JP2007311387A - Oxide magnetic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxide magnetic material having high saturation magnetic flux density and high permeability in which increase in core loss is suppressed in the range of room temperature to 140°C or at high temperature of 100°C or above by containing CuO as a principal component. <P>SOLUTION: Low loss is ensured up to high frequency near several hundreds kHz by setting the density of sintered body at 4.95 g/cc or above and the crystal grain sizes in the range of 10-15 μm in an oxide magnetic material comprising 52.0-56.0 mol% of iron oxide in terms of Fe<SB>2</SB>O<SB>3</SB>, 8.0-13.0 mol% of zinc oxide in terms of ZnO, 0-5.0 mol% (0 is excluded) of copper oxide in terms CuO, as principal components, and the remainder of manganese oxide (MnO), and 0.005-0.05 wt.% of silicon oxide in terms of SiO<SB>2</SB>, 0.01-0.1 wt.% of calcium oxide in terms of CaO, 0.01-0.5 wt.% of niobium oxide in terms of Nb<SB>2</SB>O<SB>5</SB>, and 0.01-0.5 wt.% of cobalt oxide in terms of CoO, as secondary components. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a magnetic core material used for a power transformer or the like, and relates to an oxide magnetic material.

  In recent years, downsizing of electronic devices such as portable devices has been progressing rapidly. And the power supply used for them has the same tendency, and in particular, the transformer occupies a large volume in the power supply, and also occupies a large proportion in the power loss (hereinafter referred to as core loss). High efficiency is an urgent issue.

  Characteristics required as a magnetic core material for power transformers include low core loss within the drive frequency range, high saturation magnetic flux density, high magnetic permeability, and high Curie temperature. In addition to these, in recent years, power transformer materials for hybrid vehicles and inverter transformer materials for backlights of liquid crystal displays are required to have low loss within a wide temperature range because of large temperature changes in the environment in which they are used.

  In particular, when the core loss is large, not only the efficiency as a power source is bad, but also a danger due to thermal factors due to self-heating occurs. Since the operating environment temperature of the power source is in a temperature range centered on 100 ° C., the core loss of the Mn—Zn-based ferrite used as the power source material is designed to be minimal around 100 ° C. That is, the temperature environment to be used is wide from a low temperature to a high temperature, and under severe conditions, it is necessary for the power transformer material to have low loss over a wide temperature range.

  If the minimum temperature of the core loss is lower than the operating environment temperature, there is a risk that the core loss will increase due to the temperature rise, resulting in a risk due to thermal factors. Conversely, if the minimum temperature of the core loss is too higher than the operating environment temperature, an increase in loss near room temperature becomes a problem due to an increase in hysteresis loss that causes an increase in the magnetocrystalline anisotropy constant.

Examples of Mn—Zn-based ferrite corresponding to the above requirements are disclosed in Patent Documents 1 to 3. All of them contain cobalt oxide as a subcomponent. In Patent Document 1, the main components of iron oxide (Fe ₂ O ₃ ), manganese oxide (MnO), and zinc oxide (ZnO) are used, and cobalt oxide (Co ₃ O ₄ ), silicon dioxide (SiO ₂ ), calcium oxide (CaO), niobium oxide (Nb ₂ O ₅ ), and zirconium oxide (ZrO ₂ ).

In Patent Document 2, in addition to the main components of iron oxide (Fe ₂ O ₃ ), manganese oxide (MnO), and zinc oxide (ZnO), cobalt oxide (CoO), silicon oxide (SiO ₂ ), and calcium oxide are used as subcomponents. (CaO), tantalum oxide (Ta ₂ O ₅ ), and zirconium oxide (ZrO ₂ ) are contained.

In Patent Document 3, in addition to the main components of iron oxide (Fe ₂ O ₃ ), manganese oxide (MnO), and zinc oxide (ZnO), as subcomponents, silicon oxide (SiO ₂ ), calcium carbonate (CaCO ₃ ), oxidation Cobalt (CoO) and titanium oxide (TiO ₂ ) are contained, and sintering conditions are limited.

JP 2002-231520 A Japanese Patent Publication No. 08-001844 JP 2005-119892 A

  However, the conventional techniques containing cobalt oxide as a subcomponent described in Patent Documents 1 to 3 have the following problems. Since cobalt oxide (CoO) has a positive magnetocrystalline anisotropy constant, it has the effect of reducing the core loss by reducing the rate of change of core loss with respect to temperature. However, at the same time, since the minimum temperature of the core loss is shifted to the low temperature side, the gradient with respect to the temperature of the core loss on the high temperature side becomes steep, and the core loss at a temperature of 100 ° C. or more tends to increase and the reduction effect tends to decrease.

In general, it is known that magnetocrystalline anisotropy depends on the amount of Fe ²⁺ in addition to the amount of cobalt oxide (CoO), and the minimum shift of core loss due to cobalt oxide (CoO) content to the low temperature side is minimized. In order to avoid this, it is necessary to adjust the amount of Fe ²⁺ further. As a means for adjusting the amount of Fe ^2+, the ratio of Fe ₂ O ₃ must be reduced in the case of adjustment with the main component composition, and in the case of changing the sintered pattern, it is more in an oxidizing atmosphere. Sintering must be performed. However, there is a limit to these adjustments, and since the minimum temperature of the core loss deviates from the use environment temperature, the effect of reducing the core loss is reduced.

  In Patent Documents 1 to 3, various subcomponents are included to increase the resistance, but the core loss is reduced to about 120 ° C. at the high temperature side, which is higher than that. The core loss reduction at temperature is not enough. Furthermore, under severe operating temperature environments such as automobiles, it is necessary to reduce core loss in a wider temperature range, particularly at high temperatures.

  Accordingly, an object of the present invention is to provide an oxide magnetic material that solves the above problems, reduces core loss in the range of room temperature to 140 ° C., and has a high saturation magnetic flux density and high magnetic permeability.

The present invention is, for solving the above problems, as a main component, 52.0 to 56.0 mol% of iron oxide calculated as Fe ₂ O _3, 8.0 to 13.0 mol% of zinc oxide calculated as ZnO, 0-5.0 mol% of copper oxide in terms of CuO (not including 0), the balance being manganese oxide (MnO), as the minor component, 0.005 to 0.05% silicon oxide in terms of SiO _2, Containing 0.01 to 0.1 wt% of calcium oxide in terms of CaO, niobium oxide in an amount of 0.01 to 0.5 wt% in terms of Nb ₂ O ₅ , and cobalt oxide in an amount of 0.01 to 0.5 wt% in terms of CoO The oxide magnetic material is characterized by the following.

  Further, the oxide magnetic material is characterized in that the density of the sintered body is 4.95 g / cc or more and the crystal grain size of the sintered body is 10 to 15 μm.

Here, CuO has the effect of changing Fe ²⁺ to Fe ³⁺ in order to balance the electric charge by dissolving in the spinel lattice, and without changing the component ratio or sintering pattern of Fe ₂ O ₃ and MnO. The shift of the minimum temperature of the core loss due to the inclusion of CoO to the low temperature side can be suppressed.

  Furthermore, since CuO improves the sinterability, it is possible to obtain a high-density sintered body by sintering at a lower temperature, and to obtain a high density while controlling the crystal grain size within a certain appropriate grain size range. Is possible. Moreover, it is known that hysteresis loss, which is one of the loss components, depends on the crystal grain size and sintered body density in addition to the powder composition, and CuO is an effective component for reducing core loss.

Further, by adding SiO ₂ , CaO, Nb ₂ O ₅ and concentrating it in the grain boundary layer, the specific resistance increases and eddy current loss, which is one of the loss components, can be reduced.

  Therefore, according to the present invention, by containing CuO as a main component, an increase in core loss in the range of room temperature to 140 ° C. or at a temperature of 100 ° C. or higher can be suppressed, and a high saturation magnetic flux density and high An oxide magnetic material having magnetic permeability can be provided.

  Next, embodiments of the oxide magnetic material according to the present invention will be described with specific examples.

In an oxide magnetic material composed of Fe ₂ O ₃ , ZnO, CuO, MnO as main components and SiO ₂ , CaO, Nb ₂ O ₅ , CoO as subcomponents, Fe ₂ O ₃ is added in 52. 0 to 56.0 mol% and ZnO to 9.0 to 13.0 mol%, Fe2O3 is more than 56.0 mol%, ZnO is more than 13.0 mol%, the minimum temperature of core loss is This is because even if shifting to a low temperature side and adding CuO, the minimum temperature cannot be controlled to a high temperature, and the core loss rapidly increases. This is because when Fe ₂ O ₃ is less than 52.0 mol% and ZnO is less than 9.0 mol%, the saturation magnetic flux density is small and the core loss increases rapidly. The reason why CuO is 0 to 5 mol% (not including 0) is that the core loss reduction effect at a temperature of 100 ° C. or higher cannot be obtained unless CuO is contained. This is because the core loss increases rapidly.

The reason why SiO ₂ is 0.005 to 0.05 wt% is that if it is less than 0.005 wt%, sufficient specific resistance cannot be obtained and the core loss increases, and if it exceeds 0.05 wt%, abnormal grains grow. This is because the core loss increases rapidly. The reason why CaO is set to 0.01 to 0.1 wt% is that if the content is less than 0.01 wt%, sufficient specific resistance cannot be obtained and the core loss increases. This is because the core loss rapidly increases and the core loss increases rapidly. The reason why Nb ₂ O _{5 is set} to 0.01 to 0.1 wt% is that if it is less than 0.01 wt%, sufficient specific resistance cannot be obtained and the core loss increases. This is because the core loss increases rapidly. The reason why CoO is set to 0.01 to 0.5 wt% is that if the amount is less than 0.01 wt%, the rate of change of the core loss with respect to the temperature cannot be made sufficiently small. This is because it increases.

  Further, the density of the sintered body is set to 4.95 g / cc or more and the crystal grain size is set to 10 to 15 μm, so that low loss is obtained from a high frequency region around several hundred kHz and room temperature to a high temperature around 140 ° C. An oxide magnetic material having a small change rate of core loss with respect to temperature can be obtained.

  Next, specific examples will be given to describe the oxide magnetic material of the present invention in more detail.

The main components were weighed so that Fe ₂ O ₃ : 51.5 to 57.5 mol%, ZnO: 8.5 to 13.5 mol%, CuO: 0 to 5.5 mol%, and the balance was MnO. Mixing using a ball mill, calcining at 850 ° C. for 2 hours in an air atmosphere, 0.03 wt% of SiO ₂ , 0.05 wt% of CaO, 0.05 wt% of Nb ₂ O ₅ , and 0 of CoO as subcomponents After adding 25 wt%, the mixture was finely pulverized with a ball mill. After fine pulverization, a binder was added and granulated with a spray dryer. Next, it was molded into a toroidal shape of φ30 × φ25 × 5 mm and sintered at 1250 ° C. for 6 hours in a reducing atmosphere in which the oxygen partial pressure was controlled.

Further, by the same method as the conventional material, Fe ₂ O ₃ : 53.0 mol%, MnO: 35.0 mol%, the balance is the main component composition of ZnO, SiO ₂ is 0.03 wt% as a subsidiary component, CaO Of 0.05 wt% and Nb ₂ O ₅ of 0.05 wt% were added, and a sample was manufactured under the same conditions.

  Next, the obtained core was wound, and the core loss was measured from an AC BH tracer from room temperature to 140 ° C. under measurement conditions of a frequency of 100 kHz and a magnetic flux density of 200 mT. The magnetic flux density at 1194 A / m was measured up to 100 ° C. with a direct current BH tracer. Thereafter, the permeability was measured with an impedance analyzer. Table 1 shows the core loss at room temperature and 140 ° C., the minimum temperature of the core loss, the magnetic permeability at 100 kHz at room temperature, and the saturation magnetic flux density at 100 ° C.

  Samples 1 to 3 are examples of the present invention, and samples 4 to 7 are comparative examples in which the main component composition is outside the scope of the claims. Sample 29 is a conventional example.

  FIG. 1 is a diagram showing temperature characteristics of core loss in a temperature range from room temperature to 140 ° C. From Table 1 and FIG. 1, Samples 1 to 3 show high saturation magnetic flux density and magnetic permeability, and it is understood that the core loss (Pcv) is low from room temperature to 140 ° C.

The main components were weighed so that Fe ₂ O ₃ : 54.0 mol%, ZnO: 11.0 mol%, CuO: 2.5 mol%, and the balance was MnO, and mixed using a ball mill. Calcination is performed at 850 ° C. for 2 hours. As auxiliary components, SiO ₂ is 0.001 to 0.06 wt%, CaO is 0.005 to 0.15 wt%, Nb ₂ O ₅ is 0.005 to 0.15 wt%, CoO Was 0.005 to 0.55 wt%, and then pulverized with a ball mill. After finely pulverizing, a binder was added, granulated with a spray dryer, then formed into a toroidal shape of φ30 × φ25 × 5 mm, and sintered at 1250 ° C. for 6 hours in a reducing atmosphere with controlled oxygen partial pressure.

In the same manner as the conventional example, Fe ₂ O ₃ : 53.0 mol%, MnO: 35.0 mol%, the balance is the main component composition of ZnO, SiO ₂ is 0.03 wt% as a subcomponent, CaO. Of 0.05 wt% and Nb ₂ O ₅ of 0.05 wt% were added, and a sample was manufactured under the same conditions.

  Next, the obtained core was wound, and the core loss was measured from an AC BH tracer from room temperature to 140 ° C. under measurement conditions of a frequency of 100 kHz and a magnetic flux density of 200 mT. The magnetic flux density at 1194 A / m was measured up to 100 ° C. with a direct current BH tracer. Thereafter, the permeability was measured with an impedance analyzer. Table 2 shows the core loss at room temperature and 140 ° C., the minimum temperature of the core loss, the magnetic permeability at 100 kHz at room temperature, and the saturation magnetic flux density at 100 ° C.

  Samples 8 to 15 are examples of the present invention, and samples 16 to 23 are comparative examples whose subcomponent compositions are outside the scope of the claims. Sample 29 is a conventional example. Table 2 shows that Samples 8 to 15 have a low loss from room temperature to 140 ° C., a high saturation magnetic flux density, and a high magnetic permeability.

The main components are Fe ₂ O ₃ : 54.0 mol%, ZnO: 11.0 mol%, CuO: 2.5 mol%, the balance is weighed so as to be MnO, and they are mixed using a ball mill. After calcining at 850 ° C. for 2 hours, 0.03 wt% of SiO ₂ , 0.05 wt% of CaO, 0.05 wt% of Nb ₂ O ₅ and 0.25 wt% of CoO as subcomponents are pulverized with a ball mill. Went. After fine pulverization, a binder was added and granulated with a spray dryer. Thereafter, it was formed into a toroidal shape of φ30 × φ25 × 5 mm and sintered at 1180 to 1350 ° C. for 6 hours in a reducing atmosphere in which the oxygen partial pressure was controlled.

Further, as a conventional example, a main component composition of Fe ₂ O ₃ : 53.0 mol%, MnO: 35.0 mol%, balance: ZnO, 0.02 wt% of SiO ₂ as an accessory component, CaO Of 0.05 wt% and Nb ₂ O ₅ of 0.05 wt% were added, and a sample was manufactured under the same conditions.

  Next, the obtained core was wound, and the core loss was measured from an AC BH tracer from room temperature to 140 ° C. under measurement conditions of a frequency of 100 kHz and a magnetic flux density of 200 mT. The magnetic flux density at 1194 A / m was measured up to 100 ° C. with a direct current BH tracer. Thereafter, the permeability was measured with an impedance analyzer. Table 3 shows the core loss at room temperature and 140 ° C., the minimum temperature of the core loss, the magnetic permeability at 100 kHz at room temperature, and the saturation magnetic flux density at 100 ° C.

  Samples 1, 24, and 25 are examples of the present invention, and samples 26 to 28 are comparative examples in which the density of the sintered body or the crystal grain size of the sintered body is outside the scope of the claims. Sample 29 is a conventional example. From Table 3, Samples 1, 24 and 25 having a sintered body density of 4.95 g / cc or more and a crystal grain size of 10 to 15 μm have a low loss from room temperature to 140 ° C. and have a high saturation magnetic flux density. It can be seen that the magnetic permeability is also high.

The figure which shows the temperature characteristic of the core loss in the temperature range from room temperature to 140 degreeC concerning the Example of this invention.

Claims (3)

As the main component, 52.0 to 56.0 mol% of iron oxide calculated as Fe ₂ O _3, zinc oxide from 8.0 to 13.0 mol% in terms of ZnO, the copper oxide in terms of CuO 0-5.0 mol% (not including 0), the balance being manganese oxide (MnO), as the minor component, 0.005 to 0.05% silicon oxide in terms of SiO _2, calcium oxide in terms of CaO from 0.01 to 0 An oxide magnetic material comprising: 1 wt%, niobium oxide in an amount of 0.01 to 0.5 wt% in terms of Nb ₂ O ₅ , and cobalt oxide in an amount of 0.01 to 0.5 wt% in terms of CoO.   The oxide magnetic material according to claim 1, wherein the density of the sintered body is 4.95 g / cc or more.   2. The oxide magnetic material according to claim 1, wherein the sintered body has a crystal grain size of 10 to 15 μm.

Images