JPH0513214A - Magnetic material for high-frequency use - Google Patents

Abstract

PURPOSE:To provide a useful ferrite material wherein its permeability can be improved without lowering its limiting frequency and without lowering the temperature characteristic of its permeability and its permittivity. CONSTITUTION:V2O5 in 0.01wt.% or higher and 0.5wt.% or lower is mixed with and added to a basic composition which is composed of nickel oxide, cobalt oxide and iron oxide and which is 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). Thereby, it is possible to obtain a magnetic material, for high-frequency use, wherein its permeability has been improved remarkably without lowering the temperature characteristic of its permeability and its permittivity even at a high frequency of 200MHz or higher. The 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 is provided with a high Q even when it is used at the 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 high frequency oxide magnetic material, and more particularly to a ferrite material useful as a magnetic core material for 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.

[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 the high Q at high frequency is high.
Is hard to get.

Therefore, the applicant has a high Q at a high frequency of 200 MHz or higher for which a patent application was previously filed (Japanese Patent Application No. 2-132231), has a magnetic permeability greater than 1, and has a temperature characteristic of dielectric constant. Got a small material.

[0005]

However, the characteristics are not sufficient, and it is desired that the magnetic permeability is large.

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 high frequencies, excellent temperature characteristics of permittivity, and improved magnetic permeability over conventional materials. It is what

[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 high-frequency magnetic material containing 0.01 wt% ≤ V ₂ O ₅ ≤ 0.5 wt% added to the basic composition consisting of components impairs the limiting frequency. It has been found that the magnetic permeability can be significantly improved without the use.

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

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 MH.
Since it cannot be used at high frequencies above z, y / (x + y) is 0.04
I made it bigger. The limiting frequency and the 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 is 1.
Since it will be 5 or less, y / (x + y) was set to 0.30 or less.

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

With respect to the amount of V ₂ O ₅ added, 0.01% by weight or less does not show an improvement in magnetic permeability, and if it is 0.5% or more by weight, the critical frequency is significantly decreased. Above 0.5 wt%.

[0012]

Example Using NiO, Co ₃ O ₄ , and Fe ₂ O ₃ having a purity of 99% or more, these were weighed so that a ferrite porcelain having the composition ratio shown in Table 1 was obtained, 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, added with the amount of V ₂ O ₅ shown in Table 1 and pulverized with water in a ball mill for 24 hours, then added a binder, granulated, and dehydrated. Then, it was dried and molded with a powder press at a pressure of 1000 kg / cm ² .

This molded product was fired in an electric furnace at 1200 ° C. for 2 hours to obtain a sample. The initial magnetic permeability (μ) of each sample, the limiting frequency (f max), the dielectric constant (ε), the temperature characteristics of ε of -25 ℃ ~ 20 ℃, 20 ℃ ~ 80 ℃ and the stability of the characteristics were measured and obtained. The results obtained are shown in Table 1. The limit frequency is Q of 50.
It means the upper limit frequency that can keep the above.

[0014]

[Table 1]

In Table 1, the temperature characteristic of ε is Δε / εΔT (pp
m / ℃), the upper level is -25 to 20 ℃, and the lower level is 20 to 80 ℃.
And

As is clear from Table 1, in the invention example (sample number suffix B), compared with the comparative example (sample number suffix A) which has the same composition but does not contain V ₂ O ₅ as an additive, The magnetic permeability has increased significantly. It should be noted that, in Table 1, all those with the subscript B of the sample number have compositions within the scope of the present invention.

As described above, the ferrite material according to the present invention has the effect of remarkably improving the magnetic permeability without lowering the limit frequency by using V ₂ O ₅ as an additive as in the present invention. Is recognized.

Next, FIG. 1 shows the difference in frequency characteristic of initial permeability depending on the amount of V ₂ O ₅ added. In Fig. 1, V ₂ O ₅ (a) is 0 wt.
%, (B) 0.1 wt%, (c) 0.2 wt%, (d) 0.4 wt%
%, (E) is the one with 0.5 wt% added.

As is clear from FIG. 1, the initial permeability increases as the amount of V ₂ O ₅ added increases, but (e) 0.5 wt%
With the above additions, the lowering of the critical frequency becomes remarkable. Also,
Since the magnetic permeability is not improved when the content is 0.01 wt% or less, the addition amount of V ₂ O ₅ in the present invention is set in the range of 0.01 wt% to 0.5 wt%.

[0020]

As described above, the magnetic material for high frequencies according to the present invention has the magnetic permeability remarkably improved without deteriorating the limiting frequency and the temperature characteristics of the magnetic permeability and the dielectric constant of the conventional material. .. Moreover, when the high frequency magnetic material according to the present invention is used, the size is smaller than that of the air core coil and the
Since it is possible to provide an element having a high temperature characteristic, a good temperature characteristic, a high frequency of 200 MHz or more, and various magnetic permeability values, it is extremely useful industrially.

[Brief description of drawings]

FIG. 1 shows an example of changes in magnetic permeability when V ₂ O ₅ is added to the same composition based on an example.

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) With respect to the basic composition consisting of components, V ₂ O ₅ is 0.01 wt% or more 0.
A high-frequency magnetic material characterized by containing 5 wt% or less.