JPH08236335A - Low-loss oxide magnetic material - Google Patents

Abstract

PURPOSE: To reduce the power loss of an oxide magnetic material and suppress its heat generation even in the high-frequency band of about 100kHz to about 1MHz, by making an Mn-Zn based ferrite contain an auxiliary component MgO of a specific wt.%, and further, by dissolving this MgO in a spinel crystal particles in the range of a specific ratio to a total MgO content. CONSTITUTION: The raw material powders of high-purity Fe2 O3 , Mn3 O4 and ZnO are weighed, mixed with each other and calcined. To the calcined powder, 0.02wt.% of SiO2 . 0.04wt.% of CaO and 0.3wt.% of MgO are added, and further, to the obtained powder, six kinds of auxiliary components are added by a predetermined combination, and then, these materials are mixed with each other to be crashed. After the obtained powder is mixed with a binder to be granulated, the granulated powder is molded to be burned. An MgO amount in a spinel phase crystal grain is represented by the weight ratio to an total MgO content, removing its grain boundary phase through a chemical etching. A low Pcv value is obtained in the range of this weight ratio having the value of 70-95%. In this manner, an oxide magnetic material having excellent performances as a low-loss transformer material for powder wupplies is obtained in 100kHz-1MHz.

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 more particularly to a spinel type Mn-Zn type ferrite used for a power transformer material or the like.

[0002]

2. Description of the Related Art Conventionally, a power transformer material has been used at a driving frequency of about 200 kHz or less. However, in recent years, the progress of high performance and miniaturization of various electronic devices has been remarkable, and accordingly, further high performance and miniaturization of transformer materials for power supplies have been demanded. Therefore, it is desired to further reduce the loss of the main transformer, the smooth choke, or the like, or the Mn-Zn-based ferrite used for the power transformer material. In addition, in order to reduce the size and weight of electronic devices, a study on increasing the driving frequency is remarkable in various fields, and a power supply of about 1 MHz is being commercialized.

However, when the conventional Mn-Zn type ferrite is used at a high frequency such as 1 MHz, there is a drawback that heat generation due to power loss of the ferrite is significant and the function cannot be effectively performed.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in order to meet the demand for low loss of Mn-Zn type ferrite for use in the entire range from low frequency to high frequency.
It is an object of the present invention to provide a low-loss oxide magnetic material that eliminates the above-mentioned drawbacks of the prior art and has a small power loss even in a high frequency band of about 100 KHz to about 1 MHz and effectively suppresses heat generation.

[0005]

Generally, MgO is said to substitute for the main component to form a solid solution in the spinel crystal grains. However, in the prior art, there is no clear limitation on the amount of solid solution. , Not yet done. Therefore, as a result of various studies, the present inventor solved the above-mentioned problem by concentrating MgO, which is a subcomponent, inside the crystal grains as well as at the crystal grain boundaries at a specific ratio, thereby further reducing the loss. Low Mn-
It has been found that a Zn-based ferrite can be obtained.

That is, MgO is added to the total MgO content of 70-9.
By making a solid solution in the spinel crystal particles in the range of 5%, the core loss characteristics can be improved and the performance of the power transformer material can be improved.

That is, in the present invention, the main component is 30 to 4
2 mol% manganese oxide (MnO), 4 to 19 mol
% Zinc oxide (ZnO), and the balance ferric oxide (Fe
₂ O ₃ ), and 0.1 wt% or less (not including 0) of silicon oxide (SiO ₂ ) as the first subcomponent, 0.15 wt.
% Or less (not including 0) calcium oxide (CaO), and 0.2 wt% or less (not including 0) vanadium pentoxide (V ₂ O ₅ ), 0.2 wt% as a second subcomponent. the following tantalum oxide (not including _{0) (Ta 2 O 5),} 0.1w
t% or less (not including 0) niobium oxide (Nb ₂ O ₅ ),
Hafnium oxide (H) of 0.4 wt% or less (not including 0)
fO ₂ ), 0.4 wt% or less (not including 0) titanium oxide (TiO ₂ ), and 0.4 wt% or less (not including 0) tin oxide (SnO ₂ ) at least one or more. The low loss oxide magnetic material further contains 0.2 wt% or less (not including 0) of magnesium oxide (MgO) as a third subcomponent, and the total MgO content is 70% or less.
It is a low loss oxide magnetic material characterized by being dissolved in spinel crystal grains in the range of up to 95 wt%.

[0008]

In the present invention, the power loss characteristic was improved by dissolving MgO, which is a sub-component, in the spinel phase crystal grains in a specific ratio so that the temperature rise temperature of sintering was 700 ° C or more. At the temperature of 1 vol% to the atmosphere (Ai
By adjusting the oxygen partial pressure in the range up to r) and controlling the oxygen partial pressure according to each cooling rate of 50 to 1000 ° C./Hr in the cooling unit, the inside of the crystal grains and the crystal grain boundaries are controlled. It is possible to concentrate MgO even in the following, and as a result, both the specific resistance of the grain boundary phase and the spinel phase crystal are improved,
This is probably because the eddy current loss decreased.

In the present invention, the solid solution amount of MgO in the spinel phase crystal particles is set to 70 to 95 wt% of the total content of MgO, in the case where more than 95 wt% of MgO is dissolved in the crystal particles. This is because the formation of the grain boundary phase becomes insufficient, the specific resistance of the grain boundary phase significantly decreases, both hysteresis loss and eddy current loss increase, and the power loss deteriorates.
When MgO is dissolved in the crystal grains in an amount of less than 70 wt%, the influence of magnetic strain caused by the difference in composition and oxidation degree between the grain boundary phase and the spinel phase crystal grains, and
This is because not only the power loss characteristic but also the magnetic permeability is deteriorated due to the reduction of the specific resistance in the crystal particles.

Further, in the present invention, as an accessory component,
V ₂ O ₅ of 0.2 wt% or less, Ta of 0.2 wt% or less
_{At least one of 2} O ₅ , 0.1 wt% or less of Nb ₂ O ₅ , 0.4 wt% or less of HfO ₂ , 0.4 wt% or less of TiO ₂ , and 0.4 wt% or less of SnO ₂ is added. Therefore, the power loss can be further improved. However, when the amount exceeds the above-mentioned addition amount, the crystal grain size becomes non-uniform due to abnormal grain growth, etc., the specific resistance is remarkably lowered, the hysteresis loss and the eddy current loss are both increased, and the power loss is increased. To increase.

[0011]

EXAMPLES Examples of the low loss oxide magnetic material according to the present invention will be described below.

(Example 1) High purity Fe ₂ O ₃ and Mn
The raw material powder of ₃ O ₄ and ZnO was mixed with 53.2 mol% of Fe ₂ O.
₃ , 36.8 mol% MnO, 10.0 mol% Zn
The powder was weighed so as to be O, and these powders were mixed by a ball mill and then calcined at 950 ° C.

Next, 0.02 wt% of S was added to the calcined powder.
iO ₂ , 0.04 wt% CaO, and 0.3 wt% or less MgO are added, and further six kinds of subcomponents, that is, 0.02%.
3 wt% or less of V ₂ O ₅ , 0.3 wt% or less of Ta ₂ O ₅ ,
Nb ₂ O ₅ of 0.2 wt% or less, HfO of 0.5 wt% or less
₂ , 0.5 wt% or less TiO ₂ , 0.5 wt% or less Sn
O ₂ was added in a predetermined combination, and further mixed and crushed with a ball mill.

As comparative samples, Fe ₂ O ₃ , MnO,
The composition of ZnO, SnO ₂ , and CaO is the same as above, and only the above 6 kinds of subcomponents are added in a predetermined combination,
A mixed and crushed powder was also prepared.

A binder is mixed with these obtained powders and granulated, and then molded at ² ton / cm ² , and these molded bodies are fired at a temperature of 1200 to 1400 ° C. and an oxygen partial pressure of 1 to 1.
Firing was performed under the conditions of 0 vol% and a cooling rate of 50 to 1000 ° C./Hr.

Table 1 shows, for each sample, the most excellent power loss (hereinafter referred to as Pcv) at a frequency of 100 kHz, a magnetic flux density of 2000 G, and a temperature of 100 ° C. while changing the firing conditions. .

[0017]

[Table 1]

The MgO content in the spinel phase crystal particles in Table 1 is the ratio (w) of the content in the spinel phase crystal particles from which the grain boundary phase is removed by chemical etching to the total content.
t%). In addition, in Table 1, only the samples within the scope of the present invention are shown.

From Table 1, it can be seen that the sample of the present invention has a significantly lower Pcv value than the comparative sample.

Example 2 High-purity Fe ₂ O ₃ and Mn
Raw material powder of ₃ O ₄ and ZnO was added to 53.2 mol% of Fe ₂ O.
₃ , 36.8 mol% MnO, 10.0 mol% Zn
The powder was weighed so as to be O, and these powders were mixed by a ball mill and then calcined at 950 ° C.

Next, 0.02 wt% of S was added to the calcined powder.
iO ₂ , 0.05 wt% CaO, and 0.03 wt% Nb ₂ O ₅ and 0 to 0.3 wt% MgO were added,
Further, they were mixed and crushed with a ball mill.

Next, the obtained powder is mixed with a binder and granulated, and then molded at ² ton / cm ² , and these molded bodies are fired at a temperature of 1200 to 1400 ° C. and an oxygen partial pressure of 1 to 10.
It was fired under the conditions of vol% and a cooling rate of 10 to 1000 ° C./Hr.

FIG. 1 shows the Pcv of each sample obtained when the MgO content was changed at 100 kHz, 2000 G, and 100 ° C., and the initial magnetic permeability at 100 kHz and room temperature (hereinafter referred to as μi). ) Is a graph showing the value of), and shows the amount of MgO in the spinel phase crystal particles from which the lowest Pcv value was obtained for each sample. The numerical values near the plot points in the graph indicate the amount of MgO in the spinel phase crystal particles in the total MgO content.

From FIG. 1, the content of MgO is 0 to 0.20.
It can be seen that excellent magnetic properties are obtained at wt% (excluding 0 wt%).

(Example 3) High-purity Fe ₂ O ₃ and Mn
The raw material powder of ₃ O ₄ and ZnO was mixed with 53.2 mol% of Fe ₂ O.
₃ , 36.8 mol% MnO, 10.0 mol% Zn
The powder was weighed so as to be O, and these powders were mixed by a ball mill and then calcined at 950 ° C.

Next, 0.02 wt% of S was added to the calcined powder.
iO ₂ , 0.05 wt% CaO, 0.1 wt% Ti
O ₂ and 0.03 wt% of MgO were added, and further mixed and crushed by a ball mill.

Next, the obtained powder is mixed with a binder and granulated and then molded at ² ton / cm ² , and these molded bodies are fired at a temperature of 1200 to 1400 ° C. and an oxygen partial pressure of 1 to 10.
It was fired under the conditions of vol% and cooling rate of 50 to 1000 ° C./Hr.

FIG. 2 shows 100 kHz of each sample obtained when the MgO content in the spinel phase crystal grains was changed,
2000g, Pcv at 100 ° C, and 100k
It shows the μi value under the conditions of Hz and room temperature.

The amount of MgO in the spinel phase crystal particles of FIG. 2 is a value which indicates the content in the spinel phase crystal particles from which the grain boundary phase has been removed by chemical etching, as a ratio (%) to the total content. is there.

From FIG. 2, the total content of MgO is 70 to 95.
It can be seen that the sample in which MgO is solid-solved in the spinel phase crystal particles has a low Pcv value in the range of%.

Example 4 High-purity Fe ₂ O ₃ and Mn
The raw material powder of ₃ O ₄ and ZnO was replaced with 53 mol% of Fe ₂ O ₃ ,
After weighing so as to have 39 mol% MnO and 8 mol% ZnO and mixing these powders with a ball mill,
It was calcined at 800 ° C.

Next, 0.03 wt% of S was added to the calcined powder.
iO ₂ , 0.10 wt% CaO, 0.20 wt% Hf
O ₂ and 0.02 wt% of MgO were added, and further mixed and crushed by a ball mill.

Next, the obtained powder is mixed with a binder and granulated, and then molded at ² ton / cm ² , and these molded bodies are fired at a temperature of 1200 to 1400 ° C. and an oxygen partial pressure of 3 vol.
% Or less, and the firing rate was 50 to 1000 ° C./Hr.

FIG. 3 is a graph of 50 MHz at 1 MHz of each sample obtained when the MgO content in the spinel phase crystal grains was changed.
The value of Pcv under the conditions of 0 G and 60 ° C. is shown.

The amount of MgO in the spinel phase crystal particles of FIG. 3 is a value which shows the content in the spinel phase crystal particles from which the grain boundary phase has been removed by chemical etching as a ratio (%) to the total content. is there.

From FIG. 3, 70 to 95% of the total MgO content
It is understood that, in the range of 1, the sample in which MgO is dissolved in the spinel phase crystal particles has a low Pcv value.

[0037]

As described above, according to the present invention, 10
At 0 kHz to 1 MHz, it was possible to obtain an oxide magnetic material having a lower loss than conventional and exhibiting excellent performance as a power transformer material.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between MgO content and Pcv and μi. FIG. 1A is a diagram showing the relationship between the MgO content and μi. FIG. 1B is a diagram showing the relationship between the MgO content and Pcv.

FIG. 2 is a diagram showing the relationship between the amount of MgO in spinel phase crystal particles and Pcv and μi. FIG. 2A is a diagram showing the relationship between the amount of MgO in the spinel phase crystal particles and μi. FIG. 2B is a diagram showing the relationship between the MgO amount in the spinel phase crystal particles and Pcv.

FIG. 3 is a diagram showing the relationship between the amount of MgO in spinel phase crystal particles and Pcv.

Claims (1)

[Claims] 1. A main component comprising 30 to 42 mol% of manganese oxide (MnO), 4 to 19 mol% of zinc oxide (ZnO), and the balance of ferric oxide (Fe ₂ O ₃ ). As a sub-component, 0.1 wt% or less (not including 0) silicon oxide (SiO ₂ ), 0.15 wt% or less (not including 0) calcium oxide (CaO), and further as a second sub-component, Vanadium pentoxide (V ₂ O ₅ ) of 0.2 wt% or less (not including 0), tantalum oxide (Ta ₂ O ₅ ) of 0.2 wt% or less (not including 0), 0.1 wt% or less (0 Niobium oxide (Nb ₂ O ₅ ), 0.4 wt.
% Or less (not including 0) hafnium oxide (HfO ₂ ),
Titanium oxide (Ti not exceeding 0.4 wt%)
O ₂ ), 0.4 wt% or less (not including 0) tin oxide (Sn)
O ₂ ), in a low-loss oxide magnetic material containing at least one or more of
Magnesium oxide (MgO) of 0.2 wt% or less (not including 0) is contained, and the total content of MgO is 70 to 70%.
A low loss oxide magnetic material characterized by being solid-solved in spinel crystal grains in the range of 95 wt%.