JPH02183501A - Manufacture of mn-zn soft ferrite - Google Patents

Abstract

PURPOSE:To obtain an Mn-Zn soft ferrite with a uniform crystal organization and a crystal grain boundary as well as an improved magnetic characteristics and a low iron loss value by adding an aqueous solution Ca compound as a Ca source and an aqueous solution Si compound as SiO2 source to a calcination blend material consisting of Fe2O3, Mno and Zno obtained at the calcination process and then grinding-mixing it in water slurry shape. CONSTITUTION:Fe2O3 is used as a main material and the one where Mn and Zn oxides (ZnO and Zn3O4) are mixed by a specified amount is ground and mixed by a ball mill or a vibrating mill and then is calcined. Then, with a calcination powder as 50 to 70% concentration water slurry, grinding mixing is made at warm temperature using a device such as the ball mill, attriter, etc. Aqueous solution CaCl2 and Si compound are blended as CaO and SiO2 sources, which are added by a specified amount as an aqueous solution to this grinding mixing process. These additives become CaO and SiO2 due to oxidation on calcination, are deposited in a thin film shape at a grain boundary of a sintered body, and increases grain boundary resistance, thus efficiently operating on reducing iron loss in high-frequency range.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to high frequency transformers for 1 tier, flyback transformers, which require low loss characteristics under high magnetic flux density.
The present invention relates to a method for manufacturing Mn-Zn soft ferrite used in smooth ticks and the like.

<Prior Art> A general method for producing ferrite consists of weighing raw material powder to have a predetermined composition, mixing and calcining, pulverizing, adding a binder, etc., press-forming, and sintering.

The characteristics required for Mn Zn-based ferrite manufactured by such a process are iron...
can be cited as low. Conventionally, CaO and 5
A method of adding rOt in combination is widely known [see, for example, Japanese Patent Publication No. 36-2283, "Powder and Powder Metallurgy", Vol. 8, No. 3, p. 101 (1961)].

The combined addition of CaO and 5iO1 segregates at grain boundaries and increases electrical resistance, thereby improving magnetic properties in the high frequency range.

The method of adding CaO% Stag is usually to add a small amount of CaCO5,5 lots, etc. in powder form to soft ferrite raw material powder using a mixing device such as a ball mill or attritor.

However, the amount of powders added such as CaCO2 and SiO□ is small (
For example, 0.2% or less], even if a ball mill, an attritor, etc. are used, it is not uniformly dispersed in the raw material powder and it is difficult to mix uniformly. If the additives are mixed unevenly in this way, the grain boundary precipitation of CaO and SiO□ will become uneven, and the crystal grains of the Mn-Zn ferrite sintered body will become uneven, and the thickness of the grain boundary phase will become uneven. This caused deterioration of magnetic properties.

<Problems to be Solved by the Invention> In view of the above-mentioned circumstances, the present invention uniformly disperses trace amounts of additives in the Mn-Zn soft raw material (Mn-Zn soft raw material) to provide a solution in the high frequency range that has a uniform crystal structure and grain boundaries. The object of the present invention is to provide a method for manufacturing Mn-Zn soft ferrite with excellent magnetic properties and particularly low iron value.

<Means for Solving the Problems> The present inventors have conducted extensive studies on a method for uniformly dispersing additives in order to lower the magnetic properties of Mn-Zn ferrite in the high frequency range, particularly the iron loss value. As a result, the mixing and crushing of additives to the Mn-Zn ferrite calcined powder can be reduced to 50-70% of the calcined powder using a ball mill, attritor, etc.
It is done in a concentrated water slurry state. From this, we came up with the idea that by using water-soluble additives such as silane compounds and CaC1z as additives, the additives could be uniformly dispersed in the ferrite powder, and we conducted various experiments.

As a result, the uniform dispersion of water-soluble additives maintains the fine dispersion of trace additives during the subsequent granulation, molding, and sintering processes, resulting in uniformity of crystal grains in the sintered body and the formation of grain boundary phases. It was discovered that the uniformity of the thickness can be maintained, and the present invention was developed.

That is, in the present invention, a predetermined amount of Mn is added to the main raw material FezOz.
After pulverizing and mixing the blended raw material containing O and ZnO, calcination is performed, and 0.03 to 0.13 wL% in terms of CaO and S are added to the calcined blended raw material obtained in the above calcination process as additives.
5iO of 0.005 to 0.025 wt% in terms of iO2
In a method for producing Mn-Zn soft ferrite, the process involves pulverizing and blending ta, followed by granulation and molding steps, and then firing.
Pa-01, MnO and Zn obtained in the above calcination step
Mn-, which is characterized by having a step of adding a water-soluble Ca compound as the Ca source and a water-soluble Si compound as the SiO□ source to the calcined compound raw material consisting of O, and pulverizing and mixing them in the form of a water slurry. This is a method for manufacturing Zn-based soft ferrite.

The water-soluble Ca compound is preferably CaC1,t, and the water-soluble S+ compound is preferably a water-soluble silane compound or 11□5iFa.

The configuration of the present invention will be explained in detail below along with its operation.

First, as a raw material, Fe2nt is used as a main raw material, and a predetermined amount of Mn and Zn oxides (ZnO, Mn, 04) is blended. If necessary, for example, if the particle size is not appropriate, a pulverization step may be added before each compounding. Then, the raw materials are pulverized and mixed using a ball mill or a vibration mill, and then calcined.

Here, calcination helps homogeneous reaction in main firing,
800-110, which is important in terms of alleviating excessive shrinkage due to reaction, and is 100-300"C lower than the main firing.
A temperature of about 0°C is preferred.

Next, the calcined powder is made into a water slurry with a concentration of 50 to 70%,
Pulverize and mix wet using equipment such as a ball mill or attritor. During this pulverization and mixing process, C
Water-soluble CaCl3 and S as aO,5iOz sources
+Compounds are combined and added in a predetermined amount as an aqueous solution. These additives become CaO and SiO□ by oxidation during firing, and precipitate in the form of a thin film at the grain boundaries of the sintered body, increasing the grain boundary resistance and effectively working to reduce iron loss in the high frequency range.

Water-soluble CaC1□ is used as CaO5. An improvement in iron order is observed when the amount added is in the range of 0.03 to 0.13 wL% as CaO. If the temperature is outside the above range, no improvement in iron loss will be observed. In addition, as the SiO□ source, water-soluble Si compounds, especially silane compounds (for example, P, .
・R4Si) Colloidal silica or IIzSi
F6 is effective in improving iron loss. Addition (2) was found to improve iron loss over the conventional value in the range of 0.005 to 0.025 wt% in terms of S2Og.

After mixing and pulverizing the calcined powder with additives, adding a binder,
It is granulated using a spray dryer and then formed into a predetermined shape using press processing or the like.

Next, this molded body is fired according to a conventional method at 1200 to 1200° C. for about 2 to 4 hours while adjusting the oxygen partial pressure to obtain a sintered body completely converted into ferrite.

If trace additives such as CaC0z and SiO□ are not added, uniform mixing at a submicron level or less is impossible, but by using aqueous compounds as the CaO source and SiO□ source, uniform mixing is possible. Compared to the case where CaCO3 and SiO2 are added as a composite of 6 powders that enable mixing, when aClz and a silane compound are added as an aqueous solution, when investigating the Ca distribution state with an EPMA (X-ray microanalyzer), , the sample added as powder is 1
A large difference in density is observed on the order of 0 to several tens of microns, whereas a sample added as an aqueous solution shows uniform dispersion. This is considered to be the cause of the improved characteristics.

<Example> Preferred embodiments of the present invention will be described below along with comparative examples.

Example 1 FeO3-53 mol%, MnO=35 mol%, ZnO=
Raw materials with a basic composition of 12 mol% are mixed and heated to a temperature of 85%.
Calcined in air at 0°C for 2 hours. Additives and subcomponents are added to this calcined powder in the ratio shown in Table 1, mixed and crushed for 30 minutes in a wet attritor (water slurry concentration 55%), and after adding a binder, the powder is manufactured using a spray dryer. It was grainy. Thereafter, it was molded into a toroidal shape with an outer diameter of 36 mm, an inner diameter of 24 mm, and a height of 7 mm. This molded body was fired for 53 hours at 1350'C in an atmosphere with controlled oxygen concentration.

The magnetic properties of the obtained fired product were measured and the results are shown in Table 1.

Example 2 Fe2O2 = 53 mol%, MnO = 35 mol%, ZnO
= Mixing raw materials with a basic composition of 12 mol%, 850°
C Calcined in air for 2 hours. Additive subcomponents were added to this calcined powder in the proportions shown in Table 1, wet mixed and pulverized in an attrike for 30 minutes, and after addition of a binder, the mixture was granulated in a spray dryer. After that, the outer diameter is 36mm
It was molded into a toroidal shape with an inner diameter of 24 mm and a height of 7 IL II 11 mm. This molded body is placed in an atmosphere with controlled oxygen concentration.
It was fired at 1350'C for 13 hours. Table 2 shows the results of measuring the magnetic properties of the obtained sintered body.

As is clear from these results, CaCf! Iron tn is reduced by using an aqueous solution of z and 11□5iFi as additives.

As can be seen from Tables 1 and 2, CaCj! It can be seen that the combined addition of □ and an aqueous organic silane compound contributes to a reduction in iron loss. In Table 1, the amount of A added is Si
The iron loss is lower than the level of the conventional example (No. 15) in the range of 0.005 to 0.025% in O□ conversion, and in Table 2, CaCIV,, is 0.05 to 0.25w.
t% area, that is, 0.03 to 0.3 w in terms of CaO
At L%, the iron loss is lower than that of the conventional example. This is the reason why CaC1□ and the water-soluble silane compound were limited.

Furthermore, in the MnZn ferrite sintered body, the reason why the CaO and SiO□ sources are made aqueous to reduce the iron content is explained as follows. That is, CaC0,, SiO
Adding powdered trace additives such as □ makes it impossible to mix uniformly at submicron levels;
Uniform mixing is possible by using an aqueous compound as the rA, SiO□ source.

<Effects of the Invention> As explained above, according to the present invention, Mn-Zn soft ferrite with excellent iron loss characteristics can be easily obtained, and it has many advantages in terms of miniaturization of A-type devices and measures against heat generation. can get.

Claims (3)

[Claims] 1. A predetermined amount of MnO and ZnO is added to the main raw material Fe_2O_3.
Calcination is performed after pulverizing and mixing the blended raw materials containing
After pulverizing and mixing a SiO_2 source of 0.03 to 0.13 wt% in terms of O and 0.005 to 0.025 wt% in terms of SiO_2, Mn is fired through a granulation and molding process.
- In the method for manufacturing Zn-based soft ferrite, Fe_2O_3, MnO and ZnO obtained in the above calcination step are
A Mn-Zn system characterized by having a step of adding a water-soluble Ca compound as a Ca source and a water-soluble Si compound as a SiO_2 source to the calcined mixed raw material of the additives, and pulverizing and mixing them in the form of a water slurry. Method for producing soft ferrite. 2. The manufacturing method according to claim 1, wherein the water-soluble Ca compound is CaCl_2. 3. The water-soluble Si compound is a water-soluble silane compound or H
The manufacturing method according to claim 1 or 2, wherein the material is _2SiF_6.