JPH0513213A - Manufacture of magnetic material for high-frequency use - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a ferrite material wherein its limiting frequency is high at 200MHz or higher, the temperature characteristic of its permeability and its permittivity is good and it can be used stably at a high frequency in the manufacturing method of a magnetic material, for high-frequency use, which is used as the magnetic core of an inductance element in an antenna, an LC resonance circuit, a high-frequency transformer or the like. CONSTITUTION:Molded bodies 1 which are composed of nickel oxide, cobalt oxide and iron oxide and which are composed of a composition expressed by the general formula of (NiO)x(CoO)y(Fe2O3)z (where 0.04<y/(x+y)<0.30, 0.4<z<0.6 and x+y+z=1.0) are buried and baked inside a powdery body or porous particles 2 whose composition is the same as that of the molded bodies. Thereby, it is possible to obtain a magnetic material, for high-frequency use, wherein its limiting frequency is high and the temperature characteristic of its permeability and its permittivity is good even at a high frequency of 200MHz or higher.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high frequency oxide magnetic material, particularly a ferrite material useful as a magnetic core material of an inductance element used in an antenna, an LC resonance circuit, a high frequency transformer or the like at a high frequency of 200 MHz or more. Regarding

[0002]

2. Description of the Related Art Conventionally, NiZn has been used as a magnetic material for high frequencies.
High-frequency ferrite materials such as ferrite are used, but NiZn ferrite has a high frequency at 200MHz or higher.
Air-core coils are used because of the drawback of reduced value.

However, even when the air core coil is used,
Since the effective initial magnetic permeability is 1, the size of the element is large, and the inductance is also small, so that the Q deterioration due to the resistance of the coil winding is large, and it is difficult to obtain a high Q at a high frequency. ..

Therefore, the applicant has a high Q at a high frequency of 200 MHz or more, and has a magnetic permeability of more than 1 and a permittivity of more than 1 as described in the patent application (Japanese Patent Application No. 02-132231). A material with small temperature characteristics was obtained.

[0005]

However, the characteristics are not sufficient, and one having a high Q up to a high frequency is desired.

In view of the above, it is an object of the present invention to provide a high frequency magnetic material having a high Q up to a high frequency and having excellent temperature characteristics of magnetic permeability and dielectric constant.

[0007]

The present invention comprises nickel oxide, cobalt oxide and iron oxide, and has the general formula (NiO) _x (Co
O) _y (Fe ₂ O ₃ ) _z (however, 0.04 <y / (x + y) <0.30, 0.4 <z <
0.6, x + y + z = 1.0)
A method for producing a high-frequency oxide magnetic material, which comprises burying in a powder or porous particles having the same composition as this molded article and firing it, has a high Q even at a high frequency of 200 MHz or more.
And a method for obtaining a ferrite material having excellent temperature characteristics of dielectric constant.

The ferrite material according to the present invention is embedded in a powder having the same composition as that of the ferrite and fired,
It can be seen that a high Q is obtained and the magnetic properties are significantly improved.

This is because the filling powder has a large specific surface area.
The filling powder serves as a cushioning material for the atmosphere to keep the atmosphere around the sample in an appropriate state. This is because the densification is prevented due to the decomposition of the characteristic component, the variation in the composition between the surface and the inside is suppressed, and the variation is reduced.

The composition ratio of the high frequency oxide magnetic material according to the present invention is limited to the above range for the following reason.

That is, when y / (x + y) is 0.04 or less, a high initial permeability is obtained, but the critical frequency is low and 200 MHz.
Since it cannot be used at high frequencies above z, y / (x + y) was made larger than 0.04. The limiting frequency and material impedance can be increased by containing Co, and the temperature characteristic of the dielectric constant can be reduced to 1000 ppm / ° C. or less. However, the initial magnetic permeability increases with the inclusion of Co.
Since it becomes 1.5 or less, y / (x + y) is set to 0.30 or less.

On the other hand, z, that is, the molar fraction of Fe ₂ O ₃ is 0.4
Even if it is less than or equal to 0.6 or more, the limit frequency is increased by the addition of Co, but a different phase occurs due to the deviation from the stoichiometric composition of the spinel structure, and both the dielectric constant and magnetic permeability characteristics become unstable. Further, when it is 0.6 or more, the phenomenon of so-called magnetic field deterioration becomes remarkable, so 0.4 <z <0.6.

[0013]

Example Using NiO, Co ₃ O ₄ , and Fe ₂ O ₃ having a purity of 99% or more, these were weighed so as to obtain a ferrite porcelain having the composition ratio shown in Table 1, and each obtained mixture was mixed with water. The mixture was placed in a ball mill, mixed for 4 hours, dehydrated and dried.
Then, it was calcined in an electric furnace at 900 ° C for 2 hours, crushed with water in a ball mill for 24 hours, then added a binder, granulated, dehydrated and dried, and then dried in a powder press to 1000
A molded product 1 was obtained by molding at a pressure of kg / cm ² .

As shown in FIG. 1, the molded product 1 was embedded in a powder 2 having the same composition as the molded product in a sheath 3 and fired in an electric furnace at 1200 ° C. for 2 hours to obtain a sample. The magnetic properties of the obtained fired product were measured, and the results are shown in Table 1.

The samples are serial numbers (No. 1 to No. 1) depending on their composition.
23) is attached to distinguish. In Table 1, the sample numbers marked with * are samples having a composition outside the scope of the present invention, and the others are samples having a composition within the scope of the present invention.

For comparison, a comparatively fired product (sample number suffix A) which was fired without being embedded in a powder of the same composition, and which was otherwise fired under the same conditions as the invention example (sample number suffix B). Was obtained, and its magnetic characteristics were measured, and the measurement results are shown in Table 1.

The magnetic properties are measured by measuring the initial permeability (μ) of each sample, the limiting frequency (f max), the permittivity (ε), -25 ° C.
The temperature characteristics of ε at 20 ° C. and 20 ° C. to 80 ° C. and the stability of the characteristics were measured. The limiting frequency means an upper limit frequency at which Q can be maintained at 50 or more.

[0018]

[Table 1]

In Table 1, the temperature characteristic of ε is Δε / εΔT (pp
m / ° C), (a) is -25 to 20 ° C, and (b) is 20 to 80 ° C.

As is clear from Table 1, in this invention example (sample number subscript B), compared with a comparative example (sample number subscript A) which has the same composition but is not buried in powder and fired (sample number subscript A).
% Limit frequency is increasing.

As described above, in the ferrite material according to the manufacturing method of the present invention, the critical frequency is increased by 5 to 10% by burying in the powder having the same composition as the ferrite and firing as in the present invention. It is recognized that the magnetic properties are significantly improved.

[0022]

As described above, the present invention is a method for producing a ferrite material having an initial magnetic permeability of more than 1 and a critical frequency of 200 MHz or more and good temperature characteristics of magnetic permeability and dielectric constant. Is realized. When the high frequency magnetic material manufactured by the present invention is used, it is smaller than the air-core coil and has an extremely high Q and good temperature characteristics.
Since it is possible to provide a stable element that can be used at a high frequency of MHz or higher, it is extremely useful industrially.

[Brief description of drawings]

FIG. 1 shows an example of a method for setting a molded body when it is embedded in particles having the same composition and fired.

[Explanation of symbols]

 1 molded product 2 powder 3 sheath

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Sakabe 2 26-10 Tenjin Tenjin, Nagaokakyo City, Kyoto Murata Manufacturing Co., Ltd.

Claims (1)

[Claims] [Claim 1] Nickel oxide, cobalt oxide, and iron oxide, which are represented by the general formula (NiO) _x (CoO) _y (Fe ₂ O ₃ ) _z (where 0.04 <y /
(x + y) <0.30, 0.4 <z <0.6, x + y + z = 1.0) A molded product composed of the components is embedded in a powder or porous particles having the same composition as the molded product and baked. A method of manufacturing a magnetic material for high frequency, comprising: