JPH03248403A - Low-loss ferrite - Google Patents

Abstract

PURPOSE:To enable content of SiO2 to be optimum and obtain a low-loss ferrite with a small amount of power loss over a frequency range of 25-300kHz by including Fe2O3, MnO, and ZnO as main constituents and a specific amount of CaO as a sub-constituent simultaneously and then including a specific amount of one type out of Nb2O5, Ta2O5, and TiO2. CONSTITUTION:Fe2O3, MnO, and ZnO are included as main constituents and 200-1000ppm CaO and 50-150ppm SiO2 are included as sub-constituents simultaneously. And then, at least one type out of 200-1500ppm Nb2O5, 200-1500ppm Ta2O5, and 1000-2000ppm TiO2 is included. By enabling 50-150ppm SiO2 to be included in an Mn-Zn ferrite, a ferrite with a low loss at a frequency range of 25kHz-300 kHz can be obtained. After a raw material whose main constituents are Fe2O3, MnO, and ZnO is mixed by a ball mill, it is tentatively baked, a proper amount of CaCO3, SiO2, and Nb2O5 are added compositely as sub-constituents, and grinding is performed by a ball mill. After this ground raw material is dried, a binder is added to form a grain, perform forming, and perform baking.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an Mn-Zn-based low-loss ferrite suitable for use as a magnetic core for switching power supplies and the like.

(Prior art) Conventional n-Zn based low loss ferrites include Cab, S
in.

It is known that Nb2O3, V,
There were some that added 05°TiO□, Ta205, etc.

For example, in Japanese Patent Application Laid-Open No. 58-114401, MnO
, ZnO, Fe, 0. is the main component, and CaO is 0.04
-0.2% by weight, Nb2O, 0.1% by weight without O
An ultra-low loss ferrite for a power source is disclosed below, which is characterized in that it contains 0.05% by weight or less of 5un2 as a subcomponent in a composite manner.

Also, in JP-A No. 63-62206.

The main components are MnO, ZnO, Fs, and O, and Ti
e, 500~6000PPmwTazOi 100~
An ultra-low loss ferrite for power supply is disclosed, which is characterized by containing 2,000 ppm of SiO, 150 to 270 ppm of SiO, and 500 to 2,000 ppm of CaO as subcomponents.

(Problem to be solved by the invention) When trying to obtain a low-loss ferrite with small power loss in the frequency range of 25kHz to 300kl (z), 5un2
It has been difficult to achieve low loss over a wide range of 500 ppm or less.

For example, when Sin is 15Qppm or more, the firing temperature is 13
When the temperature was 00℃, the crystal grains were abnormally sintered, and on the contrary, 50pp
If the amount is less than +w, there is a problem that the sintered density cannot be increased.

The present invention focuses on the content of SiO□ and finds the optimum content.

(Means for solving the problems) The present invention is as follows. The main components are Fe2O3, MnO, and ZnO,
200-11000pp of CaO and SiO as subcomponents
, containing 50 to 150 ppm of Nb2052 at the same time.
00~1500pp rin, Ta2O, 2oo~1500P
It contains at least one of the following.

In other words, the present invention requires Ca and Si, and further includes Nb.

In An-Zn ferrite containing at least one of Ta and Ti, 50 to 150 pp as 5in2 amount
- By containing it, it was possible to obtain ferrite with low loss in the frequency band of 25 kHz to 300 kHz.

(Example) Fe, 03 (53.5 mo1%), Mn0 (37.5 m
After mixing the raw materials whose main components are Zn0 (9,0 + mo1%) in a ball mill, they are calcined at 900 ° C.
As subcomponents, appropriate amounts of CaCO3, Sin, 1100 ppm and Nb, 500 ppm of Nb, 0° were added in a combined amount to give 300 ppm in terms of CaO, and the mixture was pulverized in a ball mill for 12 hours. However, for subcomponents such as Cab and Sin, which were previously contained in the raw materials, the amounts added after pre-calcination were reduced by that amount, so that the overall proportions matched the above-mentioned proportions. After drying this pulverized raw material, add 1 binder
, 0tzt% was added, and the mixture was granulated and molded. This compact was fired at a temperature of 1300°C and a firing atmosphere of 1% oxygen partial pressure.
Baked for an hour. The shape of the fired body was a ring with an outer diameter of 25 m, an inner diameter of 15 m, and a height of 7.5 cm.

In the same sample preparation process as in Example 1, each sample was prepared with different additives.The results are shown in Table 1.

Table 1 also shows that in the sample preparation process similar to Example 1, CaO
is 300 ppm, Nb2O, is 500 ppm, and S
The first graph shows the power loss when changing the amount of addition of in.
The reasons for limiting the range of each component in the six inventions shown in the figure are as follows. If the CaO content is less than 200pp, electrical resistance decreases, eddy current loss increases in the high frequency region, and power loss increases.
When the amount is more than p, power loss increases and magnetic permeability decreases rapidly. If SiO□ is less than 50 ppm, the sintered density will not increase, and if it is more than 150 ppm, abnormal sintering will occur, increasing loss and decreasing magnetic permeability and Q value. In addition, the reason for limiting the ranges of Nb, O3, Ta, Os, and Tie is that Nb, O, and T
If a, O, is larger than the range of the present invention, abnormal sintering occurs, loss increases, and magnetic permeability and Q value also decrease. Also,
When Nb, O, and Ta, 05 are less than the range of the present invention, electrical resistance decreases and loss increases. Also Tie,
was added to improve the temperature characteristics of power loss and achieve low loss over a wide temperature range, but the addition effect cannot be obtained at less than 1000 pps+, and the loss increases when it is more than 20000 pps@.

(Effects of the Invention) According to the present invention, by optimizing the content of SiO2, it is possible to obtain a low-loss flight with small power loss in the frequency range of 25 to 300 k)Iz.

[Brief explanation of drawings]

FIG. 1 is a graph of power loss when the amount of SiO□ added is changed.

Claims (1)

[Claims] 1. Fe_2O_3, MnO, ZnO as main components, CaO200-1000ppm, SiO_2 as subcomponents
Contains 50 to 150 ppm at the same time, and further contains Nb_2O_5
200~1500ppm, TA_2O_5200~15
00 ppm, TiO_21000 to 20000 ppm.