Unconventional thermoelectric material and preparation method thereof

Abstract

The invention discloses an unconventional thermoelectric material and a preparation method thereof, the chemical formula of the unconventional thermoelectric material is TiFexRuyCuzSb, and x, y and z are respectively the molecular weight and 1lt of Fe, Ru and Cu in the chemical formula; x + y + zlt; x and z are not 0. The invention provides an unconventional thermoelectric material TiFexRuyCuzSb (1lt; x + y + zlt; (2) the material shows excellent thermoelectric performance, the Seebeck coefficient of the material exceeds 180 [mu] V / K in a certain temperature range, the figure of life (zT) can reach 1.2 at 875 K, the resistivity of TiFexRuyCuzSb shows strict linear temperature dependence in the temperature interval of 14 K to 650 K, the Mott-Ioffe-Regel (MIR) limit is broken through, and the bad metal transmission characteristic of non-quasi particles is shown. The unique transmission characteristic and the high thermoelectric performance benefit from a complicated electronic structure and associated interaction in the TiFexRuyCuzSb, including spin, valence fluctuation and the like, so that the TiFexRuyCuzSb can more efficiently convert heat energy into electric energy in the thermoelectric conversion process, and the energy utilization efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of thermoelectric materials, and in particular to an unconventional thermoelectric material and a preparation method thereof. Background Art

[0002] Thermoelectric technology can directly realize the mutual conversion of heat energy and electrical energy, and has great application potential in deep space exploration, waste heat power generation and all-solid-state refrigeration. In 1822, Seebeck first discovered the thermoelectric effect in metals. In the 1950s, Ioffe proposed the figure-of-merit (zT=S 2 The research focuses on semiconductor thermoelectric materials. The thermoelectric performance is greatly improved by adjusting the transport properties of effective electrons or holes in heavily doped narrow-bandgap semiconductors (such as Bi2Te3, GeTe, CoSb3, SnSe, Mg3Sb2, etc.), especially the modulation of the electronic state density.

[0003] In addition, thermoelectric effects have also been observed at low temperatures in strongly correlated electron systems such as unconventional superconductors and heavy fermions, but their practical value is limited by poor performance. 8+δ Near the superconducting transition temperature, the maximum thermoelectric potential of a superconductor is only 5.5 μV / K, and the zT value is as low as 1.5×10 -5 ; LaFeAsO 0.84 The Seebeck coefficient of iron-based superconductors is -86μV / K at 125K, and the zT value is 0.061; the thermoelectric potential of Yb and Ce-based heavy fermion systems at low temperatures is about 100μV / K, and the zT value is 0.11. The electrical transport properties of these strongly correlated systems cannot be described by quasiparticles within the Fermi liquid framework, and researchers define such materials as unconventional thermoelectric materials.

[0004] Therefore, the unconventional thermoelectric material involved in the present invention refers to a thermoelectric material in which there are no quasiparticles in the non-Fermi liquid (NFL) transmission process, and the carrier scattering is mainly dominated by the dynamic spin and valence fluctuations caused by multi-body electron correlation. At present, among all unconventional thermoelectric materials, it is a major challenge to maintain a high thermoelectric potential as the temperature increases, resulting in a maximum zT value of less than 0.3, which greatly hinders the development of unconventional thermoelectric materials. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides an unconventional thermoelectric material and a preparation method thereof, so as to solve the problem that the existing unconventional thermoelectric materials are difficult to maintain a high thermoelectric potential as the temperature rises.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0007] In the first aspect of the present invention, an unconventional thermoelectric material is provided. The chemical formula of the unconventional thermoelectric material is TiFe x Ru y Cu z Sb, where x, y, and z are the molecular weights of Fe, Ru, and Cu in the chemical formula respectively, 1 < x + y + z < 2, and x and z are not 0.

[0008] Preferably, the chemical formula of the unconventional thermoelectric material is TiFe 0.68 Ru 0.01 Cu 0.38 Sb, TiFe 0.68 Ru 0.02 Cu 0.4 Sb, TiFe 0.68 Ru 0.03 Cu 0.42 Sb, TiFe 0.68 Cu 0.36 Sb, TiFe 0.69 Cu 0.38 Sb, TiFe 0.7 Cu 0.4 Sb, TiFe 0.75 Cu 0.5 Sb.

[0009] Preferably, the Seebeck coefficient of the unconventional thermoelectric material is greater than 180 μV / K, and the zT value is greater than 1.0.

[0010] In the second aspect of the present invention, a preparation method of the above unconventional thermoelectric material is provided. The preparation method includes the following steps:

[0011] Weigh the raw materials;

[0012] Perform arc melting treatment, ball milling treatment, and spark plasma sintering treatment on the raw materials in sequence to obtain the unconventional thermoelectric material.

[0013] Preferably, the step of performing arc melting treatment on the raw materials is specifically: place the weighed raw materials on a water-cooled copper hearth, under the protection of an inert gas, set the melting current to 50 - 120 mA, and the melting time to 5 - 40 s, complete the melting, and obtain an alloy ingot.

[0014] Preferably, during the melting process, add Sb raw materials to the water-cooled copper hearth to compensate for the weight loss caused by the high vapor pressure.

[0015] Preferably, after each melting, turn the alloy ingot over and remelt it, and repeat this process 2 - 8 times.

[0016] Preferably, the steps of the ball milling treatment are specifically as follows: an alloy ingot is ball milled at a rotation speed of 1400 - 2000 r / min for 6 - 120 minutes to obtain alloy powder.

[0017] Preferably, the ball milling treatment is carried out under the protection of an inert gas.

[0018] Preferably, the steps of the spark plasma sintering treatment are specifically as follows: the alloy powder is subjected to spark plasma sintering at a temperature of 600 - 800 °C and a pressure of 30 - 60 MPa for 2 - 15 minutes.

[0019] Beneficial effects:

[0020] The present invention discloses an unconventional thermoelectric material and a preparation method thereof. The unconventional thermoelectric material TiFe x Ru y Cu z Sb (1 < x + y + z < 2, x and z are not 0) exhibits excellent thermoelectric performance. Its Seebeck coefficient exceeds 180 μV / K within a certain temperature range, and the figure of merit (zT) can reach 1.2 at 875 K. In the temperature range from 14 K to 650 K, the resistivity of TiFe x Ru y Cu z Sb shows a strict linear temperature dependence, breaking through the Mott - Ioffe - Regel (MIR) limit and exhibiting the transport characteristics of a bad metal with non - quasiparticles. This unique transport characteristic and high thermoelectric performance are attributed to the complex electronic structure and correlated interactions inside TiFe x Ru y Cu z Sb, including spin and valence state fluctuations, etc. These characteristics enable TiFe x Ru y Cu z Sb to convert thermal energy into electrical energy more efficiently during the thermoelectric conversion process, improving the energy utilization efficiency.

[0021] The preparation method of the present invention adopts conventional arc melting, mechanical alloying and spark plasma sintering technologies. These technologies are mature and reliable, with relatively simple equipment requirements, easy to operate and control. Compared with the traditional complex preparation process, the preparation method of the present invention does not require special equipment and complex operation procedures, reduces the production cost, improves the production efficiency at the same time, is conducive to large - scale production, and provides the possibility for the industrial application of unconventional thermoelectric materials. Description of the Drawings

[0022] Figure 1XRD patterns of the thermoelectric materials prepared in Examples 1-7 of the present invention.

[0023] Figure 2 Variation diagram of the resistivity of the thermoelectric materials prepared in Examples 1-6 of the present invention with temperature.

[0024] Figure 3 Variation diagrams of the Seebeck coefficients and zT values of the thermoelectric materials prepared in Examples 1-4 of the present invention and other thermoelectric materials with temperature. Detailed implementation manners

[0025] The present invention provides an unconventional thermoelectric material and a preparation method thereof. To make the objectives, technical solutions and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] An embodiment of the present invention provides an unconventional thermoelectric material, and the chemical formula of the unconventional thermoelectric material is TiFe x Ru y Cu z Sb, where x, y, and z are the molecular weights of Fe, Ru, and Cu in the chemical formula respectively, 1 < x + y + z < 2, and x and z are not 0.

[0027] The unconventional thermoelectric material TiFe x Ru y Cu z Sb (1 < x + y + z < 2, x and z are not 0) exhibits excellent thermoelectric performance. Its Seebeck coefficient exceeds 180 μV / K within a certain temperature range, and the figure of merit (zT) can reach 1.2 at 875 K. In the temperature range from 14 K to 650 K, the resistivity of TiFe x Ru y Cu z Sb shows a strict linear temperature dependence, breaking through the Mott-Ioffe-Regel (MIR) limit and exhibiting the transport characteristics of a bad metal with non-quasiparticles. This unique transport characteristic and high thermoelectric performance are attributed to the complex electronic structure and correlated interactions inside TiFe x Ru y Cu z Sb, including spin and valence fluctuations, etc. These characteristics enable TiFe x Ru y Cu z Sb to convert thermal energy into electrical energy more efficiently during the thermoelectric conversion process, improving the energy utilization efficiency.

[0028] In some embodiments, the chemical formula of the unconventional thermoelectric material is TiFe 0.68 Ru 0.01 Cu 0.38 Sb、TiFe 0.68 Ru 0.02 Cu 0.4 Sb、TiFe 0.68 Ru 0.03 Cu 0.42 Sb、TiFe 0.68 Cu 0.36 Sb、TiFe 0.69 Cu 0.38 Sb、TiFe 0.7 Cu 0.4 Sb、TiFe 0.75 Cu 0.5 One of Sb.

[0029] In some embodiments, the unconventional thermoelectric material has a Seebeck coefficient greater than 180 μV / K and a zT value greater than 1.0.

[0030] The embodiment of the present invention provides a method for preparing the above-mentioned unconventional thermoelectric material, and the preparation method comprises the following steps:

[0031] Weigh the raw materials;

[0032] The raw materials are sequentially subjected to arc melting treatment, ball milling treatment and spark plasma sintering treatment to obtain the unconventional thermoelectric material.

[0033] The preparation method of the present invention adopts conventional arc melting, mechanical alloying and spark plasma sintering technologies, which are mature and reliable, have relatively simple equipment requirements, and are easy to operate and control. Compared with the traditional complex preparation process, the preparation method of the present invention does not require special equipment and complex operation procedures, reduces production costs, improves production efficiency, is conducive to large-scale production, and provides possibilities for the industrial application of unconventional thermoelectric materials.

[0034] In some embodiments, the step of arc melting the raw materials is specifically as follows: placing the weighed raw materials on a water-cooled copper hearth, under the protection of an inert gas, setting the melting current to 50-120 mA, the single melting time to 5-40 s, melting the front and back sides of the sample 2-8 times, completing the melting, and obtaining an alloy ingot.

[0035] When the melting current is too small, the time is too short, and the number of times is too small, the above five elements cannot be completely melted together. When the melting current is too large, the time is too long, and the number of times is too many, the Sb element will volatilize too much and affect the final composition.

[0036] In some preferred embodiments, the step of arc melting the raw materials is specifically as follows: placing the weighed raw materials on a water-cooled copper hearth, under the protection of an inert gas, setting the melting current to 80 mA, the time to 20 s, melting the front and back sides of the sample 5 times to complete the melting, and obtaining an alloy ingot.

[0037] In some embodiments, during the smelting process, Sb raw material is added to the water-cooled copper hearth to compensate for the weight loss due to the high vapor pressure.

[0038] In some embodiments, the ball milling step is specifically as follows: ball milling the alloy ingot at a rotation speed of 1400-2000 r / min for 6-120 minutes to obtain alloy powder.

[0039] If the ball milling speed is too slow or the time is too short, the smelted ingot cannot be completely crushed. If the speed is too fast or the ball milling time is too long, the sample may be seriously adhered to the ball mill filling, resulting in the loss of the sample.

[0040] In some preferred embodiments, the ball milling step is specifically as follows: ball milling the alloy ingot at a rotation speed of 1725 r / min for 24 minutes to obtain alloy powder.

[0041] In some embodiments, the ball milling process is performed under the protection of an inert gas.

[0042] In some embodiments, the spark plasma sintering treatment step is specifically: spark plasma sintering the alloy powder at a temperature of 600-800° C. and a pressure of 30-70 MPa for 2-15 minutes.

[0043] If the sintering temperature is too low, the pressure is too small, or the time is too short, the density of the sample may not be guaranteed, thus affecting the electrical properties of the sample; if the sintering temperature is too high, the pressure is too high, or the time is too long, the Cu ions may flow, changing the original composition of the sample and affecting the thermoelectric properties.

[0044] In some preferred embodiments, the spark plasma sintering step is specifically: spark plasma sintering the alloy powder at a temperature of 700° C. and a pressure of 50 MPa for 5 minutes.

[0045] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments, and are only for illustrating the present invention but not limiting the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Example 1

[0047] TiFe 0.68 Cu 0.38 The composition of Sb prepares raw materials and prepares alloy ingots by arc melting: during the arc melting process, it is carried out on a water-cooled copper hearth under Ar protective atmosphere. The arc melting current is 80 mA and the time is 20 s. After one melting is completed, it is turned over and re-melted four times. The uniformity is checked and an appropriate amount of additional Sb is added. The amount of addition is adjusted according to the actual situation.

[0048] During ball milling, the alloy ingot was placed in a stainless steel ball milling jar and ball milled using a SPEX 8000M mixer in an Ar atmosphere glove box. 0.68 Ru 0.01 Cu 0.38 According to the characteristics of Sb, the ball mill speed was set to 1725r / min, and 2 large stainless steel balls and 4 small stainless steel balls were added to ensure that the alloy powder achieved the ideal particle size and uniformity.

[0049] In the sintering step, the ball-milled powder is loaded into a graphite mold with an inner diameter of 12.7 mm and subjected to spark plasma sintering (SPS) in a glove box. The sintering temperature is set to 700°C, the pressure is 50 MPa, and the time is 5 minutes. During this process, the stability of the sintering temperature and pressure is strictly controlled to ensure that the material forms a good crystal structure.

[0050] The resistivity and Seebeck coefficient were tested using professional testing equipment and methods within the corresponding temperature range. The results obtained were consistent with the material performance characteristics described in the present invention, that is, within a wide temperature range, the resistivity showed a linear temperature dependence, the Seebeck coefficient showed a maximum value of 236μV / K, and the zT value reached a maximum of 1.2.

[0051] Example 2

[0052] TiFe 0.68 Ru 0.01 Cu 0.38 The composition of Sb prepares raw materials and prepares alloy ingots by arc melting: during the arc melting process, it is carried out on a water-cooled copper hearth under Ar protective atmosphere. The arc melting current is 80 mA and the time is 20 s. After one melting is completed, it is turned over and re-melted four times. The uniformity is checked and an appropriate amount of additional Sb is added. The amount of addition is adjusted according to the actual situation.

[0053] During ball milling, the alloy ingot was placed in a stainless steel ball milling jar and ball milled using a SPEX 8000M mixer in an Ar atmosphere glove box. 0.68 Ru 0.01 Cu 0.38According to the characteristics of Sb, the ball mill speed was set to 1725r / min, and 2 large stainless steel balls and 4 small stainless steel balls were added to ensure that the alloy powder achieved the ideal particle size and uniformity.

[0054] In the sintering step, the ball-milled powder is loaded into a graphite mold with an inner diameter of 12.7 mm and subjected to spark plasma sintering (SPS) in a glove box. The sintering temperature is set to 700°C, the pressure is 50 MPa, and the time is 5 minutes. During this process, the stability of the sintering temperature and pressure is strictly controlled to ensure that the material forms a good crystal structure.

[0055] The resistivity and Seebeck coefficient were tested using professional testing equipment and methods within the corresponding temperature range. The results obtained are consistent with the material performance characteristics described in this invention, that is, within a wide temperature range, the resistivity shows a linear temperature dependence, the Seebeck coefficient shows a maximum value of 226μV / K, and the zT value reaches a maximum of 1.1

[0056] Example 3

[0057] TiFe 0.68 Ru 0.02 Cu 0.4 The composition of Sb prepares raw materials and prepares alloy ingots by arc melting: during the arc melting process, it is carried out on a water-cooled copper hearth under Ar protective atmosphere. The arc melting current is 80 mA and the time is 20 s. After one melting is completed, it is turned over and re-melted four times. The uniformity is checked and an appropriate amount of additional Sb is added. The amount of addition is adjusted according to the actual situation.

[0058] During ball milling, the alloy ingot was placed in a stainless steel ball milling jar and ball milled using a SPEX 8000M mixer in an Ar atmosphere glove box. 0.68 Ru 0.02 Cu 0.4 The ball mill speed was set to 1725r / min, and 2 large stainless steel balls and 4 small stainless steel balls were added to ensure that the alloy powder achieved the ideal particle size and uniformity.

[0059] In the sintering step, the ball-milled powder is loaded into a graphite mold with an inner diameter of 12.7 mm and subjected to spark plasma sintering (SPS) in a glove box. The sintering temperature is set to 700°C, the pressure is 50 MPa, and the time is 5 minutes. During this process, the stability of the sintering temperature and pressure is strictly controlled to ensure that the material forms a good crystal structure.

[0060] The resistivity and Seebeck coefficient were tested using professional testing equipment and methods within the corresponding temperature range. The results obtained were consistent with the material performance characteristics described in the present invention, that is, within a wide temperature range, the resistivity showed a linear temperature dependence, the Seebeck coefficient showed a maximum value of 217μV / K, and the maximum zT value reached 1.04.

[0061] Example 4

[0062] The process of this embodiment is basically the same as that of embodiment 2, except that: 0.68 Ru 0.03 Cu 0.42 Composition of Sb Prepare raw materials.

[0063] The resistivity and Seebeck coefficient were tested using professional testing equipment and methods within the corresponding temperature range. The results obtained were consistent with the material performance characteristics described in the present invention, that is, within a wide temperature range, the resistivity showed a linear temperature dependence, and the Seebeck coefficient showed a maximum value of 212μV / K.

[0064] Example 5

[0065] The process of this embodiment is basically the same as that of embodiment 1, except that: 0.75 Cu 0.5 Composition of Sb Prepare raw materials.

[0066] The resistivity and Seebeck coefficient were tested using professional testing equipment and methods within the corresponding temperature range. The results obtained were consistent with the material performance characteristics described in the present invention, that is, within a wide temperature range, the resistivity showed a linear temperature dependence, and the Seebeck coefficient showed a maximum value of 183μV / K.

[0067] Example 6

[0068] The process of this embodiment is basically the same as that of embodiment 1, except that: 0.7 Cu 0.4 Composition of Sb Prepare raw materials.

[0069] The resistivity and Seebeck coefficient were tested using professional testing equipment and methods within the corresponding temperature range. The results obtained were consistent with the material performance characteristics described in the present invention, that is, within a wide temperature range, the resistivity showed a linear temperature dependence, and the Seebeck coefficient showed a maximum value of 196μV / K.

[0070] Example 7

[0071] The process of this embodiment is basically the same as that of embodiment 1, except that: 0.69 Cu 0.38 Composition of Sb Prepare raw materials.

[0072] The resistivity and Seebeck coefficient were tested using professional testing equipment and methods within the corresponding temperature range. The results obtained were consistent with the material performance characteristics described in the present invention, that is, within a wide temperature range, the resistivity showed a linear temperature dependence, and the Seebeck coefficient showed a maximum value of 214μV / K.

[0073] Figure 1 XRD diagrams of the thermoelectric materials prepared in Examples 1-7 of the present invention.

[0074] Figure 2 This is a graph showing the change in resistivity of the thermoelectric materials prepared in Examples 1-6 of the present invention with temperature.

[0075] Figure 3 The graphs are the Seebeck coefficients and zT values ​​of the thermoelectric materials prepared in Examples 1-4 of the present invention and other thermoelectric materials as a function of temperature.

[0076] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. An unconventional thermoelectric material, characterized in that: The chemical formula of the unconventional thermoelectric material is TiFe x Ru y Cu z Sb, where x, y, and z are the molecular weights of Fe, Ru, and Cu in the chemical formula, respectively, 1 < x + y + z < 2, and x and z are not zero.

2. The unconventional thermoelectric material according to claim 1, characterized in that: The chemical formula of the unconventional thermoelectric material is TiFe 0.68 Ru 0.01 Cu 0.38 Sb、TiFe 0.68 Ru 0.02 Cu 0.4 Sb、TiFe 0.68 Ru 0.03 Cu 0.42 Sb、TiFe 0.68 Cu 0.36 Sb、TiFe 0.69 Cu 0.38 Sb、TiFe 0.7 Cu 0.4 Sb、TiFe 0.75 Cu 0.5 One of Sb.

3. The unconventional thermoelectric material according to claim 1, characterized in that: The Seebeck coefficient of the unconventional thermoelectric material is greater than 180 μV / K, and the zT value is greater than 1.

0.

4. A method for preparing the unconventional thermoelectric material according to claim 1, characterized in that: The preparation method comprises the following steps: Weigh the raw materials; The raw materials are sequentially subjected to arc melting treatment, ball milling treatment and spark plasma sintering treatment to obtain the unconventional thermoelectric material.

5. The method for preparing unconventional thermoelectric materials according to claim 4, characterized in that: The step of arc melting the raw materials is specifically as follows: placing the weighed raw materials on a water-cooled copper hearth, under the protection of an inert gas, setting the melting current to 50-120 mA, the melting time to 5-40 seconds, completing the melting, and obtaining an alloy ingot.

6. The method for preparing unconventional thermoelectric materials according to claim 5, characterized in that: During the smelting process, Sb raw material is added to the water-cooled copper hearth to compensate for the weight loss due to the high vapor pressure.

7. The method for preparing unconventional thermoelectric materials according to claim 4, characterized in that: After each smelting, the alloy ingot is turned over and re-smelted, and this process is repeated 2-8 times.

8. The method for preparing unconventional thermoelectric materials according to claim 5, characterized in that: The step of ball milling treatment is specifically as follows: ball milling the alloy ingot at a rotation speed of 1400-2000 r / min for 6-120 minutes to obtain alloy powder.

9. The method for preparing unconventional thermoelectric materials according to claim 8, characterized in that: The ball milling process is carried out under the protection of inert gas.

10. The method for preparing unconventional thermoelectric materials according to claim 8, characterized in that: The spark plasma sintering treatment step is specifically: spark plasma sintering the alloy powder at a temperature of 600-800° C. and a pressure of 30-60 MPa for 2-15 minutes.

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