Method for preparing single crystal by using high-flux chemical vapor transport method

Abstract

The invention provides a method for preparing single crystals by using a high-flux chemical vapor transport method, which comprises the following steps: independently arranging different raw materials in a raw material area of a quartz tube, respectively adding a transport agent into each raw material, and vacuumizing and sealing the quartz tube; heating the quartz tube in a heating furnace, respectively setting the heating temperatures of the raw material area and the crystallization area to form different temperature gradients, reacting the heated raw materials with the transport agent to generate a gaseous compound, carrying out a free reaction between the raw materials, moving from a high-temperature area to a low-temperature area under the action of the temperature gradients, and carrying out crystallization on the gaseous compound; and crystal growth is carried out in different temperature regions. The method is simple to operate, single crystals with different proportions can be grown through one experiment, the difference of growth conditions caused by human factors in the experiment process is effectively reduced, the experiment technology is greatly optimized, the experiment period is shortened, and the method has important significance on element doping and phase diagram construction.

Description

Technical Field

[0001] The present invention belongs to the field of preparing single crystals by high-throughput chemical vapor transport method, and specifically combines the high-throughput experimental method with the chemical vapor transport method to accelerate the research process of single crystal growth. Background Art

[0002] Single crystal materials have regular surface shapes due to their long-range order and periodicity of spatial arrangement. They play an important role in in-depth research on the physical properties of materials and revealing their intrinsic properties and physical laws. Obtaining high-quality single crystals is the first step in studying condensed matter physics. The basic principle of growth is to fully mix and heat the raw materials, break old bonds and generate new bonds through chemical reactions between atoms, and form long-range ordered single crystals. At present, commonly used crystal growth methods include solid-phase reaction method, co-solvent method, chemical vapor transport method, Bridgman method, etc.

[0003] Chemical Vapor Transport (CVT) is a method of growing crystals by using chemical reversible reactions to react in different directions at different temperatures. The basic principle of chemical vapor transport is that reactants react with transport agents at a certain temperature to form gas phase products, which react inversely at different temperature gradients in the system, grow in the crystallization zone, and stack and deposit. The experimental principle diagram is shown in the attached Figure 1 As shown. This method has the characteristics of simple equipment, low growth temperature, and high single crystal quality. The synthesized single crystals are almost defect-free. In the experiment, the mass transport rate can be controlled by adjusting the mass, temperature, and temperature gradient of the transport agent. Usually, an experiment takes two to four weeks, and the experimental cycle is relatively long.

[0004] High-throughput technology is a technology that can quickly and efficiently obtain a large amount of experimental data. It is widely used in material preparation and testing, and is of great significance for accelerating material research and development and improving experimental efficiency. At present, there have been many reports at home and abroad, such as patent CN111254484A discloses a high-throughput single crystal growth device, based on the Bridgman single crystal growth method, and improves the stepper motor device to achieve high-throughput single crystal growth; patent CN105624774A discloses a method for obtaining inorganic material single crystals with continuously changing components, using non-continuous component polycrystals as raw materials and using the optical floating zone method to obtain single crystals with continuously changing components, which provides the possibility for high-throughput material characterization analysis and optimal selection. Summary of the invention

[0005] In order to solve the problems of long cycle, repetitive and single experiments in the existing chemical vapor transport method for growing single crystals, the present invention provides a high-throughput method for preparing single crystals with simple operation, simple device and more components. In the traditional gas phase transport method, only a uniformly mixed powder or polycrystalline powder of one component is placed in the raw material area, and only a specific proportion of intermediate products are generated during the gas phase transport process, and crystals grow in the crystallization area. The present invention uses a high-throughput gas phase transport method to separate the raw materials in the raw material area, and then heats up to allow the raw materials to react with the transport agent to generate gaseous compounds, and allows the raw materials to react freely with the raw materials, move from the high temperature to the low temperature area under the action of the temperature gradient, and crystallize and grow in different temperature areas. The present invention combines the traditional crystal growth method with high-throughput experimental technology, changes the traditional trial and error method, obtains the effect of multiple experiments in one experiment, can quickly generate a variety of single crystal materials, accelerate the discovery and optimization of new materials, and significantly improve research efficiency.

[0006] The present invention adopts the following technical solutions: A method for preparing single crystals by using a high-throughput chemical vapor transport method comprises the following steps: different raw materials are separately arranged in a raw material area of ​​a quartz tube, a transport agent is added to each raw material, and the quartz tube is evacuated and sealed; then the quartz tube is placed in a heating furnace for heating, and the heating temperatures of the raw material area and the crystallization area are respectively set to form different temperature gradients. After the temperature is raised, the raw materials react with the transport agent to generate gaseous compounds, and then the raw materials react freely with each other, move from a high temperature area to a low temperature area under the action of the temperature gradient, and crystallize and grow in different temperature areas.

[0007] Furthermore, different raw materials are placed in small glass tubes with one end open respectively so that different raw materials are separately arranged in the raw material area of ​​the quartz tube.

[0008] Furthermore, the water and oxygen contents in the sealed quartz tube are controlled below 0.1 ppm.

[0009] Furthermore, the method is used to prepare Fe-Ge series single crystals, comprising the following steps: placing iron powder and germanium powder in small glass tubes with an opening at one end, adding iodine as a transport agent in each small glass tube, evacuating the quartz tube and sealing it; then placing the quartz tube in a heating furnace for heating, setting the temperature of the raw material area to 600-1100°C, the temperature of the crystallization area to 500-1000°C, and the growth time to 7-21 days, so that FeGe with different proportions can be obtained. x Single crystal; the temperature of the crystallization region is lower than the temperature of the raw material region.

[0010] Furthermore, the temperature of the raw material region was set to 600° C., the temperature of the crystallization region was set to 500° C., and the growth time was 14 days.

[0011] Furthermore, the method obtains six ratios of FeGe x Single crystal, respectively FeGe 0.60 ,FeGe 0.66 ,FeGe 0.73 , single FeGe 0.78 ,FeGe 0.81 andFeGe 0.84 .

[0012] Furthermore, the mass ratio of the iron powder to the germanium powder is 1:1.

[0013] Furthermore, the amount of the transport agent added is 0.5 g / cm 3 The total amount of transport agent added is calculated as 0.5g / cm 3 Multiply by the volume sealed inside the quartz tube.

[0014] Furthermore, the transport agent is divided into two equal parts and added into two small glass tubes respectively.

[0015] Furthermore, the heating furnace is a double-temperature zone furnace.

[0016] Furthermore, the inner diameter of the quartz tube is 1.5 cm, the thickness is 1.5 mm, and the length is 35 cm, and the inner diameter of the small glass tube is 0.5 cm and the length is 2 cm. A glass tube with a larger diameter and a longer length can also be used as a reaction container, which can provide the reactants with a larger space and a longer temperature change range, promote the generation of gaseous intermediate products, and facilitate the transportation of gases and the growth of single crystals during the reaction process.

[0017] Compared with the prior art, the present invention has the following technical effects: 1. In the traditional gas phase transport method, only one component of uniformly mixed powder or polycrystalline powder is placed in the raw material area, and only a specific proportion of intermediate products are generated during the gas phase transport process, and crystals grow in the crystallization area. The present invention uses a high-throughput gas phase transport method to separate the raw materials in the raw material area, raise the temperature to allow the raw materials to react with the transport agent to generate gaseous compounds, and allow the raw materials to react freely with each other, move from the high temperature area to the low temperature area under the action of the temperature gradient, and crystallize and grow in different temperature areas. The single crystals grown by the present invention are of good quality and can meet the test requirements.

[0018] 2. The present invention discloses a method for preparing single crystals by using high-throughput chemical vapor transport. The method is simple to operate and can grow single crystals of different proportions in one experiment, effectively reducing the differences in growth conditions caused by human factors during the experiment, greatly optimizing the experimental technology and shortening the experimental cycle, which is of great significance for element doping and the construction of phase diagrams. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the experimental principle of the chemical vapor transport method in the prior art; Figure 2 It is a schematic diagram of the experimental principle of a method for preparing single crystals by using a high-throughput chemical vapor transport method according to the present invention; Figure 3 is a diagram of the growth result using the high-throughput chemical vapor transport method according to Example 1 of the present invention; Figure 4 The different proportions of FeGe prepared in Example 1 of the present invention x Optical images of single crystals; Figure 5 The different proportions of FeGe prepared in Example 1 of the present invention x SEM image and X-ray spectrum of single crystal; Figure 6 The different proportions of FeGe prepared in Example 1 of the present invention x The resistance curve of a single crystal changes with temperature; Figure 7 The different proportions of FeGe prepared in Example 1 of the present invention x Normalized resistance of a single crystal R(T) / R 300 K Curves changing with temperature; Figure 8 1 is a test result diagram of Comparative Example 1 of the present invention; Fig. 9 It is a test result diagram of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0021] The heating furnace used in the following examples is a dual-temperature zone furnace, model OTF-1200X-Ⅱ, with a maximum heating rate of 20°C / min, a maximum operating temperature of 1200°C, and a constant temperature accuracy of ±1°C.

[0022] Example 1 A method for preparing Fe-Ge series single crystals by high-throughput chemical vapor transport method comprises the following steps: Step 1: First, prepare the quartz tube and two small glass tubes required for the experiment, clean them with alcohol ultrasonic cleaning and dry them in an oven. The quartz tube used in this embodiment has an inner diameter of 1.5 cm, a wall thickness of 1.5 mm, and a length of 35 cm. One end of the small glass tube is open, and the inner diameter of the small glass tube is 0.5 cm and the length is 2 cm.

[0023] Step 2: In a glove box filled with argon, weigh 0.5 g of high-purity iron powder (Aladdin, purity 99.99%) and 0.5 g of germanium powder (Aladdin, purity 99.999%), and place them in small glass tubes. In this example, iodine particles are added as a transport agent, and the amount of the transport agent added is 0.5 g / cm 3 The transport agent is evenly divided into two equal parts and added into two small glass tubes respectively, with the open ends of the two small glass tubes facing the crystallization area.

[0024] Step 3: Place two small glass tubes in the quartz tube in sequence, and place a quartz column 25 cm from the quartz tube to seal the quartz tube.

[0025] Step 4: Use a hydrogen-oxygen flame tube sealing device to fuse the quartz column and glass tube in step 3 to complete the sealing, so that the water and oxygen content in the quartz tube is controlled below 0.1 ppm.

[0026] Step 5: Place the sealed quartz tube in a dual-temperature zone sintering furnace, and align the raw material area and the crystallization area (also called the product area) with the two thermocouples to make the temperature control more accurate. The temperature of the raw material area is set to 600 °C, the temperature of the crystallization area is set to 500 °C, and the growth time is set to two weeks. After sintering, take out the small glass tube. Six ratios of FeGe x Single crystal, respectively FeGe 0.60 ,FeGe 0.66 ,FeGe 0.73 , single FeGe 0.78 ,FeGe 0.81 andFeGe 0.84 .

[0027] Results: Single crystal accumulation was found in different areas of the quartz tube, see Figure 3 , the single crystal shapes of different parts are slightly different, see Figure 4 , energy dispersive X-ray spectroscopy (EDS) determined that there are six different ratios, see Figure 5 .like Figure 6 and Figure 7 As shown, after testing the change of resistance with temperature, it can be seen that the crystals in the six proportions all behave like metals, and the residual resistance ratio is between 1-3. The sample quality can meet the test requirements.

[0028] Comparative Example 1 The method for preparing FeGe single crystal comprises the following steps: Step 1: First, prepare the quartz tube required for the experiment, clean it with alcohol ultrasonic cleaning and dry it in an oven. The quartz tube used in this comparative example has an inner diameter of 1.5 cm, a wall thickness of 1.5 mm, and a length of 35 cm.

[0029] Step 2: In a glove box filled with argon, weigh high-purity iron powder (Aladdin, purity 99.99%) and germanium powder (Aladdin, purity 99.999%) in a molar ratio of 1:1, mix well and place at the bottom of the quartz tube. Add iodine particles as a transport agent, and the amount of the transport agent added is 0.5 g / cm 3 .

[0030] Step 3: Place a quartz column 25 cm from the quartz tube to seal the quartz tube.

[0031] Step 4: Use a hydrogen-oxygen flame tube sealing device to fuse the quartz column and glass tube in step 3 to complete the sealing, so that the water and oxygen content in the quartz tube is controlled below 0.1 ppm.

[0032] Step 5: Place the sealed quartz tube in a dual-temperature zone sintering furnace, and align the raw material area and the crystallization area (also called the product area) with the two thermocouples to make the temperature control more accurate. The temperature of the raw material area is set to 600 ℃, the temperature of the crystallization area is set to 500 ℃, and the growth time is set to two weeks. After sintering, the grown single crystals are all FeGe. See the results. Figure 8 .

[0033] Comparative Example 2 The steps are basically the same as those in Comparative Example 1, except that the iron powder and germanium powder are prepared in a molar ratio of 2:3. The single crystals grown in the end are all Fe2Ge3. Fig. 9 .

[0034] The present invention can be improved in the following aspects: (1) A glass tube with a larger diameter and longer length can be used as a reaction container. This can provide the reactants with a larger space and a longer temperature change range, promote the generation of gaseous intermediates, and facilitate gas transport and single crystal growth during the reaction.

[0035] (2) Depending on the target product, you can try placing three or even more small glass tubes, placing different raw materials, observing the reaction situation, and having a general understanding of the target product.

[0036] (3) The ratio of raw materials can also be changed to induce the growth of crystals of different ratios.

[0037] In the actual crystal growth experiment, the traditional chemical vapor transport method needs to spend several months to explore the experimental parameters of chemical vapor transport method single crystal growth, such as the type of transport agent, the amount of transport agent, the temperature range setting, the ratio adjustment of raw materials, etc. Usually, a key variable is adjusted and other variables are controlled to determine the optimal parameters for crystal growth. This is a long and repetitive task that takes a lot of time and experimental consumables.

[0038] For example, to grow a binary system single crystal, it is necessary to investigate a large amount of literature to find its phase diagram, summarize the different proportions that may exist according to the reports, and explore the specific reaction temperature for different proportions, and conduct experimental exploration. If the high-throughput chemical vapor transport method of the present invention is adopted, the two metal powders can be placed in small glass tubes respectively, and reacted under a temperature gradient to generate gaseous intermediates of different proportions, and single crystals of different proportions are generated in the crystallization area. Using this method, the main parameter that needs to be adjusted is only the temperature range. The experimental amount is greatly reduced, and single crystals of different proportions can also be obtained.

[0039] For another example, during an experiment, it is necessary to study the change in its physical properties through doping. In the process of doping, it is often necessary to explore different doping ratios, which requires a large amount of experiments. If the high-throughput experimental method of the present invention is used to place the parent material in small glass tubes, the doped substance is placed in a small glass tube separately, and a glass tube with a larger diameter is used to place all the small glass tubes, single crystals with different doping ratios can be obtained through one experiment.

[0040] The embodiments described above are only preferred embodiments of the present invention and are only used to explain the present invention, not to limit the scope of implementation of the present invention. For those skilled in the art, other implementation methods can certainly be easily made by replacement or modification based on the technical contents disclosed in this specification. Therefore, all changes and improvements made to the principles and process conditions of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A method for preparing a single crystal using high-throughput chemical vapor transport, characterized in that: The following steps are involved: Different raw materials are separately placed in the raw material area of ​​the quartz tube, a transport agent is added to each raw material, and the quartz tube is evacuated and sealed; then the quartz tube is placed in a heating furnace for heating, and the heating temperatures of the raw material area and the crystallization area are set respectively to form different temperature gradients. After heating, the raw materials react with the transport agent to generate gaseous compounds, and then the raw materials react freely with each other, move from the high temperature area to the low temperature area under the action of the temperature gradient, and crystallize and grow in different temperature areas.

2. The method for preparing a single crystal by high-throughput chemical vapor transport according to claim 1, characterized in that: Different raw materials are placed in small glass tubes with one end open respectively so that different raw materials can be separately arranged in the raw material area of ​​the quartz tube.

3. The method for preparing a single crystal by high-throughput chemical vapor transport according to claim 1, characterized in that: The water and oxygen contents in the sealed quartz tube are controlled below 0.1 ppm.

4. A method for preparing a single crystal by high-throughput chemical vapor transport according to any one of claims 1 to 3, characterized in that: The method is used to prepare Fe-Ge series single crystals, comprising the following steps: placing iron powder and germanium powder in small glass tubes with one end open, adding iodine as a transport agent in each small glass tube, evacuating the quartz tube and sealing it; then placing the quartz tube in a heating furnace for heating, setting the temperature of the raw material area to 600-1100°C, the temperature of the crystallization area to 500-1000°C, and the growth time to 7-21 days, so as to obtain FeGe with different proportions. x Single crystal; the temperature of the crystallization region is lower than the temperature of the raw material region.

5. The method for preparing single crystals by high-throughput chemical vapor transport according to claim 4, characterized in that: The temperature of the raw material area was set to 600°C, the temperature of the crystallization area was set to 500°C, and the growth time was 14 days.

6. The method for preparing single crystals by high-throughput chemical vapor transport according to claim 4, characterized in that: The method obtained six ratios of FeGe x Single crystal, respectively FeGe 0.60 ,FeGe 0.66 ,FeGe 0.73 , single FeGe 0.78 ,FeGe 0.81 andFeGe 0.84 .

7. The method for preparing single crystals by high-throughput chemical vapor transport according to claim 4, characterized in that: The mass ratio of the iron powder to the germanium powder is 1:

1.

8. The method for preparing single crystals by high-throughput chemical vapor transport according to claim 4, characterized in that: The amount of the transport agent added is 0.5 g / cm 3 .

9. The method for preparing single crystals by high-throughput chemical vapor transport according to claim 7, characterized in that: The transport agent was divided into two equal parts and added into two small glass tubes respectively.

10. The method for preparing single crystals by high-throughput chemical vapor transport according to claim 4, characterized in that: The heating furnace is a double temperature zone furnace.

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