JP2551491B2 - Low loss oxide magnetic material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a low-loss oxide magnetic material used for a power transformer or the like.

[Prior Art] In conventional transformers for switching power supplies, a switching frequency of about 10 to 200 kHz is used exclusively, and a low loss oxide magnetic material to meet this is 30 to 30% as a main component. 40 mol% manganese monoxide (Mn
O), 5 to 15 mol% zinc oxide (ZnO) and the balance ferric oxide (Fe ₂ O ₃ ), and 0.04 to 0.15 wt% calcium oxide (CaO) and 0.010 to 0.100% as auxiliary components. Mn-Zn-based spinel ferrite containing% by weight of silicon dioxide (SiO ₂₎ have already been developed.

[Problems to be Solved by the Invention] In recent years, in order to reduce the size and weight of switching power supplies,
It is becoming common to use at high switching frequencies of 100 kHz and above.

However, when a low-loss oxide magnetic material having a conventional component is used as the magnetic core material of a transformer for switching power supplies with a switching frequency of 100 kHz or more, power loss due to iron loss is large, and the resulting heat generation causes the temperature to rise above the allowable temperature. There was a drawback that it went up and damaged the transformer itself and its peripheral parts and could not be used.

Therefore, the technical problem of the present invention is to provide a low loss oxide magnetic material that can be put to practical use by reducing iron loss even if it is used at a high frequency of 100 kHz or more, and therefore suppressing heat generation below the allowable temperature. is there.

[Means for Solving the Problem] According to the present invention, 30 to 42.0 mol% of manganese monoxide (MnO) as a main component, 4.0 to 19 mol% of zinc oxide (ZnO), and the balance of ferric oxide (MnO) ( Fe ₂ O ₃ ) and 0.020 to 0.15% by weight of calcium oxide (CaO) as an auxiliary component, and 0.005
A low loss oxide magnetic material is obtained which is characterized by containing ˜0.10% by weight of silicon dioxide (SiO ₂ ) and 1.00% by weight or less of hafnium oxide (HfO ₂ ) as an additive.

According to the present invention, in the low loss oxide magnetic material, as an additive, zirconium oxide (ZrO ₂ ) of 0.30 wt% or less and vanadium oxide (V ₂ O ₂ of 0.20 wt% or less are further added.
₅ ) and 0.30% by weight or less of at least one of tantalum oxide (Ta ₂ O ₅ ) is obtained.

According to the present invention, any one of the above-mentioned low loss oxide magnetic materials further contains at least one of 0.50 wt% or less Al ₂ O ₃ and 0.30 wt% or less TiO ₂ as an additive. A low loss oxide magnetic material is obtained.

Here, in the present invention, 1.00 wt% or less of hafnium oxide (HfO ₂ ) is used as an essential additive because the above appropriate amount of this element suppresses coarse crystal grain growth, and
This is because it has the effect of increasing the specific resistance of the grain boundaries by precipitating at the grain boundaries.

Further, in the present invention, 0.30% by weight as an optional additive
Below, at least one of zirconium oxide (ZrO ₂ ), 0.20 wt% or less vanadium oxide (V ₂ O ₅ ) and 0.300 wt% or less tantalum oxide (Ta ₂ O ₃ ) is used. , As well as hafnium oxide (HfO ₂ ), it suppresses the growth of coarse crystal grains and has the effect of precipitating at the grain boundaries and increasing the specific resistance of the grain boundaries. This is because when the addition amounts of tantalum oxide and tantalum oxide exceed the upper limits of the appropriate amounts of the respective components, remarkable grain growth occurs, which is not economical and the power loss characteristic deteriorates.

Further, in the present invention, in addition to the above essential additives and optional additives, at least 0.50 wt% or less of aluminum oxide (Al ₂ O ₃ ) and 0.30 wt% or less of titanium dioxide (TiO ₂ ) are added as additives. Aluminum oxide (Al ₂ O ₃ ) and titanium dioxide (TiO ₂ ) are included as one type.
The reason is that, within the above upper limit value, the solid solution occurs in the crystal, the structure in the crystal grain is made uniform, and the resistance inside the crystal is increased.

However, if this upper limit is exceeded, the power loss will increase significantly.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

(Example 1) as a main component, 53.0 mole% of ferric oxide (Fe ₂ O _3), 37
It contains mol% manganese monoxide (MnO) and 10.0 mol% zinc oxide (ZnO), with 0.025 wt% silicon dioxide (SiO ₂ ) and 0.043 wt% calcium oxide (C
aO) and hafnium oxide (HfO ₂ ) as an additive component
Was added, and these were mixed, pre-fired, pulverized, granulated, and molded and pressed, then the oxygen partial pressure was 0.1 at% and the temperature was 1150 ° C.
And sintered to obtain an oxide magnetic material.

FIG. 1 shows the temperature T when the added amount of hafnium oxide (HfO ₂ ) is used as a parameter for the obtained oxide magnetic material.
It is a figure showing the relation between [° C] and power loss P _B [kW / m ³ ]. In Fig. 1, the power loss P _B [kW / m ³ ] is shown when the frequency is 1 MHz and the maximum magnetic flux density B _m is 500 G. In Fig. 1, curve 1 is hafnium oxide (HfO ₂ )
Curve 2 with 0.20 wt% hafnium oxide (HfO ₂ ), curve 3 with 0.40 wt% hafnium oxide (HfO ₂ ), curve 4 with 0.60 wt% hafnium oxide. When (HfO ₂ ) is added, curve 5
When 0.80% by weight of hafnium oxide (HfO ₂ ) is added,
Curve 6 is when 1.00 wt% hafnium oxide (HfO ₂ ) is added, and curve 7 is 1.20 wt% hafnium oxide (HfO ₂ ).
The characteristics with the addition of are shown. From Fig. 1, when the frequency is 1MHz, the power loss P _B is about 60 ℃ regardless of whether hafnium oxide (HfO ₂ ) is added or not.
Has a minimum value of. Then, as the amount of hafnium oxide (HfO ₂ ) added increases, the power loss P _B decreases, and when the amount added is 0.60 wt%, the power loss P _B becomes the smallest, and the amount added increases further. Power loss
When P _B increases and the amount of addition exceeds 1.20 wt%, the power loss P _B becomes larger than when it is not added.

From the above, hafnium oxide (HfO ₂ ) at a frequency of 1 MHz
It can be seen that the power loss P _B becomes smaller when 1.00 wt% or less (not including 0%) is added than when not added.

Table 1 shows the oxide magnetic material obtained in Example 1 (0.025% by weight of silicon dioxide (SiO ₂ ) as an auxiliary component,
0.043 wt% calcium oxide (CaO) and 0.060 wt%
Of hafnium oxide (HfO ₂ ) and conventional oxide magnetic material (0.025 wt.
₂ ) and 0.043% by weight of calcium oxide (CaO),
Hafnium oxide (HfO ₂ ) is not added) characteristics (initial permeability μi, saturation magnetic flux density B ₁₅ (magnetic flux density at magnetizing force 15 [Oe]) [G], residual magnetic flux density Br [G], coercive force Hc [O
e] is shown. The main components are all ferric oxide (Fe ₂ O ₃ )
53.0 mol%, manganese oxide (MnO) 37.0 mol% and zinc oxide (ZnO) 10.0 mol%.

As is clear from Table 1, the characteristics of Example 1 of the present invention required for a magnetic core material for a switching power supply, for example, an initial permeability μi of 1000 or more and a saturation magnetic flux density of 50 or more.
It fully satisfies the characteristics of 00G and above.

From the above, hafnium oxide (HfO ₂ ) as an additive
Is sufficient to meet the various characteristics required as a magnetic core material for switching power supplies, and at a frequency of 200 kHz or more, the power loss P _B is, for example, about 0.60% by weight, compared with the case without addition, at a temperature of 60 ° C. It can be seen that 500kW / m ³ can be improved.

(Example 2) 53.0 mol% of ferric oxide (Fe ₂ O ₃ ) 3 based on an oxide magnetic material obtained by mixing, molding and firing oxide powder
A conventional low-loss oxide magnetic material containing 6.0 mol% manganese monoxide (MnO) and 11.0 mol% zinc oxide (ZnO) with calcium oxide (CaO) and silicon dioxide (SiO ₂ ) as auxiliary components. Component range (calcium oxide (CaO)
0.02-0.15% by weight, silicon dioxide (SiO ₂ ) 0.005-0.1
In the conventional low-loss oxide magnetic material, the content of which is zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ) and hafnium oxide (HfO ₂ ) in various proportions. As a comparative example 2, a plurality of low-loss oxide magnetic materials of Example 2 compositely added in Example 1, a conventional example in which the above-mentioned additives are not added, and a plurality of low-loss oxide magnetic materials in which the above-mentioned additives are added singly or in combination are manufactured. did. These Example 2,
In the trial production of the conventional example and the comparative example 2, the respective oxide raw materials were weighed and mixed in predetermined amounts, granulated and molded and pressed, and the oxygen partial pressure was 5.0 at% or less in the nitrogen gas atmosphere. A sample was obtained by firing at a temperature of 1300 ° C.

Table 2 shows sample Nos. 15 to 17 and Nos. 19 and 2 of Example 2 that were prototyped.
0,22,23,25,26, Sample No. 8 as a conventional example, and Comparative Example 2
Sample No.9 to No.14, No.18,21,24 of each, and the sample temperature of power loss P _B when the maximum magnetic flux density Bm is 1000 G at frequency 200 kHz Is the minimum value for.

According to Table ₂ , the power loss is reduced compared to Sample No. 8 of the conventional example by the combined addition of the additive zirconium dioxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ) and hafnium oxide (HfO ₂ ). You can see that

This is because in these additives, ZrO ₂ and HfO ₂ precipitate at the grain boundaries of the low-loss oxide magnetic material, increasing the resistivity of the grain boundaries, and Al ₂ O ₃ forms a solid solution in the crystal. It is thought that there was an effect of increasing the resistivity in the crystal and making the crystal structure uniform, and the combined action of these increases the uniformity of the electromagnetic properties inside the structure and the resistivity of the entire structure. It is considered that the loss was reduced.

In addition, in Table ₂ , sample No. containing 0.40% ZrO ₂ was added.
It is considered that abnormal grain growth was observed in sample No. 21 containing 18,0% Al ₂ O ₃ 0.60% and sample No. 24 containing HfO ₂ 1.10, resulting in a large power loss.

Further, it can be seen that in Sample Nos. 9 to 14 in Table 2, the additive alone or two of them is 0%, and in this case as well, the power loss is large and the effect is small.

(Example 3) A conventional low-loss oxide magnetic material containing the same main component as in Example 2 and a conventional subcomponent range was further added with titanium dioxide (TiO ₂ ), vanadium pentoxide (V ₂ O ₅ ), And various low loss oxide magnetic materials of Example 3 in which various additives of hafnium oxide (HfO ₂ ) were added in various proportions were manufactured as trials. Various prototypes were made by combining an oxide magnetic material and a plurality of low-loss magnetic materials in which the above additives were added alone or in combination as Comparative Example 3.

In the prototypes of Example 3, the conventional example, and the comparative example 3, as in the case of Example 2, the respective oxide raw materials were weighed and mixed in a predetermined amount, granulated, molded and pressed, and in a nitrogen gas atmosphere, Samples were obtained by firing at a temperature of 1100-1300 ℃ with an oxygen partial pressure of 5.0 at% or less.

Table 3 shows sample Nos. 33 to 35, 37, 38, 4 of the prototyped Example 3.
0,41,43,44, the sample No.8 as a conventional example, and the samples No.27 to 32, No.36,39,42 of Comparative Example 3, the contents of the respective subcomponents and additive components and , Shows the minimum value of the power loss with respect to the sample temperature when the maximum magnetic flux density Bm is 1000 G at a frequency of 200 kHz.

According to Table 3, titanium dioxide (Ti
O ₂ ), vanadium pentoxide (V ₂ O ₅ ), and hafnium oxide (HfO ₂ ) were added in combination to produce a conventional comparative sample No. 2
It can be seen from Fig. 8 that the power loss has decreased. this is,
It is considered that the additives, V ₂ O ₅ and HfO ₂ were precipitated in the grain boundaries to increase the resistivity of the grain boundaries and uniform the crystal structure. Similarly, it can be considered that the power loss is reduced.

In Table 3, sample No. 39 containing 0.30% by weight of TiO ₂ was added.
And in sample No. 42 with 1.10 wt% HfO ₂ added,
It is considered that abnormal grain growth was observed, which resulted in a large power loss.

Sample Nos. 27 to 32 in Table 3 have 0% of each additive alone or two, and in this case as well, it is understood that the power loss is large and the effect is small.

Table 4 shows the conventional sample No. 8 and the sample of Example 2 of the present invention.
Regarding No. 15, Table 5 shows the initial permeability μ, the saturation magnetic flux density B ₁₅ , the residual magnetic flux density Br, and the resistivity ρ of the conventional sample No. 8 and the sample No. 33 of Example 3, respectively. It is a comparison of the respective electromagnetic characteristics.

In Tables 4 and 5, for μ, B ₁₅ and Br, sample N
No. 8 and No. 15 or Sample No. 33 are comparable to each other, and only the resistivity is No. 15 of Example 2 or No. 33 of Example 3, respectively. The value is more than double. It is understood that this drastic improvement in resistivity is the main cause of the reduction in eddy current loss.

As described above, it was confirmed that the power loss of 100 kHz or more was reduced by Examples 2 and 3 of the present invention, and an excellent low loss oxide magnetic material was obtained as a transformer core material for a switching power supply at a high frequency of 100 kHz or more. .

(Example 4) 53.0 mol% of ferric oxide (Fe ₂ O ₃ ) as a main component, 39.
0 mol% of manganese monoxide (MnO) and 8.0 mol% of zinc oxide (ZnO) were added as secondary components to silicon dioxide (Si
O ₂ ), calcium oxide (CaO), hafnium oxide (Hf
O ₂ ), zirconium oxide (ZrO ₂ ), aluminum trioxide (Al ₂ O ₃ ), vanadium pentoxide (V ₂ O ₅ ), alone or in combination, mixed, granulated, molded and pressed, then nitrogen Sintering was performed in a gas atmosphere at an oxygen partial pressure of 5.0 at% or less and at the optimum sintering temperature of 1100 to 1300 ° C for each composition.

Table 6 shows that the main component is 53.0 mol% ferric oxide (Fe ₂ O
₃ ), 39.0 mol% manganese monoxide (MnO) and 8.0 mol%
Of high permeability Mn-Zn ferrite containing zinc oxide (ZnO), added with silicon dioxide (SiO ₂ ) and calcium oxide (CaO) as subcomponents, and further hafnium oxide (HfO ₂ )
And zirconium oxide (ZrO ₂ ), and aluminum oxide (Al ₂ O ₃ ) and vanadium pentoxide (V ₂ O ₅ ) as selective components
The power loss (iron loss) is 60 when the frequency is 1MHz and the maximum magnetic flux density B is 500G (Gauss) when combined with
The value for each composition at around ℃ is shown.

The composition and the power loss (iron loss) of the present invention will be described with reference to Table 6.

Table 6 shows the relationship between the added amount of each subcomponent and the power loss (iron loss).

As shown in Table 6, the power loss can be reduced by the combined addition of hafnium dioxide (HfO ₂ ), zirconium dioxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), and vanadium pentoxide (V ₂ O ₅ ). It is lower than that of the lossy oxide magnetic material, and the characteristic value is improved by about 30% compared to the conventional value.

Hafnium oxide (HfO ₂ ) 1.10 wt% addition (Sample No. 5
7), Zirconium dioxide (ZrO ₂ ) 0.40 wt% added (Sample No. 60), aluminum oxide (Al ₂ O ₃ ) 0.60 wt% added (Sample No. 63), vanadium pentoxide (V ₂ O ₅ ) 0.25 wt% added In (Sample No. 66), abnormal grain growth was observed in the crystal grains, the resistivity ρ also deteriorated, and the power loss increased.

(Example 5) In the same manner as in Example 4, 53.0 mol% ferric oxide (Fe ₂ O ₃ ) and 39.0 mol% manganese monoxide (Mn) were used as main components.
O) and 8.0 mol% of zinc oxide (ZnO), as secondary components, silicon dioxide (SiO ₂ ), calcium oxide (CaO),
Hafnium oxide (HfO ₂ ), zirconium oxide (ZrO ₂ ),
In addition, aluminum oxide (Al ₂ O ₃ ) and titanium dioxide (TiO ₂ ) as selective components are added individually or in combination, mixed, granulated, molded and pressed, then in a nitrogen gas atmosphere,
Sintering was performed at an optimum sintering temperature of 1100 to 1300 ° C for each composition with an oxygen partial pressure of 5.0 at% or less.

Table 7 shows that the main component is 53.0 mol% ferric oxide (Fe ₂ O
₄ ) Containing 39.0 mol% manganese monoxide (MnO), with silicon dioxide (SiO ₂ ) and calcium oxide (Ca
O) as a base, and when hafnium oxide (HfO ₂ ) and zirconium oxide (ZrO ₂ ) and aluminum oxide (Al ₂ O ₃ ) and titanium dioxide (TiO ₂ ) as selective components are added in combination, the frequency is The power loss (iron loss) at 1MHz and operating magnetic flux density B of 500G (Gauss) is shown for each composition near 60 ° C.

7th which shows the value of the composition of this invention, and electric power loss (iron loss)
The table will be described. Table 7 shows the relationship between the added amount of each subcomponent and the power loss. From Table 7, hafnium oxide (Hf
It can be seen that the power loss is improved by the combined addition of O ₂ ), zirconium oxide (ZrO ₂ ), aluminum oxide (Al ₂ O ₃ ), and titanium dioxide (TiO ₂ ). In addition, the power loss is, for example, as described above, the frequency is 1 MHz and the maximum magnetic flux density is 5
The measured values at 00G (Gauss) are shown, but at frequencies above 100kHz, similar power loss is observed.

Hafnium oxide (HfO ₂ ) 1.10 wt% addition (Sample No. 8
5), 0.40 wt% zirconium oxide (ZrO ₂ ) added (Sample No. 88) 0.60 wt% aluminum oxide (Al ₂ O ₃ ) added (Sample No. 91), 0.35 wt% titanium dioxide (TiO ₂ ) added (Sample No. 94) In (), abnormal grain growth was observed in the crystal grains, the resistivity ρ also deteriorated, and the power loss increased.

Table 8 shows a comparison of the initial magnetic permeability μ, the saturation magnetic flux density B ₁₅ , the residual magnetic flux density Br, and the specific resistance ρ between the sample number 83 in Example 5 and the conventional composition (sample numbers 47 and 71). .

Table 8 shows that for sample No. 55 in Example 4 and the conventional composition (Sample No. 44), the initial permeability μ and the magnetizing force were 15 Oe.
The values of the saturation magnetic flux density B ₁₅ , the residual magnetic flux density Br, the coercive force Hc and the specific resistance ρ are shown below. The specific resistance value of the low loss magnetic material according to the present invention is the same as that of the conventional low loss magnetic material. In comparison, 20
It is more than twice as high.

Further, in Table 8, comparing the characteristics of the sample No. 83 of Example 5 according to the present invention and the conventional sample (Sample No. 72), it can be seen that the specific resistance ρ is about 20 times or more.

In Examples 4 and 5, sintering was performed at an optimum temperature in a nitrogen gas atmosphere with an oxygen partial pressure of 0.5% within a range of 1100 to 1300 ° C.

(Example 6) 53.0 mole% of ferric oxide as main components (Fe ₂ O _3), 39.0
It contains mol% of manganese monoxide (MnO) and 8.0 mol% of zinc oxide (ZnO), and 0.010〜0.040wt% silicon dioxide (SiO ₂ ), 0.020〜0.15wt% calcium oxide ( CaO) as an additional component 0.01-0.80
Wt% hafnium oxide (HfO ₂ ), 0.005-0.300 wt%
Tantalum oxide (Ta ₂ O ₅ ) was added and mixed in a ball mill, then pre-fired, crushed, granulated and molded and pressed, and then the oxygen partial pressure was 0 to 3% (excluding 0). ), Temperature 1100
The oxide magnetic material was obtained by sintering at ~ 1300 ° C for 1-4 hours.

Table 9 shows the samples with the most excellent core loss characteristics among the oxide magnetic materials obtained by changing the sintering conditions for each composition, silicon dioxide (SiO ₂ ), calcium oxide (CaO), Hafnium oxide (HfO ₂ ), tantalum oxide (T
Temperature is 60 ℃ and magnetic flux is 500G when a ₂ O ₅ ) is used as a parameter.
Is the power loss P _B (mW / cc).

In Table 9, Sample No. 106 contains 53.0 mol% ferric oxide (Fe ₂ O ₃ ), 39.0 mol% manganese monoxide (MnO), and 8.0 mol% zinc oxide (ZnO) as main components. ,
0.030% by weight of silicon dioxide (SiO ₂ ) and 0.080% by weight of calcium oxide (CaO) are used as subcomponents, and hafnium oxide (H
fO _2), a conventional Mn-Zn ferrite power without the addition of tantalum oxide (Ta ₂ O _5).

It can be seen that the oxide magnetic material in the present invention is superior to the conventional one (Sample 106) in any case. In addition, silicon dioxide (SiO ₂ ) is 0.030% by weight, calcium oxide (CaO) is 0.060% by weight, and hafnium oxide (HfO ₂ ) is
Sample No. 102 prepared by adding 0.15 wt% and tantalum oxide (Ta ₂ O ₅ ) 0.05 wt% has a power loss P _B of about 1/2 that of conventional ferrite, which is remarkable. Realizes low loss characteristics.

[Effects of the Invention] As described above, according to the present invention, a Zn-Mn ferrite-based oxide magnetic material containing silicon dioxide and calcium oxide can be used as a HfO ₂ switching power supply transformer containing 1.00% by weight or less as an additive. To provide materials that satisfy the required characteristics sufficiently and reduce power loss even at high frequencies of 100 kHz or more as compared with conventional ones, and that are sufficiently suitable for the reduction in size and weight of switching power supplies as high-frequency magnetic core materials. You can

Further, according to the present invention, in this Zn-Mn ferrite-based oxide magnetic material, 0.30 wt% or less of zirconium oxide (ZrO ₂ ) and 0.30 wt% or less of tantalum oxide (Ta ₂ O ₃ By including at least one of the above), various characteristics required for the transformer for the switching power supply can be further improved.

Further, according to the present invention, in these Zn-Mn ferrite-based oxide magnetic materials, 0.50 wt% or less of Al ₂ O ₃ and 0.30
By including at least one kind of TiO _{2 in} a weight% or less,
Further, various characteristics such as power loss can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between temperature and power loss (P _B ) of the low-loss oxide magnetic material according to the example of the present invention. As a comparative example, a material (curve containing no hafnium oxide (HfO ₂ )) was added. 1) and 1.20 wt% hafnium oxide (HfO ₂ ) added material (curve 7) are also shown.

Front page continuation (72) Inventor Tetsuyoshi Chiba 6-7-1 Koriyama, Taichiro-ku, Sendai-shi, Miyagi Tokin Co., Ltd. (72) Inventor Tatsuya Chiba 6-7-1, Koriyama, Taichiro-ku, Sendai, Miyagi Stock Company Tokin

Claims (3)

(57) [Claims] 1. A main component containing 30 to 42.0 mol% of manganese monoxide (MnO), 4.0 to 19 mol% of zinc oxide (ZnO), and the balance of ferric oxide (Fe ₂ O ₃ ). 0.0 as an ingredient
20-0.15 wt% calcium oxide (CaO), 0.005-0.1
A low loss oxide magnetic material comprising 0% by weight of silicon dioxide (SiO ₂ ) and 1.00% by weight or less of hafnium oxide (HfO ₂ ) as an additive. 2. The low loss oxide magnetic material according to claim 1, further comprising 0.30% by weight or less of zirconium oxide (ZrO ₂ ), 0.20% by weight or less of vanadium oxide (V ₂ O ₅ ), And 0.30% by weight or less of tantalum oxide (Ta
A low-loss oxide magnetic material containing at least one of ₂ O ₅ ). 3. The low loss oxide magnetic material according to claim 1 or 2, further comprising at least one of 0.50 wt% or less Al ₂ O ₃ and 0.30 wt% or less TiO ₂ as an additive. A low loss oxide magnetic material characterized by the above.