JP7217547B2 - A method for rapid production of n-type Mg3Sb2-based materials with high thermoelectric performance - Google Patents

Description

The present invention relates to the technical field of new energy materials, and in particular to a method for rapidly producing n-type Mg ₃ Sb ₂ -based materials with high thermoelectric performance.

Thermoelectric materials are new functional materials that realize interconversion of electrical energy and thermal energy by utilizing the transport of carriers (electrons or holes) and phonons inside the material. Thermoelectric conversion technology is a green and environmentally friendly energy technology with advantages such as no pollution, no mechanical moving parts, no noise, and high reliability. At present, thermoelectric conversion devices are mainly applied in industrial waste heat, environmental energy recovery, temperature difference thermoelectric generation and thermoelectric refrigeration. For example, temperature difference power generation is currently mainly applied in fields such as aerospace, deep-sea exploration, factory waste heat recovery and high-mountain polar exploration, and thermoelectric refrigeration is mainly applied in some micro-refrigeration devices. The performance of thermoelectric materials is commonly measured by the dimensionless thermoelectric figure of merit (ZT), where the ZT value is expressed by the formula ZT=S ² σT/, where S, σ, T, κ are the Seebeck coefficients, electrical conductivity, absolute temperature, and thermal conductivity. Currently, the energy conversion efficiency of conventional heat engines is 35%, whereas the energy conversion efficiency of thermoelectric materials is only 6-10%, which greatly limits the large-scale application of thermoelectric materials. In the 1990s, Slack et al. proposed the ideal concept of "phonon glass-electron crystals" for thermoelectric materials, stating that a good thermoelectric material would have a low thermal conductivity similar to that of glass and the good conductivity of crystals. indicates that it should The proposal of this concept enlightened the subsequent discovery of high-performance thermoelectric materials with special cage-like structures such as filled skutterudite, cage-like compounds. After the 21st century, some new theories of thermoelectric transport and proposals of new mechanisms have promoted the further development of thermoelectric materials, and the ZT values of some thermoelectric systems have even exceeded 2. At present, the main thermoelectric material systems include Bi ₂ Te ₃ -based alloys, oxide thermoelectric materials, cage structure compounds, two-dimensional layered thermoelectric materials, Half-Heusler alloys and Zintl phase compounds. Mg ₃ Sb ₂ -based thermoelectric materials belong to Zintl phase compounds, have high carrier mobility, low intrinsic lattice thermal conductivity, and “phonon glass-electron crystal” transport properties, and are thermoelectric materials with high application prospects. is.

The object of the present invention is that the raw material composition is Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y , where x=0 to 0.1, y=0 to 0.1, x and y represent atomic percentages. , the selected raw material price is low, and the n-type _{Mg3Sb2 -} based thermoelectric material can be produced quickly, efficiently, energy-savingly and at low cost by the one-step ball mill method, the production method is simple, Green, environmentally friendly, phase-pure, n-type Mg ₃ Sb ₂ -based thermoelectric materials can be rapidly produced on a large scale, and the materials are highly reproducible, have excellent thermal stability, and are 0.90 W m ⁻¹ . It has the lowest thermal conductivity value of K ⁻¹ and the highest power factor of 2451.70 μW m ⁻¹ K ⁻² at 623 K, the highest value of the system to date, and the highest thermoelectric figure of merit ZT=1.8. is one of the maximum values of the current system, the Mg element volatilizes in the conventional high-temperature melting and two-stage high-energy ball milling method, the solid-phase reaction sealing tube conditions are complicated, and the manufacturing process and time are long. The object of the present invention is to provide an n-type _{Mg3Sb2 -} based thermoelectric material with high thermoelectric performance that solves the problem and a method for producing the same.

The present invention is realized by the following technical solutions:

An n-type Mg ₃ Sb ₂ based thermoelectric material with high thermoelectric performance having a raw material composition of Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y where x=0-0.1 and y=0-0 .1, x, y represent atomic percentages.

Preferably, the thermoelectric performance of the material is enhanced when x=0.01-0.07 and y=0.01-0.07.

Most preferably, when x=0.02 and y=0.01, the ZT value of the resulting n _- type _Mg3Sb2 thermoelectric material is 1.8 at 723K.

The method for producing the n-type _{Mg3Sb2 -} based thermoelectric material with high thermoelectric performance comprises:
A step of sequentially weighing magnesium powder, antimony powder, bismuth powder, yttrium powder, and _selenium powder in a chemical composition _{Mg3.2 -xYxSb1.5Bi0.5- ySey in} an atmosphere of high-purity argon. (1) and
Under the protection of high-purity argon, the weighed powder is ball-milled, the rotation speed of the ball-mill machine is 300-600r/min, the ball-milling time is 3-8h. obtaining a 1 μm powder sample (2);
The powder obtained in step (2) was put into a graphite mold with a diameter of 15 mm, and was subjected to spark plasma sintering in vacuum, with a sintering temperature rising rate of 50-200°C/min and a temperature of 500°C-800°C. C. and 20 MPa-60 MPa for 5-15 min to obtain a pure phase n-type Mg ₃ Sb ₂ based thermoelectric material (3).

Preferably, the raw materials in step (1) are weighed in a glove box filled with high purity argon with a purity of 99.999%.

Preferably, step (2) is ball milling under the protection of high-purity argon, the ball material ratio is 15:1, the rotation speed of the ball mill is 550 r/min, the ball milling time is 5h, and the ball mill is The method is to stop for 5 minutes after every 30 minutes of forward rotation, and then to stop for 5 minutes after every 30 minutes of reverse rotation.

Preferably, in step (3), the heating rate is 50° C./min, and the temperature is maintained at 650° C. and 50 MPa for 10 minutes.

Beneficial effects of the present invention are:
1) The n-type _{Mg3Sb2 -} based thermoelectric material produced by the present invention has the characteristics of low raw material cost compared with the current commercially available _{Bi2Te3 -} based material, and can be manufactured by a one-step ball milling process. allows the n-type _{Mg3Sb2 -} based thermoelectric materials to be produced quickly, efficiently, energy-savingly, and at low cost, and is easy to operate in the production process, energy-saving, environmentally friendly, and phase-pure. N-type Mg ₃ Sb ₂ based thermoelectric materials can be produced on a large scale.
2) The n-type _{Mg3Sb2 -} based thermoelectric material produced by the present invention has the advantages of high purity, high crystallinity, high reproducibility, excellent thermal stability and mechanical strength, and the highest power factor is 2451.70 μWm ⁻¹ K ⁻² , which is the highest value of the present system, and at 723 K, the highest ZT is 1.8, one of the highest values of the present system.
₃ ) The n-type Mg3Sb2 _- based thermoelectric material produced in the present invention adopts spark plasma sintering, successfully synthesizing a pure-phase _{Mg3Sb2 -} based thermoelectric material rapidly, which is superior to conventional high-temperature Avoid the drawbacks of melting and two-stage high-energy ball milling, such as Mg element volatilization, complicated sealing conditions, high impurity content, and high price of high-energy ball milling.
4) The n-type Mg ₃ Sb ₂ based thermoelectric material produced in the present invention introduces a microstructure (nanocrystalline grains and nanolamellar structures) with a minimum thermal conductivity of 0.90 Wm ⁻¹ K ⁻¹ at 723K. It has a rate value and is currently the lowest value in the system.

It is an XRD diagram obtained by physical phase analysis of the sample of the example using an X-ray diffraction device, (a) is Example 1 of the present invention, and (b) is Example 2 of the present invention. (c) is Example 3 of the present invention, (d) is Example 4 of the present invention, (e) is Example 5 of the present invention, and (f) is Example of the present invention is 6. As can be seen, the manufacturing method of the present invention can obtain Mg ₃ Sb ₂ base material with high purity and high crystallinity. FIG. 10 is a comparison diagram showing power factors in Example 1, Example 2, and Example 3 that change according to temperature; FIG. 3 is a comparison diagram showing changes in thermal conductivity according to temperature in Examples 1, 2, and 3; FIG. 3 is a comparison diagram showing the thermoelectric figure of merit ZT in Example 1, Example 2, and Example 3 that changes according to temperature. FIG. 10 is a comparison diagram showing power factors in Example 4, Example 5, and Example 6 that change according to temperature; FIG. 10 is a comparison diagram showing changes in thermal conductivity according to temperature in Examples 4, 5, and 6; FIG. 8 is a comparison diagram showing the thermoelectric figure of merit ZT in Examples 4, 5, and 6 that changes according to temperature. FIG. 11 is a comparison diagram showing power factors in Example 7, Example 8, and Example 9 that change according to temperature; FIG. 10 is a comparison diagram showing changes in thermal conductivity according to temperature in Examples 7, 8, and 9; FIG. 10 is a comparison diagram showing the thermoelectric figure of merit ZT in Examples 7, 8, and 9 that changes according to temperature. FIG. 11 is a comparison diagram showing power factors in Example 10 and Example 11 that change according to temperature. FIG. 11 is a comparison diagram showing changes in thermal conductivity according to temperature in Examples 10 and 11; FIG. 11 is a comparison diagram showing the thermoelectric figure of merit ZT in Examples 10 and 11 that changes according to temperature. 4 is a scanning electron micrograph of a sample in Example 5. FIG. 4 is a transmission electron micrograph of a sample in Example 5. FIG.

The following is a further description of the invention without limiting the invention.

Example 1:
(1) Raw material magnesium powder, antimony powder, bismuth powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition is Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y Weigh sequentially with a stoichiometric ratio of (x=0, y=0.01) and put into a stainless steel ball mill pot with a ball material ratio of 15:1.

(2) The ball mill pot is installed in a planetary ball mill, ball milled for 1 h under the protection of argon to obtain a powder with a particle size of 500 nm to 1 μm, the rotation speed of the ball mill machine is 300 r/min, and the ball mill method is: It is to stop for 5 minutes every time it rotates forward for 30 minutes, and then stop for 5 minutes every time it rotates reversely for 30 minutes.

(3) Put the powder obtained in step (2) into a graphite mold with a diameter of 15 mm, set the discharge plasma sintering temperature to 550 ° C., the heating rate to 100 ° C./min, the pressure to 20 Mpa, and keep warm for 5 min. do.
The highest power factor of the sample produced in this example is 1463.25 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 1.03 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=0.99. .

Example 2:
Referring to Example 1, in step (2), the rotation speed of the ball mill machine is 600 r/min, and in step (3), the discharge plasma sintering temperature is 750 ° C. and the heating rate is 150 ° C./min. , the pressure is set to 40 Mpa and kept warm for 5 min.

The highest power factor of the sample produced in this example is 1478.14 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 1.01 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=0.98. .

Example 3:
Referring to Example 1, in step (2), the rotation speed of the ball mill machine is 550 r/min, and in step (3), the spark plasma sintering temperature is 650 ° C. and the heating rate is 50 ° C./min. , the pressure is set to 50Mpa and the temperature is maintained for 10min.

The highest power factor of the sample produced in this example is 1843.20 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 0.99 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=1.25. .

Example 4:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0.01, y = 0.01) were weighed sequentially with a chemical weighing ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. It differs in that there is

The sample produced in this example has a highest power factor of 2093.97 μW m ⁻¹ K ⁻² , a lowest conductivity of 1.05 W m ⁻¹ K ⁻¹ , and a thermoelectric figure of merit ZT=1.36.

Example 5:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0.02, y = 0.01) were weighed sequentially with a chemical weighing ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. It differs in that there is

The highest power factor of the sample produced in this example is 2451.70 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 0.90 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=1.80. .

Example 6:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0.03, y = 0.01) were weighed sequentially with a chemical weighing ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. It differs in that there is

The highest power factor of the sample produced in this example is 1989.42 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 0.93 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=1.50. .

Example 7:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0, y = 0.02) were weighed sequentially with a chemical weighing ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. different in that respect.

The sample produced in this example has a highest power factor of 1680.12 μW m ⁻¹ K ⁻² , a lowest thermal conductivity of 1.01 W m ⁻¹ K ⁻¹ , and a thermoelectric figure of merit ZT=1.19.

Example 8:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0, y = 0.03) were weighed sequentially with a chemical weighing ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. different in that respect.

The highest power factor of the sample produced in this example is 1710.58 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 1.04 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=1.18. .

Example 9:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0, y = 0.04) were weighed sequentially with a stoichiometric ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. different in that respect.

The highest power factor of the sample produced in this example is 1581.16 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 1.08 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=1.05. .

Example 10:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0, y = 0.07) were weighed sequentially with a chemical weighing ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. different in that respect.

The highest power factor of the sample produced in this example is 1671.16 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 0.94 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=1.01. .

Example 11:
Referring to Example 3, in step (1), the raw material magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder are placed in a glove box filled with high-purity argon with a purity of 99.999%, and the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y (x = 0.07, y = 0.01) were weighed sequentially with a chemical weighing ratio, placed in a stainless steel ball mill pot, and the ball material ratio was 15:1. It differs in that there is

The highest power factor of the sample produced in this example is 2090.18 μW m ⁻¹ K ⁻² , the lowest thermal conductivity is 1.07 W m ⁻¹ K ⁻¹ , and the thermoelectric figure of merit ZT=1.46. .

Claims (6)

A method for producing an n-type Mg ₃ Sb ₂ based thermoelectric material, wherein the raw material composition is Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y , x=0-0.1, y = 0 to 0.1, x, y represent atomic percentages,
In an argon atmosphere , magnesium powder, antimony powder, bismuth powder, yttrium powder, and selenium powder were mixed in a stoichiometric ratio of the chemical composition Mg _3.2-x Y _x Sb _1.5 Bi _0.5-y Se _y . step (1) of weighing sequentially;
Under the protection of argon, the weighed powder is ball-milled, the rotation speed of the ball-mill machine is 300-600r/min, the ball-milling time is 3-8h, and the powder is uniformly mixed after ball-milling, and the diameter is 500nm-1μm. obtaining a powder sample (2);
The powder obtained in step (2) is placed in a graphite mold with a diameter of 15 mm, and is sintered in vacuum by spark plasma, with a sintering temperature rising rate of 50-200°C/min, and 500-800°C. , heat-retaining at 20 MPa-60 MPa for 5-15 min to obtain an n-type Mg ₃ Sb ₂ -based thermoelectric material (3);
A method for producing an n-type Mg ₃ Sb ₂ based thermoelectric material, characterized by: When x = 0.01-0.07, y = 0.01-0.07 ,
A method for producing an n-type Mg ₃ Sb ₂ based thermoelectric material according to claim 1 . x = 0.02, y = 0.01 ,
A method for producing an n-type Mg ₃ Sb ₂ based thermoelectric material according to claim 1 . The raw materials in step (1) are weighed in a glove box filled with argon with a purity of 99.999%,
The method for producing n-type _{Mg3Sb2 -} based thermoelectric material according to claim 1 , characterized in that: The step (2) is ball milling under the protection of argon, the ball material ratio is 15:1, the rotation speed of the ball milling machine is 550r/min, the ball milling time is 5h, and the ball milling mode is 30min. It is to stop for 5 minutes each time it rotates forward, and then for 5 minutes every time it rotates reversely for 30 minutes.
The method for producing n-type _{Mg3Sb2 -} based thermoelectric material according to claim 4 , characterized in that: In the step (3), the heating rate is 50 ° C./min, and the temperature is kept at 650 ° C. and 50 Mpa for 10 min.
The method for producing n-type _{Mg3Sb2 -} based thermoelectric material according to claim 4 , characterized in that:

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