Micro thermoelectric material ZT value testing device and testing method

Abstract

The invention discloses a micro thermoelectric material ZT value testing device and method, and the device employs a metal wire to connect a heating device with a vacuum insulation electrode fixed on a vacuum flange, enables a temperature control device to control and measure the temperature of the heating device through the vacuum insulation electrode, and obtains the temperature T of a micro thermoelectric material. Meanwhile, alternating current and direct current can be input to the micro thermoelectric material through a metal wire connected with the micro thermoelectric material, so that the ohmic resistance of the micro thermoelectric material and the stable direct current voltage and constant current can be measured, and the thermoelectric figure of merit of the material can be directly obtained; and transmission of a plurality of parameter test errors in a traditional measurement method is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of thermoelectric material performance testing, and in particular relates to a micro thermoelectric material ZT value testing device and a testing method. Background Art

[0002] The thermoelectric figure of merit ZT of thermoelectric materials is usually measured by different equipment to measure the material's electrical conductivity (σ), Seebeck coefficient (α) and thermal conductivity (κ), and the formula ZT = α 2 σT / κ is calculated, where T is the absolute temperature. These parameters can be obtained through standardized equipment such as ZEM-3 thermoelectric potential / conductivity test system and LFA-457 thermal diffusion coefficient test system.

[0003] However, the shape and size of the samples measured by various equipment are not uniform, and it is difficult to measure multiple parameters of the same sample. The only way is to select the same batch of materials and prepare samples according to the test sample size requirements of the test equipment, which leads to batch errors in the measurement results. When measuring the ZT value, the Seebeck coefficient and electrical conductivity are usually measured in the direction parallel to the sample surface using a thermoelectric parameter test system (such as ZEM, LSR, etc.), while the thermal conductivity is measured in the direction perpendicular to the sample surface using a thermal conductivity tester (such as thermal conductivity test equipment from Netzsch, Linseis, TA, etc.). When the material is anisotropic, this measurement method in different directions will cause large errors.

[0004] In addition, the values ​​of different measuring devices have their own errors. The measurement accuracy of high-temperature Seebeck coefficient is not high. The commonly used high-temperature thermoelectric parameter test system (such as Linseis LSR series) measures the Seebeck coefficient with an accuracy of about 7%, which will bring certain errors to the evaluation of thermoelectric conversion efficiency. For example, some scholars believe that the measurement error of material thermal conductivity is generally not less than 10%, and the error of individual parameter measurement is transmitted, resulting in a large error in the final ZT result. Furthermore, the materials suitable for measurement by these devices are usually macroscopic in size, usually in the order of centimeters, and cannot meet the measurement of thermoelectric parameters of materials of millimeters and below. It is powerless to analyze the thermoelectric properties of microscopic materials and test the localized performance of macroscopic materials.

[0005] The patent application with publication number CN215812545U discloses a detector for directly measuring the thermoelectric figure of merit of micro-nano materials, including: a silicon substrate, an oxide insulating layer, a left electrode, a middle electrode, and a right electrode; the oxide insulating layer is formed on the upper layer of the silicon substrate, and the left electrode, the middle electrode, and the right electrode are arranged side by side and symmetrically at intervals on the upper layer of the oxide insulating layer, and the sample is suspended on the left electrode, the middle electrode, and the right electrode; a double H-type suspended micro-nano electrode is prepared by a photolithography-overlay-etching combined process as a sample measurement probe to eliminate the influence of thermal conduction and heat loss between the electrode and the substrate. The sample and the electrode are placed in a high vacuum constant temperature chamber and connected to an external measurement circuit for measurement. The electrode can accurately measure the thermoelectric parameters such as ZT, electrical conductivity, thermal conductivity, Seebeck coefficient, and thermal diffusivity of the same sample at one time. However, the measurement accuracy of the thermoelectric figure of merit of micro-nano materials by the device disclosed in the patent application needs to be improved. Summary of the invention

[0006] The invention provides a micro thermoelectric material ZT value testing device, which can directly and relatively accurately measure the ZT value of the thermoelectric material.

[0007] The present invention discloses a micro thermoelectric material ZT value testing device, comprising:

[0008] A vacuum chamber assembly, the vacuum chamber assembly comprising a vacuum flange, a vacuum chamber and an air inlet and outlet, the vacuum flange being fixed to the top of the vacuum chamber, the air inlet and outlet being arranged at the bottom of the vacuum chamber, and being used for evacuating and inletting air so that the interior of the vacuum chamber assembly is in a vacuum state;

[0009] A metal tube and a plurality of vacuum-insulated electrode columns, wherein the metal tube and the plurality of vacuum-insulated electrode columns penetrate and are sealed and welded to the vacuum flange;

[0010] A heating device, wherein the heating device is connected to the vacuum flange through a metal tube, and the heating device is connected to the corresponding vacuum insulated electrode column through a metal wire, and is used to change the temperature of the micro thermoelectric material and transmit the signal of the temperature T of the micro thermoelectric material to the temperature control device;

[0011] The micro thermoelectric material is located inside the heating device, and the upper and lower end surfaces of the micro thermoelectric material are respectively connected to the corresponding vacuum insulated electrode columns through two metal wires, and thus connected to the current source meter, so that the current source meter can measure the ohmic resistance, stable voltage and constant current of the micro thermoelectric material, and obtain the ZT value of the micro thermoelectric material at temperature T based on the ohmic resistance, voltage and constant current.

[0012] Preferably, the heating device comprises a metal base, a heating plate, a cooling pipeline and a thermocouple;

[0013] The metal base is located inside the vacuum chamber assembly;

[0014] The cooling pipeline is fixed in the metal base and connected to the metal pipe, and is used to cool the metal base through a cooling medium;

[0015] The heating plate is fixed on the outer surface of the metal base and connected to the corresponding vacuum insulated electrode column so as to receive the current controlled by the temperature control meter to heat the metal base;

[0016] The thermocouple is fixed on the outer surface of the metal base and connected to the corresponding vacuum insulated electrode column so as to send the temperature signal to the temperature control device, and the temperature of the metal base, that is, the temperature T of the micro thermoelectric material, is measured and controlled by the temperature control device.

[0017] Preferably, the metal base is made of aluminum or copper.

[0018] Preferably, the metal base is further provided with four insulating terminals, the micro thermoelectric material is located inside the metal base, and four metal wires connected to the micro thermoelectric material are fixed through the corresponding insulating terminals and then connected to the corresponding insulating terminals.

[0019] Preferably, the insulating terminal is made of aluminum nitride or boron nitride.

[0020] Preferably, the vacuum flange is connected to the vacuum chamber via a rubber sealing ring.

[0021] Preferably, the vacuum insulated electrode column is a copper column wrapped with insulating ceramic.

[0022] Preferably, a metal nickel layer is formed on both end surfaces of the sample, and the metal wire connected to each end surface is a metal nickel wire with a diameter of 10-50 microns.

[0023] Preferably, the vacuum chamber assembly further comprises an observation window, which is fixed to the side of the vacuum chamber and located in front of the micro-thermoelectric material, and is used to observe the micro-thermoelectric material and detect the temperature of the micro-thermoelectric material.

[0024] A specific embodiment of the present invention further provides a method for testing the ZT value of a micro thermoelectric material, using the micro thermoelectric material ZT value testing device to test the ZT value of the micro thermoelectric material, comprising:

[0025] The upper and lower end surfaces of the micro thermoelectric material are connected to corresponding vacuum insulation electrode columns through two metal wires respectively, and connected to a current source meter through the corresponding vacuum insulation electrode columns;

[0026] Insert the heating device equipped with the micro thermoelectric material together with the vacuum flange into the vacuum cavity, seal the vacuum cavity with a sealing ring, and use a vacuum pump to extract air from the air inlet and outlet to make the vacuum cavity a vacuum state;

[0027] The temperature of the heating device is controlled by a temperature control device, and the temperature T of the micro-thermoelectric material is measured. Alternating current is passed through four metal wires connected to the micro-thermoelectric material in the normal direction of the AC four-wire current source meter, and the ohmic resistance of the micro-thermoelectric material is measured by the current source meter. Then, the four-wire DC mode is used to measure the voltage across the micro-thermoelectric material in a stable state and the constant current passing through the micro-thermoelectric material by the current source meter. Based on the ohmic resistance, voltage and constant current, the figure of merit ZT of the micro-thermoelectric material at temperature T is obtained.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention can use a metal wire to connect a heating device to a vacuum insulated electrode fixed on a vacuum flange and connected to a temperature control device, so that the temperature control device can control and measure the temperature of the heating device, and then obtain the temperature T of the micro-thermoelectric material. At the same time, alternating current and direct current can be input into the micro-thermoelectric material through the metal wire connected to the micro-thermoelectric material, so as to measure the ohmic resistance, DC voltage and constant current of the micro-thermoelectric material when stable, so as to directly obtain the thermoelectric figure of merit of the material, avoiding the transmission of multiple parameter test errors in traditional measurement methods.

[0030] The end of the metal wire used in the present invention can measure the temperature more accurately, and the thin and long metal wire has less heat loss in a vacuum environment, so that the temperature signal can be transmitted to the temperature control device, so that the temperature control device can more accurately detect the temperature of the micro thermoelectric material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the structure of a micro thermoelectric material ZT value testing device provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0032] The specific embodiment of the present invention utilizes the relationship between the Pletier endothermic process and the temperature difference heat conduction process and the thermoelectric figure of merit in the thermoelectric material to obtain the thermoelectric figure of merit ZT of the sample, i.e., the micro thermoelectric material under different temperature conditions. It can avoid the error transmission of multiple parameter tests in the traditional measurement method, and the method can meet the ZT figure of merit test of thermoelectric materials of millimeter size.

[0033] The micro thermoelectric material ZT value testing device provided by the specific embodiment of the present invention is as follows: Figure 1 As shown, it includes a vacuum chamber assembly, a metal tube, a plurality of vacuum insulated electrode columns and a heating device.

[0034] The vacuum chamber assembly provided in a specific embodiment of the present invention includes a vacuum flange 11, a vacuum chamber 13 and an air inlet and outlet 18. The vacuum flange 11 is fixed to the top of the vacuum chamber 13 and is connected by a rubber sealing ring 12. It can be opened to load samples. The air inlet and outlet 18 is arranged at the bottom of the vacuum chamber 13 and is used for vacuuming and intake of air so that the inside of the vacuum chamber assembly is in a vacuum state.

[0035] The eight vacuum insulated electrode columns 1, 2, 3, 4, 7, 8, 9, 10 provided in the specific embodiment of the present invention are copper columns wrapped with insulating ceramics, and are passed through together with two metal tubes 5, 6 and fixed on the vacuum flange 11 by sealing welding.

[0036] The two metal tubes 5 and 6 provided in the specific embodiment of the present invention are welded to the metal base 15 to provide support for the heating device, which includes the metal base 15, a heating plate 19, an insulating terminal 17, a cooling pipeline and a thermocouple. The material of the metal base 15 can be aluminum or copper. The inside of the metal base 15 has a U-shaped passage shown by the dotted line that communicates with the metal tubes 5 and 6. Cooling water or cooling gas can cool the metal base 15 through the circuit.

[0037] A heating plate 19 is attached to the metal base 15, and current is passed through the electrode columns 2 and 3 to heat the metal base 15. The temperature of the metal base 15 is measured by a thermocouple 14 attached to its surface, and the signal is connected to a temperature control device through the electrode columns 8 and 9. In one embodiment, the temperature control device is a temperature control meter.

[0038] There is an insulating terminal 17 at each of the four corners of the metal base 15. The insulating terminal 17 is made of highly thermally conductive ceramics, such as aluminum nitride or boron nitride. The two ends of the sample 21 are welded with fine metal wires and then suspended in the air. After being fixed by the insulating terminal 17, they are connected to the insulating electrode columns respectively. The metal wire conductors 16 on the same side of the sample are grouped together, connecting electrode columns 1 and 4, or 7 and 10 respectively. The observation window 20 on the vacuum chamber 13 faces the sample and is used to observe the sample state or infrared temperature measurement.

[0039] A specific embodiment of the present invention further provides a method for testing the ZT value of a micro thermoelectric material, using the micro thermoelectric material ZT value testing device to test the ZT value of the micro thermoelectric material, comprising:

[0040] Sample installation: Electroplate the two end faces of the micro thermoelectric material (such as Bi2Te3, SnSe, etc., but not limited to the listed materials) with 3-5um thick metal nickel, and weld metal nickel wire, the diameter of the metal nickel wire is 10-50 microns. The two ends of the nickel wire on the same side of the end face are respectively connected to the electrode columns 1, 4, and the two ends of the nickel wire on the other side are respectively connected to the electrode columns 7, 10. In order to avoid winding short circuits between the metal wires, each metal wire is wound and fixed on four insulating terminals 17, and the distance from the sample to the insulating terminal is greater than 20cm. Insert the metal base with the sample installed together with the flange into the vacuum chamber 13 and seal it with a rubber ring 12. After checking and confirming that the position and state of the sample are normal through the window 20, use a vacuum pump to evacuate air from the air inlet and outlet 18 until the vacuum is no higher than 5*10 -4 Pa.

[0041] Measurement: Use the temperature control head to measure and control the temperature T of the metal base, and connect the vacuum insulated electrode columns 1, 4 and 7, 10 to the current source meter according to the 4-wire method. Use the 100Hz AC mode, that is, 4, 7 pass AC current, 1, 10 pass AC voltage to measure and record the ohmic resistance R of the sample, and then use the four-wire DC mode, that is, 4, 7 pass DC current, 1, 10 pass DC voltage, and perform a voltage-time curve test under a constant small current I (1-5mA). When the system voltage is stable, record the voltage U. According to the formula ZT = U / (I*R)-1, the thermoelectric figure of merit ZT of the sample at temperature T can be obtained.

Claims

1. A micro thermoelectric material ZT value testing device, characterized in that: include: A vacuum chamber assembly, the vacuum chamber assembly comprising a vacuum flange, a vacuum chamber and an air inlet and outlet, the vacuum flange being fixed to the top of the vacuum chamber, the air inlet and outlet being arranged at the bottom of the vacuum chamber, and being used for evacuating and inletting air so that the interior of the vacuum chamber assembly is in a vacuum state; A metal tube and a plurality of vacuum-insulated electrode columns, wherein the metal tube and the plurality of vacuum-insulated electrode columns penetrate and are sealed and welded to the vacuum flange; A heating device, wherein the heating device is connected to the vacuum flange through a metal tube, and the heating device is connected to the corresponding vacuum insulated electrode column through a metal wire, and is used to change the temperature of the micro thermoelectric material and transmit the signal of the temperature T of the micro thermoelectric material to the temperature control device; The micro thermoelectric material is located inside the heating device, and the upper and lower end surfaces of the micro thermoelectric material are respectively connected to the corresponding vacuum insulated electrode columns through two metal wires, and thus connected to the current source meter, so that the current source meter can measure the ohmic resistance, stable voltage and constant current of the micro thermoelectric material, and obtain the ZT value of the micro thermoelectric material at temperature T based on the ohmic resistance, voltage and constant current.

2. The micro thermoelectric material ZT value testing device according to claim 1, characterized in that: The heating device comprises a metal base, a heating plate, a cooling pipeline and a thermocouple; The metal base is located inside the vacuum chamber assembly; The cooling pipeline is fixed in the metal base and connected to the metal pipe, and is used to cool the metal base through a cooling medium; The heating plate is fixed on the outer surface of the metal base and connected to the corresponding vacuum insulated electrode column so as to receive the current controlled by the temperature control meter to heat the metal base; The thermocouple is fixed on the outer surface of the metal base and connected to the corresponding vacuum insulated electrode column so as to send the temperature signal to the temperature control device, and the temperature of the metal base, that is, the temperature T of the micro thermoelectric material, is measured and controlled by the temperature control device.

3. The micro thermoelectric material ZT value testing device according to claim 2, characterized in that: The material of the metal base is aluminum or copper.

4. The micro thermoelectric material ZT value testing device according to claim 2, characterized in that: The metal base is also provided with four insulating terminals. The micro thermoelectric material is located inside the metal base. Four metal wires connected to the micro thermoelectric material are fixed through the corresponding insulating terminals and then connected to the corresponding insulating terminals.

5. The micro thermoelectric material ZT value testing device according to claim 4, characterized in that: The insulating terminal is made of aluminum nitride or boron nitride.

6. The micro thermoelectric material ZT value testing device according to claim 1, characterized in that: The vacuum flange is connected to the vacuum cavity through a rubber sealing ring.

7. The micro thermoelectric material ZT value testing device according to claim 1, characterized in that: The vacuum insulated electrode column is a copper column wrapped by insulating ceramic.

8. The micro thermoelectric material ZT value testing device according to claim 1, characterized in that: A metal nickel layer is formed on both end surfaces of the sample, and a metal wire connected to each end surface is a metal nickel wire with a diameter of 10-50 microns.

9. The micro thermoelectric material ZT value testing device according to claim 1, characterized in that: The vacuum chamber assembly also includes an observation window, which is fixed on the side of the vacuum chamber and located in front of the micro-thermoelectric material, and is used to observe the micro-thermoelectric material and detect the temperature of the micro-thermoelectric material.

10. A method for testing the ZT value of a micro thermoelectric material, characterized in that: The ZT value of a micro-thermoelectric material is tested by using the micro-thermoelectric material ZT value testing device according to any one of claims 1 to 9, comprising: The upper and lower end surfaces of the micro thermoelectric material are connected to corresponding vacuum insulation electrode columns through two metal wires respectively, and connected to a current source meter through the corresponding vacuum insulation electrode columns; Insert the heating device equipped with the micro thermoelectric material together with the vacuum flange into the vacuum cavity, seal the vacuum cavity with a sealing ring, and use a vacuum pump to extract air from the air inlet and outlet to make the vacuum cavity a vacuum state; The temperature of the heating device is controlled by a temperature control device, and the temperature T of the micro-thermoelectric material is measured. Alternating current is passed through four metal wires connected to the micro-thermoelectric material, and the ohmic resistance of the micro-thermoelectric material is measured by a current source meter. Then, the voltage of the micro-thermoelectric material in a stable state and the constant current of the micro-thermoelectric material are measured by a current source meter using a four-wire DC mode. Based on the ohmic resistance, voltage and constant current, the figure of merit ZT of the micro-thermoelectric material at temperature T is obtained.

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