JP2008169072A - Mn-Zn FERRITE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Mn-Zn ferrite which is low loss and high saturation flux density in a wide frequency band of 100 kHz to 1 MHz. <P>SOLUTION: The main component composition of the Mn-Zn ferrite contains 53.0-58.0 mol% Fe<SB>2</SB>O<SB>3</SB>, 5.0-9.0 mol% ZnO and the balance MnO. The Mn-Zn ferrite simultaneously contains, as sub-components, 0.002-0.02 wt.% SiO<SB>2</SB>, 0.01-0.2 wt.% CaO, 0.01-0.1 wt.% V<SB>2</SB>O<SB>5</SB>, 0.01-0.1 wt.% Nb<SB>2</SB>O<SB>5</SB>, 0.3-1.5 wt.% MgO, and 0.1-0.5 wt.% CoO. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ferrite material that is used for a magnetic core of a power transformer or the like and has a low loss and a high saturation magnetic flux density in a wide frequency band of 100 kHz to 1 MHz.

  Many conventional Mn—Zn ferrites limit the driving frequency to be used, for example, a material having high permeability and low loss at a frequency of about 100 kHz. In addition, high magnetic flux density is important for transformer miniaturization. In recent years, power transformers have been downsized and driving frequency has been increased, and reduction of loss in a wider frequency band has been demanded for reasons such as loss due to harmonics as well as high saturation magnetic flux density. However, the conventional materials as previously mentioned have the disadvantage that the loss becomes high in the high frequency band, and conversely the saturation magnetic flux density becomes low if the material is low loss in the high frequency band.

As a ferrite material in a high frequency band, for example, Japanese Unexamined Patent Publication No. 6-310320 discloses a material exhibiting low loss by adding various additives to a Mn—Zn ferrite at a frequency of 300 kHz to several MHz. These materials for high-frequency bands are mainly intended for low loss, and similarly, the saturation magnetic flux density related to the miniaturization of the transformer, which is equally important, is not sufficient, and conversely, JP 2003-128458 A The high saturation magnetic flux density material as disclosed in the publication is not sufficient in consideration of the loss in the high frequency band.

JP-A-6-310320 JP 2003-128458 A

It is generally difficult to make a material that achieves both low loss and high saturation magnetic flux density in a wide frequency band of 100 kHz to 1 MHz. To reduce the loss in the high frequency band, there is a method of lowering the firing temperature and suppressing crystal growth, but there is a problem of lowering the saturation magnetic flux density. Further, in order to obtain a sufficient saturation magnetic flux density, it is known to increase the content of Fe ₂ O ₃ which is a basic composition. In this case, the minimum value of power loss (Pcv min) moves to the low temperature side, Loss increased and was not practical.

  The present invention is intended to solve the above problems and to provide a Mn—Zn ferrite having a low loss and a high saturation magnetic flux density in a wide frequency band.

The present invention is mainly composed composition _{53.0~58.0mol% Fe 2 O 3, 5.0~9.0mol} % ZnO, the balance being MnO, _SiO 2 0.002 to 0.02 wt% as an auxiliary component , CaO 0.01 to 0.2 _{wt%, V} 2 O 5 _{0.01~0.1 wt%, Nb} 2 O 5 _0.01~0.1 wt%, MgO 0.3 to 1.5 wt% , CoO 0.1 to 0.5% by weight at the same time, the minimum loss (Pcv min) at 100 kHz-200 mT and 1 MHz-50 mT is 40-100 ° C., and the value is 500 kW / m at 100 kHz-200 mT. ³ or less, 1 MHz-50 mT, 500 kW / m ³ or less, a saturation magnetic flux density of 530 mT or more at 23 ° C., and 430 mT or more at 100 ° C.

  The Mn—Zn ferrite provided by the present invention can provide a Mn—Zn ferrite material having a low loss and a high saturation magnetic flux density in a wide frequency band of 100 kHz to 1 MHz suitable for a magnetic core such as a switching power supply transformer.

Example 1 High-purity iron oxide, manganese oxide, and zinc oxide were weighed and mixed so as to have the composition shown in Table 1, and calcined at 950 ° C. for 2 hours in the atmosphere. Within the scope of the present invention, this calcined raw material is within a range of 0.002 wt% SiO ₂ , 0.06 wt% CaO, 0.04 wt% V ₂ O _5, 0.04 wt% Nb ₂ O ₅ , MgO 0. The mixture was added to 7 wt% and CoO 0.3 wt%, and pulverized with an attritor until the pulverized particle size became 1.7 μm. Polyvinyl alcohol was added to the pulverized powder and granulated, and the resulting granulated granules were formed into a toroidal shape having an outer diameter of 24 mm, an inner diameter of 19 mm, and a height of 10 mm. Thereafter, while maintaining the oxygen partial pressure at the peak temperature in the main firing, the temperature was maintained at 1350 ° C. for 4 hours, and then the temperature was lowered to obtain a sintered sample. Thus, the loss (100kHz-200mT, 1MHz-50mT, measurement temperature 23-120 degreeC) was measured for the obtained sample with the BH / Z analyzer (E5060A by HP company). Further, the saturation magnetic flux density at the maximum magnetic field of 1194 A / m was measured. Table 1 shows the Pcv min value of each composition and its temperature, and the saturation magnetic flux density at 23 ° C. and 100 ° C. Moreover, the temperature characteristic of the loss of 1 MHz-50mT is shown in FIG. As is apparent from the results shown in this table and figure, within the main component composition range of the present invention, Pcv min is in the range of 40 to 100 ° C., and at 100 kHz-200 mT and 1 MHz-50 mT, respectively, at 500 kW / m ³ or less. is there. Further, a saturation magnetic flux density of 530 mT or more at 23 ° C. and 430 mT or more at 100 ° C. is obtained.

(Example _{2) Fe 2 O 3: 55.5mol} %, ZnO: 7.0mol% pure iron oxide as the balance becomes MnO, zinc oxide, manganese oxide were weighed and mixed, atmospheric 950 ° C. × 2 Temporary calcining was performed. Within the scope of the present invention, the calcined raw material is 0.007 wt% SiO ₂ , 0.06 wt% CaO, 0.04 wt% V ₂ O _5, 0.04 wt% Nb ₂ O _5. MgO and CoO were added so as to contain the amounts shown in Table 2. Thereafter, samples were prepared and evaluated in the same manner as in Example 1. Table 2 shows these Pcv min temperatures and their values, and saturation magnetic flux densities at 23 ° C. and 100 ° C. Moreover, the temperature characteristic of the loss of 1 MHz-50mT is shown in FIG. As is apparent from the results shown in this table and figure, in the MgO and CoO addition ranges of the present invention, Pcv min is in the range of 40 ° C. to 100 ° C., and 500 kW at 100 kHz-200 mT and 1 MHz-50 mT, respectively. / M ³ or less.

The main component composition is Mn—Zn ferrite composed of Fe ₂ O ₃ , MnO and ZnO, and is limited to the range of 53.0 to 58.0 mol% Fe ₂ O ₃ , 5.0 to 9.0 mol% ZnO and the balance MnO. did. The reason is that when Fe ₂ O ₃ is 53.0 mol% or less, the saturation magnetic flux density is lowered, and when it is 58.0 mol% or more, the loss in the high frequency band is increased. Similarly, when the ZnO content is 5.0 mol% or less, the saturation magnetic flux density is lowered. When the ZnO content is 9.0 mol% or more, the loss in the high frequency band increases.

In addition to the main component composition, SiO ₂ , CaO, V ₂ O ₅ , Nb ₂ O ₅ , MgO, and CoO are added simultaneously as subcomponents. SiO ₂ and CaO coexist with each other to increase the specific resistance of the grain boundary and contribute to the reduction of eddy current loss. Nb ₂ O ₅ precipitates at the grain boundary together with SiO ₂ and CaO to form a high resistance phase. To reduce loss. When Nb ₂ O ₅ coexists, V ₂ O ₅ suppresses the occurrence of intragranular pores and abnormal grain growth induced by Nb ₂ O ₅ , so that the crystal composition has a fine and uniform grain size. It has the effect of stabilizing and suppressing the deterioration of loss. When the main composition of Fe ₂ O ₃ , MnO, and ZnO that maintains the target saturation magnetic flux density is used, Pcv min is 40 ° C. or lower. Therefore, by adding MgO, Pcv min is practically effective from 40 to 100 ° C. Within the range of MgO has the effect of moving Pcv min to a high temperature and at the same time reduces the loss in the high frequency band. When CoO is dissolved in Mn—Zn ferrite as Co ²⁺ , the positive magnetic anisotropy due to Co ²⁺ and the negative magnetic anisotropy due to Fe ²⁺ cancel each other, and as a result, the magnetism has a small absolute value and temperature change. Anisotropy occurs, and has the effect of reducing fluctuations in temperature characteristics over a wide temperature range from low temperature to high temperature, and has the function of improving the saturation magnetic flux density at room temperature. As long as these subcomponents can become oxides after firing, the structure at the time of addition is not limited. Moreover, the addition may be performed in any process as long as it is contained before the main firing.

It is a figure which shows the Pcv temperature characteristic (1MHz-50mT) by the difference in a main component composition in Example 1. FIG. It is a figure which shows the Pcv temperature characteristic (1MHz-50mT) by the difference in MgO in Example 2, and CoO content.

Claims (2)

The main component composition is 53.0 to 58.0 mol% Fe ₂ O ₃ , 5.0 to 9.0 mol% ZnO, and the balance MnO, with SiO ₂ 0.002 to 0.02 wt% and CaO 0. 01 to 0.2 _{wt%, V} 2 O 5 _{0.01~0.1 wt%, Nb} 2 O 5 _0.01~0.1 wt%, MgO 0.3 to 1.5 wt%, CoO 0. An Mn-Zn ferrite containing 1 to 0.5% by weight at the same time.
The minimum value of the loss in the 100kHz-200 mT and 1MHz-50mT (Pcv min) is in the 40 to 100 ° C., its value is in the 100kHz-200mT 500kW / ^{m 3} or less, at 1MHz-50mT 500kW / ^{m 3} or less, and saturation 2. The Mn—Zn ferrite according to claim 1, wherein the magnetic flux density is 530 mT or more at 23 ° C. and 430 mT or more at 100 ° C. 3.

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