JP3481493B2 - MnZn ferrite - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art MnZn-based ferrites are Fe ₂ O ₃ ,
It is composed mainly of ZnO and MnO, and exhibits high magnetic permeability in a main component whose magnetic anisotropy constant and magnetostriction constant are zero. Therefore, MnZn-based ferrite is used as a small or thin magnetic core for transformers, noise filters, and the like. Among them, the pulse transformer used in the interface section of the recent digital communication equipment is required to have a particularly high magnetic permeability, and the initial magnetic permeability at room temperature is 10%.
The ones of about 000 or more are often used. However, such a pulse transformer may be installed outdoors when used in a public telephone or a line termination device. Therefore, the MnZn-based ferrite used for the pulse transformer is required to have a high initial magnetic permeability in a wide temperature range from low temperature to high temperature. However, in the conventional MnZn-based ferrite, a composition is selected such that the magnetic anisotropy and the magnetostriction become zero at room temperature and a high initial magnetic permeability is exhibited, assuming that the MnZn-based ferrite is used at around room temperature or higher. Therefore, the temperature characteristics of the initial magnetic permeability of conventional materials are that the magnetic permeability anisotropy and magnetostriction are small near the peak of the magnetic permeability (primary peak) due to the magnetic anisotropy constant rapidly decreasing just above the Curie temperature. It has two peaks (secondary peak). Then, various improvements have been made to the composition and the manufacturing method so as to increase the secondary peak.

[0003]

However, if the initial magnetic permeability at room temperature is increased, on the contrary, in the low temperature region (about -30 to 0 ° C)
The initial permeability is markedly reduced. For this reason, it is necessary to increase the number of windings to secure the inductance in the low temperature range, and to use a coil with a higher initial magnetic permeability at room temperature than necessary in order to increase the initial magnetic 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 is reduced to about 5,000 at -20 ° C. 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 increase the initial magnetic permeability at room temperature of 15,000 or more in consideration of the above deterioration. In order to obtain an MnZn-based ferrite having an initial permeability of 15,000 or more at room temperature, high quality raw materials and firing methods,
There is a problem that strict control of firing conditions is required, resulting in an increase in cost and man-hours.

Japanese Unexamined Patent Publication (Kokai) No. 6-263447 describes a MnZn-based ferrite having an initial magnetic permeability of 8000 or more in the range of -20 to 100 ° C. and a change rate of 70% or less. However, the initial permeability at 10 kHz is -30 ° C to 8000 or more and -20 ° C to 10,000.
The above is not described. In addition, JP-A-10-
Japanese Patent No. 256025 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
It describes MnZn-based ferrite having an initial magnetic permeability of 10,000 or more in the temperature range of 20 to 100 ° C. However, there is no description of improvement regarding the temperature range of −30 to −20 ° C., which is still lower, and the initial magnetic permeability is 1 from a low temperature of −20 ° C.
There is no description having a performance of 0000 or more.

As described above, in the conventional MnZn-based ferrite, if an attempt is made to obtain a high initial permeability in a wide temperature range,
There was a problem that the initial magnetic permeability at room temperature had to be increased more than necessary, which was extremely inefficient and increased costs. In view of the above, it is an object of the present invention to obtain a MnZn-based ferrite having a high initial magnetic permeability in a wide temperature range.

[0006]

The present invention is a MnZn type ferrite containing Fe ₂ O ₃ of 52.60 to 53.0.
Provided is an MnZn-based ferrite characterized by containing 5 ppm or less by weight of boron and 15 ppm or less by weight of phosphorus in 0 mol%, ZnO mol% under the condition of the following formula (1), and 100 mol% in total of the balance MnO. It is a thing. 1.25 × Fe ₂ O ₃ −42.00 ≦ ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Formula (1) This MnZn-based ferrite has an initial magnetic permeability at 10 kHz of 8,000 or more in the temperature range of −30 to 90 ° C. it can.

More preferably, it is a MnZn type ferrite containing 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 100 mol% of total O
The present invention provides a MnZn-based ferrite containing phosphorus by 15 ppm or less by weight. 25.00 <ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Formula (2) This MnZn-based ferrite is characterized in that the initial permeability at 10 kHz is 10,000 or more in the temperature range of −20 to 90 ° C. and 11,000 or more at 23 ° C. And high magnetic permeability MnZn
It is a system ferrite.

Further, in the MnZn-based ferrite, 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]

BEST MODE FOR CARRYING OUT THE INVENTION The MnZn-based ferrite of the present invention contains Fe ₂ O ₃ in an amount of 52.60 to 53.00 mol%, and Fe ₂ O ₃ and ZnO must satisfy the condition of the following formula (1). I have to. 1.25 × Fe ₂ O ₃ −42.00 ≦ ZnO ≦ 1.25 × Fe ₂ O ₃ −40.25 Formula (1) The inventor of the present invention disclosed in Japanese Patent Laid-Open No. 6-263447 and Japanese Patent Laid-Open No. 10-256025.
Even in the composition range of the MnZn-based ferrite, which is disclosed in Japanese Patent Publication No. JP-A-2003-264, which has a high magnetic permeability even at a relatively low temperature,
The phenomenon in which the initial magnetic permeability is low at a low temperature such as ˜0 ° C. was examined. As a result, in the MnZn-based ferrite, the composition ranges of the individual components are not solely defined independently, but the secondary peak temperature of the initial permeability and the Curie temperature change due to the mutual amount relationship between Fe ₂ O ₃ and ZnO. However, unless this relation satisfies the relation of equation (1), −30
It has been found that a composition range having a high initial magnetic permeability cannot be obtained at a low temperature 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 combination range of nO is limited to the range of formula (1),
It is not clear why the initial magnetic permeability can be 10,000 or more even at around room temperature while maintaining the initial magnetic permeability of 8,000 or more at a low temperature of -30 to 0 ° C. Generally, MnZn
When the amount of Fe ₂ O ₃ in the system ferrite is high, the Curie temperature is high and the secondary peak temperature is low. When the amount of ZnO is high, the Curie temperature is low and the secondary peak temperature is low. 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 the temperature is −30.
It was noted that the initial magnetic permeability cannot be set to 10,000 or more even at around room temperature while maintaining the initial magnetic permeability of 8,000 or more in the temperature range of ℃ or more. The present inventor, by studying the relationship between the mutual amounts of Fe ₂ O ₃ and ZnO, lowers the secondary peak temperature below room temperature while ensuring the required Curie temperature, and improves the initial permeability in the low temperature region. I made a hypothesis that it can be raised. From this idea, various experiments were conducted, and as shown in FIG. 2, the initial magnetic permeability at 10 kHz was 8,000 or more in the temperature range of −30 to 90 ° C.
The composition range of 10,000 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
It was found to be the range surrounded by four points (3.00, 24.25). Furthermore, it was newly found that the initial magnetic permeability at 10 kHz at 23 ° C. can be set to 11,000 or more in a range surrounded by these four points with the ZnO amount exceeding 25.00 mol%. This is expressed by the following equation (2). _{25.00 <ZnO ≦ 1.25 × Fe 2} O 3 -40.25 formula (2)

Now, as described above, Fe ₂ O ₃ , ZnO,
Determining the basic composition of MnO is of course of utmost importance, but it is difficult to obtain a high initial permeability over the entire desired temperature range with this alone. It has been newly found that the above problems can be solved by limiting the amounts of impurities, especially boron and phosphorus. As an effect of boron on the initial magnetic permeability of MnZn-based ferrite, for example, in page 92 of the document “Ferrite” (Hiraga et al., Maruzen, 1986), the crystal structure is made non-uniform to prevent the development of high initial magnetic permeability. Must be kept below 50 ppm,
Is described. However, this initial magnetic permeability is a description intended for the initial magnetic permeability only at room temperature when the secondary peak is set at room temperature as described above, and it is as wide as −30 to 90 ° C. as in the present invention. Nothing is said about the effect of boron in achieving high initial permeability over the temperature range. Further, phosphorus is not described in the above literature at all. In addition, `` 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. Regarding the effect of high magnetic permeability MnZn-based ferrites on the temperature characteristics of initial magnetic permeability, Not mentioned at all.

In this regard, the present inventor has found that the temperature is -30 to 90 ° C.
In order to suppress the nonuniformity of the structure such as abnormal grains and to realize a stable high initial permeability in a region over a wide temperature range of Fe ₂ O
The relationship between the 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 Fe ₂ O ₃ , ZnO, and 100 mol% of MnO, preferably 4ppm or less, phosphorus amount 15p
It has been newly found that it is necessary to set pm, preferably 11.2 ppm or less. It is very difficult to remove boron and phosphorus in the intermediate steps such as the firing step once they are mixed in the manufacturing process of MnZn-based ferrite, so it is especially necessary to keep the amount of boron and phosphorus within the specified range in the raw iron oxide. Is preferred.

The MnZn-based ferrite of the present invention has the above composition as an essential constituent element, 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. Examples of such MnZn-based ferrite include 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
Examples thereof include O ₅ -Bi ₂ O _3, but the present invention is not limited to these examples.

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

[0015]

EXAMPLES Next, the present invention will be explained based on examples.

Using iron oxides having various amounts of boron and phosphorus, various Fe ₂ O ₃ and ZnO as shown in Table 1 were used.
After mixing the raw materials so that the balance is MnO with the composition of
It was calcined at 0 ° C. for 3 hours. Add calcium oxide to CaO
At 0.011 to 0.028 wt%, Bi bismuth oxide
₂ O ₃ was added in the range of 0.015 to 0.035 wt%, crushed with a ball mill for 8 hours, molded into a ring-shaped core, and then heated at a heating rate of 250 ° C./h in the atmosphere to 1100.
The temperature was raised from 500C to a nitrogen atmosphere at a heating rate of 500C / h, and after reaching the holding temperature of 1370C, the oxygen concentration was controlled to 10% by volume or less for 5 hours before firing. The temperature change of the initial magnetic permeability of the obtained sintered body at 10 kHz was measured from −30 ° C. to 120 ° C. The present invention is described in Example No. Comparative Examples Nos. 1 to 8 for comparison. 1-14
showed that. In addition, in Example No. 5 and Comparative Example No. 8, N
o. The temperature dependence of the initial magnetic permeability of No. 13 is shown in FIG. Further, Table 1 shows the amounts of boron and phosphorus contained in each sintered body, and the amounts of added calcium oxide and bismuth oxide.

As can be seen from Table 1 and FIG. 1, in the examples of the present invention, temperatures of -30 ° C., -20 ° C., -10 ° C., -23 ° C.
The initial permeability at 10 kHz is 100 at each temperature of 90 ° C.
Indicates 00 or more. Also, more preferably, 23 ° C., 10
It is shown that the initial magnetic permeability at kHz is 11,000 or more.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

The MnZn-based ferrite of the present invention is -3
High initial magnetic permeability in a wide temperature range of 0 to 90 ° C (initial magnetic permeability in the temperature range of -30 ° C to 90 ° C is 8000 or more, -2
Since it has an initial magnetic permeability of 10000 or more in the temperature range of 0 ° C. to 90 ° C., it is possible to obtain a very useful material for applications such as a pulse transformer operating in a wide temperature range.

[Brief description of drawings]

FIG. 1 shows an example No. 5 , Comparative Example No. It is a figure which shows the temperature characteristic of 8 and 13 initial magnetic permeability.

2 is an example No. 1 to 8 and Comparative Example No. It is a plot of the amount of Fe ₂ O ₃ and ZnO of 1-9.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01F 1/12-1/38

Claims (2)

(57) [Claims] 1. A MnZn-based ferrite comprising 52.60 to 53.00 mol% Fe ₂ O ₃ , ZnO mol% under the condition of the following formula (2) , and the balance Mn.
In a total of 100 mol% of O, boron is contained by 5 ppm or less by weight, phosphorus is contained by 15 ppm or less by weight , and initial permeability at 10 kHz is within a temperature range of -30 to 90 ° C.
A MnZn-based ferrite characterized in that it is 10000 or more . _{25.00 <ZnO ≦ 1.25 × Fe 2} O 3 -40.25 formula (2) 2. The MnZn-based ferrite further contains at least one or more 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, which is characterized.