JP2731357B2 - Method for producing Mn-Zn ferrite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency, high permeability M
An object of the present invention is to provide a manufacturing method for obtaining an n-Zn-based ferrite.

[0002]

2. Description of the Related Art Mn--Zn ferrites having high magnetic permeability are mainly composed of Fe2O3, ZnO and MnO, and various additives (Bi, Ca,
V).

[0003] This Mn-Zn ferrite is used as a magnetic core of a transformer, a noise filter, and the like, and the miniaturization of parts is being promoted by utilizing high magnetic permeability characteristics.

[0004]

For example, as a magnetic core for a noise filter, there has been an increasing demand for a material having a high magnetic permeability up to a high frequency (up to 500 kHz).

However, in the case of the conventional Mn-Zn ferrite, there is a problem that the frequency characteristic of the magnetic permeability is poor, the magnetic permeability decreases at a high frequency, and the loss at a high frequency increases.

In view of the above, an object of the present invention is to obtain a Mn-Zn ferrite having high frequency and high magnetic permeability.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a Mn-Zn ferrite which contains CaO as an auxiliary component in an amount of from 0.05 to 0.05%.
0.12% by weight, 0.02% by weight or less of Bi2O3 (excluding 0% by weight), and 0.01 to 0.2% of SiO2.
It contains 0.2% by weight (but does not include 0.01% by weight), and is fired under firing conditions of 1350 to 1380 ° C and an oxygen concentration of more than 1%.
This is to obtain a Mn-Zn ferrite satisfying μi ≧ 4000 at 0,500 kHz.

In the present invention, the reason for limiting the amounts of the subcomponents is that if the amount of CaO, Bi2O3, and SiO2 is less than a predetermined amount, the loss increases, and if the amount of CaO is more than a predetermined amount, the magnetic permeability becomes low. If the amount is more than the fixed amount, abnormal sintering occurs, which is not preferable.

[0009]

EXAMPLE 53% by mol of Fe2O3, 27% by mol of MnO and 20% by mol of ZnO were used as main components.
A raw material containing Bi2O3 and SiO2 in the amounts shown in Table 1 was prepared, calcined at 850 ° C. for 2 hours, then pulverized by a ball mill for 8 hours, and compression-molded into a ring shape.
Calcination was carried out at an oxygen concentration of 5% for 5 hours. Further, in the same sample preparation step as in the example, each sample was prepared by changing the firing conditions (the firing temperature and the firing atmosphere). 100 kh of the core
z and initial permeability μi at 500 kHz, t at 100 kHz
An δ / μi and μi at 100 kHz are A, and 50
When μi at 0 kHz is B, an initial magnetic permeability μ of 500 kHz with respect to 100 kHz represented by (A−B) / A
Table 1 shows the rate of change ｉμi / μi of i. In Table 1, those within the scope of the present invention are examples, and those outside the scope are comparative examples.

[0010]

[Table 1]

FIG. 1 shows the frequency characteristics of the magnetic permeability of the embodiment (sample No. 8) and the comparative example (sample No. 10). As shown in FIG. 1 and Table 1, it is understood that the example of the present invention is a material having high magnetic permeability even at a high frequency. At the same time, it is understood that the material has a small loss.

[0012] Further, it contains CaO, Bi2O3, Si
O2 is 0.05 to 0.12% by weight of CaO, Bi2O
3 is 0.04% by weight or less (however, not including 0% by weight), and SiO2 is 0.01 to 0.02% by weight (however,
(Excluding 0.01% by weight), it was found that characteristics almost similar to those of the examples shown in Table 1 could be obtained.

However, if the firing temperature is in the range of 1350 to 1380 ° C., the oxygen concentration at that time needs to exceed 1%. When the oxygen concentration is 1% or less, a decrease in the initial permeability at a frequency of 500 kHz and a relative loss coefficient tan δ
/ Μi.

[0014]

According to the present invention, it is possible to obtain a Mn-Zn ferrite having high magnetic permeability up to high frequencies and small loss even at high frequencies.

[Brief description of the drawings]

FIG. 1 is a graph showing frequency characteristics of magnetic permeability of an example according to the present invention and a comparative example.

Claims (1)

(57) [Claims] 1. An Mn—Zn ferrite comprising 0.05 to 0.12% by weight of CaO as an auxiliary component,
3 is 0.04% by weight or less (excluding 0% by weight), and SiO2 is 0.01 to 0.02% by weight (however,
0.01% by weight) and a sintering temperature of 1350
１３1380 ° C., sintering under sintering conditions exceeding 1% oxygen concentration, the initial magnetic permeability μi is 500 at a frequency of 100 kHz.
A method for producing Mn—Zn ferrite, which is 0 or more and 4000 or more at 500 kHz.