Heat-insulating demagnetizing refrigeration material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of heat insulation and demagnetization refrigeration, in particular to a heat insulation and demagnetization refrigeration material and a preparation method and application thereof. Wherein the heat insulation and demagnetization refrigeration material is an Eu2ZnGe2OS6 crystal. The heat insulation demagnetization refrigeration material is an Eu2ZnGe2OS6 crystal and has relatively small magnetic anisotropy, and a long-range magnetic orderliness phenomenon is not observed at 1.8 K or above. Compared with an existing traditional magnetic refrigeration material, when the magnetic field is adiabatically reduced from 7T to 0T, the material shows the maximum negative magnetic entropy difference as high as 43.11 J * kg <-1 > * K <-1 >, and has a wide development prospect in adiabatic demagnetizing refrigeration application in a 2-16K temperature zone and a sub-Kelvin temperature zone.

Description

Technical Field

[0001] The present application relates to the field of adiabatic demagnetization refrigeration technology, and in particular to an adiabatic demagnetization refrigeration material and a preparation method and application thereof. Background Art

[0002] 3 He is a key strategic resource for medical diagnosis, military exploration and cutting-edge scientific research. It plays an irreplaceable role in the subkelvin temperature range (<1K) and high-sensitivity radiation detection. However, this scarce resource, which can only be obtained through tritium decay in nuclear weapons or reactors, is facing a serious supply crisis. With the reduction of nuclear facilities worldwide, the future 3 The supply situation of He will become more severe. Especially in the research of condensed matter physics, 3 He refrigerants are crucial for achieving sub-Kelvin temperatures because quantum effects are only significant at low temperatures where thermal fluctuations are suppressed. 3 He's, low-temperature technology based on adiabatic demagnetization refrigeration materials is imminent. Summary of the Invention

[0003] In view of the above-mentioned deficiencies in the prior art, the purpose of this application is to provide an adiabatic demagnetizing refrigeration material and its preparation method and application, in order to solve the problem that the prior art lacks a 3 The problem of He adiabatic demagnetization refrigeration materials.

[0004] The technical solution of this application is as follows:

[0005] In a first aspect of the present application, an adiabatic demagnetization refrigeration material is provided, wherein the adiabatic demagnetization refrigeration material is Eu2ZnGe2OS6 crystal.

[0006] Optionally, the Eu2ZnGe2OS6 crystal belongs to the tetragonal system and has a space group of P-421m.

[0007] Optionally, the Eu in the Eu2ZnGe2OS6 crystal 2+ The ions have a Shastry-Sutherland lattice.

[0008] Optionally, the unit cell parameters of the Eu2ZnGe2OS6 crystal are α=90°, β=90°, γ=90°,

[0009] In a second aspect of the present application, a method for preparing the thermal insulation demagnetization refrigeration material according to the first aspect of the present application is provided, wherein the preparation method is a flux method.

[0010] Optionally, the preparation method comprises the steps of:

[0011] Mixing a raw material of a corresponding compound containing europium, a raw material of a corresponding compound containing zinc, and a raw material of a corresponding compound containing germanium with a flux and grinding the mixture to obtain a powder;

[0012] The mixture powder is sintered under vacuum conditions to obtain the thermal insulation demagnetization refrigeration material.

[0013] Optionally, the molar ratio of europium, zinc, and germanium in the corresponding compound raw material containing europium, the corresponding compound raw material containing zinc, and the corresponding compound raw material containing germanium is 0.6-10:0.4-6.5:0.3-7;

[0014] The mass ratio of the flux to the mixture powder is 0.5-7:1.

[0015] Optionally, the sintering step includes:

[0016] Keep the temperature at 850-1200℃ for 1-6 days, then cool to 500-800℃ at a rate of 0.2-50℃ / h, and finally cool naturally to room temperature.

[0017] The third aspect of the present application provides a use of the thermal insulation demagnetization refrigeration material of the first aspect of the present application in the preparation of refrigeration equipment.

[0018] Optionally, the refrigeration temperature range of the refrigeration equipment is 2-16 Kelvin or sub-Kelvin temperature range.

[0019] Beneficial effects of this application:

[0020] (1) The adiabatic demagnetization refrigeration material in this application is Eu2ZnGe2OS6 crystal. The magnetic test results show that the crystal material has a small magnetic anisotropy and no long-range magnetic ordering phenomenon is observed above 1.8K. Compared with existing traditional magnetic refrigeration materials, when the magnetic field is adiabatically reduced from 7T to 0T, the material exhibits a maximum negative magnetic entropy difference of up to 43.11J·kg-1·K-1. Its excellent magnetocaloric properties indicate that Eu2ZnGe2OS6 crystal has broad development prospects in adiabatic demagnetization refrigeration applications in the 2-16K temperature range and sub-Kelvin temperature range.

[0021] (2) This application uses an improved flux method to grow Eu2ZnGe2OS6 crystals, which has the advantages of easy acquisition of millimeter-scale single crystals, simple operation, and high safety. The Eu2ZnGe2OS6 crystals produced are millimeter-scale single crystals and have the advantages of stable physical and chemical properties, good mechanical properties, low deliquescent properties, and easy storage, which provide significant advantages for subsequent processing and practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments.

[0023] Figure 1 Eu in the Eu2ZnGe2OS6 crystal provided in the embodiment of this application 2+ Schematic diagram of ionic structure;

[0024] Figure 2 Flow chart of the method for preparing the adiabatic demagnetizing refrigeration material provided in an embodiment of the present application;

[0025] Figure 3 A flow chart of another method for preparing an adiabatic demagnetizing refrigeration material provided in an embodiment of the present application;

[0026] Figure 4 A physical picture of the Eu2ZnGe2OS6 crystal provided in the examples of this application;

[0027] Figure 5 A curve showing the change of the isothermal magnetization intensity of the adiabatic demagnetization refrigeration crystal material provided in an embodiment of the present application with the magnetic field;

[0028] Figure 6 This is a curve showing how the negative magnetic entropy difference of the adiabatic demagnetization refrigeration crystal material provided in the embodiment of the present application changes with temperature under different magnetic fields. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings and embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application. In the absence of conflict, the features in the following embodiments and embodiments can be combined with each other.

[0030] It should be noted that if there are descriptions involving "first", "second", etc. in the implementation of this application, the descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance and implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0031] Adiabatic Demagnetization Refrigeration (ADR) technology has become an alternative due to its advantages of completely avoiding the use of helium resources, being environmentally friendly, and being easy to operate. 3 A key technology for He cooling. Its working principle is based on the magnetocaloric effect of magnetic materials. Under the action of an external magnetic field, the spin system of the material is ordered (entropy decreases). Then, under adiabatic conditions, the magnetic field is removed and the self-selected system absorbs lattice heat by re-disordering, thereby achieving a cooling effect. However, paramagnetic salts (such as Ce2Mg3(NO3) 12 Traditional materials for ADR (adiabatic demagnetization) in the sub-Kelvin temperature range, such as Mn(NH4)2(SO4)2·6H2O, have limitations. Due to the spatial separation of magnetic ions from water molecules, their magnetic ion density is low, resulting in insufficient volumetric cooling capacity. This structural constraint severely restricts the practical application of ADR technology in the sub-Kelvin temperature range. Therefore, the development of novel adiabatic demagnetization refrigeration materials with high magnetocaloric effect has become a key research direction in ultra-low temperature refrigeration technology.

[0032] In recent years, geometrically frustrated quantum magnets (such as quantum spin liquids and spin supersolids) have emerged as promising candidates for ADR (Atomic Refrigerant Dissociation) (ADR) due to their ability to suppress magnetic order through strong quantum fluctuations. Recent research has focused on triangular lattice transition metal or rare earth magnets. These materials have attracted considerable attention due to their exceptional ADR performance. Representative materials include KBaYb(BO3)2 and KBaGd(BO3)2, which achieve cooling temperatures as low as 40mK and 120mK, respectively, after adiabatic demagnetization at an initial temperature of 2K and a 5T magnetic field. Similarly, the spin supersolid Na2BaCo(PO4)2 exhibits remarkable cooling performance near its quantum critical point, reaching a cooling temperature of 94mK after adiabatic demagnetization at an initial temperature of 2K and a 4T magnetic field. Given the outstanding performance of frustrated triangular lattice magnets in subkelvin refrigeration, exploring different quantum frustrated magnets as novel ADR refrigeration materials is of great significance.

[0033] Shastry-Sutherland lattice (SSL) materials are a type of geometrically frustrated lattice that is less studied. They have research value in the fields of quantum phenomenon detection and magnetic refrigeration. Through the synergistic effect of geometric frustration and weak exchange of rare earth ions, materials with SSL have the potential to suppress the premature appearance of magnetic order while maintaining a high magnetic ion density, thereby potentially achieving lower refrigeration temperatures and better refrigeration efficiency in the sub-Kelvin temperature range. 3+ Significant progress has been made in the research of base materials, such as Gd3Ga5O 12 , Gd(HCOO)3 and Gd(OH)F2. By using Gd 3+The large ground state spin (J = S = 7 / 2, L = 0) and magnetic isotropy of the ions lead to excellent magnetocaloric effect at low temperature. 2+ ions and Gd 3+ ions have the same ground state spin and magnetic isotropy, and divalent europium-based compounds have also attracted attention in the exploration of low-temperature magnetocaloric materials. 2+ Research on the magnetocaloric effect of base materials is limited, but existing studies have shown that it has great application potential at low temperatures. For example, Eu2B2O5 and EuB2O4 achieved magnetic entropy changes of 13.7J·kg-1·K-1 and 19.4J·kg-1·K-1 at 2.7K and 1.3K respectively under a magnetic field change of H=0-1T. These studies show that Eu 2+ Base materials may have advantages over Gd 3+ Excellent magnetic refrigeration performance of based compounds.

[0034] Based on this, see Figure 1 , an embodiment of the present application provides an adiabatic demagnetization refrigeration material, specifically Eu2ZnGe2OS6 crystal.

[0035] In some embodiments, the Eu2ZnGe2OS6 crystal belongs to the tetragonal system with a space group of P-421m.

[0036] In some embodiments, Eu in the Eu2ZnGe2OS6 crystal 2+ The ions have a Shastry-Sutherland lattice.

[0037] In some embodiments, the unit cell parameters of the Eu2ZnGe2OS6 crystal are α=90°, β=90°, γ=90°,

[0038] Magnetic testing results indicate that the Eu2ZnGe2OS6 crystal material exhibits minimal magnetic anisotropy and no long-range magnetic ordering above 1.8K. Compared to existing conventional magnetic cooling materials, the material exhibits a maximum negative magnetic entropy difference of 43.11 J·kg-1·K-1 when the magnetic field is adiabatically reduced from 7T to 0T. This suggests promising applications in adiabatic demagnetization refrigeration in the 2-16K and sub-Kelvin temperature ranges.

[0039] An embodiment of the present application further provides a method for preparing the adiabatic demagnetizing refrigeration material as described above, wherein the method for preparing the adiabatic demagnetizing refrigeration material is a flux method.

[0040] In some embodiments, see Figure 2 The preparation method of the adiabatic demagnetization refrigeration material comprises the following steps:

[0041] S1. Mixing a raw material of a corresponding compound containing europium, a raw material of a corresponding compound containing zinc, and a raw material of a corresponding compound containing germanium with a flux and grinding the mixture to obtain a mixture powder.

[0042] Wherein, the corresponding compound raw material containing europium (Eu) can be a compound powder of Eu, such as at least one of the chloride, oxide, sulfide, fluoride, carbonate, and hydroxide of Eu. The corresponding compound raw material containing zinc (Zn) can be a compound powder of Zn, such as at least one of the chloride, oxide, sulfide, fluoride, carbonate, and hydroxide of Zn. The corresponding compound raw material containing germanium (Ge) can be a compound powder of Ge, such as at least one of the chloride, oxide, sulfide, fluoride, carbonate, and hydroxide of Ge. It should be noted that the compound raw material can include any two of Eu, Zn, and Ge at the same time, or include three kinds of Eu, Zn, and Ge. The flux includes at least one of CsCl, KCl, NaCl, ZnCl2, MgCl2, PbBr2, KBr, CsI, KI, NaF, CaF2, LiF, and KF.

[0043] In some embodiments, the molar ratio of europium, zinc, and germanium in the corresponding compound raw materials containing europium, the corresponding compound raw materials containing zinc, and the corresponding compound raw materials containing germanium is 0.6-10:0.4-6.5:0.3-7. Alternatively, the molar ratio of europium, zinc, and germanium in the mixture powder is 0.6-10:0.4-6.5:0.3-7.

[0044] In some embodiments, the mass ratio of flux to mixture powder is 0.5-7:1, for example, the mass ratio of flux to mixture powder is 0.5:1, 2.7:1, 6.8:1 or 7:1.

[0045] S2. Sintering the mixture powder under vacuum conditions to obtain an adiabatic demagnetizing refrigeration material.

[0046] In some embodiments, the sintering step includes: holding at 850-1200° C. for 1-6 days, then cooling to 500-800° C. at a rate of 0.2-50° C. / h, and finally cooling naturally to room temperature. For example, the holding temperature may be 850° C., 860° C., 870° C., 880° C., 890° C., 900° C., 910° C., 920° C., 930° C., 940° C., 950° C., 960° C., 970° C., 980° C., 990° C., 1000° C., 1100° C., or 1200° C., and the holding time may be 1 day, 36 hours, 2 days, 60 hours, 3 days, 84 hours, 4 days, 5 days, or 6 days. The cooling rate may be 0.2° C. / h, 5° C. / h, 10° C. / h, 20° C. / h, 30° C. / h, 40° C. / h, or 50° C. / h. The cooling temperature can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or 800°C. At a temperature of 850-1200°C, the reactants form a liquid phase solvent, which increases their solubility in the flux. After 1-6 days of constant temperature growth, in the subsequent cooling treatment, as the temperature decreases, the supersaturation of the reactants is adjusted, causing crystal precipitation. Finally, Eu2ZnGe2OS6 crystals are obtained through natural cooling.

[0047] In some embodiments, the specific steps of sintering under vacuum conditions are: filling the mixture powder into a quartz tube and vacuum-sealing the tube to obtain a mixture reaction vacuum quartz tube; placing the mixture reaction vacuum quartz tube in a high-temperature heating furnace and sintering the mixture using the sintering steps described above. Preferably, the quartz tube has a thickness of 1-1.5 mm, an outer diameter of 10-20 mm, and a height of 200-250 mm. This ensures that during the high-temperature reaction process, the reaction area within the tube has a uniform temperature distribution and rapid heat transfer.

[0048] In some embodiments, the method for preparing the adiabatic demagnetization refrigeration material further comprises the steps of:

[0049] S3. The sintered product is cleaned. Specifically, the cleaning process involves soaking the sintered product in a cleaning solution for 1-24 hours to dissolve residual flux and generated impurities (such as KI). The cleaning solution can be ultrapure water or deionized water.

[0050] In some embodiments, see Figure 3 The preparation method of the adiabatic demagnetization refrigeration material comprises the following steps:

[0051] S1. Mixing a raw material of a corresponding compound containing europium, a raw material of a corresponding compound containing zinc, and a raw material of a corresponding compound containing germanium with a flux and grinding the mixture to obtain a mixture powder.

[0052] S2. Filling the mixture powder into a quartz tube and performing vacuum sealing treatment to obtain a mixture reaction vacuum quartz tube.

[0053] S3, placing the mixture reaction vacuum quartz tube in a high-temperature heating furnace for sintering treatment.

[0054] S4. Cleaning the sintered product to obtain an adiabatic demagnetizing refrigeration material.

[0055] The embodiment of the present application also provides a use of the above-mentioned thermal insulation demagnetization refrigeration material in the preparation of refrigeration equipment.

[0056] In some embodiments, the refrigeration temperature range of the refrigeration device is 2-16 Kelvin or sub-Kelvin temperature range.

[0057] The following is further described with reference to specific examples.

[0058] Example 1

[0059] Eu2O3 powder, ZnS powder, and GeS powder were mixed in a molar ratio of 1:1:2.6, and CsI powder was added (the molar ratio of CsI powder to the mixed powder was 2:1), mixed evenly, and ground to obtain a mixture powder;

[0060] The mixture powder was filled into a quartz tube (thickness 1 mm, outer diameter 10 mm, height 200 mm) and vacuum sealed to obtain a mixture reaction vacuum quartz tube;

[0061] The mixture reaction vacuum quartz tube was placed in a high temperature heating furnace and sintered at 950℃ for 2 days, then cooled to 600℃ at a rate of 2℃ / h, and then naturally cooled to room temperature;

[0062] The product cooled to room temperature was taken out from the quartz tube and immersed in ultrapure water for 1 hour to obtain Eu2ZnGe2OS6 crystals.

[0063] Test Example 1

[0064] The structure of the Eu2ZnGe2OS6 crystal prepared in Example 1 was analyzed. The test conditions were: the test instrument was a Bruker D8VENTURE single crystal diffractometer, a molybdenum target, a Kα radiation source (wavelength = 0.07107 nm), the test temperature was 300K, and the structure was analyzed by Olex2 software. The obtained crystallographic data are shown in Table 1. The crystal structure is shown in Figure 1 As shown, the crystal Figure 3 shown.

[0065] Table 1 Eu2ZnGe2OS6 crystal data parameters

[0066]

[0067]

[0068] Test Example 2

[0069] The performance of the Eu2ZnGe2OS6 crystal prepared in Example 1 was evaluated, and the specific steps included:

[0070] The magnetic properties of the crystal sample prepared in Example X were characterized using a comprehensive physical property measurement system (PPMS). The single crystal sample was fixed on a quartz rod in different directions using GE varnish, and the crystal anisotropy magnetization data was measured. In a varying magnetic field, isothermal magnetic anisotropy measurements were performed at intervals of 2K from 2K to 16K, with a magnetic field range of 0T to 7T. Figure 5 As shown. The test data shows that the magnetization curve shows nonlinear characteristics regardless of whether the magnetic field direction is parallel or perpendicular to the crystal c-axis, and also exhibits weak magnetic anisotropy. In order to further evaluate the magnetocaloric effect performance of the material, the magnetic entropy change value under different magnetic field conditions was calculated, as shown in the figure below. Figure 6 It is particularly noteworthy that when the magnetic field is adiabatically reduced from 7 T to 0 T, the system exhibits a maximum negative magnetic entropy difference of up to 43.11 J·kg-1·K-1.

[0071] In summary, the adiabatic demagnetization refrigeration material in this application is Eu2ZnGe2OS6 crystal. Magnetic test results show that this crystalline material has a small magnetic anisotropy and no long-range magnetic ordering phenomenon is observed above 1.8K. Compared with existing traditional magnetic refrigeration materials, when the magnetic field is adiabatically reduced from 7T to 0T, this material exhibits a maximum negative magnetic entropy difference of up to 43.11J·kg-1·K-1, which has broad development prospects in adiabatic demagnetization refrigeration applications in the 2-16K temperature range and sub-Kelvin temperature range.

[0072] It should be understood that the application of this application is not limited to the above examples. For ordinary technicians in this field, they can make improvements or changes based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

Claims

1. A heat-insulating demagnetizing refrigeration material, characterized in that: The adiabatic demagnetization refrigeration material is Eu2ZnGe2OS6 crystal.

2. The adiabatic demagnetizing refrigeration material according to claim 1, characterized in that: The Eu2ZnGe2OS6 crystal belongs to the tetragonal system and has a space group of P-421m.

3. The adiabatic demagnetizing refrigeration material according to claim 1, characterized in that: Eu in the Eu2ZnGe2OS6 crystal 2 + The ions have a Shastry-Sutherland lattice.

4. The adiabatic demagnetizing refrigeration material according to claim 1, characterized in that: The unit cell parameters of the Eu2ZnGe2OS6 crystal are α=90°, β=90°, γ=90°, 5. A method for preparing the adiabatic demagnetizing refrigeration material according to any one of claims 1 to 4, characterized in that: The preparation method is a flux method.

6. The method for preparing the adiabatic demagnetizing refrigeration material according to claim 5, characterized in that: The preparation method comprises the steps of: Mixing a raw material of a corresponding compound containing europium, a raw material of a corresponding compound containing zinc, and a raw material of a corresponding compound containing germanium with a flux and grinding the mixture to obtain a powder; The mixture powder is sintered under vacuum conditions to obtain the thermal insulation demagnetization refrigeration material.

7. The method for preparing the adiabatic demagnetizing refrigeration material according to claim 6, characterized in that: The molar ratio of europium, zinc and germanium in the corresponding compound raw material containing europium, the corresponding compound raw material containing zinc and the corresponding compound raw material containing germanium is 0.6-10:0.4-6.5:0.3-7; The mass ratio of the flux to the mixture powder is 0.5-7:

1.

8. The method for preparing the adiabatic demagnetizing refrigeration material according to claim 6, characterized in that: The sintering step comprises: Keep the temperature at 850-1200℃ for 1-6 days, then cool to 500-800℃ at a rate of 0.2-50℃ / h, and finally cool naturally to room temperature.

9. Use of the thermal insulation demagnetization refrigeration material according to any one of claims 1 to 4 in the preparation of refrigeration equipment.

10. The use according to claim 9, characterized in that The refrigeration temperature range of the refrigeration equipment is 2-16 Kelvin or sub-Kelvin temperature range.

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