Device for testing conductivity of bismuth telluride crystal bar

Abstract

The invention relates to the technical field of electrical property testing of thermoelectric materials, in particular to a bismuth telluride crystal bar conductivity testing device. According to the invention, an integrated system of a support structure, a double-guide rail assembly, a perforated slide block assembly, a probe unit and high-precision AC resistance test equipment is constructed, wherein the support structure provides a bearing basis; the double-guide-rail assembly guides the bismuth telluride crystal bars to be axially positioned, and the hole opening sliding block assembly is slidably locked to achieve rapid adaptation to the bismuth telluride crystal bars with different lengths within 10 seconds. Spring probes of the probe unit form a four-wire method test loop, a semiconductor polarization effect is eliminated in combination with a high-frequency alternating current test signal, and the spring probes are in elastic contact to ensure that the signal is stable; and by matching with high-precision resistance testing equipment, resistance acquisition and conductivity calculation are completed. According to the invention, the problems of low efficiency, poor precision and complex operation of a traditional mode are solved, rapid and accurate measurement of the conductivity of the bismuth telluride crystal bar is realized, and an efficient testing tool is provided for research, development and production of thermoelectric materials.

Description

Technical Field

[0001] This invention relates to the field of electrical performance testing technology for thermoelectric materials, specifically to a bismuth telluride crystal rod conductivity testing device, which is suitable for testing the conductivity of bismuth telluride (Bi2Te3) crystal rods and can quickly and accurately obtain the conductivity parameters of bismuth telluride crystal rods. Background Technology

[0002] Bismuth telluride-based materials are highly efficient thermoelectric conversion materials in the room temperature range, with key applications in thermoelectric power generation and semiconductor refrigeration. Electrical conductivity is a core indicator characterizing the electrical properties of bismuth telluride crystal rods, and its testing must meet the following technical requirements:

[0003] Anti-interference design: The four-wire method is used to eliminate the interference of contact resistance between the probe and the crystal rod, ensuring that the voltage signal only reflects the resistance of the crystal rod body; AC testing (frequency > 1KHz) is used to avoid the polarization effect of semiconductor materials (DC electric field easily induces carrier accumulation, leading to test deviation).

[0004] Length adaptability: Bismuth telluride crystal rods vary in length (e.g., 50mm~300mm) during production / research, requiring equipment that can quickly adapt to different length specifications.

[0005] However, existing bismuth telluride crystal rod conductivity testing devices have the following drawbacks:

[0006] Inefficient spacing adjustment: Most of them adopt "fixed spacing" or "complex disassembly" design. When changing bar stock, the guide rail / slider needs to be manually disassembled and reassembled. A single adjustment takes more than 5 minutes, resulting in low testing efficiency.

[0007] Insufficient accuracy assurance: The stability of probe contact and the anti-interference capability of the circuit have not been optimized in a targeted manner, making it difficult to meet the high-precision testing requirements of 0.001mΩ level;

[0008] High operational complexity: The reliability of the contact between the probe and the crystal rod depends on repeated manual adjustments, lacks a fast fixing and adaptive structure, and is prone to introducing test errors due to poor contact.

[0009] The patent with publication number CN221926204U proposes an auxiliary device for detecting the conductivity of bismuth telluride crystal rods. This device only addresses the convenience of basic clamping and length adaptation, and has the following key drawbacks: It employs a two-wire testing structure, transmitting signals through left and right clamps and conductive channels, which cannot eliminate contact resistance interference between the clamps and the crystal rod. The testing accuracy is significantly affected by the contact state, making it difficult to meet high-precision testing requirements. The clamps are rigid structures without an adaptive contact mechanism, making them unsuitable for adapting to the microscopic unevenness of the crystal rod surface, easily introducing testing errors due to poor contact. Furthermore, it cannot avoid the polarization effect of bismuth telluride semiconductor materials, and DC testing easily leads to carrier accumulation, further amplifying errors. The patent with publication number CN120507392A proposes a method and device for measuring performance characterization parameters of bismuth telluride-based thermoelectric materials. The core of this method lies in the construction of a test sample set and multi-parameter statistical analysis. However, it has the following limitations: it only focuses on the optimization of the geometric distribution and temperature gradient adjustment of the test samples, without providing solutions to the structural technical problems such as the length adaptation efficiency, contact stability, and circuit anti-interference of the crystal rod test. Although it mentions that conductivity is one of the test parameters, it lacks specific technical means and cannot meet the high-precision testing requirements at the 0.001mΩ level.

[0010] In summary, there is a need to develop a bismuth telluride rod conductivity testing device that combines rapid length adaptation with high-precision four-wire AC testing capability. Summary of the Invention

[0011] The purpose of this invention is to provide a bismuth telluride crystal rod conductivity testing device, which solves the problems of poor length adaptability, insufficient testing accuracy, and cumbersome operation of existing devices, and realizes rapid and accurate measurement of the conductivity of bismuth telluride crystal rods.

[0012] The technical solution of this invention is:

[0013] A bismuth telluride crystal rod conductivity testing device comprises a support structure, a dual-rail assembly, an open-hole slider assembly, a probe unit, and a resistance testing device, as detailed below:

[0014] The supporting structure serves as the load-bearing foundation, comprising a base and supports symmetrically arranged on both sides of the lower surface of the base. The dual-rail assembly includes two parallel rails mounted on the top of the base along the length of the base of the supporting structure, used to guide the axial positioning of the bismuth telluride crystal rod to be tested. The four open-hole sliders of the open-hole slider assembly are placed on the two rails. At the center of the semi-circular groove at the top of each open-hole slider, a probe mounting hole is vertically drilled. The inner diameter of the probe mounting hole matches the outer diameter of the spring probe of the probe unit, and the depth of the probe mounting hole is not less than the effective contact length of the spring probe. The four spring probes are assembled one-to-one into the probe mounting holes of the four open-hole sliders. Among them, two spring probes form a current probe group for passing AC test current; two spring probes form a voltage probe group for collecting voltage signals at both ends of the crystal rod to form a four-wire test circuit. The resistance testing device is connected to the four spring probes through wires, configured to output an AC test signal with a frequency > 1KHz, and has a resistance measurement accuracy of ≥ 0.001mΩ.

[0015] The bismuth telluride crystal rod conductivity testing device has a boss on the inner side of each guide rail that corresponds to the groove on the side of the hole slider. The bosses on the two guide rails are symmetrical, which restricts the movement of the hole slider along the length of the guide rail.

[0016] The bismuth telluride crystal rod conductivity testing device has a semi-circular groove on the top of each open slider for placing the bismuth telluride crystal rod. The semi-circular groove matches the shape of the contact point with the bismuth telluride crystal rod, and the contact point fully supports the bismuth telluride crystal rod. Each open slider has symmetrical grooves on both sides, and each groove is respectively assembled on the boss of a guide rail and is in sliding fit.

[0017] The bismuth telluride crystal rod conductivity testing device has symmetrical fastening screw holes on both sides of each open slider above the groove on the same side. The fastening screws are installed on the outside of the guide rail and correspond one-to-one with the position of the open slider. By tightening the fastening screws through the guide rail and connecting them to the fastening screw holes on the side of the open slider, the open slider is locked and fixed on the guide rail.

[0018] The aforementioned bismuth telluride crystal rod conductivity testing device comprises a spring probe, a spring, and a probe holder, with each spring probe consisting of a needle body, a spring, and a probe holder. The spring-spring-probe holder is mounted in the probe mounting hole at the bottom of the open slider. The needle body passes through the inner hole of the probe holder at the top of the open slider. The needle body is elastically and extensibly assembled inside the probe holder along the axial direction. The spring is sleeved on the outside of the needle body, so that the probe end of the needle body always has an outward preload. The spring is constrained between the inner hole of the probe holder and the needle body. All three are coaxially assembled.

[0019] The aforementioned bismuth telluride crystal rod conductivity testing device has a spring probe body made of high-purity beryllium copper plated with gold, and the spring of the spring probe provides a preload of 5~10N.

[0020] The aforementioned bismuth telluride crystal rod conductivity testing device has an interference fit between the inner diameter of the probe mounting hole and the outer diameter of the spring probe. The depth of the probe mounting hole is not less than the effective contact length of the spring probe, and the effective contact length of the spring probe is the working length of the spring probe's probe end that can elastically extend and retract.

[0021] The bismuth telluride crystal rod conductivity testing device has an opening slider made of non-conductive materials such as bakelite, acrylic, or plastic.

[0022] The bismuth telluride crystal rod conductivity testing device has guide rails made of stainless steel or hard aluminum alloy with nickel plating, and the parallelism of the two guide rails is ≤0.05mm / m.

[0023] The conductivity testing device for bismuth telluride crystal rods has a guide rail spacing that matches the diameter of the bismuth telluride crystal rod, and the guide rail spacing is 1.5 to 2 times the diameter of the bismuth telluride crystal rod.

[0024] The testing principle and process of this invention are as follows:

[0025] 1. Principle of Four-Wire Resistance Measurement

[0026] By establishing independent circuits for "current probe group to pass AC current I (mA)" and "voltage probe group to collect voltage U (mV)," interference from the contact resistance between the probe and the crystal rod is eliminated. The formula for calculating the resistance R (mΩ) of the bismuth telluride crystal rod is as follows: .

[0027] 2. Conductivity Calculation Process

[0028] After measuring the length L (mm, along the axial direction) and diameter d (mm) of the bismuth telluride crystal rod, the conductivity σ is calculated in conjunction with the resistance R:

[0029] Cross-sectional area of ​​crystal rod:

[0030] Electrical conductivity formula: (Unit: S / m)

[0031] This invention employs a sliding adjustment structure with dual guide rails and four-hole sliders, combined with a locking and fixing design, to achieve rapid spacing adjustment of crystal rods of different lengths; it constructs a test circuit using a four-wire method and spring probes, separates the current and voltage acquisition channels, and combines an elastic pre-pressure contact mechanism to eliminate contact resistance interference and adapt to the microstructure of the crystal rod surface.

[0032] The advantages and beneficial effects of this invention are:

[0033] 1. Rapid length adaptation technology

[0034] This invention utilizes a sliding adjustment structure with dual guide rails and four sliders to adjust the spacing of crystal rods of different lengths within 10 seconds: loosen the guide rail fastening screws → push the sliders to the specified spacing → tighten the fastening screws to lock the spacing. Compared to traditional "disassembly" devices, efficiency is significantly improved.

[0035] 2. High-precision four-wire AC testing technology

[0036] Four-wire method: Separates the current and voltage loops, completely eliminating the interference of contact resistance on voltage acquisition, with a test error of <0.5%;

[0037] AC polarization resistance: AC signals with frequencies >1kHz avoid semiconductor polarization effects, achieving DC test errors of over 5% and AC test errors of <1%;

[0038] Spring probe self-adaptive: 5~10N preload ensures stable contact with microscopically uneven surfaces, with contact resistance fluctuation <0.0005mΩ.

[0039] 3. Structural reliability design

[0040] The parallelism of the dual guide rails is ≤0.05mm / m, ensuring the axial positioning accuracy of the crystal rod;

[0041] The opening slider and guide rail are locked with a double locking mechanism of "dovetail groove + screw", and the spacing stability is <0.01mm under vibration environment;

[0042] The spring probe is gold-plated and has an elastic telescopic structure, with a lifespan of ≥100,000 contacts and a long-term contact resistance stability of <0.001mΩ. Attached Figure Description

[0043] 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.

[0044] Figure 1 This is a three-dimensional structural schematic diagram of the bismuth telluride crystal rod conductivity testing device of the present invention.

[0045] Figure 2 This is a schematic diagram of the placement and testing of bismuth telluride crystal rods.

[0046] Figure 3 This is a schematic diagram of the opening slider assembly and probe unit structure.

[0047] In the diagram, 1-support structure (11 base, 12 support); 2-dual guide rail assembly (21 first guide rail, 22 second guide rail); 3-hole slider assembly (31 first hole slider, 32 second hole slider, 33 third hole slider, 34 fourth hole slider, 35 left groove, 36 right groove, 37 semi-circular groove, 38 fastening screw hole, 39 probe mounting hole); 4-probe unit (41 first spring probe, 42 second spring probe, 43 third spring probe, 44 fourth spring probe, 45 probe body, 46 probe seat); 5-resistance testing equipment; 6-bismuth telluride crystal rod; 7-fastening screw. Detailed Implementation

[0048] like Figures 1-3 As shown, the bismuth telluride crystal rod conductivity testing device of the present invention is composed of a support structure 1, a double guide rail assembly 2, an open-hole slider assembly 3, a probe unit 4, and a resistance testing device 5. The functions and connections of each module are as follows:

[0049] 1. Support structure 1, which serves as the foundation for the device, includes: a horizontal plate-shaped base 11 for mounting the dual guide rail assembly 2; supports 12 symmetrically arranged on both sides of the lower surface of the base 11, which are vertically fixed to the base 11 to ensure structural stability; and an axial limiting structure (such as a U-shaped groove or positioning baffle) on the surface of the base 11 to fix the axial position of the bismuth telluride crystal rod 6 and prevent the bismuth telluride crystal rod from shifting during the test.

[0050] 2. The dual-rail assembly 2 includes two parallel high-precision linear rails (first rail 21 and second rail 22), which are installed on the top of the base 11 along the length of the base 11 of the support structure 1 to guide the axial positioning of the bismuth telluride crystal rod 6 to be tested. Each rail has a boss on its inner side that corresponds to the groove on the side of the opening slider. The bosses of the two rails are symmetrical, which restricts the opening slider to move only along the length of the rail. The rails are made of stainless steel or hard aluminum alloy. The rails are hollow in the middle and nickel-plated on the surface to reduce the coefficient of friction, while ensuring straightness and parallelism (the rail spacing is adapted to the diameter of the bismuth telluride crystal rod, usually 1.5 to 2 times the diameter). The parallelism of the two rails is ≤0.05mm / m, ensuring the coaxiality of the bismuth telluride crystal rod when it is placed horizontally, so that the contact points of the four probes are all located on the axial center line of the bismuth telluride crystal rod 6, avoiding errors introduced by contact offset.

[0051] 3. The hole-opening slider assembly 3 is equipped with four hole-opening sliders (first hole-opening slider 31, second hole-opening slider 32, third hole-opening slider 33, and fourth hole-opening slider 34), which, together with the four spring probes of the probe unit 4 (first spring probe 41, second spring probe 42, third spring probe 43, and fourth spring probe 44), form a "two-set four-wire method" test circuit. Specifically, each hole-opening slider has a semi-circular groove 37 at its top for placing the bismuth telluride crystal rod 6. The semi-circular groove 37 matches the shape of the contact point with the bismuth telluride crystal rod 6. The contact position of the rod is designed so that the semi-circular groove 37 can fully support the bismuth telluride crystal rod 6. Each hole-opening slider has symmetrical grooves on both sides (left groove 35, right groove 3). 6) Each groove is fitted onto a boss on a guide rail in a sliding fit. Each open-hole slider has symmetrical fastening screw holes 38 on both sides above the groove on the same side. Fastening screws 7 are installed on the outside of the guide rail and correspond one-to-one with the positions of the open-hole sliders. By tightening the fastening screws 38 through the guide rail and connecting them to the fastening screw holes 38 on the side of the open-hole slider, the open-hole slider is locked and fixed on the guide rail. At the center of the semi-circular groove 37 at the top of each open-hole slider, a stepped probe mounting hole 39 is vertically oriented. The inner diameter of the probe mounting hole 39 is interference-fitted with the outer diameter of the spring probe, and the hole depth is not less than the effective contact length of the spring probe (usually ≥8mm), ensuring the stability of the spring probe installation and the reliability of the electrical connection. The effective contact length of the spring probe is the working length of the spring probe's probe end that can elastically extend and retract. The effective contact length must be greater than 1.2 times the maximum compression of the spring to ensure that the spring probe is always in contact with the surface of the bismuth telluride crystal rod.

[0052] 4. Probe unit 4, comprising 4 spring probes (first spring probe 41, second spring probe 42, third spring probe 43, and fourth spring probe 44). Each spring probe includes a needle body, a spring, and a probe seat, adopting a three-section elastic structure of "needle body-spring-probe seat". The probe seat 46 is installed at the bottom of the opening slider in the probe mounting hole 39. The needle body 45 passes through the inner hole of the probe seat 46 at the top of the opening slider. The needle body 45 can be elastically extended and retracted in the probe seat 46 along the axial direction. The spring is sleeved on the outside of the needle body 45, so that the detection end of the needle body 45 always has an outward preload. The spring is constrained between the inner hole of the probe seat 46 and the needle body 45. The three are coaxially assembled. The needle body 45 is made of high-purity beryllium copper plated with gold (to reduce contact resistance). The spring provides a preload of 5~10N to ensure that the needle body 45 at the spring probe probe end is in close contact with the surface of the bismuth telluride crystal rod 6 (adapting to the microscopic unevenness of the surface of the bismuth telluride crystal rod 6). The four spring probes (first spring probe 41, second spring probe 42, third spring probe 43, and fourth spring probe 44) are divided into two groups according to their functions: the current probe group (2 probes) is used to pass in AC test current, and the voltage probe group (2 probes) is used to collect the voltage signal at both ends of the bismuth telluride crystal rod 6. The two groups of spring probes are arranged at intervals in space (the spacing is ≥ 1 / 3 of the length of the bismuth telluride crystal rod). This spacing design can avoid the influence of electromagnetic interference generated by the current loop on the voltage signal acquisition, ensuring the independence and accuracy of the voltage signal.

[0053] 5. Resistance testing equipment 5, connected to 4 spring probes via wires, has the following core performance characteristics: outputting an AC test signal with a frequency > 1KHz (typical value 5KHz) to suppress the polarization effect of bismuth telluride semiconductors; resistance measurement accuracy ≥ 0.001mΩ, resolution up to 0.0001mΩ, meeting the high-precision testing requirements for low resistance (usually in the mΩ range) of bismuth telluride crystal rods.

[0054] Example

[0055] (I) Assembly and Debugging of the Device

[0056] Construction of support structure 1: Fix the support 12 to the bottom of the base 11 with M6 hexagon socket screws, ensuring that the top surface of the base 11 is level ≤0.05mm / m; install the first guide rail 21 and the second guide rail 22 symmetrically on the top surface of the base 11 with countersunk screws, and use a laser interferometer to check the parallelism of the guide rails. If the error is >0.05mm / m, it needs to be readjusted.

[0057] Installation of the perforated slider assembly 3: The four perforated sliders (first perforated slider 31, second perforated slider 32, third perforated slider 33, and fourth perforated slider 34) are respectively embedded into the grooves formed between the first guide rail 21 and the second guide rail 22, and the left groove 35 and right groove 36 on both sides of each perforated slider slide in cooperation with the corresponding bosses of the first guide rail 21 and the second guide rail 22. M3 socket head cap screws 7 are screwed into the sides of the first guide rail 21 and the second guide rail 22. Use a feeler gauge to check the gap between the perforated slider and the guide rail to ensure smooth sliding.

[0058] Probe unit 4 assembly: Insert the four spring probes (first spring probe 41, second spring probe 42, third spring probe 43, and fourth spring probe 44) into the probe mounting holes 39 of the open slider, with the probe end of the needle body 45 protruding ≥3mm from the upper surface of the slider; tighten the fixing screws of the probe seat 46 (torque 3~5N·m) to ensure that the spring probes do not move axially.

[0059] Connection of resistance testing equipment 5: The current probe (first spring probe 41, second spring probe 42) is connected to the current output terminal (Output+, Output-) of the resistance testing equipment, and the voltage probe (third spring probe 43, fourth spring probe 44) is connected to the voltage acquisition terminal (Sense+, Sense-); set the test frequency to 5KHz, the range to 0.001mΩ~10Ω, and the trigger mode to "automatic".

[0060] (II) Conductivity Testing Procedure

[0061] Positioning and spacing adjustment of bismuth telluride crystal rod 6: Loosen the guide rail fastening screw 7, push the hole slider so that the spring probe spacing is slightly smaller than the length of the bismuth telluride crystal rod 6 to be tested (e.g., if the bismuth telluride crystal rod is 200mm long, adjust the hole slider spacing to 150mm), and tighten the fastening screw 7 after accurate measurement with a ruler; place the bismuth telluride crystal rod 6 horizontally directly above the spring probes, ensuring that the bismuth telluride crystal rod 6 completely presses down on the 4 spring probes.

[0062] Resistance measurement: Click the “Test” button on the device to output a 5KHz AC current (typical value 10mA~100mA, adjustable according to the resistance of the bismuth telluride crystal rod). The device will automatically collect the voltage and calculate the resistance R, and the result will be displayed on the screen in real time.

[0063] Conductivity calculation: Measure the distance L between the two voltage probes using a vernier caliper (accuracy 0.01 mm), and measure the diameter d of the bismuth telluride crystal rod using a micrometer (accuracy 0.001 mm) (average of 3 points on the equatorial plane); substitute the values ​​into the formula. Calculate the conductivity, retaining 3 significant figures.

[0064] (III) Performance Verification Experiment

[0065] Length adaptability test: Bismuth telluride crystal rods with lengths of 50mm, 100mm, 150mm, and 200mm were selected, and the spacing adjustment and resistance tests were performed respectively. The slider adjustment time and test repeatability were recorded.

[0066] Average adjustment time: 8.5 seconds / piece;

[0067] The same bismuth telluride crystal rod was tested repeatedly 10 times, and the standard deviation of conductivity was <5 S / cm.

[0068] Accuracy verification test: Using standard resistors ranging from 0.001Ω to 10Ω to simulate bismuth telluride crystal rods, DC (100Hz) and AC (5KHz) tests were performed respectively.

[0069] DC test error: 1.2%~3.5%;

[0070] AC test error: 0.3%~0.8%, meeting the 0.5% design requirement.

[0071] The results show that this invention innovatively constructs an integrated system consisting of a support structure, a dual-rail assembly, an open-slider assembly, a probe unit, and a high-precision AC resistance testing device. The support structure provides the foundation; the dual-rail assembly guides the axial positioning of the bismuth telluride crystal rod; the open-slider assembly slides and locks, enabling rapid adaptation to bismuth telluride crystal rods of different lengths within 10 seconds; the spring probes of the probe unit form a "four-wire method" test circuit, which, combined with a high-frequency AC test signal, eliminates semiconductor polarization effects, and the elastic contact of the spring probes ensures signal stability; and the high-precision resistance testing device completes resistance acquisition and conductivity calculation. This invention solves the problems of low efficiency, poor accuracy, and complex operation associated with traditional methods, achieving rapid and accurate measurement of the conductivity of bismuth telluride crystal rods, and providing an efficient testing tool for the research and development and production of thermoelectric materials.

Claims

1. A device for testing the conductivity of bismuth telluride crystal rods, characterized in that, It consists of a support structure, a dual guide rail assembly, an opening slider assembly, a probe unit, and a resistance testing device. The specific structure is as follows: The supporting structure serves as the load-bearing foundation, comprising a base and supports symmetrically arranged on both sides of the lower surface of the base. The dual-rail assembly includes two parallel rails mounted on the top of the base along the length of the base of the supporting structure, used to guide the axial positioning of the bismuth telluride crystal rod to be tested. The four open-hole sliders of the open-hole slider assembly are placed on the two rails. At the center of the semi-circular groove at the top of each open-hole slider, a probe mounting hole is vertically drilled. The inner diameter of the probe mounting hole matches the outer diameter of the spring probe of the probe unit, and the depth of the probe mounting hole is not less than the effective contact length of the spring probe. The four spring probes are assembled one-to-one into the probe mounting holes of the four open-hole sliders. Among them, two spring probes form a current probe group for passing AC test current; two spring probes form a voltage probe group for collecting voltage signals at both ends of the crystal rod to form a four-wire test circuit. The resistance testing device is connected to the four spring probes through wires, configured to output an AC test signal with a frequency > 1KHz, and has a resistance measurement accuracy of ≥ 0.001mΩ.

2. The bismuth telluride crystal rod conductivity testing device according to claim 1, characterized in that, Each guide rail has a boss on its inner side that corresponds to the groove on the side of the opening slider. The bosses on the two guide rails are symmetrical, which restricts the movement of the opening slider along the length of the guide rail.

3. The bismuth telluride crystal rod conductivity testing device according to claim 2, characterized in that, Each open slider has a semi-circular groove on its top for placing a bismuth telluride crystal rod. The semi-circular groove matches the shape of the contact point with the bismuth telluride crystal rod, and the contact point fully supports the bismuth telluride crystal rod. Each open slider has symmetrical grooves on both sides, and each groove is fitted onto the boss of a guide rail in a sliding fit.

4. The bismuth telluride crystal rod conductivity testing device according to claim 3, characterized in that, Each perforated slider has symmetrical fastening screw holes on both sides above the groove on the same side. The fastening screws are installed on the outside of the guide rail and correspond one-to-one with the position of the perforated slider. By tightening the fastening screws through the guide rail and connecting them to the fastening screw holes on the side of the perforated slider, the perforated slider is locked and fixed on the guide rail.

5. The conductivity testing device for bismuth telluride crystal rods according to claim 1, characterized in that, Each spring probe consists of a needle body, a spring, and a probe seat, employing a three-section elastic structure of needle body-spring-probe seat. The probe seat is installed at the bottom of the opening slider in the probe mounting hole, and the needle body passes through the inner hole of the probe seat at the top of the opening slider. The needle body is elastically and extensibly assembled inside the probe seat along the axial direction. The spring is sleeved on the outside of the needle body, so that the probe end of the needle body always has an outward preload. The spring is constrained between the inner hole of the probe seat and the needle body, and the three are coaxially assembled.

6. The bismuth telluride crystal rod conductivity testing device according to claim 5, characterized in that, The needle body of the spring probe is made of high-purity beryllium copper plated with gold, and the spring of the spring probe provides a preload of 5~10N.

7. The conductivity testing device for bismuth telluride crystal rods according to claim 1, characterized in that, The inner diameter of the probe mounting hole is interference-fitted with the outer diameter of the spring probe. The depth of the probe mounting hole is not less than the effective contact length of the spring probe. The effective contact length of the spring probe is the working length of the spring probe's probe end that can elastically extend and retract.

8. The conductivity testing device for bismuth telluride crystal rods according to claim 1, characterized in that, The material of the perforated slider is non-conductive materials such as bakelite, acrylic, or plastic.

9. The conductivity testing device for bismuth telluride crystal rods according to claim 1, characterized in that, The guide rails are made of stainless steel or hard aluminum alloy with nickel plating, and the parallelism between the two guide rails is ≤0.05mm / m.

10. The conductivity testing device for bismuth telluride crystal rods according to claim 1, characterized in that, The guide rail spacing is matched with the diameter of the bismuth telluride crystal rod, and the guide rail spacing is 1.5 to 2 times the diameter of the bismuth telluride crystal rod.

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