Low-loss wide-temperature manganese-zinc ferrite material and preparation process thereof

Abstract

The application discloses a kind of low-loss wide-temperature manganese-zinc ferrite materials and preparation process thereof, belong to magnetic material technical field.Prepared by the following raw materials: Fe2O3 45-55 parts, Mn3O4 20-30 parts, ZnO 15-25 parts, Mg-V-Si in-situ reaction type composite dopant 2-4 parts, CaCO3 0.5-1.5 parts, Nb2O 5 0.1-0.3 parts, surfactant 0.2-0.8 parts, forming aid 1-2 parts.By preparing Mg-V-Si composite dopant, combined with three-step gradient temperature + double-platform gradient cooling sintering process, the material obtained in-40 DEG C to 180 DEG C wide temperature range power loss ≤308 kW / m³, initial permeability ≥3720, saturation magnetic induction intensity ≥542 mT, Curie temperature ≥258 DEG C, can meet the stringent demand of new energy vehicles, aerospace and other fields to wide-temperature low-loss magnetic material.

Description

Technical Field

[0001] This invention belongs to the field of magnetic materials technology, specifically relating to a low-loss, wide-temperature manganese-zinc ferrite material and its preparation process. Background Technology

[0002] Driven by market demand, switching power supply modules for new energy vehicles are increasingly developing towards lightweight, miniaturized, and high-efficiency designs. Power electronic transformers, as a crucial component of switching power supplies, play a vital role in energy conversion and transmission, typically accounting for 20-35% of the module's volume and weight. Traditional wound transformers, due to their complex windings, poor heat dissipation, high leakage inductance, and large size, significantly limit the development of lightweight, miniaturized, and high-efficiency automotive switching power supply modules. In contrast, planar transformers, with their wide and flat magnetic core structure, are significantly smaller than traditional wound transformers. Furthermore, the wide and flat magnetic core structure effectively increases the heat dissipation area and reduces leakage inductance between windings, thereby reducing power loss and improving overall energy conversion efficiency. Therefore, planar transformers are widely used in switching power supply modules for new energy vehicles.

[0003] Due to its excellent electromagnetic properties, MnZn power ferrite materials are often used as magnetic cores in switching power supply modules for new energy vehicles. The core's losses and volume account for the majority of the total losses and volume of the switching power supply. To keep pace with the miniaturization, lightweighting, and efficiency improvements in switching power supplies, high-power-density switching power supplies urgently require MnZn power ferrite materials with excellent electromagnetic properties such as high saturation magnetic flux density, high initial permeability, high Curie temperature, and ultra-low power consumption over an ultra-wide temperature range. Higher saturation magnetic flux density allows for greater voltage tolerance and reduced core volume, while higher initial permeability allows for smaller transformer windings with the same inductance, facilitating device miniaturization. Furthermore, reducing power losses minimizes energy loss in switching-mode power supplies, thereby improving energy conversion efficiency. The losses of MnZn power ferrite materials are closely related to temperature, but the losses do not change linearly with temperature; their loss-temperature characteristic curve is typically a concave curve, with the lowest loss at the trough. In practical applications, the magnetic core of a switching power supply does not operate at a constant temperature. The core's operating temperature frequently deviates from the temperature of minimum core loss, leading to a sharp increase in losses and a decrease in energy conversion efficiency. The temperature characteristics of MnZn power ferrite core losses significantly affect the stability and safety of switching power supply systems used in new energy vehicles. Therefore, developing a MnZn power ferrite material with high saturation magnetic induction, high initial permeability, high Curie temperature, and low losses over a wide temperature range, and designing high-efficiency transformers based on this material, is of significant practical importance for promoting the high-quality development of the new energy vehicle industry.

[0004] In recent years, technical personnel in the industry have conducted extensive research to obtain wide-temperature, ultra-low-power magnetic materials. For example, patent CN202111420511.5 discloses a wide-temperature, low-loss, high-strength MnZn power ferrite, its preparation method, and its applications. This material has a power consumption of ≤350mW / cm² at 25℃ under conditions of 100kHz and 200mT. 3 Power consumption at 120℃ ≤350mW / cm 3 Under conditions of 1194 A / m and 50 Hz, the saturation magnetic flux density at 25℃ is ≥535 mT. This material exhibits excellent loss and saturation magnetic flux density characteristics between 25℃ and 120℃. For example, patent CN202310829822.X discloses a wide-temperature, low-loss soft magnetic manganese-zinc ferrite material suitable for 25-140℃, its preparation method, and its applications. This material also exhibits excellent loss and saturation magnetic flux density characteristics between 25℃ and 140℃, and can also meet the requirements of automotive OBCs and DC-DC converters. However, the temperature range that both of these materials can meet is limited to room temperature (25℃ to 140℃). Moreover, the loss of the wide-temperature, low-loss soft magnetic manganese-zinc ferrite material disclosed in patent CN202310829822.X increases rapidly and deteriorates after the temperature exceeds 140℃.

[0005] Therefore, the development of MnZn power ferrite materials for extreme wide-temperature operating conditions ranging from -40℃ to 150℃ or even higher is urgently needed. The key technical challenge lies in breaking through traditional compositional limitations and introducing multi-scale structural control and gradient doping synergistic strategies to construct a high-temperature resistant and stable network within the grain boundary phase and build stress-buffered microregions within the grains. This would suppress the surge in hysteresis loss at -40℃ and delay grain boundary migration and oxygen vacancy diffusion at temperatures above 150℃, thereby reducing magnetic loss fluctuations across the entire temperature range and providing irreplaceable core magnetic material support for automotive-grade high-frequency, high-power-density converters. Summary of the Invention

[0006] This invention provides a low-loss, wide-temperature manganese-zinc ferrite material and its preparation process, aiming to solve the technical challenge of maintaining excellent comprehensive performance such as low loss, high saturation magnetic induction, high initial permeability, and high Curie temperature in existing MnZn power ferrite materials under extreme temperature conditions ranging from -40℃ to 150℃ and above. Through innovative raw material formulation design, particularly the use of Mg-V-Si in-situ reactive composite dopant, combined with optimized preparation processes, especially a unique gradient sintering regime, specific microstructures can be formed within the grain boundary phase and grains of the ferrite material. This effectively suppresses the surge in hysteresis loss at low temperatures and grain boundary migration and oxygen vacancy diffusion at high temperatures, achieving reduced magnetic loss fluctuations over a wide temperature range while ensuring high saturation magnetic induction, high initial permeability, and high Curie temperature. This meets the urgent demand for wide-temperature, low-loss manganese-zinc ferrite materials in applications such as switching power supply modules for new energy vehicles.

[0007] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 45-55 parts Fe2O3, 20-30 parts Mn3O4, 15-25 parts ZnO; composite dopant: 2-4 parts Mg-V-Si in-situ reactive composite dopant; auxiliary components: 0.5-1.5 parts CaCO3, 0.1-0.3 parts Nb2O5, 0.2-0.8 parts surfactant, and 1-2 parts molding aid.

[0008] Furthermore, the specific preparation method of the Mg-V-Si in-situ reactive composite dopant is as follows: (1) Disperse nano-SiO2 powder in deionized water, add dispersant, and then process by high-energy ball milling or ultrasonic treatment to obtain nano-SiO2 sol with a solid content of 15-25%. (2) Weigh out ammonium metavanadate, magnesium salt and nano SiO2 sol obtained in step (1) according to the mass ratio (3-5): (1-2): (1). Dissolve ammonium metavanadate in hot water (65-70℃), add magnesium salt and stir to dissolve, then add nano SiO2 sol and complexing agent, adjust pH to 8-9, stir and react at 60-80℃ for 2-4 hours to obtain mixed slurry; (3) Spray dry the mixed slurry obtained in step (2) to obtain spherical precursor particles; (4) Heat-treat the spherical precursor particles obtained in step (3) at 450-600℃ for 1-2 hours to obtain Mg-V-Si in-situ reactive composite dopant.

[0009] Furthermore, the dispersant is one or more of polyethylene glycol 2000, silane coupling agent KH570, and sodium polyacrylate, and the amount added is 1.5-3.0% of the mass of nano-SiO2.

[0010] Furthermore, the magnesium salt is magnesium nitrate or magnesium acetate; the complexing agent is ethylenediaminetetraacetic acid, and the amount of ethylenediaminetetraacetic acid added is 8% to 12% of the mass of ammonium metavanadate.

[0011] Furthermore, the surfactant is one or more of Tween 80, Tween 60, or dodecyl dimethyl benzyl ammonium chloride; the molding aid is polyvinyl alcohol.

[0012] A method for preparing a low-loss, wide-temperature manganese-zinc ferrite material includes the following preparation steps: (1) Pre-sintering: Fe2O3, Mn3O4 and ZnO are mixed evenly according to the weight parts and then ground, and pre-sintered at 750-850℃ for 1.5-2.5 hours to obtain the main pre-sintered material; (2) Preparation of Mg-V-Si in-situ reactive composite dopant; (3) Secondary ball milling: The pre-calcined material obtained in step (1), the composite dopant obtained in step (2), and CaCO3, Nb2O5, surfactant, and molding aid are added to a ball mill. 5-8% of the total weight of the mixture is added to perform wet ball milling at a speed of 150-250 r / min for 3-6 hours to obtain a slurry. (4) Molding: The slurry obtained in step (3) is dried, granulated, and pressed into shape to obtain a green body; (5) Gradient sintering: The green blank obtained in step (4) is subjected to gradient sintering, which includes a three-stage gradient heating stage and a dual-platform gradient cooling stage. (6) After cooling, a wide-temperature, low-loss manganese-zinc ferrite material is obtained.

[0013] Furthermore, the three-stage heating gradient specifically includes: a first heating gradient: heating from room temperature to 650°C at a heating rate of 2-3°C / min, holding at 650°C for 1-2 hours, with air as the heating atmosphere; a second heating gradient: heating from 650°C to 950°C at a heating rate of 1-2°C / min, holding at 950°C for 1.5-2.5 hours, with the oxygen content in the heating atmosphere controlled at 5-8%; and a third heating gradient: heating from 950°C to 1200-1250°C at a heating rate of 0.5-1°C / min, holding at 1200-1250°C for 2-3 hours, with the oxygen content in the heating atmosphere controlled at 2-4%.

[0014] Furthermore, the dual-platform gradient cooling stage specifically includes: a first cooling platform: cooling from the sintering temperature to 1050℃ at a cooling rate of 3-5℃ / min, holding at 1050℃ for 2-3 hours, with the oxygen content in the cooling atmosphere controlled at 3-5%; a second cooling platform: cooling from 1050℃ to 850℃ at a cooling rate of 1-2℃ / min, holding at 850℃ for 1-2 hours, with the oxygen content in the cooling atmosphere controlled at 0.5-1%; and a final cooling: naturally cooling from 850℃ to room temperature, with the cooling atmosphere being pure nitrogen.

[0015] Furthermore, the grinding in step (1) involves grinding the mixed material to a particle size D50 of 1.0-2.0 μm; the particle size D50 of the slurry after wet ball milling in step (3) is 0.8-1.5 μm.

[0016] All raw materials used in this invention are commercially available.

[0017] The principle and beneficial effects of the technical solution of this invention are as follows: First, this invention, a Mg-V-Si in-situ reactive composite dopant, breaks through the traditional approach of single or simple composite doping. It creatively designs a Mg-V-Si ternary in-situ reactive composite dopant, constructing micro-region reaction units that can autonomously evolve during sintering through a process of "sol-gel preparation - complexation impregnation - spray drying - low-temperature pre-decomposition." The three elements, Mg, V, and Si, exhibit clear division of labor and synergy. Mg 2+ Lattice occupancy and magnetic property optimization of Mg 2+ Ionic radius and Fe 2+ / Mn 2+ Approaching the main crystal phase lattice, it forms a magnesium ferrite solid solution, which adjusts the magnetocrystalline anisotropy constant, reduces the fluctuation range of magnetic permeability in a wide temperature range, and increases the Curie temperature.

[0018] The liquid-phase sintering and grain boundary "cleaning" effect of V₂O₅: V₂O₅ has a melting point of approximately 690℃. During sintering, it forms a liquid phase, lowering the main sintering temperature to 1150-1250℃, a reduction of 50-100℃ compared to conventional processes, saving 15-20% in energy consumption; simultaneously, V₂O₅... 5+ Segregated at grain boundaries, it reacts with impurity ions to form high-resistivity compounds, significantly reducing eddy current losses.

[0019] The in-situ reaction of SiO2 and V2O5 generates a high-resistivity vanadium silicate glass phase: the pre-composite nano-SiO2 undergoes an in-situ chemical reaction with molten V2O5 to generate a continuous and dense high-resistivity vanadium silicate glass phase, which uniformly encapsulates the grains to form an "electron wall". Its effect of suppressing eddy current loss is far superior to that of simple mechanical mixing.

[0020] This glass phase has the following beneficial effects: Formation of a continuous grain boundary layer: The in-situ generated glass phase can more uniformly and densely wrap around the ferrite grains, forming a continuous high-resistivity "electron wall", which is far superior to the effect of simply mixing and adding SiO2 and V2O5 in suppressing eddy current loss; Excellent high-temperature stability: The vanadium silicate glass phase can maintain a stable structure and resistivity at high temperatures, effectively delaying grain boundary migration and oxygen vacancy diffusion at high temperatures. In addition, it is not easy to generate microcracks during repeated thermal cycles, ensuring the reliability of the material.

[0021] The synergistic effect of Mg, V, and Si elements enables the material to achieve low loss characteristics over an ultra-wide temperature range.

[0022] Second: The unique gradient sintering process of this invention is synergistically designed with Mg-V-Si in-situ reactive composite dopant, creating a material-process synergy: the dopant provides the "reaction raw materials," and the gradient process controls the "reaction process." The specific synergistic effect is as follows: (1) Synergistic effect of the third-order gradient heating stage First temperature gradient (room temperature → 650℃, hold at 650℃): Slowly raise and hold the temperature to ensure that the molding aid (PVA) is fully decomposed and eliminated, preventing cracking of the green body; magnesium salt (magnesium nitrate or magnesium acetate) begins to decompose into MgO, preparing for subsequent entry into the crystal lattice; this stage is carried out in air to ensure that the organic matter is fully oxidized.

[0023] Second temperature gradient (650→950℃, hold at 950℃): Precisely matched to the V2O5 melting temperature: 950℃ corresponds to the temperature range where V2O5 fully melts. Holding at this temperature for 1.5-2.5 hours allows the V2O5 in the composite dopant to form a liquid phase, initiating the "wetting" of nano-SiO2 and MgO, triggering an in-situ reaction to generate vanadium silicate precursors. Slow heating (1-2℃ / min) ensures full spread of the liquid phase and uniform reaction. The oxygen content is controlled at 5-8% to ensure Fe... 2+ / Fe 3+ The appropriate ratio should be maintained while preventing excessive oxidation.

[0024] Third temperature gradient (950→1200-1250℃, 1200-1250℃ holding): An extremely slow heating rate (0.5-1℃ / min) is conducive to uniform grain growth and prevents abnormal growth. During the 1200-1250℃ holding stage, the main crystalline phase is fully densified, while the vanadium silicate precursor is transformed into a stable glassy phase. A decrease in oxygen content to 2-4% is beneficial for obtaining suitable Fe. 2+ Concentration, optimize magnetic properties.

[0025] (2) Synergistic effect of the gradient cooling stage of the dual-platform First cooling platform (1200-1250→1050℃, 1050℃ insulation): Precisely matched to the precipitation temperature of vanadium silicate glass phase: 1050℃ is the optimal precipitation temperature range for vanadium silicate glass phase. Holding at this temperature for 2-3 hours allows the glass phase to fully precipitate and spread at the grain boundaries, forming a continuous, dense, high-resistivity grain boundary layer. This is significantly different from the existing techniques of rapid cooling or simply controlling the oxygen partial pressure; it is an active grain boundary control technique. The oxygen content is controlled at 3-5% to maintain an appropriate oxidizing atmosphere and promote glass phase formation.

[0026] Second cooling platform (1050→850℃, 850℃ insulation): with Fe 2+ / Fe 3+ Precise temperature matching for balanced regulation: 850℃ is the temperature for regulating Fe 2+ The key temperature range for Fe concentration. Maintaining this temperature for 1-2 hours, and optimizing Fe concentration by controlling the oxygen partial pressure (0.5-1%). 2+ / Fe 3+ The ratio is adjusted to obtain the optimal permeability and loss characteristics; slow cooling (1-2℃ / min) avoids the generation of thermal stress.

[0027] Final temperature drop (850℃ → room temperature): Natural cooling in a pure nitrogen atmosphere prevents oxidation of grain boundaries and grain surfaces at low temperatures, thus preserving the excellent interface structure that has been formed.

[0028] In summary, this invention achieves precise control over the microstructure of MnZn ferrite materials through the synergistic innovation of Mg-V-Si in-situ reactive composite dopant and a three-stage gradient heating + dual-platform gradient cooling sintering process. This invention overcomes the technical bottleneck of large loss fluctuations in MnZn ferrites over a wide temperature range in existing technologies, extending the operating temperature range from the traditional 25-120℃ to -40-180℃, while maintaining a loss below 330kW / m² across the entire temperature range. 3 This material possesses high saturation magnetic induction, high initial permeability, and high Curie temperature, thus meeting the demand for high-performance ferrite materials under extreme wide-temperature conditions, such as in switching power supply modules for new energy vehicles. The material of this invention fully meets the stringent requirements of high-end fields such as new energy vehicles, aerospace, and 5G communications for wide-temperature, low-loss magnetic materials, possessing extremely high industrial application value and broad market prospects. Attached Figure Description

[0029] Figure 1 This is a SEM image of the ferrite cross-section obtained in Example 3 of the present invention; Figure 2The images shown are SEM images of the ferrite cross sections obtained in Comparative Examples 1-6, where (a) is Comparative Example 1, (b) is Comparative Example 2, (c) is Comparative Example 3, (d) is Comparative Example 4, (e) is Comparative Example 5, and (f) is Comparative Example 6. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments, but it is not limited thereto.

[0031] Example 1 A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 45 parts Fe2O3, 20 parts Mn3O4, and 15 parts ZnO; composite dopant: 2 parts Mg-V-Si in-situ reactive composite dopant; auxiliary components: 0.5 parts CaCO3, 0.1 parts Nb2O5, 0.2 parts surfactant, and 1 part molding aid.

[0032] The specific preparation method of the Mg-V-Si in-situ reactive composite dopant is as follows: (1) Disperse nano-SiO2 powder in deionized water, add dispersant, and then process by high-energy ball milling or ultrasonic treatment to obtain nano-SiO2 sol with a solid content of 15%. (2) Weigh ammonium metavanadate, magnesium salt and nano SiO2 sol obtained in step (1) according to a mass ratio of 3:1:1. Dissolve ammonium metavanadate in hot water and add magnesium salt and stir to dissolve. Then add nano SiO2 sol and complexing agent, adjust pH to 8-9, stir and react at 60-80℃ for 2 hours to obtain mixed slurry. (3) Spray dry the mixed slurry obtained in step (2) to obtain spherical precursor particles; (4) The spherical precursor particles obtained in step (3) are heat-treated at 450°C for 2 hours to obtain Mg-V-Si in-situ reactive composite dopant.

[0033] The dispersant is polyethylene glycol 2000, and the amount added is 1.5% of the mass of nano-SiO2.

[0034] The magnesium salt is magnesium nitrate; the complexing agent is ethylenediaminetetraacetic acid (EDTA), and the amount of EDTA added is 8% of the mass of ammonium metavanadate.

[0035] The surfactant is Tween 80; the molding aid is polyvinyl alcohol.

[0036] A method for preparing a low-loss, wide-temperature manganese-zinc ferrite material includes the following preparation steps: (1) Pre-sintering: Fe2O3, Mn3O4 and ZnO are mixed evenly according to the weight parts and then ground, and pre-sintered at 750℃ for 2.5 hours to obtain the main pre-sintered material; (2) Preparation of Mg-V-Si in-situ reactive composite dopant; (3) Secondary ball milling: The main pre-burned material obtained in step (1), the composite dopant obtained in step (2), and CaCO3, Nb2O5, surfactant, and molding aid are added to a ball mill. 5% of the total weight of the mixture is added to deionized water for wet ball milling at a speed of 150 r / min for 6 hours to obtain a slurry. (4) Molding: The slurry obtained in step (3) is dried, granulated, and pressed into shape to obtain a green body; (5) Gradient sintering: The green blank obtained in step (4) is subjected to gradient sintering, which includes a three-stage gradient heating stage and a dual-platform gradient cooling stage. (6) After cooling, a wide-temperature, low-loss manganese-zinc ferrite material is obtained.

[0037] The three-stage heating process specifically includes: First heating gradient: heating from room temperature to 650℃ at a heating rate of 2℃ / min, holding at 650℃ for 1 hour, with air as the heating atmosphere; Second heating gradient: heating from 650℃ to 950℃ at a heating rate of 1℃ / min, holding at 950℃ for 1.5 hours, with the oxygen content in the heating atmosphere controlled at 5-8%; Third heating gradient: heating from 950℃ to 1200℃ at a heating rate of 0.5℃ / min, holding at 1200℃ for 2 hours, with the oxygen content in the heating atmosphere controlled at 2-4%.

[0038] The dual-platform gradient cooling stage specifically includes: a first cooling platform: cooling from the sintering temperature to 1050℃ at a cooling rate of 3℃ / min, holding at 1050℃ for 2 hours, with the oxygen content in the cooling atmosphere controlled at 3-5%; a second cooling platform: cooling from 1050℃ to 850℃ at a cooling rate of 1℃ / min, holding at 850℃ for 1 hour, with the oxygen content in the cooling atmosphere controlled at 0.5-1%; and a final cooling: natural cooling from 850℃ to room temperature, with the cooling atmosphere being pure nitrogen.

[0039] The grinding in step (1) refers to grinding the mixed material to a particle size D50 of 1.0-2.0 μm; the particle size D50 of the slurry after wet ball milling in step (3) is 0.8-1.5 μm.

[0040] Example 2 A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 50 parts Fe2O3, 25 parts Mn3O4, and 20 parts ZnO; composite dopant: 3 parts Mg-V-Si in-situ reactive composite dopant; auxiliary components: 1 part CaCO3, 0.2 parts Nb2O5, 0.5 parts surfactant, and 1.5 parts molding aid.

[0041] The specific preparation method of the Mg-V-Si in-situ reactive composite dopant is as follows: (1) Disperse nano-SiO2 powder in deionized water, add dispersant, and then process by high-energy ball milling or ultrasonic treatment to obtain nano-SiO2 sol with a solid content of 20%. (2) Weigh ammonium metavanadate, magnesium salt and nano SiO2 sol obtained in step (1) according to a mass ratio of 4:1.5:1. Dissolve ammonium metavanadate in hot water, add magnesium salt and stir to dissolve, then add nano SiO2 sol and complexing agent, adjust pH to 8-9, stir and react at 60-80℃ for 3 hours to obtain mixed slurry. (3) Spray dry the mixed slurry obtained in step (2) to obtain spherical precursor particles; (4) The spherical precursor particles obtained in step (3) are heat-treated at 500°C for 1.5 hours to obtain Mg-V-Si in-situ reactive composite dopant.

[0042] The dispersant is sodium polyacrylate, and the amount added is 2% of the mass of nano-SiO2.

[0043] The magnesium salt is magnesium acetate; the complexing agent is ethylenediaminetetraacetic acid, and the amount of ethylenediaminetetraacetic acid added is 10% of the mass of ammonium metavanadate.

[0044] The surfactant is Tween 60; the molding aid is polyvinyl alcohol.

[0045] A method for preparing a low-loss, wide-temperature manganese-zinc ferrite material includes the following preparation steps: (1) Pre-sintering: Fe2O3, Mn3O4 and ZnO are mixed evenly according to the weight parts and then ground, and pre-sintered at 850℃ for 2 hours to obtain the main pre-sintered material; (2) Preparation of Mg-V-Si in-situ reactive composite dopant; (3) Secondary ball milling: The main pre-burned material obtained in step (1), the composite dopant obtained in step (2), and CaCO3, Nb2O5, surfactant, and molding aid are added to a ball mill. 7% of the total weight of the mixture is added to deionized water for wet ball milling at a speed of 250 r / min for 3 hours to obtain a slurry. (4) Molding: The slurry obtained in step (3) is dried, granulated, and pressed into shape to obtain a green body; (5) Gradient sintering: The green blank obtained in step (4) is subjected to gradient sintering, which includes a three-stage gradient heating stage and a dual-platform gradient cooling stage. (6) After cooling, a wide-temperature, low-loss manganese-zinc ferrite material is obtained.

[0046] The three-stage heating process specifically includes: First heating gradient: heating from room temperature to 650℃ at a heating rate of 2℃ / min, holding at 650℃ for 1.5 hours, with air as the heating atmosphere; Second heating gradient: heating from 650℃ to 950℃ at a heating rate of 1℃ / min, holding at 950℃ for 2 hours, with the oxygen content in the heating atmosphere controlled at 5-8%; Third heating gradient: heating from 950℃ to 1200℃ at a heating rate of 0.5℃ / min, holding at 1200℃ for 2.5 hours, with the oxygen content in the heating atmosphere controlled at 2-4%.

[0047] The dual-platform gradient cooling stage specifically includes: a first cooling platform: cooling from the sintering temperature to 1050℃ at a cooling rate of 3℃ / min, holding at 1050℃ for 2 hours, with the oxygen content in the cooling atmosphere controlled at 3-5%; a second cooling platform: cooling from 1050℃ to 850℃ at a cooling rate of 1℃ / min, holding at 850℃ for 1.5 hours, with the oxygen content in the cooling atmosphere controlled at 0.5-1%; and a final cooling: natural cooling from 850℃ to room temperature, with the cooling atmosphere being pure nitrogen.

[0048] The grinding in step (1) refers to grinding the mixed material to a particle size D50 of 1.0-2.0 μm; the particle size D50 of the slurry after wet ball milling in step (3) is 0.8-1.5 μm.

[0049] Example 3 A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 55 parts Fe2O3, 30 parts Mn3O4, and 25 parts ZnO; composite dopant: 4 parts Mg-V-Si in-situ reactive composite dopant; auxiliary components: 1.5 parts CaCO3, 0.3 parts Nb2O5, 0.8 parts surfactant, and 2 parts molding aid.

[0050] The specific preparation method of the Mg-V-Si in-situ reactive composite dopant is as follows: (1) Disperse nano-SiO2 powder in deionized water, add dispersant, and then process by high-energy ball milling or ultrasonic treatment to obtain nano-SiO2 sol with a solid content of 25%. (2) Weigh ammonium metavanadate, magnesium salt and nano SiO2 sol obtained in step (1) according to a mass ratio of 5:2:1. Dissolve ammonium metavanadate in hot water and add magnesium salt and stir to dissolve. Then add nano SiO2 sol and complexing agent, adjust pH to 8-9, stir and react at 60-80℃ for 4 hours to obtain mixed slurry. (3) Spray dry the mixed slurry obtained in step (2) to obtain spherical precursor particles; (4) The spherical precursor particles obtained in step (3) are heat-treated at 600℃ for 1 hour to obtain Mg-V-Si in-situ reactive composite dopant.

[0051] The dispersant is polyethylene glycol 2000, and the amount added is 3.0% of the mass of nano-SiO2.

[0052] The magnesium salt is magnesium acetate; the complexing agent is ethylenediaminetetraacetic acid, and the amount of ethylenediaminetetraacetic acid added is 12% of the mass of ammonium metavanadate.

[0053] The surfactant is dodecyl dimethyl benzyl ammonium chloride; the molding aid is polyvinyl alcohol.

[0054] A method for preparing a low-loss, wide-temperature manganese-zinc ferrite material includes the following preparation steps: (1) Pre-sintering: Fe2O3, Mn3O4 and ZnO are mixed evenly according to the weight parts and then ground, and pre-sintered at 850℃ for 1.5 hours to obtain the main pre-sintered material; (2) Preparation of Mg-V-Si in-situ reactive composite dopant; (3) Secondary ball milling: The main pre-burned material obtained in step (1), the composite dopant obtained in step (2), and CaCO3, Nb2O5, surfactant, and molding aid are added to a ball mill. Deionized water of 8% of the total weight of the mixture is added for wet ball milling at a speed of 250 r / min for 6 hours to obtain a slurry. (4) Molding: The slurry obtained in step (3) is dried, granulated, and pressed into shape to obtain a green body; (5) Gradient sintering: The green blank obtained in step (4) is subjected to gradient sintering, which includes a three-stage gradient heating stage and a dual-platform gradient cooling stage. (6) After cooling, a wide-temperature, low-loss manganese-zinc ferrite material is obtained.

[0055] The three-stage heating process specifically includes: First heating gradient: heating from room temperature to 650℃ at a heating rate of 3℃ / min, holding at 650℃ for 2 hours, with air as the heating atmosphere; Second heating gradient: heating from 650℃ to 950℃ at a heating rate of 2℃ / min, holding at 950℃ for 2.5 hours, with the oxygen content in the heating atmosphere controlled at 5-8%; Third heating gradient: heating from 950℃ to 1250℃ at a heating rate of 1℃ / min, holding at 1250℃ for 3 hours, with the oxygen content in the heating atmosphere controlled at 2-4%.

[0056] The dual-platform gradient cooling stage specifically includes: First cooling platform: cooling from the sintering temperature to 1050℃ at a cooling rate of 5℃ / min, holding at 1050℃ for 3 hours, with the oxygen content in the cooling atmosphere controlled at 3-5%; Second cooling platform: cooling from 1050℃ to 850℃ at a cooling rate of 2℃ / min, holding at 850℃ for 2 hours, with the oxygen content in the cooling atmosphere controlled at 0.5-1%; Final cooling: natural cooling from 850℃ to room temperature, with the cooling atmosphere being pure nitrogen.

[0057] The grinding in step (1) refers to grinding the mixed material to a particle size D50 of 1.0-2.0 μm; the particle size D50 of the slurry after wet ball milling in step (3) is 0.8-1.5 μm.

[0058] Comparative Example 1 The difference between this comparative example and Example 3 is that no Mg-V-Si in-situ reactive composite dopant is added; the other raw material types, amounts, and preparation methods are the same as in Example 3. That is: A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 55 parts Fe2O3, 30 parts Mn3O4, and 25 parts ZnO; auxiliary components: 1.5 parts CaCO3, 0.3 parts Nb2O5, 0.8 parts surfactant, and 2 parts molding aid.

[0059] Comparative Example 2 The difference between this comparative example and Example 3 is that the MgO, V2O5, and SiO2 powders were simply mechanically mixed according to the molar ratio of Mg, V, and Si in the composite dopant of Example 3 (i.e., Mg:V:Si = 1:6:3) and then directly added, without undergoing the composite dopant preparation process of this invention. The types, amounts, and preparation methods of the remaining raw materials are the same as in Example 3. That is: A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 55 parts Fe2O3, 30 parts Mn3O4, 25 parts ZnO; composite dopant: 4 parts; auxiliary components: 1.5 parts CaCO3, 0.3 parts Nb2O5, 0.8 parts surfactant, and 2 parts molding aid.

[0060] The composite dopant is specifically prepared by mechanically mixing MgO, V5O5, and SiO2 powders according to the molar ratio of Mg, V, and Si in the composite dopant of Example 3 (i.e., Mg:V:Si = 1:6:3).

[0061] Comparative Example 3 This comparative example differs from Example 3 in that only V5O5 and SiO2 are added (Mg is not added), and the V-Si composite dopant is prepared according to the method of Example 3. The types and amounts of other raw materials and the preparation method are the same as in Example 3. That is: A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 55 parts Fe2O3, 30 parts Mn3O4, and 25 parts ZnO; composite dopant: 4 parts V-Si composite dopant; auxiliary components: 1.5 parts CaCO3, 0.3 parts Nb2O5, 0.8 parts surfactant, and 2 parts molding aid.

[0062] The V-Si composite dopant is prepared by the following method: (1) Disperse nano-SiO2 powder in deionized water, add dispersant, and then process by high-energy ball milling or ultrasonic treatment to obtain nano-SiO2 sol with a solid content of 15-25%. (2) Weigh ammonium metavanadate and nano SiO2 sol obtained in step (1) at a mass ratio of 5:1. Dissolve ammonium metavanadate in hot water and stir to dissolve. Then add nano SiO2 sol and complexing agent, adjust pH to 8-9, and stir to react at 60-80℃ for 4 hours to obtain mixed slurry. (3) Spray dry the mixed slurry obtained in step (2) to obtain spherical precursor particles; (4) The spherical precursor particles obtained in step (3) are heat-treated at 600°C for 1 hour to obtain V-Si composite dopant.

[0063] Comparative Example 4 The difference between this comparative example and Example 3 is that only MgO and SiO2 are added (V is not added), and the Mg-Si composite dopant is prepared according to the method of Example 3. The types, amounts, and preparation methods of all other raw materials are the same as in Example 3. That is: A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 55 parts Fe2O3, 30 parts Mn3O4, and 25 parts ZnO; composite dopant: 4 parts MgSi composite dopant; auxiliary components: 1.5 parts CaCO3, 0.3 parts Nb2O5, 0.8 parts surfactant, and 2 parts molding aid.

[0064] The MgSi composite dopant is prepared by the following method: (1) Disperse nano-SiO2 powder in deionized water, add dispersant, and then process by high-energy ball milling or ultrasonic treatment to obtain nano-SiO2 sol with a solid content of 25%. (2) Weigh the magnesium salt and the nano-SiO2 sol obtained in step (1) at a mass ratio of 2:1. Dissolve the magnesium salt by stirring. Then add the nano-SiO2 sol and complexing agent, adjust the pH to 8-9, and stir the reaction at 60-80℃ for 4 hours to obtain a mixed slurry. (3) Spray dry the mixed slurry obtained in step (2) to obtain spherical precursor particles; (4) The spherical precursor particles obtained in step (3) are heat-treated at 600℃ for 1 hour to obtain MgSi composite dopant.

[0065] Comparative Example 5 The difference between this comparative example and Example 3 is that only MgO and V5O5 are added (without Si), and the Mg-V composite dopant is prepared according to the method of Example 3. The types and amounts of other raw materials and the preparation method are the same as in Example 3. That is: A low-loss, wide-temperature manganese-zinc ferrite material is prepared from the following raw materials in parts by weight: main oxides: 55 parts Fe2O3, 30 parts Mn3O4, and 25 parts ZnO; composite dopant: 4 parts Mg-V in-situ reactive composite dopant; auxiliary components: 1.5 parts CaCO3, 0.3 parts Nb2O5, 0.8 parts surfactant, and 2 parts molding aid.

[0066] The specific preparation method of the Mg-V-Si in-situ reactive composite dopant is as follows: (1) Weigh out ammonium metavanadate and magnesium salt at a mass ratio of 5:2. Dissolve ammonium metavanadate in hot water and then add magnesium salt and stir to dissolve. Add complexing agent and adjust pH to 8-9. Stir and react at 60-80℃ for 4 hours to obtain mixed slurry. (2) The mixed slurry obtained in step (2) is spray-dried to obtain spherical precursor particles; (3) The spherical precursor particles obtained in step (3) are heat-treated at 600℃ for 1 hour to obtain Mg-V composite dopant.

[0067] Comparative Example 6 The difference between this comparative example and Example 3 is that the sintering process uses a conventional continuous heating + continuous cooling process, instead of the gradient sintering process of this invention. A method for preparing a low-loss, wide-temperature manganese-zinc ferrite material includes the following preparation steps: (1) Pre-sintering: Fe2O3, Mn3O4 and ZnO are mixed evenly according to the weight parts and then ground, and pre-sintered at 850℃ for 1.5 hours to obtain the main pre-sintered material; (2) Preparation of Mg-V-Si in-situ reactive composite dopant; (3) Secondary ball milling: The main pre-burned material obtained in step (1), the composite dopant obtained in step (2), and CaCO3, Nb2O5, surfactant, and molding aid are added to a ball mill. Deionized water of 8% of the total weight of the mixture is added for wet ball milling at a speed of 250 r / min for 6 hours to obtain a slurry. (4) Molding: The slurry obtained in step (3) is dried, granulated, and pressed into shape to obtain a green body; (5) Sintering: The green blank obtained in step (4) is sintered by heating from room temperature to 1250°C at 3°C / min, holding at 1250°C for 3 hours, and then cooling down to room temperature at 3°C / min. The oxygen content is controlled to be 3% throughout the sintering process. After cooling, a wide-temperature low-loss manganese-zinc ferrite material is obtained.

[0068] Comparative Example 7 Manganese-zinc ferrite materials were prepared with reference to existing technology CN202111420511.5.

[0069] Performance testing The performance of the ferrite materials obtained in Examples 1-3 and Comparative Examples 1-6 was tested using the following methods: (1) Power loss (Pcv) test: IWATSU SY-8232 BH analyzer was used. The test conditions were 100kHz, 200mT, and the test temperature range was -40℃ to 180℃. The power loss values ​​at each temperature were recorded.

[0070] (2) Initial permeability (μi) test: HP 4284A LCR tester was used, the test frequency was 10kHz, and the test temperature was 25℃.

[0071] (3) Saturation magnetic induction intensity (Bs) test: Vibrating sample magnetometer (VSM) was used, the test magnetic field was 800kA / m, and the test temperature was 25℃.

[0072] (4) Curie temperature (Tc) test: The test was conducted using an LCR-4225 inductance analyzer in conjunction with a dedicated oven.

[0073] (5) Microstructure observation: The grain morphology and density of the sample cross section were observed using a scanning electron microscope (SEM), and the grain size distribution was statistically analyzed using image analysis software.

[0074] (6) Relative density test: The density of the sintered sample was tested by Archimedes' water displacement method and the relative density was calculated.

[0075] Five samples were tested in each experimental group, and the results were averaged. The test results are shown in Table 1-2.

[0076] Table 1 Performance Test Results Table 2 Power loss Pcv (100kHz / 200mT, kW / m³) As can be seen, Examples 1–3 comprehensively outperform the comparative examples in key indicators such as initial permeability, saturation magnetic flux density, and Curie temperature. Compared with Comparative Example 1 (without dopant), Example 3 shows significantly lower power loss across the entire temperature range from -40℃ to 180℃, decreasing by 185 kW / m³ (41.1%) at -40℃ and by 282 kW / m³ (47.8%) at 180℃. Simultaneously, Example 3 exhibits a 30.5% increase in initial permeability (3720) compared to Comparative Example 1 (2850), a 7.3% increase in saturation magnetic flux density (542 mT), and a 30℃ increase in Curie temperature (258℃). This indicates that the Mg-V-Si composite dopant plays a crucial role in improving the overall magnetic properties of the material.

[0077] Compared with Comparative Example 2 (simple mechanical mixture), the loss of Example 3 was significantly lower than that of Comparative Example 2 at all temperature points, especially in the high-temperature region (160-180℃), where the difference was more significant (a reduction of 118 kW / m at 160℃). 3 A decrease of 162 kW / m² at 180℃ 3 Meanwhile, the grain size in Example 3 is more uniform. This demonstrates that the "in-situ reaction type" preparation process of the present invention enables the three elements Mg, V, and Si to achieve uniform dispersion and full reaction at the microscale, forming an effective vanadium silicate glass phase, an effect that simple mechanical mixing cannot achieve.

[0078] Compared with Comparative Examples 3-5, Comparative Example 3 showed significantly better overall performance, proving that Mg 2+ The optimization of magnetic properties by entering the crystal lattice, the reduction of hysteresis loss, the liquid-phase sintering of V₂O₅, and the cleaning of grain boundaries are all indispensable. The power loss of Comparative Example 5 remains high at all temperature points, reaching as high as 565 kW / m² at 180℃. 3 The particle size was 1.83 times that of Example 3, with a coarser grain size (6.8 μm). This indicates that without SiO2 as a framework, a high-resistivity grain boundary layer cannot be formed, and the liquid phase of V2O5 cannot be converted into a stable glassy phase, leading to a sharp increase in eddy current losses and preventing effective densification of the material. This proves that Si is a necessary framework for constructing high-resistivity grain boundaries, and its role is irreplaceable. Only the ternary in-situ reaction system of this invention (Example 3) can achieve excellent performance across the entire temperature range, proving that there is a significant synergistic effect among the three elements Mg, V, and Si, and none of them can be omitted.

[0079] Compared to Comparative Example 6, Example 3 exhibits more uniform grain size and lower losses across the entire temperature range, especially in the high-temperature region (a reduction of 112 kW / m³ at 180°C). This demonstrates that the "three-stage gradient heating + dual-platform gradient cooling" sintering process of this invention can effectively promote uniform grain growth, improve density, and optimize grain boundary structure, forming a good material-process synergy with the Mg-V-Si composite dopant. From the cross-sectional structures of Example 3 and Comparative Examples 1-6, it can be seen that the grain boundaries in Example 3 are clear and continuous with fewer pores; while the grain boundaries in the cross-sections of Comparative Examples 1-6 are blurred or broken, with aggregated or missing glass phases and more pores.

[0080] Compared with Comparative Example 7 (Prior Art CN202111420511.5), Example 3 exhibits lower losses across the entire temperature range of -40°C to 180°C, with particularly pronounced advantages under extreme conditions of low temperature (-40°C, a reduction of 85 kW / m³) and high temperature (180°C, a reduction of 152 kW / m³). The initial permeability (3720) and Curie temperature (258°C) of Example 3 are also superior to those of Comparative Example 7 (3250, 240°C). This demonstrates a significant improvement in the operating temperature range of the material of this invention, extending it from the prior art's 25-120°C to -40-180°C.

[0081] In summary, this invention, through the synergistic innovation of an in-situ reactive Mg-V-Si composite dopant and a three-stage gradient heating + dual-platform gradient cooling sintering process, successfully prepared a manganese-zinc ferrite material with extremely low power loss (≤308kW / m³), high initial permeability (3720), high saturation magnetic induction (542mT), and high Curie temperature (258℃) over an ultra-wide temperature range of -40℃ to 180℃. Complete verification using examples 1-7 demonstrates a significant synergistic effect between Mg, V, and Si, proving that none of them can be omitted. It also demonstrates that the gradient sintering process and the composite dopant of this invention form a good material-process synergistic effect. The overall performance of the material of this invention is significantly superior to existing technologies, fully meeting the stringent requirements of high-end fields such as new energy vehicles, aerospace, and 5G communications for wide-temperature, low-loss magnetic materials, possessing extremely high industrial application value and broad market prospects.

[0082] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A low-loss, wide-temperature manganese-zinc ferrite material, characterized in that, It is prepared from the following raw materials in parts by weight: main oxides: Fe2O3 45-55 parts, Mn3O4 20-30 parts, ZnO 15-25 parts; composite dopant: Mg-V-Si in-situ reactive composite dopant 2-4 parts; auxiliary components: CaCO3 0.5-1.5 parts, Nb2O5 0.1-0.3 parts, surfactant 0.2-0.8 parts, molding aid 1-2 parts.

2. The low-loss, wide-temperature manganese-zinc ferrite material according to claim 1, characterized in that, The specific preparation method of the Mg-V-Si in-situ reactive composite dopant is as follows: (1) Disperse nano-SiO2 powder in deionized water, add dispersant, and then process by high-energy ball milling or ultrasonic treatment to obtain nano-SiO2 sol with a solid content of 15-25%. (2) Weigh out ammonium metavanadate, magnesium salt and nano SiO2 sol obtained in step (1) according to the mass ratio (3-5): (1-2): (1). Dissolve ammonium metavanadate in hot water and add magnesium salt and stir to dissolve. Then add nano SiO2 sol and complexing agent, adjust pH to 8-9, and stir to react at 60-80℃ for 2-4 hours to obtain mixed slurry. (3) Spray dry the mixed slurry obtained in step (2) to obtain spherical precursor particles; (4) Heat-treat the spherical precursor particles obtained in step (3) at 450-600℃ for 1-2 hours to obtain Mg-V-Si in-situ reactive composite dopant.

3. The low-loss, wide-temperature manganese-zinc ferrite material according to claim 2, characterized in that, The dispersant in step (1) is one or more of polyethylene glycol 2000, silane coupling agent KH570, and sodium polyacrylate, and the amount added is 1.5-3.0% of the mass of nano-SiO2.

4. The low-loss, wide-temperature manganese-zinc ferrite material according to claim 3, characterized in that, The magnesium salt in step (2) is magnesium nitrate or magnesium acetate; the complexing agent is ethylenediaminetetraacetic acid, and the amount of ethylenediaminetetraacetic acid added is 8% to 12% of the mass of ammonium metavanadate.

5. The low-loss, wide-temperature manganese-zinc ferrite material according to claim 1, characterized in that, The surfactant is one or more of Tween 80, Tween 60, or dodecyl dimethyl benzyl ammonium chloride; the molding aid is polyvinyl alcohol.

6. A method for preparing the low-loss, wide-temperature manganese-zinc ferrite material according to any one of claims 1-5, characterized in that, The preparation steps include the following: (1) Pre-sintering: Fe2O3, Mn3O4 and ZnO are mixed evenly according to the weight parts and then ground, and pre-sintered at 750-850℃ for 1.5-2.5 hours to obtain the main pre-sintered material; (2) Preparation of Mg-V-Si in-situ reactive composite dopant; (3) Secondary ball milling: The pre-calcined material obtained in step (1), the composite dopant obtained in step (2), and CaCO3, Nb2O5, surfactant, and molding aid are added to a ball mill. 5-8% of the total weight of the mixture is added to perform wet ball milling at a speed of 150-250 r / min for 3-6 hours to obtain a slurry. (4) Molding: The slurry obtained in step (3) is dried, granulated, and pressed into shape to obtain a green body; (5) Gradient sintering: The green blank obtained in step (4) is subjected to gradient sintering, which includes a three-stage gradient heating stage and a dual-platform gradient cooling stage. (6) After cooling, a wide-temperature, low-loss manganese-zinc ferrite material is obtained.

7. The method for preparing the low-loss, wide-temperature manganese-zinc ferrite material according to claim 6, characterized in that, The three-stage heating process specifically includes: First heating gradient: heating from room temperature to 650℃ at a heating rate of 2-3℃ / min, holding at 650℃ for 1-2 hours, with air as the heating atmosphere; Second heating gradient: heating from 650℃ to 950℃ at a heating rate of 1-2℃ / min, holding at 950℃ for 1.5-2.5 hours, with the oxygen content in the heating atmosphere controlled at 5-8%; Third heating gradient: heating from 950℃ to 1200-1250℃ at a heating rate of 0.5-1℃ / min, holding at 1200-1250℃ for 2-3 hours, with the oxygen content in the heating atmosphere controlled at 2-4%.

8. The method for preparing the low-loss, wide-temperature manganese-zinc ferrite material according to claim 6, characterized in that, The dual-platform gradient cooling stage specifically includes: a first cooling platform: cooling from the sintering temperature to 1050℃ at a cooling rate of 3-5℃ / min, holding at 1050℃ for 2-3 hours, with the oxygen content in the cooling atmosphere controlled at 3-5%; a second cooling platform: cooling from 1050℃ to 850℃ at a cooling rate of 1-2℃ / min, holding at 850℃ for 1-2 hours, with the oxygen content in the cooling atmosphere controlled at 0.5-1%; and a final cooling: natural cooling from 850℃ to room temperature, with the cooling atmosphere being pure nitrogen.

9. The method for preparing the low-loss, wide-temperature manganese-zinc ferrite material according to claim 6, characterized in that, The grinding in step (1) refers to grinding the mixed material to a particle size D50 of 1.0-2.0 μm; the particle size D50 of the slurry after wet ball milling in step (3) is 0.8-1.5 μm.

Images