WO2023207400A1 - 一种稀土氟化物单晶在磁制冷中的应用 - Google Patents

一种稀土氟化物单晶在磁制冷中的应用 Download PDF

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WO2023207400A1
WO2023207400A1 PCT/CN2023/081822 CN2023081822W WO2023207400A1 WO 2023207400 A1 WO2023207400 A1 WO 2023207400A1 CN 2023081822 W CN2023081822 W CN 2023081822W WO 2023207400 A1 WO2023207400 A1 WO 2023207400A1
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magnetic
rare earth
single crystal
earth fluoride
lithium
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PCT/CN2023/081822
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English (en)
French (fr)
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李昺
原东升
刘鹏
加西亚•比略拉恩卡纳西翁•安东尼亚
张志东
岛村清史
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中国科学院金属研究所
国立研究开发法人物质 •材料研究机构
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Publication of WO2023207400A1 publication Critical patent/WO2023207400A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F17/00—Compounds of rare earth metals
    • C01F17/30—Compounds containing rare earth metals and at least one element other than a rare earth metal, oxygen or hydrogen, e.g. La4S3Br6
    • C01F17/36—Compounds containing rare earth metals and at least one element other than a rare earth metal, oxygen or hydrogen, e.g. La4S3Br6 halogen being the only anion, e.g. NaYF4
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/08—Materials not undergoing a change of physical state when used
    • C09K5/14—Solid materials, e.g. powdery or granular
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/12—Halides
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B21/00—Machines, plants or systems, using electric or magnetic effects
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2321/00—Details of machines, plants or systems, using electric or magnetic effects
    • F25B2321/002—Details of machines, plants or systems, using electric or magnetic effects by using magneto-caloric effects
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]

Definitions

  • the invention belongs to the field of magnetic functional materials, and specifically relates to a giant magnetic card effect material that can be driven by a small magnetic field in a low temperature range.
  • refrigeration technology is well known and widely used in daily life, such as air conditioning, refrigerators, agriculture and medical treatment, etc.
  • the temperature below liquid hydrogen is called the low-temperature zone, which can be applied to cosmic communications, quantum computers or gas liquefaction in chemical industry, as well as ultra-sensitive detectors in space, etc.
  • All refrigeration technologies are inseparable from helium.
  • the superconducting magnets that provide magnetic fields in adiabatic demagnetization refrigeration refrigeration devices need to be cooled with liquid helium.
  • 3He/4He dilution refrigerators and He adsorption refrigerators are even more inseparable from helium. .
  • the new magnetic refrigeration technology based on the magnetic card effect has the advantages of environmental friendliness, high refrigeration efficiency, low energy consumption, low noise, no pollution, and stability and reliability. Therefore, it has received widespread attention from scientific researchers.
  • the present invention provides a method that can utilize a small magnetic field to drive and obtain large magnetic entropy.
  • the magnetic card material is a lithium rare earth fluoride single crystal.
  • the purpose of the present invention is to disclose the application of a rare earth fluoride single crystal in magnetic refrigeration.
  • the rare earth fluoride single crystal is a lithium rare earth fluoride single crystal.
  • a changing magnetic field of -20kOe can obtain a large magnetic entropy change, and this series of materials has good thermal conductivity.
  • the discovery of this material provides the possibility for the simplification and widespread application of low-temperature magnetic refrigeration devices.
  • the lithium rare earth fluoride single crystal sample changes its magnetic moment from chaos to order.
  • the interaction energy between the atomic magnetic moments and with the external magnetic field decreases. Its magnetic entropy decreases and it releases the external magnetic field. hot.
  • the magnetic moment of the lithium rare earth fluoride single crystal changes from order to chaos, the magnetic entropy increases, and energy is absorbed from the outside world.
  • the sample is adiabatic, it manifests itself as a temperature change of the lithium rare earth fluoride single crystal sample itself.
  • the chemical formula of the lithium rare earth fluoride is LiREF 4 , where RE is a rare earth element.
  • the rare earth element RE is one or more of gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm) and ytterbium (Yb).
  • Gd gadolinium
  • Tb terbium
  • Dy dysprosium
  • Ho holmium
  • Er erbium
  • Tm thulium
  • Yb ytterbium
  • the lithium rare earth fluoride has a structure of tetragonal scheelite.
  • the lithium rare earth fluoride is a single crystal with extremely strong magnetic anisotropy.
  • the easy magnetization directions of LiGdF 4 , LiTbF 4 and LiHoF 4 are parallel to the C axis, and the easy magnetization directions of LiDyF 4 , LiErF 4 , LiYbF 4 and LiTmF 4 are perpendicular to the C axis.
  • LiGdF 4 exhibits paramagnetism
  • LiTmF 4 exhibits Van Vleck paramagnetism
  • LiTbF 4 and LiHoF 4 exhibit ferromagnetic ordering at Curie temperatures below 2.87K and 1.53K respectively
  • LiDyF 4 , LiErF 4 and LiYbF 4 exhibit antiferromagnetic ordering below Nel temperatures of 0.62K, 0.38K and 0.128K respectively.
  • the application temperature range of lithium rare earth fluoride single crystal is the low temperature range below 20K.
  • the isothermal magnetic entropy change ⁇ S is an important parameter to measure the performance of a magnetic card material. Therefore, the present invention uses a superconducting quantum interferometer to measure the magnetization curves at different temperatures in the easy magnetization direction of a lithium rare earth fluoride single crystal sample. Then the Maxwell relation is used to process the obtained magnetization curve data at different temperatures, and the relationship between magnetic entropy change and temperature change is obtained.
  • the lithium rare earth fluoride single crystal By applying a small changing magnetic field of 0-20kOe to the easy magnetization direction of the lithium rare earth fluoride single crystal sample, the lithium rare earth fluoride single crystal exhibits a large isothermal magnetic entropy change, among which LiGdF 4 , LiTbF 4 , LiHoF 4 , LiDyF 4 , LiErF 4 , LiYbF 4 and LiTmF 4 points obtained 50.35J ⁇ kg -1 ⁇ K -1 , 21.12J ⁇ kg -1 ⁇ at 1.8K, 4K, 4K, 1.8K, 1.8K, 1.8K and 18K.
  • the thermal conductivity of the magnetic card material is closely related to the overall refrigeration efficiency of the device.
  • the thermal conductivity test of lithium rare earth fluoride single crystal was carried out through the heat transport option of the comprehensive physical property measurement system. Since the thermal conductivity of the lithium rare earth fluoride single crystal sample is high at low temperatures, the four-wire method was used for measurement to reduce errors.
  • the shape of the sample was a needle-like cuboid shape, and a cooling measurement method was used.
  • the thermal conductivity of LiTbF 4 and LiErF 4 reaches 50W ⁇ K -1 m -1 at 25K.
  • a magnetic refrigeration method based on lithium rare earth fluoride single crystal which is characterized in that: using lithium rare earth fluoride single crystal as a magnetic working medium, by applying and removing a magnetic field to the magnetic working medium, the temperature of the magnetic working medium is generated. Change and transfer heat with the heat exchanger to achieve the purpose of refrigeration.
  • the magnetic working fluid lithium rare earth fluoride single crystal may be one or more of LiGdF 4 , LiTbF 4 , LiHoF 4 , LiDyF 4 , LiErF 4 , LiYbF 4 and LiTmF 4 ; when it is multiple, by Different lithium rare earth fluoride single crystals are mixed and arranged to expand the low-temperature refrigeration range.
  • Two or more rare earth elements can also be incorporated into the process of preparing lithium rare earth fluoride single crystal to expand the low-temperature refrigeration range.
  • a magnetic refrigeration device driven by a small magnetic field characterized in that the device includes a lithium rare earth fluoride single crystal as a magnetic working fluid.
  • the magnetic working fluid lithium rare earth fluoride single crystal may be one or more of LiGdF 4 , LiTbF 4 , LiHoF 4 , LiDyF 4 , LiErF 4 , LiYbF 4 and LiTmF 4 ; when it is multiple, by Different lithium rare earth fluoride single crystals are mixed and arranged to expand the low-temperature refrigeration range.
  • the refrigeration device also includes a magnetic field applying component, a thermal switch, a heat sink, and a load.
  • the magnetic field applying component can be made of permanent magnets, electromagnets or superconducting magnets. Permanent magnets are preferred, which can effectively simplify the device volume and optimize the design.
  • a thermal switch can be used. Mechanical contact type, superconducting type, gas type or magnetoresistive type thermal switch, preferably superconducting type thermal switch.
  • Lithium rare earth fluoride single crystal undergoes phase change at low temperatures, so when used as a magnetic refrigeration device When the magnetic working medium is placed in the center, the refrigeration temperature zone of the magnetic refrigeration device can be placed in a low temperature range of less than 20K.
  • Lithium rare earth fluoride single crystal has extremely strong magnetic anisotropy. It can reach saturation by applying a small magnetic field in the direction of the easy magnetization axis. Components that provide small magnetic fields, such as common permanent magnets, are cheap and small in size. It can not only greatly reduce the cost of the refrigeration device, but also optimize the design of the refrigeration device, and expand the application scope of the magnetic refrigeration device to large scientific experimental devices and any devices and operations that require low and extremely low temperature environments.
  • the present invention can effectively expand the refrigeration interval, meet the needs of different refrigeration intervals, and further expand the scope of application.
  • the refrigeration range can also be broadened.
  • LiGdF 4 , LiTbF 4 , LiHoF 4 , LiDyF 4 , LiErF 4 , LiYbF 4 and LiTmF 4 points obtained 50.35J ⁇ kg -1 ⁇ K - at 1.8K, 4K, 4K, 1.8K, 1.8K, 1.8K and 18K .
  • Lithium rare earth fluoride single crystal has high thermal conductivity in the low-temperature refrigeration zone. Among them, the thermal conductivity of LiTbF 4 and LiErF 4 reaches 50W ⁇ K -1 ⁇ m -1 at 25K, which can speed up the development of magnetic card materials. The heat exchange speed improves the efficiency of the overall magnetic refrigeration device.
  • the preparation process of lithium rare earth fluoride single crystal is mature and capable of large-scale industrial production. It greatly reduces the use cost of the material and the manufacturing cost of the refrigeration system, and can be quickly and widely promoted and applied.
  • Figure 1 shows the crystal structure of lithium rare earth fluoride.
  • Figure 2 is a schematic diagram of magnetic refrigeration.
  • Figure 3 shows the magnetic entropy change curve of gadolinium gallium garnet and lithium rare earth fluoride single crystal under the application of a 0-10kOe changing magnetic field along the direction of the easy magnetization axis.
  • Figure 4 shows the magnetic entropy change curve of gadolinium gallium garnet and lithium rare earth fluoride single crystal under the application of a 0-20kOe changing magnetic field along the direction of the easy magnetization axis.
  • Figure 5 shows the relationship between thermal conductivity and temperature of LiTbF 4 single crystal.
  • Figure 6 shows the relationship between thermal conductivity and temperature of LiErF 4 single crystal.
  • Figure 7 is a schematic structural diagram of the magnetic refrigeration device.
  • An application device of lithium rare earth fluoride single crystal specifically a magnetic refrigeration device driven by a magnetic field.
  • the magnetic working medium is lithium rare earth fluoride single crystal, specifically LiGdF 4 , LiTbF 4 , LiHoF 4 , LiDyF 4 , LiErF 4 , LiYbF 4 and LiTmF 4 .
  • the device also includes a magnetic field applying component, a thermal switch, a heat-sink, a load, etc.
  • the magnetic field applying components can be permanent magnets, electromagnets or superconducting magnets
  • the thermal switches can be mechanical contact, superconducting, gas or reluctance thermal switches
  • the function of the load is used to achieve cooling
  • the heat sink plays a role in heat dissipation effect.
  • the lithium rare earth fluoride single crystal is in the same temperature state as the heat sink in the zero magnetic field state, and then the magnetic field is raised while the thermal switch remains closed.
  • the magnetic field When the magnetic field reaches its maximum, turn on the heat switch, and then reduce the magnetic field. When the temperature of the magnetic working fluid drops to the temperature required by the load, some magnetic field still remains. As the magnetic field continues to decrease, the magnetic working fluid will absorb heat from the load to cool the load, thereby achieving the purpose of cooling and realizing cooling function of the entire unit.
  • the refrigeration range can be effectively expanded.
  • LiErF 4 and LiTbF 4 are mixed and arranged so that the refrigeration interval is expanded from the temperature interval below 6K when LiErF 4 is used alone to the temperature interval below 15K; in another embodiment, LiDyF 4 and LiTbF 4 mixed arrangement expands the refrigeration range from the temperature range below 4K when LiDyF 4 alone is used to the temperature range below 15K; or by incorporating a certain amount of other rare earth elements (Gd, Tb) in the process of preparing lithium rare earth fluoride single crystals , Dy, Ho, Er, Tm and Yb), when preparing a lithium rare earth fluoride single crystal containing two or more rare earth elements, the low-temperature refrigeration range can also be expanded.
  • the following examples conduct magnetic card performance tests on LiGdF 4 , LiTbF 4 , LiHoF 4 , LiDyF 4 , LiErF 4 , LiYbF 4 and LiTmF 4 respectively.
  • the test results show that in the low temperature range of less than 20K, LiGdF 4 , LiTbF 4 and LiHoF 4 , LiDyF 4 and LiErF 4 both exhibit an isothermal magnetic entropy change of 17.5J ⁇ kg -1 ⁇ K -1 that is superior to traditional GGG materials.
  • LiTbF 4 and LiErF 4 both exhibit thermal conductivities reaching 50W ⁇ K -1 m -1 in the low temperature range.
  • a small sample was first cut out from a large LiGdF 4 single crystal sample with a scalpel and weighed by an electronic balance. The mass of the sample was 7.35 mg. And use double-sided tape to fix the sample in a plastic sample tube.
  • MH test along the easy magnetization direction of the sample. Measure an MH curve at a temperature of 1.8K. Within the temperature range of 2K-10K, measure an MH curve every 1K. Wire. In the temperature range of 10K-24K, an MH curve is measured every 2K. In each tested MH curve, a data point is measured every 500Oe under a magnetic field of 0-10kOe, and a data point is measured every 1000Oe under a magnetic field of 10kOe-20kOe.
  • the relationship between the magnetic entropy change and the temperature change of the LiGdF 4 sample after applying a 0-10kOe and 0-20kOe changing magnetic field along the easy magnetization direction is calculated through the Maxwell equation.
  • the LiGdF 4 sample obtained a magnetic entropy change of 50.35J ⁇ kg -1 ⁇ K -1 under a changing magnetic field of 0-20kOe.
  • a small sample was first cut out from a large LiTbF 4 single crystal sample using a scalpel, and weighed by an electronic balance. The sample mass was 5.4 mg. And use double-sided tape to fix the sample in a plastic sample tube.
  • MH test i.e., magnetization curve test
  • Within the temperature range of 1.85K-2.85K measure an MH curve every 0.2K.
  • an MH curve is measured every 2K.
  • a data point is measured every 500Oe under a magnetic field of 0-10kOe, and a data point is measured every 1000Oe under a magnetic field of 10kOe-20kOe.
  • the relationship between the magnetic entropy change and the temperature change of the LiTbF 4 sample after applying a 0-10kOe and 0-20kOe changing magnetic field along the easy magnetization direction is calculated through the Maxwell equation.
  • the LiTbF 4 single crystal sample obtained a magnetic entropy change of 21.12J ⁇ kg -1 ⁇ K -1 under a changing magnetic field of 0-20kOe.
  • a small sample was first cut out from a large LiDyF 4 single crystal sample with a scalpel and weighed by an electronic balance. The mass of the sample was 1.48 mg. And use double-sided tape to fix the sample in a plastic sample tube.
  • MH test along the easy magnetization direction of the sample. Measure an MH curve at a temperature of 1.8K, and measure an MH curve every 1K in the temperature range of 2K-10K. In the temperature range of 10K-24K, an MH curve is measured every 2K. In each tested MH curve, a data point is measured every 500Oe under a magnetic field of 0-10kOe, and a data point is measured every 1000Oe under a magnetic field of 10kOe-20kOe.
  • the relationship between the magnetic entropy change and the temperature change of the LiDyF 4 sample after applying a 0-10kOe and 0-20kOe changing magnetic field along the easy magnetization direction is calculated through the Maxwell equation.
  • the LiDyF 4 sample obtained a magnetic entropy change of 24.45J ⁇ kg -1 ⁇ K -1 under a changing magnetic field of 0-20kOe.
  • the magnetic test In the magnetic test, first use a scalpel to cut a small sample from the large LiHoF 4 single crystal sample, and weigh it with an electronic balance. The mass of the sample is 6.35 mg. And use double-sided tape to fix the sample in a plastic sample tube. Next, conduct the MH test along the easy magnetization direction of the sample. Measure an MH curve at a temperature of 1.8K, and measure an MH curve every 1K in the temperature range of 2K-10K. In the temperature range of 10K-24K, an MH curve is measured every 2K. In each tested MH curve, a data point is measured every 500Oe under a magnetic field of 0-10kOe, and a data point is measured every 1000Oe under a magnetic field of 10kOe-20kOe.
  • the relationship between the magnetic entropy change and the temperature change of the LiHoF 4 sample after applying a 0-10kOe and 0-20kOe changing magnetic field along the easy magnetization direction is calculated through the Maxwell equation.
  • the LiHoF 4 single crystal sample obtained a magnetic entropy change of 24.98J ⁇ kg -1 ⁇ K -1 under a changing magnetic field of 0-20kOe.
  • the magnetic test In the magnetic test, first use a scalpel to cut a small sample from a large LiErF 4 single crystal sample, and weigh it with an electronic balance. The mass of the sample is 2.55 mg. And use double-sided tape to fix the sample in a plastic sample tube. Next, conduct the MH test along the easy magnetization direction of the sample. Measure an MH curve at a temperature of 1.8K, and measure an MH curve every 1K in the temperature range of 2K-10K. In the temperature range of 10K-24K, an MH curve is measured every 2K. In each tested MH curve, a data point is measured every 500Oe under a magnetic field of 0-10kOe, and a data point is measured every 1000Oe under a magnetic field of 10kOe-20kOe.
  • the LiErF 4 sample obtained a magnetic entropy change of 21.95J ⁇ kg -1 ⁇ K -1 at a temperature of 1.8K and a changing magnetic field of 20kOe.
  • the thermal conductivity test of LiErF 4 single crystal was carried out.
  • the thermal conductivity of the LiErF 4 sample along the C-axis direction was tested through the heat transport option of the comprehensive physical property measurement system.
  • the shape of the sample was rectangular.
  • the four-wire method was used for testing.
  • the cross-sectional area was 9.3mm 2
  • the surface area was 104.37mm 3
  • the electrode spacing was 1.87mm
  • the thermal radiation coefficient was set to 1.
  • the temperature range of the test was 25K-300K
  • the cooling test was carried out at a rate of 0.1K/min. Then the relationship between the thermal conductivity of the LiErF 4 sample and the temperature change was obtained, and the thermal conductivity reached 50W ⁇ K -1 ⁇ m at 25K. -1 .
  • a small piece of sample was first cut out from the large LiTmF 4 single crystal sample with a scalpel. After weighing with an electronic balance, the sample mass was 82.63 mg. And use double-sided tape to fix the sample in a plastic sample tube.
  • MH test along the easy magnetization direction of the sample. Measure an MH curve at a temperature of 1.8K, and measure an MH curve every 1K in the temperature range of 2K-10K. In the temperature range of 10K-24K, an MH curve is measured every 2K. In each tested MH curve, a data point is measured every 500Oe under a magnetic field of 0-10kOe, and a data point is measured every 1000Oe under a magnetic field of 10kOe-20kOe.
  • the relationship between the magnetic entropy change and the temperature change of the LiTmF 4 sample after applying a 0-10kOe and 0-20kOe changing magnetic field along the easy magnetization direction is calculated through the Maxwell equation.
  • the LiTmF 4 sample obtained 0.692 under a changing magnetic field of 0-20kOe Magnetic entropy change of J ⁇ kg -1 ⁇ K -1 size.
  • the magnetic test In the magnetic test, first use a scalpel to cut a small sample from the large LiYbF 4 single crystal sample, and weigh it with an electronic balance. The mass of the sample is 4.81 mg. And use double-sided tape to fix the sample in a plastic sample tube. Next, conduct the MH test along the easy magnetization direction of the sample. Measure an MH curve at a temperature of 1.8K, and measure an MH curve every 1K in the temperature range of 2K-10K. In the temperature range of 10K-24K, an MH curve is measured every 2K. In each tested MH curve, a data point is measured every 500Oe under a magnetic field of 0-10kOe, and a data point is measured every 1000Oe under a magnetic field of 10kOe-20kOe.
  • the relationship between the magnetic entropy change and the temperature change of the LiYbF 4 sample after applying a 0-10kOe and 0-20kOe changing magnetic field along the easy magnetization direction is calculated through the Maxwell equation.
  • the LiYbF 4 sample obtained a magnetic entropy change of 14.7J ⁇ kg -1 ⁇ K -1 under a changing magnetic field of 0-20kOe.

Abstract

本发明公开了一种稀土氟化物单晶在磁制冷中的应用、磁制冷方法和磁制冷装置，属于磁性功能材料领域。该系列磁卡材料为锂稀土氟化物，化学式是LiREF4，其中RE为稀土元素钆、铽、镝、钬、铒、铥和镱之中的一种或多种。该系列磁卡材料单晶具有极强的磁各向异性，通过在磁卡材料的易磁化轴方向上施加一个0-20kOe的变化磁场，LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4分在1.8K、4K、4K、1.8K、1.8K、1.8K和18K处获得50.35J·kg-1·K-1、21.12J·kg-1·K-1、24.98J·kg-1·K-1、24.45J·kg-1·K-1、21.95J·kg-1·K-1、14.7J·kg-1·K-1和0.692J·kg-1·K-1大小的等温磁熵变。其中，LiTbF4和LiErF4在25K处的热导率达到了50W·K-1·m-1。

Description

一种稀土氟化物单晶在磁制冷中的应用 技术领域
本发明属于磁性功能材料领域，具体涉及一种低温区间内能由小磁场驱动的巨磁卡效应材料。
背景技术
现如今，制冷技术已经被人们所熟知并广泛应用于日常生活中，如空调、冰箱、农业和医疗等等。在制冷技术中，在低于液氢的温度称低温区，可以将其应用于宇宙通讯、量子计算机或化工中气体液化，以及空间中的超灵敏探测器等等。其制冷技术均离不开氦气，如绝热去磁制冷的制冷装置中提供磁场的超导磁铁需要用液氦进行冷却，3He/4He稀释制冷机和He吸附式制冷机更加离不开氦气。而基于磁卡效应的新型磁制冷技术，相较于传统制冷方法，有着环境友好、制冷效率高、能量消耗少、低噪声、无污染和稳定可靠等优点。因此得到了科研人员的广泛关注。
目前低温磁制冷中较为成熟的磁工质为石榴石系列(Gd3Ga5O12(简称GGG)、Dy3Al5O12(简称DAG))。然而为了获取较大的磁熵变，通常需要给磁工质施加一个较大的变化磁场(0-50kOe)，而这种磁场需要依靠体积较大的电磁铁和超导磁铁，装置高昂的费用、复杂的装置设计和较大的体积严重阻碍了磁制冷技术走向广泛应用。因此，寻找一个低温区间内由小磁场驱动下，可以获得大磁熵变的磁工质是低温磁制冷的一个关键。
针对上述问题，本发明提供一种可利用小磁场进行驱动并获得大磁熵 变的磁卡材料，该磁卡材料为锂稀土氟化物单晶。
发明内容
本发明的目的在于公开了一种稀土氟化物单晶在磁制冷中的应用，该稀土氟化物单晶为锂稀土氟化物单晶，在低温区间内通过向该材料易磁化方向上施加一个0-20kOe的变化磁场，可获得一个大的磁熵变，且该系列材料具有良好的导热能力。该材料的发现为低温磁制冷装置的简化和广泛应用提供了可能性。
本发明技术方案如下：
一种锂稀土氟化物单晶在磁制冷中的应用。
锂稀土氟化物单晶样品在外磁场的作用下，磁矩由杂乱变为有序，原子磁矩之间及与外磁场之间的相互作用能降低，它的磁熵减小并对外界进行放热。反之，在移除磁场的过程中，锂稀土氟化物单晶的磁矩由有序变为杂乱，磁熵增加，从外界吸收能量。在样品绝热的情况下则表现为锂稀土氟化物单晶样品本身温度变化。
作为优选的技术方案：
所述锂稀土氟化物的化学式是LiREF4，其中RE为稀土元素。
所述稀土元素RE为钆(Gd)、铽(Tb)、镝(Dy)、钬(Ho)、铒(Er)、铥(Tm)和镱(Yb)之中的一种或多种。
所述锂稀土氟化物具有四方白钨矿的结构。
所述锂稀土氟化物为具有极强磁各向异性的单晶。
其中，LiGdF4、LiTbF4和LiHoF4的易磁化方向平行于C轴，LiDyF4、LiErF4、LiYbF4和LiTmF4的易磁化方向垂直于C轴。
LiGdF4表现出顺磁性，LiTmF4表现出范福莱克顺磁性，LiTbF4和LiHoF4分别在低于2.87K和1.53K的居里温度时表现出铁磁有序，LiDyF4、LiErF4和LiYbF4分别在低于0.62K、0.38K和0.128K的奈尔温度时表现出反铁磁有序。
锂稀土氟化物单晶的应用温度区间为低于20K的低温区间。
等温磁熵变ΔS是衡量一个磁卡材料性能好坏的重要参数。因此本发明采用超导量子干涉仪测量了锂稀土氟化物单晶样品的易磁化方向上的不同温度的磁化曲线。然后利用Maxwell关系式对所获得的不同温度的磁化曲线数据进行处理，并求出磁熵变随温度变化的关系。通过向锂稀土氟化物单晶样品的易磁化方向上施加一个0-20kOe小的变化磁场，锂稀土氟化物单晶表现出了大的等温磁熵变，其中LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4分在1.8K、4K、4K、1.8K、1.8K、1.8K和18K处获得50.35J·kg-1·K-1、21.12J·kg-1·K-1、24.98J·kg-1·K-1、24.45J·kg-1·K-1、21.95J·kg-1·K-1、14.7J·kg-1·K-1和0.692J·kg-1·K-1大小的等温磁熵变。
在固态磁制冷领域中，磁卡材料的热导率与装置整体的制冷效率息息相关。锂稀土氟化物单晶热导率的测试是通过综合物性测量系统的热输运选件进行的。由于锂稀土氟化物单晶样品的热导率在低温处较高，因此采用了四线法进行测量来减少误差，且样品的形状采用类针形的长方体形状，并采用降温测量的方法。LiTbF4和LiErF4在25K处的热导率达到了50W·K-1m-1。
一种基于锂稀土氟化物单晶的磁制冷方法，其特征在于：以锂稀土氟化物单晶作为磁工质，通过向磁工质施加和移除磁场，磁工质的温度发生 变化并与换热体实现热量的转移，从而达到制冷的目的。
作为优选的技术方案：
所述磁工质锂稀土氟化物单晶可为LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4之中的一种或多种；当为多种时，通过将不同的锂稀土氟化物单晶混合排列，实现低温制冷区间的扩展。
也可在制备锂稀土氟化物单晶的过程中掺入两种或两种以上的多种稀土元素(Gd、Tb、Dy、Ho、Er、Tm和Yb)，以实现低温制冷区间的扩展。
一种在小磁场驱动下的磁制冷装置，其特征在于，该装置包括锂稀土氟化物单晶作为磁工质。
作为优选的技术方案：
所述磁工质锂稀土氟化物单晶可为LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4之中的一种或多种；当为多种时，通过将不同的锂稀土氟化物单晶混合排列，实现低温制冷区间的扩展。
也可在制备锂稀土氟化物单晶的过程中掺入两种或两种以上的多种稀土元素(Gd、Tb、Dy、Ho、Er、Tm和Yb)，从而实现低温制冷区间的扩展。
该制冷装置还包括磁场施加部件，热开关，热沉，负载，其中磁场施加部件可选用永磁铁、电磁铁或超导磁体，优选永磁铁，可以有效简化装置体积，优化设计，热开关可选用机械接触式、超导式、气体式或磁阻式热开关，优选超导式热开关。
本发明的技术效果如下：
1、锂稀土氟化物单晶由于在低温处发生相变，因此当其作为磁制冷装 置中的磁工质时，可以使磁制冷装置的制冷温区处在小于20K的低温区间内。
2、锂稀土氟化物单晶具有极强的磁各向异性，在易磁化轴方向施加一个小磁场便可以达到饱和，而提供小磁场的部件，例如常见的永磁铁等价格便宜，体积小，不仅能够极大降低制冷装置的成本，而且能够优化制冷装置的设计，能够将磁制冷装置的应用范围扩展到大科学试验装置以及任何需要低温和极低温环境的装置和操作中。
3、本发明通过将多种锂稀土氟化物单晶混合排列，能够有效扩展制冷区间，满足不同的制冷区间的需求，进一步扩大应用范围。亦或是通过在制备锂稀土氟化物单晶过程中掺入一定量其它稀土元素(Gd、Tb、Dy、Ho、Er、Tm和Yb)，也可以实现制冷区间的拓宽。
4、相较于目前主流使用的Gd3Ga5O12的17.5J·kg-1·K-1的等温磁熵变。LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4分在1.8K、4K、4K、1.8K、1.8K、1.8K和18K处获得50.35J·kg-1·K-1、21.12J·kg-1·K-1、24.98J·kg-1·K-1、24.45J·kg-1·K-1、21.95J·kg-1·K-1、14.7J·kg-1·K-1和0.692J·kg-1·K-1大小的磁熵变。这些优异的性能使得锂稀土氟化物单晶完全能够代替这些主流材料，广泛应用于气体液化、极低温科学装置和航空航天等低温磁制冷领域，实现低成本、高效、无污染的低温磁制冷。锂稀土氟化物单晶在低温制冷区有着较高的热导率，其中，LiTbF4和LiErF4在25K处的热导率达到了50W·K-1·m-1，能够起到加快磁卡材料的换热速度，提升整体磁制冷装置效率的功效。
5、锂稀土氟化物单晶的制备工艺成熟，能够进行大规模的工业化生产， 极大降低了该材料的使用成本和制冷系统的制造成本，能够快速和广泛的推广应用。
附图说明
图1为锂稀土氟化物的晶体结构。
图2为磁制冷原理图。
图3为钆镓石榴石和沿锂稀土氟化物单晶易磁化轴方向施加0-10kOe变化磁场下的磁熵变曲线。
图4为钆镓石榴石和沿锂稀土氟化物单晶易磁化轴方向施加0-20kOe变化磁场下的磁熵变曲线。
图5为LiTbF4单晶的热导率随温度变化的关系。
图6为LiErF4单晶的热导率随温度变化的关系。
图7为磁制冷装置结构示意图。
具体实施方式
一种锂稀土氟化物单晶的应用装置，具体为一种在磁场驱动下的磁制冷装置，其磁工质选用锂稀土氟化物单晶，具体为LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4之中的一种或多种。
该装置还包括磁场施加部件，热开关，热沉(heat-sink)，负载(load)等。其中磁场施加部件可选用永磁铁、电磁铁或超导磁体；热开关可选用机械接触式、超导式、气体式或磁阻式热开关；负载的功能用于实现制冷；热沉起到散热功效。在初始状态下，锂稀土氟化物单晶在零磁场状态下与热沉的温度状态相同，然后在热开关保持关闭的状态下升高磁场，在等温磁化的过程中，热量由磁工质流向热沉，熵减小。待磁场升到最大时打开热 开关，随后降低磁场，磁工质温度降低至负载所需温度时仍保留有一些磁场，随着磁场的继续降低，磁工质将从负载处吸取热量为负载降温，从而达到降温的目的，实现整个装置的制冷功能。
当将多种不同的锂稀土氟化物单晶混合排列时，能有效扩展制冷区间范围。例如，一种实施方式中，将LiErF4和LiTbF4混合排列，使得制冷区间由单独LiErF4时的6K以下的温度区间扩展为15K以下的温度区间；另一种实施方式中，将LiDyF4和LiTbF4混合排列，使得制冷区间由单独LiDyF4时的4K以下的温度区间扩展为15K以下的温度区间；或者通过在制备锂稀土氟化物单晶过程中掺入一定量其它稀土元素(Gd、Tb、Dy、Ho、Er、Tm和Yb)，制备成包含两种及以上的多种稀土元素的锂稀土氟化物单晶时，也可以实现低温制冷区间的扩展。
下面的实施例分别对LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4进行磁卡性能测试，测试结果表明在小于20K的低温区间内，LiGdF4、LiTbF4、LiHoF4、LiDyF4和LiErF4均表现出优于传统GGG材料的17.5J·kg-1·K-1的等温磁熵变。其中，LiTbF4和LiErF4在低温区间内均表现出了达到50W·K-1m-1的热导率。
实施例1
LiGdF4单晶的磁卡性能测试
在磁性测试中，首先用手术刀从大块LiGdF4单晶样品中切出一小块样品，经过电子天平称量，样品质量为7.35mg。并利用双面胶将样品固定在塑料样品管中。接下来沿样品的易磁化方向进行M-H测试，1.8K的温度下测量一条M-H曲线，在2K-10K的温度范围内，每隔1K测量一条M-H曲 线。在10K-24K的温度范围内，每隔2K测量一条M-H曲线。在每条测试的M-H曲线中，在0-10kOe磁场下每隔500Oe测量一个数据点，在10kOe-20kOe磁场下每隔1000Oe测量一个数据点。
根据上面磁性测试所得不同温度下的M-H曲线，通过Maxwell方程式求得LiGdF4样品沿易磁化方向施加一个0-10kOe和0-20kOe变化磁场后的磁熵变随温度变化的关系。LiGdF4样品在0-20kOe变化磁场下获得50.35J·kg-1·K-1大小的磁熵变。
实施例2
LiTbF4单晶的磁卡性能测试
在磁性测试中，受限于仪器的测量范围，首先利用手术刀从大块LiTbF4单晶样品中切出一小块样品，经过电子天平称量，样品质量为5.4mg。并利用双面胶将样品固定在塑料样品管中。接下来沿样品的易磁化方向进行M-H测试(即磁化曲线测试)，在1.85K-2.85K的温度范围内，每隔0.2K测量一条M-H曲线。在4K-22K的温度范围内，每隔2K测量一条M-H曲线。在每条测试的M-H曲线中，在0-10kOe磁场下每隔500Oe测量一个数据点，在10kOe-20kOe磁场下每隔1000Oe测量一个数据点。
根据上面磁性测试所得不同温度下的M-H曲线，通过Maxwell方程式求得LiTbF4样品沿易磁化方向施加一个0-10kOe和0-20kOe变化磁场后的磁熵变随温度变化的关系。LiTbF4单晶样品在0-20kOe变化磁场下获得21.12J·kg-1·K-1大小的磁熵变。
在LiTbF4单晶样品的热导率测试中，通过综合物性测量系统的热输运 选件测试了LiTbF4样品沿C轴方向的热导率，样品的形状矩形。采取四线法进行测试，横截面积为9.63mm2，表面积为109.8mm3，电极间距为1.5mm，热辐射系数为1。测试的温度范围25K-50K，采取速率为0.1K/min的降温测试，随后获得LiTbF4样品的热导率随温度变化的关系，且在25K时热导率达到了50W·K-1·m-1。
实施例3
LiDyF4单晶的磁卡性能测试
在磁性测试中，首先用手术刀从大块LiDyF4单晶样品中切出一小块样品，经过电子天平称量，样品质量为1.48mg。并利用双面胶将样品固定在塑料样品管中。接下来沿样品的易磁化方向进行M-H测试，1.8K的温度下测量一条M-H曲线，在2K-10K的温度范围内，每隔1K测量一条M-H曲线。在10K-24K的温度范围内，每隔2K测量一条M-H曲线。在每条测试的M-H曲线中，在0-10kOe磁场下每隔500Oe测量一个数据点，在10kOe-20kOe磁场下每隔1000Oe测量一个数据点。
根据上面磁性测试所得不同温度下的M-H曲线，通过Maxwell方程式求得LiDyF4样品沿易磁化方向施加一个0-10kOe和0-20kOe变化磁场后的磁熵变随温度变化的关系。LiDyF4样品在0-20kOe变化磁场下获得24.45J·kg-1·K-1大小的磁熵变。
实施例4
LiHoF4单晶的磁卡性能测试
在磁性测试中，首先用手术刀从大块LiHoF4单晶样品中切出一小块样品，经过电子天平称量，样品质量为6.35mg。并利用双面胶将样品固定在塑料样品管中。接下来沿样品的易磁化方向进行M-H测试，1.8K的温度下测量一条M-H曲线，在2K-10K的温度范围内，每隔1K测量一条M-H曲线。在10K-24K的温度范围内，每隔2K测量一条M-H曲线。在每条测试的M-H曲线中，在0-10kOe磁场下每隔500Oe测量一个数据点，在10kOe-20kOe磁场下每隔1000Oe测量一个数据点。
根据上面磁性测试所得不同温度下的M-H曲线，通过Maxwell方程式求得LiHoF4样品沿易磁化方向施加一个0-10kOe和0-20kOe变化磁场后的磁熵变随温度变化的关系。LiHoF4单晶样品在0-20kOe的变化磁场下获得24.98J·kg-1·K-1大小的磁熵变。
实施例5
LiErF4单晶的磁卡性能测试
在磁性测试中，首先用手术刀从大块LiErF4单晶样品中切出一小块样品，经过电子天平称量，样品质量为2.55mg。并利用双面胶将样品固定在塑料样品管中。接下来沿样品的易磁化方向进行M-H测试，1.8K的温度下测量一条M-H曲线，在2K-10K的温度范围内，每隔1K测量一条M-H曲线。在10K-24K的温度范围内，每隔2K测量一条M-H曲线。在每条测试的M-H曲线中，在0-10kOe磁场下每隔500Oe测量一个数据点，在10kOe-20kOe磁场下每隔1000Oe测量一个数据点。
根据上面磁性测试所得不同温度下的M-H曲线，通过Maxwell方程式 求得LiErF4样品沿易磁化方向施加一个0-10kOe和0-20kOe变化磁场后的磁熵变随温度变化的关系。LiErF4样品在1.8K的温度和20kOe的变化磁场下获得21.95J·kg-1·K-1大小的磁熵变。
进行LiErF4单晶的热导率测试，其中，通过综合物性测量系统的热输运选件测试了LiErF4样品沿C轴方向的热导率，样品的形状为矩形。采取四线法进行测试，横截面积为9.3mm2，表面积为104.37mm3，电极间距为1.87mm，热辐射系数设为1。测试的温度范围25K-300K，采取速率为0.1K/min的降温测试，随后获得LiErF4样品的热导率随温度变化的关系，且在25K时热导率达到了50W·K-1·m-1。
实施例6
LiTmF4单晶的磁卡性能测试
在磁性测试中，首先用手术刀从大块LiTmF4单晶样品中切出一小块样品，经过电子天平称量，样品质量为82.63mg。并利用双面胶将样品固定在塑料样品管中。接下来沿样品的易磁化方向进行M-H测试，1.8K的温度下测量一条M-H曲线，在2K-10K的温度范围内，每隔1K测量一条M-H曲线。在10K-24K的温度范围内，每隔2K测量一条M-H曲线。在每条测试的M-H曲线中，在0-10kOe磁场下每隔500Oe测量一个数据点，在10kOe-20kOe磁场下每隔1000Oe测量一个数据点。
根据上面磁性测试所得不同温度下的M-H曲线，通过Maxwell方程式求得LiTmF4样品沿易磁化方向施加一个0-10kOe和0-20kOe变化磁场后的磁熵变随温度变化的关系。LiTmF4样品在0-20kOe的变化磁场下获得0.692 J·kg-1·K-1大小的磁熵变。
实施例7
LiYbF4单晶的磁卡性能测试
在磁性测试中，首先用手术刀从大块LiYbF4单晶样品中切出一小块样品，经过电子天平称量，样品质量为4.81mg。并利用双面胶将样品固定在塑料样品管中。接下来沿样品的易磁化方向进行M-H测试，1.8K的温度下测量一条M-H曲线，在2K-10K的温度范围内，每隔1K测量一条M-H曲线。在10K-24K的温度范围内，每隔2K测量一条M-H曲线。在每条测试的M-H曲线中，在0-10kOe磁场下每隔500Oe测量一个数据点，在10kOe-20kOe磁场下每隔1000Oe测量一个数据点。
根据上面磁性测试所得不同温度下的M-H曲线，通过Maxwell方程式求得LiYbF4样品沿易磁化方向施加一个0-10kOe和0-20kOe变化磁场后的磁熵变随温度变化的关系。LiYbF4样品在0-20kOe的变化磁场下获得14.7J·kg-1·K-1大小的磁熵变。
上述实施例只为说明本发明的技术构思及特点，其目的在于让熟悉此项技术的人士能够了解本发明的内容并据以实施，并不能以此限制本发明的保护范围。凡根据本发明精神实质所作的等效变化或修饰，都应涵盖在本发明的保护范围之内。
此外，本文省略了对公知结构和技术的描述，以避免不必要地混淆本发明的概念。

Claims (17)

  1. 一种锂稀土氟化物单晶在磁制冷中的应用。
  2. 根据权利要求1所述的应用，其特征在于：所述锂稀土氟化物的化学式是LiREF4，其中RE为稀土元素。
  3. 根据权利要求2所述的应用，其特征在于：所述稀土元素RE为钆、铽、镝、钬、铒、铥和镱之中的一种或多种。
  4. 根据权利要求3所述的应用，其特征在于：所述锂稀土氟化物具有四方白钨矿的结构，是具有磁各向异性的单晶。
  5. 根据权利要求4所述的应用，其特征在于：LiGdF4、LiTbF4和LiHoF4的易磁化方向平行于C轴，LiDyF4、LiErF4、LiYbF4和LiTmF4的易磁化方向垂直于C轴。
  6. 根据权利要求3所述的应用，其特征在于：LiGdF4表现出顺磁性，LiTmF4表现出范福莱克顺磁性，LiTbF4和LiHoF4分别在低于2.87K和1.53K的居里温度时表现出铁磁有序，LiDyF4、LiErF4和LiYbF4分别在低于0.62K、0.38K和0.128K的奈尔温度时表现出反铁磁有序。
  7. 根据权利要求1-4任一项所述的应用，其特征在于：锂稀土氟化物单晶的应用温度区间为低于20K的低温区间。
  8. 根据权利要求1-4任一项所述的应用，其特征在于：在沿锂稀土氟化物单晶样品的易磁化方向施加0-20kOe的变化磁场，锂稀土氟化物单晶表现出了大的等温磁熵变，其中LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4分在1.8K、4K、4K、1.8K、1.8K、1.8K和18K处获得50.35J·kg-1·K-1、21.12J·kg-1·K-1、24.98J·kg-1·K-1、24.45J·kg-1·K-1、21.95 J·kg-1·K-1、14.7J·kg-1·K-1和0.692J·kg-1·K-1大小的等温磁熵变。
  9. 根据权利要求5所述的应用，其特征在于：LiTbF4和LiErF4在25K处的热导率达到50W·K-1·m-1。
  10. 一种基于锂稀土氟化物单晶的磁制冷方法，其特征在于：以锂稀土氟化物单晶作为磁工质，通过向磁工质施加和移除磁场，磁工质的温度发生变化并与换热体实现热量的转移，从而达到制冷的目的。
  11. 根据权利要求10所述的磁制冷方法，其特征在于：所述锂稀土氟化物单晶为LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4之中的一种或多种；
    当为多种时，通过将不同的锂稀土氟化物单晶混合排列，实现低温制冷区间的扩展。
  12. 根据权利要求10所述的磁制冷方法，其特征在于：所述锂稀土氟化物的化学式是LiREF4，其中RE为稀土元素，且RE取自Gd、Tb、Dy、Ho、Er、Tm和Yb中的至少两种以上的稀土元素，以实现低温制冷区间的扩展。
  13. 一种在小磁场驱动下的磁制冷装置，其特征在于，该装置包括锂稀土氟化物单晶作为磁工质。
  14. 根据权利要求13所述的磁制冷装置，其特征在于：磁工质锂稀土氟化物单晶为LiGdF4、LiTbF4、LiHoF4、LiDyF4、LiErF4、LiYbF4和LiTmF4之中的一种或多种；
    当为多种时，通过将不同的锂稀土氟化物单晶混合排列，实现低温制冷区间的扩展。
  15. 根据权利要求13所述的磁制冷装置，其特征在于：所述锂稀土氟化物的化学式是LiREF4，其中RE为稀土元素，且RE取自Gd、Tb、Dy、Ho、Er、Tm和Yb中的至少两种以上的稀土元素。
  16. 根据权利要求13所述的磁制冷装置，其特征在于：该制冷装置还包括磁场施加部件，热开关，热沉，负载。
  17. 根据权利要求13所述的磁制冷装置，其特征在于：所述磁制冷装置中磁场施加部件选用永磁铁，热开关选用超导式热开关。
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