen scintillation crystal of claim 1, wherein the scintillation crystal is (Na 1-a-b-c 6 Li a Tl b Ca c ) X, wherein c is more than 0 and less than or equal to 0.002.
6. The lithium thallium co-doped sodium-based halogen scintillation crystal of claim 1, wherein the lithium thallium co-doped sodium-based halogen scintillation crystal is a single crystal.
7. A method for preparing the lithium thallium co-doped sodium-based halogen scintillation crystal of claim 1, comprising the steps of:
according to the general formula (Na) 1-a-b-c 6 Li a Tl b M c ) X respectively weighing sodium iodide, lithium halide, thallium halide and halogenated alkaline earth metal;
mixing the weighed raw materials, placing the raw materials into a crucible and sealing;
vertically placing the sealed crucible in a growth furnace, and heating the crucible to 700-900 ℃;
the crucible descends in the growth furnace at a descending speed of 2-6 mm/h after the raw materials are melted;
and after the crystal growth is finished, the growth furnace is cooled to room temperature, and the crucible is taken out to obtain the lithium thallium co-doped sodium-based halogen scintillation crystal.
8. The method of claim 7, wherein the bottom of the crucible has a capillary tube to which a seed crystal is fixed.
9. An application, characterized in that the lithium thallium co-doped sodium-based halogen scintillation crystal of any one of claims 1 to 6 is applied to neutron detection or gamma-neutron dual-mode detection.
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