CN113270535A

CN113270535A - Ru-interstitial high-performance ZrNiSn-based thermoelectric material and preparation method thereof

Info

Publication number: CN113270535A
Application number: CN202110565298.0A
Authority: CN
Inventors: 骆军; 闫昕; 张继业; 郭凯; 王晨阳
Original assignee: University of Shanghai for Science and Technology
Current assignee: University of Shanghai for Science and Technology
Priority date: 2021-05-24
Filing date: 2021-05-24
Publication date: 2021-08-17

Abstract

The present invention provides a high-performance ZrNiSn-based thermoelectric material with Ru interstitials. The chemical formula of the thermoelectric material is ZrNiRu _x Sn, wherein the value range of x is 0≤x≤0.03. The invention also provides a preparation method of the Ru interstitial high-performance ZrNiSn-based thermoelectric material. The Ru interstitial high-performance ZrNiSn-based thermoelectric material provided by the invention is non-toxic, has a short preparation period, has low thermal conductivity, and has good thermoelectric performance in the working temperature range.

Description

Ru-interstitial high-performance ZrNiSn-based thermoelectric material and preparation method thereof

Technical Field

The invention belongs to the technical field of new energy materials, and particularly relates to a Ru-interstitial high-performance ZrNiSn-based thermoelectric material and a preparation method thereof.

Background

In recent times, human beings and nature are continuously interacting, the supply of substances is gradually abundant, the economy is rapidly developed, and meanwhile, the phenomena of limitation of conventional energy sources and increasing environmental safety are accompanied, and the core of the method lies in that the traditional energy sources are not renewable and the environmental deterioration is aggravated by the use of human beings. Therefore, countries around the world focus on new energy materials that are environmentally friendly and renewable. Among them, the thermoelectric material has attracted much attention worldwide because it can achieve direct interconversion of thermal energy and electrical energy using solid internal carriers. The main physical effects involved in thermoelectric materials are: the seebeck effect, the peltier effect and the thomson effect. Thermoelectric devices can be manufactured based on the characteristics of thermoelectric materials, and have the remarkable advantages of small volume, light weight, simple structure, firmness, durability, no need of moving parts and the like, so that the thermoelectric device has wide prospect in commercial application.

Currently, the large-scale market application of thermoelectric materials and devices has not yet reached the economic range of people, and is mainly limited by the current low thermoelectric performance of thermoelectric materials, so that the energy conversion efficiency of thermoelectric devices is relatively lower than that of other energy conversion technologies. In the range of carnot cycle efficiency, the maximum energy conversion efficiency of a thermoelectric material is only related to the dimensionless thermoelectric figure of merit zT ═ S of the material²σ T/κ, the parameters S, σ, T, κ on the right of the equation represent the Seebeck coefficient, electrical conductivity, absolute temperature, and total thermal conductivity of the material, respectively. Materials that generally possess high thermoelectric properties require high seebeck coefficients and electrical conductivity, as well as low thermal conductivity.

Generally, thermoelectric materials can be classified into thermoelectric materials of around room temperature, middle temperature region and high temperature region according to the operating temperature. At present, thermoelectric materials and the technology thereof are applied in large scale in the aspects of converting industrial waste heat and automobile exhaust waste heat, and the exhaust temperature of the waste heat is mostly near the high temperature in work. PbTe, Skuters and Half-Heusler alloys have been widely studied as medium and high temperature thermoelectric materials having excellent thermoelectric properties. However, PbTe-based thermoelectric materials have high toxicity (Pb element) and weak mechanical strength, Skutterudites have relatively low thermal stability, and half-Heusler does not or rarely contain toxic elements and has excellent mechanical properties, thus having better prospects than the former two. For half-Heusler, the highly symmetric crystal structure gives the system a greater degree of energy valley degeneracy, which gives the system a greater effective mass for density of states and hence a higher Seebeck coefficient. Furthermore, such a crystal structure gives it a very high lattice thermal conductivity and thus becomes a major obstacle to limit its thermoelectric performance. At present, many high-performance p-type half-Heusler have been studied and reported, while the thermoelectric performance of n-type half-Heusler is relatively low, and zrsin-based half-Heusler is a typical study object in which it is difficult to improve the thermoelectric performance due to a complicated preparation process and high thermal conductivity.

Therefore, it is necessary to provide a high-performance ZrNiSn-based thermoelectric material having appropriate electrical properties and relatively low thermal conductivity while having a short production cycle, thereby enabling efficient production of the high-thermoelectric-performance ZrNiSn-based thermoelectric material, and a method for producing the same.

Disclosure of Invention

The purpose of the invention is as follows: the invention provides a Ru-interstitial high-performance ZrNiSn-based thermoelectric material and a preparation method thereof.

The technical scheme is as follows: in order to achieve the purpose of the invention, the following technical scheme is adopted: a Ru-gap-filling high-performance ZrNiSn-based thermoelectric material has a chemical formula of ZrNiRu_xSn, wherein the value range of x is more than or equal to 0 and less than or equal to 0.03.

Preferably, x is 0.01, 0.02 or 0.03.

The invention also provides a preparation method of the Ru-interstitial high-performance ZrNiSn-based thermoelectric material, which comprises the following steps:

a. arc melting: according to the value of x, willRespectively weighing metal simple substances Zr, Ni, Ru and Sn with the purity of more than 99.99 percent according to the stoichiometric ratio, and then mixing and smelting the raw materials of all the components in sequence to prepare ZrNiRu_xSn cast ingots are used as reaction precursors;

b. high-energy ball milling: putting a reaction precursor prepared by arc melting into a high-energy ball mill, and crushing the alloy ingot into powder within 10 hours to obtain a powder sample;

and c, SPS sintering: putting the powder sample subjected to high-energy ball milling into a graphite mold in an argon glove box, performing discharge plasma sintering, and then cooling to room temperature to obtain flaky ZrNiRu_xA Sn thermoelectric material.

4. The method for preparing the Ru-interstitial high-performance ZrNiSn-based thermoelectric material as claimed in claim 3, wherein in the step a, with the exception that Zr and Ni are kept in an original ratio, 2-4 wt% of Sn particles are additionally added in advance for samples with different value ranges x to compensate loss, and meanwhile, before alloy melting, elemental metals Zr, Ni, Ru and Sn are subjected to purification melting, and then mixed and repeatedly melted for 3-5 times, so that the alloy components and the structure are uniform.

Preferably, in step a, with the exception of maintaining the original ratio of Zr and Ni, for samples with different value ranges x, 3 wt% of Sn particles are additionally added in advance to compensate for loss, and then mixing and melting are repeated for 3 times.

Preferably, in the step b, the ball milling tank filled with the reaction precursor is subjected to ball milling for 10-20 hours at the rotating speed of 1200-1500 r/min, so that the alloy components and the structure are further uniform.

Preferably, the ball milling in step b is carried out at the rotating speed of 1200r/min for 10 h.

Preferably, ZrNiRu is used in step c_xAnd heating the Sn to 850-950 ℃ at the speed of 40-60 ℃/min, adjusting the pressure to 50-60 Mpa, keeping the temperature and the pressure for 5-15 min at constant temperature and constant pressure, and naturally cooling to room temperature to obtain the Ru-interstitial high-performance ZrNiSn-based thermoelectric material.

Preferably, in the step c, the temperature is kept for 10min at a constant temperature at a heating rate of 50 ℃/min, a sintering temperature of 900 ℃ and a sintering pressure of 50 MPa.

The preferred technical solution of the present inventionThe vacuum degree kept in the steps a, b and c is less than 10^-1pa。

Optimizing the thermoelectric performance of thermoelectric materials requires significantly reducing the thermal conductivity of the materials while regulating the electrical properties of the materials. ZrNiSn has a low carrier concentration and a high thermal conductivity, so that the intrinsic ZrNiSn thermoelectric material has low performance. The invention provides a method for optimizing the electrical property of a ZrNiSn-based thermoelectric material and obviously reducing the thermal conductivity of the ZrNiSn-based thermoelectric material through defect engineering. The Ni-position gap-filling Ru atoms with large mass and radius obviously improve the carrier concentration and optimize the electrical property, simultaneously the gap-filling Ru randomly occupies the vacancy of ZrNiSn and is used as a phonon scattering center, and the crystal lattice thermal conductivity is obviously reduced and the performance of the ZrNiSn-based thermoelectric material is improved by combining the reasons of larger atomic mass of Ru, grain refinement after ball milling and the like. The work lays a foundation for further research of the ZrNiSn based thermoelectric material.

Has the advantages that: compared with the prior art, the technical scheme of the invention has the following remarkable advantages:

1. the ZrNiSn-based half-Heusler is prepared by a process combining vacuum arc melting, high-energy ball milling and SPS in a short time, long-time heat treatment annealing is not needed in the process, the preparation period of the traditional half-Heusler is greatly shortened, and the purity of a sample is improved to the maximum extent.

2. The n-type ZrNiSn-based thermoelectric material with low carrier concentration has the carrier concentration regulated to the optimal range through proper interstitial atoms, and the electrical property of the material is optimized.

3. The crystal structure of the ZrNiSn-based thermoelectric material is changed by interstitial Ru and controlling the content of the interstitial Ru, the interstitial Ru is used as a phonon scattering center, the lattice thermal conductivity of the ZrNiSn-based thermoelectric material is effectively further reduced, and the zT value reaches 1.19 at 919K. The results lay the foundation for the application of the ZrNiSn based thermoelectric material.

Drawings

FIG. 1 shows ZrNiRu_xA powder XRD diffraction pattern and a unit cell parameter change pattern of the Sn thermoelectric material;

FIG. 2 shows ZrNiRu_xTemperature dependent electrical conductivity of Sn thermoelectric materialsA schematic diagram;

FIG. 3 shows ZrNiRu_xA relation schematic diagram of the Seebeck coefficient of the Sn thermoelectric material along with the temperature change;

FIG. 4 shows ZrNiRu at room temperature_xA relation schematic diagram of the change of the Sn thermoelectric material carrier concentration and the mobility along with the Ru content;

FIG. 5 shows ZrNiRu_xThe relation between the total thermal conductivity of the Sn thermoelectric material and the temperature change is shown schematically;

FIG. 6 shows ZrNiRu_xThe relation between the lattice thermal conductivity of the Sn thermoelectric material and the temperature change is shown schematically;

FIG. 7 is ZrNiRu_xAnd the nondimensional thermoelectric figure of merit zT of the Sn thermoelectric material is shown as a relationship graph along with the change of temperature.

Detailed Description

The Ru-gap-filling high-performance ZrNiSn-based thermoelectric material and the method for manufacturing the same according to the present invention will be described in detail with reference to the accompanying drawings.

The invention provides a Ru-interstitial high-performance ZrNiSn-based thermoelectric material, which has a chemical formula of ZrNiRu_xSn, wherein the value range of x is more than or equal to 0 and less than or equal to 0.03.

In addition, the invention also provides a preparation method of the Ru-interstitial high-performance ZrNiSn-based thermoelectric material, which comprises the following steps:

a. according to different x values, Zr, Ni, Ru and Sn metal simple substances (the purity is more than 99.9%) are weighed in a vacuum argon glove box according to a required stoichiometric ratio, the volatilization loss of Sn with a lower melting point in the arc melting period is considered, after a plurality of experimental summaries, 3 wt% of Sn particles are added in advance for samples with different gradient components to compensate the loss, then, the component raw materials are sequentially placed in a copper crucible for purification and melting, and finally, the components are mixed and repeatedly melted for 3-5 times to ensure the uniformity of the alloy components.

b. ZrNiRu prepared by smelting_xAnd putting the Sn ingot (reaction precursor) into a high-energy ball mill, and ball-milling for 10 hours at the rotating speed of 1200r/min to crush the precursor to prepare a powdery sample.

c. Loading the ball-milled powder into a graphite mold, and passing through LABOX-325GH-C1 typeSintering in a spark plasma sintering furnace, heating to 900 deg.C at a rate of 50 deg.C/min, regulating sintering pressure to 50MPa, maintaining at constant pressure for 10min, and cooling to room temperature to obtain compact round-plate-shaped ZrNiRu block_xAnd (3) Sn sample.

Prepared ZrNiRu_xThe powder XRD diffraction pattern and the unit cell parameter change pattern of the Sn thermoelectric material are shown in figure 1, and figure 1 shows that the unit cell parameter of a sample is increased along with the increase of the content of Ru, which indicates that Ru atoms can additionally enter into the tetrahedral gaps of the crystal lattice to stably exist.

ZrNiRu_xThe relation of the electrical conductivity of the Sn thermoelectric material with the temperature change is shown in a figure 2, all samples show semiconductor behavior, the electrical conductivity increases with the increase of the temperature, and the samples are found to have a negative Seebeck coefficient in combination with a figure 3, which indicates that electrons are used as main transport carriers. Undoped samples show lower conductivity at the same temperature, with a slight increase in conductivity at room temperature with increasing Ru concentration, but not much, which can be seen in FIG. 4 for ZrNiRu at room temperature_xThe scatter plot of the Sn carrier concentration n and the mobility μ as a function of Ru content explains that as the Ru concentration increases, the carrier concentration increases and the mobility decreases, so that the change in conductivity at room temperature is insignificant, and as the temperature increases, the carrier concentration increases rapidly, which may be attributed to the provision of electrons by Ru located in the gap, and the bipolar effect occurs at the temperature increase, resulting in an increase in conductivity. ZrNiRu_xThe change of the Seebeck coefficient of the Sn thermoelectric material along with the temperature is shown in a graph 3, and the Seebeck coefficient of a sample is firstly increased and then decreased along with the temperature increase, which is the result of the bipolar effect caused by intrinsic excitation of the temperature increase. At the same temperature, with the increase of the content of Ru, the seebeck coefficient of the material is abnormally increased at x of 0.01 and then becomes smaller, and a possible explanation is that impurity bands are partially introduced into interstitial Ru atoms, the band structure is changed, a small amount of holes are contained at the time of thermal excitation, and further calculation is still needed for confirmation. FIG. 4 shows ZrNiRu at room temperature_xA scatterplot of the carrier concentration n and mobility μ of Sn thermoelectric materials as a function of Ru content, with increasing Ru content, showing that interstitial Ru atoms provide the carrier concentration of the material and mobility decreasesThe electrons increase the carrier concentration and simultaneously act as scattering centers to scatter the electrons, so that the carrier mobility is reduced.

FIG. 5 shows ZrNiRu_xThe relation of the total thermal conductivity of the Sn thermoelectric material along with the temperature change is shown schematically, and the total thermal conductivity is reduced along with the increase of the Ru content under the same temperature. With the same composition, the thermal excitation of intrinsic carriers leads to a bipolar effect with increasing temperature, resulting in an increase in electron thermal conductivity and bipolar thermal conductivity, both of which are the major contributors to thermal conductivity at high temperatures. ZrNiRu_xThe relationship of the lattice thermal conductivity of the Sn thermoelectric material along with the temperature change is shown in FIG. 6, the low lattice thermal conductivity is due to the fact that Ru positioned at the gap position serves as a phonon scattering center to generate strong point defect scattering, and meanwhile, the larger atomic mass of Ru and ball milling enable crystal grains to be refined to cause the enhancement of multi-scale phonon scattering.

By comparison, when x is 0.01, the optimization of electrical properties and the reduction of lattice thermal conductivity lead to high thermoelectric properties, and the thermoelectric figure of merit of the ZrNiSn-based thermoelectric material is as high as 1.19.

The ZrNiSn based thermoelectric material and the method for manufacturing the same according to the present embodiment will be described below with specific examples 1 to 3.

The first embodiment is as follows:

zr, Ni, Ru and Sn are used as raw materials, x is 0 in the example, and the chemical formula is ZrNiRu_xSn, repeatedly smelting the proportioned raw materials for 3 times through a vacuum arc melting instrument for purification, then mixing and repeatedly smelting for 3 times to obtain an alloy ingot (reaction precursor), placing the alloy ingot in a ball milling tank for high-energy ball milling, and carrying out ball milling at the speed of 1200r/min for 10 hours to obtain ball milling powder. The ball-milling powder is filled into a graphite die, and spark plasma sintering is carried out in a vacuum environment, the sintering temperature is 900 ℃, the sintering pressure is 50MPa, and the heat preservation time is 10min, thus obtaining ZrNiRu_xA Sn wafer-like bulk thermoelectric material.

Example two:

this embodiment is substantially the same as the first embodiment, except that x is 0.01 in this embodiment.

Example three:

the embodiment is basically the same as the first embodiment, except that x is 0.02 in this embodiment.

Example four:

the embodiment is basically the same as the first embodiment, except that x is 0.03 in this embodiment.

Claims

1. A high-performance ZrNiSn-based thermoelectric material with Ru interstitial, characterized in that, its chemical formula is ZrNiRu _x Sn, wherein, the value range of x is 0≤x≤0.03.

2 . The high-performance ZrNiSn-based thermoelectric material with Ru interstitials according to claim 1 , wherein the x=0.01 or 0.02 or 0.03. 3 .

3. the preparation method of the high performance ZrNiSn base thermoelectric material of a kind of Ru interstitial as claimed in claim 1 or 2, is characterized in that, its flow process comprises the following steps:

a. Arc smelting: According to the value of x, the metal elements Zr, Ni, Ru and Sn with a purity greater than 99.99% are respectively weighed according to the stoichiometric ratio, and then the raw materials of each component are mixed and smelted to obtain ZrNiRu _x Sn ingot as reaction precursor;

b. High-energy ball milling: put the reaction precursor obtained by arc melting into a high-energy ball mill, so that the alloy ingot is pulverized into powder within 10 hours to obtain a powder sample;

c. SPS sintering: The powder samples after high-energy ball milling were loaded into a graphite mold in an argon gas glove box, and subjected to spark plasma sintering, and then cooled to room temperature to obtain a sheet-like ZrNiRu _x Sn thermoelectric material.

4. the preparation method of a kind of Ru interstitial high-performance ZrNiSn-based thermoelectric material according to claim 3, it is characterized in that, in step a, except that Zr, Ni keep original ratio, for the samples of different value ranges x Additional 2-4wt% Sn particles were added in advance to compensate for the loss. At the same time, the elemental metals Zr, Ni, Ru and Sn were purified and smelted before alloy smelting, and then mixed and smelted repeatedly for 3 to 5 times to make the alloy composition and structure uniform.

5. the preparation method of the high-performance ZrNiSn-based thermoelectric material of a kind of Ru interstitial according to claim 4, it is characterized in that, in step a, except that Zr, Ni keep original ratio, for the samples of different value ranges x Additional 3 wt % Sn particles were preliminarily added to compensate for the loss, followed by mixing and smelting repeated 3 times.

6. the preparation method of a kind of Ru interstitial high-performance ZrNiSn-based thermoelectric material according to claim 3, is characterized in that, in step b, the high-energy ball mill will be equipped with the reaction precursor at the rotating speed of 1200～1500r/min. Ball milling in a ball mill for 10 to 20 hours to make the alloy composition and structure more uniform.

7 . The preparation method of a Ru interstitial high-performance ZrNiSn-based thermoelectric material according to claim 6 , wherein in step b, the high-energy ball mill is ball-milled at a rotational speed of 1200 r/min, and the ball-milling time is 10 h. 8 .

8 . The preparation method of a high-performance ZrNiSn based thermoelectric material with Ru interstitial according to claim 3 , wherein in step c, the temperature of ZrNiRu _x Sn is raised to 850 to 950 ℃ at a rate of 40 to 60° C./min. 9 . ℃, the pressure is adjusted to 50-60 Mpa, and maintained at constant temperature and pressure for 5-15 minutes, and then naturally cooled to room temperature to obtain the Ru-filled high-performance ZrNiSn-based thermoelectric material.

9 . The preparation method of a Ru interstitial high-performance ZrNiSn-based thermoelectric material according to claim 8 , wherein in step c, a heating rate of 50° C./min, a sintering temperature of 900° C., and a sintering temperature of 50 Mpa are performed in step c. 10 . pressure, and kept at constant temperature for 10 min.