CN113758961A - Horizontal test equipment and method for thermoelectric material Seebeck coefficient and electric conductivity - Google Patents
Horizontal test equipment and method for thermoelectric material Seebeck coefficient and electric conductivity Download PDFInfo
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Abstract
The invention discloses horizontal test equipment and a horizontal test method for a thermoelectric material Seebeck coefficient and electric conductivity. The equipment provided by the invention is provided with two cooling systems, so that the Seebeck coefficient of the material at the temperature lower than the room temperature can be tested, and the heater can be quickly recovered to the lower temperature after the previous test is finished, so that the test of the next sample can be quickly started, the test of the sample is simpler and more convenient, and the efficiency of testing a plurality of samples at a plurality of temperatures is improved. The invention adopts a contact heating mode and a double heating table mode, and can accurately and quickly provide any temperature difference for a test sample. The distance between the two heating blocks can be adjusted, the grooves are formed in the surfaces of the two heating blocks, and the block sample can be placed in the grooves, so that the aim of testing the block sample and the film sample can be fulfilled.
Description
Technical Field
The invention belongs to the field of thermoelectric performance test of materials, and particularly relates to horizontal test equipment and a horizontal test method for a thermoelectric material Seebeck coefficient and electric conductivity.
Background
A thermoelectric material is a material that can convert a temperature difference into a potential difference and vice versa. The working principle is based on the thermoelectric effect of the material: when a temperature difference is established at two ends of the material, current carriers in the material can diffuse from a heat source (high temperature end) to a heat well (low temperature end) due to heat conduction, so that a potential difference is generated, and heat energy is converted into electric energy, namely the principle of thermoelectric power generation; on the contrary, when a voltage is applied to two ends of the thermoelectric material, one end of the material can be cooled and the other end can be heated, so that the potential difference is converted into a temperature difference, namely the principle of thermoelectric cooling. Thermoelectric technology can be used for power and refrigeration in specific applications in the aerospace, military, automotive, electronic, biomedical, etc. industries. For example, the thermoelectric power generation technology can replace a solar cell to provide electric energy for the outer space detector. The thermoelectric device can also be used as an atomic battery for small or large-scale waste heat (for example, human body temperature, engine waste heat, industrial waste heat, etc.) recovery. The thermoelectric refrigeration technology can also be applied to the civil field such as portable refrigerators.
The Seebeck coefficient (Seebeck) is one of the important physical parameters of thermoelectric materials. The existing Seebeck coefficient testing equipment is usually used for a bulk or thin film thermoelectric material. And the sample stage of the block Seebeck coefficient testing instrument is usually vertical, and the design is inconvenient to operate when a sample is placed. In addition, the existing film testing equipment adopts a heating mode of non-contact laser irradiation, and because laser can generate certain influence on the physical properties of materials, errors are easy to generate when materials sensitive to light or different reflectivities are tested. In addition, the existing seebeck coefficient test equipment can only test the seebeck coefficient in a temperature range above normal temperature. While electrical conductivity is another important physical parameter of thermoelectric materials, the prior art fails to achieve the ability to simultaneously test the electrical conductivity of thermoelectric materials at high and low temperatures.
Disclosure of Invention
The invention provides a Seebeck coefficient testing device, which comprises a first testing unit and a second testing unit, wherein the first testing unit and the second testing unit are connected in parallel;
each test unit comprises a heating block, a heating element, a temperature sensor, a temperature measuring probe, a current test probe, a voltage test probe and a cooling system;
the cooling system in each test cell is in contact with the heating block therein for cooling the heating block.
According to an embodiment of the present invention, the first test unit comprises a first heating block, a first heating element, a first temperature sensor, a first temperature measurement probe, a first voltage test probe, and a first cooling system.
According to an embodiment of the invention, the second test unit comprises a second heating block, a second heating element, a second temperature sensor, a second temperature measurement probe, a second voltage test probe and a second cooling system.
According to the embodiment of the invention, the first heating block and the second heating block are used together for bearing a sample to be tested; preferably, the distance between the first heating block and the second heating block can be adjusted according to the size of the sample to be measured. The shape of the heating block is not particularly limited, and the shape is preferably one that facilitates testing of a sample to be tested. Further, the first heating block and the second heating block have the same or different shapes, preferably the same shape, for example, both are rectangular bodies.
According to an embodiment of the invention, the first heating block and the second heating block are horizontally juxtaposed.
According to the embodiment of the invention, the material of the first heating block and the second heating block can be A5052 aluminum alloy, 304 stainless steel, brass or the like.
According to the embodiment of the invention, grooves can be arranged on the surfaces of the first heating block and the second heating block, and the grooves on the two heating blocks are symmetrically arranged and are used for bearing the blocky sample to be tested. Further, the shape of the groove is not particularly limited, and is preferably capable of completely carrying the sample to be measured, and may be, for example, a rectangular groove.
According to the embodiment of the invention, one end of the sample to be detected is in contact with the first heating block, the other end of the sample to be detected is in contact with the second heating block, and the temperatures of the first heating block and the second heating block are not equal. When the temperature T of the first heating block1Is less than the temperature T of the second heating block2And the sample end to be detected in contact with the first heating block is recorded as a cold end, and the sample end to be detected in contact with the second heating block is recorded as a hot end.
According to the embodiment of the invention, the surface of the groove is an insulating surface, so that the sample to be measured and the two heating blocks are heat-conducting but not electrically-conducting.
According to the embodiment of the invention, the test equipment further comprises a voltage data collector, and the first voltage test probe and the second voltage test probe are respectively connected with the voltage data collector. For example, the voltage data collector is an instrument known in the art, such as a voltmeter.
According to the embodiment of the invention, the first voltage testing probe and the second voltage testing probe are arranged above the heating block, and the two voltage testing probes can form ohmic contact with a sample to be tested and are used for testing the voltage at two ends of the sample to be tested. Preferably, the two voltage test probes are kept at a distance, for example, the distance of the two voltage test probes is significantly greater than the distance between the first temperature test probe and the first voltage test probe, and/or significantly greater than the distance between the second temperature test probe and the second voltage test probe. And voltage data obtained by testing is collected by a voltage data collector and transmitted to a computer.
According to an embodiment of the present invention, the testing apparatus further comprises a temperature data acquisition module, and the first temperature measurement probe and the second temperature measurement probe are respectively connected to the temperature data acquisition module.
According to the embodiment of the invention, the first temperature measuring probe and the second temperature measuring probe are respectively contacted with two ends of the sample to be measured, and the surface temperatures of the two ends of the sample to be measured are respectively measured. For example, when the first heating block temperature T1Is less than the temperature T of the second heating block2And the first temperature measuring probe is contacted with the cold end of the sample to be measured, and the second temperature measuring probe is contacted with the hot end of the sample to be measured.
According to an embodiment of the invention, both temperature test probes are located above the heating block. Further, the first temperature test probe is in close proximity to but not in contact with the first voltage test probe and the second temperature test probe is in close proximity to but not in contact with the second voltage test probe. The temperature data acquisition module acquires data of the two temperature test probes and transmits the acquired temperature data to the computer.
According to an embodiment of the present invention, the first voltage test probe, the second voltage test probe, the first temperature measurement probe, and/or the second temperature measurement probe may be immobilized by a support.
According to an embodiment of the invention, the first heating element is for heating a first heating block and the second heating element is for heating a second heating block. Wherein the heating element may be selected from a heating rod, a plate heater, a stick heater, or other forms of heating elements known in the art. The heating element may be arranged inside or outside the heating block, depending on the choice of heating element. For example, when the heating element is a heating rod, a first heating rod is disposed inside the first heating block and a second heating rod is disposed inside the second heating block.
According to an embodiment of the invention, the first temperature sensor is arranged inside the first heating block and the second temperature sensor is arranged inside the second heating block. The first temperature sensor and the second temperature sensor are used for monitoring the temperatures of the first heating block and the second heating block respectively in real time.
According to an embodiment of the present invention, the testing apparatus further includes a temperature controller (e.g., PID temperature controller), the first temperature sensor and the second temperature sensor respectively feed back the temperatures of the heating blocks monitored by the first temperature sensor and the second temperature sensor to the temperature controller, and the temperature controller respectively brings the first heating block and the second heating block to respective set temperatures through PID operation logic and signal feedback.
According to an embodiment of the present invention, the testing device further comprises a pressure sensor disposed at one end of the groove for detecting and controlling the pressure between the sample to be tested and the heating block to ensure that the sample to be tested is in good ohmic contact with the voltage/current testing probe. Wherein the pressure can be obtained by means of hydraulic or pneumatic pressure capable of realizing the pressurization of the screw rotation and the automatic control of a computer.
According to an embodiment of the invention, the test unit further comprises a current test probe; preferably, the first test unit includes a first current test probe and the second test unit includes a second current test probe. Preferably, the first current test probe and the second current test probe are both arranged above the placing position of the sample to be tested of the heating block and used for testing the current at two ends of the sample to be tested.
According to an embodiment of the present invention, the current test probe includes a conductive pin body and an electrode pad optionally connected to the conductive pin body. When the current test probe is a conductive probe body, the current test probe is mainly used for testing a film sample; when the current test probe comprises a conductive needle body and an electrode plate connected with the conductive needle body, the current test probe is mainly used for testing a block sample, and the contact area between the current test probe and the block sample to be tested is increased through the electrode plate, so that better contact is achieved.
According to one embodiment of the present invention, the first current test probe, the first voltage test probe, the second voltage test probe, and the second current test probe are arranged in a linear arrangement, and a distance between tips of each of the probes is equal. Preferably, the first current test probe, the first voltage test probe, the second voltage test probe and the second current test probe are sequentially arranged in a linear manner on a straight line passing through the geometric center of the sample to be measured, and the temperature measurement probe is located at the end side of the sample to be measured. For example, the distance between each probe tip is in millimeters, such as 1-3mm, with 1mm being exemplary.
According to another embodiment of the present invention, the first voltage test probe, the first current test probe, the second voltage test probe and the second current test probe are respectively disposed above four corners of the sample to be tested. Preferably, the two voltage test probes are located on the same side of the sample to be tested, the two current test probes are located on the other same side of the sample to be tested, the first voltage test probe and the second current test probe are arranged in a diagonal manner, and the second voltage test probe and the first current test probe are arranged in a diagonal manner.
According to an embodiment of the present invention, the first cooling system is disposed below the first heating block, the second cooling system is disposed below the second heating block, and the two cooling systems are respectively used for rapidly cooling the heating blocks disposed corresponding thereto. After the sample testing is finished, the temperature of the heating block can be rapidly reduced to a lower temperature through the cooling system, so that the testing device can rapidly (within 2 minutes, for example) enter the next temperature point or the testing section of the next sample.
According to an embodiment of the present invention, the first cooling system and the second cooling system may be any one of water cooling, air cooling, semiconductor refrigeration, dry ice and liquid nitrogen cooling systems. The cooling system is arranged to test the Seebeck coefficient of the sample to be tested under the condition of being lower than room temperature (25 ℃). Further, by selection of a cooling system, such as an industrial refrigerant, dry ice or liquid nitrogen, the refrigeration temperature of the cooling system can be adjusted to-200 ℃, such as-30 ℃ or-196 ℃.
According to the embodiment of the present invention, the shape of the first cooling system and the second cooling system is not particularly limited, and is preferably capable of carrying the corresponding heating blocks. Preferably, the cooling system has the same shape as the heating block.
According to an embodiment of the present invention, the test equipment further comprises a control terminal, for example, the control terminal is a computer. Furthermore, the temperature data acquisition module, the voltage data acquisition unit, the temperature controller and the cooling system are respectively connected with the control end. Further, the connection is a connection means known in the art, such as an electrical connection.
According to an embodiment of the invention, the test apparatus further comprises a sealed enclosure, both test units, or the part of the test unit other than the two cooling systems, being placed inside the sealed enclosure. Further, the sealing cover is provided with a gas inlet and/or a gas outlet for vacuumizing the sealing cover or filling inert gases such as nitrogen, argon and the like into the sealing cover, so that the whole testing device or two testing units are placed in the airtight space. For example, the enclosure may be a glove box or similar device.
According to an embodiment of the present invention, the material of the sample to be tested is a thermoelectric material, such as an inorganic thermoelectric material Bi2Te3，Sb2Te3Bulk and/or thin film samples of PbTe; PEDOT-PSS (organic thermoelectric material); bulk and/or thin film samples of hybrid perovskite materials and the like.
The invention also provides the use of the apparatus for testing the seebeck coefficient and/or the electrical conductivity of a thermoelectric material. Preferably, the thermoelectric material may be in the form of a sheet (e.g., a film) and/or a block. Preferably, the apparatus can test the seebeck coefficient and/or the electrical conductivity of the thermoelectric material above room temperature and below room temperature.
The invention also provides a method for testing the Seebeck coefficient by adopting the equipment, which comprises the following steps:
setting the temperature of the first heating block to T1', the temperature of the second heating block is T2', and T1’≠T2'; placing a sample to be detected on a heating block, measuring the temperature of the cold end and the hot end of the sample to be detected by temperature measuring probes positioned at corresponding positions, and recording the detected temperature as T1And T2And T is1≠T2(ii) a Meanwhile, the cold end and the hot end of the sample to be measured have a temperature difference delta T, so that a potential difference delta V is generated, and the Seebeck coefficient of the material is calculated by a formula S which is delta V/delta T;
the potential difference delta V is obtained by testing the first voltage test probe and the second voltage test probe.
According to an embodiment of the present invention, T1And T1’、T2And T2' are respectively the same or different.
According to an embodiment of the invention, the method further comprises the steps of: after the test is finished, the temperature of the first heating block and the temperature of the second heating block can be rapidly reduced by starting the cooling system, then the temperatures of the two heating blocks are reset, and the Seebeck coefficient at the next temperature is tested; or replacing the sample to be tested and testing the Seebeck coefficient of the next sample to be tested.
According to an embodiment of the present invention, the method for testing seebeck coefficient comprises the steps of:
A1) placing a sample to be detected on a first heating block and a second heating block; preferably, when the sample to be detected is a film sample, the film sample is directly placed on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adjusting the distance between a first heating block and a second heating block according to the size adaptability of the block sample to ensure that the block sample is completely placed in the groove;
A2) contacting a first temperature measurement probe and a first voltage test probe with one end of a sample; the second temperature measuring probe and the second voltage testing probe are contacted with the other end of the sample;
A3) setting the temperature (T) of the first heating blocks before the start of the test1') and the temperature of the second heating block (T)2') and T)1’≠T2’；
A4)T1' and T2' the temperature is different, so that a temperature difference is generated on the surface of the sample; the temperature of the cold end and the hot end of the sample to be measured is measured by temperature measuring probes positioned at the corresponding positions, and the detected temperature is recorded as T1And T2And T is1≠T2；T1And T1' not necessarily identical, T2And T2' are not necessarily the same;
A5) meanwhile, a potential difference delta V is generated between the cold end and the hot end of the sample, and the potential difference delta V is obtained through the test of the first voltage test probe and the second voltage test probe;
A6) temperature T1，T2The data passes through a temperature data acquisition module, potential difference delta V data passes through a voltage data acquisition unit and is respectively transmitted to a computer, and the temperature T of a sample to be measured is obtained through calculation according to a formula S, namely delta V/delta T1Seebeck coefficient under'.
According to an embodiment of the present invention, the method for testing seebeck coefficient may further include the steps of:
A7) after the test is finished, respectively adding T1' and T2' set to other temperature values so that the sample can be tested for seebeck coefficients at different temperatures.
According to an embodiment of the present invention, the method for testing seebeck coefficient may further include the steps of:
A8) linear fitting can be performed according to Δ V and Δ T within a certain temperature range, and the obtained slope is the average value of seebeck coefficients.
The invention also provides a method for testing conductivity by using the device, which comprises the following steps: the voltage of the sample to be tested is measured by a voltage test probe, the current of the sample to be tested is measured by a current test probe, and the conductivity of the sample to be tested is measured according to a linear four-probe method or a Van der Pauw method.
According to the embodiment of the invention, the method for testing the conductivity of the sample to be tested by the linear four-probe method comprises the following steps:
B1) placing a sample to be detected on a first heating block and a second heating block; preferably, when the sample to be detected is a film sample, the film sample is directly placed on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adjusting the distance between a first heating block and a second heating block according to the size adaptability of the block sample to ensure that the block sample is completely placed in the groove;
B2) respectively contacting a first temperature measuring probe and a second temperature probe with two ends of a sample to be tested, and respectively contacting two voltage testing probes and two current testing probes with the sample to be tested; the first current test probe, the first voltage test probe, the second voltage test probe and the second current test probe are arranged in a linear arrangement on a straight line passing through the geometric center of the sample to be tested, and the temperature measurement probe is positioned at the end side of the sample to be tested;
B3) the temperatures of the first heating block and the second heating block are both set to be T.
B4) The first voltage test probe and the second voltage test probe are used for testing the voltage (V) at two ends of the sample to be tested1) The conductive pin body of the first current test probe and the conductive pin body of the second current test probe are used for testing the current (I) at two ends of the sample to be tested1)。
According to an embodiment of the present invention, when the sample to be measured is a film sample, and the thickness of the film is (E.g., about 10 μm) is negligible with respect to the distance between the probing tips (e.g., about 1mm), and can be based on the V obtained from the test1And I1Calculating by combining the formula (1) to obtain the conductivity of the alloy at the temperature T;
wherein σsRepresents the conductivity of the material of the film sample, and δ represents the thickness of the film sample;
according to embodiments of the present invention, when the sample to be tested is a bulk sample, V can be obtained according to the test1And I1Calculating by combining the formula (2) to obtain the conductivity of the alloy at the temperature T;
where σ represents the conductivity of the bulk sample material, A represents the cross-sectional area of the bulk sample, and l represents the length of the bulk sample.
According to an embodiment of the present invention, the method for testing the conductivity of a sample to be tested by the van der pol method comprises the following steps:
C1) placing a sample to be detected on a first heating block and a second heating block; preferably, when the sample to be detected is a film sample, the film sample is directly placed on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adjusting the distance between a first heating block and a second heating block according to the size adaptability of the block sample to ensure that the block sample is completely placed in the groove;
C2) respectively contacting a first temperature measuring probe and a second temperature measuring probe with one end of a sample to be measured, wherein the first voltage measuring probe, the first current measuring probe, the second voltage measuring probe and the second current measuring probe are respectively arranged above four corners of the sample to be measured, the four corners are represented by a, b, c and d, the first voltage measuring probe is positioned at the corner a, the second voltage measuring probe is positioned at the corner b, the second current measuring probe is positioned at the corner c, the first current measuring probe is positioned at the corner d, and the voltage measuring probe and the current measuring probe are respectively contacted with the sample to be measured;
C3) setting the temperatures of the first heating block and the second heating block to be T;
C4) r by test Probeba,cd,Rab,dc,Rdc,ab,Rcd,baAnd Rcb,da,Rbc,ad,Rad,bc,Rda,cb；Rba,cdIndicates that a voltage V is applied across babaAnd the current I at the two ends of cd is obtained by testing under the condition that the end b is a positive electrodecdBy the formula Vba/IcdTo obtain a resistance Rba,cd(ii) a Similarly, calculating to obtain Rab,dc,Rdc,ab,Rcd,b，Rcb,da,Rbc,ad,Rad,bc,Rda,cb；
Calculating the conductivity of the sample to be measured according to the formulas (3) to (6);
calculating to obtain RAAnd RB(ii) a Then obtaining R through calculation according to the formula (5)S：
Calculating to obtain the conductivity of the sample material to be detected at the temperature T by the formula (6);
wherein, sigma represents the conductivity of the sample material to be measured, and delta represents the thickness of the sample to be measured.
Advantageous effects
The invention adopts a transverse horizontal heating block (namely a sample table) form, so that the test of a sample to be tested, especially a film sample, is simpler and more convenient.
By providing two cooling systems, the material can be tested for seebeck coefficient at temperatures below room temperature. Meanwhile, the heating block can be quickly restored to a lower temperature, so that a second sample or a second temperature point can be quickly tested, and the testing efficiency of a plurality of samples and a plurality of temperature points is improved.
The invention adopts a mode of heating a sample to be tested in a contact mode and adopts double heating tables, and can accurately and quickly provide any temperature difference for the sample to be tested. The distance between two heating blocks can be adjusted to the surface is fluted, can put into the recess with the block sample, thereby can satisfy the purpose of test block sample and film sample simultaneously.
Thermoelectric materials generally have an optimal use temperature, i.e., a temperature at which the thermoelectric material has optimal energy conversion efficiency. Therefore, the seebeck coefficient and the electric conductivity of the thermoelectric material at different temperatures need to be tested to judge the optimal application temperature of the material. When the thermoelectric material is applied to refrigeration or a thermoelectric generator is used under the condition that the ambient temperature is lower than the normal temperature, the temperature of one end of the material is lower than the normal temperature, so that the test of the Seebeck coefficient of the material at the non-room low temperature is crucial to the power generation application of the thermoelectric material in the refrigeration field and under the non-room low temperature condition.
The instrument adopts a linear four-probe method and a van der Waals method to test the conductivity of the material, and the two methods can avoid the contact resistance between the material and the test probe, thereby improving the conductivity test accuracy. And the device can simultaneously test the conductivity at high temperature and low temperature.
The Seebeck coefficient test equipment can simultaneously meet the test of the Seebeck coefficient and the electric conductivity of the thin-film and block thermoelectric materials under the conditions of being higher than the room temperature and being lower than the room temperature, has high test precision and high accuracy, and can be used as convenient and comprehensive test equipment in the thermoelectric material industrial field and the scientific research field.
Drawings
FIG. 1 is a schematic perspective view of a test apparatus provided in example 1;
FIG. 2 is a top view of the test apparatus provided in example 1;
FIG. 3 is a front view of the test apparatus provided in embodiment 1;
FIG. 4 is a schematic diagram showing an exploded structure of the test apparatus provided in example 1;
FIG. 5 is a schematic perspective view of the block sample test apparatus provided in example 1;
FIG. 6 is a top view of the block sample testing apparatus provided in example 1;
FIG. 7 is a front view structural view of the block sample being tested by the test apparatus provided in example 1;
FIG. 8 is a schematic diagram of a first current test probe of the test block and a second current test probe of the test block;
FIG. 9 is a schematic perspective view of a four-probe method for measuring the conductivity of a thin film material;
FIG. 10 is a schematic perspective view of a four-probe method for measuring the conductivity of bulk material;
FIG. 11 is a schematic perspective view of a Van der Pauw method for measuring the conductivity of a material;
FIG. 12 is a plot of the four endpoints of the material of FIG. 11 as it tested for conductivity by the Van der Pauw method;
FIG. 13 is a graph of Seebeck coefficient data for samples tested at 5 ℃;
FIG. 14 is a graph of Seebeck coefficient data for samples tested at 25 ℃;
FIG. 15 is a graph of Seebeck coefficient data for samples tested at 60 ℃;
FIG. 16 is a Seebeck coefficient of a sample tested at-20 ℃ to 120 ℃;
FIG. 17 is a block diagram of the connection between the test apparatus and the computer according to embodiment 1.
Reference numerals: 1-a first cooling system, 2-a first heating bar, 3-a first temperature sensor, 4-a first heating block, 5-a thin film sample to be tested, 5 ' -a bulk sample to be tested, 6-a first temperature measuring probe, 7-a first voltage testing probe, 7 ' -a first current testing probe, 7 ' a-a conductive pin body of the first current testing probe, 7 ' b-a conductive plate of the first current testing probe, 8-a second voltage testing probe, 8 ' -a second current testing probe, 8 ' a-a conductive pin body of the second current testing probe, 8 ' b-a conductive plate of the second current testing probe, 9-a second temperature measuring probe, 10-a second heating block, 11-a second temperature sensor, 12-a second heating bar, 13-a second cooling system, 14-a groove, 15-a pressure sensor, 16-a computer, 17-a temperature data acquisition module, 18-a voltage data acquisition device, 19-a first temperature controller and 20-a second temperature controller.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Example 1
The horizontal test device for the Seebeck coefficient of the thermoelectric material, which is shown in figures 1-4, is suitable for testing the thermoelectric thin film material. The test device comprises a first test unit and a second test unit which are connected in parallel.
The first test unit includes a first cooling system 1, a first heating rod 2, a first temperature sensor 3, a first heating block 4, a first temperature measurement probe 6, a first voltage test probe 7, and a second voltage test probe 8.
The second test unit comprises a second cooling system 13, a second heating rod 12, a second temperature sensor 11, a second heating block 10, a second temperature measuring probe 9, a second voltage test probe 8. The first heating block 4 and the second heating block 10 are horizontally arranged in parallel, the first heating block 4 and the second heating block 10 jointly bear the film sample 5 to be tested, namely the first heating block 4 and the second heating block 10 are also sample stages, and the first heating block 4 and the second heating block 10 can move or be fixed, so that the distance between the first heating block 4 and the second heating block 10 can be adjusted according to the size of the film sample.
One end of the film sample to be measured is in contact with the first heating block 4, and the other end is in contact with the second heating block 10. The temperature of the first heating block 4 is set to T1' and the temperature of the second heating block 10 is set to T2' (temperature T)2' and T1' different, by temperature T2' higher than T1' for example and illustrative), the portion of the sample to be measured on the first heating block 4 is called the cold end, and the portion of the sample on the second heating block 10 is called the hot end.
The test equipment further comprises a voltage data collector 18, the first voltage test probe 7 and the second voltage test probe 8 are connected with the voltage data collector 18, ohmic contact is formed between the two voltage test probes and the thin film sample 5 to be tested to test the voltage at two ends of the material, the two voltage test probes are located above the two heating blocks, the two voltage test probes are close to but not in contact with each other, and the voltage data obtained through testing are collected by the voltage data collector 18 and transmitted to a computer.
The test equipment further comprises a temperature data acquisition module 17, and the first temperature measurement probe 6 and the second temperature measurement probe 9 are respectively connected with the temperature data acquisition module 17. First temperature measurement probe 6 and second temperature measurement probe 9 contact with material cold junction and hot junction respectively, test the temperature on material surface, and two temperature test probes all are located the top of two heating blocks, and first temperature test probe 6 is close to with first voltage test probe 7, and second temperature test probe 9 is close to with second voltage test probe 8. The temperature data acquisition module acquires data of the two temperature test probes and transmits the acquired temperature data to the computer.
The first heating rod 2 and the first temperature sensor 3 are both embedded inside the first heating block 4, and the first temperature sensor 3 is close to the first heating rod 2. The second heating rod 12 and the second temperature sensor 11 are embedded inside the second heating block 10, and the second temperature sensor 11 is close to the second heating rod 12. The first temperature sensor 3 and the second temperature sensor 11 monitor the temperatures of the first heating block 4 and the second heating block 10 in real time, and feed the temperatures back to the first temperature controller 19 and the second temperature controller 20, respectively, so that the temperature controllers respectively reach the respective set temperatures of the first heating block and the second heating block through PID operation logic and signal feedback.
A first cooling system 1 is arranged below the first heating block 4, a second cooling system 13 is arranged below the second heating block 10, and the two cooling systems are respectively used for rapidly cooling the temperature of the heating blocks. After the sample test is finished, the temperature of the heating block is rapidly reduced to a lower temperature through the cooling system, so that the test equipment enters the next temperature or test link of the sample to be tested within 2 minutes. The cooling system is water cooling, air cooling, semiconductor refrigeration, dry ice or liquid nitrogen cooling. Due to the cooling system, the temperature of the first heating block and the second heating block can be lower than the room temperature (25 ℃), so that the Seebeck coefficient of the test material under the condition of lower than the room temperature can be tested.
In addition, the surfaces of the first heating block 4 and the second heating block 10 are simultaneously provided with grooves 14, and the grooves on the two heating blocks are symmetrically arranged and are used for bearing the block sample 5' to be tested. The surface of the recess 14 is treated with an insulating material so that the block sample 5' to be tested is thermally conductive but not electrically conductive to the heating block. Fig. 5-7 are schematic structural views of a testing apparatus for carrying a bulk sample to be tested.
As shown in fig. 17, the temperature data acquisition module 17, the voltage data acquisition unit 18, the first temperature controller 19, the second temperature controller 20, and the cooling system are connected to the computer 16, respectively.
Example 2
The test device for simultaneously testing seebeck coefficient and conductivity as shown in fig. 9-11, in addition to comprising the components of the device of example 1, the first test cell further comprises the conductive pin body 7 'a of the first current test probe and the second test cell further comprises the conductive pin body 8' a of the second current test probe.
Fig. 9 is a schematic perspective view of a four-probe method for testing the conductivity of a thin film material, and fig. 10 is a schematic perspective view of a four-probe method for testing the conductivity of a bulk material. In fig. 9, the conductive pin body 7 'a of the first current testing probe, the first voltage testing probe 7, the second voltage testing probe 8, and the conductive pin body 8' a of the second current testing probe are sequentially arranged in a line on a straight line passing through the geometric center of the sample to be tested, and the first temperature measuring probe 6 and the second temperature measuring probe 9 are located at the end side of the sample to be tested. The probe tips of the conductive probe body 7 'a of the first current test probe, the first voltage test probe 7, the second voltage test probe 8 and the conductive probe body 8' a of the second current test probe are equidistant, and the spacing distance is 1 mm.
In fig. 10, a current test probe is used, unlike fig. 9, a first current test probe 7 'and a second current test probe 8' are used when testing a bulk material.
In addition, one end of the recess 14 is provided with a pressure sensor 15 (fig. 10) which is used to detect and control the pressure between the bulk material and the heating block to ensure that a good ohmic contact is maintained between the bulk sample 5 'to be tested and the second amperometric probe 8'. The computer automatically controls the hydraulic or pneumatic pressure by the screw thread rotating pressure.
FIG. 11 is a schematic perspective view of a Van der Pauw method for measuring the conductivity of a material; figure 12 is a plot of the four endpoints of a material as it tested for conductivity by the van der pol method. The conductive pin bodies 7 ' a, 8 ' a and 8 ' a of the first voltage test probe, the first current test probe and the second current test probe are respectively arranged above four corners of a sample to be tested, the four corners are represented by a, b, c and d, the first voltage test probe 7 is positioned at the corner a, the second voltage test probe 8 is positioned at the corner b, the conductive pin body 8 ' a of the second current test probe is positioned at the corner c, and the conductive pin body 7 ' a of the first current test probe is positioned at the corner d.
As shown in fig. 8, the current test probe is composed of two parts: the conductive needle body and the electrode slice connected with the conductive needle body. Specifically, the first current test probe 7 ' is composed of a conductive needle body 7 ' a of the first current test probe and an electrode pad 7 ' b of the first current test probe. A conductive pin body 8 'a of the second current test probe and an electrode plate 8' b of the second current test probe. The contact area between the electrode plate and the block sample is increased, so that better contact is achieved. When the probe is not connected with the electrode plate, the conductive needle body can be independently used as a current test probe for testing the conductivity of the film sample.
Example 3: polycrystalline N-type Bi2Te3Seebeck coefficient test of thin films
Polycrystalline N-type Bi Using the test apparatus provided in example 12Te3The Seebeck coefficient of the films was tested:
A1) polycrystalline N-type Bi2Te3The film is placed on the first heating block and the second heating block, and the distance between the first heating block and the second heating block is adjusted according to the size of the film sample, so that the sample is completely placed on the surface of the heating block;
A2) contacting a first temperature measuring probe and a first voltage testing probe with one end of the film sample, wherein the distance between the probes is less than 1 mm; the second temperature measuring probe and the second voltage testing probe are in contact with the other end of the film sample and the distance between the probes is less than 1 mm.
A3) Setting the temperature (T) of the first heating blocks before the start of the test1') and the temperature of the second heating block (T)2') and T)1’≠T2’；
A4)T1' and T2' to generate a temperature difference on the surface of the sample; the temperature of the cold end and the hot end of the sample to be measured is measured by temperature measuring probes positioned at the corresponding positions, and the detected temperature is recorded as T1And T2And T is1≠T2；T1And T1' not necessarily identical, T2And T2' are not necessarily the same;
A5) meanwhile, a potential difference delta V is generated at the low-temperature end and the high-temperature end of the sample, and the potential difference delta V is obtained by testing the first voltage test probe and the second voltage test probe;
A6) temperature T1，T2The data passes through a temperature data acquisition module, potential difference delta V data passes through a voltage data acquisition unit and is respectively transmitted to a computer, and the temperature T of the film sample is obtained through calculation according to a formula S which is delta V/delta T1Seebeck coefficient under'.
A7) After the test is finished, respectively adding T1' and T2' set to another temperature to test the Seebeck coefficient of the film sample at different temperatures.
A8) Linear fitting can be performed according to Δ V and Δ T within a certain temperature range, and the obtained slope is the average value of seebeck coefficients.
For example, the temperature (T) of the first heating block is set before the test is started1' -25 deg.c) and temperature of the second heating block (T)2' -35 deg.C), the temperature of the sample surface is passed through a first temperature measuring probe (T)123.8 deg.c) and a second temperature measuring probe (T)2Measured 33.4 ℃). Meanwhile, a potential difference Δ V is generated between the low temperature end and the high temperature end of the sample, and the potential difference is measured by the voltmeter through the first voltage test probe 7 and the second voltage test probe 8. Temperature data T1，T2And the potential difference data Δ V ═ 0.0016V is transmitted to a computer, and the seebeck coefficient of the material at 25 ℃ is calculated by the formula S ═ Δ V/Δ T.
As shown in FIG. 13, polycrystalline N-type Bi at 5 ℃2Te3The Seebeck coefficient test chart of the film is used for obtaining the linear fitting R with the Seebeck coefficient value of-144.6 mu V/K20.99431. As shown in FIG. 14, polycrystalline N-type Bi at 25 ℃2Te3The Seebeck coefficient test chart is used for obtaining the R with the Seebeck coefficient value of-134.3 mu V/K and linear fitting20.99555. As shown in FIG. 15, polycrystalline N-type Bi at 60 ℃2Te3The Seebeck coefficient test chart is used for obtaining the linear fitting R with the Seebeck coefficient value of-134.9 mu V/K20.99553. FIG. 16 shows polycrystalline N-type Bi tested at-20 deg.C to 120 deg.C2Te3The seebeck coefficient obtained is shown in table 1. According to Table 1, the error of the Seebeck coefficient of the instrument is less than 2 μ V/K when the instrument tests the same sample at the same temperature.
TABLE 1
Similarly, the testing method of the embodiment is also applicable to the massive sample to be tested.
Example 4: electrical conductivity testing of thermoelectric materials
The conductivity test method is carried out by a linear four-probe method:
using the test apparatus shown in fig. 9-10, the specific test procedure is as follows:
B1) placing a sample to be detected on a first heating block and a second heating block; when the sample to be detected is a film sample, directly placing the film sample on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adaptively adjusting the distance between a first heating block and a second heating block according to the size of the block sample to ensure that the block sample is completely placed in the groove;
B2) the first voltage test probe and the second voltage test probe are used for testing the voltage (V) at two ends of the sample to be tested1) And the conductive pin body of the first current test probe and the conductive pin body of the second current test probe are used for testing the current (I) at two ends of the film or the block1). And in the measuring process, the first current testing probe, the first voltage testing probe, the second voltage testing probe and the second current testing probe are arranged in a linear arrangement on a straight line passing through the geometric center of the sample to be measured, and the distances between the adjacent probes are equal. The temperature measuring probe is positioned at the side of the sample to be measured.
B3) The temperatures of the first heating block and the second heating block are both set to be T.
When the thickness of the film (about 10 μm) is neglected with respect to the distance between the tips (about 1mm), the conductivity of the material is calculated by the following formula:
(1)
wherein sigmasIs the conductivity of the film, and δ is the thickness of the film.
When the sample to be tested is a bulk sample, the conductivity is calculated by the following formula:
(2)
where σ is the conductivity of the bulk, A is the cross-sectional area of the bulk material, and l is the length of the bulk sample.
(II) Van der Pauw method for measuring the conductivity of films and blocks:
using the test apparatus shown in fig. 11-12, the specific test procedure is as follows:
C1) placing a sample to be detected on a first heating block and a second heating block; when the sample to be detected is a film sample, directly placing the film sample on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adaptively adjusting the distance between a first heating block and a second heating block according to the size of the block sample to ensure that the block sample is completely placed in the groove;
C2) the first temperature measuring probe and the second temperature measuring probe are respectively contacted with one end of a sample to be measured,
the conductive pin bodies of the first voltage testing probe, the second voltage testing probe, the first current testing probe and the second current testing probe are simultaneously placed at four corners of the sample and are respectively marked as four corners a, b, c and d on the sample, as shown in fig. 12.
C3) Setting the temperatures of the first heating block and the second heating block to be T;
C4) r is obtained by testing through test probes respectivelyba,cd,Rab,dc,Rdc,ab,Rcd,baAnd Rcb,da,Rbc,ad,Rad,bc,Rda,cb。Rba,cdIndicates that a voltage V is applied across babaAnd the current I at the two ends of cd is obtained by testing under the condition that the end b is a positive electrodecdBy the formula Vba/IcdTo obtain a resistance Rba,cd。Rab,dc,Rdc,ab,Rcd,b，Rcb,da,Rbc,ad,Rad,bc,Rda,cbThe same applies to the calculation method of (1). Then by the formula
(3)
(4)
Calculating to obtain RAAnd RB. And solving the following equation:
(5)
calculating to obtain RS. Then by the formula
(6)
And calculating the conductivity of the material. Where σ is the conductivity and δ is the thickness of the sample.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The device for testing the Seebeck coefficient is characterized by comprising a first testing unit and a second testing unit, wherein the first testing unit and the second testing unit are connected in parallel;
each test unit comprises a heating block, a heating element, a temperature sensor, a temperature measuring probe, a current test probe, a voltage test probe and a cooling system;
the cooling system in each test cell is in contact with the heating block therein for rapidly cooling the heating block.
Preferably, the first test unit comprises a first heating block, a first heating element, a first temperature sensor, a first temperature measurement probe, a first voltage test probe and a first cooling system;
preferably, the second test unit comprises a second heating block, a second heating element, a second temperature sensor, a second temperature measurement probe, a second voltage test probe, and a second cooling system;
preferably, the first heating block and the second heating block are used together for carrying a sample to be tested;
preferably, the distance between the first heating block and the second heating block can be adjusted according to the size of the sample to be measured.
2. The test apparatus of claim 1, wherein the first and second heating blocks are horizontally juxtaposed.
Preferably, the first heating block and the second heating block are made of A5052 aluminum alloy, 304 stainless steel and brass;
preferably, the surfaces of the first heating block and the second heating block are provided with grooves, and the grooves on the two heating blocks are symmetrically arranged and are jointly used for bearing the blocky sample to be tested.
Preferably, one end of the sample to be detected is contacted with the first heating block, the other end of the sample to be detected is contacted with the second heating block, and the temperatures of the first heating block and the second heating block are not equal;
preferably, the groove surface is an insulating surface.
3. The test equipment according to claim 1 or 2, wherein the test equipment further comprises a voltage data collector, and the first voltage test probe and the second voltage test probe are respectively connected with the voltage data collector;
preferably, the first voltage testing probe and the second voltage testing probe are arranged above the heating block, and ohmic contact is formed between the two voltage testing probes and the sample to be tested; preferably, the two voltage test probes are kept at a distance.
Preferably, the test equipment further comprises a temperature acquisition module, and the first temperature measurement probe and the second temperature measurement probe are respectively connected with the temperature data acquisition module;
preferably, the first temperature probe and the second temperature measurement probe are respectively contacted with two ends of a sample to be measured, and respectively measure the surface temperature of the two ends of the sample to be measured;
preferably, both temperature test probes are located above the heating block; preferably, the first temperature test probe is in close proximity to but not in contact with the first voltage test probe and the second temperature test probe is in close proximity to but not in contact with the second voltage test probe;
preferably, the first heating element is for heating a first heating block and the second heating element is for heating a second heating block; preferably, the heating element is selected from a heating rod, a plate heater, a stick heater or other forms of heating elements known in the art;
preferably, the first temperature sensor is arranged inside the first heating block, and the second temperature sensor is arranged inside the second heating block; the first temperature sensor and the second temperature sensor monitor the temperatures of the first heating block and the second heating block in real time;
preferably, the test equipment further comprises a temperature controller, the first temperature sensor and the second temperature sensor respectively feed back the temperatures of the heating blocks monitored by the first temperature sensor and the second temperature sensor to the temperature controller, and the temperature controller respectively enables the first heating block and the second heating block to reach respective set temperatures through PID operation logic and signal feedback;
preferably, the testing device further comprises a pressure sensor, wherein the pressure sensor is arranged at one end of the groove and used for detecting and controlling the pressure between the sample to be tested and the heating block, so that good ohmic contact is kept between the sample to be tested and the voltage/current testing probe;
preferably, the test unit further comprises a current test probe; preferably, the first test unit includes a first current test probe, and the second test unit includes a second current test probe; preferably, the first current test probe and the second current test probe are arranged above the placing position of the sample to be tested of the heating block and used for testing the current at two ends of the sample to be tested;
preferably, the current test probe comprises a conductive pin body and an electrode plate optionally connected with the conductive pin body;
preferably, the test device further comprises a sealed enclosure, and both test units, or the entire device, are placed within the sealed enclosure.
Preferably, the material of the sample to be detected is a thermoelectric material.
4. The test apparatus as claimed in any one of claims 1 to 3, wherein the first current test probe, the first voltage test probe, the second voltage test probe, and the second current test probe are arranged in a linear array, and a distance between tips of each of the probes is equal. Preferably, the first current test probe, the first voltage test probe, the second voltage test probe and the second current test probe are sequentially arranged in a linear manner on a straight line passing through the geometric center of the sample to be measured, and the temperature measurement probe is positioned at the end side of the sample to be measured;
preferably, the distance between each of the probe tips is in millimeters, such as 1-3 mm;
or the first voltage test probe, the first current test probe, the second voltage test probe and the second current test probe are respectively arranged above four corners of the sample to be tested; preferably, the two voltage test probes are positioned on the same side of the sample to be tested, the two current test probes are positioned on the other same side of the sample to be tested, the first voltage test probe and the second current test probe are arranged in a diagonal manner, and the second voltage test probe and the first current test probe are arranged in a diagonal manner;
preferably, the first cooling system is arranged below the first heating block, the second cooling system is arranged below the second heating block, and the two cooling systems are respectively used for rapidly cooling the heating blocks arranged corresponding to the two cooling systems;
preferably, the first cooling system and the second cooling system are any one of water cooling, air cooling, semiconductor refrigeration, dry ice and liquid nitrogen cooling systems;
preferably, the test equipment further comprises a control terminal, for example, the control terminal is a computer. Preferably, the temperature data acquisition module, the voltage data acquisition unit, the temperature controller and the cooling system are respectively connected with the control end.
5. Use of the test device of any one of claims 1-4 for testing the seebeck coefficient and/or the electrical conductivity of a thermoelectric material;
preferably, the thermoelectric material is in the form of a sheet (e.g., film) and/or a block;
preferably, the apparatus tests the thermoelectric material for seebeck coefficient and/or electrical conductivity above room temperature and below room temperature.
6. The method of testing seebeck coefficients with a testing device according to any one of claims 1 to 4, characterized in that it comprises the following steps:
setting the temperature of the first heating block to T1', the temperature of the second heating block is T2', and T1’≠T2'; placing a sample to be detected on a heating block, measuring the temperature of the cold end and the hot end of the sample to be detected by temperature measuring probes positioned at corresponding positions, and recording the detected temperature as T1And T2And T is1≠T2(ii) a Meanwhile, the two ends of the sample to be detected generate a potential difference delta V due to the temperature difference delta T, and the Seebeck coefficient of the material is calculated through a formula S which is delta V/delta T;
the potential difference delta V is obtained by testing the first voltage test probe and the second voltage test probe.
Preferably, the method further comprises the steps of: after the test is finished, the temperature of the first heating block and the temperature of the second heating block are rapidly reduced by starting the cooling system, then the temperatures of the two heating blocks are reset, and the Seebeck coefficient at the next temperature is tested; or replacing the sample to be tested and testing the Seebeck coefficient of the next sample to be tested.
7. The method of testing seebeck coefficients according to claim 6, characterized in that it comprises the following steps:
A1) placing a sample to be detected on a first heating block and a second heating block; preferably, when the sample to be detected is a film sample, the film sample is directly placed on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adjusting the distance between a first heating block and a second heating block according to the size adaptability of the block sample to ensure that the block sample is completely placed in the groove;
A2) contacting a first temperature measurement probe and a first voltage test probe with one end of a sample; the second temperature measuring probe and the second voltage testing probe are contacted with the other end of the sample;
A3) setting the temperature (T) of the first heating blocks before the start of the test1') and the temperature of the second heating block (T)2') and T)1’≠T2’；
A4)T1' and T2' to generate a temperature difference on the surface of the sample; the temperature of the cold end and the hot end of the sample to be measured is measured by temperature measuring probes positioned at the corresponding positions, and the detected temperature is recorded as T1And T2And T is1≠T2；T1And T1' not necessarily identical, T2And T2' are not necessarily the same;
A5) meanwhile, a potential difference delta V is generated between the cold end and the hot end of the sample, and the potential difference delta V is obtained through the test of the first voltage test probe and the second voltage test probe;
A6) temperature T1，T2The data passes through a temperature data acquisition module, potential difference delta V data passes through a voltage data acquisition unit and is respectively transmitted to a computer, and the temperature T of a sample to be measured is obtained through calculation according to a formula S, namely delta V/delta T1The seebeck coefficient under';
preferably, the method for testing the seebeck coefficient further comprises the following steps:
A7) after the test is finished, respectively adding T1' and T2' set to another temperature so that the sample can be tested for seebeck coefficient at different temperatures;
preferably, the method for testing the seebeck coefficient further comprises the following steps:
A8) linear fitting can be performed according to Δ V and Δ T within a certain temperature range, and the obtained slope is the average value of seebeck coefficients.
8. The method for testing electrical conductivity with a test device according to any one of claims 1-4, wherein the method comprises the steps of: and testing the voltage of the sample to be tested by using a voltage testing probe, testing the current of the sample to be tested by using a current testing probe, and testing the conductivity of the sample to be tested according to a linear four-probe method or a Van der Ware method.
9. The method for testing the conductivity of a sample to be tested according to the linear four-probe method of claim 8, wherein the method comprises the following steps:
B1) placing a sample to be detected on a first heating block and a second heating block; preferably, when the sample to be detected is a film sample, the film sample is directly placed on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adjusting the distance between a first heating block and a second heating block according to the size adaptability of the block sample to ensure that the block sample is completely placed in the groove;
B2) respectively contacting a first temperature measuring probe and a second temperature measuring probe with two ends of a sample to be tested, and respectively contacting two voltage testing probes and two current testing probes with the sample to be tested; the first current test probe, the first voltage test probe, the second voltage test probe and the second current test probe are arranged in a linear mode on a straight line penetrating through the geometric center of a sample to be tested, and the temperature measurement probe is located on the end side of the sample to be tested;
B3) the temperatures of the first heating block and the second heating block are both set to be T.
B4) The first voltage test probe and the second voltage test probe are used for testing the voltage (V) at two ends of the sample to be tested1) The conductive pin body of the first current test probe and the conductive pin body of the second current test probe are used for testing the current (I) at two ends of the sample to be tested1)；
Preferably, when the sample to be tested is a filmWhen the sample is taken, and the thickness of the film (e.g., about 10 μm) is ignored with respect to the distance between the probing tips (e.g., about 1mm), V can be obtained from the test1And I1Calculating by combining a formula (1) to obtain the conductivity of the sample to be measured at the temperature T;
wherein σsRepresents the conductivity of the material of the film sample, and δ represents the thickness of the film sample;
preferably, when the sample to be tested is a bulk sample, V is obtained according to the test1And I1Calculating by combining the formula (2) to obtain the conductivity of the sample to be measured at the temperature T;
where σ represents the conductivity of the bulk sample material, A represents the cross-sectional area of the bulk sample, and l represents the length of the bulk sample.
10. A method for testing the conductivity of a sample to be tested by the van der pol method of claim 8, wherein the method comprises the steps of:
C1) placing a sample to be detected on a first heating block and a second heating block; preferably, when the sample to be detected is a film sample, the film sample is directly placed on the two heating blocks; when the sample to be detected is a block sample, placing the block sample in a groove of a heating block, and adjusting the distance between a first heating block and a second heating block according to the size adaptability of the block sample to ensure that the block sample is completely placed in the groove;
C2) respectively contacting a first temperature measuring probe and a second temperature measuring probe with one end of a sample to be measured, wherein the first voltage measuring probe, the first current measuring probe, the second voltage measuring probe and the second current measuring probe are respectively arranged above four corners of the sample to be measured, the four corners are represented by a, b, c and d, the first voltage measuring probe is positioned at the corner a, the second voltage measuring probe is positioned at the corner b, the second current measuring probe is positioned at the corner c, the first current measuring probe is positioned at the corner d, and the voltage measuring probe and the current measuring probe are respectively contacted with the sample to be measured;
C3) setting the temperatures of the first heating block and the second heating block to be T;
C4) r by test Probeba,cd,Rab,dc,Rdc,ab,Rcd,baAnd Rcb,da,Rbc,ad,Rad,bc,Rda,cb；Rba,cdIndicates that a voltage V is applied across babaAnd the current I at the two ends of cd is obtained by testing under the condition that the end b is a positive electrodecdBy the formula Vba/IcdTo obtain a resistance Rba,cd(ii) a Similarly, calculating to obtain Rab,dc,Rdc,ab,Rcd,b，Rcb,da,Rbc,ad,Rad,bc,Rda,cb；
Calculating the conductivity of the sample to be measured according to the formulas (3) to (6);
calculating to obtain RAAnd RB(ii) a Then obtaining R through calculation according to the formula (5)S：
Calculating the conductivity of the sample material to be detected by the formula (6);
wherein, sigma represents the conductivity of the sample material to be measured, and delta represents the thickness of the sample to be measured.
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