JPH09129431A - Low loss oxide magnetic material and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low cost and low loss oxide magnetic material having a high performance inspite of using an iron inexpensive iron oxide material containing a high content of impurities. SOLUTION: Mn-Zn ferrite showing an excellent Pcv value can be obtained by using an inexpensive iron oxide material containing P2 O5 of 0.01 to 0.1wt.%, preferably 0.01 to 0.05wt.% as impurities, and by containing Fe2 O3 of 52 to 54mol%, Mn O of 33 to 37mol%, ZnO of 9 to 15mol% as main components, SiO2 of 0.005 to 0.025wt.%, CaO of 0.02 to 0.10wt.%, Cr2 O3 of 0.1 to 3.0wt.% as subcomponents, further at least one kind of Ta2 O5 and Nb2 O5 not exceeding 0.08wt.% (exclusive of 0) in its total volume.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low loss oxide magnetic material and a method for producing the same, and more particularly to a Mn-Zn ferrite used as a transformer material for various power sources such as a switching power source and a method for producing the same. .

[0002]

2. Description of the Related Art In recent years, with the reduction in size and weight of various electronic devices, further reduction in size and weight of switching power supplies has been demanded, and Mn-Zn type ferrite generally used as a transformer material thereof has been demanded. Are required to be inexpensive and have high performance.

In order to produce high-performance ferrite,
It is desirable to use a high-purity raw material containing as few impurities as possible. Particularly, in the iron oxide raw material, about 70% of the whole ferrite is occupied by the weight ratio, so that it is general to use a high-purity raw material.

The characteristics of ferrite greatly depend on the impurities contained therein. Above all, particularly when a large amount of P ₂ O ₅ is contained, remarkable abnormal grain growth is caused, magnetic properties are significantly deteriorated, and it becomes difficult to achieve high performance.

That is, when an iron oxide raw material containing a large amount of P ₂ O ₅ is used, the presence of P ₂ O ₅ causes structural irregularities such as abnormal grain growth in the sintered body structure, resulting in significant hysteresis loss. to degrade. Not only that, P ₂ O ₅ is ubiquitously present in the structure (triple point) as a complex oxide that has reacted with CaO, and CaO in the grain boundary layer decreases, resulting in insufficient formation of the grain boundary layer. Therefore, the electric resistance is lowered, and the eddy current loss is significantly deteriorated.

Therefore, up to now, P ₂ O ₅ and P
Using a commercially available inexpensive iron oxide raw material containing a large amount of impurities such as bO, CuO, and SiO ₂ , high-performance Mn-
Zn ferrite could not be produced and had to use an expensive iron oxide raw material although it had high purity.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the drawbacks of the prior art and to provide a low-cost low-loss oxide magnetic material which has high performance even when an inexpensive iron oxide raw material containing a large amount of impurities is used. It is to provide the manufacturing method.

[0008]

As a result of various studies, the inventors of the present invention have found that even if an inexpensive iron oxide raw material powder containing 0.01 to 0.1 wt% of P ₂ O ₅ is used, In terms of composition, the main components are Fe ₂ O ₃ : 52 to 54 mol% and MnO:
33-37 mol%, ZnO: 9-15 mol%,
As an accessory component, SiO ₂ : 0.005 to 0.025 wt
%, CaO: 0.02~0.10wt%, Cr 2 O 3: 0.
1 to 3.0 wt% is added, and at least one of Ta ₂ O ₅ and Nb ₂ O ₅ is contained in a total amount of 0.08 wt% or less (not including O) to improve performance. It is a finding that can be achieved.

That is, according to the present invention, the main components are 52 to 54.
mol% ferric oxide (Fe ₂ O ₃ ), 33 to 37 mol
% Manganese oxide (MnO), 9 to 15 mol% zinc oxide (ZnO), and 0.005 to 0.
025wt% of silicon dioxide (SiO _2), 0.02~0.
10 wt% calcium oxide (CaO), 0.1-3.0
wt% chromium trioxide (Cr ₂ O ₃ ), 0.007 to 0.0
7 wt% of phosphorus pentoxide (P ₂ O ₅ ) is contained, and at least one of tantalum pentoxide (Ta ₂ O ₅ ) and niobium pentoxide (Nb ₂ O ₅ ) is added in a total amount of 0.08 wt. % Or less (not containing O) is a low loss oxide magnetic material.

The present invention also provides 0.01-0.1 wt% P
Iron oxide raw material containing ₂ O ₅ is used, and the main component composition of the sintered body is 52 to 54 mol% ferric oxide (Fe ₂ O ₃ ), 3
3-37 mol% manganese oxide (MnO), 9-15
Consists of mol% zinc oxide (ZnO), and 0.005-0.025 wt% silicon dioxide (Si
O ₂ ), 0.02 to 0.10 wt% calcium oxide (C
aO), 0.1-3.0 wt% chromium trioxide (Cr
₂ O ₃ ), tantalum pentoxide (Ta ₂ O ₅ ), and niobium pentoxide (Nb ₂ O ₅ ), at least one of which is contained in a total amount of 0.08 wt% or less (not including 0). After mixing the specified raw materials with, mixing, pre-baking and granulating, molding,
A method for producing a low-loss oxide magnetic material, which is characterized by sintering.

Here, in the present invention, F as a main component
52 to 54 mol% of e ₂ O ₃ and 33 to 37 mo of MnO
The reason for setting 1% and ZnO to 9 to 15 mol% is usually
Since the power transformer material is used in an environment of about 60 to 100 ° C., the temperature characteristic of power loss that largely depends on the main component composition needs to be negative in this temperature range. The composition range is most suitable, and
This is because the loss is low.

Further, SiO ₂ is 0.005 to 0.025 wt.
%, CaO is set to 0.02 to 0.10 wt% because if the amount is less than the lower limit, the formation of the grain boundary layer becomes insufficient, the electric resistance decreases, and the eddy current loss deteriorates. On the contrary, in the region where the upper limit is exceeded, it becomes difficult to control the structure and the characteristics deteriorate.

The total amount of Ta ₂ O ₅ and Nb ₂ O ₅ is 0.08 w.
The reason for setting t% or less (excluding O) is 0.08 wt%
This is because it is difficult to control the grain growth and the loss cannot be reduced in a region exceeding the range.

Further, the amount of P ₂ O ₅ contained in iron oxide is set to 0.
The reason why the content is set to 01 to 0.1 wt% is that the raw material of less than 0.01 wt% is expensive and does not meet the purpose of the present invention. Further, in the region where the amount exceeds 0.1 wt%, it becomes difficult to control the structure, and the loss cannot be reduced. At this time, the P ₂ O ₅ content was 0.01 to 0.05 wt%.
It is more preferable to use the raw material contained in the range since the content of other impurities is small and the loss can be relatively easily reduced.

Further, in the present invention, by adding Cr ₂ O ₃ , it becomes extremely easy to control the grain growth, abnormal grain growth does not occur, and a uniform structure is obtained, so that the hysteresis loss is reduced. Is possible. Further, the ease of controlling the structure promotes the formation of the grain boundary layer and facilitates the improvement of the eddy current loss. Further, by adding an appropriate amount of Ta ₂ O ₅ and Nb ₂ O ₅ as a means for improving performance, the electrical resistance of the grain boundary layer is further improved, and eddy current loss can be reduced.

By setting the range of the above subcomponents,
A core loss of 650 kw / m ³ can be obtained, but in order to achieve higher performance, it is desirable to set the range of the accessory component to obtain a core loss of 500 kw / m ³ or less.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to examples.

Example 1 A commercially available iron oxide raw material having a P ₂ O ₅ content of 0.03 wt% was used.
_{52.6Fe 2 O 3 -35.7MnO-11.7ZnO (} m
so as to obtain a mixed powder obtained by mixing the raw material powders of Mn ₃ O ₄ and ZnO with a ball mill to obtain a mixed powder of 950 ° C.
Calcined in the atmosphere for 2 hours. Next, 0.002 to 0.035 wt% of SiO ₂ and CaO were added to the calcined powder.
0.06 wt%, Ta ₂ O ₅ 0.03 wt%, Cr ₂ O ₃
Of 0.5 wt% and SiO ₂ of 0.01 wt%
%, 0.01 to 0.15 wt% of CaO and 0.1% of Ta ₂ O ₅ .
03 wt% and Cr ₂ O ₃ of 0.5 wt% were added, and the mixture was crushed with a ball mill. Further, 0.5 wt% of PVA was added as a binder, dried and granulated with a spray dryer. The obtained granules were pressure-molded into a toroidal shape of φ30 × φ20 × t10 mm and then sintered to obtain a sintered body.

Further, by the same method, with the same main component composition,
A conventional material without adding Cr ₂ O ₃ and Ta ₂ O ₅ was prepared as a comparative sample. Also, at this time, P ₂ O ₅ , SiO ₂ ,
The contents of CaO are 0.02, 0.01 and 0.0, respectively.
It is 6 wt%.

[0020] Figure 1, the amount and relation between core loss (P _CV) amount of the amount of CaO of SiO ₂ when the 0.06 wt% in the case of, also, in Figure 2, the SiO ₂ in the case of The relationship between the addition amount of CaO and the core loss ( _PCV ) when the addition amount is 0.01 wt% is shown.

From FIG. 1, the amount of SiO ₂ added is 0.005
It can be seen that the core loss (P _CV ) is improved in the range of 0.025 wt%. Further, it can be seen from FIG. 2 that the core loss (P _CV ) is improved when the added amount of CaO is in the range of 0.02 to 0.10 wt%.

Example 2 A commercially available iron oxide raw material having a P ₂ O ₅ content of 0.01 to 0.15 wt% was used in the same manner as in Example 1. , With the same main component composition, the contents of SiO ₂ , CaO, Cr ₂ O ₃ and Ta ₂ O ₅ were 0.01, 0.06, 0.5 and 0.03 w, respectively.
A t% powder was made and sintered.

FIG. 3 shows the relationship between the amount of P ₂ O ₅ and P _CV . From FIG. 3, it can be seen that P _CV remarkably increases when the content of P ₂ O ₅ is 0.1 wt% or more.

Example 3 A commercially available iron oxide raw material having a P ₂ O ₅ content of 0.03 wt% was used.
By the same method as in Example 1, Cr ₂ O ₃ having the same main component composition was prepared.
A powder having a content of 0.01 to 4.0 wt% was prepared. At this time, the contents of SiO ₂ , CaO, and Ta ₂ O ₅ are 0.01, 0.06, and 0.05 wt%, respectively. Next, this powder was molded using a mold having the same shape as in Example 1 and was sintered to obtain a sintered body.

FIG. 4 shows the Cr ₂ O ₃ content and P of the obtained sintered body.
The relationship of _CV is shown. From FIG. 4, the amount of Cr ₂ O ₃ is 0.1 to 3.0.
It can be seen that the core loss (P _cv ) is improved in the wt% range.

Example 4 A commercially available iron oxide raw material having a P ₂ O ₅ content of 0.03 wt% was used.
By the same method as in Example 1, Ta ₂ O ₅ having the same main component composition was prepared.
And Nb ₂ O ₅ were added in the range of 0 to 0.10 wt% to prepare a powder. At this time, SiO ₂ , CaO, C
The contents of r ₂ O ₃ were 0.01, 0.06 and 0.5, respectively.
wt%. Next, this powder was molded using a mold having the same shape as in Example 1 and was sintered to obtain a sintered body.

Table 1 shows P _cv values when the amounts of Ta ₂ O ₅ and Nb ₂ O ₅ were changed. The values of the conventional materials are those produced in Example 1.

[0028]

[Table 1]

From Table 1, when the total amount of Ta ₂ O ₅ and Nb ₂ O ₅ is 0.08 wt% or less (not including 0), the core loss (P
You can see that _cv ) has been improved.

[0030]

INDUSTRIAL APPLICABILITY According to the present invention, even if an inexpensive iron oxide raw material which has been rarely used in the past is used, Mn having high performance is obtained.
Since -Zn-based ferrite can be obtained and the cost can be significantly reduced, it is industrially useful.

[Brief description of the drawings]

FIG. 1 Si of Mn—Zn ferrite in Example 1
Diagram showing the relationship between the amount of O ₂ and core loss (P _CV).

FIG. 2 Ca of Mn—Zn ferrite in Example 1
The figure which shows the relationship between O amount and core loss ( _PCV ).

FIG. 3 is a diagram showing the relationship between the amount of P ₂ O ₅ in the iron oxide raw material and the core loss (P _CV ) of Mn—Zn ferrite in Example 2.

FIG. 4 Cr of Mn—Zn ferrite in Example 3
Diagram showing the relationship between the ₂ O ₃ amount and the core loss (P _CV).

Claims (2)

[Claims] 1. 52 to 54 mol% ferric oxide (Fe ₂ O ₃ ), 33 to 37 mol% manganese oxide (MnO), and 9 to 15 mol% zinc oxide (ZnO) as main components.
Of 0.005 to 0.025 wt% silicon dioxide (SiO ₂ ), 0.02 to 0.10 wt% of calcium oxide (CaO), and 0.1 to 3.0 wt% of chromium trioxide (C).
r ₂ O ₃ ), 0.007 to 0.07 wt% phosphorus pentoxide (P
₂ O ₅ ) and at least one of tantalum pentoxide (Ta ₂ O ₅ ) and niobium pentoxide (Nb ₂ O ₅ )
A low loss oxide magnetic material, characterized in that the total content thereof is 0.08 wt% or less (not including O). 2. An iron oxide raw material containing 0.01 to 0.1 wt% P ₂ O ₅ is used, and the main component composition of the sintered body is 52 to 5
4 mol% of ferric oxide (Fe ₂ O _3), 33~37mo
1% manganese oxide (MnO), 9 to 15 mol% zinc oxide (ZnO), and 0.005 as an accessory component.
0.025 wt% silicon dioxide (SiO ₂ ), 0.02-
0.10 wt% calcium oxide (CaO), 0.1-
The total amount of chromium trioxide (Cr ₂ O ₃ ) of 3.0 wt%, tantalum pentoxide (Ta ₂ O ₅ ), and niobium pentoxide (Nb ₂ O ₅ ) was 0.08 wt% in total. A method for producing a low-loss oxide magnetic material, which comprises blending, mixing, pre-calcining, granulating, shaping, and sintering a predetermined raw material so as to contain the following (not including 0).