JP2000277318A - Mn/Zn-BASED FERRITE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Mn/Zn-based ferrite having a high initial permeability over a wide range of temperatures. SOLUTION: This Mn/Zn-based ferrite contains 52.60-53.00 mol% of Fe2O3, ZnO mol% satisfying the conditions of the following relation and MnO as a balance, 5 ppm or less of boron and 15 ppm or less of phosphorus with respect to 100 mol% of MnO balance, with the relation; 1.25×F2 O3-42.00<=ZnO<=1.25×F2O3-40.25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MnZn ferrite, and more particularly to a MnZn ferrite having a high initial magnetic permeability over a wide temperature range.

[0002]

2. Description of the Related Art MnZn-based ferrites include Fe ₂ O ₃ ,
It is composed mainly of ZnO and MnO, and exhibits high magnetic permeability in a main component having a magnetic anisotropy constant and a magnetostriction constant of zero. For this reason, MnZn-based ferrites are used as small or thin magnetic cores such as transformers and noise filters. Among them, particularly high pulse permeability is required for a pulse transformer used for an interface section of a recent digital communication device, and the initial permeability at room temperature is 10%.
Those with about 000 or more are often used. However, when such a pulse transformer is used for a public telephone or a line termination device, it may be installed outdoors. Therefore, the MnZn-based ferrite used for the pulse transformer needs to have a high initial permeability in a wide temperature range from a low temperature to a high temperature. However, in conventional MnZn-based ferrites, a composition is selected so that magnetic anisotropy and magnetostriction become zero at room temperature and high initial magnetic permeability is exhibited on the assumption that the ferrite is used at around room temperature or higher. For this reason, the temperature characteristics of the initial permeability of the conventional material are that the magnetic anisotropy constant sharply decreases just above the Curie temperature, and the magnetic permeability anisotropy and magnetostriction are small near the room temperature (primary peak) and room temperature. Has two peaks (secondary peaks). Various compositions and manufacturing methods have been devised so as to increase the secondary peak.

[0003]

However, if the initial magnetic permeability at room temperature is increased, on the other hand, a low temperature range (about -30 to 0 ° C.)
, The initial permeability is significantly reduced. For this reason, it is necessary to increase the number of windings in order to secure the inductance in the low temperature range, and to use a material whose initial permeability at room temperature is higher than necessary to increase the initial permeability in the low temperature range. It was inefficient. For example, in the case of a conventional MnZn-based ferrite having an initial magnetic permeability of about 10,000 at room temperature, the initial magnetic permeability at −20 ° C. is halved to about 5000. On the other hand, -30 to-
In order to obtain a high initial magnetic permeability of about 7,000 or more at 20 ° C., it is necessary to extremely increase the initial magnetic permeability at room temperature to 15,000 or more in consideration of the above deterioration. In order to obtain a MnZn-based ferrite having an initial magnetic permeability at room temperature of 15,000 or more, high-quality raw materials and a firing method,
Strict control of the sintering conditions is required, and there is a problem that costs and man-hours increase.

[0004] Japanese Patent Application Laid-Open No. Hei 6-263647 describes a MnZn-based ferrite having an initial magnetic permeability of 8000 or more in a range of -20 to 100 ° C and a change rate of 70% or less. However, the initial permeability at 10 kHz is from -30 ° C to 8000 or more and from -20 ° C to 10,000.
The above is not described. In addition, Japanese Patent Application Laid-Open
No. 25606025 discloses that MnZn-based ferrite contains bismuth oxide and molybdenum oxide,
Initial magnetic permeability of 8500 or more in the range of −20 to 20 ° C., and
An MnZn-based ferrite having an initial magnetic permeability of 10,000 or more in a temperature range of 20 to 100 ° C. is described. However, there is no description of improvement for a lower temperature range of −30 to −20 ° C., and the initial permeability is 1 at a lower temperature of −20 ° C.
Those having a performance of 0000 or more are not described.

As described above, in the case of the conventional MnZn-based ferrite, in order to obtain a high initial magnetic permeability over a wide temperature range,
There is a problem that the initial permeability at room temperature must be increased more than necessary, which is very inefficient and raises the cost. In view of the above, an object of the present invention is to obtain a MnZn-based ferrite having a high initial magnetic permeability over a wide temperature range.

[0006]

SUMMARY OF THE INVENTION The present invention is a MnZn ferrite, a Fe ₂ O ₃ 52.60~53.0
A MnZn-based ferrite comprising 0 mol%, ZnO mol% under the condition of the following formula (1), and a total of 100 mol% of the remaining MnO, containing 5 ppm or less by weight of boron and 15 ppm or less by weight of phosphorus. Things. 1.25 × Fe ₂ O ₃ −42.00 ≦ ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Formula (1) This MnZn-based ferrite should have an initial permeability at 10 kHz of 8000 or more in a temperature range of −30 to 90 ° C. it can.

[0007] More preferably, it is a MnZn-based ferrite, which contains 52.60 to 53.00 mol of Fe ₂ O ₃ .
% ZnO mol% under the condition of the following formula (2) and the balance Mn
5 ppm by weight of boron in a total of 100 mol% of O
Hereinafter, there is provided an MnZn-based ferrite containing 15 ppm or less by weight of phosphorus. 25.00 <ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Formula (2) This MnZn-based ferrite has an initial magnetic permeability at 10 kHz of 10,000 or more in a temperature range of −20 to 90 ° C. and 11,000 or more at 23 ° C. High permeability MnZn
It is a system ferrite.

Further, calcium oxide, silicon dioxide, bismuth oxide,
It is preferable to contain at least one of indium oxide, tantalum oxide, niobium oxide, titanium oxide, tin oxide, and molybdenum oxide.

[0009]

DETAILED DESCRIPTION OF THE INVENTION MnZn ferrite of the present invention is 52.60～53.00Mol% of Fe ₂ O _3, and the Fe ₂ O ₃ and ZnO have to satisfy the conditions of the following formula (1) Must. 1.25 × Fe ₂ O ₃ −42.00 ≦ ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Formula (1) The present inventor disclosed in Japanese Patent Application Laid-Open Nos. 6-263447 and 10-256025.
In the composition range of the MnZn-based ferrite disclosed in Japanese Patent Application Laid-open No.
The phenomenon in which the initial magnetic permeability was low at a low temperature of 0 ° C. was examined. As a result, in the MnZn-based ferrite, the secondary peak temperature and the Curie temperature of the initial permeability change depending on the mutual amount of Fe ₂ O ₃ and ZnO instead of simply defining the composition range of each component independently. -30 unless this relationship satisfies the relationship of equation (1).
It has been found that it is not possible to obtain a composition range having a high initial permeability at low temperatures such as 0 ° C. The Curie temperature was set to 100 ° C. or higher in consideration of the operating range of the transformer.

In the present invention, the main components Fe ₂ O ₃ and Z
When the range of combination of nO is limited to the range of the formula (1),
It is unknown why the initial permeability can be increased to 10,000 or more even at around room temperature while maintaining the initial permeability of 8000 or more at a low temperature of -30 to 0 ° C. Generally, MnZn
In the system ferrite, as the amount of Fe ₂ O ₃ increases, the Curie temperature increases, and the secondary peak temperature decreases. When the amount of ZnO increases, the Curie temperature decreases, and the secondary peak temperature decreases. The present inventors have secondary peak temperature and the Curie temperature of the initial permeability in combination with Fe ₂ O ₃ and ZnO is changed, Fe ₂
If the combination of O ₃ and ZnO is out of a certain range, the secondary peak temperature is too low or too high and −30.
It was noted that the initial magnetic permeability could not be increased to 10,000 or more even at around room temperature while securing the initial magnetic permeability of 8000 or more in a temperature range of not less than ° C. The present inventor, by examining the relationship between the mutual amounts of Fe ₂ O ₃ and ZnO, lowers the secondary peak temperature below room temperature while securing the necessary Curie temperature, thereby reducing the initial magnetic permeability in the low temperature region. I hypothesized that it could be higher. From this idea, various experiments were conducted. As shown in FIG. 2, the initial permeability at 10 kHz was 8000 or more in the temperature range of -30 to 90 ° C.
The composition range of 10000 or more in the range of 20 to 90 ° C. is (Fe ₂ O ₃ (mol%), ZnO (mol%))
(52.60, 23.75), (52.6
0, 25.50), (53.00, 26.00), (5
3.00, 24.25). Further, it has been newly found that the initial magnetic permeability at 10 kHz at 23 ° C. can be 11000 or more in a range where the ZnO content exceeds 25.00 mol% in a range surrounded by these four points. This is represented by the following equation (2). 25.00 <ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Equation (2)

Now, as described above, Fe ₂ O ₃ , ZnO,
It is of course the most important to determine the basic composition of MnO, but it is very difficult to obtain a high initial permeability over the entire desired temperature range alone. It has been newly found that the above problem can be solved by limiting the amount of impurities, particularly boron and phosphorus. As an effect of boron on the initial magnetic permeability of the MnZn-based ferrite, for example, on page 92 of the document “Ferrite” (Hiraga et al., Maruzen, 1986), the crystal structure is made nonuniform and the development of high initial magnetic permeability is inhibited. Must be kept below 50 ppm,
It is described. However, as described above, the initial permeability is a description of the initial permeability only at room temperature when the secondary peak is set at room temperature, and is as wide as −30 to 90 ° C. as in the present invention. No mention is made of the effect of boron when achieving high initial permeability in the region over the temperature range. There is no description of phosphorus in the above literature. Also, `` J.
Phys. IV, France, (1997) Colloque C1-128 (ICF-7 Bordeau
x, September (1996))) shows the relationship between iron loss and phosphorus content in low-loss MnZn ferrites for power supplies. Not at all mentioned.

In this regard, the present inventor has determined that -30 to 90 ° C.
In order to suppress non-uniform structure such as abnormal grains and to realize a high initial permeability stably in a region over a wide temperature range, Fe ₂ O
The relationship between the mutual amounts of ₃ and ZnO satisfies the relationship of the formula (1) or the formula (2), and the boron in the MnZn-based ferrite is 5 ppm by weight in 100 mol% of Fe ₂ O ₃ , ZnO, MnO, preferably 4ppm or less, phosphorus amount 15p
pm, preferably 11.2 ppm or less. Boron and phosphorus are very difficult to remove in the middle of a process such as a baking process once they are mixed in the manufacturing process of MnZn-based ferrite. Is preferred.

The MnZn-based ferrite of the present invention has the above-mentioned composition as an essential component, and is composed of calcium oxide, silicon dioxide, bismuth oxide, indium oxide, tantalum oxide, niobium oxide, titanium oxide, tin oxide, and molybdenum oxide. At least one of them may be contained in addition to the essential composition. Such MnZn _{ferrite, Fe 2 O 3 -ZnO- MnO- CaO-} SiO 2 Fe 2 O 3 -ZnO- MnO- CaO- Bi 2 O 3 Fe 2 O 3 -ZnO- MnO- CaO- In 2 _{O 3 Fe 2 O 3 -ZnO- MnO-} CaO- TiO 2 Fe 2 O 3 -ZnO- MnO- CaO- SiO 2 - Ta 2
_{O 5 Fe 2 O 3 -ZnO- MnO-} CaO- SiO 2 - Nb 2
O ₅ -Bi ₂ O _{3 and the} like are exemplified, but are not limited to these examples.

CaO and SiO ₂ segregate at the grain boundaries, thereby contributing to lower loss of MnZn-based ferrite.
₂ O ₃ , In ₂ O ₃ and V ₂ O ₅ promote crystal growth as low melting point compounds and contribute to high magnetic permeability. TiO ₂ , SnO
₂ contributes to lowering the loss by increasing the resistance inside the crystal. From the above viewpoints, the content of calcium oxide is 50 to 1000 ppm by weight as CaO, and the content of silicon dioxide is 50 to 200 ppm by weight as SiO ₂ . Bismuth oxide, indium oxide, vanadium oxide,
The contents of tantalum oxide, niobium oxide, titanium oxide, tin oxide, molybdenum oxide, and the like are expressed by weight of Bi ₂ O, respectively.
₃ , In ₂ O ₃ , V ₂ O ₅ , Ta ₂ O ₅ , Nb ₂ O ₅ ,
Converted to TiO ₂ , SnO ₂ , MoO, etc. for a total of 3000
It is preferably at most about ppm.

[0015]

Next, the present invention will be described based on embodiments.

Using iron oxides having various boron and phosphorus contents, various Fe ₂ O ₃ and ZnO as shown in Table 1 were used.
After mixing the raw materials so that the balance becomes MnO with the composition of
Calcination was performed at 0 ° C. for 3 hours. Calcium oxide is added to CaO
Bismuth oxide in 0.011 to 0.028 wt%
Is added in a range of 0.015～0.035Wt% at ₂ O _3, 8 hr in a ball mill, after molding into a ring-shaped core, the temperature was raised at a heating rate 250 ° C. / h in the air, 1100
The temperature was raised from 500 ° C. to a nitrogen atmosphere, the temperature was raised to 500 ° C./h, and after the holding temperature reached 1370 ° C., the oxygen concentration was controlled to 10% by volume or less for 5 hours. The temperature change of the initial magnetic permeability at 10 kHz of the obtained sintered body was measured from -30 ° C to 120 ° C. The present invention is described in Example Nos. Nos. 1 to 14 are shown in Comparative Example Nos. 1 to 1
4 was shown. Also, in Example No. 6, No. 10 and Comparative Example No. 8, No. Figure 13 shows the temperature dependence of the initial permeability of Fig. 13.
It was shown to. Table 1 shows the amounts of boron and phosphorus and the amounts of added calcium oxide and bismuth oxide contained in each sintered body.

As can be seen from Table 1 and FIG. 1, the embodiment of the present invention has a temperature of -30.degree. C., -20.degree. C., -10.degree. C., -23.degree.
The initial permeability at 10 kHz is 800 at each temperature of 90 ° C.
0 or more, and at -20 ° C or more, the initial permeability is 1
0000 or more. Further, more preferably, at 23 ° C,
It is shown that the initial permeability at 10 kHz is 11,000 or more.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

The MnZn ferrite of the present invention has
High initial permeability in a wide temperature range of 0 to 90 ° C (initial permeability in a temperature range of -30 ° C to 90 ° C is 8000 or more, -2
(Initial permeability in a temperature range of 0 ° C. to 90 ° C. is 10,000 or more), so that a material extremely useful for applications such as a pulse transformer operating in a wide temperature range can be obtained.

[Brief description of the drawings]

FIG. 6, 10 and Comparative Example Nos. 8,1
3 is a diagram showing temperature characteristics of initial magnetic permeability of No. 3; FIG.

FIG. Nos. 1 to 14 and Comparative Example Nos. 1-9
₃ is a diagram in which the amount of Fe ₂ O _{3 and the} amount of ZnO are plotted.

Claims (2)

[Claims] 1. An MnZn-based ferrite comprising: 52.60 to 53.00 mol% of Fe ₂ O ₃ ; ZnO mol% under the condition of the following formula (1);
A MnZn-based ferrite, characterized by containing 5 ppm or less by weight of boron and 15 ppm or less by weight of phosphorus in a total of 100 mol% of O. 1.25 × Fe ₂ O ₃ −42.00 ≦ ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Equation (1) 2. The method according to claim 1, wherein the MnZn-based ferrite further contains at least one of calcium oxide, silicon dioxide, bismuth oxide, indium oxide, tantalum oxide, niobium oxide, titanium oxide, tin oxide and molybdenum oxide. The MnZn-based ferrite according to claim 1, wherein: