Magnetoresistance thin film preparation core-shell structure rare earth oxide / gallium oxide composite particles and preparation method thereof
By preparing core-shell structured rare earth oxide/gallium oxide composite particles, the problems of compositional inhomogeneity and evaporation instability of rare earth oxide and gallium metal composite films in thermal resistance evaporation technology were solved, and high-quality film preparation was achieved, which is suitable for thermal resistance evaporation of magnetoresistive films.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- KUNMING UNIV OF SCI & TECH
- Filing Date
- 2026-04-22
- Publication Date
- 2026-06-19
AI Technical Summary
In existing thermal resistance evaporation technology, the raw materials for evaporation of rare earth oxide and gallium metal composite thin films suffer from problems such as component fractionation, unstable evaporation, and easy explosion and splashing, resulting in uneven film composition and poor stability.
Rare earth oxide/gallium oxide composite particles with a core-shell structure are prepared by a sol-gel method and a low-temperature sintering process. The core is a rare earth oxide precursor powder and the outer shell is gallium oxide. The core and the outer shell are tightly coated to form a clear interface of 5nm~200nm and a coating area of 50%~80%, achieving synchronous melting and uniform evaporation.
It solves the problems of stratification and segregation caused by traditional mixing methods, improves the stability and reproducibility of vapor deposition airflow, is suitable for existing thermal resistance vapor deposition equipment, requires no modification, and provides flexibility for up to 31 component variations.
Smart Images
Figure CN122233438A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional composite materials and physical vapor deposition technology, specifically relating to a rare earth oxide / gallium oxide composite particle with a core-shell structure for the preparation of magnetoresistive thin films and its preparation method, which is particularly suitable as a evaporation source material for the preparation of magnetoresistive effect composite thin films by thermal resistance evaporation. Background Technology
[0002] Rare earth oxide materials (such as La) 1-x Ca x TmO3 (where Tm represents transition metal elements such as V, Cr, Mn, Fe, and Co) can exhibit a significant magnetoresistance effect through doping with rare earth / alkaline earth metal ions at the A-site and transition metal ions at the B-site, showing great promise for applications in magnetic storage, magnetic sensing, and spintronic devices. Combining rare earth oxides with gallium oxide to form heterostructures holds promise for obtaining novel magnetoresistance functional materials through interfacial coupling effects.
[0003] In the field of thin film preparation, thermal resistance evaporation technology has become a promising physical vapor deposition method due to its advantages such as simple equipment structure, high vacuum degree, and controllable deposition rate. However, when applying thermal resistance evaporation technology to the preparation of rare earth oxide / gallium oxide composite thin films, a key material science problem is faced: the morphology and properties of the evaporation raw materials directly determine the stability of the evaporation process and the uniformity of the film composition. In the existing technology, the evaporation raw materials are usually single-component block or powder materials. For multi-component oxide composite systems, when using rare earth oxide powder and gallium metal blocks directly as evaporation sources, the following problems exist: (1) The melting points and saturated vapor pressures of the two materials are significantly different, making it difficult to achieve synchronous evaporation and uniform co-deposition growth; (2) Conventional block evaporation sources are prone to bursting and splashing due to thermal stress during heating, resulting in unstable evaporation gas flow and defects on the film surface; (3) After simple mixing of rare earth oxide powder and liquid gallium metal, due to the large density difference, it is easy to stratify or agglomerate in the evaporation boat, further aggravating the composition inhomogeneity.
[0004] To address the aforementioned issues, a composite evaporation material specifically designed for thermal resistance evaporation needs to be developed. This material should enable the close and uniform pre-composite formation of rare earth oxides and metallic gallium at the microscale, and allow for simultaneous melting and uniform evaporation during heating, thus providing a reliable material basis for the preparation of high-quality composite thin films. However, there are currently no reports on such dedicated composite particles and their preparation methods. Summary of the Invention
[0005] The present invention aims to provide a rare earth oxide / gallium oxide composite particle with a core-shell structure for the preparation of magnetoresistive thin films and its preparation method, so as to solve the problems of component fractionation, unstable evaporation, and easy explosion and splashing of multi-component evaporation raw materials in the existing thermal resistance evaporation technology.
[0006] To achieve the above objectives, the present invention provides the following technical solution: A rare earth oxide / gallium oxide composite particle with a core-shell structure, characterized in that the composite particle comprises: The core is a rare earth oxide precursor powder, the chemical composition of which is La. 1-x Ca x TmO3, where 0 < x <1, Tm is selected from any one or at least two of V, Cr, Mn, Fe, and Co; The outer shell covers the surface of the core, and the outer shell is made of gallium oxide.
[0007] The composite particles have a particle size of 10 μm to 100 μm, the interface thickness between the shell and the core is 5 nm to 200 nm, and the shell covers 50% to 80% of the core area.
[0008] Furthermore, Tm can be any one of V, Cr, Mn, Fe, and Co; or a combination of any two, three, four, or all five of V, Cr, Mn, Fe, and Co.
[0009] Furthermore, Tm selects any one of the aforementioned transition metal elements as a single component, corresponding to the material systems La. 1-x Ca x VO3, La 1-x Ca x CrO3, La 1-x Ca x MnO3, La 1-x Ca x FeO3, La 1-x Ca x CoO3.
[0010] The Tm is selected from any two combinations of the aforementioned transition metal elements. Specifically, the material systems corresponding to any two combinations of transition metal elements are La. 1-x Ca x (V,Cr)O3, La 1-x Ca x (V,Mn)O3、La 1-x Ca x (V,Fe)O3, La 1-x Ca x (V,Co)O3、La 1-x Ca x (Cr,Mn)O3, La 1-xCa x (Cr,Fe)O3, La 1-x Ca x (Cr,Co)O3, La 1-x Ca x (Mn,Fe)O3, La 1-x Ca x (Mn,Co)O3, La 1-x Ca x (Fe,Co)O3.
[0011] The Tm is selected from any three combinations of the aforementioned transition metal elements. Specifically, the material systems corresponding to any three combinations of transition metal elements are La. 1-x Ca x (V,Cr,Mn)O3, La 1-x Ca x (V,Cr,Fe)O3, La 1-x Ca x (V,Cr,Co)O3, La 1-x Ca x (V,Mn,Fe)O3, La 1-x Ca x (V,Mn,Co)O3、La 1-x Ca x (V,Fe,Co)O3, La 1-x Ca x (Cr,Mn,Fe)O3, La 1-x Ca x (Cr,Mn,Co)O3, La 1-x Ca x (Cr,Fe,Co)O3, La 1-x Ca x (Mn,Fe,Co)O3.
[0012] The Tm is selected from any four combinations of the aforementioned transition metal elements. Specifically, the material systems corresponding to any four combinations of transition metal elements are La. 1-x Ca x (V,Cr,Mn,Fe)O3, La 1-x Ca x (V,Cr,Mn,Co)O3, La 1-x Ca x (V,Cr,Fe,Co)O3, La 1-x Ca x (V,Mn,Fe,Co)O3, La 1-x Ca x (Cr,Mn,Fe,Co)O3.
[0013] The Tm is selected from any 5 combinations of the aforementioned transition metal elements. Specifically, the material system corresponding to any 5 combinations of transition metal elements is La. 1-x Ca x (V,Cr,Mn,Fe,Co)O3.
[0014] Therefore, there are a total of 31 rare earth oxide components.
[0015] A method for preparing the above-mentioned composite particles includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to chemical composition La 1-x Ca x TmO3 was weighed and chemical reagents were used to prepare rare earth oxide precursor powder with a particle size of 0.3 μm to 5 μm through sol-gel method and sintering process; (2) Preparation of homogeneous mixed suspension of liquid gallium metal: Melt gallium metal with a purity of ≥99.9% to obtain a liquid gallium metal solution, add an alcohol dispersion medium to it, and disperse by ultrasonication to obtain a homogeneous mixed suspension containing liquid gallium metal droplets with a particle size of 50 nm~200 nm; (3) Preparation of core-shell structured precursor particles: The rare earth oxide precursor powder obtained in step (1) is sprinkled into the homogeneous mixed suspension of liquid gallium metal obtained in step (2) so that the surface of the precursor powder is wetted, and a precursor powder / liquid gallium metal mixture is obtained. The mass ratio between the precursor powder and the homogeneous mixed suspension of liquid gallium metal is 1:1 to 1:10. After stirring, standing, and ultrasonic dispersion treatment, particles with good coating effect and a precursor powder / liquid gallium metal core-shell structure are obtained, wherein the core is rare earth oxide precursor powder, the shell is liquid gallium metal, the coating area ratio is 60% to 90%, and the particle size is 1 μm to 10 μm; (4) Sintering to obtain composite particles: The precursor particles with core-shell structure obtained in step (3) are sintered at 300 ℃~700 ℃ for 1 h~10 h under inert atmosphere or vacuum conditions to transform the liquid metal gallium shell into a gallium oxide shell, thereby obtaining the composite particles.
[0016] Further, step (1) specifically includes: dissolving the chemical in a mixed solvent of deionized water and alcohol solvent, adding an appropriate amount of dispersant I and complexing agent, and adjusting the volume to 90 ml to 800 ml; after fully dissolving by magnetic stirring, heating and stirring at 70 ℃ to 100 ℃ and 200 rpm to 500 rpm for 0.5 h to 2 h to form a wet gel and drying and solidifying it to obtain a dry gel; dehydrating the dry gel at 120 ℃ to 170 ℃ for 5 h to 72 h to obtain a dry gel block; grinding for 1 h to 3 h to obtain a dry gel powder; wherein, the alcohol solvent is any one of anhydrous ethanol, methanol or glycerol, and the volume ratio of alcohol solvent to deionized water is 2:1 to 5:1; the dispersant I is ethylene glycol, and the complexing agent is any one of calcium acetate, calcium chloride or citric acid.
[0017] Further, the chemical reagents mentioned in step (1) are lanthanum nitrate, calcium nitrate, and at least one selected from ammonium metavanadate, chromium nitrate, manganese nitrate, iron nitrate, and cobalt nitrate; the heating rate of the sintering process is 1 ℃ / min~15 ℃ / min, the sintering temperature is 400 ℃~1000 ℃, and the sintering time is 8 h~16 h.
[0018] Further, the melting temperature in step (2) is 30℃~40℃, and the melting time is 10 min~15 min; the alcohol dispersion medium is any one of anhydrous ethanol, ethylene glycol, and glycerol, and the volume ratio of the alcohol dispersion medium to the liquid gallium solution is 1:1~10:1.
[0019] Further, in step (3), the spreading rate is 0.05 g / s to 1 g / s, and the difference in the distribution of precursor powder during spreading is ≤5%; the stirring is carried out at a constant temperature of 25 ℃ to 35 ℃, the stirring rate is 200 rpm to 800 rpm, and the stirring time is 30 min to 100 min, so as to obtain precursor powder / liquid gallium particles with preliminary coating effect at the microscopic level, with a coating area ratio of 20% to 40%; after stirring, dispersant II is added dropwise at a constant temperature of 25 ℃ to 35 ℃, and the mixture is allowed to stand for 10 min to 60 min. The settled precursor powder / liquid gallium mixture is transferred to an ultrasonic disperser for multi-stage ultrasonic dispersion, which reduces the probability of particle agglomeration on the one hand and improves the coating effect on the other. The dispersant II can be oleic acid or ethylene glycol. The mass of dispersant II added is 0.1% to 0.3% of the total mass of the precursor powder / liquid gallium metal mixture, and the dropping rate of dispersant II is 0.05 ml / min to 0.1 ml / min.
[0020] Furthermore, in step (3), the ultrasonic dispersion is a multi-stage ultrasonic dispersion, with each stage having an ultrasonic frequency of 20kHz~40kHz, a power of 150w~300w, a duration of 15min~30min, and a number of stages of 3~8 times. Stirring is performed between each stage of ultrasonic dispersion, with a stirring rate of 100rpm~300rpm and a stirring duration of 3min~5min.
[0021] Furthermore, in step (4), before sintering, the precursor particles with the core-shell structure are separated from the mixture by an inert ceramic scraper and dried in a glove box with oxygen and water content ≤10 ppm. The drying temperature is 80 ℃~100 ℃ and the drying time is 1 h~3 h.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention uses rare earth oxide precursor powder as the core and gallium oxide as the shell to form core-shell composite particles. This structure enables the two materials to achieve close pre-composite bonding at the microscale, forming a clear interface with a thickness of 5nm~200nm between the core and the shell, with a coverage area ratio of 50%~80%. This ensures that the composite particles can melt synchronously and evaporate uniformly during the subsequent thermal resistance evaporation process, effectively overcoming the layering and segregation problems caused by density and melting point differences in traditional physical mixing methods.
[0023] (2) The particle size of the composite particles of the present invention is controlled within the range of 10 μm to 100 μm, which has good flowability and dispersibility and is easy to spread evenly in the evaporation boat. During the heating and evaporation process, the outer shell gallium oxide wraps the core, which prevents the rare earth oxide powder from directly bursting and splashing, and significantly improves the stability and reproducibility of the evaporation gas flow.
[0024] (3) The preparation method of the present invention (sol-gel method for preparing precursor powder → liquid gallium metal coating → low-temperature sintering) has a wide process window, moderate cost, requires no complex equipment, and is easy to scale up for production. The resulting composite particles can be directly adapted to existing thermal resistance evaporation equipment without any modification to the equipment.
[0025] (4) The core of the composite particles of the present invention can accommodate La 1-x Ca x The TmO3 system has up to 31 different compositional variations (including single transition metal elements or combinations of multiple elements), which can meet different magnetoresistive performance requirements and provide great flexibility for the performance control of subsequent thin film materials. Attached Figure Description
[0026] To more clearly illustrate the technical solutions involved in the embodiments of the present invention or the prior art, the accompanying drawings included in the description of the embodiments or the prior art will be briefly introduced below. It should be noted that these drawings only show some specific embodiments recorded in the present invention and do not cover all possible implementations.
[0027] Figure 1 is a process flow diagram for preparing composite particles.
[0028] Figure 2 shows the X-ray diffraction pattern of Example 1.
[0029] Figure 3 is the MR curve of Example 1.
[0030] Figure 4 shows the SEM image of Example 1 at a magnification of ×100000.
[0031] Figure 5 shows the SEM image of Example 2 at a magnification of ×50000.
[0032] Figure 6 shows the SEM image of Example 3 at a magnification of ×20000.
[0033] Figure 7 is a planar view of the atomic force microscope in Example 1.
[0034] Figure 8 is a three-dimensional atomic force microscope image of Example 1. Detailed Implementation
[0035] The technical solution of the present invention will now be described in detail and comprehensively. It should be noted that the embodiments described are only a part of the present invention and do not cover all embodiments. Furthermore, all other embodiments that can be obtained by those skilled in the art based on the embodiments provided by the present invention without creative effort should also fall within the protection scope of the present invention. In the following embodiments, unless otherwise specified, the instruments and materials used are commercially available.
[0036] Example 1: A core-shell structured rare earth oxide / gallium oxide composite particle for magnetoresistive thin film preparation and its preparation method, wherein the composite particle comprises: The core is a rare earth oxide precursor powder, the chemical composition of which is La. 0.7 Ca 0.3 MnO3, x The value is 0.3, and the Tm transition metal element is Mn. The outer shell covers the surface of the core, and the outer shell is made of gallium oxide.
[0037] A method for preparing core-shell structured rare earth oxide / gallium oxide composite particles for magnetoresistive thin film fabrication includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to La 0.7 Ca 0.3 Lanthanum nitrate, calcium nitrate, and manganese nitrate were weighed out according to the stoichiometric ratio of MnO3. These chemicals were dissolved in a mixture of anhydrous ethanol and deionized water in a volume ratio of 3:1. Ethylene glycol was added as dispersant I, and citric acid was added as a complexing agent. The volume was adjusted to 200 ml. The mixture was stirred thoroughly at 300 rpm for 2 hours using a magnetic stirrer to form a homogeneous solution. The solution was heated and stirred in an 80 °C water bath until the solvent evaporated, forming a viscous wet gel. Further drying was carried out to obtain a dry gel. The dry gel was transferred to a drying oven and dehydrated at 150 °C for 24 hours to obtain a dry gel block. The dry gel block was ground for 2 hours to obtain a dry gel powder. The dry gel powder was placed in a box furnace and sintered at 800 °C for 12 hours at a rate of 5 °C / min to obtain La. 0.7 Ca 0.3 MnO3 precursor powder with a particle size of 1 μm to 3 μm.
[0038] (2) Preparation of a homogeneous mixed suspension of liquid gallium: A high-purity gallium block with a purity of 99.99% was melted at 35℃ for 12 min to obtain a liquid gallium solution. Anhydrous ethanol was added to the liquid gallium solution as an alcohol dispersion medium, with a volume ratio of 5:1 between the alcohol dispersion medium and the liquid gallium solution. The solution was ultrasonically dispersed for 20 min at a frequency of 30 kHz and a power of 200 W using an ultrasonic disperser to uniformly disperse the liquid gallium solution droplets into the anhydrous ethanol, thus obtaining a homogeneous mixed suspension of liquid gallium. The droplet size of the liquid gallium solution was 80 nm to 150 nm, and the sphericity of the droplets was 0.8.
[0039] (3) Preparation of core-shell structured precursor particles: The La obtained in step (1) 0.7 Ca 0.3MnO3 precursor powder was sprinkled into the homogeneous mixed suspension of liquid gallium metal prepared in step (2) at a sprinkling rate of 0.2 g / s, with a mass ratio of precursor powder to homogeneous mixed suspension of liquid gallium metal of 1:5, to obtain a precursor powder / liquid gallium metal mixture. The mixture was stirred at 500 rpm for 60 min at a constant temperature of 30 ℃ to obtain precursor powder / liquid gallium metal particles with a preliminary coating effect, and a coating area ratio of 30%. Oily acid was added as dispersant II at a dropping rate of 0.08 ml / min at a constant temperature of 30 ℃, with the added mass of dispersant II being 0.2% of the total mass of the precursor powder / liquid gallium metal mixture, and the mixture was allowed to stand for 30 min. The settled mixture was then transferred to an ultrasonic disperser for 5-stage ultrasonic dispersion, with an ultrasonic frequency of 30 kHz, ultrasonic power of 200 W, and ultrasonic duration of 20 min in each stage, and stirring at 200 rpm for 4 min between each stage. Particles with a precursor powder / liquid metal gallium core-shell structure were obtained, with a particle size of 3 μm to 6 μm and a coating area ratio of 80%.
[0040] (4) Sintering to obtain composite particles: An inert ceramic scraper with a surface roughness of 0.03 μm was immersed in the mixture that had undergone multi-stage ultrasonic dispersion treatment in step (3). The back of the scraper was at a 45° acute angle to the surface of the mixture. The scraper was pulled up at a uniform speed of 2 mm / s to separate the core-shell structure particles from the mixture. The inert ceramic scraper carrying the separated particles was transferred to a heating stage in a glove box. The oxygen and water content in the glove box were both ≤5 ppm. The scraper was dried at 90 ℃ for 2 h. The inert ceramic scraper carrying the separated particles was quickly transferred to an atmosphere furnace. High-purity argon gas was introduced at a flow rate of 60 ml / min. The temperature was increased to 500 ℃ at 5 ℃ / min and sintered for 5 h to obtain precursor powder / gallium oxide composite particles with a particle size of 40 μm~60 μm, a coating area ratio of 70%, and an interface thickness of 20 nm~50 nm.
[0041] Example 2: A core-shell structured rare earth oxide / gallium oxide composite particle for magnetoresistive thin film preparation and its preparation method, wherein the composite particle comprises: The core is a rare earth oxide precursor powder, the chemical composition of which is La. 0.6 Ca 0.4 CoO3, x The value is 0.4, and the Tm transition metal element is Co. The outer shell covers the surface of the core, and the outer shell is made of gallium oxide.
[0042] A method for preparing core-shell structured rare earth oxide / gallium oxide composite particles for magnetoresistive thin film fabrication includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to La 0.6 Ca 0.4 Lanthanum nitrate, calcium nitrate, and cobalt nitrate were weighed out according to the stoichiometric ratio of CoO3. These chemicals were dissolved in a mixture of anhydrous ethanol and deionized water in a volume ratio of 4:1. Ethylene glycol was added as dispersant I, and citric acid was added as a complexing agent. The volume was adjusted to 220 ml. The mixture was stirred thoroughly at 350 rpm for 1.5 h using a magnetic stirrer to form a homogeneous solution. The solution was heated and stirred in a 90 °C water bath until the solvent evaporated, forming a viscous wet gel. Further drying was carried out to obtain a dry gel. The dry gel was transferred to a drying oven and dehydrated at 140 °C for 24 h to obtain a dry gel block. The dry gel block was ground for 1.5 h to obtain a dry gel powder. The dry gel powder was placed in a box furnace and sintered at 900 °C for 10 h at a rate of 5 °C / min to obtain La. 0.6 Ca 0.4 CoO3 precursor powder with a particle size of 2 μm to 4 μm.
[0043] (2) Preparation of a homogeneous mixed suspension of liquid gallium metal: A high-purity gallium metal block with a purity of 99.9% was selected and melted at 35℃ for 13 min to obtain a liquid gallium metal solution. Ethylene glycol was added to the liquid gallium metal solution as an alcohol dispersion medium, with a volume ratio of alcohol dispersion medium to liquid gallium metal solution of 8:1. The liquid gallium metal solution droplets were uniformly dispersed in anhydrous ethanol for 20 min using an ultrasonic disperser at a frequency of 35 kHz and a power of 200 W to obtain a homogeneous mixed suspension of liquid gallium metal. The droplet size of the liquid gallium metal solution was 100 nm to 180 nm, and the sphericity of the droplets was 0.8.
[0044] (3) Preparation of core-shell structured precursor particles: The La obtained in step (1) 0.6 Ca 0.4CoO3 precursor powder was sprinkled into the homogeneous mixed suspension of liquid gallium metal prepared in step (2) at a sprinkling rate of 0.3 g / s, with a mass ratio of precursor powder to homogeneous mixed suspension of liquid gallium metal of 1:8, to obtain a precursor powder / liquid gallium metal mixture. The mixture was stirred at 600 rpm for 80 min at a constant temperature of 35 ℃ to obtain precursor powder / liquid gallium metal particles with a preliminary coating effect, and a coating area ratio of 35%. Oily acid was added as dispersant II at a dropping rate of 0.08 ml / min at a constant temperature of 35 ℃, with the added mass of dispersant II being 0.2% of the total mass of the precursor powder / liquid gallium metal mixture, and the mixture was allowed to stand for 30 min. The settled mixture was then transferred to an ultrasonic disperser for 6-stage ultrasonic dispersion, with each stage having an ultrasonic frequency of 35 kHz, an ultrasonic power of 250 W, and an ultrasonic duration of 25 min, and stirring at 250 rpm for 4 min between each stage. Particles with a precursor powder / liquid metal gallium core-shell structure were obtained, with a particle size of 3 μm to 6 μm and a coating area ratio of 80%.
[0045] (4) Sintering to obtain composite particles: An inert ceramic scraper with a surface roughness of 0.04 μm was immersed in the mixture that had undergone multi-stage ultrasonic dispersion treatment in step (3). The back of the scraper was at a 50° acute angle to the surface of the mixture. The core-shell structure particles were separated from the mixture by uniformly lifting at a speed of 5 mm / s. The inert ceramic scraper carrying the separated particles was transferred to a heating stage in a glove box. The oxygen and water content in the glove box were both ≤5 ppm. The scraper was dried at 85 ℃ for 2 h. The inert ceramic scraper carrying the separated particles was quickly transferred to an atmosphere furnace. High-purity argon gas was introduced at a flow rate of 60 ml / min. The temperature was increased to 600 ℃ at 5 ℃ / min and sintered for 8 h to obtain precursor powder / gallium oxide composite particles with a particle size of 50 μm~80 μm, a coating area ratio of 65%, and an interface thickness of 20 nm~50 nm.
[0046] Example 3: Rare earth oxide composition design in this example: The rare earth oxide system La is selected. 0.5 Ca 0.5 (Mn 0.5 Fe 0.5 O3, x The value is 0.5, and the transition metal elements Tm are selected from Mn and Fe.
[0047] A method for preparing core-shell structured rare earth oxide / gallium oxide composite particles for magnetoresistive thin film fabrication includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to La 0.5 Ca 0.5 (Mn 0.5 Fe 0.5Lanthanum nitrate, calcium nitrate, manganese nitrate, and ferric nitrate were weighed out according to the stoichiometric ratio. These chemicals were dissolved in a mixture of anhydrous ethanol and deionized water at a volume ratio of 3:1. Ethylene glycol was added as dispersant I, and citric acid was added as a complexing agent. The volume was adjusted to 200 ml. The mixture was stirred thoroughly at 300 rpm for 2 hours using a magnetic stirrer to form a homogeneous solution. The solution was then heated and stirred in an 80 °C water bath until the solvent evaporated, forming a viscous wet gel. Further drying was carried out to obtain a dry gel. The dry gel was transferred to a drying oven and dehydrated at 150 °C for 24 hours to obtain a dry gel block. The dry gel block was ground for 2 hours to obtain a dry gel powder. The dry gel powder was placed in a box furnace and sintered at 800 °C for 12 hours at a rate of 5 °C / min to obtain La. 0.5 Ca 0.5 (Mn 0.5 Fe 0.5 O3 precursor powder with a particle size of 1 μm to 3 μm.
[0048] (2) Preparation of a homogeneous mixed suspension of liquid gallium: A high-purity gallium block with a purity of 99.99% was melted at 35℃ for 12 min to obtain a liquid gallium solution. Anhydrous ethanol was added to the liquid gallium solution as an alcohol dispersion medium, with a volume ratio of alcohol dispersion medium to liquid gallium solution of 5:1. The solution was ultrasonically dispersed at a frequency of 30 kHz and a power of 200 W for 20 min using an ultrasonic disperser to uniformly disperse the liquid gallium solution droplets into the anhydrous ethanol, thus obtaining a homogeneous mixed suspension of liquid gallium. The droplet size of the liquid gallium solution was 80 nm to 150 nm, and the sphericity of the droplets was 0.8.
[0049] (3) Preparation of particles with precursor powder / liquid metal gallium core-shell structure: The La obtained in step (1) 0.5 Ca 0.5 (Mn 0.5 Fe 0.5O3 precursor powder was sprinkled into the homogeneous mixed suspension of liquid gallium metal prepared in step (2) at a sprinkling rate of 0.2 g / s. The mass ratio of precursor powder to homogeneous mixed suspension of liquid gallium metal was 1:5, resulting in a precursor powder / liquid gallium metal mixture. The mixture was stirred at 500 rpm for 60 min at a constant temperature of 30 ℃ to obtain precursor powder / liquid gallium metal particles with a preliminary coating effect, and the coating area ratio was 30%. Oil acid was added as dispersant II at a dropping rate of 0.08 ml / min at a constant temperature of 30 ℃. The mass of dispersant II added was 0.2% of the total mass of the precursor powder / liquid gallium metal mixture, and the mixture was allowed to stand for 30 min. The mixture was then transferred to an ultrasonic disperser for 5-stage ultrasonic dispersion. The ultrasonic frequency of each stage was 30 kHz, the ultrasonic power was 200 W, and the ultrasonic duration was 20 min. The mixture was stirred at 200 rpm for 4 min between each stage. Particles with a precursor powder / liquid metal gallium core-shell structure were obtained, with a particle size of 3 μm to 6 μm and a coating area ratio of 75%.
[0050] (4) Preparation of precursor powder / gallium oxide composite particles: An inert ceramic scraper with a surface roughness of 0.03 μm was immersed in the mixture that had undergone multi-stage ultrasonic dispersion treatment in step (3). The back of the scraper was at a 45° acute angle to the surface of the mixture. The core-shell structured particles were separated from the mixture by uniformly lifting the scraper at a speed of 2 mm / s. The inert ceramic scraper carrying the separated particles was transferred to a heating stage in a glove box. The oxygen and water content in the glove box were both ≤5 ppm. The scraper was dried at 90 ℃ for 2 h. The inert ceramic scraper carrying the separated particles was quickly transferred to an atmosphere furnace. High-purity argon gas was introduced at a flow rate of 60 ml / min. The temperature was increased to 500 ℃ at 5 ℃ / min and sintered for 5 h to obtain precursor powder / gallium oxide composite particles with a particle size of 40 μm~60 μm, a coating area ratio of 65%, and an interface thickness of 20 nm~50 nm.
[0051] Example 4: Rare earth oxide composition design in this example: The rare earth oxide system La is selected. 0.8 Ca 0.2 CrO3, x The value is 0.2, and the Tm transition metal element is Cr.
[0052] A method for preparing core-shell structured rare earth oxide / gallium oxide composite particles for magnetoresistive thin film fabrication includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to La 0.8 Ca 0.2Lanthanum nitrate, calcium nitrate, and chromium nitrate were weighed out according to the stoichiometric ratio of CrO3. These chemicals were dissolved in a mixture of anhydrous ethanol and deionized water in a volume ratio of 3:1. Ethylene glycol was added as dispersant I, and citric acid was added as a complexing agent. The volume was adjusted to 200 ml. The mixture was stirred thoroughly at 300 rpm for 2 hours using a magnetic stirrer to form a homogeneous solution. The solution was heated and stirred in an 80 °C water bath until the solvent evaporated, forming a viscous wet gel. Further drying was carried out to obtain a dry gel. The dry gel was transferred to a drying oven and dehydrated at 150 °C for 24 hours to obtain a dry gel block. The dry gel block was ground for 2 hours to obtain a dry gel powder. The dry gel powder was placed in a box furnace and sintered at 800 °C for 12 hours at a rate of 5 °C / min to obtain La. 0.8 Ca 0.2 CrO3 precursor powder with a particle size of 1 μm to 3 μm.
[0053] (2) Preparation of a homogeneous mixed suspension of liquid gallium: A high-purity gallium block with a purity of 99.99% was melted at 35℃ for 12 min to obtain a liquid gallium solution. Anhydrous ethanol was added to the liquid gallium solution as an alcohol dispersion medium, with a volume ratio of alcohol dispersion medium to liquid gallium solution of 5:1. The solution was ultrasonically dispersed at a frequency of 30 kHz and a power of 200 W for 20 min using an ultrasonic disperser to uniformly disperse the liquid gallium solution droplets into the anhydrous ethanol, thus obtaining a homogeneous mixed suspension of liquid gallium. The droplet size of the liquid gallium solution was 80 nm to 150 nm, and the sphericity of the droplets was 0.8.
[0054] (3) Preparation of particles with precursor powder / liquid metal gallium core-shell structure: The La obtained in step (1) 0.8 Ca 0.2CrO3 precursor powder was sprinkled into the homogeneous mixed suspension of liquid gallium metal prepared in step (2) at a sprinkling rate of 0.2 g / s, with a mass ratio of precursor powder to homogeneous mixed suspension of liquid gallium metal of 1:5, to obtain a precursor powder / liquid gallium metal mixture. The mixture was stirred at 500 rpm for 60 min at a constant temperature of 30 ℃ to obtain precursor powder / liquid gallium metal particles with a preliminary coating effect, and a coating area ratio of 30%. Oily acid was added as dispersant II at a dropping rate of 0.08 ml / min at a constant temperature of 30 ℃, with the added mass of dispersant II being 0.2% of the total mass of the precursor powder / liquid gallium metal mixture. The mixture was allowed to stand for 30 min. The settled mixture was then transferred to an ultrasonic disperser for 5-stage ultrasonic dispersion, with an ultrasonic frequency of 30 kHz, ultrasonic power of 200 W, and ultrasonic duration of 20 min in each stage. The mixture was stirred at 200 rpm for 4 min between each stage. Particles with a precursor powder / liquid metal gallium core-shell structure were obtained, with a particle size of 3 μm to 6 μm and a coating area ratio of 75%.
[0055] (4) Preparation of precursor powder / gallium oxide composite particles: An inert ceramic scraper with a surface roughness of 0.03 μm was immersed in the mixture that had undergone multi-stage ultrasonic dispersion treatment in step (3). The back of the scraper was at a 45° acute angle to the surface of the mixture. The core-shell structured particles were separated from the mixture by uniformly lifting the scraper at a speed of 2 mm / s. The inert ceramic scraper carrying the separated particles was transferred to a heating stage in a glove box. The oxygen and water content in the glove box were both ≤5 ppm. The scraper was dried at 90 ℃ for 2 h. The inert ceramic scraper carrying the separated particles was quickly transferred to an atmosphere furnace. High-purity argon gas was introduced at a flow rate of 60 ml / min. The temperature was increased to 500 ℃ at 5 ℃ / min and sintered for 5 h to obtain precursor powder / gallium oxide composite particles with a particle size of 40 μm~60 μm, a coating area ratio of 65%, and an interface thickness of 20 nm~50 nm.
[0056] Example 5: Rare earth oxide composition design in this example: The rare earth oxide system La is selected. 0.55 Ca 0.45 (V,Cr,Mn)O3 x The value is 0.45, and the transition metal element Tm is V, Cr, or Mn.
[0057] A method for preparing core-shell structured rare earth oxide / gallium oxide composite particles for magnetoresistive thin film fabrication includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to La 0.55 Ca 0.45Lanthanum nitrate, calcium nitrate, ammonium metavanadate, chromium nitrate, and manganese nitrate were weighed out according to the stoichiometric ratio of (V,Cr,Mn)O3. These chemicals were dissolved in a mixture of anhydrous ethanol and deionized water in a volume ratio of 3:1. Ethylene glycol was added as dispersant I, and citric acid was added as a complexing agent. The volume was adjusted to 200 ml. The mixture was stirred thoroughly at 300 rpm for 2 hours using a magnetic stirrer to form a homogeneous solution. The solution was then heated and stirred in an 80 °C water bath until the solvent evaporated, forming a viscous wet gel. Further drying was carried out to obtain a dry gel. The dry gel was transferred to a drying oven and dehydrated at 150 °C for 24 hours to obtain a dry gel block. The dry gel block was ground for 2 hours to obtain a dry gel powder. The dry gel powder was placed in a box furnace and sintered at 850 °C for 14 hours at a rate of 5 °C / min to obtain La. 0.55 Ca 0.45 (V,Cr,Mn)O3 precursor powder with a particle size of 0.5 μm to 2 μm.
[0058] (2) Preparation of a homogeneous mixed suspension of liquid gallium: A high-purity gallium block with a purity of 99.99% was melted at 40℃ for 15 min to obtain a liquid gallium solution. Glycerol was added to the liquid gallium solution as an alcohol dispersion medium, with a volume ratio of alcohol dispersion medium to liquid gallium solution of 10:1. The liquid gallium solution droplets were ultrasonically dispersed in anhydrous ethanol for 20 min at a frequency of 30 kHz and a power of 200 W using an ultrasonic disperser to obtain a homogeneous mixed suspension of liquid gallium. The droplet size of the liquid gallium solution was 50 nm to 120 nm, and the sphericity of the droplets was 0.85.
[0059] (3) Preparation of particles with precursor powder / liquid metal gallium core-shell structure: The La obtained in step (1) 0.55 Ca 0.45(V,Cr,Mn)O3 precursor powder was sprinkled into the homogeneous mixed suspension of liquid gallium metal prepared in step (2) at a sprinkling rate of 0.5 g / s, with a mass ratio of precursor powder to homogeneous mixed suspension of liquid gallium metal of 1:10, to obtain a precursor powder / liquid gallium metal mixture. The mixture was stirred at 800 rpm for 100 min at a constant temperature of 30 ℃ to obtain precursor powder / liquid gallium metal particles with a preliminary coating effect, and a coating area ratio of 40%. Ethylene glycol was added dropwise at a dropping rate of 0.1 ml / min at a constant temperature of 30 ℃ as dispersant II, with the added mass of dispersant II being 0.3% of the total mass of the precursor powder / liquid gallium metal mixture, and the mixture was allowed to stand for 60 min. The settled mixture was transferred to an ultrasonic disperser for eight-stage ultrasonic dispersion. Each stage used an ultrasonic frequency of 40 kHz, an ultrasonic power of 300 W, and an ultrasonic duration of 30 min. During the intervals between stages, the mixture was stirred at 300 rpm for 5 min. This yielded particles with a precursor powder / liquid gallium core-shell structure, a particle size of 8 μm–10 μm, and a coating area ratio of 90%.
[0060] (4) Preparation of precursor powder / gallium oxide composite particles: An inert ceramic scraper with a surface roughness of 0.02 μm was immersed in the mixture that had undergone multi-stage ultrasonic dispersion treatment in step (3). The back of the scraper was at a 60° acute angle to the surface of the mixture. The core-shell structure particles were separated from the mixture by uniformly lifting the scraper at a speed of 0.5 mm / s. The inert ceramic scraper carrying the separated particles was transferred to a heating stage in a glove box. The oxygen and water content in the glove box were both ≤5 ppm. The scraper was dried at 100 ℃ for 3 h. The inert ceramic scraper carrying the separated particles was quickly transferred to an atmosphere furnace. High-purity argon gas was introduced at a flow rate of 60 ml / min. The temperature was increased to 700 ℃ at 5 ℃ / min and sintered for 10 h to obtain precursor powder / gallium oxide composite particles with a particle size of 80 μm~100 μm, a coating area ratio of 80%, and an interface thickness of 100 nm~200 nm.
[0061] Example 6: Rare earth oxide composition design in this example: The rare earth oxide system La is selected. 0.65 Ca 0.35 (V,Cr,Mn,Fe,Co)O3 x The value is 0.35, and the transition metal element Tm is V, Cr, Mn, Fe, or Co.
[0062] A method for preparing core-shell structured rare earth oxide / gallium oxide composite particles for magnetoresistive thin film fabrication includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to La 0.65 Ca 0.35Lanthanum nitrate, calcium nitrate, ammonium metavanadate, chromium nitrate, manganese nitrate, ferric nitrate, and cobalt nitrate were weighed out according to the stoichiometric ratio of (V,Cr,Mn,Fe,Co)O3. These chemicals were dissolved in a mixture of anhydrous ethanol and deionized water in a volume ratio of 3:1. Ethylene glycol was added as dispersant I, and citric acid was added as a complexing agent. The volume was adjusted to 200 ml. The mixture was stirred thoroughly at 300 rpm for 2 hours using a magnetic stirrer to form a homogeneous solution. The solution was then heated and stirred in an 80 °C water bath until the solvent evaporated, forming a viscous wet gel. This gel was further dried to obtain a dry gel. The dry gel was transferred to a drying oven and dehydrated at 150 °C for 24 hours to obtain a dry gel block. The dry gel block was ground for 2 hours to obtain a dry gel powder. The dry gel powder was placed in a box furnace and sintered at 1000 °C for 8 hours at a rate of 5 °C / min to obtain La. 0.65 Ca 0.35 (V,Cr,Mn,Fe,Co)O3 precursor powder with a particle size of 4 μm to 5 μm.
[0063] (2) Preparation of a homogeneous mixed suspension of liquid gallium: A high-purity gallium block with a purity of 99.99% was selected and melted at 30℃ for 10 min to obtain a liquid gallium solution. Anhydrous ethanol was added to the liquid gallium solution as an alcohol dispersion medium, with a volume ratio of alcohol dispersion medium to liquid gallium solution of 5:1. The solution was ultrasonically dispersed at a frequency of 30 kHz and a power of 200 W for 20 min using an ultrasonic disperser to uniformly disperse the liquid gallium solution droplets into the anhydrous ethanol, thus obtaining a homogeneous mixed suspension of liquid gallium. The droplet size of the liquid gallium solution was 150 nm to 200 nm, and the sphericity of the droplets was 0.75.
[0064] (3) Preparation of particles with precursor powder / liquid metal gallium core-shell structure: The La obtained in step (1) 0.65 Ca 0.35(V,Cr,Mn,Fe,Co)O3 precursor powder was sprinkled into the homogeneous mixed suspension of liquid gallium metal prepared in step (2) at a sprinkling rate of 0.05 g / s. The mass ratio of precursor powder to homogeneous mixed suspension of liquid gallium metal was 1:5, resulting in a precursor powder / liquid gallium metal mixture. The mixture was stirred at 200 rpm for 30 min at a constant temperature of 30 ℃ to obtain precursor powder / liquid gallium metal particles with a preliminary coating effect, and the coating area ratio was 20%. Oil acid was added as dispersant II at a dropping rate of 0.05 ml / min at a constant temperature of 30 ℃. The mass of dispersant II added was 0.1% of the total mass of the precursor powder / liquid gallium metal mixture, and the mixture was allowed to stand for 10 min. The settled mixture was transferred to an ultrasonic disperser for three-stage ultrasonic dispersion. Each stage used an ultrasonic frequency of 20 kHz, an ultrasonic power of 150 W, and an ultrasonic duration of 15 min. During the intervals between stages, the mixture was stirred at 100 rpm for 3 min. This yielded particles with a precursor powder / liquid gallium core-shell structure, a particle size of 1 μm–3 μm, and a coating area ratio of 60%.
[0065] (4) Preparation of precursor powder / gallium oxide composite particles: An inert ceramic scraper with a surface roughness of 0.05 μm was immersed in the mixture that had undergone multi-stage ultrasonic dispersion treatment in step (3). The back of the scraper was at a 20° acute angle to the surface of the mixture. The core-shell structure particles were separated from the mixture by uniformly lifting the scraper at a speed of 10 mm / s. The inert ceramic scraper carrying the separated particles was transferred to a heating stage in a glove box. The oxygen and water content in the glove box were both ≤5 ppm. The scraper was dried at 80 ℃ for 1 h. The inert ceramic scraper carrying the separated particles was quickly transferred to an atmosphere furnace. High-purity argon gas was introduced at a flow rate of 60 ml / min. The temperature was increased to 300 ℃ at 5 ℃ / min and sintered for 1 h to obtain precursor powder / gallium oxide composite particles with a particle size of 10 μm~30 μm, a coating area ratio of 50%, and an interface thickness of 5 nm~20 nm.
[0066] Example 7: Preparation of La 0.8 Ca 0.2 FeO3 / gallium oxide core-shell structured composite particles.
[0067] The process is basically the same as in Example 1, except that: in step (1), the chemicals used are lanthanum nitrate, calcium nitrate, and ferric nitrate; the sintering temperature is 900 ℃; and in step (4), the sintering temperature is 600 ℃ and the sintering time is 3 h. The resulting composite particles have a particle size of 15 μm ~ 40 μm, an interface thickness of about 30 nm, and a coating area of about 75%.
[0068] The technical solutions of this invention are not limited to the specific embodiments described above. Any technical modifications, alterations, substitutions, and variations made to the technical solutions of this invention without departing from the spirit and scope of the claims are within the protection scope of this invention.
Claims
1. A core-shell structured rare earth oxide / gallium oxide composite particle for preparing magnetoresistive thin films, characterized in that, The composite particles include: The core is a rare earth oxide precursor powder, the chemical composition of which is La. 1-x Ca x TmO3, where 0 < x <1, Tm is selected from any one or at least two of V, Cr, Mn, Fe, and Co; An outer shell, which covers the surface of the core, is made of gallium oxide; The composite particles have a particle size of 10 μm to 100 μm, the interface thickness between the shell and the core is 5 nm to 200 nm, and the shell covers 50% to 80% of the core area.
2. The composite particles according to claim 1, characterized in that, The Tm is any one of V, Cr, Mn, Fe, and Co; or the Tm is any two, three, four, or a combination of all five of V, Cr, Mn, Fe, and Co.
3. A method for preparing the composite particles according to claim 1 or 2, characterized in that, Includes the following steps: (1) Preparation of rare earth oxide precursor powder: according to chemical composition La 1-x Ca x TmO3 was weighed and chemical reagents were used to prepare rare earth oxide precursor powder with a particle size of 0.3 μm to 5 μm through sol-gel method and sintering process; (2) Preparation of homogeneous mixed suspension of liquid gallium metal: Melt gallium metal with a purity of ≥99.9% to obtain a liquid gallium metal solution, add an alcohol dispersion medium to it, and disperse by ultrasonication to obtain a homogeneous mixed suspension containing liquid gallium metal droplets with a particle size of 50 nm~200 nm; (3) Preparation of core-shell structured precursor particles: The rare earth oxide precursor powder obtained in step (1) is sprinkled into the liquid gallium homogeneous mixed suspension obtained in step (2), and after stirring, standing and ultrasonic dispersion treatment, precursor particles with core-shell structure are obtained, wherein the core is rare earth oxide precursor powder, the outer shell is liquid gallium, the coating area ratio is 60%~90%, and the particle size is 1 μm~10 μm; (4) Sintering to obtain composite particles: The precursor particles with core-shell structure obtained in step (3) are sintered at 300 ℃~700 ℃ for 1 h~10 h under inert atmosphere or vacuum conditions to transform the liquid metal gallium shell into a gallium oxide shell, thereby obtaining the composite particles as described in claim 1 or 2.
4. The method according to claim 3, characterized in that, Step (1) specifically includes: dissolving the chemical in a mixed solvent of deionized water and alcohol, adding an appropriate amount of dispersant I and complexing agent, and adjusting the volume to 90 ml to 800 ml; after fully dissolving by magnetic stirring, heating and stirring at 70 ℃ to 100 ℃ and 200 rpm to 500 rpm for 0.5 h to 2 h to form a wet gel and drying and solidifying it to obtain a dry gel; dehydrating the dry gel at 120 ℃ to 170 ℃ for 5 h to 72 h to obtain a dry gel block; grinding for 1 h to 3 h to obtain a dry gel powder; wherein, the alcohol solvent is any one of anhydrous ethanol, methanol or glycerol, and the volume ratio of alcohol solvent to deionized water is 2:1 to 5:1; the dispersant I is ethylene glycol, and the complexing agent is any one of calcium acetate, calcium chloride or citric acid.
5. The method according to claim 3 or 4, characterized in that, The chemical reagents mentioned in step (1) are lanthanum nitrate, calcium nitrate, and at least one selected from ammonium metavanadate, chromium nitrate, manganese nitrate, iron nitrate, and cobalt nitrate; the heating rate of the sintering process is 1 ℃ / min~15 ℃ / min, the sintering temperature is 400 ℃~1000 ℃, and the sintering time is 8 h~16 h.
6. The method according to claim 3, characterized in that, The melting temperature in step (2) is 30℃~40℃, and the melting time is 10 min~15 min; the alcohol dispersion medium is any one of anhydrous ethanol, ethylene glycol, and glycerol, and the volume ratio of the alcohol dispersion medium to the liquid gallium solution is 1:1~10:
1.
7. The method according to claim 3, characterized in that, In step (3), the spreading rate is 0.05 g / s to 1 g / s, and the difference in the distribution of precursor powder during spreading is ≤5%; the stirring is carried out at a constant temperature of 25 ℃ to 35 ℃, the stirring rate is 200 rpm to 800 rpm, and the stirring time is 30 min to 100 min; after stirring, dispersant II is added dropwise, and the mixture is allowed to stand for 10 min to 60 min.
8. The method according to claim 3, characterized in that, In step (3), the ultrasonic dispersion is a multi-stage ultrasonic dispersion. The ultrasonic frequency of each stage is 20 kHz to 40 kHz, the power is 150 W to 300 W, the duration is 15 min to 30 min, and the number of stages is 3 to 8. Stirring is carried out between each stage of ultrasonic dispersion, with a stirring rate of 100 rpm to 300 rpm and a stirring duration of 3 min to 5 min.
9. The method according to claim 7, characterized in that, In step (3), the dispersant II can be oleic acid or ethylene glycol, the mass of dispersant II added is 0.1% to 0.3% of the total mass of the precursor powder / liquid gallium metal mixture, and the dropping rate of dispersant II is 0.05 ml / min to 0.1 ml / min.
10. The method according to claim 3, characterized in that, In step (4), before sintering, the precursor particles with the core-shell structure are separated from the mixture by an inert ceramic scraper and dried in a glove box with oxygen and water content ≤10 ppm. The drying temperature is 80 ℃~100 ℃ and the drying time is 1 h~3 h.