KR101541390B1 - Performance evaluation device of thin-film thermoelectric material and method thereof - Google Patents

Abstract

The present invention relates to an apparatus for evaluating a performance of a thin film thermoelectric material, which minimizes a deviation of contact condition with the thin film thermoelectric material, and a method thereof. The apparatus provides: a temperature control stage which controls the temperature at both ends of the thin film thermoelectric material; a temperature detection part for measuring the surface temperature emitted from a surface of the thin film thermoelectric material; a measurement part for measuring electrical characteristics generated by contacting the surface of the thin film thermoelectric material; and a main control part which obtains a seebeck coefficient by receiving the electrical characteristics measured by the measurement part according to the temperature information of the thin film thermoelectric material detected by the temperature detection part.

Description

TECHNICAL FIELD [0001] The present invention relates to a device for evaluating the performance of a thin film thermoelectric material and a method for evaluating the performance of the thin film thermoelectric material.

The present invention relates to an apparatus and a method for evaluating the performance of a thin film thermoelectric material, and more particularly, to an apparatus and method for evaluating the performance of a thin thermoelectric material that minimizes a variation in contact conditions with the thin film thermoelectric material.

Research and development are continuing on the possibility of thermoelectric materials as energy harvesting and environmentally friendly alternative energy. Prior to the development of nanotechnology, thermoelectric materials were used in bulk form only in special fields such as defense and space industry due to low efficiency as an energy source. However, when thermoelectric material is controlled in nano size by applying NT technology from 2000's, thermoelectric conversion efficiency Has been proved to be able to improve more than twice as compared with the bulk type, and development of nanotechnology based thermoelectric materials using multi-layered superlattice layers, nanowires, and nano powders has been actively performed.

The development of thermoelectric materials based on nanotechnology can improve the thermoelectric conversion efficiency as well as making it thinner. It can be used for portable power generation and cooling device of smart phone, wireless sensor network power supply device for remote installation such as crude oil transfer pipeline, It is also applicable as a thin, flexible type power supply device such as a measuring device.

Although the thermoelectric material measurement equipment for the bulk type has been developed and used until now, there has been little development about the technology for measuring and evaluating the characteristics of the nano thin film type thermoelectric material, and the standardization of the measurement method has not been performed yet. There is a problem in that the reliability of the indicator results is poor. Therefore, in order to research and develop nano-thin-film thermoelectric materials with excellent performance and to commercialize device applications, it is essential to develop techniques and equipment capable of objectively evaluating their characteristics.

The ZT coefficient is used as an indicator of the performance for evaluating the efficiency of thermoelectric materials and is expressed by the following equation.

  In the above equation, the physical properties that determine the performance of the thermoelectric material are influenced by the Seebeck coefficient S, the electric conductivity σ, the thermal conductivity κ, and the double Seebeck coefficient S as the square root.

The existing Seebeck coefficient measurement system provides reliable data for thermoelectric materials with a thickness of more than 1 micrometer. However, there is a problem that reliability is lowered due to errors occurring in thin film thermoelectric materials having nano thicknesses which are being actively developed recently.

Therefore, there is a need for an apparatus and method for measuring a Seebeck coefficient optimized for the properties of nano-scale thin film thermoelectric materials.

A related prior art is Korean Patent No. 1082353 (registered on November 4, 2011, Thermoelectric Device Evaluation Apparatus and Thermoelectric Device Evaluation System Using the same).

The present invention provides an apparatus and a method for evaluating the performance of a thin film thermoelectric material for measuring a Seebeck coefficient of a nano-thin film type thermoelectric material.

The present invention also provides an apparatus and a method for evaluating the performance of a non-contact thin film thermoelectric material for measuring properties of a nano-thin-film thermoelectric material, in which a measurement probe for temperature measurement and a deviation element due to contact between thin films are excluded .

Also, the present invention provides an apparatus and a method for evaluating the performance of a thin film thermoelectric material, which automatically measures the heat flow direction and accordingly measures a bekk coefficient, in order to eliminate the possibility of deviation in the heat flow direction for the same thin film thermoelectric material .

It is another object of the present invention to provide an apparatus and a method for evaluating performance of a thin film thermoelectric material, which is capable of measuring a potential difference several times in the same temperature range to derive an average value to improve precision.

The technical objects to be achieved by the present invention are not limited to the above-mentioned technical problems.

According to an aspect of the present invention, there is provided an apparatus for evaluating the performance of a thin film thermoelectric material, including: a temperature control stage for controlling temperatures of both ends of the thin film thermoelectric material; A temperature detector for measuring a temperature of a surface of the thin film thermoelectric material; A measuring unit for measuring electrical characteristics generated by contacting the surface of the thin-film thermoelectric material; And a main controller for receiving the electrical characteristic information measured by the measuring unit according to the temperature information of the thin film thermoelectric material detected by the temperature detector to derive a bekking coefficient.

Specifically, the temperature detector may be a non-contact temperature sensor or an infrared camera.

The apparatus may further include a stage controller for controlling the temperature control stage.

The measurement unit may include a probe station and a measurement module,

Wherein the probe station comprises: a probe pin for directly contacting the surface of the thin-film thermoelectric material to measure electrical characteristics;

A height adjustment knob for moving the probe pin in the Z-axis direction to contact the thin film thermoelectric material; And

And a load adjusting unit for adjusting the probe pin to press the thin film thermoelectric material with a predetermined load when the probe pin and the thin film thermoelectric material are in contact with each other,

The measurement module can digitize electrical characteristics measured by the probe pin.

In addition, the probe pin can contact the surface of the same position of the thin film thermoelectric material measured by the temperature detector.

The apparatus may further include a vacuum chamber enclosing the temperature control stage, the temperature detector, and the measurement unit so that the temperature control stage, the temperature detector, and the measurement unit can perform in a vacuum state.

According to another aspect of the present invention, there is provided a method for evaluating the performance of a thin film thermoelectric material, the method comprising: a first step of positioning the thin thermoelectric material on a temperature control stage;

A second step of setting a start temperature, a temperature deviation (DELTA T), and a test period of the thin film thermoelectric material; A third step of raising and lowering the temperature control stage to a start temperature or a set temperature; A fourth step of measuring a voltage of the thin film thermoelectric material when a predetermined time has elapsed after the temperature of the thin film thermoelectric material reaches the start temperature or the set temperature by the temperature control stage; And a fifth step of repeating the third and fourth steps to measure a potential difference with respect to a temperature deviation of a start temperature or a set temperature and to obtain a slope (a Seebeck coefficient) by applying a linear fit method, May be a temperature set according to the test section from the start temperature.

Specifically, the temperature control stage may set different temperatures to generate temperature deviations at both ends of the thin film thermoelectric material.

Further, when setting the start temperature, the temperature deviation (DELTA T), and the test section, it is possible to further set the number of times of sampling that can be repeatedly tested in the same test section.

As described above, according to the present invention, in the conventional contact type temperature and potential difference measurement method, the temperature is measured in a non-contact manner and a potential difference is applied to a probe pin having a diameter of 0.2 to 0.3 탆, Thereby minimizing the measurement error that may occur.

In addition, the present invention has an effect that the load adjusting device of the probe station keeps the pressing force of the thin film thermoelectric material constant with the probe pin, thereby eliminating the cause of the deviation of the potential difference caused by the difference of the contact condition and improving the measurement accuracy .

In addition, the present invention has two independent temperature control stages, and it is possible to easily set the heating-cooling or the cooling-heating by converting the temperature of the temperature control stage at both ends in the same place without moving the thin film thermoelectric material have.

1 is a schematic view showing an apparatus for evaluating the performance of a thin-film thermoelectric material according to an embodiment of the present invention.
2 is a view showing a temperature detection unit and a temperature control stage of a performance evaluation apparatus for a thin film thermoelectric material according to an embodiment of the present invention.
3 is an image showing a thin film thermoelectric material positioned at the top of a temperature control stage of the apparatus for evaluating the performance of a thin film thermoelectric material according to an embodiment of the present invention.
4 is an image of the top of a temperature sensor stage of a device for evaluating the performance of a bar thermoelectric material according to an embodiment of the present invention,
5 is a schematic diagram of an apparatus for evaluating the performance of a thin film thermoelectric material according to an embodiment of the present invention.
6 is a flowchart illustrating a method of evaluating the performance of a thin-film thermoelectric material according to an embodiment of the present invention.
7 is a graph showing a change in potential difference according to a temperature deviation using an apparatus and a method for evaluating performance of a thin film thermoelectric material according to an embodiment of the present invention.
8 is a graph showing changes in the Seebeck coefficient according to temperature using an apparatus and a method for evaluating the performance of a thin-film thermoelectric material according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components are denoted by the same reference symbols whenever possible. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail.

The present invention measures the Seebeck coefficient (S) among the items for obtaining the figure of merit (ZT) for evaluating the performance of the thin film thermoelectric material, and the measurement and calculation of the thermal conductivity and the electric conductivity of the thermoelectric material are omitted .

1 to 5 are views showing an apparatus for evaluating the performance of a thin film thermoelectric material according to an embodiment of the present invention. The performance evaluation apparatus 100 includes a temperature control stage 110, a temperature detection unit 120, a measurement unit 130, , And a main control unit 140. [

The temperature control stage 110 is composed of two independent first temperature control stages 110a and a second temperature control stage 110b and the two ends of the thin film thermoelectric material 1 are connected to the first temperature control stage 110a, And the upper part of the second temperature control stage 110b to adjust the temperature for each part of the thin film thermoelectric material 1.

At this time, the temperature control stage 110 may be formed with a seating groove (not shown) so that the thin thermoelectric material 1 can be seated.

The temperature control stage 110 further includes a stage controller 150 for controlling the temperature of each stage so as to realize a temperature deviation in both end faces of the thin film thermoelectric material by heating and cooling.

The stage controller 150 can control the temperature within 0.5 占 폚 by the SSR ON / OFF control or the current control method.

Since the thin film thermoelectric material 1 may be measured differently depending on the direction of heat flow with respect to the same specimen according to the manufacturing method, the temperature control stage 100 and the stage controller 150 may be operated under the same test conditions The direction of the heat flow can be automatically converted into the measured average value.

Accordingly, the present invention includes two independent temperature control stages 110 to convert temperatures of both ends of the temperature control stage 110 in the same place without moving the thin film thermoelectric material 1 to perform heating-cooling or cooling- There is an effect that the heating can be easily set.

The heat control device 100 further includes a heat sink 111 disposed at a lower end of the temperature control stage 110 to eliminate the heat generated by the temperature control stage 110.

The temperature detecting unit 120 measures the surface temperature emitted from the surface of the thin film thermoelectric material 1. Here, the temperature detector 120 may be a non-contact temperature sensor or an infrared camera. FIG. 4 is a view of the temperature control stage 110 taken by an infrared camera, and it is possible to easily detect the temperature change of the thin film thermoelectric material 1. FIG.

Here, it is preferable that the non-contact type temperature sensor is provided at the upper end of the temperature control stage 110, and the infrared camera is preferably positioned at a height at which the temperature control stage 110 can be detected.

The temperature detecting unit 120 further includes a support member 170 for supporting the temperature detecting unit 120 since the upper surface of the temperature controlling stage 110 should be detected at an upper end spaced apart from the temperature controlling stage 110 by a predetermined distance. At this time, the support member 170 is formed to adjust the height of the temperature detector 120.

The measuring unit 130 is divided into a probe station 131 and a measuring module 132. The probe station 131 includes a probe pin 131a, a height adjusting knob 131b and a load adjusting unit 131c.

Here, the probe pin 131a directly contacts the surface of the thin-film thermoelectric material 1 to measure electrical characteristics. At this time, the probe pin 131a has a thickness of 0.2 to 0.3 탆 and is made of platinum to minimize electrical resistance.

Therefore, the present invention has the effect of minimizing the deviation of the contact condition between the probe pin 131a and the thin-film thermoelectric material 1. [

The probe pin 131a can be set in advance on the surface of the thin thermoelectric material 1 prepared by the thin thermoelectric material 1 at the upper end of the temperature control stage 110 and directed by the measuring unit 130. [

When the temperature of the thin film thermoelectric material 1 is detected using the non-contact type temperature sensor, the probe pin 131a is located at the same position as the position where the laser is irradiated, and the temperature of the thin film thermoelectric material 1 is detected The error rate can be reduced by positioning the infrared camera at the same position as the infrared camera.

The height adjusting knob 131b moves the probe pin 131a in the Z-axis direction to bring the thin-film thermoelectric material 1 into contact.

The load adjusting unit 131c adjusts the probe pin 131a so that the probe pin 131a can press the thin film thermoelectric material 1 under a constant load when the probe pin 131a contacts the thin film thermoelectric material 1. [ At this time, the load adjusting unit 131c applies a spring structure to always keep the load in contact with the surface of the thin thermoelectric material constant.

Therefore, the present invention can improve the measurement accuracy by eliminating the cause of the deviation of the potential difference by keeping the pressing force of the load adjusting device 131c of the probe station 131 pressing the thin thermoelectric material 1 constant with the probe pin 131a .

In addition, the measurement module 132 receives and inputs electrical characteristics including the potential difference measured by the probe pin 131a in real time. The data thus input is transferred to the main control unit 140.

The temperature control stage 110, the temperature detection unit 120, and the measurement unit 130 may be surrounded by the vacuum chamber 160 so that the measurement can be performed in a vacuum state. The vacuum chamber 160 may be coated with an infrared shielding film or the like on the outer surface of the vacuum chamber 160 to block the infrared rays reflected from the surrounding environment when the temperature sensor is used.

Here, when the vacuum chamber 160 is applied, there is an effect that it is not affected by convection.

The main control unit 140 receives the electrical characteristic information measured by the measuring unit 130 according to the temperature information of the thin film thermoelectric material 1 detected by the temperature detecting unit 120 and derives a bekking coefficient.

In addition, the main control unit 140 can monitor the set temperature by communicating with the stage controller 150.

The performance evaluation method of the thin film thermoelectric material 1 according to the embodiment of the present invention having the above structure is shown in FIG.

First, the thin film thermoelectric material 1 is placed on the top of the temperature control stage 110 (S10). At this time, the thin-film thermoelectric material 1 places the thin-film thermoelectric material on a temperature control stage 110 having an independent stage, one side of which is located at the upper end of the first temperature control stage 110a, And is preferably located at the upper end of the stage 110b

The temperature detection unit 120 and the probe pins 131a of the measurement unit 131 are directed to the same position in the direction of the thin film thermoelectric material 1 located at the upper end of the temperature control stage 110.

That is, the probe pin 131a is positioned at the same position as the surface of the thin-film thermoelectric material 1 detected by the temperature detecting unit 120.

Next, a start temperature, a temperature deviation (DELTA T), and a test period of the thin film thermoelectric material 1 are set (S20). Here, the start temperature means a temperature at which the test starts, the temperature deviation means a temperature difference between both sides of the temperature control stage 110, and the test period means a temperature interval to be performed after the start temperature.

In addition, the number of sampling times can be set so that sampling can be performed several times at the same temperature and the same deviation, and sampling can be performed several times in order to increase the reliability according to the temperature error.

Here, the temperature deviation may be set based on the starting temperature, or may be set based on either one of the temperature control stages.

For example, when the temperature deviation is set based on the start temperature, when the start temperature is 20 占 폚 and the temperature deviation is 2 占 폚, the first temperature control stage 110a is 19 占 폚 and the second temperature control stage 110b ) Can be set to 21 [deg.] C.

When the temperature of the one temperature control stage 110 is set as a reference, the first temperature control stage 110a is 20 占 폚 when the start temperature is 20 占 폚 and the temperature deviation is 2 占 폚, 2 temperature control stage 110b may be set to 22 deg.

That is, the user sets a plurality of start temperatures and temperature deviations, respectively, and sets the next temperature and temperature deviations to the preset test periods without resetting when the corresponding start temperature and temperature deviations are measured. In the following, the temperature set from the start temperature to the test zone is called the set temperature.

Next, the temperature control stage 110 raises or lowers the temperature of the temperature control stage 110 (S30). At this time, the temperature control stage 110 sets the temperature of the temperature control stage 110 differently So that temperature differences are generated at both ends of the thin film thermoelectric material (1).

Next, it is determined whether the thin film thermoelectric material 1 reaches the start temperature and the set temperature by the temperature control stage and is maintaining the stabilization temperature (S40). At this time, the temperature of the thin film thermoelectric material 1 is monitored by the temperature detector 120 provided at the upper part in real time, and the temperature is maintained for about 1 minute to 2 minutes at the reference temperature, and it can be determined that the stabilization step is reached.

Next, if the temperature of the thin film thermoelectric material 1 reaches the start temperature or the set temperature, the voltage at both ends of the thin thermoelectric material 1 is measured (S50). At this time, the stabilization temperature can be determined as the stabilized temperature if the stabilization temperature exceeds the preset time while the same temperature is maintained after the start temperature or the set temperature is reached, and the probe pin 131a measure the voltage. At this time, measurement is performed by the predetermined sampling number.

Subsequently, the temperature of the temperature control stage 110 is changed by the start temperature or the set temperature and the temperature deviation (S60). At this time, when the start temperature is 20 占 폚 and the temperature deviation is 2 占 폚, the next set temperature is 22 占 폚. This will be described later.

When the temperature of the temperature control stage 110 is changed, the temperature measurement of the temperature control stage 110 is repeatedly performed from the temperature rising or falling of the temperature control stage 110. When the voltage measurement for the set start or set temperature and the temperature deviation is completed, The potential difference with respect to the temperature deviation is measured and the slope (the Seebeck coefficient) is derived by applying the linear fit method (S70).

If the starting temperature is 20 ° C, the temperature deviation is 2 ° C, the test period is 5, and the sampling number is 5 times based on the first temperature control stage 110a, the first temperature control stage 110a, Is 20 deg. C, and the second temperature control stage 110b is 22 deg. C, and sampling is performed five times in this interval. At this time, the actual temperature deviation may be about 1.9 to 2.1 占 폚.

The first temperature control stage 110a varies in the order of 22 deg. C, 24 deg. C, 26 deg. C, 28 deg. C and 30 deg. C in the next test interval, , 26 ° C, 28 ° C, 30 ° C, and 32 ° C in order to measure the voltage at both ends of the thermoelectric material.

That is, the Seebeck coefficient is derived from the temperature deviation and the potential difference.

Table 1 below shows the results of measuring the temperature difference voltage using the apparatus and method as described above when the starting temperature is 293 K, the temperature deviation is 0.5 K, the test section is 4, and the sampling is 5 times. 7, as shown in FIG. 7, in the same condition, the distribution has a certain range in the actual measurement. In order to digitize and data thereof, the slope is calculated by applying a first-order linear fitting method, ) Is 88.189.

? T (k) 0.5 0.6 0.5 0.6 0.5 One 1.1 1.1 One 1.1 △ V (㎶) 40 42 44 43 41 78 81 79 77 80 ? T (k) 1.5 1.5 1.5 1.6 1.6 2 2.1 2 2 2 △ V (㎶) 125 127 124 127 128 169 171 170 176 174

Table 2 shows the obtained Seebeck coefficient for each temperature in the same manner as in Table 1, and a graph of the Seebeck coefficient can be shown in FIG.

T (K) S 293 88.189 313 95.14 333 110.5 353 125.18 373 136.88

The apparatus and method for evaluating the performance of a thin-film thermoelectric material as described above are not limited to the configuration and operation of the embodiments described above. The embodiments may be configured so that all or some of the embodiments may be selectively combined so that various modifications may be made.

1: Thin film thermoelectric material
100: performance evaluation device 110: temperature control stage
110a: first temperature control stage 110b: second temperature control stage
111: heat sink 120: temperature detector
130: measuring part 131: probe station
131a: Probe pin 131b: Height adjustment knob
131c: Load adjustment unit 132: Measurement module
140: main controller 150: stage controller
160: vacuum chamber 170: support member

Claims (9)

A temperature control stage for controlling the temperatures of both ends of the thin film thermoelectric material;
A temperature detector for measuring a temperature of a surface of the thin film thermoelectric material;
A measuring unit for measuring electrical characteristics generated by contacting the surface of the thin-film thermoelectric material;
And a main controller for receiving the electrical characteristic information measured by the measuring unit according to the temperature information of the thin film thermoelectric material detected by the temperature detector to derive a bake stress coefficient,
The temperature control stage generates a temperature variation in both end faces of the thin film thermoelectric material by heating and cooling,
The probe unit includes a probe station and a measurement module. The probe station includes a pin-shaped probe pin formed of platinum to reduce the contact resistance and directly contacting the surface of the thin-film thermoelectric material to measure electrical characteristics. A height adjustment knob for moving the probe pin in the Z-axis direction to contact the thin film thermoelectric material; And a load adjuster for adjusting the probe pin to press the thin film thermoelectric material with a predetermined load when the probe pin and the thin film thermoelectric material are in contact with each other.
The method according to claim 1,
Wherein the temperature detector is a non-contact temperature sensor or an infrared camera.
The method according to claim 1,
And a stage controller for controlling the temperature of the temperature control stage.
The method according to claim 1,
Wherein the measurement module converts the electrical characteristics measured by the probe pin into data.
The method according to claim 1,
Wherein the probe pin contacts a surface of the same position of the thin-film thermoelectric material measured by the detector.
The method according to claim 1,
And a vacuum chamber enclosing the temperature control stage, the temperature detection unit, and the measurement unit so that they can be performed in a vacuum state.
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