N-type high-entropy semiconductor AgBiPbSe2S material and preparation thereof

Abstract

The application belongs to the field of novel high-entropy semiconductor materials, and discloses an N-type high-entropy semiconductor AgBiPbSe2S material and a preparation method thereof. The chemical formula of the N-type high-entropy semiconductor material is AgBiPbSe2S, wherein the atomic ratio of Ag, Bi, Pb, Se and S is 1:1:1:2:1. The material has a face-centered cubic structure, and the space group is Fm3m. The AgBiPbSe2S material obtained by improving the composition of the material can be used as an N-type semiconductor material and has the characteristics of high entropy. The material has a face-centered cubic lattice structure and belongs to the Fm3m space group, and can be used as an N-type thermoelectric material. In addition, based on the application, high-temperature smelting can be used to realize solid-phase reaction and obtain the target AgBiPbSe2S material, so that the preparation is convenient and large-scale preparation can be realized.

Description

Technical Field

[0001] This invention belongs to the field of novel high-entropy semiconductor materials, and more specifically, relates to an N-type high-entropy semiconductor AgBiPbSe2S material and its preparation, which is an N-type high-entropy semiconductor material. Background Technology

[0002] When N-type and P-type semiconductor thermoelectric materials are paired, they can form thermocouples, converting heat energy into electrical energy using the thermoelectric effect generated by temperature difference. High-performance and matched N-type and P-type semiconductors are fundamental to the high conversion efficiency and excellent service performance of thermoelectric devices. In recent decades, researchers have developed various P-type semiconductor materials with excellent thermoelectric properties (materials with positive Seebeck coefficients). However, N-type semiconductors are not only inferior in performance to P-type materials but also have fewer varieties. Developing new high-thermoelectric-performance N-type semiconductors is a key focus and breakthrough for further improving device conversion efficiency and accelerating their commercial application. In recent years, high-entropy semiconductor materials have attracted attention in the thermoelectric field due to their high crystal symmetry and severe lattice distortion. High-entropy semiconductors refer to solid solutions with high configurational entropy formed by five or more major elements competing for the same lattice sites in a molar ratio of 5-35%. High-entropy materials typically possess thermodynamic high-entropy effects, kinetic delayed diffusion effects, structural lattice distortion effects, and performance cocktail effects. The presence of high entropy effects favors the formation of highly symmetrical body-centered cubic (bcc) or face-centered cubic (fcc) crystal structures. Delayed diffusion effects facilitate the in-situ formation of nanoprecipitates, effectively reducing phonon scattering and significantly lowering the material's lattice thermal conductivity. Lattice distortion effects increase the degree of lattice distortion, leading to lower lattice thermal conductivity. The cocktail effect promotes synergy among the material's components.

[0003] However, currently, there are very few N-type high-entropy semiconductors that can be applied in the thermoelectric field. An important method for developing novel N-type high-entropy semiconductors is solid-state reaction. Identical crystal structures are a necessary condition for the formation of an infinite solid solution between components; for elements with different structures, their mutual solubility is usually limited. Therefore, forming a stable single-phase solid solution with the potential to become an N-type thermoelectric material by having five or more main elements, each competing for the same crystallization sites in a molar ratio of 5-35%, is extremely challenging. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide an N-type high-entropy semiconductor material, AgBiPbSe2S, and its preparation. By improving the material's composition, the obtained AgBiPbSe2S material can function as both an N-type semiconductor and possesses high-entropy characteristics. The high-entropy semiconductor material obtained by this invention has the chemical formula AgBiPbSe2S, is an N-type semiconductor material, has a face-centered cubic lattice structure, and belongs to the [missing information - likely a class of semiconductors]. Space groups, in particular, can be used as N-type thermoelectric materials. Furthermore, based on this invention, a solid-state reaction can be achieved through high-temperature melting to obtain the target AgBiPbSe2S material, which is convenient to prepare and can be mass-produced.

[0005] To achieve the above objectives, according to one aspect of the present invention, an N-type high-entropy semiconductor material is provided, characterized in that its chemical formula is AgBiPbSe2S, wherein the atomic ratio of Ag, Bi, Pb, Se, and S elements is 1:1:1:2:1; the material has a face-centered cubic lattice structure and a space group of [missing information].

[0006] As a further preferred embodiment of the present invention, Ag, Bi, and Pb randomly occupy cation sites and compete with each other;

[0007] Se and S randomly occupy anion sites and compete with each other;

[0008] The configuration entropy of AgBiPbSe₂S is greater than 1.5R, where R = 8.314 J mol. -1 K -1 .

[0009] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned N-type high-entropy semiconductor material, characterized by comprising the following steps:

[0010] (1) Prepare raw material powder: Under a protective atmosphere, weigh the elemental material powder corresponding to each element according to the nominal chemical dosage ratio of the chemical formula AgBiPbSe2S.

[0011] (2) Powder mixing: The various powders obtained in step (1) are thoroughly mixed to obtain a mixed powder;

[0012] (3) Vacuum sealing: Place the mixed powder obtained in step (2) into a quartz tube and evacuate to a pressure not exceeding 10. -5 Seal after mounting;

[0013] (4) High-temperature melting: The vacuum-sealed quartz tube obtained in step (3) is kept at 950℃-1050℃ for 24-30 hours for high-temperature melting. After melting, the temperature is lowered to obtain the melted ingot.

[0014] As a further preferred embodiment of the present invention, the preparation method further includes the following steps:

[0015] (5) Ingot crushing: The smelted ingot obtained in step (4) is crushed into powder, which is AgBiPbSe2S material powder.

[0016] As a further preferred embodiment of the present invention, the preparation method further includes the following steps:

[0017] (6) Discharge plasma sintering: The AgBiPbSe2S material powder obtained in step (5) is filled into a graphite mold and then subjected to discharge plasma sintering to obtain AgBiPbSe2S material block; wherein, the discharge plasma sintering meets the following requirements: the furnace cavity vacuum degree is less than 8Pa, the axial pressure is 45-50MPa, the sintering temperature is 480℃-500℃, and the sintering time is 10-15 minutes; and after the discharge plasma sintering is completed, the furnace is cooled to room temperature and the pressure is gradually removed.

[0018] As a further preferred embodiment of the present invention, in step (1), the protective atmosphere is argon.

[0019] As a further preferred embodiment of the present invention, in step (4), the heating time used for high-temperature melting is 14-20 hours, thereby heating to 950℃-1050℃.

[0020] As a further preferred embodiment of the present invention, in step (5), the pulverization is specifically carried out using a planetary ball mill.

[0021] According to another aspect of the present invention, the present invention provides the application of the above-mentioned N-type high-entropy semiconductor material as an N-type thermoelectric semiconductor material.

[0022] As a further preferred embodiment of the present invention, the N-type high-entropy semiconductor material is specifically AgBiPbSe2S material bulk.

[0023] Compared with existing technologies, the technical solution conceived in this invention, by introducing Pb and S into AgBiSe2-based materials, utilizes five elements—Ag, Bi, Pb, Se, and S—to increase the configuration entropy, overcoming the problem of low solubility between different components. This allows for a smooth solid-state reaction to obtain a stable, face-centered cubic single-phase AgBiPbSe2S material. The AgBiPbSe2S material obtained by this invention forms a face-centered cubic lattice structure (belonging to...). The space group increases the configurational entropy, overcomes the problem of low solubility between different components, and enables the solid-phase reaction to proceed smoothly to obtain a stable, face-centered cubic single-phase AgBiPbSe2S material.

[0024] For the AgBiPbSe2S material of the present invention, according to the formula (k B , Ω, n, x i and N A are the Boltzmann constant, atomic occupation probability, number of atoms of the substituted component, molar content of the i-th component, and Avogadro number respectively), it can be calculated that its configurational entropy is greater than 1.5R (R = 8.314 J mol -1 K -1 ), belonging to the high-entropy material series. Moreover, the increase in configurational entropy expands the solid solubility between the selected elements, providing a new idea for the construction of new high-entropy semiconductors.

[0025] The AgBiPbSe2S material of the present invention exhibits an N-type semiconductor material and has good N-type characteristics, with a negative Seebeck coefficient. The present invention fills the gap in N-type high-entropy semiconductor materials. Different from the existing high-entropy materials (such as AgMnGeSbTe4, AgMnSnSbTe4, AgMnPbSbTe4, etc.) which are basically P-type materials, the Seebeck coefficient of the AgBiPbSe2S material of the present invention is negative. The obtained N-type high-entropy semiconductor material of the present invention has strong universality and can be used in combination with various known P-type materials in the prior art (such as PbTe, SnTe, AgMnGe / Sn / PbSbTe4, etc.).

[0026] In the present invention, by introducing a certain proportion of Pb and S into the AgBiSe2-based material, the single-phase high-entropy semiconductor AgBiPbSe2S has an important impact on the thermoelectric properties of the generated material. The inventors also tried different proportions of Pb and S during the R & D process (as shown in Comparative Example 1 below), but the absolute value of the Seebeck coefficient of the obtained materials was relatively low. In the AgBiPbSe2S material of the present invention, the three elements Ag, Bi, and Pb randomly occupy the cation positions and compete with each other; the two elements Se and S randomly occupy the anion positions and compete with each other. The reason why the atomic ratio of Se to S in the material is controlled to be 2:1 instead of other (3 - a):a (where 0 < a < 3) is that when Se:S is 2:1, the material can maintain a single-phase structure and have the N-type semiconductor characteristics of high thermoelectric performance, with a high absolute value of the Seebeck coefficient and a high ZT value. As shown in Comparative Example 1 below, when the ratio of Se:S is changed to 3:1, although a single-phase material can also be formed, the thermoelectric performance is poor.

[0027] The AgBiPbSe2S semiconductor material of this invention has a face-centered cubic crystal structure. Unlike low-entropy N-type semiconductor materials (such as PbTe, PbS, and Ag2Te), the AgBiPbSe2S material of this invention has a configurational entropy greater than 1.5R, classifying it as a high-entropy material. Furthermore, AgBiPbSe2S exhibits low thermal conductivity, excellent thermoelectric properties, and superior mechanical properties (for example, the thermal conductivity of AgBiPbSe2S at 823 K (i.e., 550 °C) is less than 0.54 W / m). -1 K -1 Thermoelectric figure of merit is greater than 0.64, and Vickers hardness at room temperature is greater than 192H. v ).

[0028] In summary, this invention has a face-centered cubic structure. The N-type high-entropy semiconductor material AgBiPbSe2S effectively expands the material types of N-type high-entropy semiconductor materials, and can be used as an N-type thermoelectric material with good thermoelectric properties. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the N-type high-entropy semiconductor AgBiPbSe2S of the present invention.

[0030] Figure 2 The X-ray diffraction results of the ingot powder of the N-type high-entropy semiconductor AgBiPbSe2S prepared in Example 1 are shown.

[0031] Figure 3 The images show backscattered electron images (SEM) of the polished surface of the N-type high-entropy semiconductor AgBiPbSe2S bulk material prepared in Example 1, as well as energy dispersive spectroscopy (EDS) analysis of the matrix composition; wherein, Figure 3 (a) in the image corresponds to a backscattered electron image. Figure 3 (b), (c), (d), (e), and (f) in the diagram correspond to the EDS plots of Ag, Bi, Pb, Se, and S elements, respectively.

[0032] Figure 4 This is a transmission electron microscope (TEM) image of the N-type high-entropy semiconductor AgBiPbSe2S bulk material prepared in Example 1.

[0033] Figure 5 The results are from the absorbance test of the N-type high-entropy semiconductor AgBiPbSe2S bulk material prepared in Example 1.

[0034] Figure 6 The results are from the Seebeck coefficient test of the N-type high-entropy semiconductor AgBiPbSe2S bulk material prepared in Example 1.

[0035] Figure 7The graph shows the thermoelectric figure of merit of the N-type high-entropy semiconductor AgBiPbSe2S bulk material prepared in Example 1 as a function of temperature.

[0036] Figure 8 (AgBiSe2) prepared for Comparative Example 1 0.6 (PbS) 0.4 Results of Seebeck coefficient test on the block. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0038] Example 1:

[0039] The preparation method of N-type high-entropy semiconductor AgBiPbSe2S includes the following steps:

[0040] (1) In a glove box under an argon protective atmosphere, weigh out elemental silver, bismuth, lead, selenium, and sulfur. The mass of each element is determined according to the chemical formula AgBiPbSe2S. The weighing balance used in this embodiment has an error range of ±0.0005g. The raw materials corresponding to these elements are all elemental substances.

[0041] (2) Manually mix the initially weighed powder in a mortar for 30 minutes.

[0042] (3) Vacuum sealing. Place the thoroughly mixed powder into a quartz tube and evacuate to 10°C. -5 Seal after mounting.

[0043] (4) High-temperature smelting. The vacuum-sealed quartz tube is placed in a box furnace for high-temperature smelting. The smelting conditions are: slowly heating from room temperature to 950°C over 15 hours, holding at 950°C for 24 hours, and then cooling to obtain the smelted ingot.

[0044] (5) Ingot crushing: The ingot obtained by high-temperature melting is crushed into powder using a planetary ball mill for 30 minutes.

[0045] (6) Rapid sintering. The collected ingot powder is loaded into a graphite mold and then subjected to discharge plasma sintering. The sintering conditions are: furnace cavity vacuum degree less than 8 Pa, axial pressure of 45 MPa, rapid heating to the sintering temperature (500℃), holding for 15 minutes, and then cooling to room temperature with the furnace and gradually removing the pressure to obtain bulk material.

[0046] The crystal structure of the N-type high-entropy semiconductor AgBiPbSe2S material is as follows: Figure 1 As shown.

[0047] The N-type high-entropy semiconductor AgBiPbSe2S material prepared in Example 1 maintains a single... The crystal structure of the ingot powder is shown in the X-ray diffraction results. Figure 2 As shown ( Figure 2 In the text, the "AgBiPbSe2S" data corresponds to the measured data of the product in Example 1; the "simulated AgBiPbSe2S" data is obtained through simulation using Diamond and GSAS software.

[0048] The N-type high-entropy semiconductor AgBiPbSe2S material prepared in Example 1 has a uniform elemental distribution, such as... Figure 3 As shown in the table below, the actual atomic ratios are very close to the nominal atomic ratios. Considering the objective errors inherent in the detection methods, the ratio of the number of Ag, Bi, Pb, Se, and S atoms in the prepared bulk material can be considered equivalent to satisfying the nominal atomic ratio (i.e., 1:1:1:2:1).

[0049] Table: Actual atomic ratio of N-type high-entropy semiconductor AgBiPbSe2S bulk material prepared in Example 1

[0050] Element Atomic (%) Ag 17.24 Bi 15.95 Pb 17.04 Se 33.89 S 15.88

[0051] In addition, the N-type high-entropy semiconductor AgBiPbSe2S bulk material prepared in Example 1 was characterized by transmission electron microscopy, and the results are as follows: Figure 4 As shown, it has a face-centered cubic single-phase structure.

[0052] The band gap of the N-type high-entropy semiconductor AgBiPbSe2S is 0.408 eV, such as Figure 5 As shown.

[0053] The Seebeck coefficient of the N-type high-entropy semiconductor AgBiPbSe2 increases from -117 μV / K at 300 K to -176 μV / K at 823 K, exhibiting N-type semiconductor characteristics, such as... Figure 6 As shown.

[0054] The thermoelectric figure of merit of the N-type high-entropy semiconductor AgBiPbSe2S is 0.64 at 500℃ (i.e., 773K). Figure 7 As shown.

[0055] Furthermore, the AgBiPbSe2S obtained in Example 1 has a thermal conductivity of less than 0.54 W / m² at 823 K (i.e., 550 °C). -1 K -1Thermoelectric figure of merit is greater than 0.64, and Vickers hardness at room temperature is greater than 192H. v .

[0056] Comparative Example 1

[0057] N-type high-entropy semiconductor (AgBiSe2) 0.6 (PbS) 0.4 The preparation method includes the following steps:

[0058] (1) In a glove box under an argon protective atmosphere, weigh out elemental silver, bismuth, lead, selenium, and sulfur. The mass of each element should be in accordance with (AgBiSe2). 0.6 (PbS) 0.4 Chemical formulas were used for weighing. The weighing balance used in this comparative example has an error range of ±0.0005g. The raw materials corresponding to these elements are all elemental substances.

[0059] (2) Manually mix the initially weighed powder in a mortar for 30 minutes.

[0060] (3) Vacuum sealing. Place the well-mixed powder in a quartz tube, evacuate to 10⁻⁵ Torr, and then seal.

[0061] (4) High-temperature smelting. The vacuum-sealed quartz tube is placed in a box furnace for high-temperature smelting. The smelting conditions are: slowly heating from room temperature to 950°C over 15 hours, holding at 950°C for 24 hours, and then cooling to obtain the smelted ingot.

[0062] (5) Ingot crushing: The ingot obtained by high-temperature melting is crushed into powder using a planetary ball mill for 30 minutes.

[0063] (6) Rapid sintering. The collected ingot powder is loaded into a graphite mold and then subjected to discharge plasma sintering. The sintering conditions are: furnace cavity vacuum degree less than 8 Pa, axial pressure of 45 MPa, rapid heating to the sintering temperature (500℃), holding for 15 minutes, and then cooling to room temperature with the furnace and gradually removing the pressure to obtain bulk material.

[0064] The N-type high-entropy semiconductor (AgBiSe2) was prepared. 0.6 (PbS) 0.4 Seebeck coefficient of bulk materials, such as Figure 8 As shown.

[0065] In the present invention, the atomic ratio of Se:S is controlled to be 2:1. The resulting AgBiPbSe2S material maintains a single-phase structure and exhibits N-type semiconductor characteristics with high thermoelectric performance, showing great potential in thermoelectric performance. For other Se:S ratios, such as 2×(1 - x):x (0 < x < 1; for example, x = 0.4 corresponding to Comparative Example 1), although single-phase materials can also be formed, their thermoelectric performance is poor. Taking the Figure 8 obtained in Comparative Example 1 as an example, compared with Figure 8 , the absolute value of the Seebeck coefficient of the AgBiPbSe2S material obtained in Example 1 of the present invention (as shown in Figure 6 ) is significantly higher than that of Comparative Example 1 (a detailed comparison table of the Seebeck values of the products of Example 1 and Comparative Example 1 is shown in the following table). It can be seen that Example 1 obtained based on the present invention has higher thermoelectric performance.

[0066] Table: Comparison table of Seebeck coefficient values of the materials obtained in Example 1 of the present invention and Comparative Example 1 at different test temperatures

[0067]

[0068] The N-type high-entropy semiconductor AgBiPbSe2S material obtained in the present invention belongs to a single phase, and its lattice structure is a face-centered cubic structure (as shown in Figure 1 ). The space group is . For a single-phase face-centered cubic structure material, its theoretical powder XRD pattern will have 6 obvious diffraction peaks (as shown in Figure 2 ), and the powder XRD pattern of the actually prepared material in the example is very well matched with the theoretical peaks (also as shown in Figure 2 ).

[0069] In addition, in the rapid sintering step of the above-mentioned example of the present invention, the axial pressure is preferably controlled to be 45 MPa, and the density of the corresponding obtained materials is greater than 96%. According to actual needs, other axial pressure settings can also be adopted to obtain target products with higher or lower densities (different axial pressures will not affect the crystal structure of the material because after high-temperature melting, the generated material is already a single-phase material with a face-centered cubic structure; of course, similar to the conventional requirements, attention also needs to be paid to avoiding excessive pressure and material extrusion for the axial pressure).

[0070] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An application of an N-type high-entropy semiconductor material as a high-hardness N-type thermoelectric semiconductor material, wherein the chemical formula of the N-type high-entropy semiconductor material is AgBiPbSe2S, wherein, The atomic ratio of Ag element, Bi element, Pb element, Se element and S element is 1:1:1:2:1; the material lattice structure is face-centered cubic structure, and the space group is ; the Vickers hardness at room temperature is greater than 192H v ; Furthermore, the N-type high-entropy semiconductor material is specifically an AgBiPbSe2S material bulk, which is prepared according to a method including the following steps: (1) Prepare raw material powder: Under a protective atmosphere, weigh the elemental material powder corresponding to each element according to the nominal chemical dosage ratio of the chemical formula AgBiPbSe2S. (2) Powder mixing: The various powders obtained in step (1) are thoroughly mixed to obtain a mixed powder; (3) Vacuum sealing: Place the mixed powder obtained in step (2) into a quartz tube and evacuate to a pressure not exceeding 10. -5 Seal after mounting; (4) High temperature melting: The vacuum-sealed quartz tube obtained in step (3) is kept at 950℃-1050℃ for 24-30 hours for high temperature melting, and then cooled to obtain a melted ingot. (5) Ingot crushing: The smelted ingot obtained in step (4) is crushed into powder, which is AgBiPbSe2S material powder; (6) Discharge plasma sintering: The AgBiPbSe2S material powder obtained in step (5) is filled into a graphite mold and then subjected to discharge plasma sintering to obtain AgBiPbSe2S material block; wherein, the discharge plasma sintering meets the following requirements: the furnace cavity vacuum degree is less than 8 Pa, the axial pressure is 45-50 MPa, the sintering temperature is 480℃-500℃, and the sintering time is 10-15 minutes; and after the discharge plasma sintering is completed, the furnace is cooled to room temperature and the pressure is gradually removed.

2. The use according to claim 1, characterized in that, In the N-type high-entropy semiconductor material, Ag, Bi, and Pb randomly occupy cation sites and compete with each other; Se and S randomly occupy anion sites and compete with each other; The configurational entropy of AgBiPbSe2S is greater than 1.5R, where R = 8.314 J mol 1 K 1 .

3. The use according to claim 1, characterized in that, In step (1), the protective atmosphere is argon.

4. The use according to claim 1, characterized in that, In step (4), the heating time used for high-temperature melting is 14-20 hours, thereby raising the temperature to 950℃-1050℃.

5. The use according to claim 1, characterized in that, In step (5), the pulverization is specifically carried out using a planetary ball mill.

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