JP2005236069A - Mn-Zn FERRITE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide Mn-Zn ferrite where the initial permeability at 23°C is 3000 or more, the rate of change of the initial permeability is small in the wide temperature span (-20°C to 150°C) and the saturation magnetic flux density is 540mT or more at 23°C. <P>SOLUTION: The Mn-Zn ferrite is provided with main ingredients consisting of Fe<SB>2</SB>O<SB>3</SB>, ZnO and MnO, and accessary ingredients comprising SiO<SB>2</SB>(0.005-0.01% by weight), CaO (0.03-0.06% by weight) and Nb<SB>2</SB>O<SB>5</SB>(0.01-0.03% by weight). The main ingredients consist of 53.7-54.4mol% Fe<SB>2</SB>O<SB>3</SB>, 8.0-10.0mol% ZnO, and remainder MnO; and the accessory ingredients comprise simultaneously V<SB>2</SB>O<SB>5</SB>0.01-0.06% by weight and CoO 0.05-0.60% by weight, other than the above-mentioned. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention has a small rate of change in initial permeability (hereinafter referred to as μi) over a wide temperature range and a ferrite sintered body having a high saturation magnetic flux density, Mn-Zn suitable for a transformer for communication equipment and an output filter for a digital amplifier. It relates to ferrite.

  The Mn—Zn ferrite used in communication equipment transformers and digital amplifier output filters is required to have magnetic properties such as high initial permeability, high saturation magnetic flux density, and low loss. Recently, in order to obtain stable magnetic characteristics against changes in temperature around the circuit due to heat generation due to downsizing and high integration of electronic components and changes in environmental temperature, compared to general high permeability materials with large temperature characteristics change It is important to be a high magnetic permeability material with a small change in magnetic properties over a wide temperature range. In particular, when used in an output filter for a digital amplifier, there is a problem in that the frequency characteristics of the filter change due to changes in magnetic characteristics due to temperature changes, which adversely affects sound quality.

Moreover, since it is necessary to determine the size of the core to be used in a range where the magnetic flux density is not saturated for miniaturization, a material having a higher saturation magnetic flux density is desired.

JP 58-114401 A

  For the reasons described above, Mn—Zn ferrite used in a transformer for communication equipment and an output filter for digital amplifier is desired to have stable magnetic characteristics against temperature changes. Conventionally, a method of adding cobalt oxide has been attempted to obtain a material having a stable μi against temperature change. However, there are many cases where μi is 1000 or less, and even high ones are about 2000. Further, if μi is low, it is necessary to increase the number of windings in order to obtain a required inductance, and there is a problem that copper loss increases.

In order to obtain a high saturation magnetic flux density, it is known to increase the content of Fe ₂ O ₃ which is a basic composition or to increase the density of ferrite. However, these methods are not practical because there are problems that the temperature at which the power loss becomes a minimum value moves to the low temperature side and the saturation magnetic flux density at a high temperature of about 100 ° C. decreases.

The present invention is intended to solve the above problems and to provide a Mn—Zn ferrite having a small change rate of μi in a wide temperature range and a high saturation magnetic flux density.

In the present invention, the main component composition is composed of Fe ₂ O ₃ , ZnO, and MnO, and as subcomponents, SiO ₂ (0.005 to 0.01 wt%), CaO (0.03 to 0.06 wt%), Nb _In ferrite containing ₂ O ₅ (0.01 to 0.03% by weight), the main component composition consists of 53.7 to 54.4 mol% Fe ₂ O ₃ , 8.0 to 10.0 mol% ZnO, and the balance MnO. In addition to the above, V ₂ O ₅ 0.01 to 0.06 wt% and CoO 0.05 to 0.60 wt% are simultaneously contained as subcomponents, and the initial permeability at 23 ° C. is 3000 or more. Mn—Zn ferrite characterized in that the maximum rate of change of initial permeability at −20 ° C. to 150 ° C. is 15% or less and the saturation magnetic flux density at 23 ° C. is 540 mT or more, based on the initial permeability at 0 ° C. I will provide a.

  The Mn—Zn ferrite provided by the present invention has an initial permeability of 3000 or more at 23 ° C., and a maximum change rate of initial permeability at −20 ° C. to 150 ° C. based on the initial permeability at 23 ° C. is 15%. The following is a transformer for communication equipment and a digital amplifier that can have a high saturation magnetic flux density of 540 mT or higher at a saturation magnetic flux density of 23 ° C. and can exhibit stable performance against temperature changes around the circuit and environmental temperatures. It became possible to supply the output filter.

Fe ₂ O ₃ : 54.1 mol%, ZnO: 8.8 mol% High-purity iron oxide, zinc oxide, and manganese oxide are weighed and mixed so that the balance is MnO, and calcined in the atmosphere at 950 ° C for 2 hours. It was. _SiO 2 0.005 wt% in the claims scope of the present invention in the calcined material, CaO 0.04 _{wt%, Nb} 2 O 5 0.02 _{wt%, V} 2 O 5 0.05% by weight so as CoO was added so as to contain the amount shown in Table 1, and pulverized with an attritor until the pulverized particle size became 1.5 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 1300 ° C. for 5 hours, and then the temperature was lowered to obtain a sintered sample. The rate of change in μi of the thus obtained sample was measured with an LCR meter (HP 4284A). Moreover, the saturation magnetic flux density in the maximum magnetic field 800A / m was measured for the sample with the BH / Z analyzer (E5060A by HP company). Table 1 shows the maximum change rate of μi at −20 ° C. to 150 ° C. and the saturation magnetic flux density at 23 ° C. based on μi at 23 ° C., μi at 23 ° C. Also, the temperature characteristics of μi are shown in FIG.

  From Table 1 and FIG. 1, in the addition range containing CoO of the conformity examples 1 to 3, the μi at 23 ° C. is 3000 or more, the μi change rate at −20 ° C. to 150 ° C. is 15% or less, and at 23 ° C. A saturation magnetic flux density of 540 mT or more is obtained. Among them, the case of the adaptation example 2 is the best mode.

  In the comparative example outside the scope of the claims, it can be seen that if the CoO is deviated to a smaller extent, the effect of CoO is poor, the rate of change of μi increases, and μi at 23 ° C. also decreases. It can also be seen that when CoO deviates from the range of claims, μi at 23 ° C. is greatly reduced and the rate of change in the range of −20 ° C. to 150 ° C. is increased.

High purity iron oxide, manganese oxide, and zinc oxide were weighed and mixed so as to have the composition shown in Table 2, and calcined at 950 ° C. for 2 hours in the atmosphere. _SiO 2 0.005 wt% in the present invention according to claim scope to the calcined material, CaO 0.04 _{wt%, Nb} 2 O 5 0.02 _{wt%, V} 2 O 5 0.05% by weight, CoO 0. It added so that it might become 30 weight%. Thereafter, samples were prepared and evaluated in the same manner as in the best mode for carrying out the invention. Table 2 shows the secondary peak temperature (hereinafter referred to as Ts) of the μi temperature characteristics of each composition, μi at 23 ° C., the maximum change rate of μi at −20 to 150 ° C. based on μi at 23 ° C., and at 23 ° C. The saturation magnetic flux density is shown. Further, the temperature characteristics of μi are shown in FIG.

  From Table 2 and FIG. 2, in the compositions of the conforming examples 4 to 7, Ts is in the range of 10 ° C. to 50 ° C., μi at 23 ° C. is 3000 or more, and μi change rate at −20 ° C. to 150 ° C. is 15% or less. A saturation magnetic flux density at 23 ° C. of 540 mT or more is obtained.

  In the comparative example of the composition outside the scope of the claims, it can be seen that the decrease in μi at 23 ° C. and the rate of change in μi increase.

The main component _{composition, 53.7~54.4mol% Fe 2 O 3,} 8.0~10.0mol% ZnO, is limited to a range of balance MnO. The reason is that Ts is set to 10 ° C. to 50 ° C. and μi of 23 ° C. is obtained 3000 or more, and the saturation magnetic flux density at 23 ° C. is 540 mT. The above-mentioned main component composition was determined by sufficiently examining what can be obtained.

In the present invention, the reason why the Ts of the μi temperature characteristic is set to 10 to 50 ° C. is that if the Ts is out of the above range, the μi temperature characteristic curve will swell, the μi will decrease at 23 ° C., and the wide temperature range. This is because the rate of change of μi at a large value is undesirable.

In addition to the basic composition, SiO ₂ , CaO, V ₂ O ₅ , Nb ₂ O ₅ , and CoO are added simultaneously as subcomponents. By coexisting with each other, SiO ₂ and CaO increase the specific resistance of the grain boundary, contribute to the reduction of eddy current loss, and are effective in improving the impedance characteristics. Nb ₂ O ₅ precipitates at the grain boundaries together with SiO ₂ and CaO, forms a high resistance phase and reduces power loss, and also contributes to a reduction in residual magnetic flux density. 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 stabilizes and suppresses the deterioration of power loss, and is effective in improving the saturation magnetic flux density and reducing the residual magnetic flux density. CoO introduces Co ²⁺ into Mn—Zn ferrite, so that the positive magnetic anisotropy due to Co ²⁺ and the negative magnetic anisotropy due to Fe ²⁺ cancel each other, and as a result, a magnetic difference with a small absolute value and temperature change is obtained. Anisotropy occurs, and has the effect of reducing fluctuations in temperature characteristics over a wide temperature range from low to high. 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 temperature characteristic of (mu) i of the adaptation example by the difference in CoO content concerning this invention, and a comparative example.

It is a figure which shows the temperature characteristic of (mu) i of the adaptation example by the difference in the main component composition concerning this invention, and a comparative example.

Claims (1)

The main component composition is composed of Fe ₂ O ₃ , ZnO, and MnO, and SiO ₂ (0.005 to 0.01 wt%), CaO (0.03 to 0.06 wt%), Nb ₂ O ₅ ( 0.01 to 0.03% by weight), the main component composition is composed of 53.7 to 54.4 mol% Fe ₂ O ₃ , 8.0 to 10.0 mol% ZnO, and the balance MnO. In addition to the above, V ₂ O ₅ 0.01 to 0.06 wt% and CoO 0.05 to 0.60 wt% are simultaneously contained, the initial permeability at 23 ° C. is 3000 or more, and the initial permeability at 23 ° C. A Mn—Zn ferrite characterized in that the maximum change rate of initial permeability at −20 ° C. to 150 ° C. based on magnetic permeability is 15% or less and the saturation magnetic flux density at 23 ° C. is 540 mT or more.

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