CN114197030B - Preparation method of lithium hydride single crystal and device used in preparation method - Google Patents
Preparation method of lithium hydride single crystal and device used in preparation method Download PDFInfo
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- CN114197030B CN114197030B CN202111545952.8A CN202111545952A CN114197030B CN 114197030 B CN114197030 B CN 114197030B CN 202111545952 A CN202111545952 A CN 202111545952A CN 114197030 B CN114197030 B CN 114197030B
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/006—Controlling or regulating
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
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Abstract
The invention relates to the technical field of lithium hydride single crystal preparation, in particular to a preparation method of a lithium hydride single crystal and a device used by the same. The invention provides a preparation method of lithium hydride single crystal, which comprises the following steps: in the atmosphere of hydrogen, liquid lithium hydride in a static state grows a single crystal in a moving temperature field; when the single crystal grows, the temperature gradient of the liquid lithium hydride at the solid-liquid interface is less than or equal to 10 ℃/cm, and the moving temperature field is formed by moving the heating device. The lithium hydride single crystal prepared by the preparation method provided by the invention has few crystal defects and high quality. The results of the examples show that the lithium hydride single crystal prepared by the preparation method provided by the invention is semitransparent, the X-ray diffraction peaks only comprise (002) and (004), the diffraction peak intensity is high and sharp, and the lithium hydride single crystal has less step defects and high single crystal quality.
Description
Technical Field
The invention relates to the technical field of lithium hydride single crystals, in particular to a preparation method of a lithium hydride single crystal and a device used by the same.
Background
Potassium hydride is considered to be the most effective neutron shielding material at present because it has a hydrogen density (the number of hydrogen atoms contained in a unit volume) close to that of water and has a large neutron absorption cross section. In addition, lithium hydride has the advantages of high melting point, low decomposition pressure, low density and the like, and is often used for neutron shielding, ultra-light structural parts and hydrogen fuel sources in nuclear power aircrafts and space nuclear energy devices, so that attention is paid to the lithium hydride.
In order to investigate the physicochemical properties of potassium hydride, it is necessary to obtain a high-quality lithium hydride single crystal as a sample for analytical investigation. At present, the preparation method of lithium hydride single crystal mainly includes a melting temperature reduction method and a Bridgman-Stockbarger method.
The melting cooling method is used for cooling the whole lithium hydride in the molten state to be below the melting point for crystallization; the Bridgman-Stockbarger method realizes the gradual crystallization of the molten lithium hydride to obtain single crystal crystals by slowly moving a crucible to enable the molten lithium hydride to pass through a lithium hydride melting point isotherm. However, the lithium hydride single crystal obtained by the above two methods still has many defects in crystal structure and is inferior in quality.
Disclosure of Invention
In view of this, the present invention provides a method for producing a lithium hydride single crystal and an apparatus used therefor, and the lithium hydride single crystal produced by the production method provided by the present invention has few defects and high quality.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of lithium hydride single crystal, which comprises the following steps:
growing a single crystal in a moving temperature field by liquid lithium hydride in an atmosphere of hydrogen; when the single crystal grows, the temperature gradient of the liquid lithium hydride at the solid-liquid interface is less than or equal to 10 ℃/cm, and the moving temperature field is formed by moving the heating device.
Preferably, the temperature gradient of the liquid lithium hydride at the solid-liquid interface is 6 to 10 ℃/cm when the single crystal is grown.
Preferably, the pressure of the hydrogen gas is 0.15 to 0.4MPa.
Preferably, the heating device moves at a uniform speed, and the moving speed of the heating device is 1-10 mm/h.
Preferably, the preparation method of the liquid lithium hydride comprises the following steps:
in the atmosphere of hydrogen, heating lithium hydride to a first temperature by a heating device for first heat preservation to obtain initial liquid lithium hydride, wherein the first temperature is more than or equal to 740 ℃;
and in the atmosphere of hydrogen, establishing a gradient temperature field in the middle of the initial liquid lithium hydride by using a heating device, and then carrying out second heat preservation, wherein the temperature gradient of the liquid lithium hydride from bottom to top after the gradient temperature field is established is less than or equal to 10 ℃/cm.
Preferably, the first temperature is 740 to 760 ℃, and the first heat preservation time is 12 to 24 hours; the heating rate from room temperature to the first temperature is 100-200 ℃/h.
Preferably, the second heat preservation time is 1-3 h; after the gradient temperature field is established, the temperature gradient of the liquid lithium hydride from bottom to top is 6-10 ℃/cm.
Preferably, the growing single crystal directly results in an initial lithium hydride single crystal, further comprising: and cooling the initial lithium hydride single crystal to a third temperature, and carrying out third heat preservation, wherein the third temperature is 550-600 ℃, the third heat preservation time is 6-12 h, and the cooling rate of cooling to the third temperature is 1-4 ℃/h.
The invention provides a single crystal growth device used in the preparation method of the technical scheme, which comprises the following steps:
a furnace body 5;
the furnace body moving system 6 is connected with the furnace body 5, and the furnace body moving system 6 is used for controlling the furnace body 5 to move along the axial direction;
the lower-region heating body 4 and the upper-region heating body 3 are fixedly connected with the inner wall of the furnace body 5 from bottom to top, the lower-region heating body 4 and the upper-region heating body 3 are independently controlled to heat, the lower-region heating body 4 forms a lower cavity, the upper-region heating body 3 forms an upper cavity, and the lower cavity is communicated with the upper cavity;
a water-cooled crucible 8 disposed in the lower chamber;
a single crystal growth vessel 1 disposed in the upper chamber;
the single crystal growth container 1 is provided with a gas inlet and outlet conduit 9;
a sample container 2 disposed in the single crystal growth vessel 1.
Preferably, the heating apparatus further comprises a first thermocouple 7-1 fixedly connected with the lower zone heating element 4;
and the second thermocouple 7-2 is fixedly connected with the upper zone heating element 3.
The invention provides a preparation method of lithium hydride single crystal, which comprises the following steps: growing a single crystal in a moving temperature field by liquid lithium hydride in an atmosphere of hydrogen; when the single crystal grows, the temperature gradient of the liquid lithium hydride at the solid-liquid interface is less than or equal to 10 ℃/cm, and the moving temperature field is formed by moving the heating device. The preparation method provided by the invention further improves the Bridgman-Stockbarger method, the movement of the crucible containing the lithium hydride liquid in a fixed temperature field is changed into the movement of the liquid lithium hydride in a movable heating device to form a temperature field for growing the single crystal, the vibration generated in the process of growing the single crystal by the liquid lithium hydride is effectively reduced, a stable environment is provided for the growth of the single crystal by the lithium hydride, and the structural defect caused by the environmental vibration in the process of growing the single crystal is reduced; meanwhile, the method provided by the invention controls the temperature gradient of liquid lithium hydride at the solid-liquid interface to be less than or equal to 10 ℃/cm when the single crystal is grown, slows down the growth speed of the lithium hydride single crystal and is also beneficial to reducing the crystal defects of the lithium hydride single crystal. Therefore, the lithium hydride single crystal prepared by the preparation method provided by the invention has few crystal defects and high quality. The results of the examples show that the lithium hydride single crystal prepared by the preparation method provided by the invention is semitransparent, the X-ray diffraction peaks only comprise (002) and (004), the diffraction peak intensity is high and sharp, and the lithium hydride single crystal has less step defects and high single crystal quality.
The invention provides a single crystal growth device used in the preparation method of the technical scheme, which comprises the following steps: a furnace body 5; a furnace body moving system 6 connected with the furnace body 5; the furnace body moving system 6 is used for controlling the furnace body 5 to move along the axial direction; a lower-region heating element 4 and an upper-region heating element 3 which are fixedly connected with the inner wall of the furnace body 5 from bottom to top, wherein the lower-region heating element 4 and the upper-region heating element 3 are independently controlled to heat, the lower-region heating element 4 forms a lower chamber, the upper-region heating element 3 forms an upper chamber, and the lower chamber is communicated with the upper chamber; a water-cooled crucible 8 disposed in the lower chamber; a single crystal growth vessel 1 disposed in the upper chamber; the single crystal growth container 1 is provided with a gas inlet and outlet conduit 9; a sample crucible 2 disposed in the single crystal growth vessel 1. According to the single crystal growth device provided by the invention, the lower region heating element 4 and the upper region heating element 3 are independently controlled to heat, and are matched with the water-cooled crucible 8 to provide a temperature field for the liquid lithium hydride to grow single crystals, meanwhile, the furnace body 5 in the device provided by the invention can freely move along the axial direction through the furnace body moving system 6, and when the furnace body 5 moves, the lower region heating element 4 and the upper region heating element 3 which are fixedly connected with the inner wall of the furnace body 5 are driven to move, so that a moving temperature field is formed, and the liquid lithium hydride in a standing state can grow single crystals in the moving temperature field formed by the heating device. The device provided by the invention is simple to operate.
Drawings
FIG. 1 is a schematic view of a single crystal growing apparatus according to an embodiment of the present invention;
wherein, 1-single crystal growth container, 2-crucible, 3-upper zone heating element, 4-lower annular heating element, 5-furnace body, 6-furnace body moving system, 7-1-first thermocouple, 7-2-second thermocouple, 8-water cooling crucible, 9-gas inlet and outlet conduit;
FIG. 2 is a schematic diagram of a lithium hydride single crystal prepared in example 1 of the present invention;
FIG. 3 is an X-ray diffraction chart of a lithium hydride single crystal produced in example 1 of the present invention.
Detailed Description
The invention provides a preparation method of lithium hydride single crystal, which comprises the following steps:
growing a single crystal in a moving temperature field by liquid lithium hydride in an atmosphere of hydrogen; when the single crystal grows, the temperature gradient of the liquid lithium hydride at the solid-liquid interface is less than or equal to 10 ℃/cm, and the moving temperature field is formed by moving the heating device.
In the present invention, the method for preparing liquid lithium hydride preferably comprises the steps of:
in the atmosphere of hydrogen, heating lithium hydride to a first temperature for first heat preservation to obtain initial liquid lithium hydride, wherein the first temperature is more than or equal to 740 ℃;
and in the atmosphere of hydrogen, cooling the initial liquid lithium hydride from the first temperature to a second temperature, and carrying out second heat preservation to obtain the liquid lithium hydride, wherein the second temperature is 40-75 ℃ lower than the first temperature.
In the hydrogen atmosphere, the temperature of lithium hydride is raised to a first temperature for first heat preservation to obtain initial liquid lithium hydride, wherein the first temperature is more than or equal to 740 ℃.
In the present invention, the purity of the lithium hydride is preferably 99% or more, and in a specific embodiment of the present invention, the purity of the lithium hydride is specifically 99% or 99.2%.
In a particular embodiment of the invention, the size of the lithium hydride is preferably: the diameter is 24mm, and the length is 100mm.
In the present invention, the lithium hydride is preferably placed in a heating vessel to be heated. The present invention preferably charges the lithium hydride into the heating vessel in a low oxygen and low humidity glove box.
In the present invention, it is preferable that the atmosphere of the heating container is pretreated before the temperature of the lithium hydride is raised. In the present invention, the pretreatment preferably includes: and (4) sequentially carrying out inert gas washing and hydrogen washing. In the present invention, the inert gas washing is preferably argon gas washing, and the number of times of the inert gas washing is preferably 3 times. In the present invention, the inert gas washing is preferably performed by: and vacuumizing the heating container, and introducing inert gas for washing. In the present invention, after the inert gas washing, the heating container is preferably subjected to hydrogen washing, the number of times of the hydrogen washing is preferably 3, and the hydrogen washing is preferably performed in the following specific steps: and vacuumizing the heating device, and introducing hydrogen for washing. In the present invention, the purity of the hydrogen gas used in the present invention is preferably 99.999% at the time of the hydrogen gas washing. In the present invention, the hydrogen gas is particularly preferably purified by a ZrCo chemical bed.
In the present invention, the temperature increase of the lithium hydride is performed in a hydrogen atmosphere, and the pressure of the hydrogen is preferably 0.15 to 0.3MPa.
In the present invention, the first temperature is 740 ℃ or higher, preferably 740 to 760 ℃, and more preferably 745 to 755 ℃. In the present invention, the time for the first heat-retention is preferably 12 to 24 hours, and more preferably 15 to 18 hours. In the present invention, the rate of temperature increase from room temperature to the first temperature is preferably 100 to 200 ℃/h, more preferably 120 to 150 ℃/h.
According to the invention, the lithium hydride is preferably melted at the first temperature and subjected to the first heat preservation, so that the lithium hydride can be fully melted, and impurities in the liquid lithium hydride are deposited under the action of gravity in the first heat preservation process, thereby realizing the layered purification of the liquid lithium hydride.
After the initial liquid lithium hydride is obtained, in the atmosphere of hydrogen, a heating device is adopted to establish a gradient temperature field in the middle of the initial liquid lithium hydride and then carry out second heat preservation, and the temperature gradient of the liquid lithium hydride from bottom to top after the gradient temperature field is established is less than or equal to 10 ℃/cm.
In the present invention, the pressure of the hydrogen gas is preferably 0.15 to 0.3MPa.
In the present invention, the establishment of the gradient temperature field is preferably: heating device includes the upper zone heating member and sets up the lower region heating member of upper zone heating member below, initial liquid lithium hydride is located in the zone of heating of upper zone heating member, set up the device that holds room temperature cooling water in the zone of heating of lower region heating member and let in mobile room temperature cooling water, adopt the upper zone heating member will initial liquid lithium hydride is reduced to the second temperature by first temperature, reduces the second temperature by first temperature with the lower region heating member.
In the present invention, the second temperature is preferably 40 to 75 ℃ lower than the first temperature, and more preferably 45 to 70 ℃.
In the present invention, the second temperature is preferably 685 to 700 ℃, and more preferably 690 ℃.
In the present invention, the time of the second heat-retention is preferably 1 to 3 hours, and more preferably 2 hours.
In the invention, the temperature gradient of the liquid lithium hydride from bottom to top after the gradient temperature field is established is preferably less than or equal to 10 ℃/cm, and more preferably 6-10 ℃/min.
The cooling rate of the invention from the first temperature to the second temperature is preferably 10-20 ℃/h, more preferably 12-15 ℃/h.
According to the invention, the temperature of the liquid lithium hydride is reduced from the first temperature to the second temperature, so that the temperature reduction during the subsequent growth of single crystal by the liquid lithium hydride is reduced, and the defect of the single crystal is reduced.
According to the invention, the liquid lithium hydride is preferably subjected to the second heat preservation at the second temperature, so that the temperature uniformity of the liquid lithium hydride is facilitated.
In the present invention, the moving temperature field is formed by moving a heating device.
In the present invention, the heating device is preferably moved at a uniform speed, and the moving speed of the heating device is preferably 1 to 10mm/h, more preferably 2 to 8mm/h.
In the present invention, the heating means is preferably moved in one direction, and in a specific embodiment of the present invention, the heating means is preferably moved in one direction from the bottom of the container containing the liquid lithium hydride upward.
In the invention, the moving temperature field comprises a melting point isotherm of the lithium hydride, during the moving process of the moving temperature field, the part of the liquid lithium hydride in the temperature field, which is higher than the melting point temperature, is still kept in a liquid state, the part of the liquid lithium hydride, which is lower than the melting point temperature, grows into a lithium hydride single crystal, and the atmosphere equal to the melting point temperature forms a solid-liquid interface.
In the present invention, the temperature gradient of the liquid lithium hydride at the solid-liquid interface during the growth of the single crystal is not more than 10 ℃/cm, preferably 6 to 10 ℃/cm, and more preferably 6 ℃/cm or 10 ℃/cm.
In the present invention, the pressure of the hydrogen gas is preferably 0.15 to 0.4MPa, more preferably 0.2 to 0.35MPa, when growing the single crystal.
In the present invention, the growing single crystal is followed by obtaining an initial lithium hydride single crystal. After the initial lithium hydride single crystal is obtained, the method preferably further comprises the steps of cooling the initial lithium hydride single crystal to a third temperature for third heat preservation, wherein the third temperature is 550-600 ℃, the third heat preservation time is 6-12 h, and the cooling rate of cooling to the third temperature is 1-4 ℃/h.
In the present invention, the third temperature is preferably 550 to 600 ℃, and particularly preferably 550 ℃ or 600 ℃.
In the present invention, the time of the third incubation is preferably 6 to 12 hours, more preferably 6 to 8 hours.
The cooling rate of the initial lithium hydride single crystal from the temperature to the third temperature is preferably 1 to 4 ℃/h, and more preferably 1.5 to 3 ℃/h.
According to the invention, the initial lithium hydride single crystal is preferably cooled to the third temperature and subjected to third heat preservation, so that the thermal stress in the initial lithium hydride single crystal can be eliminated, and the quality of the lithium hydride single crystal can be improved.
In the invention, after the third heat preservation, the lithium hydride single crystal obtained after the third heat preservation is cooled to room temperature.
In the invention, after the temperature is reduced to room temperature, the heating container is preferably disassembled in a low-oxygen and low-humidity glove box to obtain the lithium hydride single crystal product.
The invention provides a single crystal growth device used in the preparation method of the technical scheme, which comprises the following steps:
a furnace body 5;
the furnace body moving system 6 is connected with the furnace body 5, and the furnace body moving system 6 is used for controlling the furnace body 5 to move along the axial direction;
a lower-region heating element 4 and an upper-region heating element 3 which are fixedly connected with the inner wall of the furnace body 5 from bottom to top, wherein the lower-region heating element 4 and the upper-region heating element 3 are independently controlled to heat, the lower-region heating element 4 forms a lower chamber, the upper-region heating element 3 forms an upper chamber, and the lower chamber is communicated with the upper chamber;
a water-cooled crucible 8 disposed in the lower chamber;
a single crystal growth vessel 1 disposed in the upper chamber;
the single crystal growth container 1 is provided with a gas inlet and outlet conduit 9;
a sample crucible 2 disposed in the single crystal growth vessel 1.
The single crystal growth device provided by the invention comprises a furnace body 5.
As a specific embodiment of the invention, through holes are arranged on the side wall of the furnace body 5, and the through holes are used for inserting the first thermocouple 7-1 and the second thermocouple 7-2.
As a specific embodiment of the present invention, the furnace body 5 is ring-shaped.
The single crystal growth device provided by the invention comprises a furnace body moving system 6 connected with the furnace body 5, wherein the furnace body moving system 6 is used for controlling the furnace body 5 to move along the axial direction.
As a specific embodiment of the present invention, the connection is a fixed connection.
As an embodiment of the present invention, the furnace moving system 6 is fixedly connected to the top section of the furnace body 5.
The single crystal growth device provided by the invention comprises a lower-region heating element 4 and an upper-region heating element 3 which are fixedly connected with the inner wall of a furnace body 5 from bottom to top.
In the invention, the lower region heating element 4 and the upper region heating element 3 are independently controlled to heat.
As one specific example of the present invention, the lower region heating element 4 is a ring-shaped heating element.
In an embodiment of the present invention, the bottom cross section of the lower region heating element 4 is equal in height to the bottom cross section of the furnace body 5.
As one embodiment of the present invention, the upper zone heating element 3 is a ring-shaped heating element.
In one embodiment of the present invention, the top cross section of the upper zone heating element 3 is the same height as the top cross section of the furnace body 5.
As a specific embodiment of the present invention, a through hole is provided on the side wall of the upper zone heating element 3, and the through hole is used for fixedly connecting the first thermocouple 7-1 and the second thermocouple 7-2.
As an embodiment of the present invention, the lower region heating element 4 and the upper ring-shaped heating element 3 are equal in height.
As a specific embodiment of the present invention, a through hole is provided in a side wall of the lower region heating element 4, and the through hole is used for fixedly connecting the first thermocouple 7-1 and the second thermocouple 7-2.
In the invention, the lower region heating element 4 forms a lower chamber, the upper region heating element 3 forms an upper chamber, and the lower chamber is communicated with the upper chamber.
The single crystal growing apparatus provided by the present invention comprises a water-cooled crucible 8 disposed in the lower chamber.
As an embodiment of the present invention, the height of the water-cooled crucible 8 is larger than the height of the lower region heating element 4.
In an embodiment of the present invention, the water-cooled crucible 8 is made of copper.
As a specific embodiment of the invention, the bottom of the side wall of the water-cooled crucible 8 is provided with a water inlet pipe and a water outlet pipe, and the water inlet pipe and the water outlet pipe are positioned outside the furnace body 5.
As an embodiment of the invention, the top cover of the water-cooled crucible 8 is concave to form a conical tip, and the conical angle of the conical tip is preferably 30-60 degrees.
The single crystal growing device comprises a single crystal growing container 1 arranged in the upper chamber, wherein the single crystal growing container 1 is provided with a gas inlet and outlet conduit 9.
As an embodiment of the present invention, the gas inlet/outlet conduit 9 is provided on the ceiling of the single crystal growth vessel 1. And the gas inlet and outlet are used for vacuumizing and introducing gas into the single crystal growth container 1.
As a specific example of the present invention, the height of the single crystal growth vessel 1 is larger than that of the upper zone heating element 3.
As an embodiment of the present invention, the bottom surface of the single crystal growth vessel 1 is convex to form a conical tip, and the conical angle of the conical tip is preferably 30 to 60 degrees.
As an embodiment of the present invention, the conical tip formed by the bottom surface of the single crystal growth vessel 1 protruding outward is engaged with the conical tip formed by the top cover of the water-cooled crucible 8 being recessed inward.
In one embodiment of the present invention, the material of the single crystal growth vessel 1 is stainless steel.
As a specific embodiment of the present invention, the single crystal growth vessel 1 is a detachably sealed growth vessel.
The single crystal growth apparatus provided by the present invention includes a sample crucible 2 disposed in the single crystal growth vessel 1.
As an embodiment of the present invention, the bottom surface of the sample crucible 2 is protruded to form a conical tip, and the conical angle of the conical tip is preferably 30 to 60 degrees.
As an embodiment of the present invention, the conical tip end of the bottom surface of the sample crucible 2 formed convexly fits with the conical tip end of the bottom surface of the single crystal growth vessel 1 formed convexly.
In one embodiment of the present invention, the sample crucible 2 is made of iron.
The single crystal growth apparatus according to the present invention preferably further includes a first thermocouple 7-1 fixedly connected to the lower zone heating element 4.
As an embodiment of the present invention, the first thermocouple 7-1 is used to detect the temperature of the lower region heating element 4.
As a specific example of the present invention, the second thermocouple 7-2 is used for detecting the temperature of the upper zone heating element 3.
The specific implementation process of the invention for preparing lithium hydride by using the single crystal growth device is preferably as follows: lithium hydride is charged into the sample crucible 2 in a low-oxygen and low-humidity glove box, and then the sample crucible 2 is charged into the single crystal growth vessel 1. The stainless steel single crystal growth container 1 is vacuumized through the gas inlet and outlet conduit 9, then is cleaned by filling argon, and is repeated for three times. And vacuumizing the single crystal growth container 1, filling hydrogen, repeatedly filling hydrogen into the single crystal growth container 1 for three times, and sealing the single crystal growth container 1 after the hydrogen pressure is 0.15-0.3 MPa. The single crystal growth container 1 is arranged in an upper cavity formed by an upper-area heating body 3 in a furnace body 5, a water-cooled crucible 8 is arranged in a lower cavity formed by a lower heating body 4 in the furnace body 5, and a conical tip on the bottom surface of the single crystal growth container 1 is matched with an inwards concave conical tip formed by a top cover of the water-cooled copper crucible 8. Heating the upper zone heating element 3 and the lower zone heating element 4 to 740-760 ℃ simultaneously, and keeping the temperature for 12-24 h to fully melt the lithium hydride raw material. The temperature of the upper zone heating element 3 is reduced to 685-700 ℃, the temperature of the lower zone heating element 4 is reduced to 620-640 ℃, after heat preservation is carried out for 2 hours, the furnace body 5 moves upwards along the axis through the furnace body moving system 6, and the moving speed is 1-10 mm/h. When the sample crucible 2 is positioned in the lower chamber formed by the lower zone heating element 4, the furnace body moving system 6 stops moving, the lower zone heating element 4 is slowly cooled to 550-600 ℃, and the temperature is kept for 6-10 h and then is slowly cooled to the room temperature. In the above process, flowing cold water is always introduced into the water-cooled crucible 8, and the temperature of the cold water is 20-40 ℃. And cooling to room temperature, disassembling the stainless steel single crystal growth container 1 in a low-oxygen low-humidity glove box, taking out the pure iron crucible 2, inverting the pure iron crucible, and tapping the pure iron crucible to obtain a lithium hydride single crystal rod product.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.
Example 1
Lithium hydride rod material with a diameter of 24mm, a length of 100mm and a purity of 99.0% was charged into a pure iron crucible 2 in a low oxygen and low humidity glove box. Then the crucible 2 is placed into a detachable sealed stainless steel single crystal growth container 1. The bottom surface end of the pure iron crucible 2 and the bottom surface of the single crystal growth container 1 are conical tips of 60 degrees and are matched with the concave conical tips at the upper end of the water-cooled copper crucible 8.
Vacuumizing the stainless steel single crystal growth container 1, filling argon gas for cleaning, and repeating for three times. Then the stainless steel single crystal growth container 1 is vacuumized and filled with high-purity hydrogen, and the process is repeated for three times. The hydrogen is purified by a ZrCo chemical bed and has the purity of 99.999 percent; after the last hydrogen cleaning, the hydrogen pressure in the stainless steel single crystal growth container is 0.3MPa.
The part of the single crystal growth container 1 where the pure iron crucible 2 is located is placed in an upper cavity formed by an upper zone heating element 3, the upper zone heating element 3 and a lower zone heating element 4 are heated to 740 ℃ at the speed of 100 ℃/h simultaneously, the temperature is kept for 24h, after lithium hydride raw materials are fully melted and layered and purified, the upper zone heating element 3 is cooled to 690 ℃ at the speed of 10 ℃/h, the lower zone heating element 4 is cooled to 620 ℃ at the speed of 10 ℃/h, the temperature is kept for 2h, and then a furnace body 5 is slowly lifted along the axial direction by a furnace body moving system 6, and the lifting speed is 1mm/h. The hydrogen pressure in the single crystal growth vessel 1 was maintained at 0.3MPa, and the temperature gradient of the lithium hydride liquid at the liquid phase interface (expressed as the temperature gradient of the single crystal growth vessel 1) at the time of growing a single crystal was 10 ℃/cm. When the upper parts of the pure iron crucibles are all positioned in a lower chamber formed by the lower-region heating element 4, the furnace body moving system 6 stops moving, the lower-region heating element 4 is heated to 600 ℃ at the speed of 1 ℃/h, and the temperature is kept for 6h and then is slowly cooled to the room temperature. The stainless steel single crystal growth container 1 is disassembled in the low-oxygen low-humidity glove box, the pure iron crucible is taken out and inverted, and the pure iron crucible is tapped to obtain the lithium hydride single crystal rod. The purity of the lithium hydride single crystal rod was 99.5%, the cleaved single crystal piece was translucent and the physical pattern was as shown in FIG. 2, and the X-ray diffraction pattern of the lithium hydride single crystal prepared in this example was as shown in FIG. 3, and the X-ray diffraction peaks thereof were only (002) and (004), and the intensity of the diffraction peaks was high and sharp (FIG. 3), indicating that the single crystal quality was high.
Example 2
Lithium hydride rod material with a diameter of 24mm, a length of 100mm and a purity of 99.2% was charged into a pure iron crucible 2 in a low oxygen and low humidity glove box. Then the crucible 2 is placed into a detachable sealed stainless steel single crystal growth container 1. The bottom surface end of the pure iron crucible 2 and the bottom surface of the single crystal growth container 1 are conical tips of 30 degrees and are matched with the concave conical tips at the upper end of the water-cooled copper crucible 8.
Vacuumizing the stainless steel single crystal growth container 1, filling argon, cleaning and repeating for three times. And then the stainless steel single crystal growth container 1 is vacuumized and filled with high-purity hydrogen for three times. The hydrogen is purified by a ZrCo chemical bed and has the purity of 99.999 percent; after the last hydrogen cleaning, the hydrogen pressure in the stainless steel single crystal growth container is 0.15MPa.
The part of the single crystal growth container 1 where the pure iron crucible 2 is located is placed in an annular upper chamber formed by an upper zone heating element 3, the upper zone heating element 3 and a lower zone heating element 4 are heated to 760 ℃ at the speed of 200 ℃/h simultaneously, the temperature is kept for 12h, lithium hydride raw materials are fully melted and layered and purified, the upper zone heating element 3 is cooled to 690 ℃ at the speed of 20 ℃/h, the lower zone heating element 4 is cooled to 620 ℃ at the speed of 20 ℃/h, the temperature is kept for 2h, a furnace body 5 is slowly lifted axially by a furnace body moving system 6, and the lifting speed is 1mm/h. The hydrogen pressure in the single crystal growth vessel 1 was maintained at 0.4MPa, and the temperature gradient of the lithium hydride liquid at the liquid phase interface (expressed as the temperature gradient of the single crystal growth vessel 1) at the time of growing a single crystal was 10 ℃/cm. When the upper parts of the pure iron crucibles are all positioned in a lower chamber formed by the lower zone heating elements 4, the furnace body moving system 6 stops moving, the lower zone heating elements 4 reach 550 ℃ at the speed of 1 ℃/h, and the temperature is kept for 10h and then is slowly reduced to the room temperature. The stainless steel single crystal growth container 1 is disassembled in the low-oxygen low-humidity glove box, the pure iron crucible is taken out and inverted, and the pure iron crucible is tapped to obtain the lithium hydride single crystal rod. The purity of the lithium hydride single crystal rod was 99.4%, the cleaved single crystal plate was translucent and its physical pattern was similar to that of FIG. 2, and the X-ray diffraction pattern of the lithium hydride single crystal prepared in this example was similar to that of FIG. 3, and the single crystal quality was high.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (3)
1. A method for preparing a lithium hydride single crystal is characterized by comprising the following steps:
growing a single crystal in a moving temperature field by liquid lithium hydride in an atmosphere of hydrogen; when the single crystal is grown, the temperature gradient of the liquid lithium hydride at the solid-liquid interface is 6-10 ℃/cm, and the moving temperature field is formed by moving a heating device; the heating device moves at a uniform speed, and the moving speed of the heating device is 1-10 mm/h; the pressure of the hydrogen is 0.15-0.4 MPa;
the preparation method of the liquid lithium hydride comprises the following steps:
in the atmosphere of hydrogen, heating lithium hydride to a first temperature by a heating device, and carrying out first heat preservation to obtain initial liquid lithium hydride, wherein the first temperature is 740-760 ℃, and the first heat preservation time is 12-24 h; the heating rate of heating from room temperature to the first temperature is 100-200 ℃/h;
in the atmosphere of hydrogen, establishing a gradient temperature field in the middle of the initial liquid lithium hydride by a heating device, and then carrying out second heat preservation, wherein the temperature gradient of the liquid lithium hydride from bottom to top after the gradient temperature field is established is 6-10 ℃/cm; the second heat preservation time is 1-3 h;
the growing single crystal directly results in an initial lithium hydride single crystal, further comprising: and cooling the initial lithium hydride single crystal to a third temperature, and carrying out third heat preservation, wherein the third temperature is 550-600 ℃, the third heat preservation time is 6-12 h, and the cooling rate of cooling to the third temperature is 1-4 ℃/h.
2. A single crystal growth apparatus used for the production method according to claim 1, comprising:
a furnace body (5);
the furnace body moving system (6) is connected with the furnace body (5), and the furnace body moving system (6) is used for controlling the furnace body (5) to move along the axial direction;
the lower-region heating element (4) and the upper-region heating element (3) are fixedly connected with the inner wall of the furnace body (5) from bottom to top, the lower-region heating element (4) and the upper-region heating element (3) are independently controlled to heat, the lower-region heating element (4) forms a lower cavity, the upper-region heating element (3) forms an upper cavity, and the lower cavity is communicated with the upper cavity;
a water-cooled crucible (8) disposed in the lower chamber;
a single crystal growth vessel (1) disposed in the upper chamber;
the single crystal growth container (1) is provided with a gas inlet and outlet conduit (9);
a sample container (2) disposed within the single crystal growth vessel (1).
3. The apparatus according to claim 2, further comprising a first thermocouple (7-1) fixedly connected to the lower region heating element (4);
and the second thermocouple (7-2) is fixedly connected with the upper zone heating element (3).
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