JPS59121806A - High-frequency magnetic material - Google Patents

Abstract

PURPOSE:To keep a negative temperature coefficient and improve a density by adding a small amount of V2O5 to a material which has a negative temperature coefficient of initial permeability. CONSTITUTION:To the composition, expressed by a chemical formula NixCoyFez O4 (where 0.8<=x<=1.2, 0.01<=y<=0.03, 1.8<=z<=2.2 and x+y+z=3), 2-4wt% of Bi2O3, 0.2-3wt% of SiO2 and 0.005-0.04 (expression of above chemical formula) of V2O5 are added and baked. The material to which V2O5 is added has a temperature coefficient of initial permeability which is uniformly negative in the range of 0-80 deg.C and has an improved density so that the strength of the product is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature coefficient of a ferrite magnetic core used at high frequencies. Inductance elements of various high frequency circuits are formed from a ferrite core serving as a magnetic core and a coil wound around a bobbin. Particularly as circuits using this inductance element operate at higher frequencies, it is important that they be stable against changes in ambient temperature.

The following measures have been conventionally adopted to ensure stability against temperature changes. In other words, since the circuit is usually composed of a combination of capacitors and inductance elements,
The material is selected so that the combined temperature coefficient of both is small.

This selection is made because the capacitance G of the capacitor generally has a negative concentration coefficient. deg). However, it cannot be said that the temperature coefficient of the entire circuit obtained by this selection is fully satisfactory because the temperature coefficient of other parts other than the ferrite core and the capacitor, especially the coil itself, is positive. In order to roughly improve this point, it is possible to make the temperature coefficient of the ferrite magnetic core negative, but it is difficult to obtain such a material. Materials with a negative temperature coefficient of initial permeability are:
There is Japanese Patent Application No. 53-72567.72568, but these had a density of only 4.5 g/cm@3 at most and had a drawback in product strength.

The present invention aims to maintain a negative temperature coefficient and improve density by roughly adding a small amount of V2O5.

Examples will be described below.

Example 1 The chemical formula is N'O-'l'l COo, 2q "1.qf
NiO, CO203, Fe2 so that J o4
I weighed O3 and got 8! 2030.5wt%, S
i 02 0.5wt%, V2O5 in chemical formula 0.
The powder to which 0.01 was added was mixed for 24 hours in a ball mill using water as a medium.

The mixed powder was calcined at 950°C in the air and then wet-pulverized in a ball mill for 24 hours. The pulverized powder is P
After granulation using VA solution, the ring-shaped molded body was fired at 1100° C. for 3 hours in the atmosphere. The properties of this sample are shown in Table 1 along with the results without the addition of V205.

Table 1 In Table 1, the temperature coefficient of initial magnetic permeability is defined by the following formula.

This temperature coefficient was uniformly negative between 0 and 80°C.

Example 2 Chemical formula: Nio, 5 COo, o+5 Fe 1
．． '? 404 was weighed and Bi 2 was added to it.
03 1.5wt%, 3i020.3wt%, V2O5
Table 2 shows the properties of a mixture in which 0.03 of R = 0.03 was added, which was subjected to the same treatment as in Example 1 and fired at 1050° C. in the atmosphere. This temperature coefficient was also a uniform negative value from 0 to 80°C.

Table 2 As is clear from these examples, the addition of V2O5 is effective in improving the density and product strength while maintaining a negative temperature coefficient.

Regarding the composition of the present invention, N1 ferrite was chosen because it increases the voltage expansion ratio at high frequencies.
This is to provide high electrical resistance. Therefore, an element having high electrical resistance and a uniform negative temperature coefficient, such as CuO, may be contained. Furthermore, although CO20 is effective in further increasing the voltage magnification ratio, as the amount increases, the so-called secondary peak shifts significantly toward the high temperature side. A uniform negative temperature coefficient cannot be achieved between 0 and 80°C.

B! For '20a and 5iO2ffl, uniform negative temperature coefficients can be obtained within the claimed range. V
Regarding the amount of 205, it goes without saying that if it is too small, there will be no effect of improving the density, but if it is too large, different phases are likely to occur and the magnetic properties will deteriorate.

As described above, the composition of the present invention makes it possible to obtain a uniform negative temperature coefficient material with high density.

Claims (1)

[Claims] Chemical formula N i x COy F ez Oa
(However, 0.8≦X<1.2.0.01<V<
0.03, 1.84242.2 x0V-t1=
3) in the composition represented by 8!20 and S! 02 to 0.
2≦3! 20 a <4wt%, 0.2riS i
O2<3wt%, V2O5 in the above chemical formula o, oo
A high-frequency magnetic material, which is made of ferrite obtained by adding 0.04 s to 0.04 and firing, and having a temperature coefficient of initial magnetic permeability that is uniformly negative in the range of 0 to 80°C.