Hitachi Metals, Ltd.

Proterial, Ltd.

Yasuharu Miyoshi

Tomoyuki Tada

Norikazu Koyuhara

Satoru Tanaka

Toru Umeno

Shinroh Itoh

Takeshi Yanagihara

A sintered MnZn ferrite body containing main components comprising 53.30-53.80% by mol of Fe calculated as FeO, 6.90-9.50% by mol Zn calculated as ZnO, and the balance of Mn calculated as MnO, and sub-components comprising 0.003-0.020 parts by mass of Si calculated as SiO, more than 0 parts and 0.35 parts or less by mass of Ca calculated as CaCO, 0.30-0.50 parts by mass of Co calculated as CoO, 0.03-0.10 parts by mass of Zr calculated as ZrO, and 0-0.05 parts by mass of Ta calculated as TaO, pre 100 parts by mass in total of the main components (calculated as the oxides), and having an average crystal grain size of 3 &#x3bc;m or more and less than 8 &#x3bc;m and a density of 4.65 g/cmor more.

Sintered MnZn ferrite body

A method for producing a MnZn ferrite core used at a frequency of 1 MHz or more and an exciting magnetic flux density of 75 mT or less, the MnZn ferrite comprising 53-56% by mol of Fe (calculated as FeO), and 3-9% by mol of Zn (calculated as ZnO), the balance being Mn (calculated as MnO), as main components, and 0.05-0.4 parts by mass of Co (calculated as CoO) as a sub-component, per 100 parts by mass in total of the main components (calculated as the oxides); comprising a step of molding a raw material powder for the MnZn ferrite to obtain a green body; a step of sintering the green body and cooling it to a temperature of lower than 150&#xb0; C. to obtain a sintered body of MnZn ferrite; and a step of conducting a heat treatment comprising heating the sintered body of MnZn ferrite to a temperature meeting Condition 1 of 200&#xb0; C. or higher, and Condition 2 of (Tc&#x2212;90)&#xb0; C. to (Tc+100)&#xb0; C., wherein Tc is a Curie temperature (&#xb0; C.) calculated from the percentages by mol of FeOand ZnO contained in the main components of the MnZn ferrite, keeping the sintered body at the above temperature for a predetermined period of time, and then cooling the sintered body from the keeping temperature at a speed of 50&#xb0; C./hour or less.

MnZn ferrite core and its production method

A method for producing MnZn-ferrite comprising Fe, Mn and Zn as main components, and at least Co, Si and Ca as sub-components, the main components in the MnZn-ferrite comprising 53-56% by mol (as FeO) of Fe, and 3-9% by mol (as ZnO) of Zn, the balance being Mn as MnO, comprising the step of sintering a green body to obtain MnZn-ferrite; the sintering comprising a temperature-elevating step, a high-temperature-keeping step, and a cooling step; the high-temperature-keeping step being conducted at a keeping temperature of higher than 1050&#xb0; C. and lower than 1150&#xb0; C. in an atmosphere having an oxygen concentration of 0.4-2% by volume; the oxygen concentration being in a range of 0.001-0.2% by volume during cooling from 900&#xb0; C. to 400&#xb0; C. in the cooling step; and the cooling speed between (Tc+70)&#xb0; C. and 100&#xb0; C. being 50&#xb0; C./hour or more, wherein Tc represents a Curie temperature (&#xb0; C.) calculated from % by mass of FeOand ZnO.

MnZn-ferrite and its production method

A method for producing MnZn ferrite comprising Fe, Mn and Zn as main components, and Ca, Si and Co, and at least one selected from the group consisting of Ta, Nb and Zr as sub-components, comprising a step of molding a raw material powder for the MnZn ferrite to obtain a green body, and a step of sintering the green body; the sintering step comprising a temperature-elevating step, a high-temperature-keeping step, and a cooling step; the cooling step including a slow cooling step of cooling in a temperature range of 1100&#xb0; C. to 1250&#xb0; C. at a cooling speed of 0&#xb0; C./hour to 20&#xb0; C./hour for 1 hours to 20 hours, and a cooling speed before and after the slow cooling step being higher than 20&#xb0; C./hour; the MnZn ferrite having a volume resistivity of 8.5 &#x3a9;&#xb7;m or more at room temperature, an average crystal grain size of 7 &#x3bc;m to 15 &#x3bc;m, and core loss of 420 kW/mor less between 23&#xb0; C. and 140&#xb0; C. at a frequency ofkHz and an exciting magnetic flux density of 200 mT.

MnZn ferrite and its production method

Provided are: a MnZn-based ferrite which allows to have a low magnetic core loss and to suppress a time-dependent change of magnetic property under a high-temperature environment by a control of ambient oxygen concentration and an increase of the magnetic core loss, and a method for manufacturing the same. The MnZn-based ferrite is characterized in that Fe ranges from 53.25 mol % or more to 54.00 mol % or less on the basis of FeO, Zn ranges from 2.50 mol % or more to 8.50 mol % or less on the basis of ZnO and Mn is the remainder on the basis of MnO, Si ranges from more than 0.001 mass % to less than 0.02 mass % on the basis of SiO, Ca ranges from more than 0.04 mass % to less than 0.4 mass % on the basis of CaCO, Co is less than 0.5 mass % on the basis of CoO, Bi is less than 0.05 mass % on the basis of BiO, Ta is less than 0.05 mass % on the basis of TaO, Nb is less than 0.05 mass % on the basis of NbO, Ti is less than 0.3 mass % on the basis of TiO, and Sn is less than 0.3 mass % on the basis of SnO, and note that the converted total amount of TaOand NbOis less than 0.05 mass % and the converted total amount of TiOand SnOis less than 0.3 mass %.

MnZn-based ferrite and method for manufacturing the same

A sintered ferrite material, which is obtained by adding BiOin a range from 0.5% by mass to 3% by mass against 100% by mass of a material having a composition formula of (1-x-y-z)(LiFe)O.xZnO.yFeO.zCuO wherein x, y and z satisfy 0.14&#x2266;x&#x2266;0.19, 0.48&#x2266;y&#x3c;0.5 and 0&#x2266;z&#x2266;0.03 and satisfies resistivity equal to or higher than 10&#x3a9;m, initial permeability equal to or higher than 200 and saturation magnetic flux density equal to or higher than 430 mT at 23&#xb0; C. and equal to or higher than 380 mT at 100&#xb0; C.

Sintered ferrite material, wire wound component, and producing method of sintered ferrite material

A radio wave absorption material is characterized to be obtained by firing a ferrite material that is formed by adding an accessory component, 0.1 to 2 wt % of CoO, to an oxide magnetic material containing main components, 30 to 49.5 mol % of FeO, 0.5 to 20 mol % of MnO, 5 to 35 mol % of ZnO, 0.2 to 15 mol % of (LiFe)O and MnO as the rest. In the above-mentioned composition, part of ZnO may be replaced with 20 mol % or less of CuO. This radio wave absorption material has high strength and humidity stability and has excellent radio wave absorption performance although low in cost.

Radio wave absorption material and radio wave absorber

The invention provides a ferrite material (ferrite sintered body, ferrite powders) having a composition formula of (1-x-y-z)(LiFe)O.xZnO.y(Mn, Fe)O.zCuO, wherein x, y, z, and a satisfy 0.175&#x2266;x&#x2266;0.29; 0.475&#x2266;y&#x2266;0.51; 0.07&#x2266;z&#x2266;0.22; and 0.02&#x2266;a&#x2266;0.055 in a case of a=Mn/(Mn+Fe). At least one of Co oxide, Co hydroxide, and Co carbonate in an amount of 1 wt. % or less on the basis of CoO may be contained in 100 wt % of the ferrite material. The ferrite material has a normalized impedance Zof 40000 &#x3a9;/m or more at 30 MHz and a normalized impedance Zof 60000 &#x3a9;/m or more at 100 MHz as well as a specific resistance of 10&#x3a9;m or more.

Ferrite material and method for producing ferrite material

The laminate device of the present invention comprises magnetic layers and coil patterns alternately laminated, the coil patterns being connected in a lamination direction to form a coil, and pluralities of magnetic gap layers being disposed in regions in contact with the coil patterns.

Laminate device and module comprising same

A ferrite material in which BiOis added at 6% by weight or less, and preferably 4% by weight or less, to a ferrite of Li&#x2014;Zn&#x2014;(Mn, Fe) containing a specified amount of Mn. In the ferrite material, change of magnetic permeability under high external stress is extremely small, and a core loss under a compression stress is small. By using this ferrite material, an inductor and transformer having small loss even in a state of being molded with resin can be obtained.

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Tokyo, Japan

Yasuharu Miyoshi