JPH04260658A - Sintered ferrite and its production - Google Patents

Abstract

PURPOSE:To improve the magnetic characteristics of a sintered ferrite by incorporating a zirconium compound into a sintered ferrite and to provide a process for producing the above sintered ferrite. CONSTITUTION:The subject ferrite contains 0.01-0.1wt.% of a zirconium compound (in terms of zirconia). The sintered ferrite can be produced by compounding ferrite-constituting raw material powder with 0.02-0.5wt.% (based on the raw material powder) of an organo zirconium compound having >=1 zirconium atom and >=1 alkoxy group in one molecule to coat the surface of the raw material powder with the zirconium compound and forming and sintering the powder.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite sintered body whose magnetic properties are improved by incorporating a zirconium compound into the ferrite sintered body, and a method for producing the same.

0002

[Prior Art] Generally, ferrite sintered bodies are produced by mixing and pulverizing raw material powders such as iron oxide, manganese oxide, zinc oxide, etc., filtering, drying, and pre-calcining, and after crushing, additions are made to improve properties. The agent is added in the form of a powder, and this is used as a raw material powder. Next, a small amount of binder is added to this raw material powder, the powder is granulated, and then molded using a mold and sintered as a pressure body.

By the way, the oxides of iron, manganese, zinc, etc., which are the main components, turn into spinel during sintering, so even if the mixture is uneven, it is possible to make it into a uniform spinel phase by selecting the sintering conditions. Can be done. However, if the components that do not dissolve in the spinel phase are in a non-uniform mixing state in the raw material powder, they will be dispersed non-uniformly in the structure even after sintering, making it impossible to obtain a sintered body with good properties. .

[0004] In the conventional technology, regardless of whether the powder is mixed dry or wet, the trace additives are added in the form of powder, so it has been virtually impossible to mix them uniformly. A more uniform mixing state can be achieved by increasing the mixing time, but this will result in too much pulverization of the raw material powder, generating a large amount of fine powder, which will cause abnormalities in the structure of the sintered body. . For this reason, in mechanical mixing, uniform mixing leads to pulverization, so it is necessary to set optimal conditions, and uniform mixing is virtually impossible.

[0005]

[Problems to be Solved by the Invention] For example, in Mn-Zn ferrite for high frequency power transformers, Si of ZrO2
It is known that the simultaneous addition of O2 and CaO forms a grain boundary phase with high specific resistance, thereby increasing the resistance of the sintered body and having the effect of reducing iron loss. Uniform dispersion of ZrO2 into the grain boundary phase is necessary to reduce iron loss, but conventional mixing methods
Since rO2 is added as a powder, uniform dispersion is substantially difficult. Therefore, the present invention provides a sintered body that improves iron loss by uniformly dispersing ZrO2, which is effective in reducing iron loss, and a method for manufacturing the same.

[0006]

[Means for Solving the Problems] The present invention provides raw material powder using an organic zirconium compound having at least one zirconium atom and at least one alkoxy group in one molecule after crushing a pre-fired ferrite raw material sintered body. By coating the surface of the powder and dispersing zirconium atoms on the surface of the primary particles of the powder, Zr is uniformly applied to the grain boundary phase of the sintered body.
It disperses O2.

The manufacturing method according to the present invention also has the effect of improving moldability by forming a chemical bond between the powder surface and the compound door due to the alkoxy group, increasing the affinity between the binder and the ferrite powder. There is. When considering affinity with the binder, it is desirable to perform surface treatment before mixing the binder.

[0008] A specific example of the compound used in the surface treatment of the raw material powder in the present invention includes, for example, tetrapropoxyzirconium, but it goes without saying that the compounds are not limited thereto. Further, the surface treatment method is preferably carried out by dissolving these additives as they are in a suitable solvent, mixing them with the raw material powder, and using a ball mill or the like. The additive used at this time is 0.0% as the pure content of ZrO2 in the sintered body.
01 to 0.1% by weight is desirable.

That is, the ferrite sintered body of the first invention is
Zirconium compound as zirconia 0.01~0
．． The content is 1% by weight.

[0010] Furthermore, the method for producing a ferrite sintered body according to the second invention includes adding at least one zirconium atom and one alkoxy group in each molecule to the raw material powder constituting the ferrite.
An organic zirconium compound having 0.1 to 0.5% by weight is added to the raw material powder to coat the surface of the raw material powder, and then pressed and sintered.

[0011]

[Example] 53% iron oxide (fe2O3) in mol%, 35
% manganese oxide (MnO), 12% zinc oxide (ZnO)
Using a ball mill, alcohol is added to the Mn--Zn ferrite raw material powder, which is mixed and ground for 20 hours. Next, it is pre-fired in the air at between 800 and 100 degrees Celsius for 2 hours. After this, this powder was crushed in alcohol and tetra;propoxyzirconium (Zr(Oi-C3H7)
4) at 0.06% by weight, and SiO2, CaO
0.03% by weight of each were added, mixed in a ball mill for 1 hour, and surface treated. In addition, as comparison materials, powder and zirconium oxide without surface treatment were used at 0.07
A powder was also prepared by adding % by weight and mixing in a ball mill.

Next, 1% by volume of polyvinyl alcohol was added as a binder to this powder, and the mixture was further mixed for 30 minutes. Next, a granulated powder was produced using a spray dryer. Then, this was press-molded to produce a molded body having an outer diameter of 25 mm, an inner diameter of 15 mm, and a thickness of 5 mm. This was fired at 1350 degrees Celsius for 2 hours in an atmosphere with an oxygen partial pressure of 3% to produce a sintered body. Chemical analysis of the surface-treated powder sintered body revealed that it was zirconia (ZrO2).
0.048% by weight was detected. Regarding the magnetic properties of this sintered body, as shown in Table 1, a lower iron loss was obtained than that of a sintered body using surface-treated powder. Moreover, even when compared with a sintered body to which zirconia powder was added, good characteristics were reliably obtained.

[0013]

[Table 1]

[0014]

[Effects of the Invention] As described above, according to the present invention, Zr
Atoms can be uniformly dispersed on the surface of the primary particles of the raw material powder, and a ferrite sintered body with low core loss can be obtained.

Claims (2)

[Claims] 1. A ferrite sintered body containing substantially 0.01% to 0.1% by weight of a zirconium compound as zirconia. 2. Adding 0.02 to 0.5% by weight of an organic zirconium compound having at least one zirconium atom and at least one alkoxy group in one molecule to the raw material powder constituting the ferrite, A method for producing a ferrite sintered body, which comprises coating the surface of the raw material powder, followed by molding and sintering.