Unconventional thermoelectric material and preparation method therefor

Abstract

Disclosed in the present invention are an unconventional thermoelectric material and a preparation method therefor. The chemical formula of the unconventional thermoelectric material is TiFexRuyCuzSb, wherein x, y and z are respectively the molecule amount of Fe, Ru and Cu in the chemical formula, 1<x+y+z<2, and x and z are not 0. The unconventional thermoelectric material TiFexRuyCuzSb(1<x+y+z<2) provided in the present invention exhibits excellent thermoelectric performance: the Seebeck coefficient thereof exceeds 180 μV / K in a certain temperature range; the figure of merit (zT) can reach 1.2 at 875 K; and the resistivity of TiFexRuyCuzSb exhibits strict linear temperature dependence in the temperature interval of 14 K to 650 K, which breaks through the Mott-Ioffe-Regel (MIR) limit, and exhibits the bad metal transmission properties of non-quasi particles. The unique transmission properties and the high thermoelectric performance benefit from a complicated electronic structure and associated interaction inside TiFexRuyCuzSb, including spin, valence fluctuation, etc., such that TiFexRuyCuzSb can more efficiently convert heat energy into electric energy during the thermoelectric conversion process, thereby improving the energy utilization efficiency.

Description

An unconventional thermoelectric material and its preparation method Technical Field

[0001] This invention relates to the field of thermoelectric materials, and more particularly to an unconventional thermoelectric material and its preparation method. Background Technology

[0002] Thermoelectric technology can directly convert heat energy into electrical energy, and has enormous application potential in fields such as 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) method. 2 Guided by the principle of σT / κ (where S is the Seebeck coefficient, σ is the electrical conductivity, T is the temperature, and κ is the thermal conductivity), the research focus is mainly on semiconductor thermoelectric materials. 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 by modulating the electronic density of states, the thermoelectric performance has been greatly improved.

[0003] Furthermore, 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. For example, Bi₂Sr₂CaCu₂O 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 × 10⁻⁶. -5 ;LaFeAsO 0.84 Iron-based superconductors exhibit a Seebeck coefficient of -86 μV / K and a zT value of 0.061 at 125 K; Yb and Ce-based heavy fermion systems have a thermoelectric potential of approximately 100 μV / K and a zT value of 0.11 at low temperatures. The electrical transport properties of these strongly correlated systems cannot be described by quasi-particles within the Fermi liquid framework, leading researchers to define such materials as unconventional thermoelectric materials.

[0004] Therefore, the unconventional thermoelectric materials involved in this invention refer to thermoelectric materials in which quasi-particles do not exist during non-Fermi liquid (NFL) transport, and where carrier scattering is mainly dominated by dynamic spin and valence fluctuations caused by many-body electron correlation. Currently, maintaining a high thermoelectric potential with increasing temperature is a major challenge in all unconventional thermoelectric materials, resulting in a maximum zT value that is usually less than 0.3, which greatly hinders the development of unconventional thermoelectric materials. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides an unconventional thermoelectric material and its preparation method, thereby solving the problem that 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, 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.

[0008] Preferably, the chemical formula of the unconventional thermoelectric material is TiFe 0.68 Ru[[ID=十七]] 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, and 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 smelting is completed, the alloy ingot is turned over and remelted, and this is repeated 2 - 8 times.

[0016] Preferably, the steps of the ball milling treatment are specifically as follows: the alloy ingot is ball milled at a rotational 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. Beneficial effects:

[0019] The present invention discloses an unconventional thermoelectric material and its preparation method. 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 within TiFe x Ru y Cu z Sb, including spin and valence fluctuations, etc. These characteristics enable TiFe [[ID=​​​​​​​​​​​​Figure 1 is the XRD pattern of the thermoelectric materials prepared in Examples 1-7 of the present invention.

[0022] Figure 2 is the graph of the resistivity of the thermoelectric materials prepared in Examples 1-6 of the present invention varying with temperature.

[0023] Figure 3 is the graph of the Seebeck coefficients and zT values of the thermoelectric materials prepared in Examples 1-4 of the present invention and other thermoelectric materials varying with temperature. Detailed implementation manners

[0024] The present invention provides an unconventional thermoelectric material and its preparation method. To make the purpose, technical solution 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.

[0025] 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.

[0026] 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, for TiFe x Ru y Cu z Sb, the resistivity 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 due to the complex electronic structure and correlation 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.

[0027] In some embodiments, the unconventional thermoelectric material has the chemical formula 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 the Sb types.

[0028] In some embodiments, the Seebeck coefficient of the unconventional thermoelectric material is greater than 180 μV / K, and the zT value is greater than 1.0.

[0029] This invention provides a method for preparing the above-mentioned unconventional thermoelectric material, the method comprising the following steps:

[0030] Weigh the raw materials;

[0031] The raw materials are subjected to arc melting, ball milling and spark plasma sintering in sequence to obtain the unconventional thermoelectric material.

[0032] The preparation method of this invention employs conventional electric arc melting, mechanical alloying, and spark plasma sintering techniques. These techniques are mature and reliable, require relatively simple equipment, and are easy to operate and control. Compared with traditional complex preparation processes, the preparation method of this invention does not require special equipment or complex operating procedures, reducing production costs while improving production efficiency. This facilitates large-scale production and makes it possible for the industrial application of unconventional thermoelectric materials.

[0033] In some embodiments, the step of arc melting the raw material specifically involves: placing the weighed raw material on a water-cooled copper furnace bed, under the protection of an inert gas, setting the melting current to 50-120mA, the single melting time to 5-40s, melting both sides of the sample 2-8 times to complete the melting and obtain an alloy ingot.

[0034] When the melting current is too low, the time is too short, or the number of times is too few, the above five elements cannot be completely melted together. When the melting current is too high, the time is too long, or the number of times is too many, the Sb element will volatilize too much, affecting the final composition.

[0035] In some preferred embodiments, the step of performing electric arc melting on the raw materials specifically involves: placing the weighed raw materials on a water-cooled copper furnace bed, and under the protection of an inert gas, setting the melting current to 80mA and the time to 20s, melting the sample five times on both sides to complete the melting process and obtain an alloy ingot.

[0036] In some implementations, Sb raw material is added to the water-cooled copper furnace bed during the smelting process to compensate for weight loss due to high vapor pressure.

[0037] In some embodiments, the ball milling process specifically involves: ball milling the alloy ingot at a speed of 1400-2000 r / min for 6-120 minutes to obtain alloy powder.

[0038] If the ball mill 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 stick to the ball milling pot, resulting in the loss of the sample.

[0039] In some preferred embodiments, the ball milling step specifically involves: ball milling the alloy ingot at a speed of 1725 r / min for 24 minutes to obtain alloy powder.

[0040] In some embodiments, the ball milling process is carried out under inert gas protection.

[0041] In some embodiments, the spark plasma sintering process specifically involves: sintering the alloy powder at a temperature of 600-800°C and a pressure of 30-70 MPa for 2-15 minutes using spark plasma sintering.

[0042] If the sintering temperature is too low, the pressure is too low, 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, Cu ions may flow, changing the original composition of the sample and affecting the thermoelectric properties.

[0043] In some preferred embodiments, the spark plasma sintering process specifically involves: sintering the alloy powder at a temperature of 700°C and a pressure of 50 MPa for 5 minutes using spark plasma sintering.

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are merely some embodiments of the present invention, not all embodiments, and are intended only to illustrate the present invention and not to limit it. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] TiFe 0.68 Cu 0.38 The raw materials for Sb composition are prepared by preparing alloy ingots through electric arc melting: During the electric arc melting process, it is carried out on a water-cooled copper furnace bed under an Ar protective atmosphere. The electric arc melting current is 80mA and the time is 20s. After one melting is completed, it is flipped and remelted four times. The uniformity is checked and an appropriate amount of additional Sb is added. The amount added is adjusted according to the actual situation.

[0047] During ball milling, the alloy ingot is placed in a stainless steel ball mill jar and ball milled using a SPEX 8000M mixer within an Ar atmosphere glove box. (Based on TiFe...) 0.68 Ru 0.01 Cu 0.38 The Sb mill is characterized by a ball mill speed of 1725 r / min, with the addition of 2 large stainless steel balls and 4 small stainless steel balls to ensure that the alloy powder achieves the ideal particle size and uniformity.

[0048] In the sintering step, the ball-milled powder was loaded into a graphite mold with an inner diameter of 12.7 mm and sintered by spark plasma sintering (SPS) in a glove box. The sintering temperature was set at 700℃, the pressure at 50 MPa, and the time at 5 minutes. During this process, the stability of the sintering temperature and pressure was strictly controlled to ensure that the material formed a good crystal structure.

[0049] Resistivity and Seebeck coefficient were tested using specialized testing equipment and methods within the corresponding temperature range. The results obtained conform to the material performance characteristics described in this invention, namely, the resistivity exhibits a linear temperature dependence over a wide temperature range, the Seebeck coefficient reaches a high value of 236 μV / K, and the zT value reaches a maximum of 1.2.

[0050] Example 2

[0051] TiFe 0.68 Ru 0.01 Cu 0.38 The raw materials for Sb composition are prepared by preparing alloy ingots through electric arc melting: During the electric arc melting process, it is carried out on a water-cooled copper furnace bed under an Ar protective atmosphere. The electric arc melting current is 80mA and the time is 20s. After one melting is completed, it is flipped and remelted four times. The uniformity is checked and an appropriate amount of additional Sb is added. The amount added is adjusted according to the actual situation.

[0052] During ball milling, the alloy ingot is placed in a stainless steel ball mill jar and ball milled using a SPEX 8000M mixer within an Ar atmosphere glove box. (Based on TiFe...) 0.68 Ru 0.01 Cu 0.38The Sb mill is characterized by a ball mill speed of 1725 r / min, with the addition of 2 large stainless steel balls and 4 small stainless steel balls to ensure that the alloy powder achieves the ideal particle size and uniformity.

[0053] In the sintering step, the ball-milled powder was loaded into a graphite mold with an inner diameter of 12.7 mm and sintered by spark plasma sintering (SPS) in a glove box. The sintering temperature was set at 700℃, the pressure at 50 MPa, and the time at 5 minutes. During this process, the stability of the sintering temperature and pressure was strictly controlled to ensure that the material formed a good crystal structure.

[0054] Resistivity and Seebeck coefficient were tested using specialized testing equipment and methods within the corresponding temperature range. The results obtained conform to the material performance characteristics described in this invention, namely, resistivity exhibits a linear temperature dependence over a wide temperature range, the Seebeck coefficient reaches a high value of 226 μV / K, and the zT value reaches a maximum of 1.1.

[0055] Example 3

[0056] TiFe 0.68 Ru 0.02 Cu 0.4 The raw materials for Sb composition are prepared by preparing alloy ingots through electric arc melting: During the electric arc melting process, it is carried out on a water-cooled copper furnace bed under an Ar protective atmosphere. The electric arc melting current is 80mA and the time is 20s. After one melting is completed, it is flipped and remelted four times. The uniformity is checked and an appropriate amount of additional Sb is added. The amount added is adjusted according to the actual situation.

[0057] During ball milling, the alloy ingot is placed in a stainless steel ball mill jar and ball milled using a SPEX 8000M mixer within an Ar atmosphere glove box. (Based on TiFe...) 0.68 Ru 0.02 Cu 0.4 The Sb mill is characterized by a ball mill speed of 1725 r / min, with the addition of 2 large stainless steel balls and 4 small stainless steel balls, ensuring that the alloy powder achieves the ideal particle size and uniformity.

[0058] In the sintering step, the ball-milled powder was loaded into a graphite mold with an inner diameter of 12.7 mm and sintered by spark plasma sintering (SPS) in a glove box. The sintering temperature was set at 700℃, the pressure at 50 MPa, and the time at 5 minutes. During this process, the stability of the sintering temperature and pressure was strictly controlled to ensure that the material formed a good crystal structure.

[0059] Resistivity and Seebeck coefficient were tested using specialized testing equipment and methods within the corresponding temperature range. The results obtained conform to the material performance characteristics described in this invention, namely, the resistivity exhibits a linear temperature dependence over a wide temperature range, the Seebeck coefficient reaches a high value of 217 μV / K, and the zT value reaches a maximum of 1.04.

[0060] Example 4

[0061] The process in this embodiment is basically the same as that in Embodiment 2, except that TiFe is used. 0.68 Ru 0.03 Cu 0.42 Preparation of raw materials for Sb composition.

[0062] Resistivity and Seebeck coefficient were tested using specialized testing equipment and methods within the corresponding temperature range. The results obtained conform to the material performance characteristics described in this invention, namely, the resistivity exhibits a linear temperature dependence over a wide temperature range, and the Seebeck coefficient reaches a high value of 212 μV / K.

[0063] Example 5

[0064] The process in this embodiment is basically the same as in Embodiment 1, except that TiFe is used. 0.75 Cu 0.5 Preparation of raw materials for Sb composition.

[0065] Resistivity and Seebeck coefficient were tested using specialized testing equipment and methods, and measurements were performed within the corresponding temperature range. The results obtained conform to the material performance characteristics described in this invention, namely, the resistivity exhibits a linear temperature dependence over a wide temperature range, and the Seebeck coefficient reaches a high value of 183 μV / K.

[0066] Example 6

[0067] The process in this embodiment is basically the same as in Embodiment 1, except that TiFe is used. 0.7 Cu 0.4 Preparation of raw materials for Sb composition.

[0068] Resistivity and Seebeck coefficient were tested using specialized testing equipment and methods, and measurements were performed within the corresponding temperature range. The results obtained conform to the material performance characteristics described in this invention, namely, the resistivity exhibits a linear temperature dependence over a wide temperature range, and the Seebeck coefficient reaches a high value of 196 μV / K.

[0069] Example 7

[0070] The process in this embodiment is basically the same as in Embodiment 1, except that TiFe is used. 0.69 Cu 0.38 Preparation of raw materials for Sb composition.

[0071] Resistivity and Seebeck coefficient were tested using specialized testing equipment and methods within the corresponding temperature range. The results obtained conform to the material performance characteristics described in this invention, namely, the resistivity exhibits a linear temperature dependence over a wide temperature range, and the Seebeck coefficient reaches a high value of 214 μV / K.

[0072] Figure 1 shows the XRD patterns of the thermoelectric materials prepared in Examples 1-7 of this invention.

[0073] Figure 2 shows the resistivity of the thermoelectric materials prepared in Examples 1-6 of this invention as a function of temperature.

[0074] Figure 3 shows the Seebeck coefficients and zT values ​​of the thermoelectric materials prepared in Examples 1-4 of this invention and other thermoelectric materials as a function of temperature.

[0075] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

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 unconventional thermoelectric material has the chemical formula 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 the Sb types.

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 includes the following steps: Weigh the raw materials; The raw materials are subjected to arc melting, ball milling and spark plasma sintering in sequence to obtain the unconventional thermoelectric material.

5. The method for preparing unconventional thermoelectric materials according to claim 4, characterized in that, The steps for arc melting the raw materials are as follows: the weighed raw materials are placed on a water-cooled copper furnace bed, and under the protection of inert gas, the melting current is set to 50-120mA and the melting time is 5-40s to complete the melting and obtain 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 furnace bed to compensate for the weight loss caused by the high vapor pressure.

7. The method for preparing unconventional thermoelectric materials according to claim 4, characterized in that, After each melting process, the alloy ingot is flipped and remelted, and this process is repeated 2-8 times.

8. The method for preparing unconventional thermoelectric materials according to claim 5, characterized in that, The ball milling process specifically involves: ball milling the alloy ingot at a 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 was carried out under inert gas protection.

10. The method for preparing unconventional thermoelectric materials according to claim 8, characterized in that, The specific steps of the discharge plasma sintering process are as follows: the alloy powder is subjected to discharge plasma sintering at a temperature of 600-800℃ and a pressure of 30-60MPa for 2-15 minutes.

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