JPH0376762B2 - - Google Patents
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- Publication number
- JPH0376762B2 JPH0376762B2 JP59239888A JP23988884A JPH0376762B2 JP H0376762 B2 JPH0376762 B2 JP H0376762B2 JP 59239888 A JP59239888 A JP 59239888A JP 23988884 A JP23988884 A JP 23988884A JP H0376762 B2 JPH0376762 B2 JP H0376762B2
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- temperature
- Prior art date
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- 239000013078 crystal Substances 0.000 claims description 21
- 229910001035 Soft ferrite Inorganic materials 0.000 claims description 17
- 238000005245 sintering Methods 0.000 claims description 10
- 230000035699 permeability Effects 0.000 claims description 9
- 239000002994 raw material Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims description 4
- 238000001513 hot isostatic pressing Methods 0.000 claims description 3
- 239000002245 particle Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 description 10
- 238000000034 method Methods 0.000 description 7
- 239000011148 porous material Substances 0.000 description 7
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000000280 densification Methods 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000006249 magnetic particle Substances 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052573 porcelain Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
Landscapes
- Compounds Of Iron (AREA)
- Magnetic Ceramics (AREA)
- Soft Magnetic Materials (AREA)
Description
産業上の利用分野
この発明は、Mn−Zn系の多結晶ソフトフエラ
イトの熱間静水圧プレス成形方法の改良に係り、
密度が理論密度の99.9％以上あるソフトフエライ
ト及びその製造方法に関する。
従来の技術
ソフトフエライトで最も重要なことは初透磁率
であり、高透磁率を得るには結晶粒子を大きく、
原料を高密度にすると共に焼結密度を高くする必
要がある。
そのため、近年、ソフトフエライトを高密度化
するのに熱間静水圧プレス（以下HIP処理と称
す）成形法が採用されるようになり、磁気ヘツド
用ソフトフエライトを初めとする電子部品材料が
製造されている（例えば特公昭58−14050号）。
発明が解決しようとする問題点
通常、HIP処理された材料の特徴は、
密度が理論密度にほぼ同じ、
密度が高いのにもかかわらず、結晶の大きさ
が小さく、フエライトでは数μｍ〜数十μｍで
ある、
ことにある。そのため、HIP処理して製造された
フエライトを磁気ヘツド用材料として使用した場
合、加工性が良好で、磁気ヘツドとして磁気媒体
である磁気テープ、磁気デイスクと接触走行した
場合、結晶脱落による磁気ヘツドの劣化媒体への
悪影響がない長所がある。
しかしながら、近年HIP処理材の接触走行にお
いて、磁気ヘツドを媒体の相対速度が10ｍ／sec
以上で使用する用途への適用が検討されている
が、このように速度が大きくなると、もはやHIP
処理材といえども結晶の増落が免れなくなる。
上記のごとく、相対速度の大きい接触走行をす
る用途に適用できる材料としては、高密度で結晶
粒度が50μｍ以上の大きいものが適している。こ
のような材料を製造する方法としては、従来から
常圧、あるいは真空処理を組合せ、高温で焼結す
る方法が行れていた。しかし、この方法によれ
ば、密度は理論密度の99.6％以上で高密度化する
ことはできるが、第２図の写真に見られるよう
に、結晶粒内には残留気孔が存在し、満足できる
品質のものが得られない。
この発明は、かかる現状にかんがみ、Mn−Zn
系ソフトフエライトにおいて、密度が理論密度の
99.9％以上の高密度で、かつ大きな結晶粒度の組
織を有する材料をHIP処理を施して製造するもの
であり、予備焼結条件及びHIP処理条件の組合せ
により、理論密度にほぼ近い高密度材料で、大結
晶粒組織のソフトフエライトが得られるという知
見に基づくものである。
問題点を解決するための手段
この発明は、Fe2O351〜56モル％、MnO21〜
38モル％、ZnO6〜25モル％の組成からなり、密
度が理論密度の99.9％以上、平均結晶粒径が100μ
ｍ以上で、透磁率15000以上、保磁力0.03Oe以下
の磁気特性を有するMn−Zn系ソフトフエライ
ト、及び上記組成が得られるよう配合した原料の
成形体を1050〜1200℃に加熱して予備焼結し、密
度が理論密度の95％以上、平均結晶粒度が10μｍ
以下としたのち、前記焼結体を昇温速度150℃／
Hr以下で加熱し1200〜1400℃の温度範囲で前記
予備焼結温度より100℃以上高い温度に保持して
熱間静水圧プレス処理し、密度が理論密度の99.9
％以上、平均結晶粒径が100μｍ以上の成品が得
られるMn−Zn系ソフトフエライトの製造方法を
要旨とする。この発明のMn−Zn系ソフトフエラ
イトには１〜2.5μｍの微細孔は10個／100μm2以
下、2.5μｍ以上の微細孔は５個／100μm2以下存在
することが重要であり、微細孔が前記限定以上に
なると、気孔に磁粉が付着し、磁気ヘツドとして
の性能が劣化するので好ましくない。
なお、この発明における透磁率は100kHzにて
測定したときの値である。
この発明において成分組成を限定した理由につ
いて説明する。
Fe2O3は主原料であり、51モル％未満、56モル
％を超えると透磁率が15000以上、及び保磁力が
0.03Oe以下が得られないので51〜56モル％とし
た。
MnOは21モル％未満、38モル％を超えると、
透磁率15000以上、保磁力0.03Oe以下が得られ
ず、21〜38モル％とした。
ZnOは６モル％未満、25モル％を超えると
MnOと同様、透磁率15000以上、保磁力0.03Oe以
下が得られないので６〜25モル％とした。
又、密度は理論密度の99.9％以上としたのは、
それ未満では精密加工後の加工面に微細孔が露出
し、磁気特性が劣化すると共に、薄膜パターンの
断線等を生ずるので望ましくない。
平均結晶粒径が100μｍ以下では、磁気ヘツド
にして10ｍ／sec以上の速度で摺動させた場合、
結晶脱落が完全になくならないので好ましくな
い。
透磁率は15000未満では、再生出力が十分でな
く、又保磁力は0.03Oeを超えると、残留磁気に
より磁気媒体の信号を減ずるので好ましくない。
さらに、製造方法において予備焼結、HIP処理
等を限定したのは次の理由による。
予備焼結温度は、1050℃未満では焼結密度が理
論密度の95％以上とならず、1200℃を超えると後
工程のHIP処理において結晶粒径が100μｍ以上と
ならないから1050〜1200℃とした。
なお、予備焼結品の密度を理論密度の95％、平
均結晶粒度を10μｍ以下としたのは、後工程の
HIP処理において密度が理論密度の99.9％以上、
平均結晶粒径が100μｍ以上を得るために必要な
中間品質である。
HIP処理温度は、1200℃未満では100μｍ以上の
結晶粒径が得られず、1400℃を超えると媒体であ
るArガスによるフエライトの還元が顕著になり
品質が劣化するので1200〜1400℃とした。
又、HIP処理温度に加熱する際の昇温速度は、
150℃／Hrを超えると大きな結晶粒は得られるも
のの結晶粒内に気孔を含んだものとなるため、
150℃／Hr以下で昇温することが望ましい。
HIP処理圧力は、500Kg／cm2未満ではHIP処理
による高密度化が十分行われず残留気孔が生じ、
逆に2000Kg／cm2を超え高圧化しても作用、効果上
意味がないので500〜2000Kg／cm2とした。
そして、この発明におけるHIP処理温度は、前
記1200〜1400℃の温度範囲において、予備焼結時
に保持した温度より100℃以上高い温度に保持す
ることを条件としているが、これは大きな結晶粒
を得るために必要なことであり、前記温度より
100℃以下の高い温度では粒径100μｍ以上の結晶
粒は得られない。
実施例
実施例 １
原料としてFe2O352.5モル％、MnO26.7モル
％、ZnO20.8モル％を秤量しボールミルで十分に
混合したのち、空気中で900℃の仮焼結を行い、
さらにボールミルで粉砕し、平均粒径0.8μｍとし
た。この原料粉末にバインダーとしてPVA1重量
％を添加し造粒したのち、金型に装入し、圧力
2000Kg／cm2で加圧成型して寸法30×30×12mmの成
型体を作つた。
この成型体を２％酸素含有窒素ガス雰囲気中で
1140℃×３時間の予備焼結を行い純窒素中で冷却
し、密度4.92ｇ／cm2（理論密度の96％）、平均結
晶粒度6μｍで、磁気特性として透磁率3000、保
磁力0.15Oeの焼結体を得た。
次いで、この焼結体を高密度磁器容器に装入
し、空隙を同一組成の粉体で充填し、HIP処理装
置で昇温速度100℃／Hr、保持温度1250〜1300
℃、保持時間３時間、圧力1000Kg／cm2の条件で処
理した。又比較のため、昇温速度100〜200℃／
Hr、保持温度1100〜1250℃、保持時間３時間、
圧力1000Kg／cm2の条件で処理した。そして密度、
結晶粒度、磁気特性について試験した。その結果
を第１表に示す。
Industrial Application Field This invention relates to an improvement in a hot isostatic press forming method for Mn-Zn polycrystalline soft ferrite.
This invention relates to a soft ferrite having a density of 99.9% or more of the theoretical density and a method for producing the same. Conventional technology The most important thing for soft ferrite is the initial magnetic permeability, and in order to obtain high magnetic permeability, the crystal grains must be made large,
It is necessary to increase the density of the raw material and the sintering density. Therefore, in recent years, hot isostatic pressing (hereinafter referred to as HIP processing) has been adopted to increase the density of soft ferrite, and electronic component materials such as soft ferrite for magnetic heads have been manufactured. (For example, Special Publication No. 58-14050). Problems to be Solved by the Invention Normally, the characteristics of HIP-treated materials are that the density is almost the same as the theoretical density, and although the density is high, the crystal size is small, ranging from several μm to several tens of micrometers in the case of ferrite. In particular, it is μm. Therefore, when ferrite manufactured by HIP treatment is used as a material for a magnetic head, it has good workability, and when the magnetic head is run in contact with a magnetic tape or magnetic disk, which is a magnetic medium, the magnetic head may be damaged due to falling off of crystals. It has the advantage of not having any adverse effects on the deteriorating medium. However, in recent years, in contact running of HIP-treated materials, the relative speed of the magnetic head to the medium is 10 m/sec.
Application to the above-mentioned applications is being considered, but as the speed increases, it will no longer be possible to use HIP.
Even if the material is treated, crystals will inevitably increase and fall. As mentioned above, materials with high density and large crystal grain size of 50 μm or more are suitable as materials that can be used in contact running applications with high relative speeds. Conventionally, methods for producing such materials include sintering at high temperatures in combination with normal pressure or vacuum processing. However, according to this method, the density can be increased to 99.6% or more of the theoretical density, but as seen in the photograph in Figure 2, residual pores exist within the crystal grains, making it unsatisfactory. You can't get quality products. In view of the current situation, the present invention has been made to
In soft ferrite, the density is the theoretical density.
It is manufactured by HIPing a material that has a high density of 99.9% or more and a structure with large grain size.The combination of pre-sintering conditions and HIP processing conditions results in a high-density material that is almost close to the theoretical density. This is based on the knowledge that soft ferrite with a large grain structure can be obtained. Means for Solving the Problems This invention is based on Fe 2 O 3 51~56 mol%, MnO2 1~
38 mol%, ZnO6~25 mol%, density is 99.9% or more of theoretical density, average grain size is 100μ
Mn-Zn soft ferrite having magnetic properties of 15,000 or more and a coercive force of 0.03 Oe or more, and a molded body of raw materials blended to obtain the above composition are heated to 1050-1200°C and pre-baked. The density is 95% or more of the theoretical density, and the average grain size is 10 μm.
After heating the sintered body at a heating rate of 150℃/
Hr or less and hot isostatic pressing by holding at a temperature of 1200 to 1400℃ and at least 100℃ higher than the pre-sintering temperature, and the density is 99.9 of the theoretical density.
% or more and an average crystal grain size of 100 μm or more. It is important that the Mn-Zn soft ferrite of this invention has 10 to 2.5 μm micropores/100 μm 2 or less and 2.5 μm or more micropores 5/100 μm 2 or less. If it exceeds the above limit, magnetic particles will adhere to the pores and the performance as a magnetic head will deteriorate, which is not preferable. Note that the magnetic permeability in this invention is a value measured at 100kHz. The reason for limiting the component composition in this invention will be explained. Fe2O3 is the main raw material, and when it is less than 51 mol% and more than 56 mol%, the magnetic permeability is 15000 or more, and the coercive force is
Since 0.03 Oe or less could not be obtained, the content was set at 51 to 56 mol%. MnO is less than 21 mol%, and when it exceeds 38 mol%,
It was not possible to obtain a magnetic permeability of 15,000 or more and a coercive force of 0.03 Oe or less, so it was set to 21 to 38 mol%. ZnO is less than 6 mol%, and if it exceeds 25 mol%
Like MnO, a magnetic permeability of 15,000 or more and a coercive force of 0.03 Oe or less cannot be obtained, so the content was set at 6 to 25 mol%. Also, the density was set to be 99.9% or more of the theoretical density because
If it is less than that, fine holes will be exposed on the machined surface after precision processing, the magnetic properties will deteriorate, and the thin film pattern will be disconnected, which is not desirable. When the average crystal grain size is 100 μm or less, when the magnetic head is slid at a speed of 10 m/sec or more,
This is not preferable because crystal shedding is not completely eliminated. If the magnetic permeability is less than 15,000, the reproduction output will not be sufficient, and if the coercive force exceeds 0.03 Oe, the signal of the magnetic medium will be reduced due to residual magnetism, which is not preferable. Furthermore, the reasons for limiting preliminary sintering, HIP treatment, etc. in the manufacturing method are as follows. The preliminary sintering temperature was set at 1050 to 1200°C because if it is less than 1050°C, the sintered density will not reach 95% or more of the theoretical density, and if it exceeds 1200°C, the grain size will not reach 100 μm or more in the HIP process in the subsequent process. . The density of the pre-sintered product was set to 95% of the theoretical density and the average grain size was set to 10 μm or less because of the post-process.
In HIP treatment, the density is 99.9% or more of the theoretical density,
This is an intermediate quality necessary to obtain an average crystal grain size of 100 μm or more. The HIP treatment temperature was set at 1200 to 1400°C because if it is less than 1200°C, a crystal grain size of 100 μm or more cannot be obtained, and if it exceeds 1400°C, the reduction of ferrite by Ar gas as a medium becomes significant and the quality deteriorates. In addition, the temperature increase rate when heating to the HIP treatment temperature is
If the temperature exceeds 150℃/Hr, large crystal grains can be obtained, but the crystal grains will contain pores, so
It is desirable to raise the temperature at 150℃/Hr or less. If the HIP treatment pressure is less than 500Kg/ cm2 , the densification by HIP treatment will not be sufficient and residual pores will occur.
On the other hand, increasing the pressure beyond 2000 Kg/cm 2 is meaningless in terms of function and effect, so it was set at 500 to 2000 Kg/cm 2 . The HIP treatment temperature in this invention is kept at a temperature 100°C or more higher than the temperature held during preliminary sintering in the temperature range of 1200 to 1400°C, which is necessary to obtain large crystal grains. This is necessary for
At high temperatures below 100°C, crystal grains with a grain size of 100 μm or more cannot be obtained. Examples Example 1 Weighed 52.5 mol% of Fe 2 O 3 , 6.7 mol% of MnO, and 0.8 mol% of ZnO as raw materials, mixed them thoroughly in a ball mill, and pre-sintered them at 900°C in air.
It was further ground in a ball mill to give an average particle size of 0.8 μm. After adding 1% by weight of PVA as a binder to this raw material powder and granulating it, it is charged into a mold and pressure
A molded body with dimensions of 30 x 30 x 12 mm was made by pressure molding at 2000 kg/cm 2 . This molded body was placed in a nitrogen gas atmosphere containing 2% oxygen.
Preliminary sintering was performed at 1140°C for 3 hours and cooled in pure nitrogen, resulting in a density of 4.92g/cm 2 (96% of theoretical density), average grain size of 6μm, magnetic properties of permeability of 3000 and coercive force of 0.15Oe. A sintered body was obtained. Next, this sintered body is placed in a high-density porcelain container, the voids are filled with powder of the same composition, and heated at a heating rate of 100°C/Hr and a holding temperature of 1250 to 1300 in a HIP processing device.
℃, holding time for 3 hours, and pressure of 1000 Kg/cm 2 . For comparison, the temperature increase rate is 100 to 200℃/
Hr, holding temperature 1100-1250℃, holding time 3 hours,
The treatment was carried out at a pressure of 1000 Kg/cm 2 . and density,
The grain size and magnetic properties were tested. The results are shown in Table 1.
【表】
ただし：(1) 比較例１には結晶粒内に残留気
孔が認められた。
(2) 密度5.12g／cm3は理論密度の99.
9％以上の値である。
上記結果より、この発明の実施によるものは密
度、平均結晶粒径、及び磁気特性すべてが所望範
囲内にあつて磁気ヘツド用ソフトフエライトとし
て優れていることがわかる。
又、上記発明法１の試料について組織試験をし
た結果、第１図の顕微鏡写真に示すように、結晶
粒内の気孔は比較例のものに比べ著しく少ないこ
とがわかる。
実施例 ２
実施例１と同じ条件の製造方法により、原料の
配合を変えて、この発明を実施した。そして、密
度、結晶粒径、磁気特性を試験した。その結果を
第２表に示す。[Table] However: (1) In Comparative Example 1, residual pores were observed within the crystal grains.
(2) Density 5.12g/cm 3 is the theoretical density of 99.
The value is 9% or more.
From the above results, it can be seen that the density, average grain size, and magnetic properties of the soft ferrite according to the present invention are all within the desired range, and are excellent as soft ferrites for magnetic heads. Further, as a result of microstructural testing of the sample of Invention Method 1, as shown in the micrograph of FIG. 1, it was found that the number of pores within the crystal grains was significantly smaller than that of the comparative example. Example 2 This invention was carried out using the manufacturing method under the same conditions as in Example 1, but with different blends of raw materials. Then, the density, grain size, and magnetic properties were tested. The results are shown in Table 2.
【表】
発明の効果
この発明は上記のごとく、Mn−Zn系ソフトフ
エライトの製造において、予備焼結条件及びHIP
処理条件を組合せて規制することにより、理論密
度に近い高密度で大結晶粒の組織を有し、結晶粒
内に残留気孔が少なく磁気特性に優れ磁気ヘツド
用として最適のソフトフエライトを生産できる。[Table] Effects of the Invention As described above, the present invention is applicable to preliminary sintering conditions and HIP in the production of Mn-Zn soft ferrite.
By controlling the combination of processing conditions, it is possible to produce soft ferrite that has a high density close to the theoretical density, has a large crystal grain structure, has few residual pores in the crystal grains, has excellent magnetic properties, and is optimal for use in magnetic heads.
第１図はこの発明の実施によるMn−Zn系ソフ
トフエライトの組織を示す顕微鏡写真、第２図は
従来の方法により作られたMn−Zn系ソフトフエ
ライトの組織を示す顕微鏡写真である。
FIG. 1 is a microphotograph showing the structure of Mn--Zn soft ferrite produced according to the present invention, and FIG. 2 is a microphotograph showing the structure of Mn--Zn soft ferrite produced by the conventional method.
Claims (1)
ZnO6〜25モル％の組成からなり、密度が理論密
度の99.9％以上、平均結晶粒径が100μｍ以上で、
透磁率15000以上、保磁力0.03Oe以下の磁気特性
を有することを特徴とするMn−Zn系ソフトフエ
ライト。 ２ Fe2O351〜56モル％、MnO21〜38モル％、
ZnO6〜25モル％の組成が得られるよう配合した
原料の成形体を1050〜1200℃に加熱して予備焼結
し、密度が理論密度の95％以上、平均結晶粒度が
10μｍ以下としたのち、前記焼結体を昇温速度
150℃／Hr以下で加熱し1200〜1400℃の温度範囲
で前記予備焼結温度より100℃以上高い温度に保
持して熱間静水圧プレス処理し、密度が理論密度
の99.9％以上、平均結晶粒径が100μｍ以上の成品
が得られることを特徴とするMn−Zn系ソフトフ
エライトの製造方法。[Claims] 1 Fe 2 O 3 51 to 56 mol%, MnO2 1 to 38 mol%,
It is composed of ZnO6 to 25 mol%, has a density of 99.9% or more of the theoretical density, and an average crystal grain size of 100 μm or more.
A Mn-Zn soft ferrite characterized by having magnetic properties of magnetic permeability of 15,000 or more and coercive force of 0.03 Oe or less. 2 Fe 2 O 3 51-56 mol%, MnO21-38 mol%,
A molded body of raw materials blended to obtain a composition of 6 to 25 mol% ZnO is heated to 1050 to 1200°C and pre-sintered, and the density is 95% or more of the theoretical density and the average grain size is
After reducing the diameter to 10 μm or less, the sintered body is heated at a rate of
Heating at 150℃/Hr or less and holding at a temperature of 100℃ or more higher than the pre-sintering temperature in the temperature range of 1200 to 1400℃ and hot isostatic pressing to produce a density of 99.9% or more of the theoretical density and an average crystal. A method for producing Mn-Zn soft ferrite, characterized in that a product having a particle size of 100 μm or more is obtained.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59239888A JPS61117804A (en) | 1984-11-14 | 1984-11-14 | Mn-zn system soft ferrite and manufacture thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP59239888A JPS61117804A (en) | 1984-11-14 | 1984-11-14 | Mn-zn system soft ferrite and manufacture thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61117804A JPS61117804A (en) | 1986-06-05 |
| JPH0376762B2 true JPH0376762B2 (en) | 1991-12-06 |
Family
ID=17051359
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP59239888A Granted JPS61117804A (en) | 1984-11-14 | 1984-11-14 | Mn-zn system soft ferrite and manufacture thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61117804A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63157407A (en) * | 1986-12-22 | 1988-06-30 | Sony Corp | Manufacture of high-density ferrite |
| JPH0618132B2 (en) * | 1987-05-29 | 1994-03-09 | 日本碍子株式会社 | Method for producing polycrystalline ferrite |
| JP2907253B2 (en) * | 1993-03-05 | 1999-06-21 | 日立金属 株式会社 | High permeability Mn-Zn ferrite |
| WO2000014752A1 (en) * | 1998-09-07 | 2000-03-16 | Tdk Corporation | Manganese-zinc ferrite and method for producing the same |
-
1984
- 1984-11-14 JP JP59239888A patent/JPS61117804A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61117804A (en) | 1986-06-05 |
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