Fast attenuation rare earth halide scintillation crystal Ba2YCl7 as well as preparation method and application thereof

Abstract

The invention discloses a fast-attenuation rare earth halide scintillation crystal Ba2YCl7 as well as a preparation method and application thereof, and belongs to the technical field of scintillation crystal preparation. The preparation method provided by the invention comprises the following steps: purifying BaCl2 and YCl3, mixing the BaCl2 and the YCl3 according to a molar ratio of (1.2-1.9): 1, drying in a quartz crucible, and sealing; heating to a melting temperature, keeping the temperature constant for a first set time, cooling to below the melting temperature, and keeping the temperature constant for a second set time; performing crystal growth by using a Bridgman-Stockbarger method; and annealing to obtain the product. The preparation method and device are simple, the Ba2YCl7 crystal material with good crystallinity and light transmission can be obtained, and the Ba2YCl7 crystal material can be used as a fast attenuation scintillation crystal and / or a Ce < 3 + > activated fast attenuation scintillation crystal and even a main body material of an ultrafast scintillation crystal.

Description

Technical Field

[0001] The present invention relates to the technical field of scintillation crystal preparation, and in particular to a fast-decaying rare earth halide scintillation crystal Ba2YCl7 and a preparation method and application thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Scintillator crystal is a functional crystal material widely used in radiation detection and other fields. Rare earth halide scintillator crystal, especially Ce 3+ Activated scintillating crystals are most widely studied in the field of fast decay. However, most rare earth halides are extremely sensitive to moisture, which means that they must be tightly packaged to meet application requirements. Ba2YCl7 material is insensitive to moisture, and when it undergoes electronic transition, it does not require phonons to accept or provide momentum, which indicates its short carrier lifetime. At the same time, Y is an optically inert heavy rare earth element, which not only has a high ion valence state and Ce 3+ The same, and the radius is comparable, very suitable as Ce 3+ Therefore, Ba2YCl7 materials are expected to be bright fast decay scintillation crystals and / or as Ce 3+ Good candidates for activating fast decay scintillation crystal host materials.

[0004] Ba2YCl7 crystals were first used in near-infrared to visible light upconversion luminescence research due to their low phonon energy characteristics. In 1997, Riedener, T first proposed the use of the Czochralski method to grow Ba2YCl7:Er in an inert atmosphere. 3+ Crystals. However, since Ba2YCl7 is a non-uniform molten compound, not only does the crystal structure have low symmetry, but also the raw materials are very easy to come into contact with O2 or H2O at high temperature and in a molten state, forming chloride oxide YOCl and sesquioxide Y2O3, which makes the compound very difficult to grow. The related papers or patents reported have adopted the ammonium halide route for improvement. Although this method can provide a higher growth rate and control over nucleation, it has very strict requirements for the device to exclude O2 and H2O, and the purification process is relatively cumbersome. At present, there are few reports on the preparation of large-sized, well-crystalline, and high-optical transmittance block Ba2YCl7 crystals using a relatively simple production process. Summary of the invention

[0005] In view of this, the present invention provides a fast-decaying rare earth halide scintillation crystal Ba2YCl7 and a preparation method and application thereof. The present invention can ensure that the raw materials of Ba2YCl7 are in a state of being isolated from water and oxygen. At the same time, the operation is simple and it is easy to realize the programmed growth of large-size, good crystallinity and high optical transmittance block Ba2YCl7 crystals.

[0006] In a first aspect, the present invention provides a method for preparing a fast decay rare earth halide scintillation crystal Ba2YCl7, comprising the following steps:

[0007] S1, purify BaCl2 and YCl3 and mix them in a molar ratio of (1.2-1.9):1, place them in a quartz crucible, dry them and seal them;

[0008] S2, heating to the melting temperature, keeping the temperature constant for a first set time, then cooling to below the melting temperature, keeping the temperature constant for a second set time;

[0009] S3, using a crucible descent method to grow crystals, wherein the descent rate of the quartz crucible is 0.2-0.4 mm / h;

[0010] S4. Annealing.

[0011] Preferably, BaCl2 is purified by recrystallization and YCl3 is purified by zone melting.

[0012] Preferably, the quartz crucible is washed and dried before being used, and then heated in an inert atmosphere at 600 to 1000° C. for 5 to 24 hours.

[0013] Preferably, in step S2, the melting temperature is 800-900°C, the first setting time is 10-15h; the cooling to below the melting temperature is specifically cooling to 500-600°C; the second setting time is 3-5h.

[0014] Preferably, step S2 is repeated 2 to 4 times, and then the temperature is lowered to room temperature at a cooling rate of 10 to 20° C. / h to obtain a polycrystalline material.

[0015] Preferably, in step S3, the quartz crucible is placed 1 to 3 cm above the upper edge of the temperature gradient zone, the temperature is raised to 700 to 750°C, kept for 15 to 25 hours, and then gradually decreased in the temperature gradient zone of 10 to 30°C / cm until the melt is completely solidified and crystallized.

[0016] Preferably, the crucible descent method adopts a double-temperature zone crucible descent furnace.

[0017] Furthermore, the annealing step is: maintaining a constant temperature in the lower temperature zone of the dual-temperature zone crucible descending furnace, when the upper temperature zone is cooled to the temperature of the lower temperature zone, the upper temperature zone and the lower temperature zone are cooled to 200-300°C at the same cooling rate, and then heated to 500-600°C at the same heating rate, and kept at a constant temperature for 15-30h; then the upper temperature zone and the lower temperature zone are cooled to room temperature at the same cooling rate.

[0018] Furthermore, the heating rate and cooling rate of the upper temperature zone and the lower temperature zone are 3 to 8° C. / h.

[0019] In a second aspect, the present invention provides a fast decay rare earth halide scintillation crystal Ba2YCl7 prepared by the above preparation method.

[0020] In a third aspect, the present invention provides an application of the fast decaying rare earth halide scintillation crystal Ba2YCl7 in the field of fast decaying radiation detection.

[0021] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0022] (1) The present invention adopts the crucible descent method to prepare Ba2YCl7 crystal material. The growth method and growth device are simple. Through specific ratios and process conditions, Ba2YCl7 crystal material with good crystallinity and light transmittance can be obtained, which can be used for industrial batch mechanical production.

[0023] (2) The Ba2YCl7 crystal material prepared by the present invention is a monoclinic Ba2YCl7 crystal. The photoluminescence spectrum and decay spectrum at room temperature show that the Ba2YCl7 crystal has a double peak emission when excited at 329nm, and the average decay time of the fluorescence lifetime of the 352nm emission peak is less than 20ns when the double exponential fitting is performed, indicating that it can be used as a fast decay scintillation crystal and / or as a Ce 3+ The main material of activated fast-decaying scintillation crystals or even ultrafast scintillation crystals has broad application prospects in the field of fast-decaying radiation detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute an improper limitation of the present invention. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 The photos of Ba2YCl7 crystals grown in Example 1(a) and Example 2(b) of the present invention;

[0026] Figure 2XRD diagram of Ba2YCl7 crystals grown in Example 1 and Example 2 of the present invention;

[0027] Figure 3 This is an analytical structure diagram of the Ba2YCl7 crystal grown in Example 1 of the present invention;

[0028] Figure 4 The energy band structure diagram of Ba2YCl7 crystal calculated by the first principles of the present invention;

[0029] Figure 5 The photoluminescence spectrum of the Ba2YCl7 crystal grown in Example 1 of the present invention;

[0030] Figure 6 The photoluminescence attenuation spectrum of the Ba2YCl7 crystal grown in Example 1 of the present invention;

[0031] Figure 7 This is a photo of Ba2YCl7 crystal grown in Comparative Example 1 of the present invention;

[0032] Figure 8 This is a photo of Ba2YCl7 crystals grown in comparative example 3 of the present invention. DETAILED DESCRIPTION

[0033] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0034] The present invention provides a method for preparing a fast-decaying rare earth halide scintillation crystal Ba2YCl7, comprising the following steps:

[0035] S1, purify BaCl2 and YCl3 and mix them in a molar ratio of (1.2-1.9):1, place them in a quartz crucible, dry them and seal them;

[0036] S2, heating to the melting temperature, keeping the temperature constant for a first set time, then cooling to below the melting temperature, keeping the temperature constant for a second set time;

[0037] S3, using a crucible descent method to grow crystals, wherein the descent rate of the quartz crucible is 0.2-0.4 mm / h;

[0038] S4. Annealing.

[0039] In the raw materials of the present invention, the melting points of BaCl2 and YCl3 are 963°C and 721°C respectively, and there is a problem of non-uniform melting. Therefore, the molar ratio of BaCl2 and YCl3 is limited to (1.2-1.9):1 when preparing the ingredients of the present invention, so that YCl3 is excessive, which is conducive to obtaining Ba2YCl7 crystals with good crystallinity and light transmittance. If the amount of YCl3 added is too much, the crystal crystallinity and light transmittance will be reduced, and the hygroscopicity is strong, which is not conducive to practical application; if the amount of BaCl2 added is too much, the crystal crystallinity and light transmittance will also be poor, and the crystal will be severely wrapped and bubbles will exist.

[0040] The present invention adopts a crucible descent method to prepare a fast-decaying rare earth halide scintillating crystal Ba2YCl7 with high crystallinity and high transmittance. If the quartz crucible descends too slowly, not only will the growth cycle be greatly extended, but also the transmittance and crystallinity of the grown crystal will be deteriorated; if the quartz crucible descends too fast, the Ba2YCl7 crystal will be severely cracked and cannot be produced. Therefore, it is very necessary to select a suitable quartz crucible descending rate.

[0041] In the present invention, BaCl2 is purified by recrystallization, and YCl3 is purified by zone melting. The present invention finds that directly using commercially available raw materials will result in the phenomenon of impurity dispersion, so it is necessary to purify the raw materials BaCl2 and YCl3. The present invention does not make any special restrictions on the specific steps of recrystallization and zone melting, and can use the recrystallization and zone melting commonly used in the art.

[0042] In the present invention, the quartz crucible is washed and dried before being put into use, and then heated in an inert atmosphere at 600-1000°C for 5-24h. The cleanliness of the quartz crucible will also affect the crystal growth process, and the impurities and hydroxyl groups in the quartz crucible are removed by the above treatment. The present invention does not impose any special restrictions on the specific washing and drying process, and the washing and drying methods commonly used in the art can be used.

[0043] The present invention does not impose any special restrictions on the drying and sealing processes in step S1, and the drying and sealing processes commonly used in the art may be adopted.

[0044] In the present invention, in step S2, the melting temperature is 800-900°C, the first setting time is 10-15h; the cooling to below the melting temperature is specifically cooling to 500-600°C; the second setting time is 3-5h. Step S2 is repeated 2-4 times, and then cooled to room temperature at a cooling rate of 10-20°C / h to obtain a polycrystalline material. This step is to facilitate the discharge of bubbles and impurities in the melt.

[0045] In the present invention, in step S3, the quartz crucible is placed 1 to 3 cm above the upper edge of the temperature gradient zone, the temperature is raised to 700 to 750°C, and the temperature is kept for 15 to 25 hours, more preferably 18 to 22 hours; then the temperature is gradually lowered in the temperature gradient zone of 10 to 30°C / cm, and as the seed crystal zone spontaneously eliminates nuclei, the crystals grow upward from the bottom of the crucible until the melt is completely solidified and crystallized.

[0046] In the present invention, the crucible descent method adopts a dual-temperature zone crucible descent furnace. The annealing treatment is to release residual stress and reduce deformation and crack tendency. The annealing steps of the present invention are: keep the lower temperature zone of the dual-temperature zone crucible descent furnace at a constant temperature, and when the upper temperature zone is cooled to the temperature of the lower temperature zone, the upper temperature zone and the lower temperature zone are cooled to 200-300°C at the same cooling rate. If the upper and lower temperature zones are cooled at the same time, the axial stress of the crystal is large and cracking is likely to occur. Then the upper and lower temperature zones are heated to 500-600°C at the same heating rate and kept at a constant temperature for 15-30h; then the upper temperature zone and the lower temperature zone are cooled to room temperature at the same cooling rate. In the present invention, the heating rate and cooling rate of the upper temperature zone and the lower temperature zone are 3-8°C / h.

[0047] The present invention also provides a fast decaying rare earth halide scintillating crystal Ba2YCl7 prepared by the above preparation method. The Ba2YCl7 crystal prepared by the present invention is a monoclinic crystal system, and the photoluminescence spectrum and attenuation spectrum at room temperature show that it has a double peak emission when excited at 329nn, and the average decay time of the fluorescence lifetime of the 352nm emission peak is less than 20ns when the double exponential fitting is performed.

[0048] The present invention also provides the application of the fast decay rare earth halide scintillation crystal Ba2YCl7 in the field of fast decay radiation detection.

[0049] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0050] Example 1

[0051] This embodiment provides a method for preparing a fast decay rare earth halide scintillation crystal Ba2YCl7.

[0052] (1) Raw material purification:

[0053] Purification of BaCl2: First, wash and filter it three times with anhydrous ethanol, then dissolve it with deionized water, and cool the filtrate to crystallize at 30°C. After all the filtrate is crystallized, grind the crystal block roughly and dry it in an argon atmosphere furnace at 150°C for 20 hours to obtain high-purity BaCl2, which is sealed for later use.

[0054] Purification of YCl3: Multiple zone melting is carried out in the crucible descending furnace, and the impurities are fixed to the tail. After removing the impurities, high-purity YCl3 is obtained and sealed for use.

[0055] (2) Quartz crucible treatment:

[0056] According to the growth characteristics of the crystal, a quartz crucible with a capillary structure is designed and customized, and it is pre-treated for decontamination before leaving the factory. After washing the quartz crucible several times with a large amount of clean water, deionized water is injected into the quartz crucible and placed in an ultrasonic cleaner for half an hour of ultrasonic cleaning, and then the deionized water is poured out. After repeating the above process twice, anhydrous ethanol is injected into the quartz crucible and sealed for ultrasonic cleaning for 1 hour. After pouring out the ethanol, the crucible is placed in a drying oven and dried at 60°C for 24 hours to ensure that there is no liquid residue inside the crucible. The dried quartz crucible is sealed in a special container and dried at 800°C in an inert atmosphere furnace for 10 hours to remove the hydroxyl groups in the crucible. The treated crucible is packaged in a ziplock bag and transferred to a glove box without sealing for 3 days before being put into use.

[0057] (3) Raw material loading:

[0058] The molar ratio of BaCl2 to YCl3 in the designed raw material is 1.5:1. In a glove box filled with inert gas, the pre-purified BaCl2 and YCl3 are weighed according to the designed ratio, mixed evenly, and loaded into the quartz crucible treated in step (2) using a special paper funnel (to reduce the electrostatic adsorption of the powder raw material), sealed with a valve, and dried at 160°C in vacuum for 5 hours to remove the moisture adsorbed by the raw material and the quartz crucible.

[0059] (4) Quartz crucible sealing:

[0060] Use a vacuum ionization device to evacuate the quartz crucible in step (3) to a vacuum of about 10 -6 mbar, sealed with an oxyhydrogen torch, the crucible was in a continuous ionized vacuum state during the sealing process, and rotated at 20r / min. After sealing, the vacuum tester was used to test its sealing.

[0061] (5) Polycrystalline material synthesis and aging:

[0062] The sealed quartz crucible of step (4) is placed in a melting furnace at 850°C for 15 hours to fully melt the raw materials, then the temperature is reduced to 550°C and maintained for 3.5 hours. This operation is repeated three times. After the aging of the polycrystalline material is completed, the temperature is reduced to room temperature at a rate of 15°C / h to obtain Ba2YCl7 polycrystalline material.

[0063] (6) Crucible descent method crystal growth:

[0064] Check the synthesis of the quartz crucible and polycrystalline material in step (5). For polycrystalline materials that meet the growth conditions, grow them by the crucible descent method, using a double-temperature zone crucible descent furnace. Place the quartz crucible 2 cm above the temperature gradient zone, heat it to 750 ° C at a rate of 100 ° C / h and keep it warm for 20 hours to ensure that the polycrystalline material is completely melted and mixed evenly, then let the crucible descend at a rate of 0.3 mm / h through a 26 ° C / cm temperature gradient zone. As the seed crystal zone spontaneously eliminates nuclei, the crystal grows upward from the bottom of the crucible until the melt is completely solidified and crystallized.

[0065] (7) Annealing and cooling:

[0066] The upper temperature zone is cooled at a rate of 5°C / h, while the lower temperature zone is kept at a constant temperature for annealing. When the temperatures of the upper and lower temperature zones are equal, the two temperature zones are cooled at a rate of 5°C / h simultaneously, down to 200°C, and then heated to 550°C at a rate of 5°C / h, and maintained for 20 hours. Then, they are cooled to room temperature at a rate of 5°C / h to obtain Ba2YCl7 crystals.

[0067] The Ba2YCl7 crystals obtained in this embodiment are as follows Figure 1 As shown in a in .

[0068] A uniform block was taken out from the above crystal and ground, and then powder XRD test was performed. The test results are shown in Figure 2 As can be seen from the figure, the obtained crystal is indeed Ba2YCl7 crystal.

[0069] A good quality grain was selected from the above crystals for single crystal structure analysis test. The test results are shown in Figure 3 As can be seen from the figure, the obtained crystal is indeed a monoclinic Ba2YCl7 crystal.

[0070] Based on the above test results, the first principle calculation of the crystal band structure is carried out. The calculation results are shown in Figure 4 As can be seen from the figure, the calculated band gap of Ba2YCl7 crystal is 6.18eV, which is consistent with the Ce 3+ Bandgap requirements for good host materials to activate scintillation crystals.

[0071] A 1.5 mm thin slice was taken from the above crystal and the photoluminescence spectrum and attenuation spectrum were tested using a fluorescence spectrometer. The test results are shown in Figure 5 and Figure 6 As can be seen from the figure, the photoluminescence spectrum and photoluminescence decay spectrum at room temperature show that Ba2YCl7 crystal has double peak emission when excited by 329nn, and the average decay time of the fluorescence lifetime of the 352nm emission peak is less than 20ns when fitted with a double exponential.

[0072] Example 2

[0073] This embodiment provides a method for preparing a fast decay rare earth halide scintillation crystal Ba2YCl7.

[0074] (1) Raw material purification:

[0075] Purification of BaCl2: First, wash and filter it three times with anhydrous ethanol, then dissolve it with deionized water, and cool the filtrate to crystallize at 30°C. After all the filtrate is crystallized, grind the crystal block roughly and dry it in an argon atmosphere furnace at 150°C for 20 hours to obtain high-purity BaCl2, which is sealed for later use.

[0076] Purification of YCl3: Multiple zone melting is carried out in the crucible descending furnace, and the impurities are fixed to the tail. After removing the impurities, high-purity YCl3 is obtained and sealed for use.

[0077] (2) Quartz crucible treatment:

[0078] According to the growth characteristics of the crystal, a quartz crucible with a capillary structure is designed and customized, and it is pre-treated for decontamination before leaving the factory. After washing the quartz crucible several times with a large amount of clean water, deionized water is injected into the quartz crucible and placed in an ultrasonic cleaner for half an hour of ultrasonic cleaning, and then the deionized water is poured out. After repeating the above process twice, anhydrous ethanol is injected into the quartz crucible and sealed for ultrasonic cleaning for 1 hour. After pouring out the ethanol, the crucible is placed in a drying oven and dried at 60°C for 24 hours to ensure that there is no liquid residue inside the crucible. The dried quartz crucible is sealed in a special container and dried at 800°C in an inert atmosphere furnace for 10 hours to remove the hydroxyl groups in the crucible. The treated crucible is packaged in a ziplock bag and transferred to a glove box without sealing for 3 days before being put into use.

[0079] (3) Raw material loading:

[0080] The molar ratio of BaCl2 to YCl3 in the designed raw material is 1.85:1. In a glove box filled with inert gas, the pre-purified BaCl2 and YCl3 are weighed according to the designed ratio, mixed evenly, and loaded into the quartz crucible treated in step (2) using a special paper funnel (to reduce the electrostatic adsorption of the powder raw material), sealed with a valve, and dried at 160°C in vacuum for 5 hours to remove the moisture adsorbed by the raw material and the quartz crucible.

[0081] (4) Quartz crucible sealing:

[0082] Use a vacuum ionization device to evacuate the quartz crucible in step (3) to a vacuum of about 10 -6 mbar, sealed with an oxyhydrogen torch, the crucible was in a continuous ionized vacuum state during the sealing process, and rotated at 20r / min. After sealing, the vacuum tester was used to test its sealing.

[0083] (5) Polycrystalline material synthesis and aging:

[0084] The sealed quartz crucible of step (4) is placed in a melting furnace at 900°C for 13 hours to fully melt the raw materials, then the temperature is reduced to 600°C and maintained for 3 hours; this operation is repeated 3 times. After the aging of the polycrystalline material is completed, the temperature is reduced to room temperature at a rate of 15°C / h to obtain Ba2YCl7 polycrystalline material.

[0085] (6) Crucible descent method crystal growth:

[0086] Check the synthesis of the quartz crucible and polycrystalline material in step (5). For polycrystalline materials that meet the growth conditions, grow them by the crucible descent method, using a double-temperature zone crucible descent furnace. Place the quartz crucible 3 cm above the temperature gradient zone, heat it to 750 ° C at a rate of 100 ° C / h and keep it warm for 20 h to ensure that the polycrystalline material is completely melted and mixed evenly. Then, let the crucible pass through the 20 ° C / cm temperature gradient zone at a descending speed of 0.4 mm / h. As the seed crystal zone spontaneously eliminates nuclei, the crystal grows upward from the bottom of the crucible until the melt is completely solidified and crystallized.

[0087] (7) Annealing and cooling:

[0088] The upper temperature zone is cooled at a rate of 5°C / h, while the lower temperature zone is kept at a constant temperature for annealing. When the temperatures of the upper and lower temperature zones are equal, the two temperature zones are cooled at a rate of 5°C / h simultaneously, down to 300°C, and then heated to 600°C at a rate of 5°C / h, and maintained for 20 hours. Then, the temperatures are cooled down to room temperature at a rate of 5°C / h to obtain Ba2YCl7 crystals.

[0089] The Ba2YCl7 crystals obtained in this embodiment are as follows Figure 1 As shown in b.

[0090] A uniform block was taken out from the above crystal and ground, and powder XRD test was performed. The test results are shown in Figure 2 As can be seen from the figure, the obtained crystal is indeed Ba2YCl7 crystal.

[0091] Example 3

[0092] This embodiment provides a method for preparing a fast decay rare earth halide scintillation crystal Ba2YCl7.

[0093] (1) Raw material purification:

[0094] Purification of BaCl2: First, wash and filter it three times with anhydrous ethanol, then dissolve it with deionized water, and cool the filtrate to crystallize at 30°C. After all the filtrate is crystallized, grind the crystal block roughly and dry it in an argon atmosphere furnace at 150°C for 20 hours to obtain high-purity BaCl2, which is sealed for later use.

[0095] Purification of YCl3: Multiple zone melting is carried out in the crucible descending furnace, and the impurities are fixed to the tail. After removing the impurities, high-purity YCl3 is obtained and sealed for use.

[0096] (2) Quartz crucible treatment:

[0097] According to the growth characteristics of the crystal, a quartz crucible with a capillary structure is designed and customized, and it is pre-treated for decontamination before leaving the factory. After washing the quartz crucible several times with a large amount of clean water, deionized water is injected into the quartz crucible and placed in an ultrasonic cleaner for half an hour of ultrasonic cleaning, and then the deionized water is poured out. After repeating the above process twice, anhydrous ethanol is injected into the quartz crucible and sealed for ultrasonic cleaning for 1 hour. After pouring out the ethanol, the crucible is placed in a drying oven and dried at 60°C for 24 hours to ensure that there is no liquid residue inside the crucible. The dried quartz crucible is sealed in a special container and dried at 800°C in an inert atmosphere furnace for 10 hours to remove the hydroxyl groups in the crucible. The treated crucible is packaged in a ziplock bag and transferred to a glove box without sealing for 3 days before being put into use.

[0098] (3) Raw material loading:

[0099] The molar ratio of BaCl2 to YCl3 in the designed raw material is 1.22:1. In a glove box filled with inert gas, the pre-purified BaCl2 and YCl3 are weighed according to the designed ratio, mixed evenly, and loaded into the quartz crucible treated in step (2) using a special paper funnel (to reduce the electrostatic adsorption of the powder raw material), sealed with a valve, and dried at 160°C in vacuum for 5 hours to remove the moisture adsorbed by the raw material and the quartz crucible.

[0100] (4) Quartz crucible sealing:

[0101] Use a vacuum ionization device to evacuate the quartz crucible in step (3) to a vacuum of about 10 -6 mbar, sealed with an oxyhydrogen torch, the crucible was in a continuous ionized vacuum state during the sealing process, and rotated at 20r / min. After sealing, the vacuum tester was used to test its sealing.

[0102] (5) Polycrystalline material synthesis and aging:

[0103] The sealed quartz crucible of step (4) is placed in a melting furnace at 800°C for 10 hours to fully melt the raw materials, then the temperature is reduced to 500°C and maintained for 4.5 hours; this operation is repeated 3 times. After the aging of the polycrystalline material is completed, the temperature is reduced to room temperature at a rate of 15°C / h to obtain Ba2YCl7 polycrystalline material.

[0104] (6) Crucible descent method crystal growth:

[0105] Check the synthesis of the quartz crucible and polycrystalline material in step (5). For polycrystalline materials that meet the growth conditions, grow them by the crucible descent method, using a double-temperature zone crucible descent furnace. Place the quartz crucible 1 cm above the temperature gradient zone, heat it to 750°C at a rate of 100°C / h and keep it warm for 20 hours to ensure that the polycrystalline material is completely melted and mixed evenly. Then, let the crucible descend at a rate of 0.2 mm / h through a 30°C / cm temperature gradient zone. As the seed crystal zone spontaneously eliminates nuclei, the crystal grows upward from the bottom of the crucible until the melt is completely solidified and crystallized.

[0106] (7) Annealing and cooling:

[0107] The upper temperature zone is cooled at a rate of 5°C / h, while the lower temperature zone is kept at a constant temperature for annealing. When the temperatures of the upper and lower temperature zones are equal, the two temperature zones are cooled at a rate of 5°C / h simultaneously, down to 200°C, and then heated to 550°C at a rate of 5°C / h, and maintained for 20 hours. Then, they are cooled to room temperature at a rate of 5°C / h to obtain Ba2YCl7 crystals.

[0108] Comparative Example 1

[0109] The difference between this comparative example and Example 1 is that in step (3), the molar ratio of BaCl2 to YCl3 in the raw materials is designed to be 2.3:1.

[0110] Figure 7 The crystals grown in this comparative example have worse crystallinity and light transmittance than the crystals grown in Example 1, and the crystals are severely encapsulated and have bubbles inside.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 1 is that in step (3), the molar ratio of BaCl2 to YCl3 in the raw materials is designed to be 1:1.

[0113] The crystals obtained in Comparative Example 2 have poor crystallinity and reduced light transmittance compared to the crystals grown in Example 1. Due to the excessive amount of YCl3, the crystals are highly hygroscopic after being taken out.

[0114] Comparative Example 3

[0115] The difference between this comparative example and Example 1 is that in step (6), the crucible is passed through a temperature gradient zone of 26° C. / cm at a descending speed of 0.1 mm / h.

[0116] Figure 8 The crystal grown in comparative example 3 has lower crystallinity and lower light transmittance than the crystal grown in example 1. The growth process is time-consuming and does not meet the conditions for later commercial production.

[0117] Comparative Example 4

[0118] The difference between this comparative example and Example 1 is that in step (6), the crucible is passed through a temperature gradient zone of 26° C. / cm at a descending speed of 0.5 mm / h.

[0119] The crystals obtained in Comparative Example 4 had lower crystallinity and severe cracking than the crystals grown in Example 1 and could not be produced into finished products.

[0120] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a fast decay rare earth halide scintillation crystal Ba2YCl7, characterized in that: The steps include: S1, purify BaCl2 and YCl3 and mix them in a molar ratio of (1.2-1.9):1, place them in a quartz crucible, dry them and seal them; S2, heating to the melting temperature, keeping the temperature constant for a first set time, then cooling to below the melting temperature, keeping the temperature constant for a second set time; S3, using a crucible descent method to grow crystals, wherein the descent rate of the quartz crucible is 0.2-0.4 mm / h; S4. Annealing.

2. The preparation method according to claim 1, characterized in that BaCl2 is purified by recrystallization and YCl3 is purified by zone melting.

3. The preparation method according to claim 1, characterized in that: The quartz crucible is washed and dried before being used, and then heated in an inert atmosphere at 600-1000° C. for 5-24 hours.

4. The preparation method according to claim 1, characterized in that: In step S2, the melting temperature is 800-900°C, the first setting time is 10-15h; the cooling to below the melting temperature is specifically cooling to 500-600°C; the second setting time is 3-5h.

5. The preparation method according to claim 1, characterized in that: Step S2 is repeated 2 to 4 times, and then the temperature is lowered to room temperature at a cooling rate of 10 to 20° C. / h to obtain a polycrystalline material.

6. The preparation method according to claim 1, characterized in that: In step S3, the quartz crucible is placed 1 to 3 cm above the upper edge of the temperature gradient zone, the temperature is raised to 700 to 750°C, kept for 15 to 25 hours, and then gradually decreased in the temperature gradient zone of 10 to 30°C / cm until the melt is completely solidified and crystallized.

7. The preparation method according to claim 1, characterized in that: The crucible descent method adopts a double-temperature zone crucible descent furnace; the annealing step is: keep the lower temperature zone of the double-temperature zone crucible descent furnace at a constant temperature, when the upper temperature zone is cooled to the temperature of the lower temperature zone, the upper temperature zone and the lower temperature zone are cooled to 200-300°C at the same cooling rate, and then heated to 500-600°C at the same heating rate, and kept at a constant temperature for 15-30h; then the upper temperature zone and the lower temperature zone are cooled to room temperature at the same cooling rate.

8. The preparation method according to claim 7, characterized in that: The heating rate and cooling rate of the upper temperature zone and the lower temperature zone are 3-8°C / h.

9. The fast decay rare earth halide scintillation crystal Ba2YCl7 prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the fast decaying rare earth halide scintillation crystal Ba2YCl7 as claimed in claim 9 in the field of fast decaying radiation detection.

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