JPS605044B2 - Ferrite manufacturing method - Google Patents

Description

Detailed Description of the Invention The present invention provides iron oxide (Q-Fe203) with high chemical activity.
By using Ni as a raw material, it has extremely few pores and has high magnetic permeability, magnetic flux density, and electrical resistance.
- This relates to a method for manufacturing Zn ferrite.

In general, ferrite is a polycrystalline oxide ferromagnetic material that is obtained by mixing iron oxide as a main component with one or more of nickel oxide, manganese oxide, zinc oxide, and other oxides and firing the mixture. It is generally available on the market as an oxide competitive complex of

This manufacturing method is usually called a dry method. However, as a property of the oxide stripe, there are numerous pores within each crystal grain and at the grain boundaries of the crystal, which causes a significant decrease in the magnetic permeability, magnetic flux density, etc. of ferrite. .
In addition, in the dry method, if the raw materials are not mixed uniformly,
Furthermore, even when the particle size of the raw material is large, the ion distribution of the crystals becomes non-uniform, which also causes deterioration of the magnetic properties. Pores can be removed by hot pressing, which heats ferrite powder to an appropriate temperature and presses it from the outside in this state, or by isostatic pressing the powder at a pressure of about 2 to 1 on/on. There are methods. However, all of these methods have the disadvantage of lacking mass production, and are not industrially advisable. In order to obtain Akatsuki crystals with few pores and uniform ion distribution using a transparent dry method, preparatory, granulation,
Of course, each process of forming and firing must be set to optimal conditions, but magnetic permeability and residual porosity are also significantly affected by impurities in the raw materials and the particle size of the raw materials. It has been reported that In general, in the process of crystallizing ferrite, the aging phenomenon between ferrite powders and the process in which certain ferrite crystal grains grow while spring coalescing with other ferrite crystal grains occur simultaneously. It is said that in this coagulation process, when accompanied by severe movement of grain boundaries, pores are trapped within the crystal grains, and when condensation occurs between large grains, pores remain at the grain boundaries. In the process of obtaining a ferrite competitive body, the following methods can be mentioned to increase scale precision and improve ion distribution. In other words, at the end of calcination, the calcination powder contains a large amount of different phases other than ferrite to increase the concentration gradient of each ion between the calcination powder particles. A method that causes a chemical change as the substance moves. This method is effective when used for burning Carnet-type ferrite, which involves the generation of intermediate phases such as orthoferrite. In addition, to the extent that grain growth does not occur at the end of calcination,
After forming a ferrite phase with as uniform an ion distribution as possible, this fine powder is subjected to grain growth during sintering. Ni-Z
Since n-ferrite does not involve the formation of an intermediate phase,
It is necessary to achieve densification using this method. In all of these cases, it is desirable that the false powder be fine particles;
In particular, brazing is performed from calcined powder that depends only on physical activity. In the latter case, unless the calcined powder is fine particles,
Refinement becomes extremely difficult. In order to obtain calcined powder of fine particles, the calcining temperature may be lowered. However, in order to promote ferrite formation at low temperatures, it is necessary to use raw material fine particles with high surface activity. In the case of Ni-Zn ferrite, the stacking state of oxygen ions of the raw materials Nio, Zno, and Q-Fe203 is as follows: Ni0 is ABCABC... fcc
It has a similar laminated structure, and Zn0 is ABAB...
It has a structure similar to hcp. On the other hand, Q-Fe20
3 has a rhombohedral structure and the arrangement of oxygen ions is also different from fec or hCp. When ferrite formation progresses from a raw material, it is reasonable to assume that most of the diffusion occurs by metal ions with a small ionic radius. So,
Diffusion of metal ions is easy. Therefore, the critical stage in which ferrite formation progresses is determined by the diffusion rate of Fe ions. The above is consistent with the fact that when a raw material with a large particle size is used, ferrite formation is difficult to proceed unless the temperature is high, and the ion distribution of the generated ferrite is also uneven. It can be seen that the diameter has a very large effect on ferrite formation. Q-Fe203 is Britain of the. Institute for Chemical Research Kiyoto University (B side etinofthe Insti
tute for Chemical Research
h Kyoto University) No. 4 Already Registered No. 4~
No. 5, pp. 406-415, published in 1965. As reported in this paper, in normal particles (particle size of about 5 Buddhas), weak ferromagnetism appears due to the magnetic moment moving from the C-plane toward the C-axis. The spin flipping temperature (hereinafter referred to as Ts) is about -15°C. However, the grain size is 4.
As the temperature increases, Ts gradually shifts to the lower temperature side, and at a particle size of about lr, Ts becomes -35°C. Furthermore, at 0.1〆, it suddenly decreased to -100qo per rs, and at 250A. -What is the change in T? This 0. At Ikimu/Yu, it becomes almost independent of temperature. The reason for this is that the intestinal ions near the particle surface have a different crystal field and magnetic dipole field than those inside the particle;
For fine particles, the effects of lattice defects and lattice misalignment are significant. If these facts are viewed from the viewpoint of chemical reactivity, the shift of Ts to the low temperature side clearly indicates that the chemical activity is high. The inventors paid attention to the above fact, and the mole percentage of nickel oxide was 15 to 25%, zinc oxide was 15 to 35%,
Ni-Zn ferrite was produced and bonded by variously changing the grain size of the ferric oxide raw material, that is, Q-Fe203, in a matrix of ferric oxide consisting of 45 to 60% ferric oxide, and as a result, it was found to have excellent properties. We obtained the following results.

Here, the reason why the blending ratio of nickel-zinc ferrite was limited to 15 to 25% of nickel oxide, 15 to 35% of zinc oxide, and 45 to 60% of ferric oxide in molar percentage is that high magnetic permeability can be obtained. This is because the composition range is effective only within the range of the above-mentioned compounding ratio, and is controlled by the particle size of the Q-Fe2Q raw material within that composition range. therefore,
If the mixing ratio of zinc oxide, nickel oxide, and ferric oxide is less than or greater than the above, the desired high magnetic permeability cannot be obtained even if the particle size of Q-Fe203 is changed. The embodiments and effects of the present invention will be shown below in Examples. Example Ni017.8hol%, Zm032.9hol
%, Q-Fe2Q5 hol%, the raw materials were mixed in a pole mill, fired at below 1000℃,
After pulverization, it was molded with a metal mold press and cassetted at 1350° C. or lower.

The average particle size of the raw materials used was 3.0 for both Ni○ and Zn○. Q-Fe203 is 0.025r, 0.
05 Buddha, 0.1 Buddha, 1〆 and 5 Mountain were used. All production conditions for obtaining ferrite from raw materials having the above particle size were the same. Regarding the obtained sample, magnetic permeability at 0.9 MHz and electrical resistance p(
The results shown in Table 1 were obtained by measuring the magnetic flux density Bo (G) and the dawn density d (evening/earth). As is clear from Table 1, when the particle size of Q-Fe203 becomes 1 or more, it no longer exhibits the properties of fine particles magnetically, and the crystal density also decreases significantly, and the magnetic properties also deteriorate. .

Moreover, when the samples shown in the table were examined by X-ray diffraction, structure observation, and an X-ray microanalyzer, all of the samples were found to have a single phase of NiZn ferrite. However, the particle size of Q-Fe203 is 1. When the temperature was exceeded, the number of pores in the ferrite silk body produced from this increased slightly. Furthermore, when a 5r raw material was used, the number of vacancies increased mainly at grain boundaries, and it was confirmed by an X-ray microanalyzer that the distribution of Ni ions was somewhat non-uniform. In addition, Q-Fe of 0.1 French or less
By using 2Q fine particles, the preliminary temperature and competitive temperature can be lowered by about 100 to 200°C, respectively. As detailed above, the Ni-Zn ferrite material of the present invention, which uses Q-Fe203 fine particles as the raw material, can be formed as a high-density sintered body at a lower temperature and with a higher initial magnetic permeability than the secondary materials. Therefore, if this material is applied to magnetic heads, etc., there will be great practical benefits.

Claims (1)

[Claims] 1 In producing nickel-zinc ferrite consisting of NiO, ZnO, and Fe_2O_3, raw materials with an average particle size of 0.5 μ or less, which is smaller than the particle size of the other main component raw materials, are used only for Fe_2O_3 among the main components. A method for producing Ni-Zn ferrite, characterized by the following.