阅读说明：本技术 一种闪烁晶体及其制备方法与应用 (Scintillation crystal and preparation method and application thereof ) 是由 唐华纯 李中波 张亮 于 2020-05-28 设计创作，主要内容包括：本发明涉及人工闪烁晶体技术领域,特别是涉及一种闪烁晶体及其制备方法与应用。所述闪烁晶体的化学式为CsI：Tl(x)：Cu(y),其中0.05≤x≤0.1；0.01≤y≤0.1。本发明采用共掺杂配方及改进的下降方法制备出的碘化铯晶体既能保持原有的光产额,又能有效降低余辉,特别是在辐照射线关闭后的前50ms的时间段内的余辉有显著改善,可满足高速射线成像检测需求。(The invention relates to the technical field of artificial scintillation crystals, in particular to a scintillation crystal and a preparation method and application thereof. The scintillation crystal has the chemical formula CsI: tl (x): cu (y), wherein x is more than or equal to 0.05 and less than or equal to 0.1; y is more than or equal to 0.01 and less than or equal to 0.1. The cesium iodide crystal prepared by adopting the co-doping formula and the improved reduction method not only can keep the original light yield, but also can effectively reduce the afterglow, particularly obviously improves the afterglow in the first 50ms time period after the irradiation ray is turned off, and can meet the requirement of high-speed radiographic detection.)

1. A scintillation crystal having a chemical formula CsI: tl (x): cu (y), wherein x is more than or equal to 0.05 and less than or equal to 0.1; y is more than or equal to 0.01 and less than or equal to 0.1.

2. The scintillation crystal of claim 1, wherein 0.06 ≦ x ≦ 0.08.

3. The scintillation crystal of claim 1, wherein 0.02 ≦ y ≦ 0.07.

4. A method of making a scintillation crystal according to any one of claims 1 to 3 comprising: and heating and melting the mixture of cesium iodide powder, thallium iodide and cuprous iodide, and further performing crystal growth to obtain the cesium iodide crystal.

5. The method for preparing a scintillation crystal according to claim 4, wherein the molar ratio of cesium iodide powder to thallium iodide is 1: 0.05 to 0.1; the molar ratio of the cesium iodide powder to the cuprous iodide is 1: 0.01 to 0.1.

6. The method of preparing a scintillation crystal of claim 4, further comprising any one or more of the following technical features:

A1) reacting the mixture at 195-205 ℃, vacuum drying, sealing and melting;

A2) the melting temperature is 700-750 ℃;

A3) in the crystal growth process, the temperature is reduced to 600-650 ℃ at the speed of 1.5-3.0 mm/h; the temperature gradient of a crystal growth interface is 28-32 ℃/cm; and after the crystal growth is finished, cooling to room temperature at the speed of 30-50 ℃/h.

7. The method of preparing a scintillation crystal of claim 4, wherein said cesium iodide powder is prepared by a method comprising the steps of:

1) purifying a cesium iodide raw material under a vacuum condition, removing low-temperature impurities, and performing primary crystallization to obtain a crystalline material;

2) purifying at least part of the crystallization material obtained in the step 1), removing metal ion impurities, and performing secondary crystallization to obtain cesium iodide powder.

8. The method of preparing a scintillation crystal of claim 7 wherein in step 1) said low temperature impurities comprise a combination of one or more of Li, Al, Zn.

9. The method of preparing a scintillation crystal of claim 7, further comprising any one or more of the following technical features:

B1) in the step 2), in the purification treatment step, at least part of the crystallization material is dissolved in water to prepare a cesium iodide saturated solution, hydroxylamine is added, hydrazine hydrate is used for gradually adjusting the pH value of the solution until metal ion impurities form precipitates, and then the precipitates are filtered;

B2) in the step 2), the metal ion impurities comprise one or more of K, Mg, Zn, Ba, Ni and Fe.

10. Use of a scintillation crystal according to any one of claims 1 to 3 in the field of radiation detection.

Technical Field

The invention relates to the technical field of artificial scintillation crystals, in particular to a scintillation crystal and a preparation method and application thereof.

Background

The detector component mainly comprises two parts, namely a photodiode and a scintillator, and is an important component in ray detection devices such as a security check machine, an industrial CT (computed tomography) machine and a computed tomography scanner. The scintillator in the detector emits visible light after absorbing high-energy rays, and the performance of the scintillator greatly influences the overall performance index and the detection effect of the ray detection device. The current scintillators are mainly based on artificial crystals. Cesium iodide crystals are the most widely used in X-ray security equipment and industrial CT machines in the world at present.

The cesium iodide crystal is a halide scintillator with excellent performance, the light output of the cesium iodide crystal is 85% of that of a sodium iodide crystal, the light-emitting wavelength of the cesium iodide crystal is 550nm, and the cesium iodide crystal can be effectively matched with a silicon photodiode, so that the reading system of a detector is greatly simplified, and in addition, the cesium iodide crystal has the advantages of being a cubic crystal system, low in melting point (only 621 ℃), mature in growth technology, easy to grow large-size crystals, low in price and the like, so that the cesium iodide crystal is widely applied to the fields of high-energy physics, safety inspection, industrial nondestructive detection, nuclear medicine imaging and the like. But CsI: the long afterglow (20 ms: 1-5%) characteristic of Tl seriously affects the application of Tl in the technical field of high-speed radiation imaging, and the problems of high-speed X-ray imaging blurring, image contrast reduction, ghost generation caused by X-CT influence and the like are caused by the long afterglow, particularly, with the continuous development of society, pursuing and improving the working efficiency of various industries, and providing higher scanning speed requirements for security inspection equipment, industrial CT equipment and the like: for example, the over-wrapping speed of security inspection equipment in the logistics field is expected to be 3-4 times that of conventional security inspection equipment, so that the development of ultra-low afterglow rapid cesium iodide crystals is a difficult problem and a hot spot which are concerned for many years.

At present, the afterglow of cesium iodide crystals is mainly inhibited by a co-doping mode, and doped ions mainly comprise Eu²⁺And Bi³⁺. The co-doping of the ions has certain effect on inhibiting the afterglow intensity of the crystal, but the afterglow is reduced, the light yield of the crystal is also obviously reduced, the light yield of the crystal is adversely affected, and the comprehensive advantages of the cesium iodide scintillation crystal are greatly weakened. Therefore, finding a method which can reduce the afterglow (especially the afterglow value within the first 50ms or even shorter time after the irradiation ray is turned off) of the cesium iodide crystal and has no adverse effect on the light yield is very important for the application development of the cesium iodide crystal.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, it is an object of the present invention to provide a scintillation crystal, and a method of making and using the same.

To achieve the foregoing and other related objects, one aspect of the present invention provides a scintillation crystal having a chemical formula CsI: tl (x): cu (y), wherein x is more than or equal to 0.05 and less than or equal to 0.1; y is more than or equal to 0.01 and less than or equal to 0.1.

In some embodiments of the invention, the 0.06 ≦ x ≦ 0.08.

In some embodiments of the present invention, the 0.02. ltoreq. y.ltoreq.0.07.

In another aspect, the present invention provides a method for preparing a scintillation crystal according to the present invention, comprising: and heating and melting the cesium iodide powder and the mixture of thallium iodide and cuprous iodide, and further performing crystal growth to obtain the cesium iodide crystal.

In some embodiments of the invention, the molar ratio of cesium iodide powder to thallium iodide is 1: 0.05 to 0.1; the molar ratio of the cesium iodide powder to the cuprous iodide is 1: 0.01 to 0.1.

In some embodiments of the invention, the mixture is reacted at 195-205 ℃, vacuum-dried, sealed and melted;

in some embodiments of the invention, the temperature of the melting is 700 to 750 ℃;

in some embodiments of the invention, the crystal growth process is carried out by cooling to 600-650 ℃ at a speed of 1.5-3.0 mm/h; the temperature gradient of a crystal growth interface is 28-32 ℃/cm; and after the crystal growth is finished, cooling to room temperature at the speed of 30-50 ℃/h.

In some embodiments of the present invention, the method for preparing cesium iodide powder comprises the steps of:

1) purifying a cesium iodide raw material under a vacuum condition, removing low-temperature impurities, and performing primary crystallization to obtain a crystalline material;

2) purifying at least part of the crystallization material obtained in the step 1), removing metal ion impurities, and performing secondary crystallization to obtain cesium iodide powder.

In some embodiments of the invention, in step 1), the low temperature impurities comprise a combination of one or more of Li, Al, Zn.

In some embodiments of the present invention, in step 2), in the purification treatment step, at least part of the crystallized material is dissolved in water to obtain a saturated solution of cesium iodide, hydroxylamine is added, hydrazine hydrate is used to gradually adjust the pH of the solution until metal ion impurities form precipitates, and then the precipitates are filtered.

In some embodiments of the invention, in step 2), the metal ion impurities comprise a combination of one or more of K, Mg, Zn, Ba, Ni, Fe.

In another aspect, the invention provides the use of a scintillation crystal according to the invention in the field of radiation detection.

Drawings

Fig. 1 is a graph comparing the light output of example 1 and comparative example 1.

Fig. 2 is a graph comparing the light output of example 2 and comparative example 1.

Fig. 3 is a graph comparing the light output of example 3 and comparative example 1.

Fig. 4 is a graph comparing the light output of example 4 and comparative example 1.

Fig. 5 is a graph comparing the light output of example 5 and comparative example 1.

FIG. 6 is a comparison of afterglow in examples 1 to 5 and comparative example 1.

Detailed Description

The inventor has surprisingly found through a large number of experiments that the chemical purification and secondary crystallization of high-purity (4N) cesium iodide powder before crystal growth are carried out to reduce harmful impurities in the raw materials: K. mg, Zn and the like, particularly radioactive impurities K, avoid the adverse effect on the afterglow of the crystal, the prepared cesium iodide (CsI) single crystal scintillator doped with one or more elements of Tl and Cu has small afterglow, no influence on the light yield of the crystal, high matching degree with a photodiode, and can be widely applied to the fields of radiation detection technical devices such as industrial security inspection machines, nuclear medicine imaging and the like. On the basis of this, the present invention has been completed.

A first aspect of the invention provides a scintillation crystal having a chemical formula CsI: tl (x): cu (y), wherein x is more than or equal to 0.05 and less than or equal to 0.1; y is more than or equal to 0.01 and less than or equal to 0.1.

In the scintillation crystal provided by the invention, the value range of x is optionally 0.05-0.06, 0.06-0.07, 0.07-0.08, 0.08-0.09 and 0.09-0.1; x is more than or equal to 0.05 and less than or equal to 0.07, and x is more than or equal to 0.07 and less than or equal to 0.09; x is more than or equal to 0.05 and less than or equal to 0.08, and x is more than or equal to 0.08 and less than or equal to 0.10; x is more than or equal to 0.05 and less than or equal to 0.09; x is more than or equal to 0.06 and less than or equal to 0.09; x is more than or equal to 0.06 and less than or equal to 0.08; or x is more than or equal to 0.07 and less than or equal to 0.1. The advantages within the value range are as follows: different doping concentrations can be chosen depending on the context of the crystal application: for example, when the crystal is used for the detection of α particles, x is recommended to be 0.1.

Preferably, the value range of x is more than or equal to 0.06 and less than or equal to 0.08.

In the scintillation crystal provided by the invention, the value range of y is optionally more than or equal to 0.01 and less than or equal to 0.02; y is more than or equal to 0.02 and less than or equal to 0.03; y is more than or equal to 0.03 and less than or equal to 0.04; y is more than or equal to 0.04 and less than or equal to 0.05; y is more than or equal to 0.05 and less than or equal to 0.06; y is more than or equal to 0.06 and less than or equal to 0.07; y is more than or equal to 0.07 and less than or equal to 0.08; y is more than or equal to 0.08 and less than or equal to 0.09; y is more than or equal to 0.09 and less than or equal to 0.1; y is more than or equal to 0.01 and less than or equal to 0.03; y is more than or equal to 0.03 and less than or equal to 0.05; y is more than or equal to 0.05 and less than or equal to 0.07; y is more than or equal to 0.07 and less than or equal to 0.09; y is more than or equal to 0.01 and less than or equal to 0.04; y is more than or equal to 0.04 and less than or equal to 0.08; y is more than or equal to 0.08 and less than or equal to 0.1; y is more than or equal to 0.01 and less than or equal to 0.05; y is more than or equal to 0.05 and less than or equal to 0.1; y is more than or equal to 0.02 and less than or equal to 0.09; y is more than or equal to 0.03 and less than or equal to 0.07; or y is more than or equal to 0.04 and less than or equal to 0.06. The advantages within the value range are as follows: different doping amounts can be selected according to the specific requirements of use to obtain afterglow value products of different levels.

Preferably, the value range of x is more than or equal to 0.02 and less than or equal to 0.07.

A second aspect of the invention provides a method of making a scintillation crystal of the first aspect of the invention, comprising: and heating and melting the cesium iodide powder and the mixture of thallium iodide and cuprous iodide, and further performing crystal growth to obtain the cesium iodide crystal.

In the preparation method of the scintillation crystal provided by the invention, the molar ratio of cesium iodide powder to thallium iodide is 1: 0.05 to 0.1. In some embodiments, the molar ratio of cesium iodide powder to thallium iodide is 1: 0.05 to 0.06; 1: 0.06 to 0.07; 1: 0.07 to 0.08; 1: 0.08 to 0.09; 1: 0.09-0.1; 1: 0.05 to 0.07; 1: 0.07 to 0.09; 1: 0.05 to 0.08; 1: 0.08 to 0.10; 1: 0.05 to 0.09; 1: 0.06 to 0.09; 1: 0.06 to 0.08; or 1: 0.07 to 0.1.

In the preparation method of the scintillation crystal provided by the invention, the molar ratio of the cesium iodide powder to the cuprous iodide is 1: 0.01 to 0.1. In some embodiments, the molar ratio of cesium iodide powder to cuprous iodide is 1: 0.01 to 0.02; 1: 0.02 to 0.03; 1: 0.03 to 0.04; 1: 0.04 to 0.05; 1: 0.05 to 0.06; 1: 0.06 to 0.07; 1: 0.07 to 0.08; 1: 0.08 to 0.09; 1: 0.09-0.1; 1: 0.01 to 0.03; 1: 0.03 to 0.05; 1: 0.05 to 0.07; 1: 0.07 to 0.09; 1: 0.01 to 0.04; 1: 0.04 to 0.08; 1: 0.08 to 0.1; 1: 0.01 to 0.05; 1: 0.05 to 0.1; 1: 0.02 to 0.09; 1: 0.03 to 0.07; or 1: 0.04 to 0.06.

In the preparation method of the scintillation crystal, the OH of the mixture is removed at 195-205 DEG C^-Then, vacuum drying, sealing and melting are carried out. The melting temperature is 700-750 ℃. In the crystal growth process, the temperature is reduced to 600-650 ℃ at the speed of 1.5-3.0 mm/h; the temperature gradient of a crystal growth interface is 28-32 ℃/cm; and after the crystal growth is finished, cooling to room temperature at the speed of 30-50 ℃/h. In a specific embodiment, firstly, raw material cesium iodide is subjected to OH < - > removal at 195-205 ℃, then is subjected to vacuum drying, and then is put into a crucible to be vacuumized and sealed; placing the loaded crucible in a descending furnace, melting, and controlling the temperature of the melting material to be 700-750 ℃; starting crystal growth after the melting is finished, enabling the crucible to move downwards at a constant speed and pass through a region with the temperature of 600-650 ℃ in a descending furnace, wherein the descending speed is 1.5-3.0 mm/h, and the temperature gradient of a crystal growth interface is 28-32 ℃/cm; after the crystal growth is finished, cooling to room temperature at the rate of 30-50 ℃/h; the crucible is taken out, and the crystal is peeled from the crucible to obtain the scintillation single crystal of the invention. The crucible is a quartz crucible with the inner wall plated with a carbon film; the interior of the furnace chamber of the descending furnace is axially divided into a high temperature area, a middle temperature area and a low temperature area: the temperature of the high-temperature area is controlled to be 700-750 ℃, the temperature of the middle-temperature area is controlled to be 600-650 ℃, and the temperature of the low-temperature area is controlled to be 300-350 ℃.

In the preparation method of the scintillation crystal provided by the invention, the preparation method of the cesium iodide powder comprises the following steps:

1) purifying a cesium iodide raw material under a vacuum condition, removing low-temperature impurities, and performing primary crystallization to obtain a crystalline material;

2) purifying at least part of the crystallization material obtained in the step 1), removing metal ion impurities, and performing secondary crystallization to obtain cesium iodide powder;

in the preparation method of cesium iodide powder, step 1) is to sublimate and desublimate a cesium iodide raw material under vacuum condition, purify the cesium iodide raw material, remove low-temperature impurities, and perform primary crystallization to obtain a crystal material, wherein the low-temperature impurities comprise one or more of Li, Al, Zn and the like, in general, the cesium iodide raw material such as a high-purity (4N) cesium iodide raw material is put into a quartz crucible in a vacuum sublimation and desublimating purification tank, a vacuum pump is started, and when the vacuum degree in the tank is higher than 1.0 × 10^-2And when Pa is reached, the temperature is raised to 150-170 ℃, the temperature is kept constant until the cesium iodide raw material is completely sublimated, and the heating maximum temperature of the material-containing quartz crucible is not more than 175 ℃. In one embodiment, the vacuum sublimation and sublimation purifying tank is a vacuum sublimation and sublimation purifying tank (not manufactured by standard) developed by the company. And taking out the sublimated and desublimated cesium iodide material, putting the cesium iodide material into a quartz tube plated with a carbon film, and carrying out primary crystallization growth after vacuumizing.

In the preparation method of cesium iodide powder, step 2) is to purify at least part of the crystallization material obtained in step 1), remove metal ion impurities, and then perform secondary crystallization to obtain cesium iodide powder. In the step 2), in the purification treatment step, at least part of the crystallized material is dissolved in water to prepare a cesium iodide saturated solution, hydroxylamine is added, hydrazine hydrate is used for gradually adjusting the pH value of the solution until metal ion impurities form precipitates, the solution is made to be weakly acidic, and the filtering is performed. The metal ion impurities include one or more of K, Mg, Zn, Ba, Ni, Fe, etc. In one embodiment, the filtration step may employ microfiltration.

Specifically, at least part of the crystallized material can be 1/2-4/5 of the crystallized material obtained in the step 1).

Further, at least part of the crystallization material is dissolved in pure water with the constant temperature of 40-60 ℃ to form a cesium iodide saturated solution.

A third aspect of the invention provides use of the scintillation crystal provided by the first aspect of the invention in the field of radiation detection. The radiation detection field specifically comprises the fields of industrial security inspection machines, X-ray security inspection equipment, industrial CT machines, nuclear medicine imaging and the like. The scintillation crystal in the detector emits visible light after absorbing high-energy rays, and the performance of the scintillation crystal greatly influences the overall performance index and the detection effect of the ray detection device.

The invention has the beneficial effects that:

aiming at the afterglow problem of the existing cesium iodide crystal, the invention provides a complete method for purifying, co-doping a formula and growing a crystal of CsI powder, which is easy to realize commercially, and has the characteristics of low cost, easy batch manufacturing, stability and reliability. The CsI powder purified by the method has high purity and low content of harmful impurities, particularly the content of radioactive impurities K is greatly reduced, the cesium iodide crystal prepared by adopting a co-doping formula and an improved reduction method can not only keep the original light output performance, but also effectively reduce afterglow, particularly obviously improve the afterglow in the first 50ms time period after the X-ray irradiation is closed, effectively improve the high-speed radiographic imaging quality and meet the requirements of high-speed radiographic imaging detection.

The following examples are provided to further illustrate the advantageous effects of the present invention.

In order to make the objects, technical solutions and advantageous technical effects of the present invention more clear, the present invention is further described in detail below with reference to examples. However, it should be understood that the embodiments of the present invention are only for explaining the present invention and are not for limiting the present invention, and the embodiments of the present invention are not limited to the embodiments given in the specification. The examples were prepared under conventional conditions or conditions recommended by the material suppliers without specifying specific experimental conditions or operating conditions.

Furthermore, it is to be understood that one or more method steps mentioned in the present invention does not exclude that other method steps may also be present before or after the combined steps or that other method steps may also be inserted between these explicitly mentioned steps, unless otherwise indicated; it is also to be understood that a combined connection between one or more devices/apparatus as referred to in the present application does not exclude that further devices/apparatus may be present before or after the combined device/apparatus or that further devices/apparatus may be interposed between two devices/apparatus explicitly referred to, unless otherwise indicated. Moreover, unless otherwise indicated, the numbering of the various method steps is merely a convenient tool for identifying the various method steps, and is not intended to limit the order in which the method steps are arranged or the scope of the invention in which the invention may be practiced, and changes or modifications in the relative relationship may be made without substantially changing the technical content.

In the following examples, reagents, materials and instruments used are commercially available unless otherwise specified.