CN114743747B - Low-temperature area magnetic refrigeration material and preparation method and application thereof - Google Patents

Low-temperature area magnetic refrigeration material and preparation method and application thereof Download PDF

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CN114743747B
CN114743747B CN202210438929.7A CN202210438929A CN114743747B CN 114743747 B CN114743747 B CN 114743747B CN 202210438929 A CN202210438929 A CN 202210438929A CN 114743747 B CN114743747 B CN 114743747B
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杨子煜
曾昱嘉
崔宏志
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Shenzhen University
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Abstract

The invention discloses a magnetic refrigeration material in a low-temperature area, and belongs to the technical field of magnetic refrigeration. The molecular formula of the low-temperature region magnetic refrigeration material is Gd 2 MO 5 Wherein M is one or more of Si, ge, mo or W. The magnetic refrigeration material has higher magnetic entropy variable value and adiabatic temperature change in a low temperature region, and is obviously higher than the existing commercial magnetic refrigeration working medium gadolinium gallium garnet Gd 3 Ga 5 O 12 The (GGG) has good refrigeration effect and high magnetic entropy variable value of volume unit, and is beneficial to the development of compact, miniaturized and integrated multipurpose refrigeration devices. The invention also provides a preparation method and application of the magnetic refrigeration material in the low-temperature area.

Description

Low-temperature area magnetic refrigeration material and preparation method and application thereof
Technical Field
The invention relates to the technical field of magnetic refrigeration, in particular to a low-temperature region magnetic refrigeration material and a preparation method and application thereof.
Background
The magnetic refrigeration in the low temperature region (less than 30K) plays a very important role in the fields of modern space technology, superconductivity and high-energy physics, and has great development potential in the aspect of hydrogen and helium liquefaction. The magneto-thermal effect is the core of the magnetic refrigeration technology, and the source is the magnetic field dependence of the system entropy change. Specifically, when the magnetic refrigeration material is in an external magnetic field, the magnetic moment tends to be in an ordered state, and the magnetic entropy becomes low (exothermic process); if the external magnetic field is removed, the high magnetic entropy state is recovered, and the system absorbs heat. By isothermally applying a magnetic field and thermally insulating a demagnetizing field operation, a specific heat transfer medium is combined, and a highly efficient refrigeration cycle can be realized.
The competition of the low-temperature region magnetic refrigeration technology lies in the development of high-efficiency magnetic refrigeration materials, and ideal magnetic refrigeration materials have large magnetic entropy change, high adiabatic temperature variable values and low phonon and electron specific heat. To achieve miniaturization, compactness and multifunction of the refrigerating device, the large magnetic entropy change of the magnetic refrigerating material should be embodied not only in mass units (J.kg) –1 ·K –1 ) Its volume unit value (mJ.cm) –3 ·K –1 ) And also needs to be high enough. However, the prior commercial magnetic refrigeration material has small magnetic entropy variable value in a low temperature area, particularly has low magnetic entropy variable value of volume unit, has poor magnetic refrigeration effect, and is disadvantageousTo develop a compact, miniaturized and integrated multipurpose refrigeration device. In addition, the existing magnetic refrigeration material has complex preparation process and high cost, and the development of the magnetic refrigeration technology in a low-temperature area is hindered.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a magnetic refrigeration material in a low temperature area, which has higher magnetic entropy variable value and adiabatic temperature change in the low temperature area and is obviously higher than the prior commercial gadolinium gallium garnet Gd 3 Ga 5 O 12 The (GGG) working medium has good refrigeration effect and is beneficial to the development of compact, miniaturized and integrated multipurpose refrigeration devices.
The first aspect of the invention provides a low-temperature region magnetic refrigeration material, the molecular formula of the magnetic refrigeration material is Gd 2 MO 5 Wherein M is one or more of Si, ge, mo or W.
The magnetic refrigeration material provided by the invention has higher magnetic entropy variable value in a low temperature area, large refrigeration capacity, good heat insulation temperature change performance and good refrigeration effect in the low temperature area; the magnetic refrigeration material has high volume unit magnetic entropy variable value, and is favorable for developing a compact, miniaturized and integrated multipurpose refrigeration device; in addition, the magnetic refrigeration material provided by the invention also has the processing characteristics of high mechanical stability, oxidation resistance and easiness in granulation, and has a good application prospect.
Optionally, the magnetic refrigeration material belongs to monoclinic system, and the space group is P2 1 /c。
Optionally, the magnetic refrigeration material is in a secondary phase change, and the phase change temperature is 0.3-3K.
Alternatively, when M is Ge, the molecular formula of the magnetic refrigeration material is Gd 2 GeO 5 The unit cell parameters of the magnetic refrigeration material are
Figure BDA0003614256840000021
α＝γ＝90°，β＝105.40°。
Optionally, when M is Si, the molecular formula of the magnetic refrigeration material is Gd 2 GeO 5 The unit cell parameters of the magnetic refrigeration material are
Figure BDA0003614256840000022
α＝γ＝90°，β＝107.57°。/>
Optionally, the application temperature of the magnetic refrigeration material is 0.03-30K.
The magnetic refrigeration material has good magnetic refrigeration effect in a low-temperature region, has low specific heat of electrons and phonons, and has a phase transition temperature (0.3-3K) lower than a helium liquefying point (4.2K), so that the magnetic refrigeration material is very suitable for the magnetic liquefying of helium, and has good application prospect in the fields of modern space technology, superconductivity, high-energy physics and the like.
The second aspect of the invention provides a preparation method of a magnetic refrigeration material in a low temperature region, comprising the following steps:
mixing gadolinium source and metal M source, and heat treating at 1100-1600 ℃ for 6-24 h to obtain the magnetic refrigeration material; the molecular formula of the magnetic refrigeration material is Gd 2 MO 5 Wherein M is one or more of Si, ge, mo or W.
Optionally, the gadolinium source is one or more of gadolinium oxide, gadolinium hydroxide, gadolinium fluoride, gadolinium chloride, gadolinium bromide, gadolinium sulfate, gadolinium nitrate, gadolinium oxalate, gadolinium carbonate, gadolinium boride, gadolinium perchlorate, gadolinium triflate, gadolinium acetylacetonate, and gadolinium isopropoxide.
Optionally, the metal M source is an oxide of metal M or a salt of metal M.
Optionally, the mixing time is 1h-24h.
Optionally, the mixing device comprises any one of a blender, a ball mill or a mixer.
Optionally, when mixing the gadolinium source and the metal M source, further comprising adding an auxiliary agent, the auxiliary agent comprising ethylene glycol and/or oleic acid.
Optionally, the apparatus for heat treatment comprises any one of a muffle furnace, a tube furnace, or an arc furnace.
The preparation method of the magnetic refrigeration material in the low temperature area provided by the second aspect of the invention has the advantages of simple process and high yield, and is beneficial to realizing the mass production of the magnetic refrigeration material.
In a third aspect, the present invention provides a magnetic refrigeration device comprising the magnetic refrigeration material of the first aspect.
The magnetic refrigeration device provided by the third aspect of the invention can realize good refrigeration effect in a low temperature area due to the adoption of the magnetic refrigeration material, and has a compact structure, and is more integrated and miniaturized.
Drawings
FIG. 1 shows Gd obtained in example 1 of the present invention 2 GeO 5 X-ray diffraction pattern of magnetic refrigeration material;
FIG. 2 shows Gd obtained in example 1 of the present invention 2 GeO 5 Specific heat curves of magnetic refrigeration materials under different magnetic field changes;
FIG. 3 shows Gd obtained in example 1 of the present invention 2 GeO 5 A magnetic entropy change and temperature relation diagram of the magnetic refrigeration material;
FIG. 4 shows Gd obtained in example 1 of the present invention 2 GeO 5 A relationship diagram of adiabatic temperature change and temperature of the magnetic refrigeration material under different magnetic fields;
FIG. 5 shows Gd obtained in example 2 of the present invention 2 SiO 5 X-ray diffraction pattern of magnetic refrigeration material;
FIG. 6 shows Gd obtained in example 2 of the present invention 2 SiO 5 Specific heat curves of magnetic refrigeration materials under different magnetic field changes;
FIG. 7 shows Gd obtained in example 2 of the present invention 2 SiO 5 A magnetic entropy change and temperature relation diagram of the magnetic refrigeration material;
FIG. 8 shows Gd obtained in example 2 of the present invention 2 SiO 5 And a graph of adiabatic temperature change and temperature of the magnetic refrigeration material under different magnetic fields.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a magnetic refrigeration material in a low-temperature area, which has higher magnetic entropy variable value in the low-temperature area, good heat insulation temperature change performance, large refrigeration capacity and good refrigeration effect in the low-temperature area.
The magnetic refrigeration material in the invention comprises rare earth gadolinium (Gd) with 8 S 7/2 The magnetic ground state has no orbital angular momentum (J=S=7/2), the interaction of crystal fields is weaker, and the magnetic order temperature is low, so that a stronger magnetocaloric effect is formed; the type and content of M in the magnetic refrigeration material can affect the phase transition temperature and magnetic entropy change of the magnetic refrigeration material. In an embodiment of the invention, the molecular formula of the magnetic refrigeration material is Gd 2 MO 5 Wherein M is one or more of Si, ge, mo or W. In some embodiments of the invention, M is an element, i.e., the magnetic refrigeration material has the formula Gd 2 GeO 5 、Gd 2 SiO 5 、Gd 2 MoO 5 Or Gd 2 WO 5 Any one of the following.
In some embodiments of the present invention, M is two elements, i.e., the molecular formula of the magnetic refrigeration material is Gd 2 M 1 x M 2 1-x O 5 Wherein M is 1 And M 2 Respectively Si, ge, mo or W, and 0<x<1. The molecular formula of the magnetic refrigeration material can be, but is not limited to, gd 2 Ge 0.9 Si 0.1 O 5 、Gd 2 Ge 0.7 Si 0.3 O 5 、Gd 2 Ge 0.5 Si 0.5 O 5 、Gd 2 Ge 0.9 Mo 0.1 O 5 、Gd 2 Ge 0.7 Mo 0.3 O 5 、Gd 2 Ge 0.5 Mo 0.5 O 5 、Gd 2 Mo 0.9 W 0.1 O 5 、Gd 2 Mo 0.7 Si 0.3 O 5 、Gd 2 W 0.5 Si 0.5 O 5 . In some embodiments of the invention, M is three elements, and the molecular formula of the magnetic refrigeration material is Gd 2 M 1 y M 2 z M 3 1-y-z O 5 Wherein M is 1 、M 2 And M 3 Respectively Si, ge, mo and W, 0<y<1 and 0<z<1 and 0<y+z<1. The molecular formula of the magnetic refrigeration material can be, but is not limited to, gd 2 Si 0.4 Ge 0.3 Mo 0.3 O 5 、Gd 2 Si 0.3 Ge 0.3 Mo 0.4 O 5 、Gd 2 Si 0.3 Ge 0.4 Mo 0.3 O 5 、Gd 2 Si 0.7 Ge 0.2 W 0.1 O 5 、Gd 2 Si 0.7 W 0.1 Mo 0.2 O 5 、Gd 2 Mo 0.5 Ge 0.2 W 0.3 O 5 . The phase transition temperature of the magnetic refrigeration material with the molecular formula is in a low temperature area, and the magnetic refrigeration material has higher magnetic entropy variable value and large adiabatic temperature change, thereby achieving good refrigeration effect.
In an embodiment of the present invention, the magnetic refrigeration material belongs to monoclinic system, and the space group is P2 1 And/c. The M element of the magnetic refrigeration material with the configuration has adjustability, and when M is Si and Ge, the Gd sub-lattices are in antiferromagnetic association; when M is Mo or W, M 4+ -M 4+ The magnetic interaction can form a polarization field acting on the Gd sub-lattice, so that the phase transition temperature is regulated and controlled, and the control of the highest magnetic entropy temperature change is realized.
In some embodiments of the invention, M is Ge and the magnetic refrigeration material has the molecular formula Gd 2 GeO 5 The unit cell parameters of the magnetic refrigeration material are
Figure BDA0003614256840000052
α=γ=90°, β= 105.40 °, unit cell density ρ= 7.1345g/cm 3 。
The magnetic refrigeration material has a secondary paramagnetic-antiferromagnetic phase transition (lambda-phase transition), and can keep large magnetic entropy before the phase transition temperature; in addition, the magnetic refrigeration material with the second-level phase change has no structural hysteresis loss and thermal hysteresis loss, so that the high utilization rate of magnetic entropy change in the magnetic refrigeration material is ensured.
The invention is characterized in thatIn some embodiments, M is Si and the magnetic refrigeration material has the molecular formula Gd 2 SiO 5 The unit cell parameters of the magnetic refrigeration material are
Figure BDA0003614256840000051
α=γ=90°, β= 107.57 °, unit cell density ρ= 6.7716g/cm 3 。
The magnetic refrigeration material has good thermal property, low phonon and electron specific heat, small Debye lattice heat capacity coefficient (alpha is less than 9 multiplied by 10) -5 ) The internal heat load loss in the magnetization-demagnetization cycle is low.
In the embodiment of the invention, the phase transition temperature of the magnetic refrigeration material is 0.3-3K. When the magnetic refrigeration material is near the phase transition temperature, the temperature change formed by carrying out adiabatic demagnetization on the magnetic refrigeration material is the largest, and the magnetocaloric effect is the most obvious.
In one embodiment of the invention, M is Ge, and the molecular formula of the magnetic refrigeration material is Gd 2 GeO 5 Debye lattice heat capacity coefficient α=5.6x10 of magnetic refrigeration material -5 Has low phonon and electron specific heat. At the time of the magnetic field change Δb=8.9t, the maximum magnetic entropy of the magnetic refrigeration material becomes 50.3j·kg -1 ·K -1 The magnetic entropy of the corresponding volume unit becomes 358.7 mJ.cm -3 ·K -1 The maximum adiabatic temperature change value of the magnetic refrigeration material is 22.2K.
In one embodiment of the invention, M is Si, and the molecular formula of the magnetic refrigeration material is Gd 2 SiO 5 Debye lattice heat capacity coefficient α=5.9×10 of magnetic refrigeration material -5 Has low phonon and electron specific heat. At the time of the magnetic field change Δb=8.9t, the maximum magnetic entropy of the magnetic refrigeration material becomes 58.4j·kg -1 ·K -1 The magnetic entropy of the corresponding volume unit becomes 395.7 mJ.cm -3 ·K -1 The maximum adiabatic temperature change value of the magnetic refrigeration material is 23.2K.
Gadolinium gallium garnet Gd 3 Ga 5 O 12 (GGG) is a commercial low-temperature magnetic refrigerating material, and its highest magnetic entropy at DeltaB=9T becomes 43.4J.kg at low temperature -1 ·K -1 The corresponding magnetic entropy change value of the volume unit is 307.3 mJ.cm -3 ·K -1 The adiabatic temperature was changed to 20K under adiabatic demagnetization conditions (9.4 T.fwdarw.0.7T). It can be seen that the magnetic entropy variable value of the magnetic refrigeration material provided by the invention is obviously higher than that of the current commercial magnetic refrigeration material, and the magnetic refrigeration material has better magnetic refrigeration effect in a low temperature area; the magnetic refrigeration material has high volume unit magnetic entropy variable value, and is beneficial to development of compact, miniaturized and integrated multipurpose refrigeration devices.
In the embodiment of the invention, the application temperature of the magnetic refrigeration material is 0.03-30K. The magnetic refrigeration material provided by the invention has obvious magnetocaloric effect in a temperature range of 0.03-30K, and has a wider use temperature range; the phase transition temperature is below the helium liquefaction point (4.2K), which is beneficial to the application of the phase transition temperature in the efficient magnetic liquefaction of helium.
The invention also provides a preparation method of the magnetic refrigeration material in the low temperature area, which comprises the following steps:
mixing gadolinium source and metal M source, and heat treating at 1100-1600 deg.c for 6-24 hr to obtain magnetic refrigerating material; the molecular formula of the magnetic refrigeration material is Gd 2 MO 5 Wherein M is one or more of Si, ge, mo or W.
In an embodiment of the invention, the source of gadolinium is one or more of gadolinium oxide, gadolinium hydroxide, gadolinium fluoride, gadolinium chloride, gadolinium bromide, gadolinium sulfate, gadolinium nitrate, gadolinium oxalate, gadolinium carbonate, gadolinium boride, gadolinium perchlorate, gadolinium triflate, gadolinium acetylacetonate and gadolinium isopropoxide. The metal M source is an oxide of metal M or a salt of metal M. In some embodiments of the invention, M is Ge and the metal M source may be, but is not limited to, germanium dioxide, germanium tetrachloride or germanium isopropoxide. In some embodiments of the invention, M is Si and the metal M source may be, but is not limited to, silicon oxide, silicon acetate, tetraethyl silicate, or amorphous silicon.
The metal M source adopted by the invention has low cost and easily available raw materials, and is more beneficial to industrialized popularization. In some embodiments of the invention, gadolinium oxide and an oxide of M are used as reaction raw materials, and the reaction is carried out by using the oxide as the raw materials, so that the preparation cost can be reduced, and the processing characteristics of the product can be improved.
In an embodiment of the invention, the mixing of the gadolinium source and the metal M source is performed in a stoichiometric ratio, wherein the molar ratio of elements of the gadolinium source and the metal M source is 2:1.
In embodiments of the present invention, the gadolinium source and the metal M source may be mixed in a manner that is specifically, but not limited to, stirring or ball milling. In some embodiments of the invention, the mixing apparatus comprises any one of a ball mill, a blender, or a mixer. In the embodiment of the invention, the mixing time of the gadolinium source and the metal M source is 1h-24h. The time for mixing the gadolinium source and the metal M source may be, in particular but not limited to, 1h, 3h, 7h, 10h, 15h or 24h.
In some embodiments of the invention, mixing the gadolinium source with the metal M source further comprises adding a grinding aid comprising ethylene glycol and/or oleic acid. The addition of the auxiliary agent is favorable for fully mixing the gadolinium source and the metal M source and fully reacting in the subsequent heat treatment process, so that the processing characteristics of the product are improved.
In an embodiment of the invention, the temperature of the heat treatment is 1100-1600 ℃. The temperature of the heat treatment may be, but is not limited to, 1100 ℃, 1300 ℃, 1500 ℃, or 1600 ℃. In the embodiment of the invention, the time of the heat treatment is 6h-24h, and the time of the heat treatment can be specifically but not limited to 6h, 9h, 11h, 15h, 19h or 24h. In an embodiment of the present invention, the apparatus for heat treatment comprises any one of a muffle furnace, a tube furnace, or an arc furnace.
The magnetic refrigeration material provided by the invention has the advantages of simple preparation process, wide sources of raw materials used for preparation and low cost, and is suitable for industrial production.
The invention also provides a magnetic refrigeration device, which comprises the magnetic refrigeration material.
The magnetic refrigeration device provided by the invention has good refrigeration effect in a low-temperature area, high energy utilization efficiency and no pollution, and has important application prospects in the field of helium magnetic liquefaction. In some embodiments of the invention, a magnetic refrigeration device is used in the magnetic liquefaction process of helium. In some embodiments of the invention, the magnetic refrigerator is used in cooling a superconducting device of a magnetic resonance apparatus (MRI). The superconducting equipment involved in the nuclear magnetic resonance apparatus should be in a low-temperature environment with high-efficiency refrigeration and stability, and the refrigeration equipment should be integrated with low microphonics and thermal noises as much as possible, so as to obtain the results of high signal-to-noise ratio and resolution capability.
The magnetic refrigeration device provided by the third aspect of the invention has good refrigeration capacity in a low temperature area due to the adoption of the magnetic refrigeration material.
The invention is described in further detail below in terms of a number of examples.
Example 1
The preparation method of the magnetic refrigeration material in the low temperature area comprises the following steps:
gd is put into 2 O 3 With GeO 2 Placing the mixture in a ball mill after being prepared according to the stoichiometric ratio, adding a small amount of glycol, placing the mixture in a muffle furnace after ball milling for 5 hours, and annealing for 24 hours at 1400 ℃ to fully perform solid phase reaction on the material to obtain Gd 2 GeO 5 A low temperature region magnetic refrigeration material.
Example 2
The preparation method of the magnetic refrigeration material in the low temperature area comprises the following steps:
gd is put into 2 O 3 With SiO 2 Placing the mixture in a ball mill after being prepared according to the stoichiometric ratio, adding a small amount of oleic acid, placing the mixture in a muffle furnace after ball milling for 3 hours, and annealing for 24 hours at 1500 ℃ to fully perform solid phase reaction on the material to obtain Gd 2 SiO 5 A low temperature region magnetic refrigeration material.
Effect examples
In order to verify the structure and the performance of the magnetic refrigeration material prepared by the invention, the invention also provides an effect embodiment.
Gd of this example 1 was measured by X-ray powder diffractometer 2 GeO 5 The magnetic refrigeration material is subjected to structural characterization, and the test result is shown in fig. 1. As can be seen from fig. 1, gd 2 GeO 5 The X-ray diffraction experimental spectrum of the magnetic refrigeration material is well matched with the full spectrum calculation curve of the model, and the fitting degree χ is good 2 2.478, which indicates that the resulting material is Gd 2 GeO 5 . In addition, gd 2 GeO 5 The diffraction peak shape of the magnetic refrigeration material is sharp, and the crystallinity of the sample is high. FIG. 1 shows that the structure is monoclinic system and the space group isP 2 1 /c。
Gd of example 1 was measured by a comprehensive physical measurement System (PPMS) 2 GeO 5 Specific heat capacity of the magnetic refrigeration material under different magnetic field change conditions. Wherein the specific heat curves of the external field B at 0T, 2T and 8.9T were measured, as shown in fig. 2. Fitting the 0T curve shows that the theoretical phase transition temperature is 1.6K.
According to the formula
Figure BDA0003614256840000091
And DeltaS M S (B, T) -S (0, T), wherein S (B, T) is the magnetic entropy at T temperature, C p (B, T) is a function of the magnetic component of the specific heat and the temperature, ΔS M The magnetic entropy is the difference between the magnetic entropy of the B external field and the magnetic entropy of the zero external field under the isothermal condition. The specific heat curve of FIG. 2 was calculated according to the above formula to obtain Gd of example 1 2 GeO 5 The magnetic entropy change of the magnetic refrigeration material is plotted against temperature as shown in fig. 3. As can be seen from fig. 3, gd 2 GeO 5 When the magnetic refrigeration material is delta B=8.9T, the highest magnetic entropy becomes 50.3J.kg -1 ·K -1 The magnetic entropy of the corresponding volume unit becomes 358.7 mJ.cm -3 ·K -1 。
Adiabatic temperature change information can be obtained by comparing the isentropic points in the magnetic entropy curve S (B, T) at Δb=b external field and the magnetic entropy curve S (0, T) at zero field. FIG. 4 shows Gd according to example 1 of the present invention 2 GeO 5 Adiabatic temperature change information of the magnetic refrigeration material under different magnetic fields. As can be seen from fig. 4, gd 2 GeO 5 The maximum adiabatic temperature of the magnetic refrigeration material becomes 22.2K at Δb=8.9t.
FIG. 5 shows Gd of example 2 2 SiO 5 The X-ray diffraction experimental spectrum of the magnetic refrigeration material is well matched with the full spectrum calculation curve of the model, and the fitting degree χ is good 2 5.698, which indicates that the resulting material is high crystallinity Gd 2 SiO 5 The structure is monoclinic system, and the space group is P2 1 /c。
FIG. 6 shows Gd according to example 2 of the present invention 2 SiO 5 Ratio of magnetic refrigeration materials under different magnetic field change conditionsThermal curves, wherein specific heat curves of external field B at 0T, 2T and 8.9T were measured. Fitting the 0T curve shows that the theoretical phase transition temperature is 1.5K.
Gd for example 2 2 SiO 5 The specific heat curves of the magnetic refrigeration material under different magnetic field change conditions are processed by adopting the same calculation method to obtain Gd of the embodiment 2 2 SiO 5 A graph of magnetic entropy change versus temperature for a magnetic refrigeration material is shown in fig. 7. As can be seen from fig. 7, gd 2 SiO 5 When the magnetic refrigeration material is delta B=8.9T, the highest magnetic entropy becomes 58.4J.kg -1 ·K -1 The magnetic entropy of the corresponding volume unit becomes 395.7 mJ.cm -3 ·K -1 . Examples 1-2 magnetic refrigeration materials see table 1 for the highest magnetic entropy variable at Δb=8.9t.
Gd of example 2 can be obtained in the same manner of calculation 2 SiO 5 The maximum adiabatic temperature change of the magnetic refrigeration material at Δb=8.9t is 23.2K, as shown in fig. 8. Examples 1-2 magnetic refrigeration materials see table 1 for maximum adiabatic temperature change values at Δb=8.9t.
Using the formula
Figure BDA0003614256840000101
The relative refrigerating capacity of the magnetic refrigerating material under different magnetic field changes can be calculated, wherein delta S M (DeltaB, T) is a function of magnetic entropy change and temperature T under DeltaB external field change, T c 、T h Representing cold and hot end temperatures, respectively. By the above calculation, gd of example 1 can be obtained 2 GeO 5 When the magnetic refrigerating material is delta B=8.9T, the maximum relative refrigerating capacity is 608.1 J.kg -1 。
Gd of example 2 can be obtained by the same numerical treatment 2 SiO 5 When the magnetic refrigerating material is delta B=8.9T, the maximum relative refrigerating capacity is 649.5 J.kg -1 . Examples 1-2 magnetic refrigeration materials the relative refrigeration capacity at Δb=8.9t is shown in table 1.
Table 1 table of performance parameters (Δb=8.9t) of the magnetic refrigeration materials of examples 1 to 2 of the present invention
Experimental group Example 1 Example 2
Molecular formula Gd 2 GeO 5 Gd 2 SiO 5
Maximum magnetic entropy change (J.kg) –1 ·K –1 /mJ·cm –3 ·K –1 ) 50.3/358.7 58.4/395.7
Maximum adiabatic temperature change (K) 22.2 23.2
Relative refrigerating capacity (J.kg) -1 ) 608.1 649.5
As can be seen from Table 1, the magnetic refrigeration material in the low temperature region has larger magnetic entropy change and higher adiabatic temperature change performance, and can realize good refrigeration effect in the low temperature region.
The above embodiments are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, but any insubstantial changes and substitutions made by those skilled in the art on the basis of the present invention are intended to be within the scope of the present invention as claimed.

Claims (6)

1. A low temperature zone magnetic refrigeration material, characterized in that: the molecular formula of the magnetic refrigeration material is Gd 2 MO 5 Wherein M is a combination of any two or more of W or Si, ge, mo, W; the application temperature of the magnetic refrigeration material is 0.03-30K.
2. The low temperature zone magnetic refrigerant material of claim 1, wherein: the magnetic refrigerating material belongs to monoclinic system, and the space group isP 2 1 /c。
3. A low temperature zone magnetic refrigeration material as claimed in claim 1 or claim 2, wherein: the magnetic refrigeration material is in secondary phase change, and the phase change temperature is 0.3-3K.
4. A method for preparing a low temperature region magnetic refrigeration material as claimed in any one of claims 1 to 3, comprising the steps of: mixing a gadolinium source and a metal M source, and performing heat treatment at 1100-1600 ℃ for 6-24 hours to obtain a magnetic refrigeration material; the molecular formula of the magnetic refrigeration material is Gd 2 MO 5 Wherein M is a combination of any two or more of W or Si, ge, mo, W.
5. The method for preparing the magnetic refrigeration material in the low temperature area according to claim 4, wherein: the gadolinium source is one or more of gadolinium oxide, gadolinium hydroxide, gadolinium fluoride, gadolinium chloride, gadolinium bromide, gadolinium sulfate, gadolinium nitrate, gadolinium oxalate, gadolinium carbonate, gadolinium boride, gadolinium perchlorate, gadolinium triflate, gadolinium acetylacetonate and gadolinium isopropoxide; the metal M source is an oxide of metal M or a salt of metal M.
6. A magnetic refrigeration device, characterized in that: the magnetic refrigeration device comprising the magnetic refrigeration material according to any one of claims 1 to 3.
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