Seebeck coefficient measuring device for bismuth telluride sheet material

Abstract

The invention relates to the technical field of semiconductor material thermoelectric performance testing, in particular to a bismuth telluride sheet material Seebeck coefficient measuring device. The device mainly comprises a flexible measuring device and a data acquisition system, the data acquisition system is provided with a universal meter and a programmable power supply, the flexible measuring device is connected to the input end of the universal meter through a signal cable to transmit temperature and pressure signals of a thermocouple, and the flexible measuring device is connected to the output end of the programmable power supply through a power supply cable to transmit the temperature and pressure signals of the thermocouple. And the universal meter and the programmable power supply are respectively connected to the computer through communication cables and are connected with the computer to realize data processing. Through the three-in-one design of flexible contact, synchronous sensing and temperature difference control, accurate measurement of the Seebeck coefficient is realized. Through actual measurement, the temperature control precision of the device is + / -0.1 DEG C, the voltage acquisition resolution is 0.1 mu V, and the Seebeck coefficient measurement error is less than 2%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of testing the thermoelectric properties of semiconductor materials, and particularly to a device for measuring the Seebeck coefficient of a bismuth telluride sheet. BACKGROUND

[0002] Bismuth telluride (Bi2Te3) is the best thermoelectric material in room temperature zone, and its Seebeck coefficient is a core parameter for measuring the thermoelectric conversion efficiency of the material. The existing testing method has three technical bottlenecks:

[0003] 1. Multi-point separate measurement error: the traditional four-probe method needs to measure voltage and temperature respectively, and the spatial difference leads to a decrease in data correlation;

[0004] 2. Contact damage risk: rigid probes are easy to damage the fragile bismuth telluride sheet, causing measurement deviation;

[0005] 3. Self-interference of thermocouple: the Seebeck effect of the thermocouple itself introduces measurement error.

[0006] The patent with publication number CN218003305U proposes a Seebeck coefficient testing device for thermoelectric materials, which uses a rigid conductive probe of four-probe method to directly abut the sample, which is easy to cause damage to the sheet material; the temperature detection member is arranged separately from the conductive probe, and the temperature and pressure signals are collected asynchronously, there is a multi-point measurement error, and the problems of synchronous measurement and flexible contact are not solved. The patent with publication number CN105628732A proposes a device and method for measuring Seebeck coefficient, which uses a four-probe and thermocouple separated design, and the temperature collection (thermocouple) and voltage collection (probe) belong to different points, there is a spatial sampling deviation, and synchronous temperature and pressure measurement at the same point cannot be achieved, and the data correlation is insufficient; the probe applies pressure through a spring, which can adjust the tightness but does not form a flexible contact structure suitable for brittle materials, and there is still a risk of pressure damage to the bismuth telluride sheet. The patent with publication number CN103901071A proposes a method and testing device for testing the Seebeck coefficient of film-shaped thermoelectric materials, which designs a wire electrode line contact structure for film-shaped materials, and sets a thermocouple and a wire electrode at the high-temperature end and the low-temperature end respectively, and the temperature and pressure collection points are separated, which cannot avoid the measurement deviation caused by spatial difference. The patent with publication number CN116038491A proposes a simple testing device for Seebeck coefficient of thermoelectric materials, which focuses on the automatic polishing function of the testing assembly, and the testing head and the sample are in rigid contact without designing a flexible buffer structure to protect brittle bismuth telluride sheet; the temperature and voltage collection rely on separate testing assemblies, and there is no self-interference compensation design for the thermocouple, so the measurement accuracy is limited. The patent with publication number CN215768351U proposes a nano thermoelectric material Seebeck coefficient testing device, which only adjusts the distance of the support seat to adapt to different lengths of samples, and the electrodes and thermocouples are arranged rigidly, which is easy to cause damage to the sheet material; the electrodes and thermocouples at the high-temperature end and the low-temperature end are arranged separately, and the temperature and pressure signals are collected asynchronously, which has a multi-point measurement error. SUMMARY

[0007] The purpose of the present application is to provide a bismuth telluride sheet Seebeck coefficient measuring device, which solves the problem that the prior art cannot accurately and non-destructively measure the Seebeck coefficient of bismuth telluride sheet, and realizes the integrated design of synchronous measurement, flexible contact and anti-interference compensation.

[0008] The technical solution of the present application is:

[0009] A bismuth telluride sheet Seebeck coefficient measuring device, the device comprises a flexible measuring device and a data acquisition system, the data acquisition system is provided with a multimeter and a programmable power supply, the flexible measuring device is connected to the input end of the multimeter through a signal cable to transmit the temperature and pressure signals of the thermocouple, and the flexible measuring device is connected to the output end of the programmable power supply through a power supply cable to receive the square wave current required by the heating sheet; the multimeter and the programmable power supply are respectively connected to a computer through communication cables, and are connected with the computer to realize data processing.

[0010] The flexible measuring device is provided with a box body, a heating sheet fixing cover plate, heating sheets, thermocouples, thermocouple sleeves, a fixing frame, guide rods, linear bearings, springs, a fixing seat, cover plate through holes, sliding sleeves, fixing sleeves, screws, positioning grooves and annular bosses, and the specific structure is as follows:

[0011] The heating sheet fixing cover plate is arranged on the fixing seat at the top of the box body, the upper end surface of the fixing seat is provided with a T-shaped positioning groove composed of a transverse groove and a longitudinal groove, the depth of the transverse groove is smaller than that of the longitudinal groove, two heating sheets are arranged side by side in the longitudinal groove, and the upper end surfaces of the two heating sheets are flush with the bottom surface of the transverse groove; the heating sheet fixing cover plate is a T-shaped plate structure matched with the shape of the positioning groove, the heating sheet fixing cover plate is embedded in the positioning groove and pressed on the top of the heating sheets, so that the heating sheets are fixed on the top of the box body through the heating sheet fixing cover plate, the cover plate through holes are arranged in the corresponding positions of the heating sheet fixing cover plate and the heating sheets to expose the two heating sheets, and a corresponding thermocouple is arranged above each heating sheet, the measured bismuth telluride sheet material is arranged on the top of the exposed part of the two heating sheets and between the heating sheets and the thermocouples.

[0012] Each thermocouple penetrates through a thermocouple sleeve, the thermocouple sleeve is sleeved with a sliding sleeve and a fixing sleeve from top to bottom, the sliding sleeve is in sliding fit with the thermocouple sleeve and is fixedly connected with the thermocouple sleeve through a screw, the thermocouple sleeve is provided with an annular boss at the end, and a spring is arranged between the fixing sleeve and the annular boss, the upper end of the spring abuts against the bottom of the fixing sleeve, and the lower end of the spring is in close contact with the annular boss.

[0013] The fixing frame is provided with first and second fixing plates which are parallel to each other, two guide rods are symmetrically arranged at the two sides of the longitudinal groove of the fixing seat, the guide rods are vertically fastened to the top of the fixing seat of the box body, the first and second fixing plates are sleeved with linear bearings on the guide rods, the sliding sleeve on each thermocouple sleeve is connected with the first fixing plate, and the fixing sleeve on each thermocouple sleeve is connected with the second fixing plate.

[0014] The bismuth telluride sheet material Seebeck coefficient measuring device, the box body is used as a device carrier, the heating sheet fixing cover plate is arranged on the top of the box body through the fixing seat, and the side wall of the box body is provided with heat dissipation holes.

[0015] The bismuth telluride sheet material Seebeck coefficient measuring device, the elastic clamping mechanism is composed of a fixing frame, guide rods, linear bearings and springs, the lower ends of the two guide rods are connected with the fixing seat at the top of the box body in a vertical mode through fastening threads, the axis of the guide rod is perpendicular to the plane of the heating sheet fixing cover plate, the sliding of the fixing frame is ensured to be stable, the two linear bearings are fixed at the through holes of the first and second fixing plates, the guide rod penetrates through the linear bearings, and the two thermocouples are connected with the fixing frame through the thermocouple sleeves; when the measured bismuth telluride sheet material is not placed, the spring is in a pre-compressed state, and the compression amount is 3-10 mm; after the measured bismuth telluride sheet material is placed, the spring is further compressed to 5-7 mm, so that the flexible contact of the thermocouples and the measured bismuth telluride sheet material is realized.

[0016] The thermocouple is a K type armored thermocouple, and the outer diameter is less than or equal to 1.5 mm, and the thermocouple has temperature sensing and voltage signal acquisition functions.

[0017] The thermocouple of the bismuth telluride sheet material Seebeck coefficient measuring device passes through the thermocouple sleeve and contacts the measured bismuth telluride sheet material, the thermocouple sleeve provides directional support for the thermocouple, and the annular boss at the end of the thermocouple sleeve provides support for spring compression; the heating sheets are symmetrically arranged, the center distance between the two heating sheets is greater than or equal to 10 mm, so as to adapt to the bismuth telluride sheet material with a thickness of less than or equal to 5 mm and a diameter of less than or equal to 30 mm, and the positive and negative poles of the programmable power supply are alternately connected.

[0018] The heating sheet of the bismuth telluride sheet material Seebeck coefficient measuring device is a ceramic-based Pt resistance heating sheet, and the power is 10-50 W / sheet, and the self-heating effect can be eliminated when the reverse current is passed.

[0019] The bismuth telluride sheet material Seebeck coefficient measuring device, the multimeter synchronously collects the thermocouple voltage signal and the measured bismuth telluride sheet material temperature signal, the programmable power supply outputs square wave current with a frequency of 1-5 Hz and an amplitude of 0-5 A, and is used for heating sheet temperature control and thermocouple self-compensation reduction.

[0020] The data acquisition system of the bismuth telluride sheet material Seebeck coefficient measuring device fits the temperature-voltage curve by the least square method, and calculates the Seebeck coefficient.

[0021] The flexible measuring device of the bismuth telluride sheet material Seebeck coefficient measuring device is selected to be placed in a vacuum box or an inert gas box for testing, so as to reduce the interference of external environmental factors.

[0022] The working principle of the present application is as follows:

[0023] In view of the problems of multi-point separation measurement error, contact damage risk, thermocouple self-interference and the like in the prior art, the present application takes flexible contact, synchronous sensing and reverse compensation as the core, and fully considers the brittleness of bismuth telluride sheet material and the thermoelectric characteristics in the room temperature zone for design.

[0024] 1. Flexible contact mechanism: manually lift the fixing frame → place the bismuth telluride sheet material into the positioning groove above the heating sheet → release the fixing frame → spring compression 5-7 mm → through the elastic force to make the two thermocouple probes form stable and non-damaging flexible contact with the measured bismuth telluride sheet material.

[0025] 2. Temperature difference establishment process: the programmable power supply alternately outputs forward / reverse current, when the forward power supply, the left heating sheet is heated, and the right heating sheet is cooled, to establish a stable temperature difference ΔT at both ends of the measured bismuth telluride sheet material; when the reverse power supply, the electromotive force generated by the reverse current offsets the Seebeck signal generated by the temperature difference of the thermocouple itself.

[0026] 3, Self-heating effect compensation principle: thermocouple itself exists Seebeck coefficient ), which will cause the measurement voltage ; through the programmable power reverse power supply to make the thermocouple generate reverse electromotive force , the final net voltage is , the net voltage of self-interference signal is offset.

[0027] 4, Data acquisition strategy: thermocouple is used as temperature sensor and voltage signal lead, and the temperature (T) of the measured bismuth telluride sheet and the output voltage (V) of the thermocouple are collected synchronously; the formula is used to calculate the Seebeck coefficient, and the system error is further eliminated by averaging the data of multiple forward / reverse power supply cycles.

[0028] In the above formula, V measured is the total voltage (μV) measured, S sample is the Seebeck coefficient (μV / ℃) of the measured bismuth telluride sheet, ΔT is the temperature difference (℃) between the two ends of the measured bismuth telluride sheet, S TC is the temperature difference (℃) between the two ends of the thermocouple itself, ΔT TC is the temperature difference (℃) between the two ends of the thermocouple itself, V reverse is the reverse compensation electromotive force (μV), V net is the net voltage (μV) after compensation, S is the final measured bismuth telluride sheet Seebeck coefficient (μV / ℃), and ΔV is the voltage difference (corresponding to V net , that is, the voltage change of the two ends of the bismuth telluride sheet).

[0029] The advantages and beneficial effects of the present application are:

[0030] 1, Single point synchronous measurement: through the integrated temperature and pressure acquisition design of thermocouple, the thermocouple has the functions of temperature sensing and voltage acquisition, and millisecond level synchronous sampling of the same point is realized; the space sampling deviation of the traditional method is eliminated, and the temperature-voltage correlation is significantly improved.

[0031] 2, Anti-interference design: double heating sheet reverse power supply provides thermocouple self-compensation function, effectively eliminates the error introduced by the Seebeck effect of the thermocouple itself, eliminates self-interference, the measurement result is more accurate, combined with least square method data fitting, the measurement error is less than 2%.

[0032] 3. Flexible contact protection: The elastic clamping mechanism formed by the combination of spring and linear bearing can adjust the contact pressure according to the characteristics of the sheet material. The flexible clamping mechanism realizes the flexible contact between the thermocouple and the sample, avoiding rigid damage. The adjustable spring compression makes the contact pressure between the thermocouple and the bismuth telluride sheet material under test adjustable, avoiding brittle fracture of the bismuth telluride sheet material and realizing non-destructive testing. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 : Overall diagram of the Seebeck coefficient measurement system.

[0035] Figure 2 : Structural diagram of the flexible measuring device.

[0036] Figure 3 : Enlarged view of the flexible contact structure.

[0037] Figure 4 : Hollow structure diagram of double heating elements.

[0038] Labeling Explanation: 1-Flexible Measuring Device, 2-Multimeter, 3-Programmable Power Supply, 4-Computer, 11-Box, 12-Heating Element Fixing Cover, 13-Heating Element, 14-Thermocouple, 15-Thermocouple Sheath, 16-Fixing Frame, 17-Guide Rod, 18-Linear Bearing, 19-Spring, 110-First Fixing Plate, 111-Second Fixing Plate, 112-Fixing Seat, 113-Covering Plate Through Hole, 114-Sliding Sleeve, 115-Fixing Sleeve, 116-Screw, 117-Positioning Groove, 118-Transverse Groove, 119-Longitudinal Groove, 120-Annular Boss. Detailed Implementation

[0039] like Figures 1-4 As shown, this invention proposes a Seebeck coefficient measuring device for bismuth telluride flakes, mainly comprising a flexible measuring device 1 and a data acquisition system. The data acquisition system is equipped with a multimeter 2 and a programmable power supply 3. The flexible measuring device 1 is connected to the input terminal of the multimeter 2 via a signal cable to transmit the temperature and pressure signals of the thermocouple 14. The flexible measuring device 1 is connected to the output terminal of the programmable power supply 3 via a power supply cable to receive the square wave current required by the heating element. The multimeter 2 and the programmable power supply 3 are respectively connected to a computer 4 via communication cables and are connected to the computer 4 to realize data processing.

[0040] The flexible measuring device 1 includes a housing 11, a heating element fixing cover plate 12, a heating element 13, a thermocouple 14, a thermocouple sleeve 15, a fixing frame 16 (first fixing plate 110, second fixing plate 111), a guide rod 17, a linear bearing 18, a spring 19, a fixing seat 112, a cover plate through hole 113, a sliding sleeve 114, a fixing sleeve 115, a screw 116, a positioning groove 117 (transverse groove 118, longitudinal groove 119), and an annular boss 120. The specific structure is as follows:

[0041] The heating element fixing cover 12 is mounted on the fixing seat 112 on the top of the housing 11. The upper end face of the fixing seat 112 has a T-shaped positioning groove 117 composed of a transverse groove 118 and a longitudinal groove 119. The depth of the transverse groove 118 is less than the depth of the longitudinal groove 119. Two heating elements 13 are placed side by side in the longitudinal groove 119, and the upper end faces of the two heating elements 13 are flush with the bottom surface of the transverse groove 118. The heating element fixing cover 12 is T-shaped and matches the shape of the positioning groove 117. The heating element fixing cover 12 is embedded in the positioning groove 117 and pressed on the top of the heating element 13, so that the heating element 13 is fixed to the top of the box 11 through the heating element fixing cover 12. The heating element fixing cover 12 and the heating element 13 have corresponding cover plate through holes 113 to expose two heating elements 13. Each heating element 13 is provided with a corresponding thermocouple 14 above it. The bismuth telluride sheet to be tested is placed on the top of the exposed part of the two heating elements 13, between the heating element 13 and the thermocouple 14.

[0042] Each thermocouple 14 passes through the thermocouple sheath 15. The thermocouple sheath 15 is fitted with a sliding sleeve 114 and a fixed sleeve 115 on its upper and lower sides. The sliding sleeve 114 slides with the thermocouple sheath 15 and is fixedly connected to the thermocouple sheath 15 by screws 116. The thermocouple sheath 15 has an annular boss 120 at its end. A spring 19 is provided between the fixed sleeve 115 and the annular boss 120. The upper end of the spring 19 abuts against the bottom of the fixed sleeve 115, and the lower end of the spring 19 is in close contact with the annular boss 120.

[0043] The mounting bracket 16 is provided with a first fixing plate 110 and a second fixing plate 111 that are parallel to each other. Two guide rods 17 are symmetrically arranged on both sides of the end of the longitudinal groove 119 of the mounting base 112. The guide rods 17 are vertically fastened to the top of the mounting base 112 of the housing 11. The first fixing plate 110 and the second fixing plate 111 are sleeved on the guide rods 17 through linear bearings 18. The sliding sleeve 114 on each thermocouple sheath 15 is connected to the first fixing plate 110, and the fixing sleeve 115 on each thermocouple sheath 15 is connected to the second fixing plate 111.

[0044] 1. Mechanical support system: The housing 11 serves as the carrier of the device. The top is equipped with a heating element fixing cover 12 via a fixing seat 112, and the side wall is provided with heat dissipation holes. The elastic clamping mechanism consists of a fixing frame 16, a guide rod 17, a linear bearing 18, and a spring 19, which realizes flexible contact between the thermocouple 14 and the bismuth telluride sheet material to be tested.

[0045] 2. Sensing System: Thermocouple 14 passes through thermocouple sheath 15 and contacts the bismuth telluride sheet being tested. Thermocouple sheath 15 provides guiding support for thermocouple 14. The annular boss 120 at the end of thermocouple sheath 15 provides support for the compression of spring 19. Heating elements 13 are symmetrically arranged with a spacing of ≥10mm. Temperature difference control is achieved through programmable power supply 3. Thermocouple 14 has both temperature sensing and voltage signal acquisition functions.

[0046] 3. Data acquisition system: A four-channel data acquisition card synchronously acquires thermocouple voltage (μV level) and the temperature (°C) of the bismuth telluride sheet being tested; Computer 4 runs LabVIEW program to fit Seebeck coefficients using the least squares method.

[0047] The communication port of multimeter 2 is connected to the corresponding interface of computer 4 to achieve bidirectional data transmission; the communication port of programmable power supply 3 is connected to the corresponding interface of computer 4 to achieve the issuance of control commands and the return of status information. Computer 4 receives the raw temperature sequence (T) and voltage sequence (V) data transmitted by multimeter 2, and sends acquisition commands for sampling frequency and range selection to multimeter 2. The input terminal of multimeter 2 is connected to the signal leads of the two thermocouples 14 in flexible measuring device 1 via signal cables. Multimeter 2 receives the temperature and voltage signals transmitted by thermocouples 14 in flexible measuring device 1, and then converts the analog signals into digital signals before transmitting them to the computer. Computer 4 receives the current output current and working status feedback information returned by programmable power supply 3, and sends control commands for current amplitude, frequency, and forward / reverse power supply switching to programmable power supply 3. The output terminal of programmable power supply 3 needs to be connected to the dual heating element inside flexible measuring device 1 via wires. Programmable power supply 3 outputs a square wave current with a set frequency and amplitude to the dual heating element of flexible measuring device 1 to achieve heating / cooling and reverse compensation of the heating element.

[0048] In practice, the measurement steps for the Seebeck coefficient are as follows:

[0049] 1. Sample installation: Place the bismuth telluride sheet with a thickness of ≤5mm into the positioning groove 117 of the heating element fixing cover plate 12, so that the bismuth telluride sheet is in full contact with the two heating elements 13;

[0050] 2. Temperature difference control: Set the heating power (10~20W), and maintain ΔT=1~10℃ through LabVIEW program and programmable power supply 3;

[0051] 3. Data Acquisition: Start the data acquisition card of multimeter 2 and record 10 sets of forward / reverse power supply cycle data;

[0052] 4. Result Calculation: The software on computer 4 automatically removes outliers and outputs the average Seebeck coefficient and uncertainty.

[0053] Example

[0054] 1. Testing Process

[0055] Sample loading: Manually lift the fixing frame 10mm high, place the bismuth telluride disc with a thickness of 1mm and a diameter of 30mm into the positioning groove of the heating element fixing cover plate, loosen the fixing frame to compress the spring by 5mm, so that the thermocouple is in full contact with the bismuth telluride disc;

[0056] Temperature balance: Set the heating element power (e.g., 20W), and stabilize the temperature difference to ±0.5℃ using LabVIEW program and programmable power supply control;

[0057] Data acquisition: The multimeter simultaneously acquires thermocouple voltage (ΔV) and bismuth telluride wafer temperature (ΔT); sampling frequency 5Hz, continuous acquisition for 240 seconds;

[0058] Data processing:

[0059] LabVIEW Algorithm Example (Least Squares Fitting)

[0060] / / Temperature sequence (°C): T = [25.1, 30.2, 35.4, ...];

[0061] / / Net voltage sequence after reverse compensation (μV): V = [0.8, 1.2, 1.6, ...];

[0062] / / Least squares method for fitting the linear relationship between temperature and voltage (1 represents first-order linear fitting): p = polyfit(T,V, 1);

[0063] / / The slope of the fitted line p(1) is the Seebeck coefficient (μV / ℃) Seebeck_coefficient = p(1).

[0064] 2. Key technology verification

[0065] Synchronization test: Compared with the traditional discrete probe method, the temperature-voltage signal delay of this device is <5ms;

[0066] Flexible contact verification: repeated loading test (1000 times), thermocouple indentation depth < 0.02 mm;

[0067] Anti-interference verification: After reverse heating compensation, the error introduced by the self-heating effect is <0.3%.

[0068] 3. Performance Verification

[0069] Temperature control accuracy: ±0.1℃ (25℃) environment;

[0070] Voltage resolution: 0.1μV (6½-digit digital multimeter);

[0071] Seebeck coefficient measurement error: <2% (compared to NIST standard samples).

[0072] 3. Application Effect

[0073] High precision: Seebeck coefficient measurement error <2% (traditional method error ≥5%);

[0074] High efficiency: Single test time ≤ 10 minutes (traditional methods ≥ 20 minutes);

[0075] Non-destructive testing: Elastic contact avoids material damage, suitable for brittle bismuth telluride sheets;

[0076] Self-compensation function: Eliminates interference from the thermocouple's own Seebeck effect.

[0077] The results show that the device of this invention achieves accurate measurement of the Seebeck coefficient through a three-in-one design of "flexible contact-synchronous sensing-temperature difference control". The core innovations of the device are: a single-point synchronous sensing system: the thermocouple functions as both temperature and voltage sensors, combined with a four-channel data acquisition card to achieve millisecond-level synchronous sampling at the same point; an elastic contact mechanism: a combination of springs and linear bearings forms a flexible connection, avoiding material damage or signal distortion caused by rigid contact; and an anti-interference heating structure: the dual heating elements with reverse power supply design eliminate the Seebeck effect inherent in the thermocouple, and the hollow design ensures effective establishment of a temperature difference. Actual measurements show that the device has a temperature control accuracy of ±0.1℃, a voltage acquisition resolution of 0.1μV, and a Seebeck coefficient measurement error of <2%.

Claims

1. A device for measuring the Seebeck coefficient of bismuth telluride flakes, characterized in that, The device includes a flexible measuring device and a data acquisition system. The data acquisition system is equipped with a multimeter and a programmable power supply. The flexible measuring device is connected to the input terminal of the multimeter via a signal cable to transmit the temperature and pressure signals of the thermocouple. The flexible measuring device is connected to the output terminal of the programmable power supply via a power supply cable to receive the square wave current required by the heating element. The multimeter and the programmable power supply are connected to the computer via communication cables and are connected to the computer to realize data processing. The flexible measuring device includes a housing, a heating element fixing cover, a heating element, a thermocouple, a thermocouple sleeve, a fixing frame, a guide rod, a linear bearing, a spring, a fixing seat, a cover plate through hole, a sliding sleeve, a fixing sleeve, screws, a positioning groove, and an annular boss. The specific structure is as follows: The heating element fixing cover is set on the fixing seat on the top of the box. The upper end face of the fixing seat is opened with a T-shaped positioning groove composed of a transverse groove and a longitudinal groove. The depth of the transverse groove is less than the depth of the longitudinal groove. Two heating elements are placed side by side in the longitudinal groove, and the upper end face of the two heating elements is flush with the bottom surface of the transverse groove. The heating element fixing cover is a T-shaped plate structure that matches the shape of the positioning groove. The heating element fixing cover is embedded in the positioning groove and presses on the top of the heating element, so that the heating element is fixed to the top of the box through the heating element fixing cover. The heating element fixing cover has a cover plate through hole at the corresponding position of the heating element to expose the two heating elements. A corresponding thermocouple is provided above each heating element. The bismuth telluride sheet to be tested is placed on the top of the exposed part of the two heating elements, between the heating element and the thermocouple. Each thermocouple passes through a thermocouple sheath. A sliding sleeve and a fixed sleeve are fitted on the upper and lower parts of the thermocouple sheath. The sliding sleeve slides with the thermocouple sheath and is fixedly connected to the thermocouple sheath by screws. An annular boss is provided at the end of the thermocouple sheath. A spring is provided between the fixed sleeve and the annular boss. The upper end of the spring abuts against the bottom of the fixed sleeve, and the lower end of the spring is in close contact with the annular boss. The fixing frame has a first fixing plate and a second fixing plate that are parallel to each other. Two guide rods are symmetrically arranged on both sides of the longitudinal groove end of the fixing seat. The guide rods are vertically fastened to the top of the fixing seat of the box. The first fixing plate and the second fixing plate are sleeved on the guide rods through linear bearings. The sliding sleeve on each thermocouple sheath is connected to the first fixing plate, and the fixing sleeve on each thermocouple sheath is connected to the second fixing plate.

2. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The enclosure serves as the carrier of the device. The top is fitted with a heating element and a cover plate, and the side walls of the enclosure have ventilation holes.

3. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The elastic clamping mechanism consists of a fixed frame, guide rods, linear bearings and springs. The lower ends of the two guide rods are vertically connected to the fixed seat on the top of the box through fastening threads. The axis of the guide rods is perpendicular to the plane of the heating element fixing cover plate to ensure that the fixed frame slides smoothly. The two linear bearings are fixed at the through holes of the first fixed plate and the second fixed plate. The guide rods pass through the linear bearings. The two thermocouples are connected to the fixed frame through thermocouple sleeves. When the bismuth telluride sheet to be tested is not placed, the spring is in a pre-compressed state with a compression of 3~10mm; after the bismuth telluride sheet to be tested is placed, the spring is further compressed to 5~7mm, so as to achieve flexible contact between the thermocouple and the bismuth telluride sheet to be tested.

4. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The thermocouple is a type K armored thermocouple with an outer diameter of ≤1.5mm, which has both temperature sensing and voltage signal acquisition functions.

5. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The thermocouple passes through the thermocouple sheath and contacts the bismuth telluride sheet being tested. The thermocouple sheath provides guidance and support for the thermocouple, and the annular boss at the end of the thermocouple sheath provides support for spring compression. The heating elements are symmetrically arranged, with a center-to-center distance of ≥10mm between the two heating elements to accommodate bismuth telluride sheets with a thickness ≤5mm and a diameter ≤30mm. All heating elements are alternately connected to the positive and negative terminals of the programmable power supply.

6. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The heating element is a ceramic-based Pt resistance heating element with a power of 10~50W / element. The self-heating effect can be eliminated when the reverse current is applied.

7. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The multimeter simultaneously acquires the thermocouple voltage signal and the temperature signal of the bismuth telluride sheet being tested. The programmable power supply outputs a square wave current with a frequency of 1~5Hz and an amplitude of 0~5A, which is used for heating element temperature control and thermocouple self-compensation reduction.

8. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The data acquisition system fits the temperature-voltage curve using the least squares method and calculates the Seebeck coefficient.

9. The Seebeck coefficient measuring device for bismuth telluride flakes according to claim 1, characterized in that, The flexible measuring device is tested in a vacuum chamber or an inert gas chamber to reduce interference from external environmental factors.

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