JP3590465B2 - Method for producing low-loss oxide magnetic material - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a low loss oxide magnetic materials, more particularly to a method of manufacturing a Mn-Zn ferrite which is mounted on the switching power supply or the like.
[0002]
[Prior art]
Conventionally, Mn-Zn ferrite has been used as a low-loss oxide magnetic material used for a switching power supply or the like, and its driving frequency is frequently used at about 100 kHz to 200 kHz. In this frequency band, there is a demand for high performance and low cost magnetic materials.
[0003]
In general, the magnetic core using a Mn-Zn ferrite power applications in this frequency band, the eddy current loss (hereinafter, referred to as P _e) and hysteresis loss (hereinafter, referred to as P _h) has the initiative, the How to reduce both is an extremely important issue.
[0004]
In order to reduce the P _e is, Mn-Zn ferrite sintered body (hereinafter referred to as ferrite sintered body) grain boundary phase, or it is essential to improve the electrical resistance of the spinel phase.
[0005]
As a method of improving the electrical resistance of the spinel phase itself, by increasing the oxygen partial pressure of the sintering conditions, a decrease in ^{Fe 2+,} or ^Ti 4+, for the additional inclusion of ^{Sn 4+,} by substituting the ^{Fe 3+,} and ^{Fe 2+} There is a method of suppressing the occurrence of the electron hopping phenomenon between Fe ³⁺ .
[0006]
However, the former causes remarkable deterioration of μi due to an extreme decrease of Fe ²⁺ and deterioration of magnetic characteristics such as increase of Hc. In the latter case, the temperature at which the value of the power loss is minimum (hereinafter, referred to as a minimum point) in the temperature characteristics of the power loss is not preferable because the temperature significantly moves to the low temperature side. Furthermore, both methods have the greatest drawback that the electric resistance of the ferrite sintered body does not increase so much even if the electric resistance of the spinel phase itself is improved.
[0007]
On the other hand, as a method of improving the electric resistance of the grain boundary phase, a method of forming a high-resistance grain boundary phase by adding SiO ₂ and CaO is generally known.
[0008]
This method is the most effective and most frequently used method for improving the resistance of the ferrite sintered body. At this time, by adding an appropriate SiO 2, _CaO, grain can growth inhibition, uniform grain structure is obtained, it is possible to reduce the P _h.
[0009]
Incidentally, in general, when the P ₂ O ₅ in Mn-Zn ferrite containing, liable grain size becomes uneven, not only P _h increases, also significantly increased P _e, the magnetic core The characteristics deteriorate. Further, as described above, to improve the electrical resistance of the grain boundary _phase, in the case of adding SiO 2, CaO, it tends to be less _uniform, P h, _{P e} both significantly deteriorated.
[0010]
P ₂ O ₅ is mainly contained in a large amount in the iron oxide raw material in many cases, and it is inexpensive compared to those not containing the price. Therefore, since the crystal grain size cannot be made uniform and the electrical resistance of the grain boundary phase cannot be sufficiently improved, an increase in power loss is caused. Was unusable.
[0011]
As described above, by using the iron oxide raw material containing P ₂ O _5, an oxide magnetic material Mn-Zn ferrite having excellent magnetic properties having a uniform crystal grain size was not obtained.
[0012]
[Problems to be solved by the invention]
The present invention uses iron oxide raw material containing P ₂ O ₅ in high concentration, even in a frequency range of up to about several tens KHz～100kHz, a manufacturing method of suppressing the amount of heat generated low-loss oxide magnetic materials To provide.
[0013]
[Means for Solving the Problems]
To solve the above problems, the results of various studies, the present inventors have relatively low cost of the P ₂ O ₅ content of iron oxide material obtained, 0.01 The content _of P ₂ O ₅ with iron oxide raw material is limited to 0.1 wt%, Na ₂ O less 0.12 wt% (0 to not included), the SiO ₂ 0.004~0.025wt%, the CaO 0.03 to 0. It has been found that by containing 12 wt% each, an oxide magnetic material having high electric resistance and excellent magnetic properties can be obtained.
[0015]
That is, in the present invention, the main components are composed of 52 to 54 mol% of ferric oxide (Fe ₂ O ₃ ), 33 to 37 mol% of manganese oxide (MnO), and the balance of zinc oxide (ZnO). . 007~0. 07wt% of phosphorus pentoxide (P ₂ O _5), 0 sodium oxide. 12 wt% or less (not including _{0) (Na 2 O), 0} . 004~0. 025wt% of silicon oxide ( SiO _2), 0. 03~0. containing 12 wt% of calcium oxide (CaO) a method for producing a low loss oxide magnetic material, phosphorus pentoxide (P ₂ O ₅₎ content as the starting material is, with 0.01 to 0.1% iron oxide raw material powder, (not including 0) 0.43 wt% or less of sodium diiron (NaFeO ₂₎ low-loss oxide magnetic material characterized by adding It is a manufacturing method.
[0016]
In the present invention, the reason why Fe ₂ O ₃ is 52 to 54 mol% and MnO is 33 to 37 mol% is that when Fe ₂ O ₃ is less than 52 mol% or MnO exceeds 37 mol%, power loss increases and Fe _{If the amount of 2} O ₃ exceeds 54 mol% or the amount of MnO is less than 33 mol%, the minimum point of power loss is low, which is not preferable.
[0017]
The reason that the content of P ₂ O ₅ in the iron oxide raw material is set to 0.01 to 0.1 wt% is that an iron oxide raw material of less than 0.01 wt% is suitable for improving the performance of ferrite, but is generally high in ferrite. This is because the price is not suitable for the purpose of the present invention. On the other hand, if the content exceeds 0.1 wt%, even if Na ₂ O is contained, it becomes difficult to control the grain growth and the magnetic properties are degraded.
[0018]
The reason why the SiO ₂ content is 0.004 wt% or more and the CaO content is 0.03 wt% or more is that if the content is less than 0.004 wt% and less than 0.03 wt%, sufficient electric resistance cannot be obtained. This is because eddy current loss increases and magnetic characteristics deteriorate. Also, the reason why the SiO ₂ content is 0.025 wt% or less and the CaO content is 0.12 wt% or less is that if the content exceeds 0.025 wt% and 0.12 wt%, respectively, the crystal grain size becomes extremely non-uniform, This is because the magnetic characteristics deteriorate.
[0019]
In addition, the use of NaFeO ₂ as Na ₂ O in the production of Mn—Zn ferrite has the effect of suppressing the variation in the structure of the sintered body, that is, the crystal grain size is reduced by facilitating the control of grain growth. This is because there is an effect of easily obtaining a uniform structure. The same effect can be obtained by adding sodium in the form of an oxide, a carbonate, a nitrate, or a chloride as well as a complex oxide with iron. However, it is more preferable to add a composite oxide. Na ₂ O is unstable in the air and is not industrially suitable.
[0020]
The reason that the content of Na ₂ O or less 0.12 wt%, when it exceeds 0.12 wt%, conversely, it is difficult to control the grain _growth, is to cause an increase in P h, _{P e} .
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below.
[0022]
(Example 1)
Iron oxide, manganese oxide, and zinc oxide raw materials were used as main components, and were weighed so as to have a composition of 53.0 mol%, 35.5 mol%, and 11.5 mol%, respectively, in terms of Fe ₂ O ₃ , MnO, and ZnO. . The P ₂ O ₅ content is set to be 0.007, 0.012, 0.022, 0.03, 0.035, 0.051, 0.07, 0.074 wt% in the ferrite sintered body. I made it. In addition, iron oxide raw materials having a P ₂ O ₅ content of 0.012, 0.034, and 0.096 wt%, respectively, were mixed and used to prepare the above ratio.
[0023]
Further, 0.125 wt% of NaFeO ₂ was added as a sub-component so as to be 0.035 wt% in terms of Na ₂ O. Further, the SiO ₂ 0.016wt%, CaO was added respectively so that 0.08 wt%.
[0024]
These powders were mixed, pre-fired, crushed, granulated, pressed after forming, and fired at an oxygen partial pressure of 10.0% or less and a temperature of 1200 to 1400 ° C. to obtain a sintered body.
[0025]
FIG. 1 shows the power loss at a frequency of 100 kHz, a magnetic flux density of 2,000 G, and a temperature of 80 ° C. when the P ₂ O ₅ content was used as a parameter in the obtained ferrite sintered body.
[0026]
From FIG. 1, it can be seen that when the P ₂ O ₅ content in the ferrite sintered body is 0.07 wt% or more, the power loss significantly increases.
[0027]
(Example 2)
Using an iron oxide raw material mixed so that P ₂ O ₅ becomes 0.025 wt%, 0.016 wt% of SiO ₂ and 0.08 wt% of CaO are used as subcomponents with respect to the main component similar to that of Example 1. , And further added with Na ₂ O at 0, 0.011, 0.022, 0.036, 0.056, 0.071, 0.094, 0.113, 0.12, 0. NaFeO ₂ was added at 0, 0.036, 0.073, 0.127, 0.2, 0.25, 0.346, 0.4, 0.43, 0.455 wt% so as to be 127 wt%, A ferrite sintered body was obtained in the same manner as in Example 1.
[0028]
FIG. 2 shows the power loss at a frequency of 100 kHz, a magnetic flux density of 2,000 G, and a temperature of 80 ° C. when the Na ₂ O content is used as a parameter of the obtained ferrite sintered body.
[0029]
FIG. 2 shows that when the Na ₂ O content in the ferrite sintered body exceeds 0.12 wt%, the power loss increases significantly.
[0030]
(Example 3)
Using an iron oxide raw material mixed so that P ₂ O ₅ becomes 0.025 wt%, a main component similar to that in Example 1 was used, and as an auxiliary component, 0.035 wt% in terms of Na ₂ O as a subcomponent. the NaFeO ₂ was added 0.125 wt%, further, 0.08 wt% of CaO, the SiO ₂ 0.002,0.004,0.007,0.01,0.016,0.02,0.025, Each was added so as to be 0.03 wt%, and a ferrite sintered body was obtained in the same manner as in Example 1.
[0031]
FIG. 2 shows the power loss at a frequency of 100 kHz, a magnetic flux density of 2000 G, and a temperature of 80 ° C. when the SiO ₂ content of the obtained ferrite sintered body was used as a parameter.
[0032]
FIG. 2 shows that when the SiO ₂ content in the ferrite sintered body is 0.004 to 0.025 wt%, a low power loss is exhibited.
[0033]
(Example 4)
Using an iron oxide raw material mixed so that P ₂ O ₅ becomes 0.025 wt%, a main component similar to that in Example 1 was used, and as an auxiliary component, 0.035 wt% in terms of Na ₂ O as a subcomponent. the NaFeO ₂ was added 0.125 wt%, further, the SiO ₂ 0.016wt%, the CaO content in the parameter 0.02,0.03,0.05,0.06,0.08,0.1 , 0.12, and 0.15 wt%, respectively, and a ferrite sintered body was obtained in the same manner as in Example 1.
[0034]
FIG. 4 shows the power loss at a frequency of 100 kHz, a magnetic flux density of 2000 G, and a temperature of 80 ° C. when the CaO content of the obtained ferrite sintered body was used as a parameter under the same conditions as in Example 1.
[0035]
FIG. 4 shows that when the CaO content in the ferrite sintered body is 0.03 to 0.12 wt%, a low power loss is exhibited.
[0036]
【The invention's effect】
As is clear from the above, according to the present invention, an iron oxide raw material containing P ₂ O ₅ is used which is inexpensive and easily obtainable as an iron oxide raw material, and is excellent in suppressing heat generation even in a frequency range around 100 kHz. and it was able to provide a method for producing Mn-Zn ferrite of the low-loss oxide magnetic materials having magnetic properties.
[Brief description of the drawings]
FIG. 1 is a characteristic diagram showing a relationship of Pcv to P ₂ O ₅ content in a ferrite sintered body manufactured in Example 1.
FIG. 2 is a characteristic diagram showing the relationship between Pcv and Na ₂ O content in a ferrite sintered body manufactured in Example 2.
FIG. 3 is a characteristic diagram showing a relationship between Pcv and SiO ₂ content in a ferrite sintered body manufactured in Example 3.
FIG. 4 is a characteristic diagram showing the relationship between Pcv and CaO content in a ferrite sintered body manufactured in Example 4.

Claims (1)

Main component 52～54Mol% ferric oxide _{(Fe 2 O 3), 33~37mol} % of manganese oxide (MnO), and it becomes than the rest of zinc oxide (ZnO), further, 0. 007~0. 07wt % of phosphorus pentoxide (P ₂ O _5), 0 sodium oxide. 12 wt% or less (not including _{0) (Na 2 O), 0} . 004~0. 025wt% of silicon oxide (SiO _2), 0. 03-0. containing 12 wt% of calcium oxide (CaO) a method for producing a low loss oxide magnetic material, is phosphorus pentoxide (P ₂ O ₅₎ content as a starting material, 0.01 to 0. with 1 wt% of iron oxide raw material powder, sodium dioxide iron (NaFeO ₂₎ (not including 0) 0.43 wt% or less manufacturing method of low-loss oxide magnetic material you comprises adding.

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