CN112195507B - Method for preparing rare earth metal single crystal - Google Patents

Abstract

The invention discloses a preparation method of a rare earth metal single crystal. The method comprises the following steps: installing a rare earth metal material rod in a three-electrode arc zone smelting furnace, wherein the rare earth metal is one of Sc, Lu, Er, Y, Gd, Tb, Dy, Ho and Tm; vacuumizing to below 1Pa, and filling argon to 5-80 kPa; heating the material rod, and after a melting zone appears, performing first zone melting on the material rod at a zone melting speed of 0.01-5 mm/min and a rotating speed of 0-20 r/min; stopping heating and cooling after the first zone melting is finished; and moving the charge bar to an initial position after the charge bar is cooled, and repeating zone melting once or for multiple times to obtain the rare earth metal single crystal. The method can prepare the rare earth metal single crystal with the size range phi of 4-12 mm, and has short preparation period and high yield.

Description

Method for preparing rare earth metal single crystal

Technical Field

The invention relates to the technical field of rare earth metal single crystal preparation, in particular to a preparation method of a rare earth metal single crystal.

Background

Rare earth elements have unique physical and chemical properties due to their special 4f electron shell structure. The rare earth metal monocrystal has anisotropic property, high density and no pores. At present, the method is mainly applied to the fields of reference materials, coating materials and the like in the research and development of metal materials, and has extremely high research value.

The main preparation method of the metal single crystal comprises the following steps: the vapor phase single crystal growth technology prepares a single crystal by a vapor deposition method, the single crystal has small size and many air holes, is easy to be bonded with the crucible wall, and easily causes strain to the single crystal during separation. The liquid single crystal growth technology comprises a zone melting method, a pulling method and a temperature gradient method for preparing single crystals, which easily causes crucible pollution, and has long preparation time, harsh process conditions and large investment. The recrystallization annealing method and the solid-state electromigration method in the solid-state single crystal growth technology have the problems that the size of a single crystal is small, generally 1mm or less, and the cutting of single crystal particles is difficult due to the limitation of the microscopic form of a matrix metal, and Chinese patent CN106222744A discloses a rare earth metal single crystal and a preparation method thereof, and particularly discloses that the rare earth metal single crystal is prepared by adopting a directional solidification ingot through repeated extrusion deformation and recrystallization annealing, so that the time consumption is long, the oxygen content is high, and the like.

Disclosure of Invention

Based on the problems, the invention aims to provide a method for preparing rare earth metal single crystals, the rare earth metal single crystals prepared by the method can be in a size range of phi 4-12 mm, the preparation period is short, and the yield is high.

The above purpose of the invention is realized by the following technical scheme:

according to one aspect of the present invention, there is provided a method for preparing a rare earth metal single crystal, comprising the steps of:

installing a rare earth metal material rod in a three-electrode arc zone smelting furnace, wherein the rare earth metal is one of Sc, Lu, Er, Y, Gd, Tb, Dy, Ho and Tm;

vacuumizing to below 1Pa, and filling argon to 5-80 kPa;

heating the material rod, and after a melting zone appears, performing first zone melting on the material rod at a zone melting speed of 0.01-5 mm/min and a rotating speed of 0-20 r/min;

and after the first zone melting is finished, stopping heating and cooling, moving the material rod to an initial position after the material rod is cooled, and repeating the zone melting for one time or multiple times to obtain the rare earth metal single crystal.

Further, the purity of the rare earth metal material rod is higher than 2N, and the diameter of the rare earth metal material rod is 4-12 mm.

Further, the diameter of the rare earth metal single crystal is 4-12 mm.

Further, the zone-melting speed can be 0.01-0.5 mm/min. The rotation speed can be 1-10 r/min.

Further, when the zone melting is repeated, the moving direction of the melting zone is the same as that of the first zone melting, and the moving speed may be the same as that of the first zone melting or may be increased or decreased based on the moving speed.

Furthermore, the currents of the three electrodes are the same and are 5-25A. Namely, the current of the three electrodes is kept consistent in the heating and temperature rising stage and the final heat preservation.

Further, in the present invention, the three-electrode arc zone melting furnace includes: the device comprises a base, a furnace body arranged on the base, a clamping device arranged in the furnace body and used for clamping and moving a material rod, and an electrode heating assembly used for heating the material rod, wherein the base is provided with an air suction hole and an air charging hole; the clamping device includes: the furnace body comprises a first lifting rod, a second lifting rod and a chuck, wherein the first lifting rod is arranged on the top of the furnace body; the electrode heating assembly comprises three electrodes which are installed on the furnace wall and can move along the transverse direction, and the electrodes are uniformly arranged on the periphery of the charge bar by taking the charge bar as the center.

Further, the step of installing the rare earth metal bar in a three electrode arc zone melting furnace includes: clamping the rare earth metal material rod at a chuck between the first lifting rod and the second lifting rod; adjusting the electrode heating assembly, and adjusting the tail ends of the three electrodes to the positions 1-6 mm away from the material rod.

Compared with the prior art, the preparation method of the rare earth metal single crystal is applicable to preparation of various rare earth metal single crystals, the size range of the prepared rare earth metal single crystal can be phi 4-12 mm, the preparation method has the advantages of short preparation period, only one day, several days or even dozens of days in the prior art and high yield.

Drawings

FIG. 1 is a schematic view of a three electrode arc zone melting furnace used in the present invention;

FIG. 2 is a schematic representation of the electrode position in a three electrode arc zone furnace for use with the present invention;

FIG. 3 is a photograph showing a high-purity scandium single crystal ingot obtained in example 1 of the present invention.

In the drawings 1-2, 1 furnace body, 2 base, 3 air exhaust holes, 4 air charging holes, 5 second lifting rods, 6 first lifting rods, 7 moving rods, 8 clamps, 9 chucks, 10 tungsten wires, 11 material rods and 12 sealing rings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

FIG. 1 shows schematically a configuration in a three electrode arc zone furnace for use with the present invention; figure 2 shows schematically the mounting positions of electrodes in a three electrode arc zone smelting furnace. As shown in fig. 1-2, the three-electrode arc zone melting furnace includes a base 2, a furnace body 1 mounted on the base 2, and a holding device and an electrode heating assembly mounted within the furnace body 1.

According to the invention, as shown in fig. 1, the base 2 is provided with an air exhaust hole 3 for vacuumizing the interior of the furnace body 1 to form a vacuum chamber in the furnace body 1; the base 2 is further provided with an air charging hole 4 for charging inert gas, such as high-purity argon with a purity of 99.99%, into the furnace body 1 as protective gas. Wherein, the size of the base 2 is preferably larger than that of the furnace body 1.

The gripping means is used to grip and move the material bar 11. As shown in fig. 1, the clamping device may include: a first lifting rod 6 located above, a second lifting rod 5 located below, and two chucks 9. The first lifting rod 6 and the second lifting rod 5 can move along the longitudinal direction so as to finish the up-and-down movement of the material bar 11 in the zone melting process. Specifically, the two lifting rods can be driven to move up and down by a first driving device which is arranged outside the furnace body 1 and is respectively connected with the first lifting rod 6 and the second lifting rod 5, so that the clamping of the material rod 11 is completed, and the material rod 11 in the zone melting stage can move up and down in the vertical direction. Further, the first lifting rod 6 is installed on the top of the furnace body 1, the second lifting rod 5 is installed on the base 2, and the specific installation mode of the two lifting rods is not limited. For example, the furnace body 1 and the base 2 may be provided with holes, and the first lifting rod 6 and the second lifting rod 5 may be vertically movably mounted in the holes. The first lifting rod 6 and the second lifting rod 5 are correspondingly arranged up and down to better clamp the material rod 11. The first lifting rod 6 and the second lifting rod 5 are preferably arranged on the central axis of the furnace body 1. The clamping head 9 is arranged at the end part of the first lifting rod 6 and the second lifting rod 5 which are opposite, namely one end of the lifting rod clamping the material rod 11. Preferably, sealing rings 12 are arranged at the mounting positions of the first lifting rod 6 and the top of the furnace body 1 and the mounting positions of the second lifting rod 5 and the base 2, so as to ensure the sealing performance in the furnace. The structure of the chuck 9 is not particularly limited, and the chuck can clamp the material bar 11 to realize the function of fixing the material bar 11.

In an alternative embodiment, the first lifting rod 6 and the second lifting rod 5 in the present invention can also rotate, that is, the first lifting rod 6 and the second lifting rod 5 can be respectively and vertically movable and can be rotatably installed on the top of the furnace body 1 and the base 2. For example, a third driving device disposed outside the furnace body 1 and connected to the first lifting rod 6 and the second lifting rod 5 respectively may be used to drive the rotation thereof, so as to rotate the clamped material rod 11. The third driving device may be, for example, a motor, as long as the third driving device can drive the two lifting rods to rotate.

The electrode heating assembly is used for heating the material rod 11. The electrode heating assembly comprises three electrodes which are uniformly installed on the furnace wall and can move along the transverse direction, the electrodes are uniformly and annularly arranged on the periphery of the charge bar 11 by taking the charge bar 11 as the center, namely, the included angle between the adjacent electrodes is 120 degrees so as to ensure the zone melting uniformity. As shown in fig. 1 and 2, the electrode may include: a moving rod 7 mounted on the wall of the furnace body 1, a clamp 8 connected to one end of the moving rod 7, and a tungsten filament 10 (of course, the tungsten filament is not limited to the tungsten filament, and may be made of other materials in the art) mounted on the clamp 8; the structure of the clamp 8 is not particularly limited, and for example, the clamp may have the same structure as the collet 9, so as to perform a clamping and fixing function, so that the center of the tungsten filament 10 is centered with the center of the collet 9. In the present invention, the electrodes are preferably arranged in a horizontal arrangement as shown in fig. 1, but not limited thereto, and may be arranged in a downward or upward inclined angle to ensure that the ends of the electrodes for heating are on the same horizontal plane. Preferably, a sealing ring 12 may be provided at the installation position of the moving rod 7 with the wall of the furnace body 1 to further ensure the sealing inside the furnace. In particular, the electrode heating assembly may be driven to move laterally by a second driving device connected thereto, which is disposed outside the furnace body 1. Further, the second driving device is connected with the other end of the moving rod 7, so that the moving rod 7 is driven to drive the integral electrode to move in the transverse direction, and the distance between the electrode and the material rod 11 is adjusted.

It should be noted that the first driving device and the second driving device may be a hydraulic cylinder, a motor, and the like, and are not limited specifically, and the two lifting rods may move up and down and the electrodes may move transversely. In addition, the first driving device and the third driving device can also be the same device, the device can control the up-down movement of the lifting rod and can also complete the rotation function of the lifting rod, the specific principle is not repeated, the device is the prior art, and the device can realize the multiple functions. In the invention, all the driving devices can be controlled by the same controller, and even all the driving devices can be controlled by an integrated multifunctional device to complete all the functions of all the driving devices.

It should be noted that, of course, the present invention also includes other devices such as an electronic control device, for example, controlling the on-state of the electrode heating assembly, the current of each electrode, the zone melting temperature, the connection mode of the positive electrode and the negative electrode, etc. all can be common technologies in the art, and are not described in detail herein.

The rare earth metal single crystal of the present invention is prepared by arc zone melting using the above-described three-electrode arc zone melting furnace, and the method for preparing the rare earth metal single crystal of the present invention is described in detail below:

and step S1, mounting the rare earth metal material rod in a three-electrode arc area smelting furnace. Specifically, a rare earth metal bar is firstly arranged at a chuck 9 between a first lifting rod 6 and a second lifting rod 5 and is clamped and fixed; then, the tail ends of three electrodes in the electrode heating assembly are adjusted to be 1-6 mm away from the material rod 11. Wherein the rare earth metal is one of Sc, Lu, Er, Y, Gd, Tb, Dy, Ho and Tm. The purity of the rare earth metal material rod is higher than 2N, and the diameter of the rare earth metal material rod is 4-12 mm.

Step S2, vacuumizing the three-electrode arc area smelting furnace to below 1Pa from the extraction hole 3 of the base 2, and filling argon to 5-80 kPa from the inflation hole 4 of the base 3;

and S3, heating the material rod 11, and after a melting zone appears, performing first zone melting on the material rod 11 at a zone melting speed (namely, an up-down moving speed) of 0.01-5 mm/min and a rotating speed of 0-20 r/min. The three electrodes always keep the current consistent during the whole temperature rise heating and the final heat preservation, and the current can be 5-25A. Furthermore, the zone-melting speed can be 0.3-0.5 mm/min, and the rotating speed can be 1-10 r/min.

And step S4, after the first zone melting is finished, stopping heating, cooling the material rod 11, moving the material rod 11 to the initial position after the material rod 11 is cooled, and repeating the zone melting for one or more times to obtain the rare earth metal single crystal. Wherein the diameter of the rare earth metal single crystal is 4-12 mm. When zone melting is repeated, the moving direction of the melting zone is unchanged, and the moving speed is greater than, less than or equal to that of the first zone melting.

The invention is described in detail below with specific examples:

example 1

A metal scandium material rod with the purity of 3N and the diameter of 8mm is selected as a raw material.

And fixing a metal scandium material rod 11 at a chuck 9 between an upper lifting rod and a lower lifting rod, and then adjusting the distance between the tail ends of the three electrodes and the material rod 11 to be 4 mm.

Vacuumizing to below 1pa, and then filling high-purity argon to 50 KPa.

And starting heating, wherein the three electrodes are respectively started to ensure the current to be consistent, and the current is 12A during heat preservation.

After the melting zone is stabilized, the motor is started to perform the first melting zone at the (upward) melting zone speed of 0.5mm/min and the rotating speed of 4 r/min.

After zone melting is finished, the heating is turned off, and the material rod 11 is cooled.

After the material rod 11 is cooled, the material rod 11 is moved to an initial position, the moving speed of the upper lifting rod and the lower lifting rod is changed to be upward 0.3mm/min, and the zone melting process is repeated once, so that the scandium metal single crystal with the diameter of phi 8mm can be obtained.

Example 2

Selecting a metal lutetium material rod with the purity of 3N and the diameter of 8mm as a raw material.

The metal lutetium material rod 11 is fixed at the position of the chuck 9 between the upper lifting rod and the lower lifting rod, and then the distance between the tail ends of the three electrodes and the material rod 11 is adjusted to be 3.5 mm.

Vacuumizing to below 1pa, and then filling high-purity argon to 30 kPa.

And starting heating, respectively starting the three electrodes and ensuring the current to be consistent, wherein the current is 13A during heat preservation.

After the melting zone is stabilized, the motor is started to perform the first zone melting at the zone melting speed of 0.3mm/min and the rotating speed of 6 r/min.

After zone melting is finished, the heating is turned off, and the material rod 11 is cooled.

After the material bar 11 is cooled, the material bar 11 is moved to the initial position, the zone melting process is repeated once, the moving direction of the melting zone is unchanged, and the speed is the same as the first zone melting speed, so that the metal lutetium monocrystal with the diameter of phi 8mm can be obtained.

Example 3

Selecting a metal dysprosium material rod with the purity of 3N and the diameter of 6mm as a raw material.

Fixing the metal dysprosium material rod 11 at the position of the chuck 9 between the upper lifting rod and the lower lifting rod, and then adjusting the distance between the tail ends of the three electrodes and the material rod 11 to be 3 mm.

Vacuumizing to below 1pa, and then filling high-purity argon to 30 KPa.

And starting heating, respectively starting the three electrodes, ensuring the current to be consistent, and keeping the current to be 7.5A during heat preservation.

After the melting zone is stabilized, the motor is started to perform the first zone melting at the zone melting speed of 0.4mm/min and the rotating speed of 8 r/min.

After zone melting is finished, the heating is turned off, and the material rod 11 is cooled.

After the material bar 11 is cooled, the material bar 11 is moved to the initial position, the moving speed of the upper lifting rod and the lower lifting rod is changed to be upward 0.3mm/min, and the zone melting process is repeated once, so that the metal dysprosium single crystal with the phi of 6mm can be obtained.

The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to practitioners skilled in this art. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims (4)

1. A method for preparing a rare earth metal single crystal is characterized by comprising the following steps:

installing a rare earth metal material rod in a three-electrode arc zone smelting furnace, wherein the rare earth metal is one of Sc, Lu, Er, Y, Gd, Tb, Dy, Ho and Tm; the purity of the rare earth metal material rod is higher than 2N, and the diameter of the rare earth metal material rod is 4-12 mm;

vacuumizing to below 1Pa, and filling argon to 5-80 kPa;

heating the material bar, and after a melting zone appears, performing first zone melting on the material bar at a zone melting speed of 0.01-0.5 mm/min and a rotating speed of 1-20 r/min;

stopping heating and cooling after the first zone melting is finished, moving the material rod to an initial position after the material rod is cooled, and repeating the zone melting for one or more times to obtain a rare earth metal single crystal, wherein the diameter of the rare earth metal single crystal is 4-12 mm;

wherein the three electrode arc zone melting furnace comprises: the device comprises a base, a furnace body arranged on the base, a clamping device arranged in the furnace body and used for clamping and moving a material rod, and an electrode heating assembly used for heating the material rod; the clamping device includes: the furnace body comprises a first lifting rod arranged on the top of the furnace body and a second lifting rod arranged on the base and opposite to the first lifting rod, wherein the first lifting rod and the second lifting rod can move up and down and rotate along the longitudinal direction; the electrode heating assembly comprises three electrodes which are arranged on the furnace wall and can move along the transverse direction, and the electrodes are uniformly arranged on the periphery of the charge bar by taking the charge bar as the center; wherein the currents of the three electrodes are the same and are 5-25A; during installation, the tail ends of the three electrodes are adjusted to be 1-6 mm away from the material rod.

2. The method for producing a rare earth metal single crystal according to claim 1, wherein the rotation speed is 1 to 10 r/min.

3. The method of producing a rare earth metal single crystal according to claim 1, wherein the moving direction is the same as that of the first time when the floating zone melting is repeated.

4. The method of producing a rare earth metal single crystal according to claim 1,

the base is provided with an air exhaust hole and an air inflation hole;

the clamping device further comprises: a collet mounted at opposite ends of the first and second lift rods.

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