Nickel ferrite target material and method for producing the same

Abstract

The application relates to the technical field of target material preparation, and provides a nickel ferrite target material and a preparation method thereof, which comprises the following steps: providing NiO powder and Fe2O3 powder, and sequentially mixing, ball milling, drying and calcining the NiO powder and the Fe2O3 powder with a dispersant and a solvent to obtain NiFe2O4 calcined powder; mixing, ball milling and drying Fe3O4 powder doped with A, the NiFe2O4 calcined powder, the dispersant and the solvent to obtain mixed powder; A is at least one selected from MnO2, CuO, CoO, Cr2O3 and MgO; and the mixed powder is subjected to pre-pressing treatment and hot-pressing treatment, and then is machined to obtain the nickel ferrite target material. The Fe3O4 powder doped with A is introduced, Fe 2+ and Fe 3+ exist on octahedral sites in the crystal structure of the Fe3O4 powder doped with A, so that electron exchange can be realized through oxygen ion bridges, a conductive path is constructed in the material, the conductivity of the target material is improved, and the direct-current sputtering process requirement is met.

Description

Technical Field

[0001] This application belongs to the field of target preparation technology, and particularly relates to a nickel ferrite target and its preparation method. Background Technology

[0002] Nickel ferrite (NiFe2O4) is a negative temperature coefficient (NTC) ceramic material whose resistivity decreases exponentially with increasing temperature. Therefore, it is widely used in the fabrication of thermistors for household appliances, automotive electronics, and medical devices. However, current NTC thermistors are typically ceramic bodies, and their size is difficult to reduce due to limitations in sintering processes, making integration with silicon-based circuits inconvenient. This has driven thin-film fabrication as a crucial development direction. With the evolution of electronic devices towards miniaturization, surface-mount design, and high performance, the fabrication of soft magnetic ferrite thin films using physical vapor deposition (PVD) techniques such as magnetron sputtering has become an inevitable trend.

[0003] In thin film preparation, reactive sputtering with nickel-iron alloy targets or direct sputtering with NiFe2O4 targets are commonly used. The former is prone to incomplete reactions, leading to uneven oxygen content and residual metallic phases in the film, thus affecting its functional properties. The latter, due to the extremely high resistivity of NiFe2O4, makes it difficult to maintain stable glow discharge in DC magnetron sputtering, resulting in process instability, low deposition rates, and target loss. While radio frequency magnetron sputtering can sputter insulating targets, it suffers from limitations such as complex equipment, high cost, low deposition rates, and difficulty in controlling film uniformity. Existing methods to improve the conductivity of NiFe2O4 targets by doping with metal powders or conductive oxides may introduce impurity phases, affecting the final purity and performance of the film.

[0004] Therefore, how to effectively improve the conductivity of NiFe2O4 target material to meet the requirements of DC sputtering process while ensuring that the purity and functional properties of NiFe2O4 film are not compromised is a key problem that urgently needs to be solved to promote the thin film production and application of this material. Summary of the Invention

[0005] The purpose of this application is to provide a nickel ferrite target and its preparation method, which aims to solve the problem that NiFe2O4 target material cannot be coated by DC sputtering due to its poor conductivity.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0007] In a first aspect, this application provides a method for preparing a nickel ferrite target, comprising the following steps:

[0008] NiO powder and Fe2O3 powder are available;

[0009] The NiO powder, the Fe2O3 powder, the dispersant and the solvent were sequentially mixed, ball-milled, dried and calcined to obtain NiFe2O4 calcined powder.

[0010] Fe3O4 powder doped with A, calcined NiFe2O4 powder, dispersant, and solvent are mixed, ball-milled, and dried to obtain a mixed powder; A is selected from at least one of MnO2, CuO, CoO, Cr2O3, and MgO.

[0011] The mixed powder is pre-pressed and hot-pressed, and then machined to obtain a nickel ferrite target.

[0012] Secondly, this application provides a nickel ferrite target material, which is prepared by the method for preparing nickel ferrite target material provided in this application.

[0013] Compared with the prior art, this application has the following beneficial effects:

[0014] (1) By introducing Fe3O4 powder doped with A, the conductivity of the target material was significantly improved. Fe3O4 crystal structure contains Fe... 2+ and Fe 3+ Electron exchange can occur through oxygen ion bridges. This forms continuous electron transition channels; the cation of A (Mn) 4+ Cu 2+ Co 2+ Cr 3+ Mg 2+ After the solid solution enters the Fe3O4 lattice, it produces a "pinning effect," which enhances the thermal stability and structural integrity of the Fe3O4 phase. This effectively inhibits phase transformation or decomposition during hot pressing and sintering, thereby avoiding degradation of conductivity and ensuring the reliability of the conductive network.

[0015] (2) A two-part synthesis process is adopted, namely, NiO powder and Fe2O3 powder are first calcined to synthesize NiFe2O4 calcined powder, and then it is hot-pressed and sintered with Fe3O4 powder doped with A. On the one hand, this avoids Fe3O4 from decomposing into FeO and O2 at high temperature and being oxidized into high resistivity Fe2O3 after cooling and contacting air. On the other hand, it also prevents uncontrollable solid-phase side reactions from the direct co-firing of NiO, Fe2O3 and Fe3O4, thereby ensuring the structural purity and performance stability of the target material with NiFe2O4 as the main phase.

[0016] (3) The hot pressing sintering process can achieve rapid densification of the target material under relatively low temperature, short time and reducing / vacuum atmosphere conditions, which greatly reduces the risk of Fe3O4 being decomposed and then oxidized, and effectively protects its conductive network. At the same time, the instantaneous high pressure provided by hot pressing promotes tight bonding between particles, which not only improves the density and mechanical strength of the target material, but also helps the Fe3O4 conductive phase to be uniformly distributed in the NiFe2O4 matrix, thereby finally obtaining a nickel ferrite target material with excellent conductivity and dense structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a process flow diagram of the preparation method of the nickel ferrite target provided in the embodiments of this application. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0020] The first aspect of this application provides a method for preparing a nickel ferrite target, such as... Figure 1 As shown, it includes the following steps:

[0021] S1: Provides NiO powder and Fe2O3 powder;

[0022] S2: NiO powder, Fe2O3 powder, dispersant and solvent are sequentially mixed, ball-milled, dried and calcined to obtain NiFe2O4 calcined powder;

[0023] S3: Fe3O4 powder doped with A, calcined NiFe2O4 powder, dispersant and solvent are mixed, ball-milled and dried to obtain mixed powder; A is selected from at least one of MnO2, CuO, CoO, Cr2O3 and MgO;

[0024] S4: The mixed powder is pre-pressed and hot-pressed, and then machined to obtain nickel ferrite target material.

[0025] The method for preparing nickel ferrite targets provided in this application significantly improves the conductivity of the target material by introducing Fe3O4 powder doped with alumina. Fe3O4 crystal structure simultaneously contains Fe... 2+ and Fe 3+ Electron exchange can occur through oxygen ion bridges. This forms continuous electron transition channels; the cation of A (Mn) 4+ Cu 2+ Co 2+ Cr 3+ Mg 2+The "pinning effect" generated when NiO and Fe2O3 powders are dissolved into the Fe3O4 lattice enhances the thermal stability and structural integrity of the Fe3O4 phase, effectively suppressing phase transformation or decomposition during hot-pressing sintering and thus preventing conductivity degradation and ensuring the reliability of the conductive network. A two-part synthesis process is employed: first, NiO powder and Fe2O3 powder are calcined to synthesize NiFe2O4 calcined powder; then, this powder is hot-pressed and sintered with A-doped Fe3O4 powder. This avoids the decomposition of Fe3O4 into FeO and O2 at high temperatures, followed by oxidation to high-resistivity Fe2O3 upon cooling and contact with air. It also prevents uncontrollable solid-phase side reactions from direct co-firing of NiO, Fe2O3, and Fe3O4, ensuring the structural purity and performance stability of the target material with NiFe2O4 as the main phase. The hot-pressing sintering process enables rapid densification of the target material under relatively low temperature, short time, and reducing / vacuum atmosphere conditions, significantly reducing the risk of Fe3O4 oxidation and effectively protecting its conductive network. Meanwhile, the instantaneous high pressure provided by hot pressing promotes tight bonding between particles, which not only improves the density and mechanical strength of the target material, but also helps the Fe3O4 conductive phase to be uniformly distributed in the NiFe2O4 matrix, thus ultimately obtaining a nickel ferrite target material with excellent conductivity and dense structure.

[0026] In step S1 above, in this embodiment, the mass ratio of NiO powder to Fe2O3 powder is (1~1.2):1. This mass ratio range provides a precise stoichiometric basis for the high-temperature solid-state reaction to generate nickel ferrite (NiFe2O4) calcined powder. The purity of NiO powder and Fe2O3 powder is ≥99.99%.

[0027] In step S2 above, in this embodiment, the calcination atmosphere is air, the temperature is 950~1200℃, and the time is 4~6h. The calcination conditions in this embodiment facilitate the full reaction of NiO and Fe2O3 to generate NiFe2O4 calcined powder.

[0028] In the examples, the dispersant is selected from at least one of polyethylene glycol, hexadecyl sulfonate, polycarboxylate, polyacrylate, or triethanolamine. The amount of dispersant added is 0.3-1% of the total mass of NiO powder and Fe2O3 powder.

[0029] In the examples, the solvent is selected from ethanol or deionized water.

[0030] In step S3 of the above embodiment, the step of preparing Fe3O4 powder doped with A includes: dissolving the soluble metal salt, ferrous salt, and ferric salt corresponding to A in deoxygenated distilled water to obtain a mixed salt solution; adding a precipitant and a complexing agent to the mixed salt solution under an inert atmosphere to carry out a co-precipitation reaction to generate a hydroxide colloid; concentrating, washing, and drying the hydroxide colloid, and then calcining it at 600-950°C for 6-12 hours under a vacuum or reducing atmosphere to obtain Fe3O4 powder doped with A. Using deoxygenated distilled water can effectively suppress the Fe in the ferrous salt. 2+ It is oxidized to Fe during the reaction. 3+ In this embodiment, the soluble metal salt, ferrous salt, and ferric salt corresponding to A are first dissolved together, so that the doped A ions react with Fe. 2+ Fe 3+ Uniform mixing lays the foundation for uniform doping; co-precipitation under an inert atmosphere effectively protects Fe. 2+ It must not be oxidized, which is a prerequisite for the final formation of Fe3O4 instead of Fe2O3; finally, calcination in an oxygen-deficient environment can prevent Fe3O4 from being oxidized, and at the same time allow the metal ions doped with A to enter the Fe3O4 lattice, and finally obtain Fe3O4 powder doped with A.

[0031] In the examples, the soluble metal salt corresponding to A is selected from at least one of manganese chloride, copper chloride, copper nitrate, copper sulfate, cobalt chloride, cobalt nitrate, chromium chloride, chromium sulfate, magnesium chloride, and magnesium nitrate.

[0032] In the examples, the ferrous salt is selected from FeSO₄. 4· 7H2O.

[0033] In the examples, the iron salt is selected from FeCl₂. 3· 6H2O.

[0034] In the embodiments, the precipitant is selected from a saturated urea solution.

[0035] In the examples, the complexing agent is selected from ammonium chloride or ammonium nitrate.

[0036] In the embodiments, the mass ratio of calcined NiFe2O4 powder to A-doped Fe3O4 powder is (85~95):(5~15); within this mass ratio range, Fe3O4 can provide an appropriate amount of Fe. 2+ , and Fe 3+ Electron exchange occurs This creates continuous electron transition channels, constructs a conductive network within the material, and enhances the performance of NiFeO. x The conductivity of the target material has minimal impact on the spinel structure stability, magnetic and electrical transport coupling performance, and purity of the NiFe2O4 main phase, thus maintaining good negative temperature coefficient stability.

[0037] In this embodiment, the content of A in the A-doped Fe3O4 powder is 1~5wt%. Within the range of A content in this embodiment, it can be ensured that the metal elements in A are dissolved into the Fe3O4 lattice in a substitution or interstitial manner, forming a lattice pinning effect, which enhances the thermal stability and structural integrity of the Fe3O4 phase, thereby suppressing the degradation of conductivity caused by phase transformation or decomposition and subsequent oxidation during subsequent hot pressing, and ensuring the reliability of the conductive network.

[0038] In the examples, the particle size of the mixed powder is 5~20μm.

[0039] In the examples, the dispersant is selected from at least one of polyethylene glycol, hexadecyl sulfonate, polycarboxylate, polyacrylate, or triethanolamine. The amount of dispersant added is 0.3-1% of the total mass of Fe3O4 powder and NiFe2O4 calcined powder doped with A.

[0040] In the examples, the solvent is selected from ethanol or deionized water.

[0041] In the above-mentioned step S4, the hot pressing process includes: first heating to 500~600℃ and holding for 20~40 minutes; then heating to 700~800℃ and holding for 60~90 minutes; then heating to 950~1200℃ and pressurizing to 10~30MPa, and holding for 60~120 minutes; after the holding is completed, the pressure is released and the furnace is cooled to room temperature. In the low-temperature stage of 500-600℃, adsorbed water, bound water, and organic matter in the powder are slowly decomposed and fully discharged to prevent rapid vaporization in the subsequent high-temperature stage, which could lead to cracks or pores in the target material. In the medium-temperature stage of 700-800℃, the powder particles come into contact with each other and form necks under thermal activation, resulting in preliminary sintering and densification, laying the structural foundation for subsequent high-temperature densification. In the high-temperature holding pressure stage of 950-1200℃, the applied high pressure provides a strong sintering driving force, significantly promoting material migration and accelerating pore shrinkage, thereby rapidly eliminating closed pores and enabling the target material to achieve high density and grain uniformity that is difficult to achieve with ordinary pressure sintering. Simultaneously, the entire process is carried out under vacuum or a reducing atmosphere, effectively preventing the Fe3O4 conductive phase from being oxidized to the high-resistivity Fe2O3, ensuring the conductivity of the target material.

[0042] The second aspect of this application provides a nickel ferrite target material, which is prepared by the method for preparing nickel ferrite target material provided in this application.

[0043] The nickel ferrite target provided in this application embodiment is prepared by the method provided in this application embodiment, and therefore has excellent conductivity, which can meet the process requirements of DC sputtering.

[0044] The following description is based on specific embodiments.

[0045] Example 1

[0046] This embodiment provides a method for preparing a nickel ferrite target, including the following steps:

[0047] (1) Preparation of NiFe2O4 calcined powder: Weigh appropriate amounts of NiO powder (purity ≥99.99%) and Fe2O3 powder (purity ≥99.99%) in a mass ratio of 1:1; add NiO powder, Fe2O3 powder, polyethylene glycol and pure water to a ball mill for ball milling and mixing; after drying and sieving, the resulting slurry is calcined at 1100℃ for 5h in air atmosphere to obtain NiFe2O4 calcined powder; the amount of polyethylene glycol added is 0.5% of the total mass of NiO powder and Fe2O3 powder;

[0048] (2) Preparation of Fe3O4 powder doped with MnO2: Weigh appropriate amounts of manganese chloride tetrahydrate (MnCl2·4H2O) and ferrous sulfate (FeSO4) in a mass ratio of 1:17.1:33.2. 4· 7H2O) and ferric chloride (FeCl) 3· 6H2O) was dissolved in deoxygenated distilled water to obtain a mixed salt solution; under argon protection, saturated urea solution and ammonium chloride solution were added to the mixed salt solution, and a co-precipitation reaction was carried out at 90℃ to generate hydroxide colloid; after the hydroxide colloid was concentrated, washed and dried, it was placed in a vacuum furnace and calcined at 800℃ for 8h under the protection of an argon-hydrogen mixed atmosphere with an argon-hydrogen volume ratio of 94:6 to obtain Fe3O4 powder doped with MnO2;

[0049] (3) Ingredient mixing: Weigh appropriate amounts of NiFe2O4 calcined powder and Fe3O4 powder doped with MnO2 in a mass ratio of 90:10, and mix them with polyethylene glycol and deionized water by ball milling. After drying the resulting slurry, pass it through a 100-mesh sieve to obtain a mixed powder with a particle size of about 5~20μm. The amount of polyethylene glycol added is 0.5% of the total mass of NiFe2O4 calcined powder and Fe3O4 powder doped with MnO2.

[0050] (4) Hot pressing sintering: The mixed powder is filled into a graphite mold and pre-formed under a pressure of 30 MPa. Then, the vacuum hot press furnace is evacuated until the vacuum degree reaches 10. -2 When the pressure is below Pa, the temperature is initially increased to 550℃ at 2℃ / min and held for 30min to fully degas and degrease; then the temperature is increased to 750℃ at 1.5℃ / min and held for 60min; then the temperature is increased to 1100℃ at 1℃ / min, and the pressure is gradually increased to 20MPa and maintained at this temperature and pressure for 90min. After the holding and pressure holding are completed, the pressure is released and the material is cooled to room temperature with the furnace to obtain a nickel ferrite target semi-finished product.

[0051] (5) Machining: Cut the nickel ferrite target semi-finished product, grind the surface and trim the size to obtain the nickel ferrite target.

[0052] Example 2

[0053] This embodiment provides a method for preparing a nickel ferrite target, which differs from Example 1 in that:

[0054] In step (2), Fe3O4 powder doped with CoO is prepared, and "manganese chloride (MnCl2·4H2O)" is replaced with "cobalt chloride hexahydrate (CoCl2·6H2O)".

[0055] In step (3), “Fe3O4 powder doped with MnO2” is replaced with “Fe3O4 powder doped with CoO”.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing a nickel ferrite target, which differs from Example 1 in that:

[0058] Omit step (2) and replace “Fe3O4 powder doped with MnO2” in step (3) with “Fe3O4 powder”.

[0059] Comparative Example 2

[0060] This comparative example provides a method for preparing a nickel ferrite target, which differs from Example 1 in that:

[0061] Omit step (2) and replace “Fe3O4 powder doped with MnO2” in step (3) with “ZnO powder”.

[0062] Comparative Example 3

[0063] This comparative example provides a method for preparing a nickel ferrite target, which differs from Example 1 in that:

[0064] Replace step (4) with “cold isostatic pressing and air sintering, i.e.: fill the mixed powder into the mold, and then put it into a cold isostatic pressing (CIP) machine to press and form. The CIP pressure is 220MPa, and a green blank with a relative density of 62% is obtained. The green blank is put into a sintering furnace, and heated to 400℃ at 1.5℃ / min in an air atmosphere, and held for 12h. Then it is heated to 1400℃ at 1℃ / min, held for 12h, and then cooled with the furnace to obtain a nickel ferrite target material.”

[0065] Comparative Example 4

[0066] This comparative example provides a method for preparing a nickel ferrite target, comprising the following steps:

[0067] (1) Mixing of ingredients: Weigh appropriate amounts of NiO powder, Fe2O3 powder, MnO2 powder and Fe3O4 powder in a mass ratio of 28.7: 61.3: 0.3: 9.7, and mix them with polyethylene glycol and deionized water by ball milling. Then add polyvinyl alcohol and mix evenly. After drying the slurry, pass it through a 100-mesh sieve to obtain a mixed powder with a particle size of about 5~20μm.

[0068] (2) Hot pressing sintering: The mixed powder is filled into a graphite mold and pre-formed under a pressure of 30 MPa. Then, the vacuum hot press furnace is evacuated until the vacuum degree reaches 10. -2 When the pressure is below Pa, the temperature is initially increased to 550℃ at 2℃ / min and held for 30min to fully degas and degrease; then the temperature is increased to 750℃ at 1.5℃ / min and held for 60min; then the temperature is increased to 1100℃ at 1℃ / min, and the pressure is gradually increased to 20MPa and maintained at this temperature and pressure for 90min. After the holding and pressure holding are completed, the pressure is released and the material is cooled to room temperature with the furnace to obtain a nickel ferrite target semi-finished product.

[0069] (3) Machining: Cut the nickel ferrite target semi-finished product, grind the surface and trim the size to obtain the nickel ferrite target.

[0070] Relevant performance test analysis:

[0071] 1. The resistivity of the nickel ferrite targets prepared in Examples 1-2 and Comparative Examples 1-4 was tested using a four-probe tester.

[0072] 2. The actual density of the nickel ferrite targets prepared in Examples 1-2 and Comparative Examples 1-4 was tested using the Archimedes density test method. The relative density was calculated as follows: relative density = actual density / theoretical density × 100%, based on the theoretical density.

[0073] 3. First, using a magnetron sputtering device under the same deposition conditions, the nickel ferrite targets prepared in Examples 1-2 and Comparative Examples 1-2 were sputtered onto an Al2O3 substrate to obtain a nickel ferrite thin film with a thickness of about 500 nm. Then, interdigitated silver electrodes were printed on the nickel ferrite thin film using screen printing to form a thin film NTC thermistor.

[0074] The thin-film NTC thermistor was placed in a constant temperature bath at 25°C for resistance testing to obtain the resistance value at 25°C. Then, the thin-film NTC thermistor was placed in a constant temperature bath at 85°C for resistance testing to obtain the resistance value at 85°C. Finally, the B value of the thin-film NTC thermistor was calculated based on the resistance values ​​at 25°C and 85°C.

[0075] The test results are shown in Table 1 below.

[0076] Table 1

[0077]

[0078] As can be seen from Table 1, the resistivity of the nickel ferrite targets prepared in Examples 1-2 and the corresponding B-values ​​of the thin-film NTC thermistors are significantly better than those in Comparative Examples 1-2. This is mainly due to the stable conductive network formed by the addition of Fe3O4 powder doped with MnO2 or CoO in the embodiments of this application. 4+ or Co 2+ The "pinning effect" effectively inhibits the decomposition of Fe3O4 into FeO and O2 during hot pressing, preventing oxidation upon contact with air during cooling and thus protecting the Fe... 2+ / Fe 3+ The unobstructed electron transition channels significantly reduce the resistivity of the target material, enabling it to meet the process requirements of DC sputtering. Furthermore, the embodiments of this application employ a two-step process: first, calcining to form NiFe2O4 powder, and then vacuum hot-pressing it with Fe3O4 powder doped with MnO2 or CoO. This effectively suppresses harmful side reactions and helps maintain the structural integrity of the NiFe2O4 main phase. Consequently, the resulting NTC thermistor exhibits excellent NTC characteristics, with its B value approaching the theoretical value of pure NiFe2O4 (3400K).

[0079] In contrast, the Fe3O4 added in Comparative Example 1 lacked thermal stability under hot pressing and high temperatures, easily decomposing into FeO and O2 at high temperatures. Upon cooling and contact with air, it was oxidized to Fe2O3, leading to Fe... 2+ The reduction in electron transition channels and the incomplete formation of the conductive network lead to an increase in the resistivity of the target material. Furthermore, the instability of Fe3O4 during the hot pressing process may also react with the NiFe2O4 main phase to produce impurity phases, thereby affecting the crystal structure and cation distribution of the film and resulting in a decrease in the B value.

[0080] Although adding ZnO to Comparative Example 2 reduced the resistivity of the nickel ferrite target, the corresponding thin-film NTC thermistor's B value deteriorated significantly, falling below 2000 kJ, which is insufficient for practical applications. The main reason is likely that the introduction of ZnO disrupts the main phase structure and cation distribution of NiFe₂O₄, such as the Zn... 2+ Occupying the tetrahedral position forces Fe 3+ Entering the octahedral position alters the conductivity mechanism or introduces impurities, leading to a deterioration in the performance of NTC thermistors.

[0081] In Comparative Example 3, the powder was sintered at atmospheric pressure in an air atmosphere. This resulted in the complete oxidation of Mn-doped Fe3O4 into high-resistivity Fe2O3, causing the conductive network to fail and leading to a high resistivity of the target material. Furthermore, the driving force for atmospheric pressure sintering was insufficient, resulting in a slow and incomplete densification process with numerous residual pores, leading to a low relative density. In Comparative Example 4, all powder raw materials were directly mixed and hot-pressed for sintering. At high temperatures, complex solid-state reactions may occur, leading to uneven shrinkage or gas generation, generating internal stress and cracks, and hindering densification. Therefore, the resistivity and relative density of the nickel-ferrite targets prepared in Comparative Examples 3 and 4 were severely degraded, and neither could meet the process requirements of DC magnetron sputtering.

[0082] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a nickel ferrite target, characterized in that, Includes the following steps: NiO powder and Fe2O3 powder are provided; the mass ratio of NiO powder to Fe2O3 powder is (1~1.2):1; The NiO powder, the Fe2O3 powder, the dispersant and the solvent were sequentially mixed, ball-milled, dried and calcined to obtain NiFe2O4 calcined powder. Fe3O4 powder doped with A, calcined NiFe2O4 powder, dispersant, and solvent are mixed, ball-milled, and dried to obtain a mixed powder; A is selected from at least one of MnO2, CuO, CoO, Cr2O3, and MgO; the mass ratio of calcined NiFe2O4 powder to Fe3O4 powder doped with A is (85~95):(5~15); the content of A in the Fe3O4 powder doped with A is 1~5 wt%. The mixed powder is pre-pressed and hot-pressed, and then machined to obtain a nickel ferrite target material; The hot pressing process includes: first heating to 500~600℃ and holding at that temperature for 20~40 minutes; Continue heating to 700~800℃ and hold for 60~90 minutes; continue heating to 950~1200℃ and pressurize to 10~30MPa, and hold for 60~120 minutes; after holding, release the pressure and cool with the furnace to room temperature.

2. The preparation method according to claim 1, characterized in that, The steps for preparing the Fe3O4 powder doped with A include: Dissolve the soluble metal salt, ferrous salt, and ferric salt corresponding to A in deoxygenated distilled water to obtain a mixed salt solution; Under an inert atmosphere, a precipitant and a complexing agent are added to the mixed salt solution to carry out a co-precipitation reaction, generating hydroxide colloids; After the hydroxide colloid is concentrated, washed and dried, it is calcined at 600~950℃ for 6~12h in a vacuum or reducing atmosphere to obtain Fe3O4 powder doped with A.

3. The preparation method according to claim 2, characterized in that, The soluble metal salt corresponding to A is selected from at least one of manganese chloride, copper chloride, copper nitrate, copper sulfate, cobalt chloride, cobalt nitrate, chromium chloride, chromium sulfate, magnesium chloride, and magnesium nitrate.

4. The preparation method according to claim 2, characterized in that, The ferrous salt is selected from FeSO₄. 4· 7H2O.

5. The preparation method according to claim 2, characterized in that, The iron salt is selected from FeCl₂ 3· 6H2O.

6. The preparation method according to claim 2, characterized in that, The precipitant is selected from a saturated urea solution; And / or, the complexing agent is selected from ammonium chloride or ammonium nitrate.

7. The preparation method according to claim 1, characterized in that, The calcination process is carried out in an air atmosphere at a temperature of 950-1200℃ for 4-6 hours.

8. The preparation method according to claim 1, characterized in that, The particle size of the mixed powder is 5~20μm.

9. The preparation method according to claim 1, characterized in that, The dispersant is selected from at least one of polyethylene glycol, hexadecyl sulfonate, polycarboxylate, polyacrylate, or triethanolamine; And / or, the solvent is selected from ethanol or deionized water.

10. A nickel-ferrite target material, characterized in that, It is prepared by the method for preparing nickel ferrite target material according to any one of claims 1 to 9.

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