CN116288640A - Low-temperature electrolytic polishing method for preparing Bi2Te 3-based thermoelectric material EBSD sample - Google Patents

Low-temperature electrolytic polishing method for preparing Bi2Te 3-based thermoelectric material EBSD sample Download PDF

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CN116288640A
CN116288640A CN202211646809.2A CN202211646809A CN116288640A CN 116288640 A CN116288640 A CN 116288640A CN 202211646809 A CN202211646809 A CN 202211646809A CN 116288640 A CN116288640 A CN 116288640A
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electrolytic polishing
power supply
temperature
ebsd
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韩福洲
王琪琛
任杰
李阁平
郭文斌
胡嘉南
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Institute of Metal Research of CAS
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    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F3/00—Electrolytic etching or polishing
    • C25F3/16—Polishing
    • C25F3/30—Polishing of semiconducting materials
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
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Abstract

Bi preparation method 2 Te 3 Low-temperature electrolytic polishing method of base thermoelectric material EBSD sample comprises the following steps of firstly carrying out Bi preparation 2 Te 3 Performing linear cutting on the material, and performing grinding, polishing and polishing on the obtained sample; the electrolytic polishing solution is perchloric acid-alcohol solution with perchloric acid volume fraction of 9% -12%; then pouring electrolytic polishing solution with the volume of 2/3 of that of the beaker into the beaker, taking metal as a cathode, taking tweezers made of iron or inert metal as an anode, turning on a power supply, modulating the voltage of a constant-current and voltage-stabilized power supply to 15-20V at normal temperature, and turning off the power supply after the current is modulated to 1-3A; taking out the cathode and anode, pouring liquid nitrogen into beaker, stirring, and clamping Bi with forceps when temperature is reduced below-60deg.C 2 Te 3 The sample, the cathode and the anode are put into the electrolytic polishing solution again and the circuit is reconnected, the power supply is turned on, and the current gradually rises from 0.1-0.2A to 1-And 3A, taking out the sample, cleaning and drying the sample. The method is efficient, stable and simple to operate, and can prepare high-quality EBSD samples, and the EBSD data resolution ratio is up to more than 98%.

Description

Bi preparation method 2 Te 3 Low-temperature electrolytic polishing method for base thermoelectric material EBSD sample
Technical Field
The invention belongs to the technical field of material preparation, and particularly provides a method for preparing Bi 2 Te 3 A low temperature electropolishing method for base thermoelectric material EBSD samples.
Background
Bi 2 Te 3 The base thermoelectric material belongs to low-temperature thermoelectric materials, has higher thermoelectric conversion efficiency near room temperature, and is the only commercial thermoelectric material for large-scale application. The crystal structure is as follows
Figure BDA0004009951620000011
The crystal system has anisotropy, so that the thermoelectric transport property and the mechanical property of the crystal system are obviously different in different orientations. The introduction of textures with different orientations in the material has remarkable influence on mechanical properties, and can optimize carrier concentration and improve thermoelectric efficiency.
At present, in order to greatly develop the 5G communication technology in China, a semiconductor refrigerator with higher performance needs to be prepared, which is a technology for Bi 2 Te 3 The thermoelectric conversion efficiency and mechanical properties of the thermoelectric-based materials are more demanding, and therefore, it is necessary to use EBSD (electron back scattering diffraction) technology to provide more detailed and accurate information on grain orientation, texture, and morphology, which also places higher demands on preparing EBSD samples. However, in the process of preparing the EBSD sample, a large amount of scratches and stress are introduced during polishing of the sample due to poor mechanical properties of the material, so that the surface EBSD information is damaged and lost, and the stress needs to be released as much as possible and the scratches need to be removed. The method for preparing the EBSD sample is widely used at present because of low equipment cost, simple and convenient operation and small sample size requirement of the electrolytic polishing method. Factors affecting the electropolishing effect are primarily related to electropolishing fluid composition, electropolishing parameters, and temperature.
There are only a few documents currently reporting on the study of texture and grain orientationLight step and parameters, e.g. scholars K.C.Tewari at Electropolishing of Bi 2 Te 3 based alloys one herein proposes to prepare a 1L solution as an electropolishing solution with 90g potassium hydroxide, 56g tartaric acid, 220ml glycerol and deionized water, but specific polishing parameters are not given; the scholars Mark Homer proposed in Preparation Methods for TEM Specimens of Bismuth Telluride and Related Thermoelectric Alloys to prepare an electrolyte with 53% water, 38% glycerol, 5% sodium hydroxide and 4% tartaric acid and electropolish the sample at 10-15V, but the sample prepared by this method was only subjected to TEM observation, did not show EBSD observation results, and the electrolyte composition was complex.
Therefore, a Bi which is efficient, stable, and simple is provided 2 Te 3 It is extremely important that the electrolytic polishing method of the thermoelectric material fills the gap in this field.
Disclosure of Invention
The purpose of the present invention is to provide a method for producing Bi 2 Te 3 The low-temperature electrolytic polishing method of the base thermoelectric material EBSD sample is efficient, stable and simple and convenient to operate, can be used for preparing a high-quality EBSD sample, has the EBSD data resolution rate of more than 98%, has clear tissue morphology, can accurately provide sample crystallographic information, and is convenient for analyzing the problems of grain orientation, texture and the like. By the method, scratches on the surface of the sample can be effectively removed, and the grain boundary on the surface of the sample is clear. The sliding line can be clearly seen on the deformed sample, and the sample has higher resolution.
The technical scheme of the invention is as follows:
bi preparation method 2 Te 3 The low-temperature electrolytic polishing method of the EBSD sample based on the thermoelectric material is characterized by comprising the following steps of:
1) Bi according to the EBSD sample size requirement 2 Te 3 Performing wire cutting on the material, wherein the thickness is 1-3 mm, and marking corresponding TD, RD and ND directions;
2) Polishing the cut sample, and polishing after polishing off cutting marks;
3) Preparing an electrolytic polishing solution:
preparing perchloric acid-alcohol solution with perchloric acid volume fraction of 9% -12% as electrolytic polishing solution;
4) Electropolishing and subsequent treatment:
pouring electrolytic polishing solution with the volume of 2/3 of that of the beaker into the beaker, connecting the electrolytic polishing solution with a cathode by using metal, connecting the electrolytic polishing solution with a cathode of a direct current power supply, and connecting the electrolytic polishing solution with an anode by using iron tweezers or tweezers made of inert metal; switching on the power supply, modulating the voltage of the constant-current and stabilized power supply to 15-20V at normal temperature, and switching off the power supply after the current is modulated to 1-3A; taking out the cathode and anode, pouring liquid nitrogen into beaker, stirring, and clamping Bi with forceps when temperature is reduced below-60deg.C 2 Te 3 The sample, the cathode and the anode are put into the electrolytic polishing solution again and are connected with the circuit again, the power supply is turned on, the current gradually rises from 0.1 to 0.2A to 1 to 3A along with the rise of the temperature of the electrolyte, in the process, whether black substances are generated in the electrolytic polishing solution or not is observed in time, and if the black substances are generated, the Bi is proved 2 Te 3 And (3) electropolishing the sample, turning off the power supply when the current is 1-3A, rapidly taking out the sample, cleaning the surface with water, if the surface of the sample has residual black substances, wiping the surface with cotton under the flushing of water flow, and finally flushing with alcohol and drying. If no black substance is generated, the sample is not electrified, only chemical corrosion is carried out, the power supply is immediately turned off, the sample is polished again, and electrolytic polishing is carried out again.
As a preferable technical scheme:
in step 2), due to Bi 2 Te 3 The material is softer and fragile, 2000# sand paper is selected for polishing the sample, and then soft black damping cloth and W2.5 polishing paste are selected for mechanical polishing, so that the number and depth of scratches can be effectively reduced, stress can be conveniently released in the electrolytic polishing process, and the scratches are eliminated. The sample was then rinsed with alcohol and blow dried.
In the step 3), a glass measuring cylinder is used for measuring a proper amount of perchloric acid, the perchloric acid is poured into alcohol (absolute ethyl alcohol), and a glass rod is used for continuously stirring and radiating heat, wherein the volume fraction of the perchloric acid is 9% -12%.
In step 4), the cathode is stainless steel or titanium alloy.
The sample electropolished by the method can be used for various observation means such as a Scanning Electron Microscope (SEM) and Electron Back Scattering Diffraction (EBSD), and the like, and has clear images, high resolution ratio of more than 98% and extremely high quality.
The characteristics of the invention are as follows:
1. for Bi 2 Te 3 The thermoelectric material is based, and a detailed, efficient and stable electrolytic polishing method is provided, has detailed electrolytic polishing parameters and electrolytic polishing liquid components, is simple in components and extremely low in cost, does not have any danger in the configuration process, does not generate harmful gas or pollutants, and is environment-friendly.
2. Can prepare Bi with high quality 2 Te 3 The analysis rate of the EBSD sample based on the thermoelectric material reaches more than 98%, and the crystallographic information and the morphology tissues can be completely and accurately collected, so that the method has great significance in further improving the thermoelectric conversion efficiency and the mechanical property.
3. According to the method, for the sample with deformation, the EBSD sample with high resolution can be prepared, and the sliding trace can be clearly seen.
Drawings
FIG. 1 Bi after electropolishing 2 Te 3 Band image of sample.
FIG. 2 Bi after electropolishing 2 Te 3 IPF image of sample (resolution 98.7%).
FIG. 3 Bi near the indentation after electropolishing 2 Te 3 FSD image of sample.
FIG. 4 Bi near the indentation after electropolishing 2 Te 3 IPF image of sample.
Fig. 5 FSD image of the sample prepared in comparative example 1.
Fig. 6 IPF image of the sample prepared in comparative example 1.
FIG. 7 is an FSD image of a sample prepared by electropolishing at-30 ℃.
FIG. 8 is an IPF image of a sample prepared by electropolishing at-30deg.C for comparative example 2.
Detailed Description
Example 1
Bi preparation method 2 Te 3 The low-temperature electrolytic polishing method of the thermoelectric material-based EBSD sample comprises the following steps of:
(1) Bi prepared by SPS method 2 Te 3 The sample was polished and mechanically polished.
And (3) cutting a sample with a corresponding size by utilizing linear cutting, wherein deeper cutting marks and oxide layers exist on the surface of the cut sample, and grinding and mechanical polishing are needed. Because the hardness of the material is small, the surface layer of the sample can be directly polished by using No. 2000 sand paper, then the sample is mechanically polished by using soft black damping cloth as polishing cloth and W2.5 polishing paste, scratches are lighter and finer as much as possible, stress is released and the scratches are eliminated in the subsequent electrolytic polishing, and then the sample is cleaned and dried by using alcohol.
(2) Preparing electrolytic polishing solution
Preparing 500mL of electrolytic polishing solution with the perchloric acid volume fraction of 10%, measuring 50mL of perchloric acid by using a glass measuring cylinder, pouring the solution into 450mL of alcohol, continuously stirring the solution by using a glass rod for heat dissipation, and cooling the solution to room temperature.
(3) Electrolytic polishing
Pouring an electrolytic polishing solution with the volume of 2/3 of that of the beaker into the beaker, selecting an electrode plate made of stainless steel as a cathode, taking iron tweezers as an anode, and turning on a power supply together with a circuit, modulating the power supply voltage to 15.6V at normal temperature, modulating the current to 2.3A, and turning off the power supply. And then taking out the cathode and the anode, pouring liquid nitrogen into the electrolyte, and continuously stirring for a small amount for many times until the temperature of the electrolyte is reduced to about-80 ℃. The sample is clamped on tweezers, the cathode and the anode are quickly put into electrolyte again, a connecting circuit is powered on to carry out electrolytic polishing, and the initial current is 0.18A. In the electrolytic polishing process, attention is paid to whether black substances are generated or not at all, the precipitation of the black substances represents that the sample is subjected to electrolytic polishing, the power supply is turned off after the current is gradually increased to 2.3A, the sample is taken out for cleaning, and the black substances on the surface are gently wiped clean by cotton and are dried by a blower.
(4) EBSD analysis is carried out on the sample, and the result is analyzed by using Channel 5 software, so that a band image and an inverse pole figure (IPF figure) of the sample are obtained, as shown in figures 1 and 2.
Example 2
Bi preparation method 2 Te 3 The low-temperature electrolytic polishing method of the thermoelectric material-based EBSD sample comprises the following steps of:
(1) For Bi 2 Te 3 The sample was polished and mechanically polished.
And (3) cutting a sample with a corresponding size by utilizing linear cutting, wherein deeper cutting marks and oxide layers exist on the surface of the cut sample, and grinding and mechanical polishing are needed. Because the hardness of the material is small, the surface layer of the sample can be directly polished by using No. 2000 sand paper, then the sample is mechanically polished by using soft black damping cloth as polishing cloth and W2.5 polishing paste, scratches are lighter and finer as much as possible, stress is released and the scratches are eliminated in the subsequent electrolytic polishing, and then the sample is cleaned and dried by using alcohol.
(2) And (3) making a plurality of diamond-shaped indentations on the surface of the polished sample by using a micro Vickers hardness tester, and carrying out local deformation.
(3) Preparing electrolytic polishing solution
Preparing 500mL of electrolytic polishing solution with the perchloric acid volume fraction of 10%, measuring 50mL of perchloric acid by using a glass measuring cylinder, pouring the solution into 450mL of alcohol, continuously stirring the solution by using a glass rod for heat dissipation, and cooling the solution to room temperature.
(4) Electrolytic polishing
Pouring an electrolytic polishing solution with the volume of 2/3 of that of the beaker into the beaker, selecting an electrode plate made of stainless steel as a cathode, taking iron tweezers as an anode, and turning on a power supply together with a circuit, modulating the power supply voltage to 18V at normal temperature, and turning off the power supply after the current is modulated to 2.6A. And then taking out the cathode and the anode, pouring liquid nitrogen into the electrolyte, and continuously stirring for a small amount for many times until the temperature of the electrolyte is reduced to about minus 100 ℃. The sample is clamped on tweezers, the cathode and the anode are quickly put into electrolyte again, a connecting circuit is powered on to carry out electrolytic polishing, and the initial current is 0.12A. In the electrolytic polishing process, attention is paid to whether black substances are generated or not at all, the precipitation of the black substances represents that the sample is subjected to electrolytic polishing, the power supply is turned off after the current is gradually increased to 2.6A, the sample is taken out for cleaning, and the black substances on the surface are gently wiped clean by cotton and are dried by a blower.
(5) The sample was subjected to EBSD analysis to obtain an FSD image of the sample near the indentation as shown in fig. 3. The results were analyzed using Channel 5 software to obtain an antipodal map (IPF map) as shown in fig. 4.
Comparative example 1
The electrolyte is prepared by 53% of water, 38% of glycerol, 5% of sodium hydroxide and 4% of tartaric acid, and the sample is subjected to electrolytic polishing at room temperature of 10-15V, wherein the resolution ratio of the obtained sample is only 78.5%, and the FSD diagram and the IPF diagram of the sample after the electrolytic polishing are shown in figures 5 and 6.
Comparative example 2
The difference from example 1 is that: electropolishing is carried out at the temperature of minus 30 ℃ under the condition that the initial current is 0.5A, and the resolution ratio of the sample FSD graph and the IPF graph after electropolishing is only 70 percent as shown in figures 7 and 8.
The invention is not a matter of the known technology.
The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made in accordance with the spirit of the present invention should be construed to be included in the scope of the present invention.

Claims (5)

1. Bi preparation method 2 Te 3 The low-temperature electrolytic polishing method of the EBSD sample based on the thermoelectric material is characterized by comprising the following steps of:
1) Bi according to the EBSD sample size requirement 2 Te 3 Performing wire cutting on the material, wherein the thickness is 1-3 mm, and marking corresponding TD, RD and ND directions;
2) Polishing the cut sample, and polishing after polishing off cutting marks;
3) Preparing an electrolytic polishing solution:
preparing perchloric acid-alcohol solution with perchloric acid volume fraction of 9% -12% as electrolytic polishing solution;
4) Electropolishing and subsequent treatment:
pouring electrolytic polishing solution with the volume of 2/3 of that of the beaker into the beaker, connecting the electrolytic polishing solution with a cathode by using metal, connecting the electrolytic polishing solution with a cathode of a direct current power supply, and connecting the electrolytic polishing solution with an anode by using iron tweezers or tweezers made of inert metal; switching on the power supply, modulating the voltage of the constant-current and stabilized power supply to 15-20V at normal temperature, and switching off the power supply after the current is modulated to 1-3A; taking out the cathode and anode, pouring liquid nitrogen into beaker, stirring, and clamping Bi with forceps when temperature is reduced below-60deg.C 2 Te 3 The sample, the cathode and the anode are put into the electrolytic polishing solution again and are connected with the circuit again, the power supply is turned on, the current gradually rises from 0.1 to 0.2A to 1 to 3A along with the rise of the temperature of the electrolyte, in the process, whether black substances are generated in the electrolytic polishing solution or not is observed in time, and if the black substances are generated, the Bi is proved 2 Te 3 And (3) electropolishing the sample, turning off the power supply when the current is 1-3A, rapidly taking out the sample, cleaning the surface with water, if the surface of the sample has residual black substances, wiping the surface with cotton under the flushing of water flow, and finally flushing with alcohol and drying.
2. The preparation of Bi according to claim 1 2 Te 3 The low-temperature electrolytic polishing method of the base thermoelectric material EBSD sample is characterized by comprising the following steps of: in the step 2), 2000# sand paper is selected to polish the sample, and then W2.5 polishing paste is selected on the black damping polishing cloth to polish.
3. The preparation of Bi according to claim 1 2 Te 3 The low-temperature electrolytic polishing method of the base thermoelectric material EBSD sample is characterized by comprising the following steps of: in step 4), the cathode is stainless steel or titanium alloy.
4. The preparation of Bi according to claim 1 2 Te 3 The low-temperature electrolytic polishing method of the base thermoelectric material EBSD sample is characterized by comprising the following steps of: the sample after electrolytic polishing is used for a scanning electron microscope or an electronBack-scattering diffraction.
5. The preparation of Bi according to claim 1 2 Te 3 The low-temperature electrolytic polishing method of the base thermoelectric material EBSD sample is characterized by comprising the following steps of: the EBSD data analysis rate of the sample after electrolytic polishing is above 98%.
CN202211646809.2A 2022-12-21 2022-12-21 Low-temperature electrolytic polishing method for preparing Bi2Te 3-based thermoelectric material EBSD sample Pending CN116288640A (en)

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