JPH04177807A - Ferromagnetic material low-loss manganese-zinc ferrite - Google Patents

Abstract

PURPOSE:To make it possible to obtain a ferrite for low-loss power use, which is stable in quality, by a method wherein the optimum range of an ion distribution, in particular the relation between divalent FE and trivalent Mn, is specified and a trace additional amount is used in combination. CONSTITUTION:In an Mn-Zn ferrite core, relations shown by formula I are satisfied. In the formula I, Z shows an additional element in a small quantity, Vc shows a cation hole and (x) shows [2(alpha-beta-gamma)+delta]/[2alpha+beta+gamma+delta]. Provided that, alpha, beta, gamma and delta are used on the conditions of 51<=alpha<=55, 33<=beta<=40, 7<=gamma<=14 and 0<=delta<=2 and the alpha, beta, gamma and delta are mol% of compounding raw materials, Fe2O3, MnO and ZnO, and the other trace additional element. Thereby, the power loss of the ferrite core is improved and a low-power loss magnetic material consisting of the Mn-Zn ferrite core, which is high in reliability even under a high frequency and a high load, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to Mn--Zn ferrite having low power loss characteristics required for transformer core materials for switching power supplies, display monitor power supplies, and the like.

(Prior art) Regarding Mn-Zn ferrite having low power loss characteristics, its composition is 50 to 56 mo1% Fe2O3,
MnO 30-4011o1%, ZnO 5-20
The main component is mo1%, and various additives such as CaO1SiO2 are used as subcomponents.

However, in recent years, with the miniaturization and higher frequency of power supplies, there is a need for transformer core materials with even lower power loss characteristics than conventional ones, and conventional Mn-Zn ferrite materials have
Under such conditions, there are serious problems such as increased power loss, unusability, or decreased reliability due to heat generation.

The distribution of ions in ferrite after firing has an important meaning in reducing power loss. In particular, the content of divalent Fe ions is directly related to magnetocrystalline anisotropy, magnetostriction, or resistivity, and is the factor that has the greatest influence on power loss.

However, conventional technical disclosures for general Mn-Zn ferrite only specify the ratio of blended raw materials or firing atmosphere, and do not specifically explain how to adjust the ion distribution for blended raw materials. There was no clear indication of what to do.

(Problems to be Solved by the Invention) In order to solve the above problems, the present invention provides a low power loss magnetic material made of Mn-Zn ferrite that has improved power loss and is highly reliable even under high frequencies and high loads. The purpose is to

(Means for solving problems) The present invention is characterized in that it satisfies the following relationship.

Z n :”M n b” M n , 3+ F e a
"F e :" Z r V cgO4-...(1) 0.004≦x-d+c≦0.03 ・(
2) X depends only on composition. In other words, it is a variable determined only by the blending ratio of raw materials, and is
γ)+δ)/(2α+β+γ16)...(3) It is given by the following relational expression. Here, α, β5, γ, and δ1 respectively mean mol% of Fe, OMnO, ZnO, and a trace amount of added 2 3 ” element.

Furthermore, the above relationship is valid when 51≦α≦55. 33≦β≦40°7≦α≦13.
0<δ≦2 (4).

In addition, in order to satisfy the spinel structure, in a form that includes atomic vacancies, the cation sites are a, ten, c, and d in the molecular formula.
+e10f-3-(5) is satisfied.

What is important here is the relationship expressed by formula (2), which is characterized by setting the relationship between the variables C and d in the molecular formula within a certain range with respect to the variable X determined by a given composition.

M(d-c) in the molecular formula is the active divalent Fe in the material.
It can be called an ion. In other words, in fact, the bivalent F
It can be said that e and trivalent Mn are in an equilibrium relationship with 3/i Fe and divalent Mn, or (d-c) corresponds to the amount of divalent Fe when trivalent ~1n does not exist. .

If x-d is less than 14, for example, Zn evaporates from the grain boundaries during firing and stress is generated near the grain boundaries, deteriorating the magnetic properties. If it exceeds 0.03, for example, a second phase other than the spinel phase will precipitate, which is also undesirable because there is a problem that the magnetic properties will deteriorate.

In addition to the above, magnetic permeability is generally higher as x-d+c is lower, and eddy current loss is lower as x-d+c is higher.
There is an optimal range of x-d ten c.

Furthermore, in molecular formula (1), in addition to the above relationship,
Even better loss characteristics can be obtained if the variables a, b, c, d, and e satisfy the following relationship.

0.14≦a≦0.27 0.63≦b+c≦0.77 2.01≦d+e≦2.15 ・(
8) These component ranges are determined by the magnetocrystalline anisotropy of the material,
This is a range that is effective for low-loss materials with low magnetostriction, etc., but even in this range, even better low-loss characteristics can be obtained by satisfying the relational expression (2) above. confirmed. Zn range a1 or M mouth range b+c
The reason why the range is wider than that of Fe is that the component range differs depending on whether only low loss is given priority or whether both low loss and high saturation magnetic flux density are satisfied.

Now, for loss in the high frequency range, high resistance that can reduce eddy current loss is effective, but the above (2) and (6)
In addition to the relationship in the formula, S of p@amount% that satisfies the condition of the following formula
By adding I 2 O 2 and 8% by weight of CaO, a resistance layer is formed at the grain boundaries and the loss is greatly reduced.

0, O1≦p≦003. 0.02≦a≦0.1...(
A) It is important that these elements exist simultaneously; if both are less than the above range, no improvement in loss will be observed, and if too much, loss will be significantly worsened due to abnormal grain growth.

Furthermore, in order to improve resistance, when TiO□ and V2O, which increase intragranular resistance and grain boundary resistance, are added to the above conditions in the following range and r and S are added in weight %, the eddy current loss is also significantly reduced. It was confirmed that the effect of

0.1≦r≦0.8. 0005≦s≦0.1 In this case, the addition of T1 generally increases by 1 mol of divalent Fe ions for 1 mol of Ti addition from the viewpoint of ion charge balance. In the case, the relational expression as shown in the above equation (1) is
It is important to satisfy the Fe ion of i. In other words, the relationship in equation (1) can be said to be a condition that should be satisfied regardless of the presence or absence of additives.

Since V2O has a low melting point, the grain boundary layer turns into a liquid phase during high-temperature firing, thereby forming a uniform resistance layer at the grain boundaries.

Next, a method for controlling d and C within the composition range of the present invention will be explained.

First, ranges of α, β, γ, δ, etc. that are effective for achieving desired magnetic characteristics such as saturation magnetic flux density, magnetic permeability, etc. are determined. In other words, the optimal ranges of α, β2, γ, and δ are selected depending on whether among the low-loss materials, emphasis is placed on saturation magnetic flux density or magnetic permeability.

This determines the value of X. In order to control C and d when the value of However, it is more desirable to use the value of X based on the immediately preceding analysis result of each raw material powder corresponding to the firing loft. x-d+c increases when firing is performed in an oxygen-enriched atmosphere, and also increases when firing is performed at a low temperature.

(Example) Example 1 In the component system shown in Table 1, a power loss curve was measured using x-d+c as an index.

Table 1 B 53.333.713.02006000.08B
C53,435,01L61003000.088x-
In calculating d+c, d-c was obtained by changing the blended raw materials shown in Table 1 at a firing temperature of 1250° C. for a holding time of 4 hours, and by changing the oxygen concentration in the firing atmosphere from 0.6% to 4.8% depending on the firing conditions. The values of c and d of the fired ferrite core were measured by wet chemical analysis.

In this case, the value of the wet chemical analysis is directly d−c, that is, 3
Effective divalent FQ excluding the amount oxidized by valent Ml
I think so.

As shown in FIG. 1, by using x-d+c as an index, it is possible to represent the lowest power loss region of each of samples A, B, and C. The best range is 0.
It is expressed as 004≦x−d+c≦0.030.

Example 2 In the component range of the three samples of Example 1, changes in power loss were measured by changing the amounts of S 1 02 and Ca 2 O, which are trace additives. The firing conditions are 1250
℃ for 4 hours 17, the oxygen concentration in the atmosphere was controlled to around 1.5%, and the value of x-d+c was o, ot.

It was fired to look like this.

As a result, the power loss value is 100kHz, 20h
A characteristic of 450 to 50 OIIIW/- was obtained at T.

In SiO2, O, C11≦p≦ in weight%
If the value of x- No clear difference could be found when d+c was used as an index.

Specifically, S102 is 50ppln on the low addition side and 350ppc on the high addition side, and for CaO, it is 100ppffl on the low addition side and 1200ppm on the high addition side.
I conducted an experiment.

For samples on the high doping side, the power loss was 100% when measured at 1ookHz and 200+nT in all cases.
It exceeded 0IllW/-, and microscopic observation confirmed that giant grains had grown.

Example 3 In the composition range of the three samples of Example 1, TiO and V2O were added as trace additives under the same firing conditions as Example 2.
5 was added. Power loss is 150p with addition of V2O5
When pI is fixed at 11 and x-d+c is around 0.010, as shown in Fig. 2, at a weight of 96, 0.1
≦“Good results were obtained in the range of ≦0.8.

On the low addition side, only an increase in resistance, which is the effect of adding sufficient Ti, can be obtained, and on the high addition side, the loss rapidly increases due to an increase in resistance or a shift from saturation to a decrease, and abnormal grain growth.

Assuming that the amount of T102 added is a constant value and 2000 ppm, V
Similarly, x-d+c is 001 by changing the amount of 2O5 added.
Experiments were conducted near 0.

The effect of V2O5 can be seen even when added in a very small amount of about 50 ppm. When the weight exceeds 11,000 pp, the loss becomes noticeably worse due to abnormal grain growth.

■ As with TiO2, it contributes to the loss improvement of 0.
This is due to increased resistance.

Example 4 Under the same firing conditions as Example 2, Fe20352.6m
ol%, MnO35,8mol%, Zn
As trace additives to 01L, 7%, CaO450pptx, S i O1 [10pps by weight ppm
, T j O22000 pprm.

A ferrite core was manufactured by adding 200 ppl of V2O.

In this case, when organizing the ion distribution using x-d+c as an index, the best power loss characteristics were shown at around 0.010.

Incidentally, in the case of a frequency of 100 kHz and a magnetic flux density of 200 mT, a power loss value of 340 mW/crA was achieved at a temperature of around 80°C. In addition, the high frequency 50(lkl(
Also at z, 930mW/at a magnetic flux density of 100mT
cffl was significantly lower than that of conventional materials. Incidentally, the maximum saturation magnetic flux density was 500 days T.

(Effect of the invention) As is clear from the above, in Mn-Zn ferrite, the optimum ion distribution range, especially divalent Fe and trivalent Mn
By specifying the relationship between
A low-loss power ferrite can be obtained.

Furthermore, the conventional method only stipulates the components before mixing or before firing, but does not regulate the ion distribution range of the ferrite core with respect to the ferrite component. I was unable to respond directly.

If Mn-Zn ferrite, which has significantly improved power loss according to the present invention, is used as a power supply core, a great effect can be obtained in reducing the size and weight of switching converters, for example.

[Brief explanation of the drawing]

FIG. 1 is a chart showing the relationship between the index of x-d+c and power loss, and FIG. 2 is a chart showing the relationship between the index of x-d+c and power loss. X-d due to changes in the amount of TiO□ added when added as a trace additive
It is a chart showing changes in power loss when the index of +c is constant. Agent Patent attorney Tatsuo Chanoki0 0
．． 010 0.020 0.030 0.040 0.
θ50Y, -dsC

Claims (1)

[Claims] 1. A ferromagnetic low-loss manganese-zinc ferrite characterized by satisfying the following relationship in a Mn-Zn ferrite core. Zn^2^+_aMn^2^+_bMn^3^+_cF
e^2^+_dFe^3^+_eZ_fVc_gO^2
^-_4a+b+c+d+e+f+g=3 0.004≦x-d+c≦0.03 Here, Z=trace additive element Vc=cation vacancy X={2(α-β-γ)+δ}/(2a+β+γ+δ)
However, 51≦α≦55 33≦β≦40 7≦γ≦14 0≦δ≦2 α, β, γ, δ are blended raw materials, Fe_2O_3, MnO,
This is the mol% of ZnO and other trace additive elements. 2. The ferromagnetic low-loss manganese-zinc ferrite according to claim 1, which satisfies the following conditions. 0.14≦a≦0.27 0.63≦b+c≦0.77 2.01≦d+e≦2.15 3. 3. The ferromagnetic low-loss manganese-zinc ferrite according to claim 1 or 2, characterized in that SiO_2 and CaO in the following range are added as Z. 0.01≦p≦0.03 0.02≦a≦0.1 However, p is SiO_2 (wt%), a is CaO (wt%)
). 4. The ferromagnetic low-loss manganese-zinc ferrite according to claim 1, 2 or 3, characterized in that Ti_2O and V_2O_5 in the following ranges are added as Z. 0.1≦r≦0.8 0.005≦s≦0.1 However, r is TiO_2 (weight%), S is V_2O_5 (
weight%).