JP3099245B2 - Method for producing low-loss oxide magnetic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a low-loss oxide magnetic material.

[0002]

2. Description of the Related Art In a conventional transformer for a switching power supply, a switching frequency of about 200 kHz is exclusively used, and Mn-Zn spinel type ferrite is used. In recent years, to reduce the size and weight of switching power supplies, the switching frequency was 200 kHz.
Use at the above high frequencies is becoming common.

[0003]

However, the conventional Mn-
When a Zn-based spinel-type oxide magnetic material is used as a magnetic core material of a transformer for a switching power supply having a switching frequency of 200 kHz or more, there is a disadvantage that iron loss is large and heat is generated, thereby significantly deteriorating the performance of the power supply. The cause is speculated as follows. Conventional ferrite sintered bodies are prepared by mixing iron, manganese, and zinc oxide powders in a ball mill, etc., pre-firing, passing through a fine pulverizing process and a granulating process, and pressing to produce a green compact. Are obtained by firing this green compact. By the way, this sintered body is made of SiO ₂ and Ca during the mixing or pulverizing step.
Generally, O or other trace elements are added, and after cooling, the SiO ₂ , CaO, and other trace additive elements are present as grain boundary phases in the Mn—Zn ferrite crystal grain boundaries. The grain boundary phase has a function of significantly improving the electric resistance of the ferrite and reducing the eddy current loss generated in the ferrite. However, the amount of addition of SiO ₂ , CaO and other trace additives in the ferrite sintered body described above is extremely small, at most several thousand ppm. In addition, since each component is added alone, the formation of the grain boundary phase is non-uniform, and furthermore, there are many places where the grain boundary phase does not exist. Not only increases the eddy current loss, but also deteriorates the sinterability, does not allow sufficient atom diffusion and densification, and increases the overall power loss. It is.

[0004] Therefore, the technical problem of the present invention is to form a microstructure having a fine and uniform crystal grain size so that a frequency of 2 is obtained.
An object of the present invention is to provide a method for manufacturing a low-loss oxide magnetic material that can reduce iron loss even when used at a high frequency of 00 kHz or more.

[0005]

Means for Solving the Problems The present inventors have conducted various studies to overcome the above-mentioned drawbacks.
By adding a glass phase containing O ₂ , CaO, HfO ₂ as a main component, or a powder of a crystal phase or a mixed phase thereof, or a powder containing at least one of Fe ₂ O ₃ , MnO, and ZnO to the powder. It has been found that a power loss can be remarkably reduced, and a low-loss oxide magnetic material that can be used even at a high frequency of several hundred kHz or more can be obtained. According to the present invention, in a method for producing a Mn-Zn-based ferrite having a spinel-type crystal structure by powder metallurgy, the Mn-Zn-based ferrite raw material powder has
A method for producing a low-loss oxide magnetic material characterized by adding at least one of a glass phase containing iO ₂ , CaO, and HfO ₂ , and a powder of a mixed phase thereof. According to the invention, said additive powder is Fe
_A method for producing a low-loss oxide magnetic material characterized by adding an additive powder containing at least one of ₂ O ₃ , MnO, and ZnO. Further, according to the present invention, there is provided a method for producing a low-loss oxide magnetic material, wherein the content of SiO _{2 in} the additive powder is 5 to 60 mol% or less. According to the present invention, there is provided a method for producing a low-loss oxide magnetic material, wherein the content of HfO _{2 in} the additive powder is 90% or less. In the present invention, S
iO ₂ , CaO, HfO ₂ as a main component, Fe ₂ O ₃ ,
The glass phase containing MnO, ZnO, or the crystal phase, or the powder of the mixed phase thereof is almost the same as the composition of the grain boundary phase in the crystal, so that the uniformity of the grain boundary phase can be improved. In addition to these results, these powders become nuclei of the liquid phase during sintering, and these nuclei are uniformly dispersed in the green compact, so that uniform grain boundaries can be formed at the crystal grain boundaries of the sintered body. Because the structure was homogenized, the sinterability was significantly improved.
It is presumed that eddy current loss and hysteresis loss were reduced due to the promotion of atom diffusion and densification. In the present invention, SiO _2, CaO, glass phase consisting of HfO _2, crystal phase, in addition powder comprising one at least selected from these mixed phase powder, had a composition of SiO ₂ and 5 to 60 mol% is 5mol % Or less
_{2 The} amount is too small, so that not only a grain boundary phase exhibiting good core loss characteristics cannot be obtained, but also the sinterability is reduced, so that 5 mol% is used.
In addition, in the region exceeding 60 mol%, the amount of SiO ₂ is too large, abnormal grain growth occurs, and the core loss characteristics are remarkably deteriorated. In the present invention, at least one of a glass phase, a crystal phase composed of SiO ₂ , CaO, and HfO ₂ , and a mixed phase powder thereof, has a HfO ₂ composition exceeding 90 mol% in a region exceeding 90 mol%.
This is because an excessive amount of O ₂ causes abnormal grain growth and remarkably deteriorates core loss characteristics.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

(Example 1) Fe ₂ O ₃ , MnO, ZnO
Weighed to 53.5 mol%, 38 mol%, and 8.5 mol%, and mixed with a ball mill.
It was calcined at ° C. (referred to as I material). In addition, SiO ₂ , CaO,
After weighing HfO ₂ , Fe ₂ O ₃ , MnO, ZnO and HfO ₂ as shown in Table 1 and mixing them in a ball mill, the powder was molded at ² ton / cm ² and 500 to 1000
Fired at ℃. Further, these powders were pulverized with a ball mill, and the obtained powder was used as II material. (I-1 to II-5, a total of 5 types)
%, And mixed and pulverized with a ball mill. Next, after the obtained powder is molded at ² ton / cm ² ,
The main firing was performed at 0 ° C. Further, as a comparison material, SiO ₂ and CaO were added to the powder of the I material at 0.02 wt% and 0.05 wt%, respectively.
%, And then mixed and pulverized in a ball mill as in the above, molded and fired. Table 2 shows the most excellent power loss characteristics among the sintered bodies obtained when the respective II materials were added and the firing conditions were changed, in comparison with comparative materials. SiO ₂ , CaO, Fe ₂ O ₃ , MnO, Zn according to Embodiment 1 of the present invention
It can be seen that the addition of the calcined powders of O and HfO ₂ shows a smaller power loss than the comparative example.

[0008]

[Table 1]

[0009]

[Table 2]

[0010] (Example 2) II-1 material in Example 1, and, II-2 material, and, in Example 1 SiO ₂ 5mol% -CaO75mol% obtained in the same process as -HfO ₂ 20Mo
l%, SiO ₂ 30 mol% -CaO 50 mol% -HfO
₂ 20 mol%, SiO ₂ 40 mol% -CaO 40 mol%
_{-HfO 2 20mol%, SiO 2 60mol} % -CaO
20 mol% -HfO ₂ 20 mol%, SiO ₂ 65 mol%
-CaO 15 mol% -HfO obtain a sintered body in the same manner as with Example 1 added to the I material was obtained ₂ 20 mol% of the powder each in 0.05～0.2Wt% Example 1. FIG. 1 shows the power loss measurement results. In FIG. 1, curve 1 shows the power loss of the sintered body according to Example 2 of the present invention, and curve 2 shows the power loss measurement result of the conventional product. It can be seen that the power loss of SiO ₂ amount is superior to conventional products in the range of 5 to 60 mol% in the baking powder SiO ₂ -CaO.

[0011] (Example 3) II-1 material in Example 1, and, II-2 material, _{and, SiO 2 8mol% -CaO72mol% -HfO} 2 20mo obtained in the same manner as in Example 1 preparation
_{l%, SiO 2 8mol% -CaO} 52mol% -HfO
₂ 40 mol%, SiO ₂ 8 mol% -CaO 32 mol%
HfO ₂ 60 mol%, SiO ₂ 8 mol% -CaO12mo
l% -HfO ₂ 80 mol%, SiO ₂ 8 mol% -CaO
Each 0.05 to 2mol% -HfO ₂ 90mol% of powder
0.2 wt% was added to the I material obtained in Example 1 to obtain a fired body in the same manner as in Example 1. FIG. 2 shows the power loss (1 MHz-500 G at 60) when the mixing ratio of the HfO ₂ powder was changed.
° C). For comparison, the power loss of the conventional product is also shown. In FIG. 2, curve 3 shows the characteristic according to the first embodiment, and curve 4 shows the characteristic according to the comparative example. HfO ₂ powder mixing ratio is 9
It can be seen that at 0 mol% or less, a power loss superior to the conventional ferrite as a comparative material is exhibited.

Example 4 FIG. 3 shows the results of measuring the power loss frequency dependence of a sintered sample and a comparative material obtained by using the powder containing 30 mol% of HfO ₂ powder shown in Example 3. . FIG. 3 shows that the Mn− according to Example 4 of the present invention
It can be seen that Zn ferrite (curve 5) shows superior power loss in all frequency ranges as compared with the conventional material (curve 6) as a comparative material.

Example 5 FIG. 4 shows the results of measuring the power loss temperature dependence of a sintered sample and a comparative material obtained using the powder containing 30 mol% of the HfO ₂ powder shown in Example 3. . FIG. 4 shows that Mn—Z according to the fifth embodiment of the present invention.
It can be seen that n-ferrite (curve 7) shows superior power loss over the entire temperature range as compared with the conventional product (curve 8) as a comparative material.

Example 6 The II material shown in Example 1 (II-
1 to 5) were added to the I material at 0.05% by weight, mixed and pulverized by a ball mill, molded and fired. Table 3 shows SiO ₂ and C
aO, HfO ₂ and SiO ₂ , CaO, HfO ₂ , Fe
_This shows the specific resistance when the mixing ratio of ₂ O ₃ , MnO, and ZnO is changed. According to an embodiment of the present invention, SiO ₂ , CaO,
It can be seen that the addition of the calcined powder of Fe ₂ O ₃ , MnO, ZnO, HfO ₂ shows a higher specific resistance.

[0015]

[Table 3]

[0016]

As described above, according to the present invention, M
In a method of producing n-Zn ferrite by a usual powder metallurgy method, a powder of a glass phase or a crystal phase composed of SiO ₂ and CaO, and a powder of a mixed phase thereof, and further containing Fe ₂ O ₃ , MnO, ZnO, Or HfO
By adding the powder containing ₂ , the power loss is remarkably improved, and when incorporated in a switching power supply or the like, the calorific value is reduced, and a low-loss oxide magnetic material exhibiting excellent power supply characteristics is obtained. This is presumably because the improvement of the uniformity of the grain boundary phase in the Mn-Zn ferrite produced high characteristics.

[Brief description of the drawings]

[1] shows the relationship between the power loss at the time of changing the amount of SiO ₂ SiO ₂ -CaO calcined powder in Example 2. (1MHz-500G at 60 ℃)

FIG. 2 shows SiO ₂ —CaO—HfO ₂ in Example 3.
It shows the relationship with the power loss when the amount of HfO _{2 in the} fired powder is changed. (1MHz -500G at 6
0 ℃)

FIG. 3 shows SiO ₂ —CaO—Fe ₂ O in Example 3.
_{7 is a} graph comparing the power loss frequency dependence of a sample to which a sintered powder of _3- MnO-ZnO is added with a comparative example. (50
0G at 60 ℃)

FIG. 4 shows SiO ₂ —CaO—Fe ₂ O in Example 3.
_{7 is a} graph comparing the power loss temperature dependence of a sample to which a sintered powder of _3- MnO-ZnO is added with that of a comparative example. (1MHz
-500G)

Claims (4)

(57) [Claims] 1. Mn-Zn having a spinel type crystal structure
In a method of producing a ferrite based on powder metallurgy, SiO ₂ , Ca
A method for producing a low-loss oxide magnetic material, comprising adding an additional powder containing at least one of a glass phase containing O, HfO ₂ , a crystal phase, and a powder of a mixed phase thereof. 2. The method for producing a low-loss oxide magnetic material according to claim 1, wherein said additive powder is Fe ₂ O ₃ , MnO,
A method for producing a low-loss oxide magnetic material comprising at least one kind of ZnO. 3. The method for producing a low-loss oxide magnetic material according to claim 1, wherein the content of SiO _{2 in} said additive powder is 5%.
A method for producing a low-loss oxide magnetic material, wherein the content is at most 60 mol%. 4. The method for producing a low-loss oxide magnetic material according to claim 1, wherein the content of HfO _{2 in} said additive powder is 9%.
A method for producing a low-loss oxide magnetic material, which is 0% or less.