Multi-doped lanthanum bromide scintillation crystal and preparation method thereof

Abstract

The invention relates to a multi-doped lanthanum bromide scintillation crystal and a preparation method thereof. The light-emitting non-uniformity of the head part and the tail part of the crystal is not more than 0.1%, the scintillation performance of the head part and the tail part of the crystal is consistent, the crystal quality is greatly improved, the application range of the crystal is widened, and the market prospect is wide. According to the preparation method disclosed by the embodiment of the invention, the preparation method of the multi-doped lanthanum bromide scintillation crystal in a secondary crystal growth mode by taking the crystal which is synthesized by a horizontal zone melting method and is free of surface and tail impurity layers as a raw material is provided for the first time, the operation is simple, the raw materials are easy to obtain, and the implementation of the whole preparation process is easy to realize. The problems of poor luminescence uniformity and the like caused by a component segregation phenomenon are avoided, the luminescence nonuniformity of the head part and the tail part of the crystal is improved to 0.07% from 1.12%, the energy resolution of the crystal is improved to 2.33% at 662 KeV from 2.94% at 662 KeV, and the quality of the crystal is greatly improved.

Description

A multi-doped lanthanum bromide scintillation crystal and its preparation method Technical Field

[0001] This invention belongs to the field of scintillation crystal materials, and particularly relates to a multi-doped lanthanum bromide scintillation crystal and its preparation method. Background Technology

[0002] Scintillation crystals are functional materials that convert high-energy rays such as X-rays and gamma rays into ultraviolet-visible light. As core components of high-end detection equipment, they are widely used in fields such as security inspection, nuclear medicine imaging, geological exploration, and high-energy physics, possessing enormous market value and industrial scale. Cerium-doped lanthanum bromide (Ce:LaBr3) crystals are currently a hot topic in international research and application among novel inorganic scintillation crystals. They possess excellent characteristics such as high light output, fast decay time, and good energy resolution, surpassing the performance of traditional high-output sodium thallium iodide (NaI:Tl) scintillation crystals. They are the best-performing scintillation crystals discovered to date and are widely used in environmental monitoring, counter-terrorism security inspections, oil well logging, and high-energy physics. To meet the needs of national security and other fields, improving the energy resolution of Ce:LaBr3 crystals has become a research hotspot both domestically and internationally in recent years.

[0003] To improve the energy resolution of Ce:LaBr3 crystals, it is common practice to incorporate cations (such as Li) into the crystal. + Na + Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ (etc.). Due to the difference in radius between the doped cation and La... 3+ Ionic radius (e.g., Mg) 2+ The radius of the ion is 0.072 nm, La 3+ The ions (with a radius of 0.106 nm) have certain differences, and the segregation coefficient of the doped ions in the crystal is less than 1, which causes certain differences in the scintillation performance such as energy resolution at the head and tail of the crystal.

[0004] Patent CN101723433A discloses a method for preparing lanthanum cerium bromide crystals, the chemical composition of which includes a reinforcing agent, and the general chemical formula of the crystal is (Ce). x D 3y / 2 La 1-x-y Br3, where D represents a +2 valence ion reinforcing agent, can be one or a combination of elements from the group Mg, Ca, Sr, Ba, Zn, Cd, 0.01 ≤ x ≤ 0.99, 0.01 ≤ y ≤ 0.2, 0 ≤ x+y ≤1. It solves the crystal cracking problem through the pinning effect, and the grown crystal is crack-free and completely transparent, with an optimal energy resolution of 3.3%@662keV.

[0005] Since lanthanum bromide and the above-doped lanthanum bromide crystals are generally used as cylinders, the inconsistency in the scintillation performance between the head and the tail of the multi-ion-doped lanthanum bromide crystal will cause serious problems in key applications of detection equipment, affecting data accuracy, equipment reliability and overall system efficiency. Therefore, improvement is urgently needed. However, this problem has not been proposed by anyone so far, and the corresponding problems have not been solved either. Summary of the Invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a multi-doped lanthanum bromide scintillation crystal and a preparation method thereof.

[0007] According to one aspect of the present invention, a multi-doped lanthanum bromide scintillation crystal is provided, wherein the crystal is Ce x M y La (1-x-y) Br3, where M is one or a mixture of two of Mg, Ca, Sr, Ba, Y, Yb, Gd, 0 < x ≤ 0.2, 0 < y ≤ 0.01, and the non-uniformity of luminescence between the head and the tail of the crystal is not greater than 0.1%.

[0008] According to another aspect of the present invention, a preparation method of the multi-doped lanthanum bromide scintillation crystal described above is provided, wherein the method includes the following steps: performing the first crystal growth by the horizontal zone melting method to obtain an initial raw material crystal; removing the impurity layers on the surface and the tail of the initial raw material crystal to obtain a raw material crystal, and performing the second crystal growth with the raw material crystal as the growth raw material to obtain the multi-doped lanthanum bromide scintillation crystal.

[0009] By using the crystal obtained by the horizontal zone melting method and removing the impurity layers on the initial surface and the tail as the raw material crystal for further crystal growth, the non-uniformity of luminescence caused by the component segregation phenomenon is avoided. Moreover, through the implementation of the horizontal zone melting method, the purification of the raw material is achieved, and defects such as scattering and cracking caused by impurities are avoided, greatly improving the crystal quality.

[0010] Further, performing the first crystal growth by the horizontal zone melting method to obtain an initial raw material crystal includes: placing the uniformly mixed raw materials in a horizontal zone furnace, heating to completely melt the raw materials, and moving the heater to achieve crystal growth to obtain the initial raw material crystal.

[0011] Further, the raw materials are fully and uniformly mixed by ball milling with a planetary ball mill. The ball milling time is 12 - 48h, which can ensure that the raw materials are fully and uniformly mixed.

[0012] Further, in the horizontal zone furnace, the complete melting temperature of the raw materials is 810 - 835°C, and the moving speed of the heater is 1 - 10mm / h.

[0013] Furthermore, the removal of the impurity layer from the surface and tail of the initial raw material crystal is carried out in a glove box. The crystal remaining after removing the impurity layer from the surface and tail of the initial raw material crystal is crushed in the glove box, placed in a crucible, vacuumed, and sealed to isolate water and oxygen.

[0014] Furthermore, the process of growing the multi-doped lanthanum bromide scintillation crystal by using the raw material crystal with the impurity layer removed as the growth material includes: placing a crucible containing the raw material crystal with the impurity layer removed into a descending furnace, performing crystal growth by melting and drawing, and then cooling and annealing to obtain the crystal.

[0015] Furthermore, the crucible is placed in the high-temperature zone of a two-stage temperature-controlled descending furnace. The temperature of the upper and lower zones rises, causing the raw material in the crucible to melt completely. Then, it is drawn down for crystal growth. After the crystal growth is completed, the drawing down is stopped, and the temperature is lowered to room temperature to obtain the crystal.

[0016] The upper temperature zone rises to 840-900℃, and the lower temperature zone rises to 730-780℃, causing the raw materials in the crucible to melt completely.

[0017] Crystal growth is carried out by drawing the crucible down at a rate of 0.1-1.0 mm / h.

[0018] Specifically, the following steps are included: Weighing of raw materials: Using anhydrous LaBr3, CeBr3 and MBr2 / MBr3 (one or a mixture of two of Mg, Ca, Sr, Ba, Y, Yb, Gd, etc.) with a purity of 99.99% as raw materials, a certain weight of LaBr3, CeBr3 and MBr2 / MBr3 is weighed in a glove box according to the stoichiometric ratio, and then placed in a pre-cleaned quartz crucible.

[0019] Crucible sealing: After removing the quartz crucible from the glove box, quickly evacuate it and seal it.

[0020] Ball milling: After sealing the above-mentioned quartz crucible, place it in a planetary ball mill and ball mill for 12-24 hours to ensure that the raw materials are fully and evenly mixed.

[0021] Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to the melting point, hold it at that temperature for a period of time, then slowly move the melting zone and move the heater slowly at a speed of 1-10 mm / h to achieve crystal growth, and then cool it to room temperature.

[0022] Raw material processing: Take out the crystal from the horizontal zone furnace, place the grown crystal in a vacuum glove box, remove the impurity layer on the surface and tail to obtain the raw material crystal, grind the raw material crystal obtained by removing the impurity layer on the surface and tail in a mortar, and put it into a pre-cleaned quartz crucible.

[0023] Crucible sealing: After removing the quartz crucible from the vacuum glove box, quickly evacuate it and seal it.

[0024] Crystal growth: A quartz crucible is placed in a descending furnace. Using raw crystals with impurity layers removed as raw material, crystal growth is carried out in the descending furnace according to a pre-set program, including melting and drawing. The crystal is then cooled and annealed to obtain the final crystal. After growth is complete, the crystal is removed from the descending furnace for later use.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1. The multi-doped lanthanum bromide scintillation crystal of the present invention has a light emission non-uniformity of no more than 0.1% between the head and tail of the crystal, and the scintillation performance of the head and tail of the crystal is basically the same, which greatly improves the crystal quality, broadens the application range of the crystal, and has a broad market prospect.

[0026] 2. The preparation method of multi-doped lanthanum bromide scintillation crystal exemplified by this invention. This invention proposes for the first time a method for preparing multi-doped lanthanum bromide scintillation crystals using a secondary crystal growth process with surface and tail impurity layers removed, synthesized via a horizontal zone melting method. The method is simple to operate, uses readily available raw materials, and avoids problems such as poor luminescence uniformity caused by component segregation. The luminescence non-uniformity at the crystal head and tail is improved from 1.12% to 0.07%, and the crystal's energy resolution is increased from 2.94%@662keV to 2.33%@662keV, significantly improving crystal quality. Detailed Implementation

[0027] Based on the shortcomings of the existing technology, the present invention aims to fundamentally improve the luminescence uniformity of multi-doped lanthanum bromide scintillation crystals and improve the quality of the crystals through a novel technical approach.

[0028] To better understand the technical solution of the present invention, the present invention will be further described below with reference to specific embodiments.

[0029] Example 1 x=0.05, y=0.004 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 26.5g of CeBr3 raw material, and 1.65g of BaBr2 raw material, and then put them into a pre-cleaned quartz crucible.

[0030] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, the opening of the quartz crucible is sealed with an oxyhydrogen flame to isolate it from water and oxygen.

[0031] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 24 hours to ensure that the raw materials are fully and evenly mixed.

[0032] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 815°C, and slowly move the heater at a speed of 5 mm / h to achieve crystal growth.

[0033] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0034] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, the opening of the quartz crucible is sealed with an oxyhydrogen flame to isolate it from water and oxygen.

[0035] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 870℃ and the temperature of the lower zone was raised to 750℃. The temperature was maintained for 12 hours to completely melt the raw materials in the crucible. Then, the crystal was drawn down at a rate of 0.5 mm / h for crystal growth. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 15-50℃ / h, and the crystal was removed. The energy resolution at the crystal head was 2.43%@662keV, the energy resolution at the crystal tail was 2.52%@662keV, and the energy resolution inhomogeneity was 0.09%.

[0036] Example 2 x=0.04, y=0.005 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 725g of anhydrous LaBr3 raw material with a purity of 99.99%, 30.5g of CeBr3 raw material, and 2.48g of SrBr2 raw material, and then put them into a pre-cleaned quartz crucible.

[0037] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -4 Pa, the opening of the quartz crucible is sealed with an oxyhydrogen flame to isolate it from water and oxygen.

[0038] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 36 hours to ensure that the raw materials are fully and evenly mixed.

[0039] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 825°C, and slowly move the heater at a speed of 3 mm / h to achieve crystal growth.

[0040] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0041] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -4 Pa, the opening of the quartz crucible is sealed with an oxyhydrogen flame to isolate it from water and oxygen.

[0042] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 840℃ and the temperature of the lower zone was raised to 730℃. The temperature was held constant for 12 hours to completely melt the raw materials in the crucible. Then, the crystal was grown by drawing it down at a rate of 0.8 mm / h. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 15-50℃ / h, and the crystal was removed. The crystal was complete and transparent. The energy resolution at the crystal head was 2.34%@662keV, the energy resolution at the crystal tail was 2.41%@662keV, and the energy resolution inhomogeneity was 0.07%.

[0043] Example 3 x=0.06, y=0.002 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 32.1g of CeBr3 raw material, and 0.92g of YBr3 raw material, and then put them into a pre-cleaned quartz crucible.

[0044] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0045] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 48 hours to ensure that the raw materials are fully and evenly mixed.

[0046] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 820°C, and slowly move the heater at a speed of 4 mm / h to achieve crystal growth.

[0047] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0048] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0049] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descending furnace. The temperature of the upper zone was raised to 900℃ and the temperature of the lower zone was raised to 780℃, and the temperature was held constant for 24 hours to completely melt the raw materials in the crucible. Then, crystal growth was carried out by drawing the crystal down at a rate of 0.6 mm / h. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 20-50℃ / h, and the crystal was taken out. The crystal was complete and transparent. The energy resolution at the crystal head was 2.53%@662keV, the energy resolution at the crystal tail was 2.62%@662keV, and the energy resolution inhomogeneity was 0.09%.

[0050] Example 4 x=0.01, y=0.01 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 5.09g of CeBr3 raw material, and 5.56g of YbBr3 raw material, and then put them into a pre-cleaned quartz crucible.

[0051] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0052] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 12 hours to ensure that the raw materials are fully and evenly mixed.

[0053] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 835°C, and slowly move the heater at a speed of 1 mm / h to achieve crystal growth.

[0054] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0055] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0056] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 900℃ and the temperature of the lower zone was raised to 770℃. The temperature was maintained for 30 hours to completely melt the raw materials in the crucible. Then, crystal growth was carried out by drawing the crystal down at a rate of 0.4 mm / h. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 30℃ / h, and the crystal was taken out. The crystal was complete and transparent. The energy resolution at the crystal head was 2.45%@662keV, the energy resolution at the crystal tail was 2.53%@662keV, and the energy resolution inhomogeneity was 0.08%.

[0057] Example 5 x=0.1, y=0.005 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 56.02g of CeBr3 raw material, and 1.36g of MgBr2 raw material, and then put them into a pre-cleaned quartz crucible.

[0058] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0059] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 30 hours to ensure that the raw materials are fully and evenly mixed.

[0060] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 810°C, and slowly move the heater at a speed of 2 mm / h to achieve crystal growth.

[0061] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0062] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0063] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 845℃ and the temperature of the lower zone was raised to 750℃, and held at this temperature for 20 hours to completely melt the raw materials in the crucible. Then, crystal growth was carried out by drawing the crystal down at a rate of 0.6 mm / h. After crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 25℃ / h, and the crystal was removed. The crystal was complete and transparent. The energy resolution at the crystal head was 2.54%@662keV, the energy resolution at the crystal tail was 2.63%@662keV, and the energy resolution inhomogeneity was 0.09%.

[0064] Example 6 x=0.15, y=0.006 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 89.11g of CeBr3 raw material, and 1.88g of CaBr2 raw material, and then put them into a pre-cleaned quartz crucible.

[0065] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0066] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 30 hours to ensure that the raw materials are fully and evenly mixed.

[0067] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 815°C, and slowly move the heater at a speed of 10 mm / h to achieve crystal growth.

[0068] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0069] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0070] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 880℃ and the temperature of the lower zone was raised to 770℃. The temperature was maintained for 25 hours to completely melt the raw materials in the crucible. Then, the crystal was drawn down at a rate of 1.0 mm / h for crystal growth. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 30℃ / h, and the crystal was removed. The crystal was complete and transparent. The energy resolution at the crystal head was 2.47%@662keV, the energy resolution at the crystal tail was 2.55%@662keV, and the energy resolution inhomogeneity was 0.08%.

[0071] Example 7 x=0.2, y=0.01 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 126.93g of CeBr3 raw material, 1.84g of MgBr2 raw material, and 1.65g of SrBr2 raw material, and then put them into a pre-cleaned quartz crucible.

[0072] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0073] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 35 hours to ensure that the raw materials are fully and evenly mixed.

[0074] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 825°C, and slowly move the heater at a speed of 5 mm / h to achieve crystal growth.

[0075] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0076] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0077] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 870℃ and the temperature of the lower zone was raised to 760℃. The temperature was maintained for 25 hours to completely melt the raw materials in the crucible. Then, crystal growth was carried out by drawing the crystal down at a rate of 0.4 mm / h. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 50℃ / h, and the crystal was taken out. The crystal was complete and transparent. The energy resolution at the crystal head was 2.33%@662keV, the energy resolution at the crystal tail was 2.42%@662keV, and the energy resolution inhomogeneity was 0.09%.

[0078] Example 8 x=0.12, y=0.008 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 69.00g of CeBr3 raw material, 0.91g of CaBr2 raw material, and 3.12g of YbBr3 raw material, and then put them into a pre-cleaned quartz crucible.

[0079] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0080] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 35 hours to ensure that the raw materials are fully and evenly mixed.

[0081] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 830°C, and slowly move the heater at a speed of 5 mm / h to achieve crystal growth.

[0082] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0083] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0084] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 885℃ and the temperature of the lower zone was raised to 760℃. The temperature was maintained for 25 hours to completely melt the raw materials in the crucible. Then, crystal growth was carried out by drawing the crystal down at a rate of 0.1 mm / h. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 20℃ / h, and the crystal was taken out. The crystal was complete and transparent. The energy resolution at the crystal head was 2.44%@662keV, the energy resolution at the crystal tail was 2.51%@662keV, and the energy resolution inhomogeneity was 0.07%.

[0085] Example 9 x=0.05, y=0.006 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 26.56g of CeBr3 raw material, 1.25g of BaBr2 raw material, and 1.38g of YBr3 raw material, and then put them into a pre-cleaned quartz crucible.

[0086] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0087] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 24 hours to ensure that the raw materials are fully and evenly mixed.

[0088] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 820°C, and slowly move the heater at a speed of 6 mm / h to achieve crystal growth.

[0089] (5) Raw material processing: The grown crystals are placed in a glove box with water and oxygen content ≤0.1ppm, and the impurity layer on the surface and tail is removed to obtain raw material crystals. The raw material crystals with the impurity layer removed on the surface and tail are crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0090] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0091] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 900℃ and the temperature of the lower zone was raised to 770℃. The temperature was maintained for 25 hours to completely melt the raw materials in the crucible. Then, crystal growth was carried out by drawing the crystal down at a rate of 0.5 mm / h. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 25℃ / h, and the crystal was taken out. The crystal was complete and transparent. The energy resolution at the crystal head was 2.31%@662keV, the energy resolution at the crystal tail was 2.40%@662keV, and the energy resolution inhomogeneity was 0.09%.

[0092] Example 10 x=0.1, y=0.006 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 56.08g of CeBr3 raw material, 1.75g ​​of GbBr3 raw material, and 1.82g of YbBr3 raw material, and then put them into a pre-cleaned quartz crucible.

[0093] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0094] (3) Ball milling: Place the above-mentioned quartz crucible in a planetary ball mill and ball mill for 24 hours to ensure that the raw materials are fully and evenly mixed.

[0095] (4) Horizontal zone melting: Place the above crucible in a horizontal zone melting furnace, heat it to 830°C, and slowly move the heater at a speed of 4 mm / h to achieve crystal growth.

[0096] (5) Raw material processing: The crystals grown above are placed in a glove box with water and oxygen content ≤0.1ppm. The impurity layer on the surface and tail is removed to obtain the raw material crystal. The raw material crystal with the impurity layer removed on the surface and tail is crushed in a mortar and placed in a pre-cleaned quartz crucible.

[0097] (6) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, by using an oxyhydrogen flame to melt the opening of the quartz crucible, thereby achieving the purpose of isolating water and oxygen.

[0098] (7) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 900℃ and the temperature of the lower zone was raised to 780℃, and the temperature was held constant for 27 hours to completely melt the raw materials in the crucible. Then, crystal growth was carried out by drawing the crystal down at a rate of 0.1 mm / h. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 25℃ / h, and the crystal was taken out. The crystal was complete and transparent. The energy resolution at the crystal head was 2.34%@662keV, the energy resolution at the crystal tail was 2.43%@662keV, and the energy resolution inhomogeneity was 0.09%.

[0099] Comparative example: x=0.05, y=0.004 (1) Weighing of raw materials: In a glove box with water and oxygen content ≤0.1ppm, accurately weigh 500g of anhydrous LaBr3 raw material with a purity of 99.99%, 26.5g of CeBr3 raw material, and 1.65g of BaBr2 raw material, mix them evenly in a mortar, and then put them into a pre-cleaned quartz crucible.

[0100] (2) Crucible sealing: After removing it from the glove box, quickly evacuate to 10°C. -3 Pa, the opening of the quartz crucible is sealed with an oxyhydrogen flame to isolate it from water and oxygen.

[0101] (3) Crystal growth: The crucible was placed in the high-temperature zone of a two-stage temperature-controlled descent furnace. The temperature of the upper zone was raised to 870℃ and the temperature of the lower zone was raised to 750℃. The temperature was maintained for 12 hours to completely melt the raw materials in the crucible. Then, the crystal was drawn down at a rate of 0.5 mm / h for crystal growth. After the crystal growth was completed, the drawing was stopped. The temperature was lowered to room temperature at a rate of 15-50℃ / h, and the crystal was removed. The energy resolution at the crystal head was 2.94%@662keV, the energy resolution at the crystal tail was 4.06%@662keV, and the energy resolution inhomogeneity was 1.12%.

[0102] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, the above-described features have similar functions to (but are not limited to) those disclosed in this application.

Claims

1. A multi-doped lanthanum bromide scintillation crystal, characterized in that, The crystal is Ce x M y La (1-x-y) Br3, where M is one or a mixture of two of Mg, Ca, Sr, Ba, Y, Yb, Gd, 0 < x ≤ 0.2, 0 < y ≤ 0.01, and the non-uniformity of luminescence between the head and the tail of the crystal is not greater than 0.1%.

2. A method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 1, characterized in that, Includes the following steps: The initial raw material crystal is obtained by performing the first crystal growth using the horizontal zone melting method; the impurity layer on the surface and tail of the initial raw material crystal is removed to obtain the raw material crystal, and the raw material crystal is used as the growth material to perform the second crystal growth to obtain the multi-doped lanthanum bromide scintillation crystal.

3. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 2, characterized in that, The initial raw material crystal is obtained by first crystal growth using the horizontal zone melting method, which includes: placing the uniformly mixed raw material in a horizontal zone melting furnace, heating the raw material to completely melt it, moving the heater, and realizing crystal growth to obtain the initial raw material crystal.

4. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 3, characterized in that, The raw materials are thoroughly mixed evenly by ball milling in a planetary ball mill.

5. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 3, characterized in that, Inside the horizontal zone furnace, the raw material is completely melted at a temperature of 810-835℃, and the moving speed of the heater is 1-10 mm / h.

6. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to any one of claims 3-6, characterized in that, The removal of the impurity layer from the surface and tail of the initial raw material crystal is carried out in a glove box. The raw material crystal from which the impurity layer is removed is crushed in the glove box, placed in a crucible, vacuumed, and sealed to isolate water and oxygen.

7. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 6, characterized in that, The process of growing the multi-doped lanthanum bromide scintillation crystal by using the raw material crystal from which the impurity layer has been removed as the growth material includes: placing a crucible containing the growth material in a descending furnace, performing crystal growth by melting and drawing the material, and then annealing it at a lower temperature.

8. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 7, characterized in that, The crucible is placed in the high-temperature zone of a two-stage temperature-controlled descending furnace. The temperature of the upper and lower zones rises, causing the raw material in the crucible to melt completely. Then, it is drawn down for crystal growth. After the crystal growth is completed, the drawing down is stopped, and the temperature is lowered to room temperature to obtain the crystal.

9. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 8, characterized in that, The temperature in the upper heating zone rises to 840-900℃, and the temperature in the lower heating zone rises to 730-780℃, so that the raw materials in the crucible are completely melted.

10. The method for preparing a multi-doped lanthanum bromide scintillation crystal according to claim 9, characterized in that, Crystal growth is carried out by drawing the crucible down at a rate of 0.1-1.0 mm / h.