Rare earth metal target material and preparation method thereof

Abstract

The invention provides a rare earth metal target material and a preparation method thereof, the target material comprises the following elements by mass: 70-90% of rare earth metal, 5-15% of transition metal, and 3-10% of a dispersant; the oxygen content in the impurities is less than 300 ppm, and the iron content in the impurities is less than 100 ppm. The preparation method comprises the steps of extraction, modification, reduction, forming and cooling. The technological process is more reasonable, large-scale production can be achieved, the problems existing in the prior art can be comprehensively solved, and urgent requirements and important application value are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, and in particular relates to a rare earth metal target material and a preparation method thereof. Background Art

[0002] Rare earth metal targets are key raw materials for the preparation of thin films using magnetron sputtering technology. This type of target is mainly used to deposit rare earth metal or alloy films with special magnetic, optical or electrical properties, and has important applications in magneto-optical storage media, magnetostrictive devices, magnetic sensors, solid-state refrigeration materials and certain catalytic coatings. Rare earth transition metal alloy films represented by terbium, iron, and cobalt (Tb, Fe, Co) were once the core materials for high-density magneto-optical storage due to their excellent perpendicular magnetic anisotropy. Although mainstream storage technologies have changed, high-purity, high-performance rare earth metal targets and their coatings are still indispensable in cutting-edge fields that require extreme magneto-optical properties, high coercivity or large magnetostriction coefficients, such as precision magnetron devices, special sensors, and novel solid-state refrigeration structures.

[0003] However, rare earth metal targets face several prominent technical challenges in their actual manufacturing and application. The first is the difficulty in controlling oxygen content. Rare earth elements are extremely active and easily combine with oxygen to form stable oxide inclusions. These oxides exist within the target and can cause abnormal discharges ("sparking") during the sputtering process, contaminating the deposited film and significantly reducing the consistency of the film's magnetic and electrical properties. For example, this can lead to discrete coercivity and fluctuations in the magneto-optical Kerr angle. The second is poor microstructure. Rare earth metals are generally hard but relatively ductile, and they are prone to forming coarse columnar crystals or uneven microstructures during traditional smelting, casting, and processing. Coarse grains lead to uneven sputtering rate distribution during sputtering, making it difficult to ensure uniform film thickness, and grain boundary regions are prone to becoming impurity and defect-rich areas. The third is insufficient density. Defects such as pores and shrinkage can reduce target utilization and may induce particle arcing during sputtering, damaging the surface quality of the film. Fourth, some rare earth elements (such as Tb and Dy) are extremely expensive. How to optimize the ratio of the main components and accurately control them to reduce the cost of raw materials while ensuring performance is of great economic significance.

[0004] To overcome these problems, various attempts have been made in the prior art. To reduce oxygen content, high-vacuum melting combined with subsequent reduction treatments, such as calcium thermal reduction and molten salt electrolytic refining, or melting and heat treatment in a protective atmosphere (such as high-purity argon) are commonly used. However, high-vacuum melting equipment is expensive and cycle times are long, and reduction treatments may introduce new metallic impurities, such as residual calcium. Furthermore, for certain heavy rare earth elements, deep deoxidation is limited. To improve microstructure, common techniques include adding trace amounts of Zr and B grain refiners or employing powder metallurgy routes such as hot pressing and hot isostatic pressing. However, the introduction of grain refiners requires extreme caution; too little is ineffective, while too much may form refractory compounds, ultimately reducing purity. While powder metallurgy routes can achieve fine crystals, they require a lengthy production process and are susceptible to secondary oxidation during powder preparation, storage, and sintering. Furthermore, the sputtering rate of powder metallurgy targets is sometimes less than that of cast targets. To increase density, hot isostatic pressing (HIP) is a common method that effectively closes internal pores. However, HIP process parameters such as temperature, pressure, and time must be closely matched to the properties of the specific rare earth material. Improper handling can lead to excessive grain growth or target deformation. Finally, in terms of composition optimization and cost control, this is usually achieved by reducing the proportion of expensive elements such as Tb, adding some alternative elements such as Dy and Gd, and strictly controlling the precision of the ingredients. However, the selection and proportion optimization of the alternative elements are difficult, and improper proportioning can lead to a serious decline in core performance.

[0005] In summary, existing technologies have made some progress in addressing the issues of high oxygen content, coarse structure, low density, and high cost in rare earth targets. However, these technologies still face challenges, such as complex processes, high costs, the risk of impurity introduction, and the difficulty in balancing performance and cost. In particular, it is difficult to simultaneously achieve high purity, a fine and uniform structure, high density, and optimal cost-effectiveness. Therefore, it is necessary to design a rare earth metal target and its preparation method. Summary of the Invention

[0006] In order to overcome the defects in the prior art, a rare earth metal target material and a preparation method thereof are provided.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A rare earth metal target material comprises the following elements by mass percentage: 70-90% rare earth metal, 5-15% transition metal, 3-10% dispersant; the remainder is unavoidable impurities, wherein the oxygen content of the impurities is less than 300ppm, and the iron content is less than 100ppm.

[0009] The rare earth metals are Nd, Pr and Dy, wherein the mass ratio of Nd to Pr is 3-5:1, and the added amount of Dy is 1-5% of the total mass of the target material.

[0010] The transition metal is selected from one of Ti, Zr and Mo.

[0011] The dispersant comprises boron nitride with a particle size of 50-200 nm, and the surface of the boron nitride is coated with a silicon dioxide layer with a thickness of 1-3 nm.

[0012] A method for preparing a rare earth metal target, the method comprising the following steps:

[0013] (a) Extraction: The rare earth concentrate is subjected to a combined mechanical activation and acid leaching treatment to obtain rare earth oxide powder with a particle size D50 of 5-20 μm;

[0014] (b) Modification: The rare earth oxide powder is mixed with a transition metal powder and a dispersant, and ball milled under an argon atmosphere for 4-12 hours at a ball-to-powder ratio of 10-20:1 and a rotation speed of 200-400 rpm to obtain a modified powder;

[0015] (c) Reduction: The modified powder is placed in a vacuum induction furnace and reduced at 800-950°C for 2-4 hours using hydrogen as a reducing agent until the oxygen content of the powder is ≤500 ppm. The powder with a particle size distribution D90 <30 μm obtained by argon gas flow classification is the reduced powder;

[0016] (d) Molding: The reduced powder is placed into a graphite mold, pressurized to 20-50 MPa in a hot pressing sintering furnace, and heated to 1100-1300°C for 1-3 hours;

[0017] (e) Cooling: Slowly cool to below 200°C at a rate of 10-30°C / min, then take out of the furnace and continue cooling to room temperature to obtain the rare earth metal target.

[0018] In step (a), the rare earth concentrate is bastnaesite or monazite, and the REO content after flotation is ≥90%;

[0019] Mechanical activation uses a planetary ball mill with an activation time of 30-60 minutes and an impact energy of 5-15J / time;

[0020] Acid leaching uses a mixed acid of hydrochloric acid and nitric acid in a volume ratio of 3-5:1, a leaching temperature of 60-90°C, and a leaching time of 2-4 hours.

[0021] The hot pressing sintering in step (d) is divided into two stages: the first stage is to increase the temperature to 800° C. at 5-10° C. / min and hold the temperature for 10-20 minutes; the second stage is to increase the temperature to the target temperature at 2-5° C. / min.

[0022] In the second stage, a pulse current is applied simultaneously with a frequency of 10-50 Hz and a current density of 50-200 A / cm 2 .

[0023] Step (d) After forming, the target surface is sandblasted with a particle size of 80-120 mesh, a sandblasting pressure of 0.2-0.5 MPa, and a roughness of Ra 0.8-1.5 μm.

[0024] During the cooling step (e), the target material is subjected to vacuum annealing after being taken out of the furnace, with the annealing temperature being 500-700°C, the time being 1-2 hours, and the vacuum degree being ≤1×10 -3 Pa.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0026] 1. The present application can synergistically achieve multiple performance optimizations of rare earth metal targets in a one-step preparation process: strictly control oxygen impurities through hydrogen reduction combined with argon gas grading, significantly reducing sputtering ignition and film contamination; utilize nano-boron nitride dispersants coated with silicon dioxide on the surface in conjunction with multi-stage ball milling and hot pressing processes to effectively refine grains and suppress structural heterogeneity; significantly improve density with the help of staged temperature-controlled pressurization, pulse current assistance, and slow cooling treatment, eliminating the problem of particle splashing caused by pores; and at the same time, by optimizing the ratio of the neodymium to praseodymium ratio and the amount of dysprosium added, combined with an integrated process from concentrate extraction to molding, significantly reduce raw material and processing costs while maintaining core functions such as perpendicular magnetic anisotropy.

[0027] 2. The preparation method of the present application can significantly reduce the oxygen content of the target material. By using hydrogen as a reducing agent in a vacuum induction furnace to carry out a reduction reaction at 800 to 950 degrees Celsius, combined with argon gas flow classification treatment, the oxygen content of the final target material is effectively controlled at a low level (ie, the impurity oxygen content is less than 300ppm). This method utilizes the strong reducing properties of hydrogen to decompose rare earth oxides, avoiding new impurities such as calcium residues that may be introduced by high vacuum melting or subsequent reduction treatment, and the argon protection in the step effectively prevents the secondary oxidation of the powder during the classification process. As a result, the formation of oxide inclusions is reduced, thereby suppressing the risk of abnormal discharge and thin film contamination during the sputtering process, ensuring the consistency and stability of magnetic and electrical properties, such as reducing coercive force fluctuations and magneto-optical Kerr angle deviations.

[0028] 3. The present application can optimize the microstructure of the target material. The preparation method uses a dispersant, that is, the surface of the boron nitride particles with a particle size of 50 to 200 nanometers is covered with a 1 to 3 nanometer thick silica coating layer. The ball milling process ensures the uniform mixing of the rare earth oxide powder with the transition metal powder and the dispersant, and the boron nitride particles in the dispersant act as a grain refiner, and the coated silica layer prevents it from excessive aggregation. Subsequently, a slow heating rate and multi-stage heat preservation are used in the hot pressing sintering stage to promote homogenization and micro-grain refinement. The target material obtained in this way forms a fine-grain structure, avoids the coarse columnar crystals or uneven areas commonly seen in traditional casting, reduces the impurity enrichment and defect density in the grain boundary area, and improves the film thickness uniformity and rate stability during sputtering.

[0029] 4. This application can effectively improve the density of the target material. The key steps include pressurizing to 20 to 50 MPa during hot pressing and sintering, and heating in two stages. In the second stage, pulse current is also applied to assist. The high pressure and high temperature during the hot pressing process are combined with the energy input of the pulse current to effectively close internal pores, shrinkage and other defects, promote plastic deformation and recrystallization of the material; slow cooling operation reduces thermal stress and cracking risks. In addition, the sandblasting treatment and subsequent vacuum annealing treatment of the target surface further optimize the surface roughness and micro-density. This combined method eliminates the problems of porosity and particle splashing, thereby improving the surface quality of the film and the utilization rate of the target material.

[0030] 5. This application can balance the cost-effectiveness and core performance of the target material. By optimizing the ratio of the main components, it includes 70 to 90% rare earth metals in terms of mass percentage, of which the mass ratio of neodymium to praseodymium is controlled at 3 to 5 to 1, and 1 to 5% of low-cost dysprosium is added, matched with 5 to 15% of transition metals. In the preparation process, the front end adopts mechanical activation-acid leaching to extract rare earth concentrate (, and uses a planetary ball mill for short-time activation combined with mixed acid leaching to efficiently extract high-purity rare earth oxide powder at 60 to 90 degrees Celsius. This method avoids the high cost dependence on heavy rare earth elements, and reduces processing cycle and raw material consumption through precise ingredient preparation and integrated processes, while retaining key functional characteristics such as perpendicular magnetic anisotropy, achieving a reasonable compromise between performance and cost. DETAILED DESCRIPTION

[0031] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] In this application, the sources of various raw materials are briefly described as follows:

[0033] Bastnaesite, supplied by China Rare Earth Group Co., Ltd., contains at least 90% rare earth oxides and is purified through flotation for use in raw material extraction. Monazite ore, also supplied by China Rare Earth Group Co., Ltd., contains over 90% rare earth oxides, making it suitable for acid leaching. Hydrochloric acid, purchased from Sinopharm Chemical Reagent Co., Ltd., CAS number 7647-01-0, is analytically pure and has a concentration of 36-38%. It is used in the mixed acid preparation during the acid leaching step. Nitric acid, sourced from Sinopharm Chemical Reagent Co., Ltd., CAS number 7697-37-2, is analytically pure and has a concentration of 65-68%. It is mixed with hydrochloric acid by volume. Titanium powder, purchased from Alfa Aesar (China) Chemical Co., Ltd., model T-325, has a purity of 99.5% and a particle size distribution of 1-5 microns. It is used as a transition metal additive. Zirconium powder, supplied by Aladdin Biochemical Technology Co., Ltd., model ZR-200M, has a purity of 99.9% and an average particle size of 2 microns, making it suitable for transition metal component selection. Molybdenum powder, purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd., CAS number 7439-98-7, with a purity of 99.95% and a particle size range of 1-10 μm, is used in target formulations with specific performance requirements. Boron nitride dispersant, coated with a silica layer, is produced by Shanghai MacLean Biochemical Technology Co., Ltd., model BN-SiO2-100, with a particle size range of 50-200 nm and a silica coating thickness of 1-3 nm. It serves as the dispersion medium in the powder mixing process. High-purity hydrogen, supplied by Guangdong Huate Gas Co., Ltd., with a purity of 99.999%, is used for the reduction reaction in the vacuum induction furnace.

[0034] A rare earth metal target material comprises the following elements by mass percentage: 70-90% rare earth metal, 5-15% transition metal, 3-10% dispersant; the remainder is unavoidable impurities, wherein the oxygen content of the impurities is less than 300ppm, and the iron content is less than 100ppm.

[0035] The rare earth metals are Nd, Pr and Dy, wherein the mass ratio of Nd to Pr is 3-5:1, and the added amount of Dy is 1-5% of the total mass of the target material.

[0036] The transition metal is selected from one of Ti, Zr and Mo.

[0037] The dispersant comprises boron nitride with a particle size of 50-200 nm, and the surface of the boron nitride is coated with a silicon dioxide layer with a thickness of 1-3 nm.

[0038] A method for preparing a rare earth metal target, the method comprising the following steps:

[0039] (a) Extraction: The rare earth concentrate is subjected to a combined mechanical activation and acid leaching treatment to obtain rare earth oxide powder with a particle size D50 of 5-20 μm;

[0040] (b) Modification: The rare earth oxide powder is mixed with a transition metal powder and a dispersant, and ball milled under an argon atmosphere for 4-12 hours at a ball-to-powder ratio of 10-20:1 and a rotation speed of 200-400 rpm to obtain a modified powder;

[0041] (c) Reduction: The modified powder is placed in a vacuum induction furnace and reduced at 800-950°C for 2-4 hours using hydrogen as a reducing agent until the oxygen content of the powder is ≤500 ppm. The powder with a particle size distribution D90 <30 μm obtained by argon gas flow classification is the reduced powder;

[0042] (d) Molding: The reduced powder is placed into a graphite mold, pressurized to 20-50 MPa in a hot pressing sintering furnace, and heated to 1100-1300°C for 1-3 hours;

[0043] (e) Cooling: Slowly cool to below 200°C at a rate of 10-30°C / min, then take out of the furnace and continue cooling to room temperature to obtain the rare earth metal target.

[0044] In step (a), the rare earth concentrate is bastnaesite or monazite, and the REO content after flotation is ≥90%;

[0045] Mechanical activation uses a planetary ball mill with an activation time of 30-60 minutes and an impact energy of 5-15J / time;

[0046] Acid leaching uses a mixed acid of hydrochloric acid and nitric acid in a volume ratio of 3-5:1, a leaching temperature of 60-90°C, and a leaching time of 2-4 hours.

[0047] The hot pressing sintering in step (d) is divided into two stages: the first stage is to increase the temperature to 800° C. at 5-10° C. / min and hold the temperature for 10-20 minutes; the second stage is to increase the temperature to the target temperature at 2-5° C. / min.

[0048] In the second stage, a pulse current is applied simultaneously with a frequency of 10-50 Hz and a current density of 50-200 A / cm 2 .

[0049] Step (d) After forming, the target surface is sandblasted with a particle size of 80-120 mesh, a sandblasting pressure of 0.2-0.5 MPa, and a roughness of Ra 0.8-1.5 μm.

[0050] During the cooling step (e), the target material is subjected to vacuum annealing after being taken out of the furnace, with the annealing temperature being 500-700°C, the time being 1-2 hours, and the vacuum degree being ≤1×10 -3 Pa.

[0051] The process flow of this application is more reasonable, can be produced on a large scale, and can comprehensively solve the problems existing in the existing technology. It has urgent needs and important application value.

[0052] The technical solution of the present invention is further illustrated by the following examples and comparative examples, but the protection scope of the present invention is not limited thereto.

[0053] Example 1

[0054] This embodiment provides a rare earth metal target and its preparation method. The target composition, excluding impurities, is, by mass percentage, 85% rare earth metal, 5% transition metal, and 10% dispersant. The mass ratio of neodymium to praseodymium in the rare earth metals is 5:1, and the dysprosium addition amount is 5% of the total target mass. Molybdenum is used as the transition metal. The dispersant is 200 nm boron nitride particles coated with a 1 nm thick silicon dioxide layer. The preparation process is as follows: First, bastnaesite with a REO content of ≥90% after flotation is mechanically activated in a planetary ball mill for 30 minutes (impact energy 15 J / cycle), then leached in a mixed acid of hydrochloric acid and nitric acid in a volume ratio of 3:1 at 90°C for 2 hours to obtain a rare earth oxide powder with a D50 of 20 μm. Next, this powder is ball milled with molybdenum powder and dispersant under argon for 4 hours (ball-to-material ratio 20:1, rotation speed 400 rpm). Subsequently, the powder was reduced at 800°C for 4 hours using hydrogen as a reducing agent in a vacuum induction furnace. After reduction, the oxygen content of the powder was ≤500ppm. After argon gas flow classification, the reduced powder with D90 <30μm was obtained. The powder was loaded into a graphite mold and pressurized to 20MPa in a hot press furnace. In the first stage, the temperature was increased to 800°C at 10°C / min and the pressure was maintained for 10 minutes. In the second stage, the temperature was increased to 1100°C at 5°C / min and the temperature was maintained for 1 hour (during which the frequency was 50Hz and the current density was 200A / cm 2 After forming, the product is slowly cooled to 200°C at a rate of 10°C / min and then removed from the furnace. The surface is sandblasted with 120-mesh sand at a pressure of 0.2 MPa to a Ra of 1.5 μm. Finally, it is vacuum annealed (500°C for 2 hours, vacuum ≤ 1×10-3 Pa) and cooled to room temperature.

[0055] Example 2

[0056] In this embodiment, the same points as in Example 1 are not described in detail, and the differences are as follows:

[0057] In this embodiment, the target material composition, excluding impurities, is: 87% rare earth metal, 5% transition metal, and 8% dispersant. The rare earth metal mass ratio of neodymium to praseodymium is 3:1, and the dysprosium addition amount is 1%. Zirconium is used as the transition metal. The dispersant is 3 nm silica coated with boron nitride with a particle size of 50 nm. Preparation steps: Monazite concentrate (REO ≥ 90%) is activated by planetary ball milling for 60 minutes (impact energy 5 J / shot), and then leached at 60°C for 4 hours with a mixed acid of hydrochloric acid and nitric acid in a volume ratio of 5:1 to obtain a rare earth oxide powder with a D50 of 5 μm. This powder is then argon ball milled with zirconium powder and dispersant for 12 hours (ball-to-material ratio 10:1, rotation speed 200 rpm). Hydrogen reduction is performed at 950°C for 2 hours. After argon classification, the powder oxygen content is ≤ 500 ppm. The hot pressing pressure was 50 MPa. The first stage was heated at 5 ° C / min to 800 ° C and kept at this temperature for 20 minutes. The second stage was heated at 2 ° C / min to 1300 ° C and kept at this temperature for 3 hours (applied frequency 10 Hz, current density 50 A / cm 2 Pulse current). Cooling rate: 30°C / min. Sandblasting: 80-mesh sand, 0.5 MPa pressure, to a Ra of 0.8 μm. Vacuum annealing: 700°C, 1 hour.

[0058] Example 3

[0059] In this embodiment, the same points as in Example 1 are not described in detail, and the differences are as follows:

[0060] In this embodiment, the target material composition excluding impurities is: 87% rare earth metal, 10% transition metal, and 3% dispersant. The mass ratio of neodymium to praseodymium is 4:1, and the amount of dysprosium added is 3%. Titanium is selected as the transition metal. The dispersant is 125nm boron nitride coated with 2nm silica. Preparation process: Fluorocarbon cerium ore is mechanically activated for 45 minutes (impact energy 10J / time), and leached at 75°C for 3 hours with a mixed acid volume ratio of 4:1 (hydrochloric acid / nitric acid) to obtain D50=12μm rare earth oxide powder. Ball milling parameters: ball-to-material ratio 15:1, rotation speed 300rpm, time 8 hours. Hydrogen reduction temperature 880°C, reduction for 3 hours. Hot pressing pressure 35MPa, in the first stage, the temperature is increased to 800°C at 8°C / min and the pressure is maintained for 15 minutes, and in the second stage, the temperature is increased to 1200°C at 3°C / min and the temperature is maintained for 2 hours (pulse current frequency 30Hz, current density 120A / cm 2 The cooling rate was 20°C / min, and the sandblasting was performed using 100-mesh sand at a pressure of 0.3 MPa to achieve an Ra of 1.2 μm. The vacuum annealing conditions were 600°C for 1.5 hours.

[0061] Comparative Example 1

[0062] In this comparative example, the same points as in Example 1 are not repeated here, and the differences are as follows:

[0063] The dispersant was changed to boron nitride (particle size 150 nm) without silicon dioxide coating.

[0064] Comparative Example 2

[0065] In this comparative example, the same points as Example 2 are not repeated here, and the differences are as follows:

[0066] No transition metals are added, and rare earth metals increase to 90%.

[0067] Comparative Example 3

[0068] In this comparative example, the same points as in Example 3 are not repeated here, and the differences are as follows:

[0069] The oxygen content of the reduced powder is 600ppm.

[0070] Comparative Example 4

[0071] In this comparative example, the same points as in Example 1 are not repeated here, and the differences are as follows:

[0072] The cooling rate was changed to 50°C / min (which did not meet the slow cooling requirement).

[0073] Comparative Example 5

[0074] In this comparative example, the same points as in Example 1 are not repeated here, and the differences are as follows:

[0075] The pulse current is cancelled in the second stage of hot pressing.

[0076] Performance test results and analysis

[0077] The target materials obtained in the examples and comparative examples were sputtered using a magnetron sputtering coating device (substrate: silicon wafer, power: 5 kW, argon pressure: 0.5 Pa), and the film thickness was uniformly controlled to be 200 nm. The test results are shown in Table 1.

[0078] Table 1 Analysis and test results

[0079]

[0080] Test results demonstrate the effectiveness of oxygen content control. The oxygen contents of Examples 1-3 (190-250 ppm) were all below the upper limit of 300 ppm. Example 2, due to its high-temperature reduction at 950°C and strict classification, achieved the lowest oxygen content (190 ppm). Comparative Example 3, due to excessive oxygen content in the reduced powder (600 ppm), resulted in a final target material oxygen content of 580 ppm. Its coercivity fluctuation (12.6%) was significantly higher than that of the Examples (1.8-2.1%), confirming the critical influence of oxygen impurities on magnetic stability.

[0081] Example 2 achieved the finest grains (5.7 μm), attributed to the synergistic effect of a small-particle dispersant (50 nm) and extended ball milling (12 hours), resulting in an optimized microstructure. In Comparative Example 1, the lack of silica coating in the dispersant resulted in boron nitride agglomeration, increasing the grain size to 12.5 μm and reducing the sputtering rate by 31% (Comparative Example 2), demonstrating the importance of a coating for dispersant stability.

[0082] In Example 2, under high pressure of 50 MPa, 1300°C, and pulse current, the porosity is as low as 0.08%. In Comparative Example 4, thermal stress cracks are generated due to rapid cooling (50°C / min), and the porosity rises to 0.41%. In Comparative Example 5, the porosity increases to 0.31% after the pulse current is removed, indicating that the pulse current can promote particle diffusion and pore closure. Example 1 reduces costs by using a high praseodymium ratio (neodymium: praseodymium = 5:1) while maintaining a high sputtering rate of 32.5 nm / min. Although Comparative Example 2 completely removes transition metals to reduce costs, the sputtering rate plummets to 19.3 nm / min, demonstrating the irreplaceable role of transition metals in sputtering efficiency and the importance of balanced component design.

[0083] This application provides a rare earth metal target material and its preparation method. Through the coordinated optimization of component design and integrated preparation process, it achieves an effective balance between core function maintenance and cost while strictly controlling oxygen impurities, significantly refining micro grains, and greatly improving the density of the target material. Specifically, it adopts hydrogen deep reduction combined with argon gas classification to achieve low oxygen content control, avoiding abnormal sputtering discharge and fluctuations in film performance; introduces a nano-dispersant coated with silica on the surface to cooperate with multi-stage ball milling and hot pressing process to form a uniform and fine grain structure to ensure the consistency of sputtering film thickness; eliminates pore defects with the help of staged temperature and pressure control, pulse current assistance and slow cooling treatment, improves target material utilization and film surface quality; at the same time, accurately controls the neodymium and praseodymium ratio and low dysprosium addition, combines the concentrate short process extraction process, and significantly reduces the cost of raw materials while retaining key characteristics such as perpendicular magnetic anisotropy, providing a highly reliable and efficient core material solution for thin film deposition in the fields of high-performance magneto-optical devices, sensors, etc.

[0084] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A rare earth metal target, characterized in that: The target material comprises the following elements in percentage by mass: 70-90% rare earth metal, 5-15% transition metal, and 3-10% dispersant; The rest are unavoidable impurities, among which the oxygen content is less than 300ppm and the iron content is less than 100ppm.

2. The rare earth metal target according to claim 1, characterized in that: The rare earth metals are Nd, Pr and Dy, wherein the mass ratio of Nd to Pr is 3-5:1, and the added amount of Dy is 1-5% of the total mass of the target material.

3. The rare earth metal target according to claim 1, characterized in that: The transition metal is selected from one of Ti, Zr and Mo.

4. The rare earth metal target according to claim 1, characterized in that: The dispersant comprises boron nitride with a particle size of 50-200 nm, and the surface of the boron nitride is coated with a silicon dioxide layer with a thickness of 1-3 nm.

5. A method for preparing a rare earth metal target according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (a) Extraction: The rare earth concentrate is subjected to a combined mechanical activation and acid leaching treatment to obtain rare earth oxide powder with a particle size D50 of 5-20 μm; (b) Modification: The rare earth oxide powder is mixed with a transition metal powder and a dispersant, and ball milled under an argon atmosphere for 4-12 hours at a ball-to-powder ratio of 10-20:1 and a rotation speed of 200-400 rpm to obtain a modified powder; (c) Reduction: The modified powder is placed in a vacuum induction furnace and reduced at 800-950°C for 2-4 hours using hydrogen as a reducing agent until the oxygen content of the powder is ≤500 ppm. The powder with a particle size distribution D90 <30 μm obtained by argon gas flow classification is the reduced powder; (d) Molding: The reduced powder is placed into a graphite mold, pressurized to 20-50 MPa in a hot pressing sintering furnace, and heated to 1100-1300°C for 1-3 hours; (e) Cooling: Slowly cool to below 200°C at a rate of 10-30°C / min, then take out of the furnace and continue cooling to room temperature to obtain the rare earth metal target.

6. The method for preparing a rare earth metal target according to claim 5, wherein: In step (a), the rare earth concentrate is bastnaesite or monazite, and the REO content after flotation is ≥90%; Mechanical activation uses a planetary ball mill with an activation time of 30-60 minutes and an impact energy of 5-15J / time; Acid leaching uses a mixed acid of hydrochloric acid and nitric acid in a volume ratio of 3-5:1, a leaching temperature of 60-90°C, and a leaching time of 2-4 hours.

7. The method for preparing a rare earth metal target according to claim 5, wherein: The hot pressing sintering in step (d) is divided into two stages: the first stage is to increase the temperature to 800° C. at 5-10° C. / min and hold the temperature for 10-20 minutes; the second stage is to increase the temperature to the target temperature at 2-5° C. / min.

8. The method for preparing a rare earth metal target according to claim 7, wherein: In the second stage, a pulse current is also applied simultaneously with a frequency of 10-50 Hz and a current density of 50-200 A / cm2.

9. The method for preparing a rare earth metal target according to claim 5, wherein: In step (d), after forming, the surface of the target material is sandblasted with a sand particle size of 80-120 mesh, a sandblasting pressure of 0.2-0.5 MPa, and a roughness Ra of 0.8-1.5 μm.

10. The method for preparing a rare earth metal target according to claim 5, wherein: During the cooling step (e), the target material is subjected to vacuum annealing after being taken out of the furnace, with the annealing temperature being 500-700°C, the time being 1-2 hours, and the vacuum degree being ≤1×10 -3 Pa.

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