CN105628732B - A kind of devices and methods therefor of measurement Seebeck coefficients - Google Patents

Abstract

The invention discloses a device and method for measuring the Seebeck coefficient, wherein the device includes a main/subsidiary heater, a first insulated heat conductor, a second insulated heat conductor, a first main/subsidiary probe, a second main/subsidiary probe, the first main/auxiliary thermocouple, and the second main/auxiliary thermocouple, wherein, the first insulated heat conductor and the second insulated heat conductor are used to place the sample to be measured; the first main/auxiliary probe and the second The main/auxiliary probes are used to measure the potential of the sample to be measured; the first main/auxiliary thermocouple and the second main/auxiliary thermocouple are used to measure the temperature of the sample to be measured. The shape of the sample to be measured in the present invention can be flexible and diverse, and the device can test the Seebeck coefficient of materials under different temperature conditions. With the average test method, the measured Seebeck coefficient has high measurement accuracy.

Description

A device and method for measuring Seebeck coefficient

technical field

The invention belongs to the technical field of test devices, and more particularly relates to a device and method for measuring Seebeck coefficients.

Background technique

Recently, thermoelectric materials, an emerging energy conversion material, have attracted more and more attention. It is a functional material that realizes mutual conversion of thermal energy and electrical energy through carrier transport in semiconductor materials. Thermoelectric materials have a series of advantages such as no noise during operation, no need for transmission parts, cleanliness, environmental protection, and long service life, making this material have a wide and bright application prospect. This makes it particularly important to test the performance of thermoelectric materials, and the Seebeck coefficient is one of the important performance parameters of thermoelectric materials. The Seebeck coefficient, also known as the Seebeck coefficient, is an inherent performance parameter of a material. According to the definition, the Seebeck coefficient of a material can be expressed as:

Among them: S is the Seebeck coefficient of the material, ΔT is the standard temperature difference between the two ends of the material test, V _sr represents the Seebeck voltage generated under the temperature difference ΔT.

The size of the Seebeck coefficient is directly related to the coefficient of thermoelectric performance of the thermoelectric material, that is, the thermoelectric figure of merit. Accurate measurement of the Seebeck coefficient of the material has important practical significance for the evaluation and research of the performance of the thermoelectric material. However, there are currently no relevant international and domestic standards for testing the Seebeck coefficient of semiconductor materials. Although the definition of Seebeck coefficient is relatively simple from a physical concept, in the actual measurement process, how to establish the temperature difference between the two ends of the sample, measure the temperature and voltage at the same position of the sample at the same time, the interference voltage attached to various factors in the measurement process, and data processing There are various practical problems [L.Adnane, N.Williams, H.Silva, and A.Gokirmak.Rev.Sci.Instrum.86, 105119(2015).]. Among the detection equipment that has been developed, most of them are for the measurement of semiconductor bulk samples, and many of them use the two-probe method (for example, for the integration of Seebeck coefficient and resistivity of bulk samples Integrated testing), these devices cannot complete the measurement well for semiconductor materials that are not easy to process into bulk shapes, or semiconductors that require sample placement. There are not many devices for testing sheet samples and testing Seebeck coefficients using similar four-probe resistance testing techniques, and there are gaps in the corresponding Seebeck coefficient testing process standards and data processing methods.

Contents of the invention

For the above defects or improvement needs of the prior art, the object of the present invention is to provide a device and method for measuring the Seebeck coefficient, wherein by improving the key measurement principle of the device, the structure of each component and its setting method, etc., Compared with the existing technology, it can effectively solve the problem of high requirements for measuring the shape of the sample. The shape of the sample to be measured can be flexible and diverse, and the device can test the Seebeck coefficient of the material under different temperature conditions. The structure of the device is simple. Based on the test method of obtaining multiple sets of Seebeck coefficients by four probes and then averaging, the measurement accuracy of the measured Seebeck coefficients is high.

In order to achieve the above object, according to one aspect of the present invention, a kind of device of measuring Seebeck coefficient is provided, it is characterized in that, comprise main heater (1), secondary heater (5), the first insulating heat conductor (3), The second insulating heat conductor (4), the first main probe (11), the first sub-probe (12), the second main probe (13), the second sub-probe (14), the first main thermocouple (7), the first auxiliary thermocouple (8), the second main thermocouple (9) and the second auxiliary thermocouple (10); wherein,

Both the first insulating heat conductor (3) and the second insulating heat conductor (4) are located on the main heater (1), placed in a front-to-back positional relationship, and the first insulating heat conductor (3) No direct contact with the second heat insulating conductor (4); both the first heat insulating conductor (3) and the second heat insulating conductor (4) are used to place the sample to be measured; the sample to be measured One end of which is in contact with the first insulating heat conductor (3), and the other end is in contact with the second insulating heat conductor (4);

The auxiliary heater (5) is located on one side of the first insulating heat conductor (3), and is used to heat the first insulating heat conductor (3); the main heater (1) is used to simultaneously heat the The first heat insulating conductor (3) and the second heat insulating conductor (4) are heated;

The first main probe (11) and the first sub-probe (12) are respectively used to measure the potential at the left and right ends of the contact part of the sample to be measured and the first insulating heat conductor (3), so The second main probe (13) and the second sub-probe (14) are respectively used to measure the potential at the left and right ends of the part where the sample to be measured is in contact with the second insulating heat conductor (4);

The first main thermocouple (7) and the first auxiliary thermocouple (8) are respectively located at the left and right parts below the first insulating heat conductor (3), and are respectively used to measure the sample to be measured The temperature at the left and right ends of the part in contact with the first insulating heat conductor (3); the second main thermocouple (9) and the second secondary thermocouple (10) are located at the second insulating heat conductor ( 4) The lower left and right parts are respectively used to measure the temperature of the left and right ends of the part where the sample to be measured is in contact with the second insulating heat conductor (4).

As a further preference of the present invention, the sample to be measured is a block sample or a sheet sample.

As a further preference of the present invention, the first main probe (11), the first sub-probe (12), the second main probe (13), the second sub-probe (14) Both the sample to be measured and the sample to be measured are located in a vacuum environment or a protective gas environment.

As a further preference of the present invention, the first main thermocouple (7), the first auxiliary thermocouple (8), the second main thermocouple (9) and the second auxiliary thermocouple (10) The position can be adjusted left and right.

According to another aspect of the present invention, the method for measuring the Seebeck coefficient utilizing the above-mentioned device for measuring Seebeck coefficient is provided, it is characterized in that, comprising the following steps:

(1) Installation of the sample to be measured:

The sample to be measured is placed on the first insulating heat conductor and the second insulating heat conductor, so that one end of the sample to be measured is in contact with the first insulating heat conductor, and the other end is in contact with the second insulating heat conductor; The heater and the sub-heater heat the sample to be measured;

(2) Measuring temperature and potential: using the first main probe, the first sub-probe, the second main probe, the second sub-probe, the first main thermocouple, the first sub-thermocouple, and the second main thermocouple and the second secondary thermocouple respectively measure the temperature and potential of the sample to be measured, wherein,

The first main probe and the first sub-probe are respectively used to measure the potential at the left and right ends of the part where the sample to be measured is in contact with the first insulating heat conductor;

The second main probe and the second sub-probe are respectively used to measure the potential at the left and right ends of the part where the sample to be measured is in contact with the second insulating heat conductor;

The first main thermocouple and the first auxiliary thermocouple are respectively located at the left and right parts below the first insulating heat conductor, and are respectively used to measure the relative temperature between the sample to be measured and the first insulating heat conductor. The temperature at the left and right ends of the contact part;

The second main thermocouple and the second auxiliary thermocouple are respectively located at the left and right parts below the second insulating heat conductor, and are respectively used to measure the relative temperature between the sample to be measured and the second insulating heat conductor. The temperature at the left and right ends of the contact part;

(3) Calculate the Seebeck coefficient:

Note that the difference between the temperature measured by the first main thermocouple and the temperature measured by the second auxiliary thermocouple is ΔT ₁ , and the temperature measured by the first auxiliary thermocouple is different from the temperature obtained by the second main thermocouple. The difference between the temperatures measured by the thermocouple is ΔT ₂ , the difference between the temperature measured by the first secondary thermocouple and the temperature measured by the second secondary thermocouple is ΔT ₃ , and the temperature measured by the second secondary thermocouple is ΔT 3 . The difference between the temperature measured by a main thermocouple and the temperature measured by the second main thermocouple is ΔT ₄ ;

The difference between the potential measured by the first main probe and the potential measured by the second sub-probe is V ₁ , and the potential measured by the first sub-probe is the same as the potential obtained by the second main probe. The difference between the potentials measured by the needle is V ₂ , the difference between the potentials measured by the first sub-probe and the potential measured by the second sub-probe is V ₃ , and the first The difference between the potential measured by the main probe and the potential measured by the second main probe is V ₄ ;

Calculate the Seebeck coefficient of the sample to be measured according to ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ , V ₁ , V ₂ , V ₃ and V ₄ .

As a further preference of the present invention, the ΔT ₁ , ΔT ₂ , ΔT ₃ , ΔT ₄ , V ₁ , V ₂ , V ₃ and V ₄ are multiple groups, and the multiple groups of ΔT ₁ and the multiple groups of V ₁ One-to-one correspondence, the multiple sets of ΔT ₂ are in one-to-one correspondence with the multiple sets of V ₂ , the multiple sets of ΔT ₃ are in one-to-one correspondence with the multiple sets of V ₃ , the multiple sets of ΔT ₄ are in one-to-one correspondence with the multiple sets of V ₄ one-to-one correspondence;

The Seebeck coefficient S of described sample satisfies:

Wherein, S ₁ is the slope after the linear fitting of the multiple groups of ΔT ₁ and the multiple groups of V ₁ ; S ₂ is the slope of the linear fitting of the multiple groups of ΔT ₂ and the multiple groups of V ₂ ; S ₃ is the slope after the linear fitting of the multiple groups of ΔT ₃ and the multiple groups of V ₃ ; S ₄ is the slope of the linear fitting of the multiple groups of ΔT ₄ and the multiple groups of V ₄ .

Through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:

1. By improving the structure of the test device, the Seebeck coefficient of the sheet sample can be tested. The present invention places the sample to be measured (such as a semiconductor material sample) on the first insulating heat conductor and the second insulating heat conductor by setting the first main/auxiliary probe and the second main/auxiliary probe, and then uses the first The main/auxiliary probe and the second main/auxiliary probe measure the potential of different positions of the sample to be measured, which can be applied to bulk test sample materials whose shape is not convenient to be made into a slender shape, or which need to be made into a sheet to The material for testing thermoelectric properties, and the slender block sample is easy to install during the test, overcoming the shape limitation of the existing test device on the test sample (for example, only for bulk materials). By fixing the main part of the thermocouple on the part of the heating device, the temperature measurement accuracy is improved, and the interference of the thermoelectric force of the thermocouple itself on the test is also eliminated.

2. The method of measuring the Seebeck coefficient with four probes is used, which improves the measurement accuracy and can be better combined with the measurement of resistivity with four probes, which is convenient for integrated design. In the prior art, because the measurement of the Seebeck coefficient cannot be matched with a four-probe test resistivity platform, often many integrated test equipment for the Seebeck coefficient and resistivity that have been built can only use the two-probe test method, and the more advanced four-probe test The method of measuring the resistivity of the probe (such as the van der Pauw method) cannot be applied. The present invention applies a platform similar to the four-probe test resistivity to the measurement of the Seebeck coefficient of the material. According to the supporting measurement process and data processing method, the measurement accuracy of the sample can be effectively improved, and it is also convenient to use the same platform. Perform a four-probe resistivity test.

3. The structure of the device in the present invention cleverly separates the temperature-measuring thermocouple from the voltage-measuring probe, and fixes the thermocouple body on the heat-conducting block on the heating device, effectively reducing the cold- The finger effect improves the temperature measurement accuracy and eliminates the interference of the thermocouple's own thermoelectric effect on the Seebeck electromotive force. Simple thermocouple point contact temperature measurement has the so-called cold-finger effect, which makes the measured temperature value lower than the actual temperature. The higher the temperature to be measured, the more obvious the cold-finger effect. By separating the device for measuring temperature and voltage during sample testing, the main body of the thermocouple is fixed on the heat conduction block on the heating device, which can significantly reduce the cold-finger effect. At the same time, the Seebeck electromotive force interference caused by the thermoelectric effect of the thermocouple itself is eliminated.

4. The test method in the present invention is to apply the non-existing origin fitting method to the flake dynamic method measurement, which can improve the accuracy of drawing conclusions. The existing methods of measuring Seebeck coefficient are mainly divided into static method and dynamic method. The static method test is usually long because the temperature at both ends of the sample is difficult to keep stable, it is difficult to establish a constant temperature difference, and there is error voltage interference, so the test time is usually relatively long. It is not easy to realize and the error is large; the dynamic method test, the existing test method is commonly used to assume that the temperature at both ends of the sample and the voltage between the two ends of the sample are proportional to time, then the Seebeck coefficient is equivalent to the voltage and temperature difference The ratio of the proportional coefficients of the two over time. This method has achieved relatively good test results, but in fact, the temperature difference between the two ends of the sample and the voltage between the two ends are not strictly proportional to time, so this processing method still has certain sources of error. Another method used is to set multiple sets of stable temperature combinations at both ends on the basis of keeping the average temperature at both ends of the sample constant, so as to obtain multiple sets of constant temperature difference combinations, and then measure the temperature differences generated by these combinations Seebeck Voltage, the data are fitted to the curve through the origin to obtain the Seebeck coefficient. Although according to the definition of Seebeck coefficient, the voltage and temperature difference between both ends should be strictly proportional, but due to some interference factors, the actual fitted curve does not necessarily pass through the origin. The present invention combines the above-mentioned device structure, cooperates with the provided dynamic method test process for sheet materials, uses multiple sets of data measured by the dynamic method, only considers the slope after linear fitting, and uses the non-origin fitting method for data calculation , the Seebeck coefficient is obtained, the test time is short, and the conclusions drawn are more accurate.

5. The present invention forms four temperature-voltage combinations based on the four points tested, and then obtains four sets of Seebeck coefficients and calculates the average result. The existing similar test structures or devices are basically the Seebeck coefficients obtained by using the combination of temperature and voltage at two points (dynamic method or static method) on the same sample. When the sample structure is uniform and non-oriented, this method can also obtain relatively accurate test results, but if the measured sample has a slight compositional inhomogeneity, the data measured by the method of the same device may be different from the true value of the whole material. If there is a deviation in the Seebeck coefficient, there is a large error in the test. However, the present invention forms four temperature-voltage combinations based on the four points tested, then obtains four sets of Seebeck coefficients, and obtains the averaged results. This method can not only obtain relatively accurate results when the sample composition is uniform, but also has a unique advantage when the composition is slightly uneven: the final data obtained can better represent the entire material. Integrating the Seebeck coefficient, by analyzing the difference of the Seebeck coefficient value of each group of tests, the degree of compositional inhomogeneity of the entire material can also be analyzed.

To sum up, compared with the previous patents, the present invention has the following improvements and corresponding benefits in the structure of the device:

(1) Through the above-mentioned structural design, the present invention can directly place samples of blocks and sheets on two insulating heat conductors. Compared with other inventions, the shape and size of samples that can be tested are significantly larger.

(2) the present invention is by four probes to the Seebeck coefficient test of sample, and existing test device and method have only used two probes, for example the situation that sample material is inhomogeneous, precision is not high; The present invention passes four A probe device and a corresponding test method can obtain significantly more accurate and comprehensive test results.

(3) The position of the thermocouple in the present invention can be adjusted flexibly with the positions of the four probes (comprising the first main/sub-probe and the second main/sub-probe). Most of the thermocouples in the existing invention are basically They are all exposed outside as temperature-measuring thermocouples, and measure the temperature by single-point contact with the sample; the device of the present invention embeds the thermocouple body under the insulating heat conductor, especially through position adjustment so that the position of each thermocouple is consistent with the probe. Corresponding to the position of the needle, in the actual test process, especially for the test under high temperature conditions, more accurate measurement results can be obtained.

Correspondingly, compared with the existing invention, the testing method of the present invention also has its unique characteristics. Many existing inventions and related equipment that have been developed, when measuring the Seebeck coefficient, they all assume that the measured material composition is uniform by default, and the Seebeck coefficient of each area on the test sample is also roughly the same, so many inventions are Only two points are taken to test the entire sample, which is equivalent to the test that the Seebeck coefficient of the entire sample is between certain two points. In fact, in addition to the possible deviation of material composition, some slight differences in processing and treatment in different regions of the material will have a great impact on the thermoelectric properties (including Seebeck coefficient) of the entire sample, so only the difference between two points The Seebeck coefficient values obtained from temperature difference and voltage measurements often vary greatly. Aiming at this characteristic, the present invention proposes a method of measuring four groups of different temperature and voltage combinations at four points to obtain four groups of Seebeck coefficient values, and then calculating an average to obtain the final result. Compared with existing inventions, this method can overcome the measurement when the distribution of Seebeck coefficient values of samples that cannot be overcome by previous inventions is not very uniform, so that the measured values are more comprehensive and accurate. . In addition, the measurement positions of the potential and temperature are selected at the left and right ends of the part where the sample to be measured is in contact with an insulating heat conductor (that is, the area near the edge of the sample to be measured), and the test has good stability and accuracy.

In summary, the device and method provided by the present invention can improve the test accuracy of Seebeck coefficient well, and can be used to develop a new generation of test instruments, which is beneficial to material performance testing and research and development, and has broad application prospects.

Description of drawings

Fig. 1 is the device structure schematic diagram of measuring Seebeck coefficient among the present invention;

Fig. 2 is a curve diagram of multiple groups of ΔT ₁ and V ₁ raw data fitting S ₁ value;

Fig. ₃ is a curve diagram of multiple groups of ΔT and V raw data fitting _S value _;

Fig. 4 is the graph of multiple groups of ΔT ₃ and V ₃ original data fitting S ₃ value;

Fig. 5 is a curve diagram of fitting S ₄ value of multiple sets of ΔT ₄ and V ₄ raw data.

The meanings of the reference signs in the figure are as follows: 1 is the heating device (i.e. the main heater), 2 is the sealing area, 3 and 4 are insulating heat conductors, 5 is the heater (i.e. the auxiliary heater), 7, 8, 9 and 10 are thermocouples, and 11, 12, 13 and 14 are probes.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

Example 1

As shown in Figure 1, the device for measuring the Seebeck coefficient comprises a main heater 1, a secondary heater 5, a first insulating heat conductor 3, a second insulating heat conductor 4, a first main probe 11, a first auxiliary probe 12, The second main probe 13, the second auxiliary probe 14, the first main thermocouple 7, the first auxiliary thermocouple 8, the second main thermocouple 9 and the second auxiliary thermocouple 10; wherein,

The first insulated heat conductor 3 and the second insulated heat conductor 4 are all located on the main heater 1, and the first insulated heat conductor 3 and the second insulated heat conductor 4 are not in direct contact; the first insulated heat conductor 3 and the second insulated heat conductor The thermal conductors 4 are all used to place the sample to be measured; one end of the sample to be measured is in contact with the first insulating thermal conductor 3, and the other end is in contact with the second insulating thermal conductor 4;

The auxiliary heater 5 is located on the side of the first insulated heat conductor 3 or the second insulated heat conductor 4, and is used to heat the first insulated heat conductor 3 or the second insulated heat conductor 4; the main heater 1 is used to heat the first insulated heat conductor The thermal conductor 3 and the second insulating thermal conductor 4 are heated;

The first main probe 11 and the first sub-probe 12 are used to measure the potential at both ends of the part in contact with the first insulating heat conductor 3 in the sample to be measured;

The second main probe 13 and the second sub-probe 14 are used to measure the potential at both ends of the part in contact with the second insulating heat conductor 4 in the sample to be measured;

The first main thermocouple 7 and the first auxiliary thermocouple 8 are all located below the first insulating heat conductor 3, and are used to measure the first main probe 11 and the first heat insulating conductor 3 in the sample to be measured. The temperature of the part below the corresponding point in the sub-probe 12 placement area;

The second main thermocouple 9 and the second auxiliary thermocouple 10 are all located under the second insulating heat conductor 4, and are used to measure the contact with the second insulating heat conductor 4, the second main probe 13 and the second heat conductor 4 in the sample to be measured. The sub-probe 14 placement area corresponds to the temperature of the part below the point.

In the present invention, the heating device 1 can provide ambient temperature when heating; the device also has a sealed area 2 (which can be vacuumed or fed with protective gas), which can prevent the sample to be tested from being oxidized when testing the Seebeck coefficient. Two insulated heat conductors 3 and 4 are fixed on the heating device for placing samples, and the two are separated by a certain distance to facilitate the establishment of the temperature difference between the two ends of the sample. A small heater 5 is fixed inside the area where the heat conductor 3 is close to the sample, and is used to heat one end of the sample. Four thermocouples 7, 8, 9, 10 are respectively fixed on the same horizontal line of the lower part where the two heat conductors 3, 4 are facing the sample. Around the heating device 1, four probes 11, 12, 13, 14 are also fixed with springs, the protruding length and the tightness of pressing can be adjusted according to the size and thickness of the sample, so that the probes are in good contact with the sample.

In this embodiment, four probes are fixed on the periphery of the heating device. After one end of the probe is fixed, the other end is placed on the area where the sample is placed on the heating device, and the sample is pressed against the sample during measurement. The protruding length of the probe and the tightness of pressing can be adjusted to facilitate the installation of the sample and make the probe in good contact with the sample. Four probes are used to measure the Seebeck electromotive force generated by the Seebeck effect.

The device can be connected with a computer through a data acquisition card to realize automatic data collection and processing. For example, the voltage values output by the four probes are connected to the data acquisition card 15, and an 8-channel 16-bit acquisition card is selected, and each channel can change the range independently, which can satisfy the acquisition of voltage signals and temperature signals at the same time. Through the combination of lines, the data acquisition card can measure the voltage between multiple groups of probe pairs, among which 4 channels are allocated for pairs between probes 11 and 14, 12 and 13, 11 and 13, 12 and 14 voltage collection. Allocate 4 channels of data acquisition card for signal input and acquisition of four thermocouples 7, 8, 9, 10. The data acquisition card communicates with the computer through the RS485-RS232 converter 17, and controls the acquisition of the acquisition card through a computer program. The large heating device 1 needs to be heated to provide ambient temperature, so a classic PID temperature controller 16 is set to control its heating rate and heating temperature. The PID also communicates with the computer through the RS485 serial port. Since the small heater 4 only needs to be energized and heated after the large heating device is heated to the required temperature, and the power can be turned off after the temperature difference between the two ends of the sample is established, it does not need to be controlled by PID, but only needs to be controlled by a computer that can communicate with the computer. Program the relay to turn the small heater on and off.

The whole process of obtaining the Seebeck coefficient result of the material by using the above-mentioned device can be divided into the testing stage and the calculation stage; where:

In the testing phase, the sample should be made and installed first, so that the sample meets the sample requirements and installation requirements, and then the measurement is carried out.

The sample requirements are: the sample is in the shape of a regular rectangular sheet, and the length of the sample has a fixed requirement (generally 10-15mm) according to the size of the sample placement area. The sample is required to be regular and flat, with uniform thickness and no large holes. If the four-probe van der Pauw resistivity test is to be performed simultaneously on this platform, in addition to meeting the above requirements, the sample standard corresponding to the four-probe resistivity test should also be met (for example, see ASTM: F76-08) .

The sample installation requirements are: install the prepared sample on the sample stage, and pay attention to that the two ends of the sample should be aligned with the positions where the thermocouples are installed on the heat conduction blocks 3 and 4. Adjust the protruding length of the four probes, place the four probes on the four corners of the upper and lower edges of the sample, and require the upper and lower probes 11, 12, 13, 14 to be connected with the thermocouples 7, 8, 9, 10 Corresponding to the position, so that when the temperature difference between the two ends of the sample is established, the detected voltage and temperature are basically at the same position. After adjusting the position of the probe, put down the probe, and apply proper pressing force from the fixed spring to keep the probe in good contact with the sample.

The contact detection and testing process is as follows:

Contact detection: After the above-mentioned platform is built and the samples are initially installed, power on and run. First of all, it is necessary to check whether the contacts of the four probes are in good contact with the sample. You can know that the contact between the probes and the sample is good by passing a current between each two probes and then detecting the voltage to judge whether the corresponding current and voltage are in a linear relationship. degree.

Test process: After the sample is placed and installed, the test process begins. First, the PID is controlled by the computer to heat the heating device to the required ambient temperature. When it is determined to be heated to the required temperature and the temperature is stable, turn on the small heater 4, and then turn off the small heater 5 immediately after establishing a temperature difference between the two ends of the sample on the basis of keeping the ambient temperature not changing much at this time. Detect the average temperature of the hot and cold ends at this time, and it should be kept around the ambient temperature. Start to collect 14 sets of data simultaneously and continuously through the data acquisition card, each set of data includes: the voltage between probes 11 and 14, denoted as V ₁ , the voltage between probes 12 and 13, denoted as V ₂ , the probe The voltage between 11 and 13 is recorded as V ₃ , the voltage between probes 12 and 14 is recorded as V ₄ , and the temperature values of the four thermocouples are recorded as T ₁ , T ₂ , T ₃ , and T ₄ .

The calculation phase includes the following steps:

First, according to the temperature of thermocouple 7 (denoted as T _A ) and the temperature of thermocouple 10 (denoted as T _B ) in each set of data, the temperature difference between the two is obtained, denoted as ΔT ₁

ΔT ₁ =T _A -T _B

According to the voltage between the probes 11 and 14 measured in each set of data, record it as V ₁ ,

According to the calculated sets of ΔT ₁ and V ₁ , by the following formula

V ₁ =S ₁ ΔT ₁ +B ₁

The fitted slope S ₁ is the obtained Seebeck coefficient value

Theoretically, the Seebeck voltage is strictly proportional to the temperature difference, that is, the fitting curve should pass through the origin, but in the actual process, the existence of various system errors will make the fitting curve not pass the origin. This dynamic method also uses However, the origin fitting can get more accurate values.

Similarly, according to the temperature of thermocouple 8 (denoted as T _C ) and the temperature of thermocouple 9 (denoted as T _D ) in each set of data, the temperature difference between the two is obtained, denoted as ΔT ₂

ΔT ₂ =T _C -T _D

According to the voltage between the probes 12 and 13 measured in each set of data, record it as V ₂ ,

According to the calculated multiple sets of ΔT ₂ and V ₂ , by the same fitting formula

V ₂ =S ₂ ΔT ₂ +B ₂

The fitted slope S ₂ is another Seebeck coefficient value obtained

Then, according to the temperature of thermocouple 8 (denoted as T _C ) and the temperature of thermocouple 10 (denoted as T _B ) in each set of data, the temperature difference between the two is obtained, denoted as ΔT ₃

ΔT ₃ =T _C -T _B

According to the voltage between the probes 12 and 14 measured in each set of data, record it as V ₃ ,

According to the calculated multiple sets of ΔT ₃ and V ₃ , by the same fitting formula

V ₃ =S ₃ ΔT ₃ +B ₃

The fitted slope S ₃ is the obtained third Seebeck coefficient value.

Finally, according to the temperature of thermocouple 7 (denoted as T _C ) and the temperature of thermocouple 9 (denoted as T _D ) in each set of data, the temperature difference between the two is obtained, denoted as ΔT ₄

ΔT ₄ =T _A -T _D

According to the voltage between the probes 11 and 13 measured in each set of data, record it as V ₄ ,

According to the calculated multiple sets of ΔT ₄ and V ₄ , by the same fitting formula

V ₄ =S ₄ ΔT ₄ +B ₄

The fitted slope S ₄ is the obtained fourth Seebeck coefficient value.

Then obtain the average value of S ₁ , S ₂ , S ₃ , and S ₄ and record it as S,

The obtained coefficient S is the final Seebeck coefficient.

Error Analysis:

According to the definition of Seebeck coefficient, its relative error can be expressed as:

In the formula, U is the Seebeck potential, and ΔT is the temperature difference between the hot and cold ends of the sample. For the first item, when the range of the selected data acquisition card is 15mv, its resolution is less than 0.5μv, and its own conversion error is only 0.5%. The error is estimated by △T=10K, α=50μv/K, It is about 0.6%; for the second item, there are mainly thermocouple errors, A/D conversion errors and errors due to contact thermal resistance. We use Pt-Pt-10%Rh thermocouples to measure temperature, because this kind of thermocouples It has a random error, for example, the error is ±0.25% at 0-1300°C. According to the error handling method, this error can be reduced by multiple measurements, such as using the arithmetic mean of the temperature measured n times to replace the real temperature ( The standard deviation at T ₀ ) is:

Since the microcomputer collects data readings very quickly (collecting 10 points per second), we use 200 readings for each temperature point, and then take the average value. For example, when the temperature measurement point is 500°C, the random error of 100 readings can be reduced to Then the resulting temperature difference |η _ΔT | error is 0.18K. In the process of the data acquisition card collecting the potential signal of the thermocouple and converting it into a temperature value, combined with the characteristics of the Pt-Pt-10%Rh thermocouple, the readings T _h and T at both ends of the sample are obtained when the temperature is ≥0°C _c errors are <0.15K, then |η _ΔT |<0.3K. For the error caused by contact thermal resistance, if the contact material is selected properly, and the processing accuracy is relatively high to ensure that the sample is in good contact, this error can basically be ignored. From this point of view, the total error is about |η _ΔT |<0.48K, if the error is estimated by ΔT=10K, then |η _ΔT |/η<4.8%, then according to the principle of error summation, each set of data The resulting errors should be basically the same, so the total error of the Seebeck coefficient is about 5%.

Use this test system to measure the Seebeck coefficient of the P-type Bi _0.5 Sb _1.5 Te ₃ material at room temperature. The four sets of original data tested are shown in Figures 2, 3, 4, and 5. The Seebeck coefficient fitted for each set of data The average Seebeck coefficient was obtained by averaging, and compared with the test value of the HGTE-II thermoelectric parameter test system using the same standard test instrument, the deviation and error were obtained, as shown in Table 1.

Table 1

In combination with the structure of the testing device, this embodiment implements the dynamic method measurement for the flake sample for the first time, provides supporting testing standards, and puts forward requirements for various aspects of the testing process (such as the production and installation of the sample, the connection between the sample and the probe). Whether the contact is good, etc.), improving the quality of the test.

The present invention can also design special software, for example, selects the c# of Microsoft as the development language of test software, obtains the computer software that is matched with measuring device and method in the present invention, realizes that test is computer integrated control, collection, calculation, display output the process of.

The protective gas in the present invention can be a commonly used protective gas, such as nitrogen, rare gas or a mixture thereof. The present invention also proposes supporting test standards, which mainly provide detailed standard requirements for sample requirements before testing, sample installation, contact detection, probe position detection, and test procedures, and also provide detailed standard requirements for data processing after testing. The method (for example, the use of dynamic method but the origin for curve fitting, and the method of using multiple sets of temperature-voltage combinations to fit multiple sets of Seebeck coefficients to calculate the average value has unique advantages when testing the Seebeck coefficient of inhomogeneous samples ), improving the test accuracy. Through the adjustment of the main/sub-heater, the Seebeck coefficient of semiconductor materials can be measured at any temperature, which improves the measurement accuracy.

It is easy for those skilled in the art to understand that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, All should be included within the protection scope of the present invention.

Claims (6)

1. A device for measuring Seebeck coefficients is characterized by comprising a main heater (1), an auxiliary heater (5), a first insulating heat conductor (3), a second insulating heat conductor (4), a first main probe (11), a first auxiliary probe (12), a second main probe (13), a second auxiliary probe (14), a first main thermocouple (7), a first auxiliary thermocouple (8), a second main thermocouple (9) and a second auxiliary thermocouple (10); wherein,

the first insulating heat conductor (3) and the second insulating heat conductor (4) are both positioned on the main heater (1) in a front-rear position relation, and the first insulating heat conductor (3) and the second insulating heat conductor (4) are not in direct contact with each other; the first insulating heat conductor (3) and the second insulating heat conductor (4) are used for placing a sample to be measured; one end of the sample to be measured is contacted with the first insulating heat conductor (3), and the other end is contacted with the second insulating heat conductor (4);

the auxiliary heater (5) is positioned on one side of the first insulating heat conductor (3) and is used for heating the first insulating heat conductor (3); the main heater (1) is used for heating the first insulating heat conductor (3) and the second insulating heat conductor (4) simultaneously;

the first main probe (11) and the first auxiliary probe (12) are respectively used for measuring the electric potentials at the left end and the right end of the contact part of the sample to be measured and the first insulating heat conductor (3), and the second main probe (13) and the second auxiliary probe (14) are respectively used for measuring the electric potentials at the left end and the right end of the contact part of the sample to be measured and the second insulating heat conductor (4);

the first main thermocouple (7) and the first auxiliary thermocouple (8) are respectively positioned at the left part and the right part below the first insulating heat conductor (3) and are respectively used for measuring the temperature of the left end and the right end of the contact part of the sample to be measured and the first insulating heat conductor (3); the second main thermocouple (9) and the second auxiliary thermocouple (10) are respectively positioned at the left part and the right part below the second insulating heat conductor (4) and are respectively used for measuring the temperature of the left end and the right end of the contact part of the sample to be measured and the second insulating heat conductor (4);

the apparatus also includes a component to calculate a Seebeck coefficient based on the Δ T ₁ 、ΔT ₂ 、ΔT ₃ 、ΔT ₄ 、V ₁ 、V ₂ 、V ₃ And V ₄ Calculating the Seebeck coefficient of the sample to be measured; wherein the difference between the temperature measured by the first main thermocouple and the temperature measured by the second auxiliary thermocouple is Delta T ₁ The difference value between the temperature measured by the first secondary thermocouple and the temperature measured by the second main thermocouple is delta T ₂ The difference value between the temperature measured by the first secondary thermocouple and the temperature measured by the second secondary thermocouple is delta T ₃ The difference between the temperature measured by the first main thermocouple and the temperature measured by the second main thermocouple is delta T ₄ (ii) a The difference value of the electric potential measured by the first main probe and the electric potential measured by the second auxiliary probe is V ₁ The difference value between the electric potential measured by the first auxiliary probe and the electric potential measured by the second main probe is V ₂ The difference value between the electric potential measured by the first auxiliary probe and the electric potential measured by the second auxiliary probe is V ₃ The difference value between the electric potential measured by the first main probe and the electric potential measured by the second main probe is V ₄ 。

2. The apparatus for measuring a Seebeck coefficient according to claim 1, wherein said sample to be measured is a block sample or a sheet sample.

3. The apparatus for measuring Seebeck coefficient according to claim 1, characterized in that said first main probe (11), said first secondary probe (12), said second main probe (13), said second secondary probe (14) and said sample to be measured are all located in a vacuum environment or in a protective gas environment.

4. Device for measuring the Seebeck coefficient according to claim 1, characterized in that the position of said first main thermocouple (7), said first secondary thermocouple (8), said second main thermocouple (9) and said second secondary thermocouple (10) can be adjusted left or right.

5. A method for measuring a Seebeck coefficient using the apparatus for measuring a Seebeck coefficient according to any one of claims 1 to 4, comprising the steps of:

(1) Installation of the sample to be measured:

placing a sample to be measured on a first insulating heat conductor and a second insulating heat conductor, so that one end of the sample to be measured is in contact with the first insulating heat conductor and the other end of the sample to be measured is in contact with the second insulating heat conductor; heating the sample to be measured by a main heater and a secondary heater;

(2) Measuring temperature and potential: respectively measuring the temperature and the potential of the sample to be measured by using a first main probe, a first auxiliary probe, a second main probe, a second auxiliary probe, a first main thermocouple, a first auxiliary thermocouple, a second main thermocouple and a second auxiliary thermocouple, wherein,

the first main probe and the first auxiliary probe are respectively used for measuring the electric potentials of the left end and the right end of the contact part of the sample to be measured and the first insulating heat conductor;

the second main probe and the second auxiliary probe are respectively used for measuring the electric potentials of the left end and the right end of the contact part of the sample to be measured and the second insulating heat conductor;

the first main thermocouple and the first auxiliary thermocouple are respectively positioned at the left part and the right part below the first insulating heat conductor and are respectively used for measuring the temperature of the left end and the right end of the contact part of the sample to be measured and the first insulating heat conductor;

the second main thermocouple and the second auxiliary thermocouple are respectively positioned at the left part and the right part below the second insulating heat conductor and are respectively used for measuring the temperature of the left end and the right end of the contact part of the sample to be measured and the second insulating heat conductor;

(3) Calculating the Seebeck coefficient:

recording the difference between the temperature measured by the first main thermocouple and the temperature measured by the second auxiliary thermocouple as delta T ₁ The difference value between the temperature measured by the first secondary thermocouple and the temperature measured by the second main thermocouple is delta T ₂ The difference value between the temperature measured by the first secondary thermocouple and the temperature measured by the second secondary thermocouple is delta T ₃ The difference between the temperature measured by the first main thermocouple and the temperature measured by the second main thermocouple is delta T ₄ ；

The difference value between the electric potential measured by the first main probe and the electric potential measured by the second auxiliary probe is V ₁ The difference value between the electric potential measured by the first auxiliary probe and the electric potential measured by the second main probe is V ₂ The difference value between the electric potential measured by the first auxiliary probe and the electric potential measured by the second auxiliary probe is V ₃ The difference value between the electric potential measured by the first main probe and the electric potential measured by the second main probe is V ₄ ；

According to Δ T ₁ 、ΔT ₂ 、ΔT ₃ 、ΔT ₄ 、V ₁ 、V ₂ 、V ₃ And V ₄ Calculating the Seebeck coefficient of the sample to be measured.

6. The method for measuring Seebeck coefficient according to claim 5, wherein the Δ T is ₁ 、ΔT ₂ 、ΔT ₃ 、ΔT ₄ 、V ₁ 、V ₂ 、V ₃ And V ₄ Is a plurality of groups, the plurality of groups are delta T ₁ And the plurality of groups V ₁ One-to-one correspondence, the plurality of sets Δ T ₂ And the plurality of groups V ₂ One to one correspondence, the multiple groups of Δ T ₃ And the plurality of groups V ₃ One-to-one correspondence, the plurality of sets Δ T ₄ And the plurality of groups V ₄ One-to-one correspondence is realized;

the Seebeck coefficient S of the sample satisfies:

wherein S is ₁ Is the multiple groups of delta T ₁ And the plurality of groups V ₁ Slope after linear fitting; s ₂ Is the multiple groups of delta T ₂ And the plurality of groups V ₂ Slope after linear fitting; s ₃ Is the multiple groups of delta T ₃ And the plurality of groups V ₃ Slope after linear fitting; s. the ₄ Is the multiple groups of delta T ₄ And the plurality of groups V ₄ Slope after linear fit.