High-purity rare earth oxide block material with intrinsic magnetoelectric property as well as preparation method and application of high-purity rare earth oxide block material

Abstract

The invention belongs to the technical field of rare earth functional materials, and particularly relates to a high-purity rare earth monoxide block material with intrinsic magnetoelectric properties and a preparation method and application of the high-purity rare earth monoxide block material. The preparation method comprises the following steps that S1, in an inert gas atmosphere, lanthanum oxide and lanthanum metal are mixed and pressed into a prefabricated block; s2, the prefabricated block is put into a multi-surface jacking machine, the pressure is increased to 4.5-5.5 GPa, and the pressure is maintained; and then the temperature is increased to 1473-1573 K at the speed of 100-200 K / min, heat preservation is carried out, and the rare earth monoxide block material is prepared and obtained. The rare earth oxide block material prepared by the invention has a pure NaCl type crystal structure, and the impurity phase content is less than or equal to 3%; in addition, the super-conduction critical temperature is high, and the superconductor volume is close to 100%.

Description

Technical Field

[0001] This invention belongs to the technical field of rare earth functional materials, and more specifically, relates to a high-purity rare earth monoxide bulk material with intrinsic magnetoelectric properties, its preparation method, and its application. Background Technology

[0002] Rare earth oxides (REOs) possess multiple magnetoelectric properties, including superconductivity and magnetism, due to their unique NaCl-type crystal structure and 4f / 5d electronic configuration. They are core candidate materials for fields such as superconducting electronics and magnetic storage. Among them, LaO is the most promising material for research and application in this system.

[0003] However, in the existing technology, there are three major defects in the preparation and application of LaO: (1) Morphological limitations and lattice distortion problems: Most of the reported LaO is prepared by epitaxial growth in the form of thin films (such as growth on yttrium aluminum oxide (YAlO3) substrates); due to the significant lattice mismatch between the thin film and the substrate, the thin film has a structural distortion of c / a≠1, and the magnetoelectric properties are seriously deviated from the intrinsic values ​​(such as the superconducting critical temperature of LaO thin film is only 4.25-5.24K, which is lower than the intrinsic value of bulk materials), which cannot meet the requirements of actual devices for the intrinsic properties of materials. (2) Low purity of bulk rare earth oxide preparation: the existing bulk preparation method (belt high pressure press) is difficult to suppress the generation of impurity phases, and impurities such as lanthanum oxide (La2O3) and rare earth metals are easily introduced into the product, and the impurity phase content generally exceeds 5%; and bulk LaO only exhibits metallic properties and no superconducting properties have been found. (3) The preparation process is difficult to scale up: Existing processes such as pulsed laser deposition (PLD) have problems of high cost and low output, and can only prepare a small number of samples at a time; belt high pressure press is prone to introducing impurities, resulting in low product qualification rate and failing to meet the needs of industrial production.

[0004] Therefore, existing technologies cannot simultaneously solve the problems of high purity and low superconducting critical temperature of rare earth monoxide bulk materials. There is an urgent need to develop a reliable large-scale preparation process to achieve the preparation of high-purity rare earth monoxide bulk materials. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, the primary objective of this invention is to provide a method for preparing rare earth monoxide bulk materials.

[0006] The second objective of this invention is to provide a rare earth oxide bulk material prepared by the above-described preparation method.

[0007] The third objective of this invention is to provide the application of rare earth oxide bulk materials in superconducting devices.

[0008] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0009] This invention claims protection for a method for preparing a rare earth monoxide bulk material, comprising the following steps: S1. Lanthanum oxide and lanthanum metal are mixed and pressed into preforms in an inert gas atmosphere; S2. The preformed block is placed in a multi-faceted press, pressurized to 4.5-5.5 GPa, and held at that pressure; then the temperature is increased to 1473-1573 K at a rate of 100-200 K / min and held at that temperature to prepare rare earth monoxide bulk material.

[0010] This invention utilizes a multi-faceted press to achieve precise high-temperature, high-pressure (HPHT) synthesis. A preform of lanthanum oxide and lanthanum metal is heated to a specific temperature range at a specific pressure range using a specific heating rate, successfully preparing a pure NaCl-type crystal structure rare-earth oxide bulk material (LaO bulk material). The specific high-pressure environment suppresses impurity phase formation; while the specific heating rate and high temperature range better promote atomic diffusion and complete reaction, allowing lanthanum oxide and lanthanum metal to fully react and generate the target product. Furthermore, this method avoids bulk cracking or lattice distortion caused by abrupt temperature / pressure changes.

[0011] The LaO bulk material prepared by this invention has an impurity phase content of ≤3% and exhibits a pure NaCl-type crystal structure, achieving intrinsic structural control. The superconducting critical temperature of the LaO bulk material prepared by the above method of this invention is increased by more than 20% compared to existing thin film samples, and the superconducting volume is close to 100%. This invention employs a multi-faceted top-pressing machine for preparation, ensuring controllable process parameters and performance; it has advantages such as short preparation cycle, controllable raw material costs, and suitability for industrial-scale production.

[0012] Preferably, in step S1, the molar ratio of lanthanum oxide to lanthanum metal is 1:1-1.05.

[0013] Preferably, in step S1, the mixing and pressing pressure is 5-8 MPa. More preferably, the mixing and pressing pressure is 5-6 MPa.

[0014] Preferably, in step S1, the dimensions of the precast block are: diameter 0.55-0.60cm; height 0.70-0.80cm.

[0015] Preferably, in step S1, the purity of the lanthanum oxide is ≥99.99%; and / or the purity of the lanthanum metal is ≥99.7%. High-purity raw materials are more conducive to avoiding the generation of impurities during the preparation process, and can also prevent impurities in the raw materials from remaining in the final rare earth monooxide bulk material, thus avoiding a decrease in the purity of the product.

[0016] Preferably, step S1 further includes a pretreatment step of the lanthanum oxide; the pretreatment operation is to anneal the lanthanum oxide at 1173-1273 K in an air atmosphere. Pretreatment removes adsorbed water and trace impurities from the surface of the lanthanum oxide raw material, thereby improving the purity of the final rare earth monooxide bulk material and reducing the content of impurity phases.

[0017] Preferably, in step S2, the pressure boosting rate is 0.3-1 GPa / min. More preferably, in step S2, the pressure boosting rate is 0.5-0.8 GPa / min.

[0018] Preferably, in step S2, the heat preservation time is 2-3 hours.

[0019] Preferably, in step S2, the multi-faceted top press selects pyrophyllite and boron nitride as the pressure transmission medium to ensure uniform pressure transmission and avoid reaction with the sample.

[0020] Preferably, the multi-face press can be a six-face press, an eight-face press, etc.

[0021] Preferably, the inert gas includes, but is not limited to, argon.

[0022] Furthermore, this invention seeks protection for the rare earth oxide bulk material prepared by the above preparation method.

[0023] Furthermore, this invention claims protection for the application of rare-earth oxide bulk materials in superconducting devices. Specifically, applications include, for example, in low-temperature superconducting devices or superconducting devices operating in high-pressure extreme environments.

[0024] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing bulk rare-earth monoxide materials. The method employs a multi-faceted press combined with a specific preparation process, resulting in bulk rare-earth monoxide materials with a pure NaCl-type crystal structure, impurity phase content ≤3%, a high superconducting critical temperature, and a superconducting volume approaching 100%. The preparation method provided by this invention has a short cycle time, can be mass-produced, and the prepared bulk rare-earth monoxide materials fully exhibit the intrinsic magnetoelectric properties of rare-earth monoxides. Attached Figure Description

[0025] Figure 1 The image shows the XRD pattern of the LaO bulk material prepared in Example 1.

[0026] Figure 2 The graph shows the physical property measurements of the LaO bulk material prepared in Example 1. Figure 2 In the figure, 'a' represents the resistance of the LaO bulk material as a function of temperature (the inset is a magnified view of the low-temperature region). Figure 2 b in the figure represents the H curve of LaO bulk material measured below the Curie temperature (Tc), with the measured magnetic field range being 0-1 T; the inset shows the M(H) curve at 2 K temperature within an extended magnetic field range of -1 to 1 T. Figure 2 In this context, c represents the relationship between the superconducting volume fraction of the LaO bulk material and temperature. Figure 2 In this context, d represents the upper critical magnetic field H of the LaO bulk material. c2 Relationship with temperature.

[0027] Figure 3 The images show the XRD patterns of the LaO bulk materials prepared in Comparative Examples 1 and 2. Figure 3 In the figure, 'a' is the XRD pattern of the LaO bulk material prepared in Comparative Example 1; Figure 3 In the figure, b is the XRD pattern of the LaO bulk material prepared in Comparative Example 2 (the inset is a comparison of the actual sample images of the LaO bulk material prepared in Example 1 and the LaO bulk material prepared in Comparative Example 2). Detailed Implementation

[0028] The present invention will be further described below with reference to the specification and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0029] Lanthanum oxide (La2O3) powder: purity 99.999%, purchased from Macklin.

[0030] Lanthanum (La) particles: 99.7% purity, 40 mesh, purchased from Alfa Aesar.

[0031] Example 1: LaO bulk material and its preparation (1) Raw material pretreatment: La2O3 powder was annealed at 1273K in air atmosphere for 10h to remove adsorbed water and trace impurities on the surface; after annealing, it was transferred to a glove box filled with argon (oxygen content ≤0.1ppm, water content ≤0.1ppm); metallic La particles were directly placed into the glove box.

[0032] (2) Mixing and pressing: Weigh out La2O3 powder (0.210g, 0.00065mol) and metallic La particles (0.0945g, 0.00068mol, 5% excess) according to the ratio. Put the weighed La2O3 powder and metallic La particles into an agate mortar and grind for 40min until the particle size is ≤3μm to ensure that the raw materials are mixed evenly.

[0033] (3) Press molding: In an argon-filled glove box, the powder mixed evenly in step (2) is placed into a cylindrical mold and pressed into a preform using a hydraulic press at a pressure of 5 MPa. The preform has a diameter of 0.55 cm and a height of 0.3 cm. After pressing, the density of the preform reaches 25% of the theoretical density.

[0034] (4) HPHT synthesis: The preform was loaded into the boron nitride (BN) sample chamber of a 420-type six-sided top press and the corresponding pyrophyllite device was assembled. The pressure was raised to 5 GPa within 10 min and held for 5 min to stabilize the pressure. The temperature was raised to 1573 K at a heating rate of 100 K / min and held for 3 h. After the holding period, the temperature was quenched to room temperature. Then the pressure was slowly reduced to normal pressure within 15 min to avoid cracking of the material due to sudden pressure change. LaO bulk material was prepared.

[0035] (5) Post-processing: Remove the sample chamber, break the chamber, scrape off the BN and impurities remaining on the surface of the block with an agate knife, and transfer it to a glove box for storage.

[0036] Example 2: LaO bulk materials and their preparation The difference between this embodiment and embodiment 1 is that in step (4), the temperature is increased to 1473K at a heating rate of 100K / min and held for 3h.

[0037] Example 3: LaO bulk materials and their preparation The difference between this embodiment and embodiment 1 is that in step (4), the temperature is increased to 1500K at a heating rate of 100K / min and held for 3 hours.

[0038] Example 4: LaO bulk materials and their preparation The difference between this embodiment and embodiment 1 is that in step (4), the pressure is increased to 4.5 GPa within 10 minutes.

[0039] Example 5: LaO bulk materials and their preparation The difference between this embodiment and embodiment 1 is that in step (4), the pressure is increased to 5.5 GPa within 10 minutes.

[0040] Example 6: LaO bulk material and its preparation The difference between this embodiment and embodiment 1 is that in step (4), the temperature is increased to 1573K at a heating rate of 200K / min.

[0041] Comparative Example 1 The difference between this comparative example and Example 1 is that in step (4), the temperature is increased to 1373K at a heating rate of 100K / min and held for 3h.

[0042] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (4), the temperature is increased to 1573K at a heating rate of 70K / min and held for 3h.

[0043] Test Example 1 (1) The LaO bulk material prepared in Example 1 was tested using an X-ray diffractometer (MiniFlex 600, Rigaku, Japan) and a physical property measurement system (PPMS-9T).

[0044] (2) Figure 1 The image shows the XRD pattern of the LaO bulk material prepared in Example 1. Figure 1 As shown, the XRD pattern indicates that the LaO bulk material has a pure NaCl type structure, space group Fm-3m, lattice parameter a=5.14517 (2) Å, and impurity phase content of 2.7%. The impurity phase content of the LaO bulk materials prepared in Examples 2-5 is similar to that of the LaO bulk material in Example 1, with no significant difference.

[0045] Figure 2 The graph shows the physical property measurements of the LaO bulk material prepared in Example 1. Figure 2 As shown, the LaO bulk material prepared in Example 1 under ambient pressure has a Tc of 6.05 K, a superconducting volume greater than 98%, and is a type II superconductor. C2 (0) = 3.32T. It can be seen that the LaO bulk material prepared in Example 1 has excellent superconducting properties, and the superconducting critical temperature is increased by more than 20% compared with the existing LaO thin film samples (Tc is about 4-5K).

[0046] Test Example 2 (1) The LaO bulk materials prepared in Comparative Example 1 and Comparative Example 2 were tested using an X-ray diffractometer (MiniFlex 600, Rigaku, Japan) and a physical property measurement system (PPMS-9T).

[0047] (2) Figure 3 XRD patterns of the LaO bulk materials prepared for Comparative Examples 1 and 2. Figure 3 As shown in a, the LaO bulk material prepared in Comparative Example 1 shows a large number of raw material impurity phase diffraction peaks, with an impurity content close to 10%.

[0048] Depend on Figure 3 As shown in Figure b, the sample prepared in Example 1 has a color that is visually different from the LaO bulk material prepared in Comparative Example 2. The LaO bulk material prepared in Comparative Example 2 exhibits a large number of impurity phase diffraction peaks, and the target sample was not synthesized.

[0049] The foregoing examples are merely illustrative, used to explain some features of the method described in this invention. The appended claims are intended to claim the broadest possible scope, and the embodiments presented herein are demonstrated by the applicant's actual experimental results. Therefore, the applicant intends that the appended claims are not limited by the selection of examples illustrating the features of the invention. Some numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. A method for preparing a rare earth monoxide bulk material, characterized in that, Includes the following steps: S1. Lanthanum oxide and lanthanum metal are mixed and pressed into preforms in an inert gas atmosphere; S2. The preformed block is placed in a multi-faceted press, pressurized to 4.5-5.5 GPa, and held at that pressure; then the temperature is increased to 1473-1573 K at a rate of 100-200 K / min and held at that temperature to prepare rare earth monoxide bulk material.

2. The preparation method according to claim 1, characterized in that, In step S1, the molar ratio of lanthanum oxide to lanthanum metal is 1:1-1.

05.

3. The preparation method according to claim 1, characterized in that, In step S1, the pressure for mixing and pressing is 5-8 MPa.

4. The preparation method according to claim 1, characterized in that, In step S1, the purity of lanthanum oxide is ≥99.99%; and / or the purity of lanthanum metal is ≥99.7%.

5. The preparation method according to claim 1, characterized in that, Step S1 further includes a step of pretreating the lanthanum oxide; the pretreating operation is to anneal the lanthanum oxide at 1173-1273K in an air atmosphere.

6. The preparation method according to claim 1, characterized in that, In step S2, the rate of pressure increase is 0.3-1 GPa / min.

7. The preparation method according to claim 1, characterized in that, In step S2, the heat preservation time is 2-3 hours.

8. The preparation method according to claim 1, characterized in that, The impurity phase content of rare earth monoxide bulk materials is ≤3%.

9. The rare earth oxide bulk material prepared by the preparation method according to any one of claims 1-8.

10. The application of the rare earth oxide bulk material of claim 9 in superconducting devices.

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