Hitachi Metals, Ltd.

Hitachi Ferrite Electronics, Ltd.

Hitachi Ferrite, Ltd.

Proterial, Ltd.

Norikazu Koyuhara

Tomoyuki Tada

Yasuharu Miyoshi

Satoru Tanaka

Toshihiko Tanaka

Shiro Murakami

Hitoshi Ueda

Akio Uchikawa

Makoto Kadowaki

Emi Nakagawa

Yoshihito Yoshikawa

Youichi Yamamoto

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 sintered Ni ferrite body having a composition comprising, calculated as oxide, 47.0-48.3% by mol of FeO, 14.5% or more and less than 25% by mol of ZnO, 8.2-10.0% by mol of CuO, and more than 0.6% and 2.5% or less by mol of CoO, the balance being NiO and inevitable impurities, and having an average crystal grain size of more than 2.5 &#x3bc;m and less than 5.5 &#x3bc;m.

Sintered Ni ferrite body, coil device, and method for producing sintered Ni 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 ferrite core for use in coupling transformers and distributing transformers in CATV equipments such as couplers, distributors and amplifiers, the ferrite core being made of a ferrite having a saturation magnetostriction |&#x3bb;| of 8&#xd7;10or less in an absolute value and an initial permeability &#x3bc;of 300 or more.

Ferrite core, CATV equipment and bi-directional CATV system

Magnetic core

A Ni ferrite sintered body comprising 48.0-50.0 mol % of Fe.sub.2 O.sub.3, 14.0-24.0 mol % of NiO and 28.0-36.0 mol % of ZnO with 50 ppm or less of P as an impurity, the sintered body having a minimum core loss of 30 kW/m.sup.3 or less at 50 kHz and 50 mT, and the segregation percentage of P in the crystal structure being 1% or less by area. The Ni ferrite sintered body preferably has an average crystal grain size of 3-30 .mu.m, the percentage of crystal grain particles larger than two times the average crystal grain size being preferably 10% or less based on the total number of the crystal grain particles in a crystal structure.

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Tokyo, Japan

Norikazu Koyuhara