JPS63260883A - Mn-zn base ferrite core with good high frequency properties - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a Mn-Zn ferrite core with excellent high frequency characteristics suitable for use in deflection yokes, flyback transformers, power transformers, etc., and its production. It is about the method.

(Prior Art) Characteristics required of the transformer core as described above include low iron loss in a high frequency range, and high saturation magnetic flux density (Bs) and high initial magnetic permeability.

In order to reduce iron loss in a high frequency region, it is necessary to reduce not only hysteresis loss but also eddy current loss at the same time.

As a method for reducing eddy current loss, for example,
As disclosed in Japanese Patent Publication No. 380 and Japanese Patent Publication No. 36-2283, approximately 0.05 to 0.5 wtχ of calcium oxide is contained in the material and precipitated at the grain boundaries of ferrite. It is known that increasing resistance is an effective means.

Further, Japanese Patent Publication No. 48-6759 reports that addition of Ca chloride salt is effective. According to this method, Ca chloride salt reacts with Fe, 0°, Mn3O4, ZnO, etc. to form oxide spinel at the ferrite sintering temperature, that is, 900°C to 1350″C, while chlorine reacts with Ca ions in the ferrite core produced in this way tend to precipitate at the grain boundaries without being dissolved in the spinel structure.Therefore, the addition of Ca chloride salt is It is said to be useful in forming high-resistance films.

In addition to the calcium compounds mentioned above, additives include
CaO-Sin, (NECRe5earch & D
development.

p, 66+ Nα19 (1970)), CaO−
VzOs (see Japanese Patent Publication No. 37-15077) and CaO-VzOs -5i(h (Japanese Patent Publication No. 59-20)
3768) are known, and their addition in an appropriate blend contributes to the formation of a high-resistance grain boundary phase.

In all of the above methods, calcium oxide, calcium chloride, etc. are added to the raw material powder by mixing it in powder or solution form and then calcining it, or by thoroughly crushing the raw material powder after calcining it. , followed by mixing in powder or solution form.

(Problems to be solved by the invention) Generally, the sintered body obtained by the method described above is
A high resistance layer is formed at the grain boundaries due to the additive effect, and a fine grain structure can be obtained, which is advantageous in reducing loss, but it is disadvantageous in increasing magnetic permeability. .

In other words, as mentioned in Section 7, cores for various transformers are required not only to have low iron loss in the high frequency range, but also to have high initial magnetic permeability, but conventional technology does not have low iron loss. It is difficult to satisfy the requirements of high magnetic permeability and high magnetic permeability at the same time, and improvements have been desired.

This invention was developed in view of the above-mentioned current situation.
The purpose of this paper is to propose a ferrite core that has excellent initial permeability as well as iron loss characteristics in a high frequency range, along with an advantageous manufacturing method.

(Means for solving the problem) As a result of numerous experiments to solve the above problem, the inventors modified the conventional method of adding additives, processed it into a molded product, and then It has been found that by impregnating the sintered body with a solution of the additive, a concentration gradient of the additive is imparted to the sintered body, thereby achieving both low loss and high magnetic permeability.

This invention is based on the above knowledge.

That is, in this invention, the amount of surface adhesion is 0.1 to 2 on the surface layer.
Mn-Zn ferrite core with excellent high-frequency characteristics, which has a concentrated layer of calcium with a concentration of 0.0cm/CHI, and a surface layer containing calcium, silicon, and vanadium with a surface adhesion of 0.1 to 20cm/cm. Mn-Z with excellent high frequency characteristics, comprising a layer enriched with one or two of the following:
It is an n-type ferrite core.

In addition, this invention provides Pet's as a main component, Mn
After mixing O and ZnO in predetermined amounts, mixing, crushing, calcining,
The molded body is molded through a granulation process, and then 0.1 to 15% of a calcium compound is added to the molded body. A method for manufacturing an Mn-Zn ferrite core having excellent high frequency characteristics, which comprises impregnating a treatment liquid containing a treatment liquid in a range of Owtχ, followed by drying and firing;
After blending a predetermined amount of O, it is molded through a mixing, pulverizing, calcining, and granulating process, and then one or two of a calcium compound, a silicon compound, and a vanadium compound are added to the molded body.
This is a method for manufacturing an Mn--Zn-based ferrite core with excellent high frequency characteristics, which is characterized by impregnating the core with a treatment solution containing seeds in a range of 0.1 to 10.0 wtx, followed by drying and firing.

This invention will be specifically explained below.

As mentioned above, in order to reduce eddy current loss, which accounts for the majority of iron loss, it is necessary to form a high resistance layer and uniformly refine crystal grains. On the other hand, in order to increase magnetic permeability, it is necessary to facilitate the movement of domain walls, that is, to increase the size of crystal grains.

In this invention, a solution containing a calcium compound in the molded body,
Alternatively, by impregnating a solution containing a calcium compound and one or two of a silicon compound and a vanadium compound, calcium or calcium and silicon and/or vanadium elements (hereinafter referred to as enriched elements) can be formed from the surface to the inside of the molded body. A concentration gradient of (generally referred to as) is applied, and then, after sufficient drying, firing is performed. According to this method, a high resistance layer with fine crystal grains is formed in the surface layer of the sintered body, while a structure with relatively large crystal grains is obtained in the interior, thus reducing the initial magnetic permeability. Moreover, the high frequency iron loss characteristics can be significantly improved.

(Function) Hereinafter, the method for manufacturing a ferrite core according to the present invention will be specifically explained in order of steps.

First, as a raw material, a material containing ferric oxide (Fezes) as the main raw material and a predetermined amount of metal oxides of Mn and Zn is used. If necessary, for example, if the particle size is not appropriate, a pulverization step may be added before each compounding.

Next, the raw materials are mixed and pulverized using a ball mill or a vibration mill, preferably to an average particle size of about 0.8 to 1.2 μm, and then calcined. Here, calcination is important in the sense of promoting a homogeneous reaction in the main firing and mitigating excessive shrinkage due to the reaction.
It is preferable to carry out at a low temperature of about 800 to 1100°C.

Next, the calcined powder is pulverized and then granulated using a spray dryer or the like.

In the present invention, the above mixing, pulverization, calcination, and granulation do not necessarily have to be performed in the order as described above, and for example, the pulverization step and the calcination step may be performed in the reverse order.

Thereafter, it is molded into a predetermined shape by pressing or the like, and the present invention is characterized in that the molded product thus obtained is impregnated with a treatment liquid containing a compound of a concentrating element.

In FIG. 1, FezQ: 70.9htχ (hereinafter simply shown in %).

The magnetic properties of the sintered bodies obtained by impregnating a molded body with a composition of MnO: 19.6% and ZnO: 9.5% with calcium chloride aqueous solutions of various concentrations, then drying and firing were investigated. Show the results.

As is clear from the figure, the concentration of calcium chloride is 0.
The magnetic properties of the samples impregnated with a 1-15% aqueous solution were particularly excellent.

As is clear from the figure, no improvement in core loss was observed in the magnetic properties of the sample impregnated with an aqueous solution containing calcium chloride at a concentration of less than 0.1%. The reason for this is considered to be that the concentration of calcium chloride was too low and did not contribute to an increase in the resistivity of the sintered body. On the other hand, samples impregnated with an aqueous solution of calcium chloride exceeding 15% showed a slight improvement in iron loss, but on the other hand, a significant decrease in initial permeability was observed. This is thought to be because the growth suppressing effect was too strong and the crystal structure of the sintered body became extremely small.

For the above reasons, in the present invention, the calcium compound concentration in the impregnating solution is limited to a range of 0.1 to 15%.

Similar experiments were also carried out using a slurry of calcium compounds, silicon compounds, and vanadium compounds (weight ratio Ca
b/(Sift + VzOs) = 3.8), the magnetic properties of the samples impregnated with the slurry with a treatment solution concentration of 0.1 to 10.0% were excellent;
The compound concentration of the treatment liquid containing a calcium compound and one or both of a silicon compound and a vanadium compound was limited to a range of 0.1 to 10.0%. In this case, the slurry is uniformly mixed using a suitable stirrer to make the concentration uniform.

The impregnation may be carried out by immersing the molded body in a treatment liquid containing the compound within the above-mentioned range for several seconds, or by spraying the treatment liquid onto the molded body using an air gun, a spray gun, or the like.

However, when using the former method, if the immersion time is too long, cracks may occur after sintering, or high concentrations of calcium may penetrate too far into the interior, resulting in property deterioration such as a decrease in initial magnetic permeability and an increase in iron loss. Therefore, the immersion time in a treatment solution containing a calcium compound should be about 1 to 5 seconds, while the immersion time in a treatment solution containing a lucium compound and a silicon and vanadium compound should be about 1 to 10 seconds. It is preferable to do so. Furthermore, when using a slurry for the processing liquid, it is desirable to sufficiently stir it to make the composition uniform, and also to adjust the weight ratio of the concentrating elements, i.e., Cab/Sin, , C
aO/V, 0. or CaO/(SiOz+Vies)
If the weight ratio is less than 0.2, the effect of reducing iron loss will be small, so the weight ratio is preferably 0.2 or more.

Next, according to the usual method, after drying at a temperature of about 80 to 120 °C, drying at a temperature of about 1200 to 140 °C while adjusting the oxygen partial pressure.
The material is fired at 0° C. for about 22 to 4 hours to form a sintered body that is completely ferrite-formed.

In addition, when we investigated samples with good magnetic properties obtained by impregnation with the above-mentioned appropriate treatment liquid, it was found that the amount of surface adhesion of concentrated elements was 0.1 to 20 μ/cm in all samples.
” was found to be in the range.

Furthermore, the results of investigating the relationship between the amount of surface adhesion and the concentration gradient of the concentrated layer are shown in FIGS. 2(a) and 2(b), respectively. Note that the concentration gradient was expressed by the measured value of electrical resistivity over the thickness of the sample.

As is clear from the figure, when the amount of surface adhesion is outside the above range, no effective concentration gradient is provided.

Therefore, the amount of surface adhesion of the concentrated element in the concentrated layer was set to 0.1
It was limited to a range of ~20 .mu./c112. By the way, the average concentration gradient in the concentrated layer of the sample used in the above experiment is
It was 1 to 3 .mu./cm.

(Example) Ferric oxide <FetOx): 70.9%, manganese oxide (MnO): 19.6% and zinc oxide (ZnO)
): After wet mixing raw materials with a composition of 9.5%,
After granulation, it was calcined in air at a temperature of 920°C for 2 hours. After pulverization, the powder was granulated to a diameter of about 100 pm to obtain ferrite powder, and the resulting powder was molded into a toroidal shape using a mechanical press. At this time, the molding density is 2
．． 85 to 2.90 g/cm'', parent control, f, -0 21 such toroidal molded bodies (outer diameter 36cm, inner diameter 24cm) were prepared respectively.
NOx)t, CaBrz and Ca1. One piece each was immersed for several seconds in 20 types of treatment solutions with respective aqueous solution concentrations of 0.08%, 1%, 5%, 12%, and 16%.

Immediately after the impregnation treatment by immersion, it was dried in a constant temperature bath for 24 hours, and then fired at 1300°C for 3 hours while adjusting the oxygen partial pressure.

The magnetic properties of each sintered body thus obtained were measured at room temperature (25°C).
) are shown in Table 1.

For comparison, the same table includes those without impregnation treatment, as well as calcined powders with the above raw material powder composition)',! After crushing, 0.01%, 0.1%, and 0.7% of calcium chloride powder was added to the raw materials, respectively, and the powder was then granulated to a diameter of about 100 μm. The resulting powder was shaped into a toroidal shape using a mechanical press. Measurement results for a sintered body obtained by molding and then processing under the same firing conditions as above are also shown.

From the same table, when comparing a sample of a sintered body impregnated with an aqueous solution with a concentration according to the present invention and a sample not impregnated (reference example), the initial magnetic permeability and saturation magnetic flux density hardly change, and the iron loss improves. I know that there is.

Example 2 Twenty-one toroidal molded bodies were prepared in the same manner as in Example 1, and CaCO5+ Sing + CaCO5+
VgOs and CaCO3+ Sing + V! O5
water dispersion slurry (approx.
0 m solution and disperse each compound uniformly with a stirrer) for a few seconds, and then heated to approximately 100 °C.
Table 2 shows the results of measurements of magnetic properties after drying for 3 hours and then undergoing the same treatment as in Example 1.

From Table 2, (Ca: 5 +St: 1) f
f1g/cm” sample and (Ca: 2 + Si
1) mg/cm'' sample, a significant reduction in iron loss was achieved without reducing the initial permeability and saturation magnetic flux density, compared to the non-impregnated example.

On the other hand (Ca: 0.05 + Si: 0.01)■
For samples with a small amount of surface adhesion (/cm"), there is no improvement effect compared to the case without impregnation; on the other hand, when the amount of surface adhesion is large, the initial magnetic permeability and saturation magnetic flux density decrease significantly.

This tendency is the same when the impregnation treatment is performed with a slurry containing calcium carbonate, vanadium oxide, and a composite addition of these and silicon oxide.

(Effects of the Invention) According to the present invention, it is possible to easily obtain a Mn-Zn-based ferrite core that is excellent not only in iron loss characteristics but also in initial magnetic permeability and saturation magnetic flux density, and is particularly useful as a power supply core. In the current situation where cores for TVs and TVs are used at higher frequencies, being able to significantly reduce iron loss without reducing initial magnetic permeability or saturation magnetic flux density has great advantages in terms of downsizing equipment and countering heat generation. .

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the concentration of calcium chloride in the treatment solution during impregnation treatment and the magnetic properties of the sintered body. Figure 2 is the specific resistance across the thickness of the sintered body obtained according to the present invention. It is a graph showing changes in values.

Claims (1)

[Claims] 1. Surface adhesion amount on the surface layer is 0.1 to 20 mg/cm^2
A Mn-Zn based ferrite core with excellent high frequency characteristics and a calcium concentrated layer. 2. Fe_2O_3 as the main component, MnO and Zn
After blending a predetermined amount of O, it is molded through mixing, pulverization, calcining, and granulation steps, and then a calcium compound is added to the molded body.
．． Impregnated with a treatment liquid containing in the range of 1 to 15.0 wt%,
A method for producing an Mn--Zn-based ferrite core having excellent high frequency characteristics, which comprises drying and firing. 3. Surface adhesion amount is 0.1 to 20 mg/cm^2 on the surface layer.
M with excellent high frequency characteristics, comprising a concentrated layer of calcium and one or two of silicon and vanadium.
n-Zn ferrite core. 4. Fe_2O_3 as the main component, MnO and Zn
After blending a predetermined amount of O, it is molded through a mixing, pulverizing, calcining, and granulating process, and then one or two of a calcium compound, a silicon compound, and a vanadium compound are added to the molded body.
A method for manufacturing an Mn-Zn ferrite core having excellent high frequency characteristics, which comprises impregnating the core with a treatment solution containing seeds in a range of 0.1 to 10.0 wt%, followed by drying and firing.