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  • C04B35/26—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on ferrites
  • C04B35/2608—Compositions containing one or more ferrites of the group comprising manganese, zinc, nickel, copper or cobalt and one or more ferrites of the group comprising rare earth metals, alkali metals, alkaline earth metals or lead
  • C04B35/2633—Compositions containing one or more ferrites of the group comprising manganese, zinc, nickel, copper or cobalt and one or more ferrites of the group comprising rare earth metals, alkali metals, alkaline earth metals or lead containing barium, strontium or calcium
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  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/34—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites
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  • C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
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  • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
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Definitions

• the present disclosure relates to MnZn-based ferrites that are particularly suitable for the magnetic cores of automobile-mounted parts.
• MnZn-based ferrite is a material widely used as a magnetic core for noise filters such as switching power supplies, transformers, and antennas.
• the soft magnetic materials it has high magnetic permeability and low loss in the kHz region, and is cheaper than amorphous metals and the like.
• MnZn-based ferrite used for the magnetic core of electronic components for automobile mounting applications whose needs are expanding due to the recent hybridization and electrification of automobiles, is required to have a high fracture toughness value.
• MnZn-based ferrite is a ceramic and is easily damaged because it is a brittle material.
• it is constantly vibrated and easily damaged in automobile mounting applications. This is because it will continue to be used.
• weight reduction and space saving are also required for automobile applications, it is important to have suitable magnetic properties as well as conventional applications in addition to high fracture toughness value.
• Patent Documents 1 and 2 can be mentioned as long as they mention good magnetic characteristics. Further, as MnZn-based ferrite having an increased fracture toughness value, for example, Patent Documents 3 and 4 have been reported.
• Patent Document 1 and Patent Document 2 although the composition for realizing the desired magnetic properties is mentioned, the fracture toughness value is not mentioned at all, and it is used as a magnetic core of an electronic component for an automobile. Is unsuitable.
• Patent Documents 3 and 4 refer to the improvement of the fracture toughness value, the magnetic properties are insufficient as the magnetic core of an electronic component for an automobile vehicle, which is also unsuitable for this application.
• This disclosure was made in view of such circumstances, and was manufactured under the same conditions as the excellent mechanical properties of a fracture toughness value of 1.10 MPa ⁇ m 1/2 or more measured in accordance with JIS R1607 of a flat plate core. It is an object of the present invention to provide an MnZn-based ferrite having a good magnetic property that a loss value of a toroidal-shaped core at 100 ° C., 300 kHz, and 100 mT is 450 kW / m 3 or less.
• the present inventors have obtained the following findings as a result of repeated diligent studies in order to achieve the above-mentioned problems.
• the inventors first found the optimum composition of Fe 2 O 3 amount and Zn O amount of MnZn-based ferrite capable of reducing the loss value at 100 ° C. and 300 kHz. Within this composition range, the magnetic anisotropy and magnetostriction are small, the resistivity is maintained, and the secondary peak showing the minimum value of the temperature characteristic of the loss can appear in the vicinity of 100 ° C. Low loss can be achieved below.
• uniform grain boundaries can be generated by adding appropriate amounts of SiO 2 , CaO, and Nb 2 O 5 , which are non-magnetic components that segregate at the grain boundaries, and the loss value can be further reduced by increasing the specific resistance. I found that.
• abnormal grain growth is a phenomenon in which the balance of grain growth during firing is lost due to the presence of impurities or the like, and coarse particles having a size of about 100 normal particles appear in some parts.
• the abnormal grain growth site has extremely low strength, and the core breaks from this site. Therefore, suppressing abnormal grain growth is indispensable for improving the fracture toughness value.
• the present invention has been made based on the above findings. That is, the gist structure of the present invention is as follows.
• MnZn-based ferrite composed of basic components, sub-components and unavoidable impurities. Assuming that the total of iron, zinc, and manganese in terms of Fe 2 O 3 , ZnO, and MnO is 100 mol%, the above basic components are Iron: 51.5-55.5 mol% in terms of Fe 2 O 3 Zinc: 5.0 to 15.5 mol% in terms of ZnO and manganese: the balance.
• the sub-component SiO 2 50-300 mass ppm, CaO: 100 to 1300 mass ppm and Nb 2 O 5 : 100 to 400 mass ppm
• P, B, Na, Mg, Al and K in the unavoidable impurities respectively.
• MnZn-based ferrite that suppresses Al less than 250 mass ppm
• K less than 100 mass ppm.
• the fracture toughness value measured in accordance with JIS R1607 is 1.10 MPa ⁇ m 1/2 or more, and the loss value at 100 ° C., 300 kHz and 100 mT is 450 kW / m 3 or less.
• the MnZn-based ferrite according to [2] is 1.10 MPa ⁇ m 1/2 or more, and the loss value at 100 ° C., 300 kHz and 100 mT is 450 kW / m 3 or less.
• the MnZn-based ferrite according to [2].
• the fracture toughness value measured according to JIS R1607 of the flat plate core is 1.10 MPa ⁇ m 1/2 or more, which is an excellent mechanical property
• the toroidal shape core manufactured under the same conditions is 100 ° C.
• MnZn-based ferrite which has a good magnetic characteristic of a loss value of 450 kW / m 3 or less at 300 kHz and 100 mT, can be provided with a good yield by reducing the crack generation rate of the molded body to 3.5% or less.
• MnZn-based ferrite in order to reduce the loss value of MnZn-based ferrite, it is effective to reduce the magnetic anisotropy and magnetostriction. In order to realize these, it is necessary to select the blending amount of Fe 2 O 3 , ZnO and MnO, which are the main components of the MnZn-based ferrite, from a suitable range. Further, by applying sufficient heat in the firing step to appropriately grow the crystal grains in the ferrite, it is possible to facilitate the movement of the domain wall in the crystal grains in the magnetization step. In addition, by adding a component that segregates to the grain boundaries and generating grain boundaries of appropriate and uniform thickness, the resistivity is maintained and the eddy current loss is reduced, achieving low loss in the 100 to 500 kHz range. There is.
• the magnetic core of electronic components for automobiles is required to have a high fracture toughness value so that they will not be damaged even in an environment subject to constant vibration. If the MnZn-based ferrite, which is the magnetic core, is damaged, the inductance is greatly reduced, so that the electronic component cannot perform the desired function, and as a result, the entire automobile may become inoperable.
• MnZn-based ferrites used in electronic components for automobiles are required to have both low loss magnetic properties and high fracture toughness values. According to the present disclosure, it is possible to provide MnZn-based ferrite having both good magnetic properties and high fracture toughness value.
• the numerical range represented by using “-” means a range including the numerical values before and after "-" as the lower limit value and the upper limit value.
• the composition of MnZn-based ferrite is limited.
• the reason why the composition of MnZn-based ferrite (hereinafter, also simply referred to as ferrite) is limited to the above range will be described.
• the content of these Fe 2 O 3 , ZnO, and MnO is mol% with respect to the total amount of iron, zinc, and manganese in terms of Fe 2 O 3, ZnO, and MnO, which is 100 mol%, while subcomponents and unavoidable impurities.
• the content of is expressed in mass ppm with respect to the basic component.
• Fe 2 O 3 51.5 mol% to 55.5 mol%
• the content of Fe 2 O 3 should be at least 51.5 mol% or more, and the upper limit should be 55.5 mol%.
• the content of Fe 2 O 3 is 55.3 mol% or less.
• ZnO 5.0 mol% to 15.5 mol%
• the Curie temperature becomes excessively high, and the loss value at 100 ° C. increases. Therefore, it is decided to contain at least 5.0 mol% of ZnO.
• the upper limit of the ZnO content is set to 15.5 mol%.
• the ZnO content is preferably 5.5 mol% or more.
• MnO Remaining This disclosure relates to MnZn-based ferrite, and the rest of the composition of the main component is MnO. This is because it is not possible to realize a loss value of 450 kW / m 3 or less under exciting conditions of 100 ° C., 300 kHz, and 100 mT without MnO.
• the MnO content is preferably 29.0 mol% or more, more preferably 30.0 mol% or more, still more preferably 30.5 mol% or more.
• the MnO content is preferably 43.0 mol% or less, more preferably 42.0 mol% or less.
• SiO 2 50-300 mass ppm SiO 2 is known to contribute to the homogenization of the crystal structure of ferrite, and by adding an appropriate amount, abnormal grain growth is suppressed and specific resistance is also increased. With the addition of an appropriate amount of SiO 2 , the loss value under exciting conditions of 100 ° C., 300 kHz, and 100 mT can be reduced, and the fracture toughness value can also be increased. Therefore, it is assumed that SiO 2 is contained at least in an amount of 50 mass ppm or more. However , when the content of SiO 2 is excessive, on the contrary, abnormal particles having low strength locally appear, and the abnormal particles significantly reduce the fracture toughness value and at the same time significantly deteriorate the loss value.
• the content of 2 should be 300 mass ppm or less.
• the content of SiO 2 is preferably 55 mass ppm or more, more preferably 60 mass ppm or more.
• the content of SiO 2 is preferably 275 mass ppm or less, more preferably 250 mass ppm or less.
• CaO 100-1300 mass ppm
• CaO has a function of segregating into the grain boundaries of MnZn-based ferrite and suppressing the growth of crystal grains, and by adding an appropriate amount, the loss value under exciting conditions of 100 ° C., 300 kHz, and 100 mT is reduced as the specific resistance increases. Can be done.
• the function of suppressing crystal grain growth also has the function of suppressing the appearance of abnormal grain growth, the fracture toughness value can be increased by adding an appropriate amount of CaO. Therefore, it is assumed that CaO is contained at least 100 mass ppm or more. However, when the CaO content is excessive, on the contrary, abnormal grains appear, the fracture toughness value decreases, and the loss value also deteriorates.
• the CaO content is kept at 1300 mass ppm or less.
• the CaO content is preferably 120 mass ppm or more, more preferably 150 mass ppm or more.
• the CaO content is more preferably 200 mass ppm or more.
• the CaO content is preferably 1200 mass ppm or less, more preferably 1100 mass ppm or less.
• Nb 2 O 5 100-400 mass ppm It is known that Nb 2 O 5 segregates at the grain boundaries of MnZn-based ferrite, has the effect of slowly suppressing the grain growth, and relaxing the stress. Therefore, the loss value can be reduced by adding an appropriate amount, and the fracture toughness value is also increased by suppressing the growth of abnormal grains that locally become low in strength. Therefore, at least Nb 2 O 5 is contained at 100 mass ppm or more. I decided to. However , when the content of Nb 2 O 5 is excessive, abnormal grains appear on the contrary, which induces a significant decrease in fracture toughness value and deterioration of loss value. Therefore, the content of Nb 2 O 5 is 400 mass ppm or less. Put in.
• the content of Nb 2 O 5 is preferably 120 mass ppm or more, more preferably 130 mass ppm or more.
• the content of Nb 2 O 5 is preferably less than 380 mass ppm.
• the content of Nb 2 O 5 in order to appropriately disperse the added Nb during the production of ferrite, preferably prevent fluctuations in the temperature characteristics of the loss value, and preferably suppress the increase in the loss value at 100 ° C. Is more preferably 375 mass ppm or less, still more preferably 350 mass ppm or less.
• P and B are components inevitably contained in the raw material iron oxide. There is no problem if these contents are in a very small amount, but if they are contained in a certain amount or more, abnormal grain growth of ferrite is induced, and the fracture toughness value decreases because the abnormal grain growth site becomes the starting point of fracture. It also increases the loss value in terms of magnetic properties, which has a serious adverse effect. Therefore, the contents of both P and B need to be limited to less than 10 mass ppm.
• the content of P is preferably 8 mass ppm or less, more preferably 5 mass ppm or less.
• the content of B is preferably 8 mass ppm or less, more preferably 5 mass ppm or less.
• the lower limit of the contents of P and B is not particularly limited, and may be 0 mass ppm, respectively.
• Na less than 200 mass ppm
• Mg less than 200 mass ppm
• Al less than 250 mass ppm
• K less than 100 mass ppm Na, Mg, Al, K are low-purity iron oxide, manganese oxide, and zinc oxide that are raw materials for MnZn-based ferrite. It is contained in water and is present as a dissolved component in water such as tap water. Further, in the ferrite manufacturing process, components such as a dispersant containing these metal ions may be added. Further, those containing these components are mainly used as refractories of the furnace used for calcining and firing in the ferrite manufacturing process, and it is conceivable that these components may be mixed due to the furnace falling off or contact wear.
• these components may react with iron oxide during firing to form a spinel structure and dissolve in MnZn-based ferrite.
• These components themselves do not induce abnormal grain growth and do not adversely affect the magnetic properties, but the solid solution of these components has lower toughness than ordinary MnZn-based ferrites. Therefore, the presence of these components causes MnZn.
• the toughness of the system ferrite may be significantly reduced. Therefore, in order to suppress the decrease in toughness, the content of these four components is limited.
• Na less than 200 mass ppm
• Mg less than 200 mass ppm
• Al less than 250 mass ppm
• K less than 100 mass ppm.
• the Na content is preferably 130 mass ppm or less, more preferably 90 mass ppm or less.
• the Mg content is preferably 150 mass ppm or less, more preferably 125 mass ppm or less.
• the Al content is preferably 200 mass ppm or less, more preferably 180 mass ppm or less.
• the content of K is preferably 90 mass ppm or less, and more preferably 75 mass ppm or less.
• the lower limits of Na, Mg, Al, and K are not particularly limited and may be 0 ppm, respectively.
• the Na content is preferably 10 mass ppm or more.
• the Mg content is preferably 10 mass ppm or more.
• the Al content is preferably 15 mass ppm or more.
• the K content is preferably 5 mass ppm or more.
• the MnZn-based ferrite will be described in detail later, but is produced by molding a granulated powder containing a binder by a powder compression method and then firing it. In this molding process, the molded body may be cracked mainly when the mold is removed from the mold. If cracks occur at this point, the product will be defective and its value as a product will be lost.
• the Na, Mg, Al and K components have a composition within the above-mentioned specified range, the crack generation rate of the molded product can be suppressed. We are investigating the details of this mechanism, but the present inventors speculate as follows.
• the content of Ti as an unavoidable impurity is preferably less than 50 mass ppm.
• the lower limit of the Ti content is not particularly limited and may be 0 mass ppm. From the viewpoint of production technology, the Ti content is preferably 5 mass ppm or more.
• the total amount of P, B, Na, Mg, Al, and K is preferably 675 mass ppm or less, and more preferably 400 mass ppm or less. The smaller the total amount of these, the larger the fracture toughness value.
• MnZn-based ferrite various characteristics are greatly affected by various parameters, not limited to the composition. Among them, in the present disclosure, it is preferable to provide the following provisions in order to obtain more preferable magnetic characteristics and mechanical characteristics.
• Fracture toughness value measured in accordance with JIS R1607 1.10 MPa ⁇ m 1/2 or more MnZn-based ferrite is a ceramic and is a brittle material, so it hardly undergoes plastic deformation. Therefore, the fracture toughness is measured by the SEBP method (Single-Edge-Precracked-Beam method) specified in JIS R 1607. In the SEBP method, the fracture toughness value is measured by imprinting a Vickers indenter in the center of the flat plate core and performing a bending test with a pre-crack.
• SEBP method Single-Edge-Precracked-Beam method
• the MnZn-based ferrite of the present disclosure is intended for use in automobiles where high toughness is required, and has a fracture toughness value of 1.10 MPa ⁇ m 1/2 or more. In order to satisfy this condition, it is necessary to control the component composition within the specified range as described above. Preferably, the fracture toughness value is 1.12 MPa ⁇ m 1/2 or more.
• the MnZn-based ferrite of the present disclosure may further contain the following additives as subcomponents.
• CoO 3500 mass ppm or less
• CoO is a component containing Co 2+ ions having positive magnetic anisotropy, and the addition of this component can widen the temperature range of the secondary peak showing the minimum temperature of loss. Further, by setting the CoO content to 3500 mass ppm or less, the negative magnetic anisotropy of other components can be offset, and an increase in the loss value at 100 ° C. can be further prevented.
• the lower limit of CoO is not particularly limited and may be 0 mass ppm, but preferably more than 500 mass ppm. Further, preferably, the CoO content is 2500 mass ppm or less.
• NiO 15,000 mass ppm or less
• NiO is selectively incorporated into the B site of the spinel lattice, and has the effect of reducing the loss value as a result of increasing the Curie temperature of the material and increasing the saturation magnetic flux density. Further, by setting the NiO content to 15,000 mass ppm or less, it is possible to further prevent the increase in magnetostriction and further prevent the increase in the loss value at 100 ° C. Therefore, when added, the NiO content should be limited to 15,000 mass ppm or less. Preferably, the NiO content is 12000 mass ppm or less.
• the lower limit of NiO is not particularly limited and may be 0 mass ppm, but is preferably 1200 mass ppm or more, more preferably 1500 mass ppm or more, and further preferably 2000 mass ppm or more.
• the method for producing MnZn-based ferrite of the present disclosure is as follows.
• the molding process of molding the granulated powder to obtain a molded body can be a method for producing MnZn-based ferrite, which comprises a firing step of calcining the molded body to obtain MnZn-based ferrite.
• MnZn-based ferrite In the production of MnZn-based ferrite, first, Fe 2 O 3 , ZnO, and MnO powder, which are the basic components, are weighed so as to have the above-mentioned ratios, and these are sufficiently mixed to form a mixture, and then the mixture is tentatively prepared. Bake (temporary baking process). At this time, unavoidable impurities are limited to the above-mentioned range.
• the sub-ingredients specified in the present disclosure are added to the obtained calcined powder at a predetermined ratio, mixed with the calcined powder, and pulverized (mixing-crushing step).
• the powder is sufficiently homogenized so that the concentration of the added component is not biased, and at the same time, the calcined powder is refined to the target average particle size to obtain a pulverized powder.
• a known organic binder such as polyvinyl alcohol is added to the pulverized powder, and granulation is performed by a spray-drying method or the like to obtain granulated powder (granulation step). After that, if necessary, it is subjected to a step such as sieving for adjusting the particle size, and then pressure is applied by a molding machine to form a molded product (molding step). If the molded body is cracked in this molding step, the crack remains in the MnZn-based ferrite of the final product. MnZn-based ferrite containing cracks is inferior in strength and is synonymous with containing a gap, so that it is a defective product that cannot satisfy the desired magnetic characteristics. Therefore, the molded product containing cracks is removed at this point. Next, the molded product is fired under known firing conditions to obtain a MnZn-based ferrite (firing step).
• a known organic binder such as polyvinyl alcohol is added to the pulverized powder, and granulation is performed by
• a raw material having a reduced amount of impurities is used. Further, during mixing, pulverization, and granulation, pure water or ion-exchanged water having a reduced amount of impurities is used as a solvent for the slurry containing the basic component or the sub-component. Also, as the binder and the surfactant to be added to reduce the viscosity of the slurry, select one having reduced metal ions. Further, the refractories of the furnace used in the calcining process and the firing process often contain these components. For this reason, Na, Mg, Al and Na, Mg, Al and Na, Mg, Al and Na, Mg, Al and It prevents K contamination.
• the obtained MnZn-based ferrite may be appropriately subjected to surface polishing or other processing.
• the MnZn-based ferrite thus obtained is an excellent machine with a fracture toughness value of 1.10 MPa ⁇ m 1/2 or more measured in accordance with JIS R1607 of a flat plate core, which was not possible with conventional MnZn-based ferrite. Not only does it have the characteristics, but it also realizes the good magnetic characteristics of the toroidal-shaped core manufactured under the same conditions, with a loss value of 450 kW / m 3 or less at 100 ° C, 300 kHz, and 100 mT.
• the loss value of the toroidal-shaped core at 100 ° C., 300 kHz, and 100 mT is preferably 440 kW / m 3 or less.
• the loss value of the toroidal shape core is 100 ° C. using a core loss measuring instrument (manufactured by Iwadori Measurement Co., Ltd .: SY-8232) after winding the core for 5 turns on the primary side and 5 turns on the secondary side. A loss value of 300 kHz and 100 mT is measured.
• the sample that was dented in the center by the Vickers indenter was cracked and then broken in a three-point bending test, and the breaking load and the dimensions of the sample were obtained. Calculated based on and.
• Example 1 Fe contained, if all Zn and Mn were calculated as Fe 2 O 3, ZnO and MnO, Fe 2 O 3, ZnO, and MnO are each raw material powder were weighed so as to ratios shown in Table 1, a ball mill After mixing for 16 hours using Next, SiO 2 , CaO and Nb 2 O 5 were weighed equivalent to 150, 700 and 250 mass ppm, respectively, and then added to the calcined powder, and pulverized with a ball mill for 12 hours to obtain pulverized powder. Polyvinyl alcohol was added to the pulverized powder to perform spray-dry granulation, and a pressure of 118 MPa was applied to form a toroidal-shaped core and a flat plate-shaped core.
• the molded bodies are placed in a firing furnace and fired at a maximum temperature of 1320 ° C. for 2 hours in a gas stream in which nitrogen gas and air are appropriately mixed.
• a sintered toroidal-shaped core having an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm and a sintered flat plate-shaped core having a length of 4 mm, a width of 35 mm, and a thickness of 3 mm were obtained.
• the loss value at 100 ° C., 300 kHz, and 100 mT is 450 kW / m 3 or less and the fracture toughness value is 1.10 MPa ⁇ m 1/2. As described above, it has both suitable magnetic properties and high toughness.
• the value is high.
• the loss value has increased due to the increased magnetic anisotropy and magnetostriction, and the loss value at 100 ° C., 300 kHz, and 100 mT does not satisfy 450 kW / m 3 or less.
• Comparative Example (Comparative Example 1-3) in which ZnO was insufficient the Curie temperature rose excessively
• Comparative Example (Comparative Example 1-4) in which ZnO was contained in a larger amount than the claimed range the loss was minimized. Since the indicated secondary peak has decreased, the loss value at 100 ° C., 300 kHz, and 100 mT cannot satisfy 450 kW / m 3 or less.
• Example 2 Fe contained, if all Zn and Mn were calculated as Fe 2 O 3, ZnO and MnO, Fe 2 O 3: 53.0mol %, ZnO: 12.0mol%, MnO: a 35.0Mol% of the component composition
• the raw materials were weighed so as to be, mixed for 16 hours using a ball mill, calcined in air at 900 ° C. for 3 hours, and cooled to room temperature in air for 1.5 hours to obtain calcined powder. ..
• the amounts of SiO 2 , CaO, Nb 2 O 5 shown in Table 2 and CoO or NiO were added to some of the samples, and the mixture was pulverized with a ball mill for 12 hours to obtain pulverized powder.
• Polyvinyl alcohol was added to the pulverized powder to perform spray-dry granulation, and a pressure of 118 MPa was applied to form a toroidal-shaped core and a flat plate-shaped core. After that, after visually confirming that the molded product is not cracked, the molded product is inserted into a firing furnace and fired at a maximum temperature of 1320 ° C. for 2 hours in a gas stream in which nitrogen gas and air are appropriately mixed, and then fired outside.
• a sintered toroidal-shaped core having a diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm and a sintered flat plate-shaped core having a length of 4 mm, a width of 35 mm, and a thickness of 3 mm were obtained.
• the amounts of P and B contained in the obtained sintered toroidal-shaped core and the sintered flat plate-shaped core were 4 and 3 mass ppm, respectively, and Na, Mg, Al, and K were 80, 75, 120, and 30 mass ppm, respectively. Met.
• the loss value at 100 ° C., 300 kHz and 100 mT is 450 kW. It is / m 3 or less and the fracture toughness value is 1.10 MPa ⁇ m 1/2 or more, and both suitable magnetic properties and high toughness can be achieved.
• Comparative Examples 2-1, 2-3 and 2-5 which contained less than the specified amount of even one of the three components of SiO 2 , CaO and Nb 2 O 5, the grain boundary generation was insufficient, so the ratio was increased.
• the loss value is deteriorated due to the decrease in resistivity and the increase in eddy current loss, and some low-strength coarse grains appear due to insufficient suppression of crystal grain growth.
• the breaking toughness value is less than the desired value.
• Comparative Examples 2-2, 2-4 and 2-6 in which even one of the same components is excessive, the loss value is remarkably deteriorated due to the appearance of abnormal grains, and the abnormal grain generation site is locally located. Due to its low strength, the fracture toughness value is also greatly reduced.
• Example 3 By the method shown in Example 1, the ratio of the basic component and the sub-ingredients is the same as that of Example 1-2, but the amount of P and B contained is different.
• Got The granulated powder was formed into a toroidal-shaped core and a flat plate-shaped core by applying a pressure of 118 MPa. Then, after visually confirming that these molded bodies were not cracked, the molded bodies were inserted into a firing furnace and fired at a maximum temperature of 1320 ° C. for 2 hours in a gas stream in which nitrogen gas and air were appropriately mixed.
• a sintered toroidal-shaped core having an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm and a sintered flat plate-shaped core having a length of 4 mm, a width of 35 mm, and a thickness of 3 mm were obtained.
• the characteristics of each of these samples were evaluated using the same method and equipment as in Example 1. The obtained results are shown in Table 3.
• Example 3-1 in which the impurities P and B are within the specified range, the loss value at 100 ° C., 300 kHz, and 100 mT is 450 kW / m 3 or less, and the fracture toughness value is 1.10 MPa ⁇ m 1/2 or more. , Suitable magnetic properties and high toughness can be achieved at the same time. On the contrary, when one or both of the two components are contained more than the specified value, the loss value deteriorates due to the appearance of abnormal grains, and at the same time, the fracture toughness value also decreases, and the desired values are not obtained for both.
• Example 4 By the method shown in Example 1, the basic component and the sub-component have the same composition as in Example 1-2, but raw materials containing various amounts of impurities are used, and mixed, pulverized, and produced.
• the water used as the solvent for the slurry at the time of granulation unlike ordinary pure water or ion-exchanged water, tap water or mineral water with different hardness is used, or by intentionally adding a reagent, the sample is finally prepared. Using granulated powder prepared so that the amounts of Na, Mg, Al and K contained were different, a toroidal-shaped core and a flat plate-shaped core were formed by applying a pressure of 118 MPa.
• the molded bodies are inserted into a firing furnace and fired at a maximum temperature of 1320 ° C. for 2 hours in a gas stream in which nitrogen gas and air are appropriately mixed.
• a sintered toroidal-shaped core having an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm was obtained, and a sintered flat plate-shaped core having a length of 4 mm, a width of 35 mm, and a thickness of 3 mm was obtained.
• the characteristics of each of these samples were evaluated using the same method and equipment as in Example 1. The obtained results are shown in Table 4.
• the fracture toughness value is 1.10 MPa ⁇ m 1/2 or more, which is a good value. ..
• Comparative Examples 4-1 to 4-9 containing any one of Na, Mg, Al and K in a specified value or more the desired value of the magnetic property is obtained, but the fracture toughness value is 1. It has decreased to 10 MPa ⁇ m 1/2 or less. It is presumed that this decrease in toughness is due to the solid dissolution of Na, Mg, Al and K in the crystal grains, and the appearance of locally low toughness points.
• the crack occurrence rate of the molded product is as high as more than 3.5% in Comparative Examples 4-1 to 4-9. This is because the contents of Na, Mg, Al and K were not sufficiently suppressed in these comparative examples, so that the uniform dispersion of the binder was hindered, and the strength was weak because the amount of the binder was locally insufficient in the molded product. It is probable that this is because there are some spots and crack defects are more likely to appear.
• the MnZn-based ferrite defined in the present invention has good magnetic properties with a loss value of 450 kW / m 3 or less under exciting conditions of 300 kHz and 100 mT at 100 ° C., and a fracture toughness value of 1.10 MPa ⁇ m. It has both mechanical properties of 1/2 or more, and it is possible to reduce the crack occurrence rate of the molded body to 3.5% or less and manufacture it with good yield, so the magnetic core of electronic parts for automobiles in particular. Suitable for.

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