117 results about "Ferrite powder" patented technology

The invention belongs to the field of ferrite materials, and particularly relates to a high-coercivity strontium ferrite with iron partially replaced by aluminum and a preparation method of the high-coercivity strontium ferrite. Aiming at the problem of low coercive force of a ferrite pre-sintering material in the prior art, iron is partially replaced by aluminum, ferric nitrate, strontium nitrate, aluminum nitrate and glucose are used as reaction raw materials, the ratio of the total molar weight of Fe and Al to the molar weight of Sr is (9.5-12): 1, the ratio of the molar weight of Al to the total molar weight of Fe and Al is (0-0.41): 1, and the molar weight of glucose is 0.5-3.5 times of the total molar weight of Fe, Al and Sr; and calcining at 900-1200 DEG C for 1-3 hours by adopting a solution self-combustion-aluminum ion substitution method to prepare the strontium permanent magnetic ferrite powder material with high coercivity.

A ferrite powder comprising, as a main component compound, a magnetoplumbite-type hexagonal ferrite having a composition represented by the formula Sr(FexAlyZrz)12O19+δ (where x, y, z, and δ satisfy 0.400≤x<1.000, 0.030≤y≤0.350, 0.001≤z≤0.040, 0.750≤x+y+z<1.000, and -5.00≤δ≤-0.200), and having a volume resistance of 1.0×109 Ω·cm or less. A ferrite resin composite material, ferrite resin composite, and electromagnetic wave absorber containing said ferrite powder.

The invention belongs to the technical field of radio frequency microwave functional components, and particularly relates to a pouring type integrated transformer, an internal matching component and a preparation method thereof, the pouring type integrated transformer comprises a microstrip impedance line of a multilayer spiral structure, a soft magnetic ferrite pouring body located outside the microstrip impedance line, and leading-out terminals arranged at the two ends of the microstrip impedance line; the micro-strip impedance line is arranged on a substrate with a certain dielectric constant requirement and forms a spiral structure along a set path, the micro-strip impedance line and the substrate of the micro-strip impedance line are coated with the soft magnetic ferrite pouring body, the soft magnetic ferrite pouring body is of an integrally formed structure, and the soft magnetic ferrite pouring body is obtained by mixing soft magnetic ferrite powder and a binder, pouring the mixture in a mold and carrying out curing demolding. Through the innovative structural design and preparation process, the technical bottlenecks of large size, low efficiency, inconsistency, difficulty in packaging and the like existing in a traditional manual winding matching mode are overcome, and a feasible technical scheme is provided for miniaturization, high performance and large-scale application of a power amplifier matching network in a radio frequency microwave system.

This invention relates to the technical fields of RFID equipment manufacturing and novel magnetic inks, providing a magnetic ink for RFID electronic tags and its preparation method. The magnetic ink comprises bisphenol A epoxy acrylate prepolymer, modified polyester resin, polyamide-imide resin, nano-scale soft magnetic ferrite powder, silver-coated flake copper powder, low-polymerization-degree polyurethane compatibilizer, γ-glycidyl etheroxypropyltriethoxysilane coupling agent, photoinitiator, antioxidant, leveling agent, and reactive diluent monomer. The ferrite powder has a D50 of 0.1-0.3µm and its surface is treated with a phosphate ester-silane double coating. After UV curing, its magnetic permeability is 20-60, and its loss tangent is ≤0.05. This invention's ink possesses excellent magnetic properties, conductivity, and flexibility, effectively improving the tag's electromagnetic response, crack resistance, and printing accuracy. It is suitable for printing high-Q value narrow-linewidth antenna patterns.

The application belongs to the technical field of magnetic material preparation, and particularly relates to a production process of high-performance rare earth permanent ferrite magnetic powder. The process comprises the following steps: preparing iron red and auxiliary materials, wherein the auxiliary materials comprise calcium carbonate, strontium carbonate, lanthanum oxide and cobalt oxide; mixing raw materials in proportion, then performing dry ball milling to obtain mixed materials; performing steam treatment on the obtained mixed materials to make the water content of the mixed materials reach 2-5%, then performing ripening, and the ripening time is at least 30 min, and the ripening process is completed in the screw conveyor; balling; pre-sintering; performing coarse crushing on the pre-sintered materials and sieving to obtain rare earth permanent ferrite magnetic powder. Through steam pretreatment and ripening, the strength and thermal stability of the ball materials are significantly improved, the ball materials remain complete in the kiln, the flowability is good, and the consistency and qualified rate of the product are improved.

The discharge valve comprises a material receiving frame applied to the permanent magnetic ferrite crushing ball mill, a through hole penetrating through and extending to the left side of the material receiving frame is formed in the bottom of the material receiving frame, and mounting plates are welded to the inner walls of the two sides of the through hole. A discharging valve body is installed in a through hole which is formed in the bottom of the material receiving frame and penetrates through the left side of the material receiving frame, installation grooves are formed in the middle of the front portion and the middle of the rear portion of the discharging valve body, a panel is welded to the left side of the discharging valve body, and the discharging valve body is a hollow cuboid. And filtering through holes are formed in the right side, the upper part, the lower part, the front part and the rear part of the discharge valve body. According to the discharge valve of the permanent magnetic ferrite crushing ball mill, the receiving frame, the stop lever, the discharge valve body and the like are arranged, so that permanent magnetic ferrite powder can be quickly filtered by the discharge valve body, the permanent magnetic ferrite powder is automatically separated from a grinding ball, the labor is saved, and the cost is reduced.

The present invention generally relates to a method for synthesizing dysprosium-doped copper-zinc ferrite nanomaterials with enhanced structural and functional properties. The method comprises dissolving stoichiometric quantities of copper nitrate trihydrate, zinc nitrate hexahydrate, iron nitrate nonahydrate, and dysprosium nitrate hexahydrate in distilled water to prepare an oxidizer solution. A fuel mixture is separately prepared using urea and glucose in equal proportions by weight. The oxidizer and fuel mixtures are combined in 1:1 ratio, calculated based on their respective oxidizing and reducing valencies, to form a homogeneous precursor solution. This solution is stirred thoroughly for about one hour and subsequently transferred to a Pyrex dish. The dish is placed in a muffle furnace preheated to approximately 450° C., where the solution undergoes a self-sustained combustion reaction, yielding a fine, porous Cu0.5Zn0.5DyxFe2-xO4 ferrite powder within 20 minutes. The resultant powder is ground to achieve uniform particle distribution suitable for advanced applications.

The invention discloses a preparation method and application of ferrite-based micron-sized flaky microwave absorbent powder, and relates to the technical field of microwave absorbing materials.The preparation method comprises the following steps that S1, ferrite precursor tape casting slurry A is pretreated, and slurry B is obtained; s2, the slurry B is poured into a casting machine for casting, and a casting green tape C is obtained at an outlet of the casting machine; s3, stripping and removing the PET substrate on the tape casting green tape C to obtain a ferrite green tape sheet D; s4, sintering the ferrite green tape sheet D in sintering equipment, and cooling to room temperature to obtain a ferrite sheet E; and step S5, crushing the ferrite sheet E, and performing classified screening treatment to obtain the flaky ferrite absorbent powder. According to the invention, the design is reasonable, the flaky ferrite powder is used as the magnetic absorbent, compared with the traditional flaky carbonyl iron, the ferrite material has obvious lightweight and anticorrosion advantages, the labyrinth effect formed by the flaky structure can further improve the anticorrosion performance of the product, and impedance mismatching caused by eddy current loss is avoided.

The present invention developed a composite having a novel structure containing, in a high content, a powder having a radiation-shielding function.　Provided is a composite having a radiation-shielding function and a method for producing the same. The composite comprises a preform made from a mixture containing a liquid silica-based binder and one or more radiation-shielding powders selected from gadolinium oxide, boron carbide, boron oxide, boron, barium sulfate, strontium oxide, tungsten, tungsten oxide, tungsten carbide, molybdenum, molybdenum oxide, iron powder, iron oxide powder, and ferrite powder, the radiation-shielding powder(s) being contained in the range from 3% to 85% in total. All of the voids in the preform are impregnated and filled with molten aluminum and solidification is allowed to occur to form a composite, or 25% or more of the voids in the preform are impregnated with a liquid organic / inorganic sealing agent and solidification is allowed to occur to form a composite. The liquid silica-based binder has properties that allow the preform to be formed at a temperature at which the radiation-shielding powder(s) does not decompose.

A multi-pump servo motor driving module for a ferrite powder press comprises a main driver, a first slave driver and a second slave driver, a power supply port of the main driver is connected with a main servo motor, power supply ports of the first slave driver and the second slave driver are respectively connected with a first slave servo motor and a second slave servo motor, and the first slave driver and the second slave driver are respectively connected with the main driver and the second slave driver. The ferrite powder pressing machine has the beneficial effects that firstly, the ferrite powder pressing machine realizes multi-pump linkage operation, part of procedures can be overlapped and carried out at the same time, the waiting time between the forming procedures is reduced, and the forming period is greatly shortened; secondly, the servo motor pump is used for closed-loop control, oil can be reasonably supplied to different hydraulic pumps according to the requirements of all working procedures, and different moments, angles and speeds needed by different working procedures are matched;

The invention provides a high-stability magnetic core material and a preparation method thereof, and belongs to the technical field of ferrite materials.The preparation method comprises the following steps that raw materials are subjected to primary ball milling and then mixed, and mixed powder is obtained; pressing the mixed powder into a material block, and presintering to obtain MnZn ferrite; the preparation method comprises the following steps: grinding MnZn ferrite to obtain MnZn ferrite powder, and loading nano SiO2 and nano MgO on the surface of the MnZn ferrite powder to obtain coated MnZn ferrite powder; mixing the MnZn coated ferrite powder with Bi2O3, Ta2O5 and SnO2, and carrying out secondary ball milling, so as to obtain doped ferrite powder; mixing and granulating the doped ferrite powder and an adhesive, and pressing into a green body; and sintering the green body to obtain the MnZn ferrite magnetic core material. Volume mutation of the magnetic core material under thermal shock can be counteracted, and the magnetic core material is prevented from cracking after being subjected to thermal shock.

The invention discloses a snow melting process based on electromagnetic induction heating of a turnout, which comprises electromagnetic induction coils attached to the waist of a turnout steel rail and the side face of a turnout sliding plate, and electronic paste containing graphene, silver, copper, nickel and ruthenium series resistance paste and a dopant prepared by compounding spinel cordierite and ferrite is burnt and injected to the outer sides of the coils. Alternating current is applied to the coil to generate a magnetic field, the inner side magnetic flux enables the steel rail to generate eddy current heating, the outer side magnetic flux enables slurry carriers to migrate to generate Joule heat, and a synergistic heating infrared radiation system is formed. The method has the beneficial effects that ice and snow on the surface of a turnout steel rail, a rail gap and a sliding plate area are synchronously melted, the technology utilizes the infrared radiation characteristics of graphene, spinel cordierite and ferrite powder, original vacant magnetic flux is utilized, the magnetic flux utilization rate is increased, power consumption is reduced, and the snow melting efficiency and reliability are improved.

The invention relates to a preparation method of a YIG-M type barium ferrite mixed material for a microstrip line circulator. The preparation method comprises the following steps: firstly, preparing YIG precursor powder and barium ferrite powder; pressing the YIG precursor powder into a green body, and sintering to obtain phase-formed YIG ferrite; and crushing the YIG ferrite, mixing the crushed YIG ferrite with the barium ferrite precursor powder according to a mass ratio of 1: 2-2: 1, pressing the mixture into a green body, and carrying out sintering phase formation to obtain the YIG-M type barium ferrite mixed material. The external bias magnetic field of the prepared mixed material is far smaller than that of a traditional YIG material, a good circulation effect can be achieved only through a smaller permanent magnet, and a circulator can be further miniaturized and integrated.

The invention relates to the technical field of transformer manufacturing, in particular to a laminated transformer preparation method and a laminated transformer. The preparation method of the laminated transformer comprises the following steps: respectively preparing ferrite powder and microcrystalline glass ceramic powder into a first green tape and a second green tape by adopting a tape casting process; forming through holes in the first green tape and the second green tape, and filling the through holes with conductive paste; a primary coil layer and a secondary coil layer are printed on the first hole filling green ceramic tape; laminating a plurality of coil hole-filling green ceramic tapes and a plurality of second hole-filling green ceramic tapes according to a preset sequence to form an intermediate electrode layer; laminating a plurality of first green tapes to form a cover layer; stacking the two cap layers and the intermediate electrode layer together to form a block; and sintering the laminated monomers to obtain the laminated transformer. The problems of interface stress concentration and structure cracking caused by difference of thermal expansion coefficients of different materials are effectively solved, and the product yield and reliability are remarkably improved.

Provided is a radio wave absorbing sheet with little variation in radio wave absorption amount associated with temperature changes. A first radio wave absorbing sheet comprises a base material made of an organic substance and a powder supported within the base material. The powder is composed of MnZn ferrite powder, aluminum powder, and silicon carbide powder. When the volume ratio of the MnZn ferrite powder is VM, the volume ratio of the aluminum powder is VA, and the volume ratio of the silicon carbide powder is VS with respect to the entire radio wave absorbing sheet, the silicon carbide occupancy ratio RS1 represented by VS / (VM + VA + VS) is 1.5-41% inclusive.

Provided are: a ferrite powder whereby, when the ferrite powder is applied in a composite material, dropping out of ferrite particles is suppressed without moldability and filling ability being compromised; a ferrite resin composite material; and an electromagnetic shielding material, an electronic material, or an electronic component. This ferrite powder includes at least spherical or polyhedral ferrite particles in which a step structure is provided on surfaces thereof, the step structure having a polyhedral outline in the surfaces of the ferrite particles.

The present invention belongs to the field of wireless charging technology, and specifically relates to a high-frequency low-loss three-dimensional shielding material and a preparation method thereof. The preparation method comprises the following steps: (1) preparing a material composed of Fe bal. M a Cu b M' c Si d B e X f (1) crushing or pulverizing the iron-based nanocrystalline and / or amorphous material, and then subjecting it to annealing and crystallization treatment to obtain nanocrystalline soft magnetic alloy powder; (2) mixing the obtained nanocrystalline soft magnetic alloy powder with ferrite powder and a binder, and then subjecting the mixture to compression molding or injection molding to obtain a high-frequency, low-loss three-dimensional shielding material. The composite shielding material obtained by the present invention can simultaneously possess the high saturation magnetic flux density of nanocrystalline and the low-loss characteristics of ferrite, and can be processed into a three-dimensional shape, thereby reducing leakage magnetic flux in the XY direction and improving the power conversion efficiency.

The application discloses a preparation method of a magnetic high-entropy alloy composite material, and belongs to the technical field of magnetic material preparation. The saturation magnetization intensity of the magnetic high-entropy alloy composite material can reach 153-172 emu / g, the hardness value can reach 200-233 HV, the tensile strength can reach 600-712 MPa, and the coercive force is less than 200 Oe. The preparation steps comprise the following steps: (1) high-entropy alloy powder preparation; (2) ferrite powder preparation; (3) mixing the powders obtained in the steps (1) and (2) with proper additives; (4) loading into a mold and pressure forming; (5) sintering, and the magnetic high-entropy alloy composite material is obtained. The high-entropy alloy magnetic composite material obtained by reasonably controlling the high-entropy alloy composition, the ferrite composition, the proportion of the two components and the sintering process has excellent mechanical properties and outstanding high-frequency magnetic properties.

The invention relates to a method for preparing nano barium ferrite powder, in particular to a method for preparing nano barium ferrite through cooperation of laser annealing and neodymium doping. The method comprises the following steps: S1, preparing a ferrite amorphous strip from raw materials including Fe2O3, BaO, Nd2O3 and B2O3 by utilizing a smelting melt-spinning method; s2, irradiating the ferrite amorphous strip in the step S1 by using laser, and carrying out laser annealing; and S3, carrying out pickling crushing and filtering washing treatment on the annealed strip, and drying to obtain the neodymium-doped nano barium ferrite. According to the preparation method disclosed by the invention, through the synergistic effect of laser annealing and strong absorption of neodymium ions, overgrowth of crystal grains is effectively inhibited, and the particle size distribution of the nano ferrite is narrowed, so that the problems of wide particle size distribution of powder, low production efficiency and the like in the existing preparation technology are solved.

To develop a composite of a new constitution containing a powder having a radiation shielding function in a high content.SOLUTION: Molten aluminum is impregnated and filled into all voids of a preform made of a mixture containing one or more kinds of radiation shielding powders selected from gadolinium oxide, boron carbide, boron oxide, boron, barium sulfate, strontium oxide, tungsten, tungsten oxide, tungsten carbide, molybdenum, molybdenum oxide, iron powder, iron oxide powder, and ferrite powder and a liquid silica-based binder, the mixture containing the radiation shielding powders in a range of 3 to 85% in total; In the composite body having the radiation shielding function and the method for manufacturing the same, a liquid organic-inorganic sealing agent is impregnated and solidified to form the composite body, and a liquid silica-based binder has characteristics capable of forming a preform at a temperature at which the radiation shielding powder is not decomposed.SELECTED DRAWING: None

The present invention provides a ferrite powder which contains 0.9% by mass to 2.5% by mass of lithium (Li), 1.0% by mass to 8.0% by mass of manganese (Mn), and 58.0% by mass to 69.5% by mass of iron (Fe), and has a crystal phase belonging to the space group P4132 and a crystal phase belonging to the space group Fd-3m. In the X-ray diffraction profile, the half width of the (311) plane of the crystal phase belonging to the space group Fd-3m is 0.09° to 0.22°, and the volume average particle diameter D50 is not less than 1 μm but less than 20 μm.

The application provides an amorphous magnetic powder core and a preparation method thereof, and the preparation method comprises the following steps: (1) brittle heat treatment is performed on a Fe-based amorphous alloy, the amorphous alloy is broken and then pre-annealing treatment is performed to obtain amorphous powder, and two portions of the amorphous powder are taken and sieved through different sieves to obtain first powder and second powder; (2) the first powder and the second powder are mixed, and then MgO is used to perform magnetron sputtering treatment on the first powder and the second powder to obtain precursor powder; (3) surface modification treatment is performed on nano ferrite powder, the precursor powder and the surface-modified nano ferrite powder are mixed and ground, a binder is added for granulation, and then annealing treatment is performed after compression treatment to obtain the amorphous magnetic powder core. The amorphous powder / MgO / ferrite double-layer core-shell structure amorphous composite material is prepared by using the magnetron sputtering method and the mechanical ball milling method, and the prepared magnetic powder core has high permeability, low power loss and good direct current superposition performance.

The present invention belongs to the technical field of soft magnetic materials and discloses a high-frequency, low-loss magnetic powder core and a preparation method thereof. The method comprises the following preparation steps: (1) subjecting an iron alloy soft magnetic powder having a particle size of 5 to 50 μm to an insulation coating treatment to obtain an insulation-coated iron alloy soft magnetic powder; (2) uniformly mixing the insulation-coated iron alloy soft magnetic powder obtained in step (1) with a ferrite powder having a particle size of less than 5 μm and a binder, and then injecting the mixture into a mold for compression molding, and then heating the mixture to 600 to 900°C for annealing to obtain a high-frequency, low-loss magnetic powder core. The magnetic powder core of the present invention is prepared by mixing and compounding large-particle iron alloy soft magnetic powder and small-particle ferrite powder, which can significantly improve the insulation performance of the magnetic powder core to reduce its high-frequency loss, and increase its molding density to reduce the adverse effect on the inductance value.

The invention discloses a preparation method of a composite wave-absorbing film and the composite wave-absorbing film. The method comprises the following steps: mixing a strontium source, an iron source and fused salt, and grinding to obtain a first mixture; the first mixture is subjected to high-temperature sintering and then crushed, and first powder is obtained; and washing and drying the first powder, and grinding to obtain the strontium ferrite powder. Mixing the first aramid nanofiber aqueous dispersion with the strontium ferrite aqueous dispersion to obtain a first mixed dispersion; and carrying out vacuum filtration on the first mixed dispersion liquid to obtain the first composite film. Mixing the second aramid nanofiber aqueous dispersion liquid with the Ti3C2Tx aqueous dispersion liquid to obtain a second mixed dispersion liquid; and carrying out vacuum filtration treatment on the second mixed dispersion liquid to obtain a second composite film. The first composite film and the second composite film are stacked and then subjected to hot pressing treatment, and the composite wave-absorbing film is obtained. Strontium ferrite and Ti < 3 > C < 2 > T < x > in the composite wave-absorbing film have a synergistic effect, so that the wave-absorbing frequency band is widened, and the wave-absorbing performance of the composite wave-absorbing film is improved.

The present invention provides a magnetic filling slurry and its preparation method and application. The raw materials of the magnetic filling slurry include, by weight, 95-99 parts of soft magnetic alloy powder, 1-5 parts of ferrite powder, 10-20 parts of binding liquid, 3-6 parts of a first composite solvent, 0.3-0.6 parts of a dispersant, and 0.3-0.6 parts of a first plasticizer; the binding liquid includes a binding agent, a second composite solvent, and a second plasticizer in a mass ratio of (3-4):(4-5):(3-1). The magnetic filling slurry provided by the present invention, by introducing ferrite powder as an insulating coating agent, makes the soft magnetic alloy powder have a higher magnetic permeability; by regulating the ratio of each component in the binding liquid and the composite solvent system, the magnetic filling slurry has good printability and thixotropy, and can meet the performance requirements as a screen printing filling slurry.

The invention provides a method for preparing a high-frequency ultralow-loss soft magnetic composite material, and the method comprises the following steps: (1) iron alloy soft magnetic powder and ferrite powder are provided, the D50 particle size range of the iron alloy soft magnetic powder is 1-100 [mu] m, the average particle size of the ferrite powder is 1-100 nm, and the average particle size of the ferrite powder is 1-100 nm; the ferrite powder is prepared by a coprecipitation method; the mass ratio of the ferrite powder to the iron alloy soft magnetic powder is (0.05: 100)-(10: 100); (2) mixing and grinding the iron alloy soft magnetic powder and the ferrite powder in the step (1) for a period of time to obtain composite powder; (3) adding an adhesive into the composite powder in the step (2), uniformly mixing and granulating to obtain granulated composite powder; and (4) adding a lubricant into the granulated composite powder in the step (3), and mixing to prepare the high-frequency ultralow-loss soft magnetic composite material. According to the high-frequency ultra-low-loss soft magnetic composite material prepared by the invention, the hysteresis loss and the eddy-current loss of the composite material can be remarkably reduced.

The application relates to the technical field of permanent ferrite preparation, in particular to a method for preparing strontium ferrite by a multi-field coupling auxiliary molten salt method. First, a chemical coprecipitation method is improved to obtain a mixture containing an excess precipitant, inorganic salt and strontium ferrite precursor; then the mixture is subjected to heat treatment under multi-field coupling; finally, strontium ferrite powder is obtained after washing and drying. The application simplifies the chemical coprecipitation process, avoids Sr loss and realizes in-situ salt formation; a multi-element molten salt system is constructed during heat treatment, and an alkali-containing molten salt system with activation is proposed; in the molten salt liquid phase environment, multi-physical fields such as magnetic fields and ultrasonic vibration force fields are cooperated to control the orientation and growth of grains, new driving force and fast channels are provided for ion diffusion, and the rapid synthesis of strontium ferrite and the control of microstructure and size are realized in a low temperature and short time.

The invention discloses an intelligent heat treatment forming die for a manganese zinc ferrite magnetic core, and relates to the technical field of forming dies, the intelligent heat treatment forming die for the manganese zinc ferrite magnetic core comprises a forging press, a water tank is fixedly installed on the surface of the forging press, and a water pump fixedly penetrates through the top of the water tank; according to the intelligent heat treatment forming mold for the manganese zinc ferrite cores, the output end of the motor rotates to drive a rotating shaft to rotate, and meanwhile, the rotating shaft rotates to drive a stirring plate to rotate; at the moment, the stirring plate rotates to stir the manganese-zinc-iron oxide powder accumulated in the feeding cylinder, so that the uniformity of the powder is improved, non-uniform distribution of some components in a final product is avoided, the consistency and performance stability of magnetic cores are ensured, the fluidity of raw materials is improved, and the raw materials enter a mold more easily; therefore, the required magnetic core shape can be better formed in the heat treatment forming process.

The invention discloses samarium ferrite powder and a preparation method thereof, and the preparation method comprises the following steps: 1) mixing and stirring a samarium salt aqueous solution, a water-soluble iron salt and citric acid for 1-3 hours to obtain an initial reactant; (2) carrying out hydrothermal reaction on the initial reactant at 180-200 DEG C for 6-15 hours to obtain an intermediate reactant; 3) carrying out solid-liquid separation on the intermediate reactant, washing the separated solid, and drying the washed solid to obtain a precursor; and 4) roasting the precursor in an inert atmosphere at 700-900 DEG C for 1-5 hours to obtain the samarium ferrite powder. According to the preparation method, the samarium ferrite powder with good sphericity and the particle size of 2-3 microns can be obtained.

The present application provides an electromagnetic wave absorbing sheet having a small variation in the amount of electromagnetic wave absorption caused by temperature change. A first electromagnetic wave absorbing sheet includes a substrate composed of an organic substance and a powder supported in the substrate, the powder being composed of a MnZn ferrite powder, an aluminum powder, and a silicon carbide powder, when a volume ratio of the MnZn ferrite powder is set to V M , a volume ratio of the aluminum powder is set to V A , and a volume ratio of the silicon carbide powder is set to V S , a silicon carbide occupancy ratio R S represented by V M / (V A + V S + V S1 ) is 1.5% or more and 41% or less.