Compound of cage compound and method for controlling proportion of phases during preparation

Abstract

The invention discloses a compound of an Eu8GaxGe46-x cage compound and a method for controlling the proportion of each phase during preparation, and the method comprises the following steps: weighing metal elementary substances as synthesis raw materials according to the nominal proportion (Eu: Ga: Ge = 8: x: 46-x, 14.5 < = x < = 16.5); smelting the raw materials in an electric arc furnace; grinding the sample into powder; performing spark plasma sintering (SPS), and for the determined two-phase target proportion during sintering, if the Ga content is larger, namely, the x is larger, the sintering temperature is lower, the pressure is smaller, and the heat preservation time is shorter; if the smaller the Ga content is, the smaller the x is, the higher the sintering temperature is, the larger the pressure intensity is, and the longer the heat preservation time is, when the Ga content is constant, the sintering temperature, the sintering pressure intensity and the heat preservation time form an interactive compensation triangular relation, that is, by reducing any one parameter or any two parameters and then adding the other two parameters or one parameter, the Ga content can be calculated. And the ratio of the alpha phase to the beta phase in the composite material is controlled. According to the invention, the Eu8GaxGe46-x cage compound can be simply and efficiently prepared, and the proportion of each phase in the compound can be controlled.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of material preparation, and relates to a compound of Eu8Ga x Ge 46-x and a method for controlling the proportion of each phase during preparation. BACKGROUND

[0002] Cage compounds are compounds composed of polyhedral cages and guests in the cages. The "cage" is a cage-shaped cavity composed of atoms or molecules, and the cavity can be filled with other atoms or molecules as "guests". Intermetallic cage compounds are widely studied as main candidates for new thermoelectric materials, as they meet the concept of phonon glass-electron crystal (PGEC) proposed by Slack, i.e. the anharmonic vibration of guest atoms in the cage can scatter phonons without affecting the conductivity of the framework, so that the cage compound has high conductivity like a crystal and low thermal conductivity like a glass. Among them, Eu8Ga x Ge 46-x (14.5 ≤ x ≤ 16.5) is the only known intermetallic cage compound with all magnetic elements filled in the cage, and is divided into type I (alpha phase) and type VIII (beta phase) in structure. The paramagnetic-ferromagnetic transition of Eu8Ga 16 Ge 30 (x=16) occurs at about 13 K and 34 K, respectively, which has also attracted some attention in the field of magnetic refrigeration. The research on single-phase Eu8Ga x Ge 46-x is relatively complete, and the synthesis process is relatively mature. Single-phase Eu8Ga x Ge 46-x of the beta phase can be obtained directly by arc furnace smelting; single-phase Eu8Ga x Ge 46-x of the alpha phase can be obtained by annealing the beta phase, or by sintering the beta phase under high temperature and high pressure by SPS. Single-phase materials can eliminate the interference of other phases, which is the basis for understanding the intrinsic properties of materials, and can clearly define the structure-performance relationship, providing pure samples for theoretical modeling. SUMMARY

[0003] The composite material composed of different phases can produce performance that cannot be achieved by single-phase due to the interaction of different phases, and expand the functional boundary. Therefore, the composite material coexisting with the alpha phase and the beta phase of Eu8Ga x Ge 46-x will exhibit obvious advantages in functional performance.

[0004] On one hand, compared with single-phase materials, the two-phase coexisting composite material has two ferromagnetic-paramagnetic transitions, which can broaden the magnetic refrigeration working temperature range and improve the refrigeration capacity (RC) and relative refrigeration capacity (RCP). On the other hand, if the composite material is not a simple mechanical mixture, but an interactive growth of the alpha phase and the beta phase, a large number of micro-disordered regions can be formed in the material, and the resulting nanocrystalline grain boundaries, deformations and dislocations can strongly scatter phonons, reducing the lattice thermal conductivity. Further, the composite material contains various types of "cages", which provide a more diverse local environment for Eu atoms, allowing them to produce more abundant anharmonic vibration modes, and thus scatter more types of phonons. The above two mechanisms are expected to break through the bottleneck of single-phase material thermal conductivity regulation and provide a new path for achieving higher thermoelectric figure of merit ZT.

[0005] At present, Eu8Ga x Ge 46-x The two-phase coexisting composite material of the alpha phase and the beta phase is rarely studied. Therefore, it is urgent to develop a Eu8Ga x Ge 46-x Composite cage compound preparation method, realizing the interactive growth and synergistic regulation of the alpha phase and the beta phase, to further improve the magnetic and thermoelectric properties of the material, and lay the foundation for its application in functional devices.

[0006] The present disclosure proposes a method for preparing a cage compound composite material from a cage compound single-phase material, which can simply and efficiently prepare a Eu8Ga x Ge 46-x Cage compound composite material and control the phase ratio in the composite.

[0007] In the following, a brief overview of the present disclosure will be given in order to provide a basic understanding of certain aspects of the present disclosure. It should be understood that this overview is not an exhaustive overview of the present disclosure. It is not intended to identify key or important parts of the present disclosure nor is it intended to limit the scope of the present disclosure. Its purpose is merely to present some concepts of the present disclosure in a simplified form as a prelude to a more detailed description to be discussed later.

[0008] According to an aspect of the present disclosure, a method for controlling the phase ratio in a Eu8Ga x Ge 46-x Cage compound composite material during preparation is provided, comprising the following steps: Step 1: Calculate and weigh: Calculate the required mass of each element from the nominal ratio of the pre-synthesized cage compound complex (Eu: Ga: Ge = 8: x: 46-x, 14.5 ≤ x ≤ 16.5) and the total mass. According to the calculation result, accurately weigh the high-purity metal elements as the synthesis raw material; Step 2: Arc furnace melting (ARC): Put the weighed raw materials into the arc furnace and melt under argon atmosphere to obtain the sample; Step 3: Grind: Grind the melted sample into powder; Step 4: Spark plasma sintering (SPS): Take an appropriate amount of ground sample and put it into the sintering mold. The chamber of the sintering furnace is pumped to a certain vacuum degree. After setting the required sintering pressure, temperature and time, sintering is carried out; Step 5: Sampling: After sintering, a round sheet of cage compound complex is obtained; In step 4, when performing spark plasma sintering (SPS), for the determined two-phase target ratio, the greater the Ga content, i.e. the greater x, the lower the sintering temperature, the smaller the pressure, and the shorter the holding time. If the Ga content is smaller, i.e. x is smaller, the sintering temperature is higher, the pressure is larger, and the holding time is longer. When the Ga content is constant, the sintering temperature, sintering pressure and holding time form a triangular relationship of mutual compensation, i.e. by reducing any one parameter or any two parameters, and then increasing the other two parameters or one parameter, to control the ratio of α phase and β phase in the composite material.

[0009] Preferably, in step 1, when weighing Eu metal, 3%-5% more Eu is needed to make up for the loss caused during melting.

[0010] Preferably, in step 4, the sintering temperature is 565-595 ℃, the sintering pressure is 30-40 MPa, and the holding time is 3-40 min.

[0011] Preferably, in step 2, open the side extraction valve to extract low vacuum to below 10 Pa, and close the side extraction valve; open the argon cylinder and the filling valve to fill argon, and close the filling valve when the pressure gauge reaches 0; open the side extraction valve again to extract vacuum to below 10 Pa, and close the side extraction valve; then open the plug valve to extract high vacuum to above 10 Pa, and close the plug valve; fill argon to make the pressure in the furnace chamber reach normal pressure, and start melting the sample. Each sample is turned over at least 3-5 times and melted for 4-6 times. -4 Pa above, close the plug valve; fill argon to make the pressure in the furnace chamber reach normal pressure, and start melting the sample. Each sample is turned over at least 3-5 times and melted for 4-6 times.

[0012] Preferably, in step 3, the melted sample is ground to remove the oxide layer on the surface and placed in a mortar. After being knocked and ground into powder.

[0013] Preferably, in step 4, the inner wall of the mold and the upper and lower surfaces of the sample are both covered with graphite paper, the mold is placed in the cavity of the sintering furnace, the cavity door is closed, vacuum is extracted to below 5 Pa, the pressure adjustment button is adjusted to the desired pressure value, the sintering temperature and sintering time required are set, and the sintering start button is turned on to start sintering.

[0014] Preferably, in step 4, when the Ga content is constant, the pressure at the time of sintering is first fixed, and the proportion of different phases is controlled by adjusting the sintering temperature and holding time. When a lower sintering temperature is used, the molar proportion of the alpha phase in the composite material is increased by prolonging the holding time.

[0015] Preferably, in step 5, the graphite diffusion layer on the surface caused by sintering of the graphite paper also needs to be polished off.

[0016] According to another aspect of the present disclosure, there is provided a Eu8Ga x Ge 46-x cage compound composite obtained by the method of the present application.

[0017] Preferably, the molar ratio of the alpha phase and the beta phase in the composite is 0.5:1-1.5:1.

[0018] The scheme of the present disclosure can at least help to achieve one of the following effects: 1. Eu8Ga x Ge 46-x cage compound composite can be simply and efficiently prepared, and the proportion of each phase in the composite can be controlled; 2. According to the specific content of Ga, by adjusting the pressure, temperature and time, the proportion of the alpha phase and the beta phase can be adjusted, so as to realize the control of the proportion of each phase in the composite material and the fine tuning of the material performance; 3. According to the mutual coordination relationship among the sintering temperature, pressure and time, when one parameter is limited, the proportion of the alpha phase and the beta phase in the composite material can be maintained and controlled by adjusting one or two other parameters. BRIEF DESCRIPTION OF DRAWINGS

[0019] The specific content of the present disclosure will be described below with reference to the accompanying drawings, which will help to more easily understand the above and other purposes, features and advantages of the present disclosure. The accompanying drawings are only used to illustrate the principles of the present disclosure. In the drawings, the size and relative position of the units are not necessarily drawn according to the scale.

[0020] Figure 1 X-ray diffraction patterns of the Eu8Ga 15 Ge 31 sample of Example 1 after sequentially undergoing ARC and SPS are shown.

[0021] Figure 2 X-ray diffraction patterns of the Eu8Ga15 Ge 31 The MT and dM / dT-T plots of the sample, where M refers to magnetization and T refers to thermodynamic temperature.

[0022] Figure 3 The appearance of the sample of Example 1 after undergoing SPS is shown.

[0023] Figure 4 Eu8Ga of Example 2 after undergoing SPS is shown. 15.25 Ge 30.75 Refined X-ray diffraction Rietveld structure image of the sample.

[0024] Figure 5 Eu8Ga after SPS in Example 2 15.25 Ge 30.75 The MT and dM / dT-T plots of the sample, where M refers to magnetization and T refers to thermodynamic temperature.

[0025] Figure 6 For the first Eu8Ga in Example 3 after SPS 15.2 Ge 30.8 Refined X-ray diffraction Rietveld structure image of the sample.

[0026] Figure 7 For the second Eu8Ga in Example 3 after SPS 15.2 Ge 30.8 Refined X-ray diffraction Rietveld structure image of the sample.

[0027] Figure 8 For the first Eu8Ga in Example 3 after SPS 15.2 Ge 30.8 The MT and dM / dT-T plots of the sample, where M refers to magnetization and T refers to thermodynamic temperature.

[0028] Figure 9 For the second Eu8Ga in Example 3 after SPS 15.2 Ge 30.8 The MT and dM / dT-T plots of the sample, where M refers to magnetization and T refers to thermodynamic temperature. Detailed Implementation

[0029] Exemplary disclosures of this disclosure will be described below with reference to the accompanying drawings. For clarity and brevity, not all features implementing this disclosure are described in the specification. However, it should be understood that many disclosure-specific decisions can be made in developing any such implementation of this disclosure to achieve the developer’s specific goals, and these decisions may vary depending on the specific disclosure.

[0030] It should also be noted that, in order to avoid obscuring this disclosure with unnecessary details, only features closely related to the solution of this disclosure are shown in the accompanying drawings, while other details that are not closely related to this disclosure are omitted.

[0031] It should be understood that this disclosure is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. Throughout this document, features may be substituted or borrowed between different embodiments where feasible, and one or more features may be omitted in one embodiment. It should be understood that the design methods of this disclosure are exemplary in the embodiments.

[0032] The composite material disclosed herein can be applied in magnetocaloric and thermoelectric materials, through different proportions of α-phase and β-phase Eu8Ga x Ge 46-x The formation of composite materials through interactive growth and interaction can broaden the operating temperature range of magnetocooling and improve the cooling capacity (RC) and relative cooling capacity (RCP); it can break through the bottleneck of single-phase material thermal conductivity control and achieve a higher thermoelectric figure of merit ZT.

[0033] The composite material disclosed herein consists of α-phase and β-phase Eu8Ga in different proportions. x Ge 46-x The composition is (14.5 ≤ x ≤ 16.5), preferably, the molar ratio of α phase to β phase can be 0.5:1-1.5:1, and the preparation method includes the following steps: Step 1: Calculate and weigh: Calculate the required mass of each element based on the nominal ratio of the pre-synthesized cage-like compound (Eu: Ga: Ge = 8: x: 46-x, 14.5 ≤ x ≤ 16.5) and the total mass; accurately weigh the high-purity metallic element as the synthesis raw material according to the calculation results; preferably, the theoretical Eu content ratio is 8, but considering that Eu is very volatile, an additional portion of Eu is added to compensate for the loss caused during the smelting process, preferably an additional 3%-5% Eu; Step 2: Arc Furnace Melting (ARC): Place the weighed raw materials into the arc furnace and melt them under an argon atmosphere to obtain the sample; preferably, first evacuate the furnace, open the bypass valve to evacuate to a low vacuum below 10 Pa, and then close the bypass valve; open the argon cylinder and fill the gas cylinder with argon gas, and close the filling valve when the pressure gauge reaches 0; open the bypass valve again to evacuate to a low vacuum below 10 Pa, and then close the bypass valve; then open the gate valve to evacuate to a high vacuum below 10 Pa. -4 Once the pressure exceeds a certain level (Pa), close the gate valve. Pour argon gas to bring the furnace chamber pressure to atmospheric pressure, then begin melting the samples. Each sample should be turned over at least 3-5 times and melted 4-6 times. Step 3: Grinding: Grind the smelted sample into powder; preferably, grind off the oxide layer on the surface of the smelted sample and place it in a mortar, crush it and grind it into powder. Step 4: Spark Plasma Sintering (SPS): Place an appropriate amount of the ground sample into the sintering mold. Evacuate the chamber of the sintering furnace to a certain vacuum level. Set the required sintering pressure, temperature, and sintering time, and then proceed with sintering. Preferably, the inner wall of the mold and the upper and lower surfaces of the sample are covered with graphite paper. Place the mold into the chamber of the sintering furnace and close the chamber door. Turn on the mechanical pump and evacuate to below 5 Pa. Adjust the pressure adjustment button to the required pressure value, set the required sintering temperature and sintering time, and turn on the sintering start button to begin sintering. The inventors discovered that regardless of the Ga content, higher sintering pressure, higher temperature, and longer sintering time result in a larger proportion of the α phase. However, higher Ga content facilitates phase transformation. In other words, for a given target two-phase ratio, during spark plasma sintering (SPS), the Ga content is negatively correlated with sintering temperature, pressure, and holding time. If the Ga content is higher, i.e., x (14.5 ≤ x ≤ 16.5) is higher, the material's phase transformation rate is faster during sintering. In this case, to form a composite material, it is generally necessary to lower the sintering temperature, reduce the pressure, and shorten the holding time. Conversely, if the Ga content is lower, i.e., x (14.5 ≤ x ≤ 16.5) is lower, the phase transformation rate is faster. 16.5) The smaller the value, the slower the phase transformation rate of the material during sintering. In this case, to achieve the same two-phase ratio as when the Ga content is high, it is generally necessary to increase the sintering temperature, increase the pressure, and increase the holding time. Furthermore, when the Ga content is constant, in order to form a composite material, the inventors discovered that the three main parameters during sintering—sintering temperature, pressure, and time—form an interactively compensating triangular relationship. That is, by decreasing any one or any two parameters and then increasing the other two or one parameter, the ratio of α and β phases in the composite material can be controlled. Because this parameter adjustment can compensate for the energy barrier during sintering, the ratio of different phases in the final composite material can be controlled when a certain parameter is limited. Specifically, the sintering temperature can be, for example, 565-595 ℃, the sintering pressure can be 30-40 MPa, and the holding time can be 3-40 minutes. In particular, for ease of adjustment and control, the pressure during sintering can generally be fixed, and the proportion of different phases can be controlled by adjusting the sintering temperature and holding time. For example, in the case of Example 3 below, when both use a lower sintering temperature, the molar proportion of the α phase in the composite material can be increased by extending the holding time. Compared with the two, for the case of a lower sintering temperature, the holding time can be further increased to increase the molar proportion of the α phase in the composite material.

[0034] Step 5: Sampling: After sintering, a circular cage-like compound composite is obtained. The sample is taken out. Preferably, the graphite diffusion layer caused by the sintering of graphite paper is polished off to obtain a circular cage-like compound composite. Preferably, the molar ratio of α phase to β phase in the composite can be 0.5:1-1.5:1.

[0035] The present invention will be further described below with reference to specific embodiments.

[0036] Example 1: To prepare a chemically nominally compounded Eu8Ga 15 Ge 31 For the sample (x=15), high-purity elemental metals Eu (99.99%), Ga (99.99%), and Ge (99.999%) were weighed in a ratio of 8.4:15:31. Since Eu is highly volatile, an additional 5% Eu was added to compensate for losses during the smelting process. Calculations showed 8 * 1.05 = 8.4, therefore the molar ratio of Eu was 8.4. The weighed elemental metals were placed in a vacuum arc furnace. The side-extraction valve was opened, and a vacuum was evacuated to below 10 Pa. The side-extraction valve was then closed. Argon gas was introduced until the pressure gauge reading was 0, and the argon gas valve was closed. The side-extraction valve was opened again, and a vacuum was evacuated to below 10 Pa. The side-extraction valve was then closed. Finally, the gate valve was opened, and a high vacuum was evacuated to 10 Pa. -4 Pa, close the gate valve. Pour argon gas to bring the furnace pressure to atmospheric pressure, then begin melting. To ensure more thorough and uniform melting, continuously shake the ignition cone during melting. After each melting cycle, flip the sample and continue melting, flipping each sample 3 times and melting 4 times. After melting, wait for the furnace to cool down. Once cooled, remove the alloy ingot. Use sandpaper to remove the oxide layer from the surface of the alloy ingot, then grind it into powder using a mortar and pestle. Characterize the structure of the powder sample using X-ray diffraction (XRD). The resulting XRD pattern is shown below. Figure 1 As shown in (a), the obtained sample is in the β phase.

[0037] A portion of the powder sample was placed in a mold with a diameter of 12.7 mm and subjected to spark plasma sintering. The sintering conditions were: sintering temperature of 595 ℃, sintering pressure of 30 MPa, and holding time of 20 min. After the holding time was completed, the sample was cooled by depressurization, i.e., the sintering pressure was reduced to 0. After the sample had cooled completely, it was removed. After cleaning the graphite and other impurities from the sample surface, the structure of the sample was characterized using an X-ray diffractometer. The obtained X-ray diffraction pattern is shown below. Figure 1 As shown in (b), the resulting composite material consists of α and β phases. Figure 1 (c) also shows the standard spectra of the α and β phases. It can be seen that... Figure 1 The diffraction peaks in (a) are all diffraction peaks of the β phase. Figure 1(b) shows diffraction peaks of both the β and α phases, with a molar ratio of 1.2:1 between the α and β phases. This indicates that spark plasma sintering (SPS) technology can transform a single-phase sample into a composite sample with two coexisting phases. A small piece of the SPS-sintered sample was taken and its magnetization was measured using a Power Property Measurement System (PPMS). The measurement conditions were: an external magnetic field of 100 Oe, field cooling, and a temperature range of 2-60 K. The obtained magnetization-temperature (MT) curve and its derivative (dM / dT-T) curve are shown below. Figure 2 As shown in (a) and (b). From Figure 2 As can be seen in (a), the magnetization M experienced two sharp increases as the temperature decreased, indicating that two paramagnetic-ferromagnetic transitions occurred. Figure 2 (b) The temperature at which |dM / dT| reaches its maximum value is defined as the Curie temperature (T). C The peak at 33.9 K corresponds to the magnetic transition of the β phase, and the peak at 10.1 K corresponds to the magnetic transition of the α phase, confirming that the control of the technical parameters of the discharge plasma sintering in the present invention can transform a single-phase sample into a composite sample with a controllable ratio of two phases. Figure 3 The image shows the appearance of the sample after SPS sintering. It can be seen that the sample is very regular and dense, and the measured density is 96% of the theoretical density.

[0038] Example 2: To prepare a chemically nominally compounded Eu8Ga 15.25 Ge 30.75 For the sample (x=15.25), high-purity elemental metals Eu (99.99%), Ga (99.99%), and Ge (99.999%) were weighed in a ratio of 8.4:15.25:30.75. Since Eu is highly volatile, an additional 5% Eu was added to compensate for losses during the smelting process. Next, electric arc furnace smelting was performed, with the specific operating steps identical to Example 1, and will not be repeated here. Then, an appropriate amount of powder was placed into a 12.7 mm diameter mold for spark plasma sintering. Because the Ga content in Example 2 was higher than that in Example 1, the sintering conditions were: a sintering temperature of 575 °C, lower than that in Example 1; a sintering pressure of 30 MPa, the same as in Example 1; and a holding time of 25 min, longer than that in Example 1. Other experimental operations were the same as in Example 1 and will not be described further. The Rietveld-refined X-ray diffraction pattern is shown below. Figure 4As shown in the figure, the black × represents the experimentally measured result, the red line is the calculated result, the gray line at the bottom is the difference between the experimental and calculated results, and the blue and pink vertical lines are the positions of the Bragg diffraction peaks of the β phase and α phase, respectively. The sample contains both α and β phases with a molar ratio of 1.25:1. Compared to Example 1, the molar ratio of the α phase is higher, mainly because the Ga content in Example 2 is higher than that in Example 1. Under the same pressure, a lower temperature and a longer holding time were achieved, but a composite with a higher molar ratio of the α phase was still obtained. The MT test results and dM / dT-T curves are shown in the figures below. Figure 5 As shown in (a) and (b), the test conditions were the same as in Example 1. With decreasing temperature, the magnetization underwent two sharp increases, indicating two ferromagnetic transitions. The two maxima of |dM / dT| are located at approximately 12.1 and 31.8 K, respectively, corresponding to the T values ​​of the α and β phases. C .

[0039] Example 3: To prepare a chemically nominally compounded Eu8Ga 15.2 Ge 30.8 For the sample, high-purity elemental metals Eu (99.99%), Ga (99.99%), and Ge (99.999%) were weighed at a ratio of 8.4:15.2:30.8. To compensate for the volatilization loss of Eu during the smelting process, an additional 5% of Eu was added. The sample was then smelted in an electric arc furnace, with the specific operating steps being the same as in Examples 1 and 2, and will not be repeated here. Two portions of the powder were then subjected to high-temperature, high-pressure discharge plasma sintering, and for easy distinction, they were designated Eu8Ga. 15.2 Ge 30.8 -1、Eu8Ga 15.2 Ge 30.8 -2. Sintering was still performed using a 12.7 mm diameter mold. Eu8Ga 15.2 Ge 30.8 The sintering conditions for Eu8Ga were: sintering temperature 575 ℃, sintering pressure 30 MPa, and holding time 3 min; 15.2 Ge 30.8 The sintering conditions for -2 are: sintering temperature of 565 ℃, sintering pressure of 30 MPa, and holding time of 40 min. To obtain a consistent density, compared to Eu8Ga... 15.2 Ge 30.8 -1, Eu8Ga 15.2 Ge 30.8-2 used a lower sintering temperature, but with a correspondingly longer holding time. Other steps were the same as in Examples 1 and 2. X-ray diffraction analysis of the sintered samples showed that both consisted of two phases, α and β. To determine the ratio of the two phases, the Rietveld method was used to refine the structure of the two-phase coexisting sample, with results as shown below. Figure 6 and Figure 7 As shown. Eu8Ga 15.2 Ge 30.8 The molar ratio of the α phase to the β phase in Eu8Ga is 0.95:1. 15.2 Ge 30.8 The molar ratio of the α phase to the β phase in -2 is 1.2:1, indicating that under the same pressure, when both phases are sintered at a lower temperature (Eu8Ga), the molar ratio of the α phase to the β phase is 1.2:1. 15.2 Ge 30.8 The sintering temperature of Eu8Ga is 575 ℃. 15.2 Ge 30.8 The sintering temperature of -2 is 565℃. The molar proportion of the α phase in the composite material can be increased by increasing the holding time, and compared to Eu8Ga... 15.2 Ge 30.8 -1, Eu8Ga 15.2 Ge 30.8 -2 uses a lower sintering temperature (Eu8Ga) 15.2 Ge 30.8 The sintering temperature of Eu8Ga is 575℃. 15.2 Ge 30.8 The sintering temperature of sample -2 is 565 °C, so the holding time needs to be further increased to a longer 40 min to improve the molar proportion of the α phase in the composite material. In addition, MT tests were performed on the samples under the same conditions as in Examples 1 and 2. The MT and dM / dT-T curves of the two samples are shown below. Figure 8 and 9 As shown, both samples exhibit two Tc values, indicating the coexistence of two phases. The lower temperatures of 11.6 and 11.9 K correspond to the α phase, while the higher temperatures of 32.0 and 31.1 K correspond to the β phase. Furthermore, the proportions of the two phases differ between the two samples. (Eu8Ga) 15.2 Ge 30.8 The α phase proportion of -1 is less than that of Eu8Ga 15.2 Ge 30.8 -2, consistent with the XRD refinement results. This indicates that spark plasma sintering technology can transform a single-phase sample into a two-phase composite sample, and the proportion of the two phases can be adjusted by changing the sintering conditions.

[0040] This embodiment describes the preparation of Eu8Ga. x Ge 46-xThis invention provides a feasible solution for controlling the proportion of each phase in a cage-like compound composite material. Based on the specific Ga content, the ratio of α and β phases can be adjusted by regulating pressure, temperature, and time, thereby controlling the proportion of each phase in the composite material and fine-tuning its properties. Furthermore, for materials with specific Ga content, sintering temperature, pressure, and time form an interactively compensating triangular relationship. That is, the ratio of α and β phases in the composite material can be controlled by decreasing any one or two parameters and then increasing the other two or one parameter. Generally, for easier adjustment and control, the molar proportion of the α phase in the composite material can be increased by fixing the sintering pressure, decreasing the sintering temperature, and then increasing the holding time. This invention offers a simple and efficient method for preparing cage-like compound composite materials.

[0041] The present disclosure has been described above with reference to specific implementation schemes through simulation analysis and design methods. However, those skilled in the art should understand that these descriptions are exemplary and are not intended to limit the scope of protection of the present disclosure.

[0042] Those skilled in the art can make various modifications and alterations to this disclosure in accordance with the spirit and principles of this disclosure, and such modifications and alterations are also within the scope of this disclosure.

Claims

1. A method for controlling the preparation of Eu8Ga x Ge 46-x A method for determining the phase proportions in a cage-like compound complex, comprising the following steps: Step 1: Calculate and weigh: Calculate the required mass of each element based on the nominal ratio of the pre-synthesized cage-like compound complex (Eu: Ga: Ge = 8:x: 46-x, 14.5 ≤ x ≤ 16.5) and the total mass; accurately weigh the high-purity metallic element as the synthesis raw material according to the calculation results; Step 2: Arc Furnace Melting (ARC): The weighed raw materials are placed into an arc furnace and melted under an argon atmosphere to obtain the sample; Step 3: Grinding: Grinding the sample obtained from melting into powder; Step 4: Spark plasma sintering (SPS): Take an appropriate amount of the ground sample and put it into the sintering mold. Evacuate the chamber of the sintering furnace to a certain degree of vacuum. Set the required pressure, temperature and time for sintering and then carry out sintering. Step 5: Sampling: After sintering, a circular cage-like compound composite is obtained; The key feature is that, in step 4, during spark plasma sintering (SPS), for a given target ratio of two phases, if the Ga content is higher (i.e., x is higher), the sintering temperature is lower, the pressure is lower, and the holding time is shorter; if the Ga content is lower (i.e., x is lower), the sintering temperature is higher, the pressure is higher, and the holding time is longer. When the Ga content is constant, the sintering temperature, sintering pressure, and holding time form an interactively compensating triangular relationship. That is, by reducing any one or any two parameters and then increasing the other two or one parameter, the ratio of α phase and β phase in the composite material can be controlled.

2. The method according to claim 1, characterized in that: In step 1, when weighing Eu metal, an additional 3%-5% Eu needs to be added to compensate for the losses caused during the smelting process.

3. The method according to claim 1, characterized in that: Step 4: sintering temperature is 565-595 ℃, sintering pressure is 30-40 MPa, and holding time is 3-40 min.

4. The method according to claim 1, characterized in that: In step 2, open the bypass valve to evacuate to a low vacuum below 10 Pa, then close the bypass valve; open the argon cylinder and fill it with argon gas, and close the filling valve when the pressure gauge reaches 0; open the bypass valve again to evacuate to a low vacuum below 10 Pa, then close the bypass valve; next, open the gate valve to evacuate to a high vacuum below 10 Pa. -4 Once the pressure is above Pa, close the slide gate valve; purge the furnace chamber with argon gas to bring the pressure to atmospheric pressure, and begin melting the samples. Each sample should be turned over at least 3-5 times and melted 4-6 times.

5. The method according to claim 1, characterized in that: In step 3, the oxide layer on the surface of the smelted sample is ground off and placed in a mortar, then crushed and ground into powder.

6. The method according to claim 1, characterized in that: In step 4, the inner wall of the mold and the top and bottom surfaces of the sample are covered with graphite paper. The mold is placed into the cavity of the sintering furnace and the cavity door is closed. The vacuum is evacuated to below 5 Pa. The pressure adjustment button is adjusted to the required pressure value. The required sintering temperature and sintering time are set, and the sintering start button is turned on to start sintering.

7. The method according to claim 1, characterized in that: In step 4, when the Ga content is constant, the pressure during sintering is first fixed, and the proportion of different phases is controlled by adjusting the sintering temperature and holding time. When a lower sintering temperature is used, the molar proportion of the α phase in the composite material is increased by extending the holding time.

8. The method according to claim 6, characterized in that: In step 5, it is also necessary to grind off the graphite diffusion layer on the surface caused by the sintering of graphite paper.

9. An Eu8Ga obtained by any one of claims 1-8 x Ge 46-x A complex of cage-like compounds.

10. The complex according to claim 9, characterized in that: The molar ratio of α phase to β phase in the composite is 0.5:1 to 1.5:1.

Images