Method for growing cerium lanthanum bromide scintillation crystal by using horizontal Bridgman method

Abstract

The invention discloses a method for growing a lanthanum cerium bromide scintillation crystal by using a horizontal Bridgman method, which comprises the following steps of: mixing growth raw materials LaBr3 and CeBr3 in a horizontal boat in an inert atmosphere, and putting seed crystals into a seed crystal bag of the horizontal boat; putting the horizontal boat into a quartz crucible, vacuumizing, filling reaction mixed gas, and sealing the quartz crucible; the temperature gradient in the horizontal Bridgman furnace is set to be 5-20 DEG C per centimeter, and the sealed quartz crucible is placed in the horizontal Bridgman furnace for crystal growth to obtain lanthanum cerium bromide crystals; according to the invention, a free space is formed above a melt grown by adopting a horizontal Bridgman method, so that the constraint and extrusion of a crucible on a crystal are relieved; and through a small temperature gradient, the internal thermal stress of the crystal is further reduced, and the problems that the LaBr3: Ce crystal is extremely easy to crack, a complete crystal ingot is difficult to obtain and the success rate is low when the LaBr3: Ce crystal is grown by a vertical Bridgman method are solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic scintillator materials, and particularly relates to a method for growing cerium-doped lanthanum bromide scintillation crystals by the horizontal Bridgman method. Background Art

[0002] At present, scintillation crystals are used to detect by converting ionizing radiation such as X / γ rays, high-energy charged particles (such as electrons, positrons, protons, and alpha particles) into light signals. Scintillation crystals are usually coupled with photomultiplier tubes or SiPMs. The light pulse signals formed by their excitation by ionizing radiation will be output through photomultiplier tubes or SiPMs and amplified into proportional electrical pulse signals by associated electronic circuits, thereby realizing radiation detection. Thus, scintillation crystals are widely used in fields such as nuclear medicine, high-energy physics, astrophysics, security systems, geophysics, environmental control, and industrial applications.

[0003] In all scientific and technological fields based on the use of scintillation crystals, obtaining materials with appropriate properties is a primary task. Cerium-doped lanthanum bromide scintillation crystals (LaBr 3 :Ce) have received extensive attention since their discovery by Van Loef EVD in 2001 and have the most prominent performance among scintillation crystals. Cerium-doped lanthanum bromide scintillation crystals have excellent properties such as high density (5.0 g / cm 3 ), high light yield (~65000 photons / MeV), fast decay time (~30 ns), high energy resolution (~3% @ 662 keV), good energy proportionality, and strong high-temperature stability. The performance of cerium-doped lanthanum bromide scintillation crystals is comprehensively superior to that of NaI:Tl scintillation crystals and has great potential to replace NaI:Tl crystals. The discovery of cerium-doped lanthanum bromide scintillation crystals has opened a new era in the research of scintillators and the development of nuclear radiation detectors and has great application prospects in nuclear radiation detection fields such as nuclear medicine, well logging, nuclear safety detection, space research, and high-energy physics.

[0004] The technical choice for producing scintillation crystals determines their quality, cost, and market prospects. Improving the efficiency of the crystal growth process is the main goal of researchers. Currently, the main components affecting the process efficiency and crystal growth cost are crystal growth technology, growth equipment, and raw material costs. The combination and optimization of these components can maximize the process efficiency. However, there are many difficulties in the growth and preparation of cerium lanthanum bromide scintillation crystals, making it difficult to achieve widespread application. Among them, cerium lanthanum bromide scintillation crystals have significant orientation dependence in thermal and mechanical properties, being brittle mechanically and prone to cleavage and cracking. In addition, lanthanum bromide is very sensitive to moisture and oxygen, reacting to form rare earth oxyhalides, which leads to adhesion between the crystal and the ampoule wall during the growth process. The currently commonly used growth method is the vertical Bridgman method. It is reported in the literature "H. Shi, L. Qin, W. Chai, J. Guo, Q. Wei, G. Ren, K. Shu, The LaBr 3 :Ce Crystal Growth by Self-Seeding Bridgman Technique and Its Scintillation Properties, Crystal Growth & Design, 10(2010)4433 - 4436." that the LaBr 3 :Ce crystal was grown by the self-seeding vertical Bridgman method. The temperature gradient used during the vertical Bridgman method growth was 30 °C / cm, and the grown LaBr 3 :Ce crystals were extremely prone to cleavage and cracking, with a low success rate. Moreover, there is an important relationship between the crystallization direction and growth rate in the self-seeding process of LaBr 3 :Ce crystals: when the lowering speed is 0.5 mm / h, the crystal orientation is always

[100] , and the ingot is prone to cracking; when the lowering speed is 1 mm / h, the crystal orientation remains unchanged, staying at

[001] , and only a few ingots crack. The stress during the vertical Bridgman method growth mainly comes from the adhesion force between the LaBr 3 :Ce ingot and the quartz crucible wall during the cooling process. Only when the crystal grows along the

[001] direction, making the formed stress have the highest symmetry, can the formation of cracks in the crystal be better avoided. Therefore, it is necessary to strictly control the crystallization orientation through the self-seeding process, make the

[001] orientation dominant through a lowering rate of 1 mm / h, and in order to obtain a single crystal, the diameter of the capillary tip of the crucible needs to maintain a slender shape. Finally, the inner diameter of the capillary tip used is 3 mm and the length is 30 mm. Therefore, the finally obtained LaBr 3 :Ce single crystal has a limited size, only 10×10×10 mm 3 .

[0005] In the literature "W.M. Higgins, A. Churilov, E. van Loef, J. Glodo, M. Squillante, K. Shah, Crystal growth of large diameter LaBr 3 :Ce and CeBr 3 , J Cryst Growth, 310(2008)2085 - 2089.", it is reported that customized equipment is used for the treatment of water - oxygen - sensitive materials and crystal growth, and finally large - sized LaBr 3 :Ce and pure CeBr 3 crystal growth is carried out in a vertical multi - zone Bridgman furnace. The furnace body for growth uses airtight top and bottom insulation plugs to prevent chimney effect and uncontrolled air flow to reduce the thermal shock to the crystal. The raw materials before growth are configured and loaded into the crucible in a nitrogen glove box that reduces the water - oxygen concentration (below 10 ppm) through copper catalysts and dry molecular sieves. Finally, by suppressing the formation of oxyhalides, the residual stress in the grown crystal is reduced and crack formation is inhibited. Finally, by suppressing the random crystal orientation of spontaneous nucleation with the c - axis seed crystal (

[001] ) leading to crystal cracking, and combining annealing and slow cooling, a 2 - inch crack - free LaBr 3 :Ce crystal with a light yield of 80000 photons / MeV is finally obtained. However, due to the severe anisotropy of thermal expansion (thermal expansion of a - and c - axes) of the LaBr 3 :Ce crystal and the water - oxygen - sensitive characteristics of the material, the technological process needs to be strictly controlled. The growth by the vertical Bridgman method is restricted by the crucible, and due to the characteristic that the LaBr 3 :Ce crystal is extremely easy to cleave along the cleavage parallel to the c - axis, there are problems of serious crystal fragmentation and low success rate. Summary of the Invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a method for growing cerium - doped lanthanum bromide scintillation crystals using the horizontal Bridgman method. In the horizontal Bridgman method, there is free space above the melt, which alleviates the constraint and extrusion of the crucible on the crystal; and through a small temperature gradient, the internal thermal stress of the crystal is further reduced, solving the problem that when growing LaBr 3 :Ce crystals by the vertical Bridgman method, it is extremely easy to crack and it is difficult to obtain a complete ingot with a low success rate.

[0007] To achieve the above object, the present invention provides the following technical solution: A method for growing cerium - doped lanthanum bromide scintillation crystals using the horizontal Bridgman method, comprising the following steps:

[0008] S1 Under an inert atmosphere, the growth raw material LaBr 3, CeBr 3 Mix them and place them in a horizontal boat, and put seeds in the seed pocket of the horizontal boat;

[0009] S2 Load the above-mentioned horizontal boat into a quartz crucible, evacuate, fill with a reaction mixture gas, and seal the quartz crucible;

[0010] S3 Set the temperature gradient in the horizontal Bridgman furnace to 5°C to 20°C per centimeter, place the sealed quartz crucible in the horizontal Bridgman furnace, and the center of the seed in the horizontal boat is located at the melting point temperature of LaBr 3 At the melting point temperature, the side of the seed away from the growth raw material is cooled gradientually, and the side of the seed close to the growth raw material is heated gradientually to a high-temperature constant-temperature field, and the temperature of the high-temperature constant-temperature field is above the melting point of the growth raw material;

[0011] S4 After all the growth raw materials are melted in the high-temperature constant-temperature field, move the horizontal boat in the direction where the seed has not melted to grow crystals to obtain a cerium lanthanum bromide crystal precursor;

[0012] S5 Cool down, anneal, keep warm, and cool down the cerium lanthanum bromide crystal precursor to obtain a cerium lanthanum bromide crystal.

[0013] Furthermore, in S1, the proportion of CeBr 3 in the growth raw material is 0.1 at% to 10 at%, and the filling height range of the growth raw material is 1 / 2 to 2 / 3 of the height of the horizontal boat.

[0014] Furthermore, in S1, the seed is a c-direction seed.

[0015] Furthermore, in S1, the growth raw materials LaBr 3 , CeBr 3 are also doped with a co-dopant, the doping amount of the co-dopant is 0 ppmW to 3000 ppmW, and the co-dopant is a bromide combination of one or several elements selected from Ga, In, Bi, Mg, Ca, Sr, Ba, Zn, Cd, Zr, Hf.

[0016] Furthermore, in S2, the reaction mixture gas is high-purity argon and a reaction gas, and the proportion of the reaction gas in the reaction mixture gas is 5% to 30%; the reaction gas is a halogen group or silane group compound reactive gas.

[0017] Furthermore, in S3, the melting range of the seed is 0.1 cm to 0.3 cm, the temperature of the high-temperature constant-temperature field is 10°C to 60°C above the melting point of LaBr 3 , and keep the horizontal boat in the above temperature gradient field for 6 h to 36 h.

[0018] Furthermore, in S4, the moving speed of the horizontal boat is 0.1 mm to 5 mm per hour until the temperature at the tail of the horizontal boat is lower than LaBr3 The melting point.

[0019] Further, in S5, the lanthanum cerium bromide crystal precursor is cooled to 450 °C - 650 °C at a rate of 5 - 50 °C per hour, held for 12 h - 48 h, and then cooled to room temperature at a rate of 5 °C - 50 °C per hour.

[0020] The present invention also provides a lanthanum cerium bromide scintillation crystal prepared by the above method.

[0021] The present invention also provides an application of the lanthanum cerium bromide scintillation crystal. The lanthanum cerium bromide scintillation crystal prepared by the above lanthanum cerium bromide scintillation crystal or the above preparation method is cut and processed, polished in an inert atmosphere, and encapsulated into a detector of a certain specification.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The present invention proposes a method for growing lanthanum cerium bromide scintillation crystals using the horizontal Bridgman method. Using the horizontal Bridgman method can keep the upper part of the melt as a free space, relieve the constraint and extrusion of the crucible on the crystal, and effectively avoid the problem that the crystals grown by the vertical Bridgman method are easily fragmented; by the reaction mixed gas, a low water-oxygen environment is further maintained to inhibit the formation of oxohalides and avoid the adhesion of the LaBr 3 :Ce ingot to the wall of the horizontal boat, and at the same time effectively inhibit the volatilization and decomposition of the melt, and the components of the prepared crystal are closer to the ideal stoichiometric ratio; further, using the seed crystal and small temperature gradient growth improves the yield of the LaBr 3 :Ce ingot, makes the crystal grow along the

[001] direction, minimizes the expansion along the crystal length direction, and further reduces the internal thermal stress of the crystal to inhibit crystal cracking. In summary, the present invention solves the problem that the lanthanum cerium bromide scintillation crystals grown by the vertical Bridgman method are extremely easy to crack and it is difficult to obtain a complete ingot, realizes the improvement of the ingot yield and utilization rate, and is especially suitable for processing into special-shaped lanthanum cerium bromide scintillation crystals such as squares. Description of the Drawings

[0024] Figure 1 It is a schematic diagram of the horizontal boat described in the present invention, (a) front view, (b) top view.

[0025] Figure 2 It is a schematic diagram of the crystal growth device of the embodiment of the present invention.

[0026] The reference numerals are as follows: 1 - alumina insulation board, 2 - heating wire, 3 - zirconia partition, 4 - quartz furnace chamber, 5 - nano-aerogel insulation blanket, 6 - growth raw material, 7 - horizontal boat, 8 - quartz crucible, 9 - quartz plug, 10 - quartz support.

[0027] Figure 3The crystal energy spectrum diagram obtained in Example 1. Detailed implementation manners

[0028] The present invention will be further described below in conjunction with the accompanying drawings and detailed implementation manners.

[0029] The present invention provides a method for growing cerium lanthanum bromide scintillation crystals using the horizontal Bridgman method, comprising the following steps:

[0030] Step 1: Under an inert atmosphere, load the growth raw materials LaBr 3 , CeBr 3 into a clean and dry horizontal boat in a certain proportion, and a certain proportion of co-dopants may be incorporated into the growth raw materials. The mass of the loaded growth raw materials is related to the specifications of the horizontal boat of the furnace body, and the loading mass should satisfy that the height after melting of the growth raw materials is lower than the height of the horizontal boat. Preferably, the height range is 1 / 2 - 2 / 3 of the height of the horizontal boat. As Figure 1 shown in [reference], a seed crystal pocket is provided at one end of the horizontal boat, and a c-axis seed crystal is loaded for crystal seeding to ensure the crystal growth direction.

[0031] Among them, the proportion of CeBr 3 in the growth raw materials ranges from 0.1 to 10 at%, and the co-dopant may be a combination of bromides of one or several elements in the group of Ga, In, Bi, Mg, Ca, Sr, Ba, Zn, Cd, Zr, Hf, and the doping amount may be 0 - 3000 ppmW.

[0032] Step 2: Under an inert atmosphere, load the horizontal boat loaded with the growth raw materials into a quartz crucible, transfer it out of the inert gas glove box under air isolation conditions, and connect it to a vacuum sealing unit. First, evacuate the quartz crucible to a vacuum, and when the vacuum degree reaches the required pressure, then fill it with a mixture of high-purity (6N and above) Ar gas and a reaction gas at a certain pressure; then use a hydrogen-oxygen flame to seal the quartz crucible.

[0033] Among them, the reaction gas can be a halogen group or silane group compound reactive gas, such as CBr 4 , CCl 4 , SiCl 4 , etc., or it can also be H 2 . Taking the reaction process of the reaction gas CBr 4 as an example: 2H 2 O + CBr 4 → CO 2 + 4HBr, and its reaction product CO 2 is an inert substance.

[0034] Preferably, the proportion of the reaction gas in the mixture ranges from 5% to 30%, and more preferably the proportion range is 10% to 20%.

[0035] Step 3: Place the sealed quartz crucible in a horizontal Bridgman furnace. The special temperature field setting requirements are as follows: as Figure 2 described, the growth raw materials in the horizontal boat melt into a high-temperature molten liquid in the high-temperature zone of the horizontal Bridgman furnace, and only 0.1 - 0.3 cm of the seed crystal at one end of the horizontal boat can melt;

[0036] Preferably, the tip of the seed crystal does not melt, that is, the temperature in the middle of the seed crystal needs to be set to the melting point of LaBr 3 raw material (783 °C);

[0037] Preferably, the temperature gradient of the horizontal Bridgman furnace is set to 5 - 20 °C per centimeter, and further preferably, the temperature gradient is set to 5 - 10 °C per centimeter;

[0038] Preferably, the center of the seed crystal in the horizontal boat in the horizontal Bridgman furnace is located at the position where the melting point temperature of LaBr 3 raw material is located. On the side of the seed crystal away from the growth raw materials, it cools down from the melting point temperature according to the set temperature gradient, ensuring that the temperature at the end of the seed crystal is within the range of 743 - 775 °C, so that the side of the seed crystal away from the growth raw materials does not melt; on the side of the seed crystal close to the growth raw materials, it heats up from the melting point temperature to 10 - 60 °C above the melting point according to the set temperature gradient. Further preferably, the temperature range is 10 - 20 °C above the melting point to obtain a high-temperature constant temperature field; keep the horizontal boat in the above temperature field for 6 - 36 h, and further preferably, the holding time is 12 - 24 h, and the growth raw materials melt into a high-temperature molten liquid in the high-temperature constant temperature field.

[0039] Step 4: Control the horizontal movement of the quartz crucible or the heater, so that the horizontal boat and the furnace body heater move slowly relative to each other, so that the relative position of the horizontal boat moves towards the low-temperature zone, that is, the melt zone moves towards the seed crystal direction. The horizontal movement speed is 0.1 - 5 mm per hour, and preferably the movement rate is 0.1 - 1 mm per hour. Finally, when the position of the end of the horizontal boat is at a temperature lower than the melting point (783 °C) of LaBr 3 raw material, stop moving;

[0040] Step 5: The grown crystal is slowly cooled at a rate of 5 - 50 °C per hour to an annealing field at a temperature of 450 - 650 °C and held for 12 - 48 h. Then it is slowly cooled to room temperature at a rate of 5 - 50 °C per hour.

[0041] Further preferably, the cooling rate is 10 - 20 °C per hour, the annealing temperature is 550 - 600 °C, and the annealing time is 24 - 36 h.

[0042] Step 6: The grown crystal is cut and processed, and then polished in an inert atmosphere. The crystal is polished into the required shape and encapsulated into a detector of a certain specification.

[0043] A further technical solution of the present invention is that the material of the horizontal boat in each step includes but is not limited to quartz, pBN, graphite, alumina, platinum, and various crucible materials coated with a carbon film.

[0044] By using the horizontal Bridgman method in the present invention, a free space can be maintained above the melt, alleviating the constraint and extrusion of the crucible on the crystal; and a low water-oxygen environment is further maintained through reactive gases to inhibit the formation of oxygen halides and avoid the adhesion of the LaBr 3 :Ce ingot to the wall of the horizontal boat; and combined with the c-direction seed crystal and growth with a small temperature gradient to improve the yield of the LaBr 3 :Ce ingot.

[0045] Example 1:

[0046] Step 1: Under an inert atmosphere in a glove box, load the growth raw materials LaBr 3 , CeBr 3 into a clean and dry quartz boat with an inner diameter of 3 inches coated with a carbon film in a proportion that conforms to the crystal stoichiometry of La 0.95 Ce 0.05 Br 3 . The loading mass should satisfy that the height after melting the growth raw materials is 2 / 3 of the height of the crucible. Load a c-direction seed crystal into the seed crystal bag of the horizontal boat, and the specifications of the seed crystal are a diameter of 6 mm and a length of 45 mm;

[0047] Step 2: Under an inert atmosphere, place the horizontal boat 7 loaded with the growth raw materials 6 into the quartz crucible 8, plug in the quartz plug 9, transfer it out of the inert gas glove box under air isolation conditions, and connect it to a vacuum sealing unit. First, evacuate the quartz crucible to 8 vacuum, and when the vacuum degree reaches 5×10 -5 Pa, then fill it with a mixed gas of high-purity (6N and above) Ar gas and CBr 4 ; then use a hydrogen-oxygen flame to seal the quartz crucible, and the proportion of CBr 4 in the mixed gas is 10%;

[0048] Step 3: Place the sealed quartz crucible 8 in step 2 on the quartz support 10 in the horizontal Bridgman furnace. The inner wall of the quartz furnace chamber of the horizontal Bridgman furnace is provided with heating wires 2, the outer wall is provided with an alumina insulation board 1 and a zirconia partition board 3, and a nano-aerogel insulation blanket 5 is provided at the inlet. As Figure 2 shown, the growth raw materials 6 in the horizontal boat 7 are melted into a high-temperature molten liquid in the high-temperature zone of the horizontal Bridgman furnace, and only 0.1 - 0.3 cm of the seed crystal at one end of the horizontal boat can be melted. Preferably, the tip of the seed crystal is not melted, that is, the temperature in the middle of the seed crystal needs to be set to LaBr 3Melting point of the raw material (783 °C); with the center of the seed crystal as the boundary, the seed crystal on the side far from the raw material does not melt, and the temperature field is a temperature gradient field with a decreasing temperature gradient, and the range of the gradient is 10 °C decrease per centimeter. The seed crystal on the side close to the raw material melts, and the temperature field gradually changes from the melting point to a high-temperature constant temperature field, and the temperature of the high-temperature constant temperature field is 20 °C above the melting point. The horizontal boat 7 is heat-insulated in this temperature field for 24 h;

[0049] Step 4: Control the horizontal movement of the heater to cause a slow relative movement between the horizontal boat and the furnace body heater, so that the relative position of the horizontal boat moves towards the low-temperature area, that is, the melt area moves towards the seed crystal direction. The horizontal movement speed is 1 mm per hour. Finally, the position of the end of the horizontal boat stops moving when it is at a temperature lower than the temperature position of the melting point of LaBr 3 (783 °C);

[0050] Step 5: The grown crystal is slowly cooled at a rate of 10 °C per hour to the annealing field at a temperature of 550 °C and heat-insulated for 24 h. Then it is slowly cooled to room temperature at a rate of 10 °C per hour.

[0051] Step 6: The grown crystal is cut and processed, and then polished in an inert atmosphere. The polished crystal has a specification of 12.7×25.4×50.8 mm 3 , and is encapsulated into a detector with a specification of 18×30×55 mm 3 .

[0052] The cerium bromide detector of the present embodiment has a square shape with a specification of 18×30×55 mm 3 , and the energy spectrum diagram measured under the 137 Cs source is as shown in Figure 3 . The energy resolution (@662 keV) is 2.8%.

[0053] Example 2:

[0054] Step 1: Under an inert atmosphere in a glove box, load the growth raw materials LaBr 3 , CeBr 3 into a clean and dry quartz boat with an inner diameter of 3 inches coated with a carbon film in accordance with the stoichiometric ratio of the La 0.999 Ce 0.001 Br 3 crystal, and incorporate 1000 ppmW of SrBr 2 into the raw materials. The loading mass satisfies that the height after the raw materials melt is 2 / 3 of the height of the crucible. Load a c-axis seed crystal into the seed crystal bag of the horizontal boat. The specification of the seed crystal is a diameter of 6 mm and a length of 45 mm;

[0055] Step 2: Under an inert atmosphere, place the horizontal boat 7 filled with the growth raw material 6 into the quartz crucible 8, plug the quartz stopper 9, transfer it out of the inert gas glove box under air isolation conditions, and connect it to the vacuum sealing unit. First, evacuate the quartz crucible to a vacuum of 5×10 -5 Pa, then fill it with a mixed gas of high-purity (6N or above) Ar gas at 0.1 atm and CBr 4 ; then use an oxyhydrogen flame to seal the quartz crucible, and the proportion of CBr 4 in the mixed gas is 15%;

[0056] Step 3: Place the sealed quartz crucible 8 in step 2 on the quartz support 10 in the horizontal Bridgman furnace. The inner wall of the quartz furnace chamber of the horizontal Bridgman furnace is provided with heating wires 2, the outer wall is provided with an alumina insulation board 1 and a zirconia partition 3, and a nano-aerogel insulation blanket 5 is provided at the inlet. The special temperature field setting requirements are as follows: as Figure 2 in, the raw material in the horizontal boat melts into a high-temperature molten liquid in the high-temperature zone of the horizontal Bridgman furnace, and only 0.2 - 0.3 cm of the seed crystal at one end of the horizontal boat can melt. Preferably, the tip of the seed crystal does not melt, that is, the temperature in the middle of the seed crystal needs to be set to the melting point of the LaBr 3 raw material (783 °C); with the center of the seed crystal as the boundary, the seed crystal on the side far from the raw material does not melt, and the temperature field is a temperature gradient field with a gradient range of 5 °C per centimeter. The melting temperature field of the seed crystal on the side close to the raw material gradually changes from the melting point to a high-temperature constant temperature field, and the temperature of the high-temperature constant temperature field is 10 °C above the melting point. The horizontal boat is kept warm in this temperature field for 24 h;

[0057] Step 4: Control the horizontal movement of the heater to make the horizontal boat and the furnace body heater move slowly relative to each other, so that the relative position of the horizontal boat moves towards the low-temperature zone, that is, the melt zone moves towards the seed crystal direction. The horizontal movement speed is 0.5 mm per hour. Finally, stop moving when the position of the end of the horizontal boat is at a temperature lower than the melting point (783 °C) of the LaBr 3 raw material;

[0058] Step 5: The grown crystal is slowly cooled at a rate of 20 °C per hour to an annealing field at a temperature of 600 °C and kept warm for 36 h. Then it is slowly cooled to room temperature at a rate of 20 °C per hour.

[0059] Step 6: The grown crystal is cut and processed, and then polished in an inert atmosphere. The polished crystal has a specification of φ25.4×122 mm 3 and is encapsulated into a detector with a specification of φ31.75*150 mm 3 .

[0060] The cylindrical detector prepared in this example is a lanthanum cerium bromide scintillation crystal detector for well logging encapsulated with high-temperature resistance, with a specification of φ31.75×150mm 3 , and the energy resolution (@662 keV) of the energy spectrum measured under the 137 Cs source is < 7% at room temperature.

[0061] Example 3:

[0062] Step 1: Under an inert atmosphere in a glove box, load the growth raw materials LaBr 3 , CeBr 3 into a clean and dry quartz boat with a 3-inch inner diameter coated with carbon film in accordance with the stoichiometric ratio of the La 0.9 Ce 0.1 Br 3 crystal, and incorporate 1500 ppmW of CaBr 2 into the raw materials. The loading mass should satisfy that the height of the raw materials after melting is 2 / 3 of the height of the crucible. Load a c-axis seed crystal into the seed crystal bag of the horizontal boat. The specification of the seed crystal is a diameter of 6 mm and a length of 45 mm;

[0063] Step 2: Under an inert atmosphere, place the horizontal boat 7 loaded with the growth raw materials 6 into the quartz crucible 8, plug it with a quartz stopper 9, transfer it out of the inert gas glove box under air isolation conditions, and connect it to a vacuum sealing unit. First, evacuate the quartz crucible to 8 vacuum. When the vacuum degree reaches 5×10 -5 Pa, then fill it with a mixed gas of high-purity (6N and above) Ar gas at 0.1 atm and CCl 4 ; then use a hydrogen-oxygen flame to seal the quartz crucible. The proportion of CCl 4 in the mixed gas is taken as 20%;

[0064] Step 3: Place the sealed quartz crucible 8 in step 2 on the quartz support 10 in a horizontal Bridgman furnace. The inner wall of the quartz furnace chamber of the horizontal Bridgman furnace is provided with heating wires 2, the outer wall is provided with an alumina insulation board 1 and a zirconia partition 3, and a nano-aerogel insulation blanket 5 is provided at the inlet. Special temperature field setting requirements are as follows: As Figure 2 in, the raw materials in the horizontal boat melt into a high-temperature molten liquid in the high-temperature zone of the horizontal Bridgman furnace, and only 0.2 - 0.3 cm of the seed crystal at one end of the horizontal boat can melt. Preferably, the tip of the seed crystal does not melt, that is, the temperature in the middle of the seed crystal needs to be set to the melting point of LaBr 3 (783 °C); taking the center of the seed crystal as the boundary, the seed crystal on the side far from the raw materials does not melt, and the temperature field is a temperature gradient field with a gradient range of 7.5 °C per centimeter. The melting temperature field of the seed crystal on the side close to the raw materials gradually changes from the melting point to a high-temperature constant temperature field, and the temperature of the high-temperature constant temperature field is 15 °C above the melting point. The horizontal boat is kept warm in this temperature field for 36 h;

[0065] Step 4: Control the horizontal movement of the heater to cause a slow relative movement between the horizontal boat and the furnace body heater, so that the relative position of the horizontal boat moves towards the low-temperature zone, that is, the melt zone moves towards the seed crystal direction. The horizontal movement speed is 0.1 mm per hour. Finally, the position of the tail end of the horizontal boat is lower than the temperature position of the melting point (783 °C) of LaBr 3 of the raw material, and then stop the movement;

[0066] Step 5: Slowly cool the grown crystal at a rate of 15 °C per hour to an annealing field at a temperature of 575 °C and hold it for 30 h. Then slowly cool it to room temperature at a rate of 15 °C per hour.

[0067] Step 6: Cut and process the grown crystal, and then polish it in an inert atmosphere. The polished crystal has a specification of φφ38×38 mm 3 , and encapsulate it into a detector with a specification of φ42×40 mm 3 .

[0068] The cylindrical detector prepared in this example is a cerium bromide lanthanum scintillation crystal detector with conventional encapsulation. The energy resolution (@662 keV) of the energy spectrum measured under a 137 Cs source is better than 3% at room temperature.

[0069] Example 4:

[0070] Step 1: Under an inert atmosphere in a glove box, load the growth raw materials LaBr 3 , CeBr 3 into a clean and dry quartz boat with a 3-inch inner diameter coated with a carbon film in accordance with the stoichiometric ratio of the La 0.9 Ce 0.1 Br 3 crystal, and incorporate 2000 ppmW of ZnBr2 into the raw materials. The loading mass satisfies that the height after the raw materials are melted is 1 / 2 of the height of the crucible. Load a c-axis seed crystal into the seed crystal pocket of the horizontal boat. The specification of the seed crystal is a diameter of 6 mm and a length of 45 mm;

[0071] Step 2: Under an inert atmosphere, load the horizontal boat 7 loaded with the growth raw material 6 into the quartz crucible 8, plug in the quartz plug 9, transfer it out of the inert gas glove box under air isolation conditions, and connect it to a vacuum sealing unit. First, evacuate the quartz crucible to a vacuum of 5×10 -5 Pa, and then fill it with a mixed gas of high-purity (6N and above) Ar gas and SiCl 4 at 0.1 atm; then use a hydrogen-oxygen flame to seal the quartz crucible. The proportion of SiCl 4 in the mixed gas is 5%;

[0072] Step 3: Place the sealed quartz crucible 8 in step 2 on the quartz support 10 in the horizontal Bridgman furnace. The inner wall of the quartz furnace chamber of the horizontal Bridgman furnace is provided with heating wires 2, the outer wall is provided with an alumina thermal insulation board 1 and a zirconia partition 3, and a nano-aerogel thermal insulation blanket 5 is provided at the inlet. Special requirements for the temperature field setting are as follows: As Figure 2 In, the raw materials in the horizontal boat melt into a high-temperature molten liquid in the high-temperature zone of the horizontal Bridgman furnace, and only the seed crystal at one end of the horizontal boat can melt within the range of 0.2 - 0.3 cm. Preferably, the tip of the seed crystal does not melt, that is, the temperature in the middle of the seed crystal needs to be set to the melting point of LaBr 3 (783 °C); with the center of the seed crystal as the boundary, the seed crystal on the side far from the raw material does not melt, and the temperature field is a temperature gradient reduction field, with the gradient ranging from 7.5 °C per centimeter. The melting temperature field of the seed crystal on the side close to the raw material gradually changes from the melting point to a high-temperature constant temperature field, and the temperature of the high-temperature constant temperature field is 30 °C above the melting point. The horizontal boat is insulated in this temperature field for 10 h;

[0073] Step 4: Control the horizontal movement of the heater to make the horizontal boat and the furnace body heater move slowly relative to each other, so that the relative position of the horizontal boat moves towards the low-temperature zone, that is, the melt zone moves towards the seed crystal direction. The horizontal movement speed is 2 mm per hour. Finally, the horizontal boat stops moving when the position of the end of the horizontal boat is at a temperature lower than the melting point (783 °C) of the LaBr 3 raw material;

[0074] Step 5: The grown crystal is slowly cooled at a rate of 5 °C per hour to an annealing field at a temperature of 450 °C and insulated for 48 h. Then it is slowly cooled to room temperature at a rate of 5 °C per hour.

[0075] Step 6: The grown crystal is cut and processed, and then polished in an inert atmosphere. The polished crystal has a specification of φφ25.4×50 mm 3 and is encapsulated into a detector with a specification of φ31.75*75 mm.

[0076] The cylindrical detector prepared in this embodiment is a lanthanum bromide cerium scintillation crystal detector for well logging using high-temperature resistant encapsulation, with a specification of φ31.75*75 mm. At 137 the energy resolution (@662 keV) of the energy spectrum measured under the Cs source is <5% at room temperature.

[0077] Example 5:

[0078] Step 1: Under an inert atmosphere in a glove box, place the growth raw materials LaBr 3 , CeBr 3 in accordance with the compliance of La 0.9 Ce 0.1 Br 3The crystal with stoichiometric ratio is loaded into a clean and dry quartz boat with a 3-inch inner diameter and coated with carbon film. 2500 ppmW of MgBr2 is doped into the raw material, and the loading mass meets the requirement that the height after melting of the raw material is 2 / 3 of the height of the crucible. A c-axis seed crystal is loaded into the seed crystal bag of the horizontal boat. The specifications of the seed crystal are a diameter of 6 mm and a length of 45 mm;

[0079] Step 2: Under an inert atmosphere, the horizontal boat 7 loaded with the growth raw material 6 is loaded into the quartz crucible 8 and a quartz plug 9 is inserted. It is transferred out of the inert gas glove box under air isolation conditions and connected to a vacuum sealing unit. First, the quartz crucible is evacuated to a vacuum of 8, and when the vacuum degree reaches 5×10 -5 Pa, then a high-purity (6N and above) Ar gas and H 2 mixed gas with a pressure of 0.1 atm is filled; then the quartz crucible is sealed with a hydrogen-oxygen flame, and the proportion of H 2 in the mixed gas is taken as 20%;

[0080] Step 3: Place the sealed quartz crucible 8 in step 2 on the quartz support 10 in the horizontal Bridgman furnace. The inner wall of the quartz furnace chamber of the horizontal Bridgman furnace is provided with heating wires 2, the outer wall is provided with an alumina insulation board 1 and a zirconia partition 3, and a nano-aerogel insulation blanket 5 is provided at the inlet. Special temperature field setting requirements are as follows: as Figure 2 in it, the raw material in the horizontal boat melts into a high-temperature molten liquid in the high-temperature zone of the horizontal Bridgman furnace, and only 0.2 - 0.3 cm of the seed crystal at one end of the horizontal boat can melt. Preferably, the tip of the seed crystal does not melt, that is, the temperature in the middle of the seed crystal needs to be set to the melting point of LaBr 3 (783 °C); with the center of the seed crystal as the boundary, the seed crystal on the side far from the raw material does not melt, and the temperature field is a temperature gradient field with a gradient range of 20 °C per centimeter. The melting temperature field of the seed crystal on the side close to the raw material gradually changes from the melting point to a high-temperature constant temperature field, and the temperature of the high-temperature constant temperature field is 60 °C above the melting point.

[0081] The horizontal boat is insulated in this temperature field for 6 h;

[0082] Step 4: Control the horizontal movement of the heater to make the horizontal boat and the furnace body heater move slowly relative to each other, so that the relative position of the horizontal boat moves towards the low-temperature zone, that is, the melt zone moves towards the seed crystal direction. The horizontal movement speed is 3 mm per hour. Finally, when the position of the tail end of the horizontal boat is at a temperature lower than the melting point (783 °C) of the LaBr 3 raw material, stop moving;

[0083] Step 5: The grown crystal is slowly cooled at a rate of 50 °C per hour to an annealing field at a temperature of 650 °C and insulated for 12 h. Then it is slowly cooled to room temperature at a rate of 50 °C per hour.

[0084] Step 6: The grown crystal is cut and processed, and then polished in an inert atmosphere. The polished crystal has a specification of φφ25×25 mm 3 , and is encapsulated into a detector with a specification of φ32×30 mm 3 .

[0085] The cylindrical detector prepared in this example is a cerium lanthanum bromide scintillation crystal detector using difficult low-temperature encapsulation. The energy resolution (@662 keV) of the energy spectrum measured under a 137 Cs source is better than 3% at room temperature.

[0086] Example 6:

[0087] Step 1: Under an inert atmosphere in a glove box, load the growth raw materials LaBr 3 , CeBr 3 into a clean and dry quartz boat with an inner diameter of 3 inches coated with a carbon film in accordance with the stoichiometric ratio of the La 0.9 Ce 0.1 Br 3 crystal. Add 3000 ppmW of BaBr2 to the raw materials, and the loading mass should meet the requirement that the height after melting of the raw materials is 2 / 3 of the height of the crucible. Load a c-axis seed crystal into the seed crystal bag of the horizontal boat. The specification of the seed crystal is a diameter of 6 mm and a length of 45 mm;

[0088] Step 2: Under an inert atmosphere, place the horizontal boat 7 loaded with the growth raw materials 6 into the quartz crucible 8, plug in the quartz plug 9, transfer it out of the inert gas glove box under air isolation conditions, and connect it to a vacuum sealing unit. First, evacuate the quartz crucible to 8 vacuum until the vacuum degree reaches 5×10 -5 Pa, and then fill it with a mixed gas of high-purity (6N and above) Ar gas at 0.1 atm and CCl 4 ; then use a hydrogen-oxygen flame to seal the quartz crucible. The proportion of CCl 4 in the mixed gas is 30%;

[0089] Step 3: Place the sealed quartz crucible 8 in step 2 on the quartz support 10 in a horizontal Bridgman furnace. The inner wall of the quartz furnace chamber of the horizontal Bridgman furnace is provided with heating wires 2, the outer wall is provided with an alumina insulation board 1 and a zirconia partition 3, and a nano-aerogel insulation blanket 5 is provided at the inlet. Special temperature field setting requirements are as follows: As Figure 2 in, the raw materials in the horizontal boat melt into a high-temperature molten liquid in the high-temperature zone of the horizontal Bridgman furnace, and only 0.2 - 0.3 cm of the seed crystal at one end of the horizontal boat can melt. Preferably, the tip of the seed crystal does not melt, that is, the temperature in the middle of the seed crystal needs to be set to LaBr 3The melting point (783 °C); with the center of the seed crystal as the boundary, the seed crystal on the side far from the raw material does not melt, and the temperature field is a decreasing temperature gradient field, with the gradient ranging from 15 °C per centimeter. On the side of the seed crystal close to the raw material, the melting temperature field gradually changes from the melting point to a high-temperature constant temperature field, and the temperature of the high-temperature constant temperature field is 40 °C above the melting point. The horizontal boat is kept warm in this temperature field for 12 h;

[0090] Step 4: Control the horizontal movement of the heater to make the horizontal boat and the furnace body heater move slowly relative to each other, so that the relative position of the horizontal boat moves towards the low-temperature area, that is, the melt area moves towards the seed crystal direction. The horizontal movement speed is 5 mm per hour. When the position of the end of the horizontal boat is finally at a temperature lower than the melting point (783 °C) of the LaBr3 raw material, the movement stops;

[0091] Step 5: The grown crystal is slowly cooled at a rate of 30 °C per hour to an annealing field at a temperature of 500 °C and kept warm for 30 h. Then it is slowly cooled to room temperature at a rate of 30 °C per hour.

[0092] Step 6: The grown crystal is cut and processed, and then polished in an inert atmosphere. The processed crystal has a specification of 6×6×50 mm 3 , and is encapsulated into a multi-pixel detector with an 8×8 array specification of 56*56*53 mm.

[0093] The square detector prepared in this embodiment is a cerium bromide lanthanum scintillation crystal multi-pixel detector encapsulated in an 8×8 array. The energy resolution (@662 keV) of the energy spectrum measured under the 137 Cs source is better than 13% at room temperature.

[0094] In summary, the present invention provides a method for growing cerium bromide lanthanum scintillation crystals using the horizontal Bridgman method, which solves the problems that the cerium bromide lanthanum scintillation crystals grown by the vertical Bridgman method are extremely prone to cracking and it is difficult to obtain a complete ingot, realizes the improvement of the ingot yield and utilization rate, can effectively realize the preparation of various special-shaped and cylindrical cerium bromide lanthanum scintillation crystals, the crystal sizes prepared meet various requirements, and the performance resolution of the prepared detector reaches the international level.

[0095] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can still be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method, characterized in that, it includes the following steps: S1 Under an inert atmosphere, place the growth raw materials LaBr 3 , CeBr 3 in a horizontal boat and place seeds in the seed pocket of the horizontal boat; S2 Load the above horizontal boat into a quartz crucible, evacuate, fill with a reaction mixture gas, and seal the quartz crucible; S3 sets the temperature gradient in the horizontal Bridgman furnace to be 5°C to 20°C per centimeter, places the sealed quartz crucible in the horizontal Bridgman furnace, and the center of the seed crystal in the horizontal boat is located at the melting point temperature of LaBr 3 At the melting point temperature, the side of the seed crystal away from the growth raw material is cooled with a gradient, and the side of the seed crystal close to the growth raw material is heated with a gradient to a high-temperature constant temperature field, and the temperature of the high-temperature constant temperature field is above the melting point of the growth raw material; S4 After all the growth raw materials are melted in a high-temperature constant temperature field, move the horizontal boat in the direction where the seed crystal is not melted to grow crystals to obtain a cerium lanthanum bromide crystal precursor; S5 Cool down, anneal, keep warm, and then cool down the cerium lanthanum bromide crystal precursor to obtain a cerium lanthanum bromide crystal.

2. The method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method as described in claim 1, characterized in that, In S1, the proportion of CeBr in the growth raw material 3 is 0.1 at% to 10 at%, and the filling height range of the growth raw material is 1 / 2 to 2 / 3 of the horizontal boat height.

3. The method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method as described in claim 1, characterized in that, In S1, the seed crystal is a c-direction seed crystal.

4. The method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method as described in claim 1, characterized in that, In S1, the growth raw materials LaBr 3 and CeBr 3 are also doped with a co-dopant, the doping amount of the co-dopant is 0 ppmW to 3000 ppmW, and the co-dopant is a bromide combination of one or several elements selected from Ga, In, Bi, Mg, Ca, Sr, Ba, Zn, Cd, Zr, and Hf.

5. The method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method as described in claim 1, characterized in that, In S2, the reaction mixture gas is high-purity argon and a reaction gas, and the proportion of the reaction gas in the reaction mixture gas ranges from 5% to 30%; the reaction gas is a reactive gas of the halogen group or the silane group compound.

6. The method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method as described in claim 1, characterized in that, In S3, the melting range of the seed crystal is 0.1 cm to 0.3 cm, and the temperature of the high-temperature constant-temperature field is 10 °C to 60 °C above the melting point of LaBr 3 The horizontal boat is kept at this temperature gradient field for 6 h to 36 h.

7. The method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method as described in claim 1, characterized in that, In S4, the moving speed of the horizontal boat is 0.1 mm to 5 mm per hour until the temperature at the tail of the horizontal boat is lower than the melting point of LaBr 3 .

8. The method for growing cerium lanthanum bromide scintillation crystal using the horizontal Bridgman method as described in claim 1, characterized in that, In S5, the cerium lanthanum bromide crystal precursor is cooled down to 450°C - 650°C at a rate of 5 - 50°C per hour, kept warm for 12h - 48h, and then cooled down to room temperature at a rate of 5°C - 50°C per hour.

9. A cerium lanthanum bromide scintillation crystal, characterized in that, it is prepared by using the method described in any one of claims 1 - 8.

10. An application of a cerium lanthanum bromide scintillation crystal, characterized in that, The cerium lanthanum bromide scintillation crystal described in claim 9 or the cerium lanthanum bromide scintillation crystal prepared by using the method described in any one of claims 1 - 8 is cut and processed, polished in an inert atmosphere, and encapsulated into a detector of a certain specification.

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