CN114839009A - Device and method for de-twining layered single crystal sample - Google Patents
Device and method for de-twining layered single crystal sample Download PDFInfo
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Abstract
The invention provides a device and a method for de-twining a layered single crystal sample, wherein the device comprises the following components: a metal outer frame with an inner cavity; and a metal sheet positioned in the inner cavity of the metal outer frame; two ends of the metal sheet are fixed with the metal outer frame; the thermal expansion coefficient of the metal outer frame is smaller than that of the metal sheet; the metal sheet is configured to bear and fix a sample, and under a low-temperature environment, due to the difference of the thermal expansion coefficients of the metal outer frame and the metal sheet, the metal sheet is subjected to a tensile force and transmits tensile strain to the sample. The device can realize the de-twinning of the single crystal sample and can transfer the residual uniaxial strain to the single crystal sample, so that the sample has certain uniaxial strain on the basis of de-twinning.
Description
Technical Field
The invention relates to the technical field of metallographic microscopic analysis. And more particularly, to an apparatus and method for de-twining a layered single crystal sample.
Background
For most iron-based superconductors, the system experiences a tetragonal phase (a) as the temperature decreases T ＝b T ) To orthonormal phase (a) o >b o ) Structural phase transition (T)<T S ) The included angle between the unit cell vectors is 45 deg. Researches show that two groups of symmetrical twin crystal domain structures are formed in the iron-based superconductor after the structural phase change, and the crystal domains are mutually parallel or vertically arranged in a regular stripe shape in a sample ab plane along the directions of (100) and (010) of a tetragonal phase; the sample can extend to the whole sample along the direction c without being influenced by surface defects of the sample and the like; if the sample quality is high, the twin domain walls are smooth and regular with a pitch of about 10 microns, as shown in FIGS. 1 and 2.
In the iron-based superconductor, the origin of physical phenomena such as superconductivity and resistance anisotropy is still lack of a relatively unified theoretical explanation. The existence of twin crystal phenomenon hinders researchers from researching intrinsic magnetism, resistance and other properties in the system [2-3] . For example, the presence of twinning, resulting in T<T S In the structure peak (020) o Has the existing position (020) o Also has a contribution of (200) o A contribution. In the experiment, it is very important to research and develop a mature de-twinning method. Currently, the de-twinning process for the realization of bulk single crystal samples of large dimensions (in the order of centimeters) by the application of uniaxial mechanical stress is relatively mature but is accompanied by a large background signal from the de-twinning apparatus. Relatively mature methods for de-twining a layered single crystal sample with a smaller size (millimeter level) are still lacking in experimental research.
Layered single crystal samples, FeSe (T), with iron-based superconductors S 90K), the basic size of the sample is 2 x 0.05mm 3 . Researchers have studied the information of magnetism, resistance and the like of the FeSe single crystal in the twin crystal state by adopting different experimental means. But is limited by the development of the de-twinning technology, and the intrinsic physical properties of the FeSe single crystal need to be further researched. Based on the device, a novel device for de-twining the layered single crystal sample is invented and designed, and the practicability and feasibility of the device are verified by adopting various experimental means.
Disclosure of Invention
Aiming at the problems, the invention provides a device for de-twining a layered single crystal sample so as to solve the problem that the traditional mechanical pressurization mode cannot be used for de-twining the layered single crystal sample with a small size (millimeter level).
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a device for de-twining a layered single crystal sample, which comprises:
a metal outer frame with an inner cavity; and
the metal sheet is positioned in the inner cavity of the metal outer frame;
two ends of the metal sheet are fixed with the metal outer frame;
the thermal expansion coefficient of the metal outer frame is smaller than that of the metal sheet;
the metal sheet is configured to bear and fix a sample, and under a low-temperature environment, due to the difference of the thermal expansion coefficients of the metal outer frame and the metal sheet, the metal sheet is subjected to a tensile force and transmits tensile strain to the sample.
In addition, preferably, the metal sheet includes a middle area, two transition areas located at two ends of the middle area, and two fixing areas formed at one end of the two transition areas far from the middle area respectively for being combined and fixed with the metal outer frame;
the two side parts of the transition area gradually narrow towards the middle area.
In addition, preferably, the junction between the intermediate region and the transition region and the junction between the transition region and the fixing region both include an arc-shaped transition portion.
In addition, preferably, both side portions of the middle region are straight sides;
the two side edge parts of the transition area are inclined edges which gradually gather together.
In addition, it is preferable that the length direction of the metal outer frame is defined as a first direction, the width direction of the metal outer frame is defined as a second direction, and the height direction of the metal outer frame is defined as a third direction;
the metal sheet is arranged along the first direction;
the size of the metal outer frame in the first direction is 95mm, the size of the metal outer frame in the second direction is 45mm, and the size of the metal outer frame in the third direction is 5 mm;
the size of the middle area in the first direction is 20mm, the size of the middle area in the second direction is 15mm, and the size of the middle area in the third direction is 0.2 mm;
the size of the fixed area in the first direction is 7mm, the size of the fixed area in the second direction is 35mm, and the size of the fixed area in the third direction is 0.2 mm.
In addition, preferably, the device further comprises a connecting part formed on the metal outer frame and used for connecting with external equipment.
In addition, preferably, the metal outer frame is made of invar alloy; the metal sheet is made of 6061 aluminum alloy.
In addition, preferably, the device comprises two clamping fixing pieces which are arranged at two ends of the metal sheet and fixed with the metal outer frame, and the metal sheet is positioned between the two clamping fixing pieces; the two clamping fixtures are configured to clamp and fix the metal sheet within the metal frame.
The invention also provides a method for de-twining the layered single crystal sample, which comprises the following steps:
fixing two ends of the metal sheet with the metal outer frame;
fixing the layered single crystal sample on a metal sheet;
under the low-temperature environment, because the thermal expansion coefficient of the metal outer frame is smaller than that of the metal sheet, the metal sheet is subjected to tensile force and transmits tensile strain to the sample;
analyzing the sample;
the analysis includes anisotropic resistivity testing or elastic neutron diffraction measurements.
In addition, it is preferable that both ends of the metal sheet are fixed in the metal outer frame by a clamping fixture, and the method further includes:
uniformly coating STYCAST 2850FT glue on the contact position of the metal sheet, the clamping and fixing piece and the metal outer frame, and baking for 2 hours at the temperature of 65 ℃.
The invention has the beneficial effects that:
the device can be widely applied to various layered single crystal samples, can realize the de-twinning of the single crystal samples, and can transfer the residual uniaxial strain to the single crystal samples, so that the samples have certain uniaxial strain on the basis of de-twinning.
In experimental research, on one hand, the improvement of the de-twinning technology is beneficial to researching the intrinsic properties of a sample, and the understanding of a researcher to a researched system is enhanced; on the other hand, the introduction of uniaxial strain in the system may induce some novel physical phenomena or cause changes in sequence parameters.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
FIG. 1 is CaFe 2 As 2 Single crystal (T) S 173K) optical images of single crystal domain structures at 293K and 5K.
FIG. 2 is a graph showing the results of BaFe 2 As 2 In a single crystal, when T<T S (138K) When the crystal is in the tetragonal phase, the structural phase of the tetragonal phase lattice is changed into the orthogonal phase and two groups of twin crystal domains are formed.
Fig. 3 is a schematic view of the overall structure of the present invention.
Fig. 4 is a schematic view of the structure of the metal sheet of the present invention.
FIG. 5 is a graph of the invention in conjunction with a single sample.
FIG. 6 is an anisotropic resistivity measurement of a de-twinned FeSe single crystal and characterization of the uniaxial strain of the device.
FIG. 7 is a graph of the invention in conjunction with multiple samples.
Fig. 8 shows the result of neutron diffraction of the structural peak (020) of the detwinned state FeSe (tightening top screw) and the result of neutron diffraction of the structural peak (020) of the twinned state FeSe (loosening top screw).
Detailed Description
Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
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.
Techniques and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be considered a part of the specification where appropriate.
In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
The traditional mechanical pressurization mode is that the stress is directly transmitted to a centimeter-sized single crystal sample by rotating a screw, so that the stress cannot be directly transmitted to the millimeter-sized single crystal sample.
In addition, the traditional mechanical pressurizing method needs a certain hardness of the sample, and the layered soft sample cannot bear the pressurizing method.
The method aims to solve the problem that the traditional mechanical pressurization mode cannot be used for de-twining a layered single crystal sample with the dimension of millimeter magnitude. The invention provides a device for de-twining a layered single crystal sample, which is shown in a combined mode in figures 1 to 8 and specifically comprises the following components: a metal outer frame 1 with an inner cavity; and a metal sheet 2 positioned in the inner cavity of the metal outer frame 1; two ends of the metal sheet 2 are fixed with the metal outer frame 1; the thermal expansion coefficient of the metal outer frame 1 is smaller than that of the metal sheet 2; the metal sheet 2 is configured to bear and fix the sample 3, and under a low-temperature environment, due to the difference of the thermal expansion coefficients of the metal outer frame 1 and the metal sheet 2, the metal sheet 2 is subjected to a tensile force and transmits the tensile strain to the sample 3 through glue. The device can be widely applied to de-twinning multiple layered single crystal samples and can apply uniaxial strain to the samples, successfully solves the technical problems of de-twinning of the layered samples with smaller size in the iron-based superconductor, and is beneficial to researchers to detect the intrinsic properties in the systems by adopting multiple experimental methods, thereby enhancing the understanding of the interaction of multiple sequence parameters in the systems; for a layered single crystal sample without twinning effect, the device can apply uniaxial strain to the single crystal along a specific direction, and can induce a new physical phenomenon or regulate and control the existing sequence parameters.
The design concept of the device comes from the difference of the thermal expansion coefficients of different metals. The metal frame 1 is made of invar alloy and has a thermal expansion coefficient of about 2 × 10 -6 K; 6061 aluminum alloy is used for the metal sheet 2, and the thermal expansion coefficient is about 24 multiplied by 10 -6 and/K. Along with the reduction of the temperature, the invar alloy outer frame shrinks slowly with the 6061 aluminum alloy sheet with the thickness of 0.2mm, which is adhered with the sample, due to the difference of the thermal expansion coefficients, the inner 6061 aluminum alloy sheet shrinks quickly, and the aluminum alloy sheet is connected with the invar alloy outer frame through STYCAST 2850FT glue and a screw, so that the aluminum alloy sheet is stretched along the length direction of the metal outer frame at low temperature. The aluminum alloy sheet is designed into a specific shape with wider two ends and narrower middle, and uniaxial strain is [ -22 x (300-T). times.10 ] in the process of cooling -6 ]More uniformly and intensively converging to a narrower area in the middle of the aluminum alloy sheet. The strain is simultaneously transferred to a plurality of single crystal samples under the action of specific glue, so that the large-area layered single crystal samples simultaneously de-twins or are regulated and controlled by uniaxial strain.
In an embodiment, regarding the specific structure of the metal sheet 2, the metal sheet 2 includes a middle area 21, two transition areas 22 located at two ends of the middle area 21, and two fixing areas 23 respectively formed at one end of the two transition areas 22 away from the middle area 21 for being combined and fixed with the metal outer frame 1; the two side portions of the transition region 22 are tapered toward the intermediate region 21.
Further, in order to prevent the stress from being too concentrated at the connection between the intermediate region 21 and the transition region 22 and at the connection between the transition region 22 and the fixing region 23, the connection between the intermediate region 21 and the transition region 22 and the connection between the transition region 22 and the fixing region 23 both include an arc-shaped transition portion 24.
More specifically, both side portions of the middle region 21 are arranged in parallel straight edges, and both side portions of the transition region 22 are arranged in symmetrical oblique edges. Through the arrangement, the strain can be more uniformly and intensively gathered in the middle area of the aluminum alloy sheet.
In the above embodiment, it is defined that the length direction of the metal outer frame 1 is a first direction, the width direction of the metal outer frame 1 is a second direction, and the height direction of the metal outer frame 1 is a third direction; the metal sheet 2 is arranged along the first direction; the size of the metal outer frame 1 in the first direction is 95mm, the size of the metal outer frame 1 in the second direction is 45mm, and the size of the metal outer frame 1 in the third direction is 5 mm; the dimension of the intermediate zone 21 in the first direction is 20mm, the dimension of the intermediate zone 21 in the second direction is 15mm, and the dimension of the intermediate zone 21 in the third direction is 0.2 mm; the size of the fixing area 23 in the first direction is 7mm, the size of the fixing area 23 in the second direction is 35mm, the size of the fixing area 23 in the third direction is 0.2mm, and the total length of the metal sheet 2 in the first direction is 77 mm. The dimensions of the sheet 2 are particularly critical in the overall device design, and the sample 3 is affixed to the sheet 2 at the intermediate zone 21, and in order to prevent strain concentration at the transition zone 22, a slow transition is required over a longer distance. On the premise of the same size of the metal outer frame 1, the narrower the middle area of the metal sheet 2 for bearing the sample 3, the larger the strain, but the limited quality of the sample 3 which can be pasted. (when the intermediate zone is too narrow, the sample is few and the quality is insufficient, the higher test data quality is difficult to obtain) in the experiment, the inner diameter of the cavity of the measuring instrument and the requirement for the sample amount are also considered.
In an embodiment, the apparatus further comprises a connecting portion 4 formed on the metal frame 1 for connecting with an external device, wherein the connecting portion 4 is used for connecting the apparatus with a testing instrument.
In one embodiment, the device includes two clamping fixtures 5 arranged at two ends of the metal sheet 2 and fixed to the metal frame 1, and the metal sheet 2 is located between the two clamping fixtures 5; the two clip fixtures 5 are configured to clip and fix the metal sheet 2 within the metal outer frame 1.
Furthermore, the metal outer frame 1 is made of invar alloy; the clamping fixing piece 5 and the metal sheet 2 are both made of 6061 aluminum alloy; the clamping fixing piece 5 fixes the metal sheet through an M3 stainless steel screw with the length of 4mm, and the clamping fixing piece connects and fixes the metal sheet 2 and the invar outer frame through an M3 stainless steel screw (namely, a top screw 6) with the length of 12 mm; the screws on the whole device are screwed, and the function of fixing the metal sheet 2 is mainly realized, but the function of stretching the metal sheet 2 is not realized.
In conclusion, the device can be widely applied to various layered single crystal samples, can realize the de-twinning of the single crystal samples, and can transfer the residual uniaxial strain to the single crystal samples, so that the samples have certain uniaxial strain on the basis of de-twining.
In experimental research, on one hand, the improvement of the de-twinning technology is beneficial to researching the intrinsic properties of a sample, and the understanding of a researcher to a researched system is enhanced; on the other hand, the introduction of uniaxial strain in the system may induce some novel physical phenomena or cause changes in sequence parameters.
In another embodiment, the present invention also provides a method for de-twining a layered single crystal sample, the method comprising: fixing two ends of a metal sheet 2 with a metal outer frame 1, wherein in the assembly process, two ends of the metal sheet 2 are fixed in the metal outer frame through a clamping and fixing piece 5, further, STYCAST 2850FT glue is required to be uniformly coated at the contact position of the metal sheet 2 with the clamping and fixing piece 5 and the metal outer frame 1, and the metal sheet is baked for 2 hours at the temperature of 65 ℃, so that the operation can reduce the stress concentration around a screw hole correspondingly matched with an M3 stainless steel screw, and prevent the metal sheet 2 from being broken or sliding along the screw hole direction in the stretching process, thereby causing the relaxation and loss of the tension; fixing the layered single crystal sample 3 on the metal sheet 2; under the low temperature environment, because the thermal expansion coefficient of the metal outer frame 1 is smaller than that of the metal sheet, the metal sheet 2 is under tension and transmits the tensile strain to the sample 3; sample 3 was analyzed; the analysis comprises an anisotropic resistivity test or elastic neutron diffraction measurement; the measurement is carried out by a PPMS (comprehensive physical property measurement system), and the analysis is carried out by data processing by matlab.
Taking the example of a single crystal of a layer of smaller size, FeSe, in an iron-based superconductor (typical size 2 x 0.05 mm) 3 ) We characterize the de-twinning effect of the device through a plurality of experimental modes: (1) carrying out transport measurement (testing the anisotropic resistivity of the de-twinned FeSe single crystal) by combining a comprehensive physical property measurement system PPMS; (2) elastic neutron diffraction measurement; the results are as follows:
(1) transport measurement
The anisotropic resistivity measurement of the de-twinned FeSe single crystal is completed based on a comprehensive Physical Property Measurement System (PPMS) and combined with a multifunctional rod. The overall dimensions of the device for de-twinning a layered single crystal sample can be suitably reduced to achieve adaptation to the PPMS cavity, subject to the internal diameter of the PPMS cavity, it being understood that the above operations are only performed with a corresponding reduction in overall dimensions, and the principle thereof is not changed.
Adhering a FeSe single crystal sample to the center of an aluminum alloy sheet by using hydrogen-free glue Cytop, and adjusting the tetragonal phase of the single crystal sample (110) T The direction is parallel to the straight edge of the aluminum alloy sheet. The intrinsic resistivity rho of the twin-crystal-removed FeSe single crystal in the a and b directions is measured by adopting a Montgomery resistance measurement method a And ρ b (ii) a By (ρ) b -ρ a )/(ρ b +ρ a ) The characteristic resistance anisotropy can reach 6%, as shown in fig. 6, indicating that the FeSe single crystal is highly dephased.
In order to further exclude the influence of Poisson's ratio and characterize uniaxial strain on the aluminum alloy sheet at low temperature, strain in the central rectangular area of the aluminum alloy sheet was measured using a strain gauge (type: WK-05-062TT-350) capable of measuring strain in both horizontal (b-direction) and vertical (a-direction) directions, and the result was shown as b in FIG. 6 (in the experimental de-twinning study, the default pressing direction was the b-direction, i.e., the second direction, while the apparatus was applying a tensile force in the vertical direction, so the vertical direction was the a-direction, i.e., the first direction).
The two curves at b in fig. 6 correspond to the difference in strain in the first direction and the second direction in the uniform and narrow rectangular region at the center of the aluminum alloy sheet in the state where the screws 6 at the top of the apparatus are tightened and loosened, respectively. For the former, the uniaxial strain of the uniform rectangular region at low temperature can reach epsilon vertical -ε horizontal (ε a -ε b )＝5×10 -3 Sufficient to de-twinning the FeSe; for the latter, only very small residual strains can be seen.
By combining the above analysis, we have designed the aluminum alloy sheet to be wide at both ends and narrow in the middle, keeping its elastic coefficient lower than that of other parts, thereby generating elastic deformation. Transportation measurement proves the practicability and scientificity of the device from various angles, and can successfully realize that the layered FeSe single crystal is de-twinned and the central narrow region of the aluminum alloy sheet has 5 multiplied by 10 under low temperature -3 Uniaxial strain of (2).
(2) Elastic neutron diffraction measurement
Elastic neutron diffraction is an experimental probe well characterizing the de-twinning ratio of the device. Elastic neutron diffraction can measure bragg diffraction of the single crystal structure peak. In neutron scattering or neutron diffraction experiments, cadmium (with a large neutron absorption section) can be used for wrapping invar alloy, redundant aluminum alloy sheets and the like of the outer frame of the device, only the sample part is exposed in the neutron beam range, and background signals can be reduced.
Referring to FIG. 7, a plurality of FeSe single crystals of tetragonal phase (110) are bonded to an aluminum alloy sheet T The direction is parallel to the a/b direction. The twin crystal removing effect of the device is characterized by adopting a 'known' cold triaxial polarization spectrometer on a neutron source of a Chinese advanced research reactor (CARR reactor) of the Chinese atomic energy science research institute.
A and b in FIG. 8 are neutron diffraction results of the structural peak (020) of the twin-state FeSe (tightening top screw 6) and the twin-state FeSe (loosening top screw 6), respectively, and the temperatures corresponding to the two curves are 20K (T) respectively<T S ) And 120K (T)>T S )。
For the FeSe single crystal in the twin crystal state, the diffraction peak at the position of (020) is weakened in strength and the full width at half maximum is widened below the structural phase transition temperature. After Gaussian function fitting, the diffraction peak at (020) is split from one peak into two peaks with similar spectral weights along with the reduction of temperature. The two peaks appear because the structural peak (020) o has the existing peak (020) after entering the twin crystalline state o The peak contribution also has (200) o The peak contributions, which are comparable. Machine for finishingIn particular, T S Above and below, the spectral weights of the diffractograms are substantially conserved, as shown by b in fig. 8.
For the FeSe single crystal in the de-twinning state, fitting T by adopting a Gaussian function<T S And T>T S Diffraction pattern at structural peak (020) is found when T is<T S Splitting of peaks likewise occurs, the two peaks corresponding to it being (020) o The contribution of the peak (right side) is also (200) o Contribution of peak (left), but the spectral weights of the two peaks are significantly different. Adopt (I (020) o -I(200) o )/(I(020) o +I(200) o ) Demarcating the de-twinning ratio which can reach about 71 percent, wherein I (020) o And I (200) o Represents a structural peak (020) in the orthogonal phase o And (200) o The strength of (2). And T is<T S And T>T S The two spectra are conserved again, as shown in a in FIG. 8.
By combining the analysis, the device can directly and simultaneously perform partial de-twinning on a large amount of FeSe single crystals (the de-twinning ratio is as high as-71%), and the influence of background signals is effectively reduced by the whole device. The wide application of the device will help researchers to study the intrinsic properties of similar systems.
It should be understood that the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it will be obvious to those skilled in the art that other variations or modifications may be made on the basis of the above description, and all embodiments may not be exhaustive, and all obvious variations or modifications may be included within the scope of the present invention.
Claims (10)
1. An apparatus for de-twinning a layered single crystal sample, comprising:
a metal outer frame with an inner cavity; and
the metal sheet is positioned in the inner cavity of the metal outer frame;
two ends of the metal sheet are fixed with the metal outer frame;
the thermal expansion coefficient of the metal outer frame is smaller than that of the metal sheet;
the metal sheet is configured to bear and fix a sample, and under a low-temperature environment, due to the difference of the thermal expansion coefficients of the metal outer frame and the metal sheet, the metal sheet is subjected to a tensile force and transmits tensile strain to the sample.
2. The device for the layered single crystal sample twinning regression as claimed in claim 1, wherein said metal sheet comprises a middle region, two transition regions located at two ends of the middle region, and two fixing regions formed at one end of the two transition regions away from the middle region respectively for combining and fixing with the outer metal frame;
the two side parts of the transition area gradually narrow towards the middle area.
3. The apparatus according to claim 2, wherein the junction of the intermediate region and the transition region and the junction of the transition region and the fixing region each comprise an arc-shaped transition portion.
4. The device for the layered single crystal sample twinning as claimed in claim 2, wherein both side portions of the middle region are straight-sided;
the two side parts of the transition area are inclined edges which gradually gather together.
5. The apparatus for de-twining a layered single crystal sample according to claim 2,
defining, wherein the length direction of the metal outer frame is a first direction, the width direction of the metal outer frame is a second direction, and the height direction of the metal outer frame is a third direction;
the metal sheet is arranged along the first direction;
the size of the metal outer frame in the first direction is 95mm, the size of the metal outer frame in the second direction is 45mm, and the size of the metal outer frame in the third direction is 5 mm;
the size of the middle area in the first direction is 20mm, the size of the middle area in the second direction is 15mm, and the size of the middle area in the third direction is 0.2 mm;
the size of the fixed area in the first direction is 7mm, the size of the fixed area in the second direction is 35mm, and the size of the fixed area in the third direction is 0.2 mm.
6. The apparatus as claimed in claim 1, further comprising a connecting part formed on the metal frame for connecting to an external device.
7. The device for the de-twinning of the layered single crystal sample according to claim 1, wherein the metal outer frame is made of invar alloy; the metal sheet is made of 6061 aluminum alloy.
8. The device for the layered single crystal sample twinning regression as claimed in claim 1, wherein said device comprises two holding fixtures arranged at two ends of the metal sheet and fixed with the metal outer frame, said metal sheet is located between the two holding fixtures; the two clamping fixtures are configured to clamp and fix the metal sheet within the metal frame.
9. A method for de-twinning a layered single crystal sample, the method comprising:
fixing two ends of the metal sheet with the metal outer frame;
fixing the layered single crystal sample on a metal sheet;
under the low-temperature environment, because the thermal expansion coefficient of the metal outer frame is smaller than that of the metal sheet, the metal sheet is subjected to tensile force and transmits tensile strain to the sample;
analyzing the sample;
the analysis includes anisotropic resistivity testing or elastic neutron diffraction measurements.
10. The method for de-twining a layered single crystal sample according to claim 9,
the two ends of the metal sheet are fixed in the metal outer frame through the clamping fixing piece, and the method further comprises the following steps:
and uniformly coating STYCAST 2850FT glue on the contact position of the metal sheet, the clamping and fixing piece and the metal outer frame, and baking at 65 ℃ for 2 hours.
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