JP2021515411A - n-type Mg-Sb-based room temperature thermoelectric material and its manufacturing method - Google Patents

Abstract

It is an n-type Mg-Sb group room temperature thermoelectric material, and the general chemical formula is Mg3 + δMnxSb2-y-zBiiAz, where A is an oxygen group element S, Se or Te, −0.2 ≦ δ ≦ 0.3. Yes, x, y, z are atomic ratios, x = 0.001 to 0.4, y = 0 to 1.0, z = 0 to 0.2. Using a single material having a purity of ≥99% according to the general chemical formula as a raw material, batch weighing each in an argon atmosphere, adding small balls made of stainless steel to the ball mill, and rotating the ball mill at high speed to obtain powder. The powders are weighed and packed in a graphite mold, and the mold is placed in a high-temperature furnace to create a vacuum, sintered at a total pressure of less than 4 Pa, and cooled to room temperature after the sintering is completed. The room temperature thermoelectric figure of merit and mechanical performance of thermoelectric materials are clearly superior to those of traditional n-type tellurized bismuth, and are cheaper, easier to manufacture, more controllable and more reproducible.

Description

The present invention belongs to the technical field of thermoelectric materials, and particularly relates to n-type Mg-Sb-based room temperature thermoelectric materials and methods for producing the same.

Thermoelectric materials are constantly attracting attention from all over the world as key materials for power generation technology that uses waste heat and solar energy as heat sources. A good thermoelectric material usually has good conductivity and poor heat transfer performance. Thermoelectric materials are usually divided into n-type and p-type, and a thermoelectric device is formed by integrating multiple p-type and n-type thermoelectric materials to realize mutual conversion between direct electrical energy and thermal energy. To do. The energy conversion efficiency of thermoelectric devices mainly depends on the thermoelectric figure of merit (ZT) of the thermoelectric material. How to improve the performance of thermoelectric materials is a popular research direction in academia and industry, and researchers are not only controlling the transfer process of electrons and phonons in known thermoelectric materials, but also new types. We are also focusing on searching for thermoelectric materials. In particular, research on n-type traditional thermoelectric materials has improved performance to some extent by optimizing means such as nanonization and phonon processes. The tellurized bismuth-based thermoelectric material is a thermoelectric material (150 ° C, ZT _m ≈ 1.06) with the best performance near room temperature, while the medium-temperature thermoelectric material is Skutterudes (450 ° C, ZT _m ≈ 1.08). Thermoelectric performance indices such as lead telluride (500 ° C, ZT _m ≈ 1.4) and Half-Heuslers (600 ° C, ZT _m ≈ 1.0) peak only in the range of 400 to 600 ° C and are near room temperature. ZT is also less than 0.4. With the miniaturization of thermoelectric devices, we have submitted certain requirements for the processability and mechanical performance of materials. Currently commercial room temperature n-type thermoelectric materials are tellurized bismuth substrates, but their poor mechanical performance limits the variety of thermoelectric devices and their fracture toughness is between ^{0.8 and 1.3 MPam 1/2.} is there.

Currently, many scholars have studied the above problems and adopted, for example, Mg-Sb-based Zintl compounds as a new thermoelectric material, but the thermoelectric figure of merit and mechanical performance are not very ideal at room temperature. The operating temperature range and application area of the material were limited.

Therefore, it is necessary to solve these technical defects.

An object of the present invention is to overcome the above-mentioned deficiency of the prior art. First, an n-type Mg-Sb-based thermoelectric material having excellent room temperature thermoelectric performance is provided, and its room temperature thermoelectric performance index and mechanical performance are traditional. It is superior to the level of n-type tellurized bismuth thermoelectric materials and is cheaper.

Chemical formulas of the n- type Mg-Sb based room temperature thermoelectric material provided by the present invention is a _{Mg 3 + δ Mn x Sb 2} -yz Bi y A z, wherein A is an oxygen group element S, Se or Te , -0.2 ≤ δ ≤ 0.3, and x, y, and z are atomic ratios, x = 0.001 to 0.4, y = 0 to 1.99.0, z = 0 to 0. It is 2.

In n- type Mg-Sb based room temperature thermoelectric materials as preferred chemical formula _{Mg 3 + δ Mn x Sb 2} -yz Bi y A z of the present invention, x = 0.001~0.4, y = 0~1 . 0, z = 0 to 0.2.

The above-mentioned room temperature n-type Mg-Sb-based thermoelectric material provided by the present invention has a room temperature thermoelectric performance index superior to that of the prior art n-type tellurized bismuth performance (0.8-1.06). The materials are selected and mixed with inexpensive and easily available oxygen group elements, and these elements are relatively large in storage in nature, are inexpensive, and are used as commercial n-type room temperature thermoelectric materials for existing tellurized bismuth. It can be replaced, meets the demand for mass production of industrialization, and has high utility value.

The present invention also provides a method for producing the above-mentioned n-type Mg-Sb-based room temperature thermoelectric material.

The general formula _{Mg 3 + δ Mn x Sb 2} -yz Bi y A purity ≧ 99% of a single material according to _z as the raw material, the oxygen content is batch weighed in an argon atmosphere of less than 1 ppm, and was set in a ball mill, a ball mill A certain amount of stainless steel globules are added, and the ball mill is rotated at high speed to obtain powder.

The powders obtained in the above steps are weighed and packed in a graphite mold, the mold is placed in a high temperature furnace to create a vacuum, sintered at a total pressure of less than 4 Pa, and cooled to room temperature after sintering. A mass thermoelectric material having a density of 3.6 to 5.8 g / cm ^{3 can be obtained.}

As an optional step of the manufacturing method of the present invention, when the stainless steel globules and the raw material rotate in the ball mill, argon gas is injected to protect them.

As an optional step of the manufacturing method of the present invention, at least two kinds of stainless steel globules having different diameters are used as the stainless steel globules contained in the ball mill.

When two types of stainless steel globules are used as an optional step of the manufacturing method of the present invention, the diameters are 6 mm and 20 mm, respectively, and the quantity ratio thereof is 10: 1 to 5: 3.

As an optional step of the manufacturing method of the present invention, the weight of the stainless steel globules and raw materials placed on the ball mill is 10: 1 to 20: 1.

As an optional step of the manufacturing method of the present invention, the ball polishing time in the ball mill of the stainless steel globules and the raw material is 7 to 12 hours.

As an optional step of the manufacturing method of the present invention, the operating speed of the ball mill is 300 to 500 r / min.

As an optional step of the manufacturing method of the present invention, when the mold is placed in a high temperature furnace for sintering, the sintering temperature is 500 ° C. to 900 ° C. and the sintering time is 5 min to 40 min.

As an optional step of the manufacturing method of the present invention, when the mold is placed in a high temperature furnace for sintering, the sintering temperature is 600 ° C. to 900 ° C. and the sintering time is 5 min to 40 min.

As an optional step of the manufacturing method of the present invention, when the mold is placed in a high temperature furnace and sintered, the sintering axial pressure is 40 to 120 MPa.

The method for producing an n-type Mg-Sb-based room temperature thermoelectric material provided by the present invention mechanically impacts a raw material with small balls made of stainless steel having different diameters to form an alloyed powder. In addition, discharge plasma activated sintering molding is performed using a graphite mold, the operation is simple, the craft process is short, the cost is low, the controllability of the obtained thermoelectric material is strong, the reproducibility is good, and the thermoelectric material There is a good future in the field.

In order to more clearly explain the technical solutions in the examples of the present invention, the drawings used in the examples will be briefly described below. Obviously, the drawings described below are only a few embodiments of the present invention, and one of ordinary skill in the art can obtain other drawings from these drawings without any creative effort. ..

FIG. 1 is a schematic view of a graphite mold used in the production of plasma sintering of the present invention. Figure 2 is a XRD spectrum of Example 1 of producing the n- type _{Mg 3 + δ Mn x Sb 2} -yz Bi y Te z room temperature thermoelectric material according to the present invention. Figure 3 is a thermoelectric performance view in the cycle test of Example 1 of producing the n- type _{Mg 3 + δ Mn x Sb 2} -yz Bi y Te z room temperature thermoelectric material according to the present invention. Figure 4 is a thermoelectric figure of merit comparison diagram of manufacturing the n- type _{Mg 3 + δ Mn x Sb 2} -yz Bi y Te z room temperature thermoelectric material in Example 1 and the conventional n- type bismuth telluride material by the present invention is there. Figure 5 is a cutaway toughness comparison diagram of manufacturing the n- type _{Mg 3 + δ Mn x Sb 2} -yz Bi y Te z room temperature thermoelectric material in Example 1 and the conventional n- type thermoelectric material according to the present invention. 6 is an XRD spectrum of Example 3 of the manufactured n- type _{Mg 3 + δ Mn x Sb 2} -yz Bi y Se z room temperature thermoelectric material according to the present invention.

In order to clarify the object, technical solution, and advantage of the present invention, the present invention will be described in more detail with reference to the following drawings and examples. It should be understood that the specific examples described herein are descriptions of the present invention and are not intended to limit the present invention.

The present invention has the chemical formula has provided _{Mg 3 + δ Mn x Sb 2} -yz Bi y is A _z n-type Mg-Sb based room temperature thermoelectric materials. Here, A is an oxygen group element S, Se or Te, −0.2 ≦ δ ≦ 0.3, and x, y, z are atomic ratios, x = 0.001 to 0.4, y = 0. ~ 1.99, z = 0 to 0.2.

As aforementioned n- type Mg-Sb based room temperature thermoelectric material, 0.001 to 0.4 is preferred as the range of x values in the chemical formula _{Mg 3 + δ Mn x Sb 2} -yz Bi y A z. The range of y value is preferably 0 to 1.0. The range of the z value is preferably 0 to 0.2.

Currently, the Mg-Sb-based thermoelectric material has excellent thermoelectric performance as a new type of thermoelectric material, but its application at medium and low temperatures is affected by the Mg vacancy, and the ZT value near room temperature is less than 0.4. It limits the operating temperature range and application fields of this new material. Mg ₃ Sb ₂ is a Zintl phase layered material with an a-La ₂ O ₃ structure, which usually has a large solid solubility, provides a large space for doping elements, is advantageous for adjusting the Mg emptyness concentration, and is a material. The Sb-position doped Bi is advantageous in lowering the thermal conductivity. However, doping of different elements also _{affects the Mg 3} Sb ₂ energy band differently in terms of electronic structure, which changes the temperature at which the thermoelectric figure of merit peaks, making it impossible to achieve ideal thermoelectric performance. Limit the operating temperature range and application area of. In the present invention, _{the Zintl phase layer of Mg 3} Sb ₂ is doped with a trace amount of oxygen group elements such as S, Se or Te to control the carrier concentration, lower the lattice thermal conductivity, and the thermoelectric performance of the Mg-Sb-based thermoelectric material. Can be improved. In particular, the thermoelectric figure of merit under room temperature conditions reaches the performance level of n-type tellurized bismuth (0.8-1.06) of the prior art, and exceeds the performance level of n-type tellurized bismuth at medium and high temperatures. In addition, since we chose cheap and easily available oxygen group elements as the doping material, these elements are relatively large in storage in nature, cheap in price, much lower in cost than tellurized bismuth thermoelectric materials, and can be mass-produced for industrialization. Since it is possible, it is sufficiently useful as a commercial n-type room temperature thermoelectric material to replace the existing tellurized bismuth.

The present invention further provides a method for producing the above-mentioned n-type Mg-Sb-based room temperature thermoelectric material, which comprises the following steps.

S1 is the chemical formula _{Mg 3 + δ Mn x Sb 2} -yz Bi y A purity ≧ 99% of a single material according to _z is selected as the raw material, the oxygen content is batch weighed in an argon atmosphere of less than 1ppm, respectively, Then, it is set in a planetary ball mill, a certain amount of stainless steel globules are added to the ball mill, and the above-mentioned raw materials are crushed and mixed by utilizing the collision energy of the stainless steel globules in the ball mill, and powder Mg _{3 + δ} Mn is used. was rudimentary synthesized _{x Sb 2-yz Bi y a} z phase.

In this step, when the stainless steel globules in the ball mill and the raw material rotate in the ball mill, argon gas can be injected to protect them and prevent the powder from being oxidized.

In order to further change the size of the crystal grains, at least two kinds of globules of different diameters were selected as the joined stainless steel globules, and the globules of different diameters constantly collided with each other to obtain the powder material. The particle size can be further reduced and the mixing can be made more uniform. Two types of stainless steel globules having diameters of 6 mm and 20 mm are selected, and the quantity ratio of the two types of globules is 10: 1 to 5: 3.

In this step, the weight ratio of the stainless steel globules set in the ball mill to the raw material is 10: 1 to 20: 1, and the operating speed of the ball mill is 300 to 500 r / min. The ball polishing time with the raw material in the ball mill was 7 to 12 hours, and an ideal powder was obtained.

In S2, the powders obtained in the above steps are weighed and packed in a graphite mold, and the mold is placed in a high temperature furnace to create a vacuum, which is sintered when the total pressure is less than 4 Pa to form a massive alloy. After the sintering is completed, cool to room temperature.

Referring to FIG. 1, in this step, the graphite mold includes a graphite pressure head 1, a graphite pressure chamber 2 and a thermocouple 3, and the powder 4 is arranged in the graphite pressure chamber 2 and agglomerated by the graphite pressure head 1. It is compressed. When a graphite mold is sintered in a high temperature furnace, the sintering temperature is 500 ° C. to 900 ° C., preferably 600 ° C. to 900 ° C., the sintering time is 5 min to 40 min, and the sintering axial pressure is 40 to 40. It is 120 MPa.

The density of the mass produced in the above step is ^{between 3.6 and 5.8 g / cm 3} , the resistivity is 5 to 180 μΩm, the Seebeck coefficient is 80 to 340 μV / K, and the power factor is 0.6 to 4. 0.0 mW / m / K ² , thermal conductance 0.45 to 1.25 Wm ^-1 K ^-1 , breaking toughness ^{greater than 2.1 MPam 1/2} , its thermoelectric performance index ZT is 0.6 to 0 at room temperature. It reaches 9 and 1.42 at 250 ° C, which is clearly superior to the tellurized bismuth thermoelectric material.

Measured within the range of 2θ = 10 ° to 80 ° using an X-ray diffractometer (XRD), the 5-element Mg-Sb-based thermoelectric material Mg _{3 + δ} Mn _x Sb _2- it _yz Bi _y a _z has a corresponding diffraction peaks of Mg ₃ Sb _2-phase, and no appearance of other extraneous peaks (Hetero peak), synthetic material is a Mg ₃ Sb ₂ single phase Was suggested.

The method for producing an n-type Mg-Sb-based room temperature thermoelectric material provided by the present invention is a powder in which raw materials are alloyed by mechanically impacting in a ball mill using small balls made of stainless steel having different diameters. It is formed in a stainless steel mold and placed in a graphite mold for discharge plasma activation sintering molding. The manufacturing method is simple to operate, low in cost, strong in controllability, good reproducibility, and industrial production. It is advantageous to.

Hereinafter, the production method of the present invention will be described in detail together with examples.

Example 1
Manufactured by the following process.
In S1, sheet Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Te (purity 99.999%), powder Mn (purity 99.95). %) and pick raw materials, the general formula _{Mg 3 + δ Mn x Sb 2} -yz Bi y Te z in which the stoichiometric ratio (where δ = -0.1, x = 0.1, y = 0 According to .5, z = 0.01, that is, the general formula of chemistry is Mg _2.9 Mn _0.1 Sb _1.49 Bi _0.5 Te _0.01 ), the oxygen content is batch-weighed in an argon atmosphere vacuum dry box with an oxygen content of less than 1 ppm. Small balls made of stainless steel with diameters of 6 mm and 20 mm are placed in a planetary ball mill at a ratio of 10: 1, and argon gas is injected to protect them to prevent powder oxidation. The weight ratio of the ball mill to the raw material is 20: It was 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 7.5 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, high temperature sintering is performed at a total pressure of less than 4 Pa, the sintering temperature is controlled within 600 ° C, the overburn temperature is controlled within 10 ° C, and the applied pressure during the sintering process is 75 MPa. The sintering time was controlled to about 10 min.

After the completion of sintering, the density of the formed mass was about 4.0 g / cm ³ .

As shown in FIG. 2, the mass materials obtained in Example 1 through the analysis of X-ray diffraction are all Mg ₃ Sb ₂ single-phase, and the quintuple Mg-Sb-based thermoelectric material Mg _2.9. Mn _0.1 Sb _1.49 Bi _0.5 Te _{0.01 has Mg 3} Sb ₂ at 22.46 °, 24.61 °, 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc., respectively. Diffraction peaks of (100), (002), (011), (012), and (103) appeared.

Referring to FIG. 3, the n-type Mg _2.9 Mn _0.1 Sb _1.49 Bi _0.5 Te _0.01 material produced in Example 1 has a thermal power ratio of 1.5 to 1.5 in a cycle test in the range of 0 ° C. to 500 ° C. It is 2.7 mW / m / K ² .

Referring to FIG. 4, the _{thermoelectric performance index ZT of the n-type Mg 2.9} Mn _0.1 Sb _1.49 Bi _0.5 Te _0.01 material produced in Example 1 reaches 0.69 at room temperature and 1.42 at 250 ° C. Responded to tellurized bismuth between 25 ° C and 125 ° C, and after 125 ° C the ZT value was clearly superior to the tellurized bismuth material.

As shown in FIG. 5, the mechanical performance of the 5-element n-type Mg _2.9 Mn _0.1 Sb _1.49 Bi _0.5 Te _0.01 material produced in Example 1 is that the fracture toughness is 2.95 MPam ^1/2 and the Young's modulus is At 43 GPa, the elastic modulus corresponds to the tellurized bismuth base material, and the fracture toughness is 2.5 to 3 times that of the tellurized bismuth base material.

In addition, this 5-element n-type Mg _2.9 Mn _0.1 Sb _1.49 Bi _0.5 Te _0.01 mass material has a resistivity of 20 to 90 μΩm, a Seebeck coefficient of -220 to -300 μV / K, and heat within a range of 25 to 500 ° C. The conductance is 1.1 to 0.6 Wm ^-1 K ^-1 .

Example 2:
Manufactured by the following process.
In S1, sheet Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Te (purity 99.999%), powder Mn (purity 99.95). %) as a raw _{material, Mg 3 + δ Mn x Sb} 2-yz Bi y Te z in which the stoichiometric ratio (δ = 0.1, x = 0.2 , y = 0.3, z = 0.05 That is, according to the general formula Mg _3.1 Mn _0.2 Sb _1.65 Bi _0.3 Te _0.05 ), the oxygen content was batch-weighed in a vacuum drying box with an argon atmosphere of less than 1 ppm, and small balls made of stainless steel with diameters of 6 mm and 20 mm were used. They were placed together in a planetary ball mill at a ratio of 10: 2 and argon gas was injected to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 15: 1. The operating speed of the planetary ball mill was 400 r / min, and the ball polishing time was 10 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 4 Pa, the sintering temperature is controlled within 700 ° C., the overburn temperature is controlled within 10 ° C., and the applied pressure during the sintering process is 80 MPa. The firing time was controlled to 20 min. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

After the completion of sintering, the density of the formed mass was approximately 4.2 g / cm ³ .

After analysis of X-ray diffraction, the _{quintuple n-type Mg 3.1} Mn _0.2 Sb _1.65 Bi _0.3 Te _0.05 mass material _{produced in Example 2 is Mg 3} Sb ₂ single phase and 22.46 ° each. , 24.61 °, 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc. of Mg ₃ Sb ₂ (100), (002), (011), (012), respectively. , (103) Diffraction peaks appeared, and no other heterogeneous peaks appeared.

In addition, this 5-element n-type Mg _3.1 Mn _0.2 Sb _1.65 Bi _0.3 Te _0.05 mass material has a resistivity of 10 to 80 μΩm, a Seebeck coefficient of −150 to −350 μV / K, and heat within a range of 25 to 500 ° C. The conductance is 1.2 to 0.7 Wm ^-1 K ^-1 .

Mechanical performance Fracture toughness is 2.56 MPam ^1/2 and Young's modulus is 45 GPa.

The thermoelectric figure of merit ZT reaches 0.74 at room temperature and 1.42 at 250 ° C, clearly superior to the tellurized bismuth material.

Example 3
Manufactured by the following process.
In S1, sheet Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Se (purity 99.999%), powder Mn (purity 99.95). the%) as a raw _{material, Mg 3 + δ Mn x Sb} 2-yz Bi y Se z in a stoichiometric ratio (δ = 0, x = 0.3 , y = 0.1, z = 0.1, i.e. According to the general formula Mg ₃ Mn _0.3 Sb _1.8 Bi _0.1 Se _0.1 ), the oxygen content is batch-weighed in a vacuum drying box with an argon atmosphere of less than 1 ppm, and small balls made of stainless steel with diameters of 6 mm and 20 mm are 5 :. They were placed together in a planetary ball mill at a ratio of 3 and injected with argon gas to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 10: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 7.5 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 4 Pa, the sintering temperature is controlled within 800 ° C., the overburn temperature is controlled within 10 ° C., the applied pressure during the sintering process is 100 MPa, and baking is performed. The firing time was controlled to 8 min. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

After the completion of sintering, the density of the formed mass was about 4.5 g / cm ³ .

_{As shown in FIG. 6, the quintuple n-type Mg 3} Mn _0.3 Sb _1.8 Bi _0.1 Se _0.1 mass material produced in Example 3 through the analysis of X-ray diffraction _{is Mg 3} Sb ₂ single phase. And, in the vicinity of 22.46 °, 24.61 °, 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc. of Mg ₃ Sb ₂ , (100), (002), respectively. (011), (012), and (103) diffraction peaks appeared, and no other heterogeneous peaks appeared.

Further, this 5-element n-type Mg ₃ Mn _0.3 Sb _1.8 Bi _0.1 Se _0.1 agglomerate material has a resistivity of 30 to 120 μΩm, a Seebeck coefficient of −240 to −350 μV / K, and heat within a range of 25 to 500 ° C. The conductance was 1.0 to 0.6 Wm ^-1 K ^-1 .

Mechanical performance Fracture toughness is 2.37 MPam ^1/2 and Young's modulus is 44 GPa.

The thermoelectric figure of merit ZT reaches 0.65 at room temperature and 1.38 at 250 ° C, clearly superior to the tellurized bismuth material.

Example 4
In S1, sheet Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), powder Mn (purity 99.95%), S (purity 99.999%). %) as a raw _{material, Mg 3 + δ Mn x Sb} 2-yz Bi y S z is a stoichiometric ratio (δ = -0.2, x = 0.4 , y = 0.8, z = 0. 2. That is, according to the general formula Mg _2.8 Mn _0.4 Sb ₁ Bi _0.8 S _0.2 ), the oxygen content is batch-weighed in a vacuum drying box in an argon atmosphere with an oxygen content of less than 1 ppm, and small balls made of stainless steel having diameters of 6 mm and 20 mm. Was put together in a planetary ball mill at a ratio of 10: 2 and argon gas was injected to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 20: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 12 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 4 Pa, the sintering temperature is controlled to 900 ° C., the overburn temperature during the sintering process is controlled within 10 ° C., the applied pressure is 120 MPa, and baking is performed. The firing time was controlled to 5 min. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

After the completion of sintering, the density of the formed mass was about 4.8 g / cm ³ .

After analysis of X-ray diffraction, the quintuple n-type Mg _2.8 Mn _0.4 Sb ₁ Bi _0.8 S _0.2 massive material _{produced in Example 4 is Mg 3} Sb ₂ single phase and 22.46 °, respectively. _{Mg 3} Sb ₂ (100), (002), (011), (012), respectively, in the vicinity of 24.61 °, 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc. (103) Diffraction peaks appeared, and no other heterogeneous peaks appeared.

In addition, this 5-element n-type Mg _2.8 Mn _0.4 Sb ₁ Bi _0.8 S _0.2 mass material has a resistivity of 20 to 130 μΩm, a Seebeck coefficient of -175 to 280 μV / K, and heat within a range of 25 to 500 ° C. The conductance was 0.9 to 0.6 Wm ^-1 K ^-1 .

Mechanical performance Fracture toughness is 2.55 MPam ^1/2 and Young's modulus is 49.5 GPa.

The thermoelectric figure of merit ZT reaches 0.62 at room temperature and 1.29 at 250 ° C, clearly superior to the tellurized bismuth material.

Example 5
In S1, sheet-like Mg (purity 99.8%), granular Sb (purity 99.999%), powdery Mn (purity 99.95%), and S (purity 99.999%) are used as raw materials, and Mg _{3+ δ Mn x Sb 2-yz Bi} y S z is a stoichiometric ratio (δ = 0.2, x = 0.1 , y = 0, z = 0, i.e. the chemical formula Mg _3.2 Mn _0.1 Sb ₂₎ in accordance with , Oxygen content is batch weighed in a vacuum dry box with an argon atmosphere of less than 1 ppm, and 6 mm and 20 mm diameter stainless steel globules are put together in a planetary ball mill in a ratio of 10: 1 and argon gas. Was injected to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 15: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 12 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 4 Pa, the sintering temperature is controlled within 700 ° C, the overburn temperature during the sintering process is controlled within 10 ° C, the applied pressure is 120 MPa, and baking is performed. The firing time was controlled to 30 min. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

After the completion of sintering, the density of the formed mass was approximately 4.2 g / cm ³ .

After analysis of X-ray diffraction, the _{quintuple n-type Mg 3.2} Mn _0.1 Sb ₂ mass material _{produced in Example 5 is Mg 3} Sb ₂ single phase and 22.46 ° and 24.61, respectively. (100), (002), (011), (012), (103) of _{Mg 3} Sb _{2 in} the vicinity of °, 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc., respectively. Diffraction peaks appeared and no other heterogeneous peaks appeared.

This 5-element n-type Mg _3.2 Mn _0.1 Sb ₂ mass material has a resistivity of 30 to 100 μΩm, a Seebeck coefficient of −180 to −250 μV / K, and a thermal conductance of 1.3 to −500 ° C. in the range of 25-500 ° C. It was 0.8 Wm ^-1 K ^-1.

Mechanical performance Fracture toughness is 2.15 MPam ^1/2 and Young's modulus is 45.5 GPa.

The thermoelectric figure of merit ZT reaches 0.41 at room temperature and 0.96 at 250 ° C, close to the level of tellurized bismuth material.

Example 6
In S1, filamentous Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Te (purity 99.999%), powdery Mn (purity 99.95%). ) as a raw _{material, Mg 3 + δ Mn x Sb} 2-yz Bi y Te z in which the stoichiometric ratio (δ = 0.2, x = 0.01 , y = 1.8, z = 0.01, That is, according to the general chemical formula Mg _3.2 Mn _0.01 Sb _0.19 Bi _1.8 Te _0.01 ), the oxygen content was batch-measured in a vacuum drying box with an argon atmosphere of less than 1 ppm, and 10 small balls made of stainless steel with diameters of 6 mm and 20 mm were measured. It was placed in a ball mill at a ratio of 1: 1 and argon gas was injected to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 15: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 10 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 4 Pa, and two-step sintering is performed. The primary sintering temperature is 500 ° C., the time is 20 min, and the secondary sintering temperature is 700 ° C., time. Was 10 min. During the sintering process, the overburn temperature was controlled within 10 ° C. and the applied pressure was 120 MPa. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

After the completion of sintering, the density of the formed mass is approximately 5.5 g / cm ³ .

After analysis of X-ray diffraction, the _{quintuple n-type Mg 3.2} Mn _0.01 Sb _0.2 Bi _1.8 mass material _{produced in Example 6 is Mg 3} Sb ₂ single phase and 22.46 ° and 24, respectively. (100), (002), (011), (012), (012) of _{Mg 3} Sb _{2 in} the vicinity of .61 °, 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc., respectively. 103) Diffraction peaks appeared, and no other heterogeneous peaks appeared.

This n-type Mg _3.2 Mn _0.1 Sb ₂ mass material has a resistivity of 5 to 20 μΩm, a Seebeck coefficient of −120 to −160 μV / K, and a thermal conductance of 1.8 to 2. It is 2 Wm ^-1 K ^-1 .

The thermoelectric figure of merit ZT reaches 0.41 at room temperature and 0.68 at 250 ° C., and its thermoelectric performance is lower than that of Examples 1 to 5.

Example 7
In S1, filamentous Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Te (purity 99.999%), powdery Mn (purity 99.95%). ) as a raw _{material, Mg 3 + δ Mn x Sb} 2-yz Bi y Te z in which the stoichiometric ratio (δ = 0.2, x = 0.01 , y = 1.2, z = 0.05, That is, according to the general chemical formula Mg _3.2 Mn _0.01 Sb _0.75 Bi _1.2 Te _0.05 ), the oxygen content was batch-measured in a vacuum drying box with an argon atmosphere of less than 1 ppm, and 10 small balls made of stainless steel with diameters of 6 mm and 20 mm were measured. It was placed in a ball mill at a ratio of 1: 1 and argon gas was injected to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 15: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 10 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 4 Pa, the sintering temperature is controlled within 700 ° C, the overburn temperature during the sintering process is controlled within 10 ° C, the applied pressure is 120 MPa, and baking is performed. The firing time was controlled to 30 min. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

After the completion of sintering, the density of the formed mass was about 5.0 g / cm ³ .

After analysis of X-ray diffraction, the n-type Mg _3.2 Mn _0.1 Sb ₂ mass material _{produced in Example 7 is Mg 3} Sb ₂ single-phase, and 22.46 ° and 24.61 °, respectively. (100), (002), (011), (012), (103) diffraction peaks of _{Mg 3} Sb _{2 in} the vicinity of 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc., respectively. Appeared, and no other heterogeneous peaks appeared.

This n-type Mg _3.2 Mn _0.1 Sb ₂ mass material has a resistance of 10 to 40 μΩm, a Seebeck coefficient of −140 to −220 μV / K, and a thermal conductance of 1.4 to 1. It is 0 Wm ^-1 K ^-1 .

The thermoelectric figure of merit ZT reaches 0.60 at room temperature and 1.43 at 250 ° C, close to the level of tellurized bismuth material.

Example 8
In S1, filamentous Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Te (purity 99.999%), powdery Mn (purity 99.95%). ) as a raw _{material, Mg 3 + δ Mn x Sb} 2-yz Bi y Te z in which the stoichiometric ratio (δ = -0.2, x = 0.001 , y = 1.9, z = 0, i.e. According to the general formula Mg _2.8 Mn _0.001 Sb _0.1 Bi _1.9 ), the oxygen content was batch-weighed in a vacuum-drying box with an argon atmosphere of less than 1 ppm, and 10: 1 stainless steel balls with diameters of 6 mm and 20 mm. It was placed in a ball mill in an amount ratio and argon gas was injected to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 15: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 10 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and placed on the inner wall of the mold. Was laid with 0.1 mm graphite carbon paper, and then the mold was placed in the high temperature furnace cavity.

The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 4 Pa, and two-step sintering is performed. The primary sintering temperature is 500 ° C., the time is 20 min, and the secondary sintering temperature is 700 ° C., time. Was 20 min. During the sintering process, the overburn temperature was controlled within 10 ° C. and the applied pressure was 120 MPa. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

After the completion of sintering, the density of the formed mass was about 5.8 g / cm ³ .

After analysis of X-ray diffraction, the n-type Mg _2.8 Mn _0.001 Sb _0.1 Bi _1.9 mass material _{produced in Example 8 is Mg 3} Sb ₂ single-phase, and 22.46 ° and 24.61, respectively. (100), (002), (011), (012), (103) of _{Mg 3} Sb _{2 in} the vicinity of °, 25.65 °, 33.56 °, 37.29 °, 43.96 °, etc., respectively. Diffraction peaks appeared and no other heterogeneous peaks appeared.

This n-type Mg _2.8 Mn _0.001 Sb _0.1 Bi _1.9 mass material has a resistivity of 5 to 13 μΩm, a Seebeck coefficient of -70 to -110 μV / K, and a thermal conductance of 2.1 to ~ in the range of 25-500 ° C. It is 2.9 Wm ^-1 K ^-1 .

The thermoelectric figure of merit ZT reaches 0.35 at room temperature and 0.6 at 250 ° C.

Comparative Example 2
Manufactured by the following process.
In S1, sheet Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Te (purity 99.999%), powder Ti (purity 99.99). %) as a raw material, the stoichiometric ratio is _{Mg 3 + δ Ti x Sb 2} -yz Bi y Te z (δ = -0.2~0.3, x = 0~0.4, y = 0~ According to 0.8, z = 0 to 0.2), the oxygen content was batch weighed in a vacuum drying box with an argon atmosphere of less than 1 ppm, and stainless steel balls 6 mm and 20 mm in diameter were 10: 1. Argon gas was injected into the ball mill at a ratio of the amount to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 20: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 7.5 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 0.1 ppm in an argon atmosphere, weighed, placed in the graphite mold shown in FIG. 1, and then the mold is placed. It was placed in a quartz tube. The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 10 Pa, the applied pressure during the sintering process is 80 MPa, the heating speed is controlled to 5 to 35 ° C., and the sintering time is 30 to 30 to 35 ° C. It was controlled to 60 min. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

Through the analysis of X-ray diffraction, 5 yuan Mg obtained in Comparative Example _{1 3 + δ Ti x Sb 2} -yz Bi y Te z (y = 0~0.8, z = 0~0.4, z = 0-0.2) The mass material was Mg ₃ Sb ₂ single phase.

Referring to FIG. 6, a method in which Ti is selected as the doping element and thermoelectric sintering is adopted is adopted, and the thermoelectric performance index thereof is 0.38 at room temperature and 1.24 at 250 ° C. It is much lower than the thermoelectric performance index of Example 1.

Comparative Example 2
In S1, sheet Mg (purity 99.8%), granular Sb (purity 99.999%), Bi (purity 99.999%), Te (purity 99.999%), powder Fe (purity 99.99). %) as a raw material, the stoichiometric ratio is _{Mg 3 + δ Fe x Sb 2} -yz Bi y Te z (δ = -0.2~0.3, x = 0~0.4, y = 0~ According to 0.8, z = 0 to 0.2), the oxygen content was batch weighed in a vacuum drying box with an argon atmosphere of less than 1 ppm, and 10: 1 stainless steel globules with diameters of 6 mm and 20 mm. It was placed in a ball mill at a ratio of the amount and argon gas was injected to prevent powder oxidation, and the weight ratio of the ball mill to the raw material was 20: 1. The operating speed of the planetary ball mill was 500 r / min, and the ball polishing time was 7.5 hours.

In S2, the powder obtained in the above step is taken out from a vacuum drying box having an oxygen content of less than 1 ppm in an argon atmosphere, weighed, placed in a graphite mold shown in FIG. 1, and then the mold is placed in a quartz tube. I put it in. The inside of the furnace is evacuated, sintering is performed at a total pressure of less than 10 Pa, the rate of temperature rise is controlled to 5 to 35 ° C., the sintering time is controlled to 30 to 60 min, and the applied pressure during the sintering process. Was 80 MPa. After the sintering was completed, the material was cooled to room temperature and a sintered sample was taken out.

Through the analysis of X-ray diffraction, 5 yuan Mg obtained in Comparative Example _{2 3 + δ Fe x Sb 2} -yz Bi y Te z (y = 0~0.8, z = 0~0.4, z = 0-0.2) The mass material was Mg ₃ Sb ₂ single phase.

A transition element Fe is selected as the measured doping element, and a thermoelectric sintering method is adopted. The thermoelectric performance index is 0.23 at room temperature and 1.14 at 250 ° C. It is much lower than the thermoelectric performance index of Example 1.

The above-mentioned contents are merely preferable examples of the present invention, and do not limit the present invention. To the extent of the spirit and principles of the present invention, all modifications, equivalent substitutions, improvements, etc. should be included within the scope of protection of the present invention.

Claims (12)

Chemical formulas of the thermoelectric material is _{Mg 3 + δ Mn x Sb 2} -yz Bi y A z, A is an oxygen group element S, Se or Te, a -0.2 ≦ δ ≦ 0.3,
x, y, z are atomic ratios, and are n-type Mg-Sb groups at room temperature, characterized in that x = 0.001 to 0.4, y = 0 to 1.99, and z = 0 to 0.2. Thermoelectric material. In the chemical formula _{Mg 3 + δ Mn x Sb 2} -yz Bi y A z of the thermoelectric material, x = 0.001~0.4, y = 0~1.0 , is z = 0 to 0.2 The n-type Mg-Sb-based room temperature thermoelectric material according to claim 1. The general formula _{Mg 3 + δ Mn x Sb 2} -yz Bi y A purity ≧ 99% of a single material according to _z as the raw material, the oxygen content is batch weighed in an argon atmosphere of less than 1 ppm, and was set in a ball mill, a ball mill A process of adding a certain amount of small stainless steel balls and rotating the ball mill at high speed to obtain powder.
The powders obtained in the above steps are weighed and packed in a graphite mold, the mold is placed in a high temperature furnace to create a vacuum, sintered at a total pressure of less than 4 Pa, and cooled to room temperature after sintering. The method for producing an n-type Mg-Sb-based room temperature thermoelectric material according to claim 1 or 2, which comprises a step of obtaining a mass thermoelectric material having a density of 3.6 to 5.8 g / cm ^3. The method for producing an n-type Mg-Sb-based room temperature thermoelectric material according to claim 3, wherein when the stainless steel globules and the raw material rotate in a ball mill, argon gas is injected to protect them. .. The production of an n-type Mg-Sb-based room temperature thermoelectric material according to claim 4, wherein at least two kinds of stainless steel globules having different diameters are used as the stainless steel globules contained in the ball mill. Method. The n-type Mg- according to claim 5, wherein when two types of stainless steel globules are used, the diameters are 6 mm and 20 mm, respectively, and the quantity ratio is 10: 1 to 5: 3. A method for producing an Sb-based room temperature thermoelectric material. The n-type Mg-Sb according to any one of claims 3-6, wherein the weight ratio of the stainless steel globules set in the ball mill to the raw material is 10: 1 to 20: 1. A method for producing a base room temperature thermoelectric material. The n-type Mg-Sb group room temperature thermoelectric according to any one of claims 3-6, wherein the ball polishing time in the ball mill of the stainless steel globules and the raw material is 7 to 12 hours. How to make the material. The method for producing an n-type Mg-Sb-based room temperature thermoelectric material according to any one of claims 3-6, wherein the operating speed of the ball mill is 300 to 500 r / min. The invention according to any one of claims 3-6, wherein when the mold is placed in a high temperature furnace for sintering, the sintering temperature is 500 ° C. to 900 ° C. and the sintering time is 5 min to 40 min. A method for producing an n-type Mg-Sb-based room temperature thermoelectric material. The invention according to any one of claims 3-6, wherein when the mold is placed in a high temperature furnace for sintering, the sintering temperature is 600 ° C. to 900 ° C. and the sintering time is 5 min to 40 min. A method for producing an n-type Mg-Sb-based room temperature thermoelectric material. The n-type Mg-Sb group according to any one of claims 3-6, wherein when the mold is placed in a high temperature furnace and sintered, the sintering axial pressure is 40 to 120 MPa. A method for manufacturing a room temperature thermoelectric material.

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