A chalcogenide compound, method of making and thermoelectric applications thereof

Abstract

The application provides a novel chalcogenide compound and a preparation method and application thereof, and the chemical general formula is M 3Bi4 Q 9, wherein M one or two selected from metals Pd and Pt, Q one or two or more combinations of chalcogen elements S, Se and Te. The series of materials belong to the trigonal system, R -3 space group, with a three-dimensional extended crystal structure, and are a novel thermoelectric material. In the structure, M 6 Q 12 ] 12‑ The "hard clusters" are dispersed in Bi- Q The "soft lattice" forms a unique crystal structure of "soft in hard", which has good thermoelectric performance on the basis of ensuring unobstructed electric transport characteristics. Through proper carrier doping, excellent thermoelectric performance can be achieved, and the material is expected to be used in waste heat recovery, thermoelectric refrigeration, thermoelectric power generation and other thermoelectric conversion related fields.

Description

Technical Field

[0001] This invention relates to the preparation of inorganic crystalline materials and their application as thermoelectric materials, belonging to the field of inorganic materials. Background Technology

[0002] Thermoelectric conversion technology can directly convert electrical energy into heat energy through the Seebeck or Peltier effect of thermoelectric materials, which is of great value for the efficient conversion and utilization of energy. High-performance thermoelectric materials are the core of achieving efficient thermoelectric conversion, and their performance can be measured through dimensionless parameters. ZT Value measurement. Specifically defined as... ZT = S 2 σ T / κ ,in S Here, σ is the Seebeck coefficient, and σ is the conductivity. T For temperature, κ is the thermal conductivity. S 2 σ reflects the electrical properties of a material and is collectively referred to as the power factor. PF ), κ Mainly determined by electronic thermal conductivity κ e and lattice thermal conductivity κ L Contribution. To achieve greater [goals / achievements]. ZT To improve the power factor of materials while maintaining low thermal conductivity, it is necessary to increase the power factor of the material. Since the mid-20th century, materials such as bismuth telluride, lead telluride, cobaltite, and magnesium antimonide have been used in thermoelectric conversion. However, these materials still face various problems such as high requirements for preparation conditions and high toxicity of raw materials. Exploring and developing new high-efficiency thermoelectric materials remains a core task in the field of thermoelectrics and has significant scientific and practical value. Summary of the Invention

[0003] The purpose of this invention is to provide a chalcogenide compound, its preparation method, and its thermoelectric applications.

[0004] In a first aspect, the present invention provides a chalcogenide compound with the chemical formula: M 3Bi4 Q 9, of which M It can be any one or a combination of two of the metallic elements Pd or Pt. Q It is any one or a combination of two or more of the sulfide elements S, Se, and Te.

[0005] The compound belongs to the trigonal crystal system. R -3 space group, with a three-dimensional extended crystal structure, in which MFor planar tetragonal coordination, six MQ 4. Formed by connecting through shared vertices [ M 6 Q 12 ] 12- Clusters, clusters via Bi- Q Coordination polyhedra are interconnected.

[0006] In the compound, it is possible to... M Bit element, Bi and Q The dopant elements are doped with different valence elements, either individually or simultaneously, with the concentration of the dopant elements ranging from 0 at% to 20 at%.

[0007] In a second aspect, the present invention provides a method for preparing the above-mentioned chalcogenides, comprising: placing a raw material containing Pd, Pt, Bi, S, Se, Te and doping elements under vacuum conditions, holding it at 600-800°C for more than 24 hours, and then cooling it down.

[0008] The molar ratios of Pd / Pt, Bi, and S / Se / Te elements in the raw material are (2.4~3):(3.2~4):(7.2~9). S, Se, and Te elements can originate from the same raw material compound as the metal elements; for example, the raw material may contain Bi₂S₃, Bi₂Se₃, Bi₂Te₃, PtS, PdS, etc. Pd or Pt elements can originate from elemental raw materials or their halides such as PdCl₂, PtCl₂, etc. M The doping element can be Cu + Ag + Elements such as Pb can be used at the Bi site. 2+ Sn 2+ Sn 4+ Elements, Q The doping element can be Cl. - ,Br - I - Elements such as...

[0009] The high-temperature reaction may include heating from room temperature to 600-800°C within 10 hours.

[0010] The high-temperature reaction may include heating to 600-800°C and holding at that temperature for 48-72 hours, then cooling to 500°C within 48-72 hours, and then naturally cooling to room temperature.

[0011] In the above preparation process, fluxes can be added to the reaction raw materials. Fluxes include, but are not limited to, alkali metal halides such as KCl, KI, RbCl, CsI, etc., to promote crystal growth.

[0012] Thirdly, the present invention provides a use of the above-mentioned chalcogenide compound, characterized in that it can be used for thermoelectric conversion.

[0013] This invention provides a chalcogenide compound, its preparation method, and its uses, with the general chemical formula being: M 3Bi4 Q 9, of which M Selected from metals Pd and Pt, Q Selected from the chalcogenides S, Se, and Te. This series of materials belongs to the trigonal crystal system. R The -3 space group, possessing a three-dimensional extended structure, is a class of thermoelectric materials. Its elements include... M Bi Q The valence states are +2, +3, and -2, respectively. Each element can be partially replaced by other heterovalent elements to achieve a certain concentration of doping. The concentration of the doped element is between 0 at% and 20 at%. M For planar tetragonal coordination, six MQ 4. Formed by connecting through shared vertices [ M 6 Q 12 ] 12- Clusters, with inter-cluster communication via Bi- Q Coordination polyhedra connect to each other, forming a three-dimensional extended crystal structure. M 6 Q 12 ] 12- stable geometric configuration and strong cluster strength M - Q The bonds make it a "hard cluster" with less thermal vibration, while the longer Bi- Q Bonds and smaller bonds enable Bi- Q The coordination polyhedra form a relatively soft sublattice. This unique "soft yet hard" crystal structure brings strong lattice anharmonicity, greatly compressing the material's lattice thermal conductivity. While ensuring smooth electrical transport characteristics, it also possesses low thermal conductivity, thus achieving excellent thermoelectric performance. Specifically, the compound Pt3Bi4S6Se3 has a lattice thermal conductivity of only 0.39 W / (m K) at 773 K, even without heavy carrier doping. ZT The value can reach up to 0.56. Compared with similar materials, this material has superior thermoelectric properties. By appropriately doping this material with charge carriers, excellent thermoelectric performance can be achieved, making it a promising candidate for applications in thermoelectric conversion fields such as waste heat recovery, thermoelectric refrigeration, and thermoelectric power generation. Attached Figure Description

[0014] Figure 1 For the present invention M 3Bi4 Q 9. Schematic diagram of crystal structure;

[0015] Figure 2 The powder X-ray diffraction patterns of Pt3Bi4S9 and Pt3Bi4Se9 in Examples 1 and 2 of this invention are shown below.

[0016] Figure 3 The lattice thermal conductivity diagrams of Embodiments 1-4 of the present invention are shown;

[0017] Figure 4 The conductivity diagrams of embodiments 1-4 of the present invention are shown;

[0018] Figure 5 The Seebeck coefficient diagrams for embodiments 1-4 of the present invention are shown;

[0019] Figure 6 Examples 1-4 of the present invention are shown. ZT Value graph. Detailed Implementation

[0020] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0021] This disclosure relates to a chalcogenide compound, its preparation method, and its thermoelectric applications, with the general chemical formula being: M 3Bi4 Q 9, of which M Selected from metals Pd and Pt, Q Selected from the chalcogenides S, Se, and Te. This series of materials belongs to the trigonal crystal system. R The material belongs to the -3 space group and has a three-dimensional extended structure. It exhibits excellent thermoelectric conversion properties and can be used as... M 3Bi4 Q One example in 9, Pt3Bi4S6Se3, has a lattice thermal conductivity of only 0.39 W / (m K) at 773 K, without heavy carrier doping. ZT The value can reach as high as 0.56. This type of material can be used to make thermoelectric devices and has promising applications in waste heat recovery, thermoelectric refrigeration, and thermoelectric power generation.

[0022] Implementation Form 1

[0023] Chalcogenides of this embodiment M 3Bi4 Q 9 (M = Pd, Pt, Q = S, Se, Te) belong to the trigonal crystal system. R -3 space group. Furthermore, the compound of this embodiment has a three-dimensional extended crystal structure, composed of [ M 6 Q 12 ] 12- Bi- clusters and inter-cluster bi- QIt is formed by connecting coordination polyhedra (see Figure 1 ). Among them, elements M Bi Q The valence states are +2, +3, and -2, respectively. Each element can be partially replaced by other heterovalent elements to achieve a certain concentration of doping. The concentration of the doped element is between 0 at% and 20 at%. M For planar tetragonal coordination, six MQ 4. Formed by connecting through shared vertices [ M 6 Q 12 ] 12- Clusters, with inter-cluster communication via Bi- Q Coordination polyhedra are interconnected. M 3Bi4 Q The unit cell parameters of an example of Pt3Bi4S9 are as follows: a = b = 13.3434(4) Å, c =13.3414(6) Å, a = b = 90°, g = 120° Z = 6, and its crystallographic data are shown in Table 1. As M 3Bi4 Q 9. The cell parameters of another example of Pt3Bi4Se9 are: a = b = 13.8675(9) Å, c = 13.8381(14) Å, a = b = 90°, g = 120° Z = 6, and its crystallographic data are shown in Table 1.

[0024] Table 1 Pt3Bi4 Q 9 ( Q Crystallographic data of S, Se)

[0025] Molecular formula <![CDATA[Pt3Bi4S9]]> <![CDATA[Pt3Bi4Se9]]> molecular weight 1709.73 2131.83 Space Group -3 -3 a (Å) 13.3434(4) 13.8675(9) c (Å) 13.3414(6) 13.8381(14) <![CDATA[Volume (Å 3 )]]> 2057.15(15) 2304.6(4) <![CDATA[Density (g×cm -3 )]]> 8.281 9.216

[0026] The following describes the chalcogenides of the present invention by way of example. M 3Bi4 Q Preparation method of 9.

[0027] The raw materials containing platinum, palladium, bismuth, sulfur, selenium, tellurium, and other doping elements can be placed under vacuum conditions and reacted at high temperature to prepare the product. The raw materials can be thoroughly ground and mixed uniformly, for example, in a mortar. The vacuum conditions can be, for example, evacuated to 0.1–0.3 Pa, and the mixed raw materials can be sealed in, for example, a quartz tube. The molar ratios of platinum / palladium, bismuth, sulfur / selenium / tellurium elements in the raw materials can be (2.4–3):(3.2–4):(7.2–9), thereby further obtaining a product with higher purity. S, Se, and Te elements can originate from the same raw material compound as the metal elements; for example, the raw materials may contain Bi₂S₃, Bi₂Se₃, Bi₂Te₃, PtS, PdS, etc. Pd or Pt elements can originate from elemental raw materials or their halides such as PdCl₂, PtCl₂, etc. M The doping element can be Cu + Ag + Elements such as Pb can be used at the Bi site. 2+ Sn 2+ Sn 4+ Elements, Q The doping element can be Cl. - ,Br - I - Elements such as...

[0028] The mixed raw materials can be placed under vacuum and heated to 600-800°C, held at that temperature for more than 24 hours, and then cooled. In this high-temperature reaction method, it is preferable to heat to 600-800°C at a rate of 60-80°C / hour to achieve the preparation of crystals with high quality and purity. In some embodiments, the reaction vessel can be a quartz tube, which is evacuated to 0.1 Pa, melted and sealed, and placed in a muffle furnace, where it is heated to 600-800°C at a rate of 60-80°C / hour. Furthermore, it is preferable to heat to 600-800°C and hold for 48-72 hours, then cool to 500°C at a rate of 3-8°C / hour, and then allow to cool naturally to room temperature, thereby achieving the growth of larger crystals.

[0029] In some embodiments, chalcogenides M 3Bi4 Q The preparation method of 9 may include:

[0030] (a) Mix the raw materials containing platinum / palladium, bismuth, sulfur / selenium / tellurium elements in a molar ratio of (2.4~3):(3.2~4):(7.2~9) evenly, load them into a reaction vessel, and seal the vessel after evacuation.

[0031] (b) Place the sealed reaction vessel from step (a) into a muffle furnace, heat to 600–800°C, hold at that temperature for a period of time, and then cool to room temperature to obtain the desired product. M 3Bi4Q 9.

[0032] This invention provides a chalcogenide compound, its preparation method, and its uses, with the general chemical formula being: M 3Bi4 Q 9, of which M Selected from metals Pd and Pt, Q The materials are selected from chalcogenides S, Se, and Te. The crystal structure of this material exhibits a unique […]. M 6 Q 12 ] 12- Cluster. M 6 Q 12 ] 12- stable geometric configuration and strong cluster strength M - Q The bonds make it a "hard cluster" with less thermal vibration, while the longer Bi- Q Bonds and smaller bonds enable Bi- Q The coordination polyhedra form a relatively soft sublattice. This unique "soft yet hard" crystal structure brings strong lattice anharmonicity, greatly compressing the material's lattice thermal conductivity. The three-dimensional extended crystal structure ensures smooth electrical transport properties, thus achieving excellent thermoelectric performance. The compound Pt3Bi4S6Se3 exhibits a lattice thermal conductivity of only 0.39 W / (m K) at 773 K, even without heavy carrier doping. ZT The value can reach up to 0.56, and it has application prospects in thermoelectric fields such as waste heat recovery, thermoelectric refrigeration, and thermoelectric power generation.

[0033] The chalcogenides of the present invention M 3Bi4 Q 9 M Bi Q The valence states are +2, +3, and -2, respectively. Each element can be partially substituted by other elements of different valence to achieve a certain concentration of doping, with the concentration of the dopant element ranging from 0 at% to 20 at%. Doping at a certain concentration can significantly change the electrical and thermal transport properties of the material, thereby facilitating the optimization and achievement of better thermoelectric performance. M The doping element can be Cu + Ag + Elements such as Pb can be used at the Bi site. 2+ Sn 2+ Sn 4+ Elements, Q The doping element can be Cl. - ,Br - I - Elements such as...

[0034] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0035] In the following embodiments, unless otherwise specified, the reagents, materials and instruments used are all conventional reagents, materials and instruments, and are commercially available. The reagents involved can also be synthesized by conventional synthesis methods.

[0036] Example 1

[0037] Preparation of Pt3Bi4S9: 0.5853 g Pt, 1.0283 g Bi2S3, and 0.0962 g S were weighed and thoroughly ground in a mortar. The mixture was then transferred to a quartz tube with an inner diameter of 1 cm and vacuum-sealed. The vacuum was then evacuated to 0.1 Pa. The sealed quartz tube was placed in a muffle furnace, and the following holding program was set: the temperature was raised to 650 °C after 10 hours, held at 650 °C for 48 hours, and then cooled to 500 °C at a rate of 3 °C per hour, followed by natural cooling to room temperature. The product was removed from the quartz tube, yielding polycrystalline Pt3Bi4S9. The obtained pure-phase powder was then subjected to SPS sintering at 550 °C and 60 MPa to finally produce a bulk thermoelectric material.

[0038] Example 2

[0039] Preparation of Pt3Bi4Se9: 0.5853 g Pt, 1.3097 g Bi2Se3, and 0.2369 g Se were weighed and thoroughly ground in a mortar. The mixture was then transferred to a quartz tube with an inner diameter of 1 cm and vacuum-sealed. The vacuum was evacuated to 0.1 Pa. The sealed quartz tube was placed in a muffle furnace, and the following holding program was set: the temperature was raised to 650 °C after 10 hours, held at 650 °C for 48 hours, and then cooled to 500 °C at a cooling rate of 3 °C per hour, followed by natural cooling to room temperature. The product was removed from the quartz tube, yielding polycrystalline Pt3Bi4Se9. The obtained pure phase powder was sintered by SPS at 450 °C and 60 MPa to finally produce a bulk thermoelectric material.

[0040] Example 3

[0041] Preparation of Pt3Bi4S6Se3: 0.5853 g Pt, 1.0283 g Bi2S3, and 0.2369 g Se were weighed and thoroughly ground in a mortar. The mixture was then transferred to a quartz tube with an inner diameter of 1 cm and vacuum-sealed. The vacuum was then evacuated to 0.1 Pa. The sealed quartz tube was placed in a muffle furnace, and the following holding program was set: the temperature was raised to 650 °C after 10 hours, held at 650 °C for 48 hours, and then cooled to 500 °C at a rate of 3 °C per hour, followed by natural cooling to room temperature. The product was removed from the quartz tube, yielding polycrystalline Pt3Bi4S6Se3. The obtained pure-phase powder was then subjected to SPS sintering at 500 °C and 60 MPa to finally produce a bulk thermoelectric material.

[0042] Example 4

[0043] Preparation of Pt3Bi4S3Se6: 0.5853 g Pt, 1.3097 g Bi2Se3, and 0.0962 g S were weighed and thoroughly ground in a mortar. The mixture was then transferred to a quartz tube with an inner diameter of 1 cm and vacuum-sealed. The vacuum was evacuated to 0.1 Pa. The sealed quartz tube was placed in a muffle furnace, and the following holding program was set: the temperature was raised to 650 °C after 10 hours, held at 650 °C for 48 hours, and then cooled to 500 °C at a rate of 3 °C per hour, followed by natural cooling to room temperature. The product was removed from the quartz tube, yielding polycrystalline Pt3Bi4S3Se6. The obtained pure-phase powder was sintered by SPS at 450 °C and 60 MPa to finally produce a bulk thermoelectric material.

[0044] Example 5

[0045] Performance testing:

[0046] 1) The obtained Pt3Bi4S9 and Pt3Bi4Se9 crystals were ground and then subjected to powder X-ray diffraction tests. The results are as follows: Figure 2 As shown, the obtained powder X-ray diffraction pattern is consistent with the theoretical X-ray diffraction pattern of the crystal obtained from the single-crystal structure analysis, proving that the obtained crystal has high purity.

[0047] 2) The lattice thermal conductivity of Pt3Bi4S9, Pt3Bi4S6Se3, Pt3Bi4S3Se6, and Pt3Bi4Se9 after SPS sintering was tested, and the results are as follows: Figure 3As shown. The obtained samples have extremely low lattice thermal conductivity, with Pt3Bi4S6Se3 exhibiting a lattice thermal conductivity as low as 0.39 W / (m K) at 773 K, Pt3Bi4S9 exhibiting a lattice thermal conductivity of 0.45 W / (m K) at 773 K, Pt3Bi4Se9 exhibiting a lattice thermal conductivity of 0.40 W / (m K) at 773 K, and Pt3Bi4S6Se3 exhibiting a lattice thermal conductivity of 0.39 W / (m K) at 773 K.

[0048] 3) The conductivity of Pt3Bi4S9, Pt3Bi4S6Se3, Pt3Bi4S3Se6, and Pt3Bi4Se9 after SPS sintering was tested, and the results are as follows: Figure 4 As shown, at 323 K, the conductivity of the samples decreased with increasing Se content. Pt3Bi4S9 had the highest conductivity at 323 K, at 185.9 S / cm, followed by Pt3Bi4S6Se3 at 124.2 S / cm, Pt3Bi4S3Se6 at 51.3 S / cm, and Pt3Bi4Se9 at 20.8 S / cm.

[0049] 4) The Seebeck coefficients of Pt3Bi4S9, Pt3Bi4S6Se3, Pt3Bi4S3Se6, and Pt3Bi4Se9 after SPS sintering were tested, and the results are as follows: Figure 5 As shown, the Seebeck coefficients of the materials are all negative, indicating that they possess... n Semiconductor characteristics. The Seebeck coefficients of the various materials at 323 K are -194.8 mV / K (Pt3Bi4S9), -154.8 mV / K (Pt3Bi4S6Se3), -236.5 mV / K (Pt3Bi4S3Se6), and -294.6 mV / K (Pt3Bi4Se9). The obtained materials exhibit high Seebeck coefficients.

[0050] 5) Based on the electrical conductivity, thermal conductivity, and Seebeck coefficient obtained from the tests, calculate the values ​​of each material. ZT Value, result as Figure 6 As shown. Without heavy carrier doping, Pt3Bi4S6Se3 at 773 K... ZT The value is as high as 0.56 for Pt3Bi4S9. ZT With a value as high as 0.53, it has excellent thermoelectric properties.

Claims

1. A chalcogenide compound, characterized in that: (1) The chemical formula is M3Bi4Q9, where M is any one or a combination of two of the metal elements Pd or Pt, and Q is any one or a combination of two or more of the chalcogens S, Se, and Te. (2) It belongs to the trigonal crystal system, space group R-3, and has a three-dimensional extended crystal structure; (3) Where M is a planar tetragonal coordination, and six MQ4s are connected by sharing a vertex to form [M6Q 12 ] 12- Clusters, which are interconnected by Bi-Q coordination polyhedra; (4) The valence state of the M-position element is +2, the valence state of Bi is +3, and the valence state of the Q-position element is -2.

2. The chalcogenide compound according to claim 1, characterized in that: One or more of the M-site elements, Bi and Q-site elements are doped with heterovalent elements, and the concentration of the dopant element is 0 at% to 20 at%.

3. A method for preparing the chalcogenide compound according to claim 2, characterized in that: (1) The raw materials containing Pd / Pt elements, Bi elements, S / Se / Te elements and doped elements are mixed and ground evenly, wherein the molar ratio of Pd / Pt:Bi:S / Se / Te elements is (2.4~3):(3.2~4):(7.2~9); (2) Under vacuum conditions, the sample obtained in step (1) is heated from room temperature to 600~800℃ within 10 hours, kept at that temperature for 48~72 hours, and then cooled to 500℃ within 48~72 hours, and then naturally cooled to room temperature.

4. The method for preparing chalcogenides according to claim 3, characterized in that: A fluxing agent, which is an alkali metal halide, is added to the reaction raw materials.

5. The use of the chalcogenide compound according to claim 1 or 2, characterized in that: It is used in the field of thermoelectric conversion.

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