JP2000299215A - Low loss oxide magnetic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable reducing magnetic loss by specifying the composition amount of Fe2O3, NiO, CuO and ZnO which are main component and SiO2 or MnO which are admixture to the main component. SOLUTION: As main component composition, 43-50 mol% of Fe2O3, 10-40 mol% of NiO, 1-15 mol% of CuO and residual ZnO are used, and at least one kind out of 0.005-0.1 wt.% of SiO2 and 0.005-0.5 wt.% of MnO is added as admixture, thereby obtaining low loss oxide magnetic material. The mean crystal grain diameter of a baked member is set at least 5 μm, and the ratio of pores in crystal grains to the whole pores is set as 5-60%, so that oxide magnetic material of lower loss can be obtained. Since resistivity is remarkably high, direct winding of a coil is enabled, and a jig for winding like a bobbin is unnecessary. Since the resistivity is high, collective baking with magnetic material is possible, and microminiaturization is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oxide magnetic material, and more particularly to a low-loss oxide magnetic material suitable for a ferrite core used in a power transformer.

[0002]

2. Description of the Related Art Conventionally, as a transformer material for a power source, Mn having a relatively high saturation magnetic flux density and a small power loss has been mainly used.
-Zn-based ferrite is used. However, Mn-
Zn-based ferrite has a DC specific resistance of 10 to 10 ³ Ωcm.
And low. Therefore, when winding is performed on a magnetic core using Mn-Zn-based ferrite, winding is performed on the magnetic core through a jig such as a bobbin in order to eliminate problems such as a short circuit between the magnetic core and the winding. I was For this reason, this is an obstacle to miniaturization, weight reduction, and cost reduction of the transformer or the choke coil.

[0003] In recent years, miniaturization of electronic devices such as portable devices has been rapidly advancing. And the power supply used for them also tends to be downsized. Transformers occupy a large part of the power supply in terms of both volume and power loss, so that their size and efficiency have been demanded.
Therefore, a magnetic core using a Ni—Zn-based ferrite that has a high DC specific resistance and does not require a bobbin when winding is used. Ni—Zn-based ferrite has a high specific resistance, and can be wound directly. In addition to the high specific resistance and the low temperature firing by the addition of Cu, the conductor and the magnetic material can be integrally fired, and an unlimited size reduction can be realized.

[0004]

However, the above-mentioned Ni-
Zn-based ferrite has the following disadvantages. That is, in general, there is a problem that the magnetic loss is significantly larger than that of the Mn-Zn ferrite.

[0005] The magnetic loss of ferrite is composed of hysteresis loss, eddy current loss, and residual loss. In particular, N
i-Zn ferrite generally has a DC specific resistance of 10
^As high as ⁶ to 10 ¹⁰ Ωcm, the eddy current loss is negligibly small.

The hysteresis loss is a loss caused by irreversible movement of the domain wall. In order to reduce the hysteresis loss, it is necessary to reduce pores or inclusions that hinder domain wall movement. However, if the inclusions are reduced too much, the domain wall will travel a long distance, and conversely increase the hysteresis loss. Further, the number of domain walls depends on the average crystal grain size. Therefore, it is desirable that the crystal grain size is large. As described above, in order to reduce the hysteresis loss, it is desirable that the average crystal grain size is large and that the crystal grains have pores or inclusions that hinder the domain wall movement.

Accordingly, the present invention provides a method of adding at least one of SiO ₂ and MnO to a Ni—Zn ferrite,
It is an object of the present invention to provide an oxide magnetic material having a large average crystal grain size and having pores in crystal grains to reduce magnetic loss.

[0008]

According to the present invention, ferrite having a small magnetic loss within a driving frequency, a large specific resistance, and a large average crystal grain size can be obtained.

That is, according to the present invention, the main component composition is 43 to 50.
mol% Fe2O3, 10-40 mol% NiO, 1
It consists of 15 mol% CuO and the balance ZnO, and has an additive of 0.005 to 0.1 wt% SiO2 or 0.00.
A low-loss oxide magnetic material containing at least one of 5-0.5 wt% MnO.

The main component composition is 43 to 50 mol% Fe2O.
3, 10 to 40 mol% NiO, 1 to 15 mol% Cu
O and the balance being ZnO are as follows: Fe ₂ O ₃ is 43 mol%
Or less, or 40 mol% or more of NiO, or C
When uO is 15 mol% or more, the loss at room temperature is significantly deteriorated. When Fe ₂ O ₃ is 50 mol% or more, the specific resistance is remarkably reduced due to generation of Fe ²⁺ , and NiO is 10 mol% or less. This is because the Curie temperature and the maximum magnetic flux density are low, and the reliability as a power supply material is inferior. If CuO is 1 mol% or less, firing at a low temperature cannot be performed, and
^{This is because} the generation of ²⁺ significantly lowers the specific resistance. The reason why at least one kind of additive is 0.005 to 0.1 wt% SiO ₂ or 0.005 to 0.5 wt% MnO is that SiO ₂ is 0.005 wt% or less and MnO is 0.005 wt%. % Or less, the hysteresis loss increases to cause deterioration of the loss.
iO ₂ is 0.1 wt% or more, and MnO is 0.5 wt%
This is because the density becomes low when the percentage is set to%.

Further, the present invention provides the low-loss oxide magnetic material, wherein the sintered body has an average crystal grain size of 5 μm or more, and the ratio of pores in the crystal grains to all pores is 5 to 60%.
Is a low-loss oxide magnetic material.

The reason why the average crystal grain size of the fired body is 5 μm or more is that if the average crystal grain size of the fired body is 5 μm or less, the loss is deteriorated due to an increase in hysteresis loss.

The ratio of pores in crystal grains to all pores is 5
The reason why it is set to ６０60% is that if the proportion of the pores in the crystal grains to all the pores is 5% or less, or 60% or more, the hysteresis loss increases.

The present invention also relates to the above low-loss oxide magnetic material, wherein the temperature at which the power loss is minimized is 120 ° C. or higher.

[0015] The present invention also relates to the low-loss oxide magnetic material described above, wherein the pre-baking temperature is 500 to 750 ° C.

The reason why the pre-baking temperature is set to 500 to 750 ° C. or lower is that if the pre-baking temperature is 500 ° C. or lower, the loss at room temperature is significantly deteriorated. The exact cause is unknown. When the pre-baking temperature is 750 ° C. or higher, not only the loss increases particularly at a high temperature of 80 ° C. or higher, but also the temperature at which the loss is minimized is 120 ° C. or lower.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

Table 1 shows various characteristics of the first embodiment of the present invention when the additive composition is kept constant and the main component composition is changed.

[0019]

[Table 1]

Fe ₂ O ₃ , NiO, ZnO, CuO, S
iO ₂ and MnO were weighed to have the composition shown in Table 1, and mixed for 2 hours using an attritor. After mixing
Granulated with a spray dryer. The granulated powder was calcined in a rotary kiln. The obtained powder was crushed using an attritor. After crushing, the mixture was granulated by a spray dryer, pressed into a toroidal shape, and baked at a sintering temperature of 1150 ° C. to produce an invention product and a comparative product.

As a conventional product, the main component composition is 49 mol%
Ni—Zn ferrite composed of Fe ₂ O ₃ , 25 mol% NiO and the balance ZnO was weighed and mixed for 2 hours using an attritor. After mixing, the mixture was granulated with a spray dryer. The granulated powder was calcined in a rotary kiln. The obtained powder was crushed using an attritor. After crushing,
It was granulated by a spray dryer, pressed into a toroidal shape, and fired at a firing temperature of 1250 ° C.

Table 1 shows the ratio of the pores in the crystal grains to the total pores of the invention product, the comparison product, and the conventional product when the main component composition was changed, the average crystal grain size, the specific resistance, and 50 kHz-15.
0mT-RT, 50kHz-150mT-80 ° C, 5
The loss at 0 kHz-150 mT-120 ° C is shown. The main component composition is 43 to 50 mol% Fe ₂ O ₃ , 10 to 40 mo
1% NiO, 1 to 15 mol% CuO, balance ZnO
It can be seen that the specific resistance is high and the loss is small in the range.

Table 2 shows various characteristics when the addition amounts of SiO ₂ and MnO are changed while the main component composition is kept constant according to the second embodiment of the present invention.

[0024]

[Table 2]

Fe ₂ O ₃ , NiO, ZnO, CuO, S
iO ₂ and MnO were weighed to have the composition shown in Table 2, and
The invention product and the comparison product were produced under the same conditions as those of the embodiment.

Table 2 shows the ratio of pores in the crystal grains to the total pores of the invention product, the comparison product, and the conventional product when the amounts of SiO2 and MnO were changed, the average crystal grain size, the specific resistance, and 50 kHz.
z-150mT-RT, 50kHz-150mT-8
0 ° C., 50 kHz-150 mT-120 ° C. loss. 0.005 to 0.1 wt% of SiO ₂ , or
It can be seen that the invention containing at least one of 005 to 0.5 wt% MnO has a high specific resistance and a small loss.

Table 3 shows various characteristics when the ratio of the pores in the crystal grains to the total pores is changed by changing the firing temperature according to the third embodiment of the present invention.

[0028]

[Table 3]

Fe ₂ O ₃ , NiO, ZnO, CuO, S
iO ₂ and MnO were weighed to have the composition shown in Table 3, and
The invention product and the comparison product were produced under the same conditions as those of the embodiment.

Table 3 shows the ratio of the pores in the crystal grains to the total pores of the invention product, the comparison product, and the conventional product when the average crystal grain size was changed, the average crystal grain size, the specific resistance, and 50 kHz-1.
50mT-RT, 50kHz-150mT-80 ° C,
The loss at 50 kHz-150 mT-120C is shown. It can be seen that invention products having an average crystal grain size of 5 μm or more have high specific resistance and small loss.

Table 4 shows various characteristics when the pre-baking temperature is changed according to the fourth embodiment of the present invention.

[0032]

[Table 4]

The main component composition is 49.5 mol% Fe
₂ O ₃ , 15 mol% NiO, 5 mol% CuO and the balance ZnO were weighed and mixed using an attritor for 2 hours. After mixing, the mixture was granulated with a spray dryer.
The granulated powder was pre-fired at 500 to 750 ° C in a rotary kiln. The obtained powder was crushed using an attritor. After crushing, the mixture was granulated by a spray dryer, pressed into a toroidal shape, and fired at a firing temperature of 1150 ° C.

Table 4 shows the average grain size, specific resistance, and 50 kHz of the invention product and the comparison product when the pre-baking temperature was changed.
-150mT-RT, 50kHz-150mT-80
° C, 50 kHz-150 mT-140 ° C loss.
It is understood that the specific resistance is high and the loss is small when the pre-baking temperature is in the range of 500 to 750 ° C.

FIG. 1 shows the temperature characteristics of the loss of 50 kHz-150 mT between the invention product 4 according to the first embodiment of the present invention and the conventional product. Inventive product 4 has a smaller loss over the entire temperature range and a temperature at which the power loss is minimized is 120, compared to the conventional product.
It turns out that it is more than ° C.

FIG. 2 shows 50 kHz of invention products 25, 27, 4 and comparison product 13 according to the fourth embodiment of the present invention.
4 shows the temperature characteristics of a loss of −150 mT. Pre-baking temperature is 50
It can be seen that in the sample at 0 to 700 ° C., the loss is small over the entire temperature range and the temperature at which the power loss is minimized is 120 ° C. or higher.

[0037]

As described above, according to the present invention,
43-50 mol% Fe ₂ O ₃ , 10
-40 mol% NiO, 1-15 mol% CuO, balance ZnO, 0.0005-0.1 wt% as additive
SiO ₂ or 0.005 to 0.5 wt% MnO
In the low-loss oxide magnetic material containing at least one of the following, the average crystal grain size of the fired body is 5 μm or more, and the ratio of the pores in the crystal grains to all the pores is 5 to 60%, so that the low loss An oxide magnetic material is obtained.

According to the present invention, the conventional Mn-Zn
Since the specific resistance is remarkably higher than that of ferrite, it is possible to directly wind a winding, and a winding magnet such as a bobbin is not required, and cost reduction can be expected. In addition, since the specific resistance is high, it is possible to integrally sinter with the magnetic material, and it is possible to miniaturize.

Further, according to the present invention, Fe ₂ O ₃ , Ni
In the method for producing Ni—Zn—Cu ferrite containing O, ZnO, and CuO as main components, the pre-baking temperature is set to 500 to 75.
By setting the temperature to 0 ° C., a low-loss low-loss oxide magnetic material can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing temperature characteristics of a loss of 50 kHz-150 mT between an invention product 4 according to a first embodiment of the present invention and a conventional product.

FIG. 2 shows an invented product 25 according to a fourth embodiment of the present invention;
The figure which shows the temperature characteristic of loss of 50kHz-150mT of 27,4, and the comparative product 13.

Claims (4)

[Claims] 1. A composition comprising a main component of 43 to 50 mol% Fe2
O3, 10 to 40 mol% NiO, 1 to 15 mol% C
uO, with the balance being ZnO, with an additive of 0.005 to
0.1 wt% SiO2, or 0.005 to 0.5 wt
% MnO. A low-loss oxide magnetic material comprising at least one of MnO. 2. The low-loss oxide magnetic material according to claim 1, wherein an average crystal grain size of the fired body is 5 μm or more, and a ratio of pores in crystal grains to all pores is 5 to 60%. Characterized low-loss oxide magnetic material. 3. The low-loss oxide magnetic material according to claim 1, wherein the temperature at which the power loss is minimized is 120 ° C.
A low-loss oxide magnetic material characterized by the above. 4. The low-loss oxide magnetic material according to claim 1, wherein the pre-baking temperature is 500 to 750.
A low-loss oxide magnetic material having a temperature of ° C.