JPH0353270B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a new manganese-zinc ferrite magnetic material with low loss and low residual magnetic flux density. Manganese-zinc ferrite is widely used as a transformer material in various communications equipment and consumer equipment, but recently there has been a trend toward using higher frequency power supplies to miniaturize power supplies, and it is suitable for this purpose. Properties as transformer materials have come to be required. The properties required of manganese-zinc ferrite for use in high-frequency power supplies include high density, high resistance, high magnetic permeability, high saturation magnetic flux density, low residual magnetic flux density, and low power loss near the operating temperature of the transformer. There is. Until now, various trace components have been added to improve the electromagnetic properties of manganese-zinc ferrite, such as combined addition of CaCO ₃ -SiO ₂ (Japanese Patent Publication No. 36-2283) and SnO ₂ - It is known that the magnetic core properties are improved by TiO ₂ composite addition (Japanese Patent Publication No. 51-48276). However, although these manganese-zinc ferrites show considerable improvement in characteristics in terms of eddy current loss, etc., they are still not fully satisfactory in terms of power loss at high temperatures. In order to develop manganese-zinc ferrite suitable for transformer materials for high-frequency power supplies, the inventors of the present invention have conducted intensive research and have added niobium oxide as a trace component and heated and sintered it using an appropriate manufacturing process. The inventors have discovered that very excellent electromagnetic properties can be obtained when using the same method, and based on this finding, the present invention has been accomplished. Hitherto, it has been known to add niobium oxide to manganese-zinc ferrite to make it have high magnetic permeability and low loss (Japanese Patent Publication No. 38-23421).
However, the ferrite obtained in this way shows high magnetic permeability and low eddy current loss in the low frequency region and room temperature region, but under the harsh conditions of 100KHz and 100℃ or more for high frequency power supply. , the above characteristics are significantly deteriorated and it cannot be put to practical use. The present invention overcomes these difficulties by adding innovation to the manufacturing process.
This provides a magnetic material with completely new properties. That is, in producing manganese-zinc ferrite, the present invention adds niobium oxide or a compound Nb ₂ O ₅ which produces niobium oxide as a trace component to the raw material mixture at a ratio of 0.02 to 0.10% by weight in terms of Nb 2 O 5. B-H is characterized in that it is then heated to a predetermined sintering temperature through a gradual heating step under atmospheric pressure and a rapid heating step in an atmosphere with controlled oxygen concentration, and combustion is completed at this temperature.
Bm/Br of the loop is 3.0 or more and 100K
Power loss is 450m under Hz, 2000G, 100℃ conditions
The present invention provides a method for manufacturing a magnetic material having a W/cc or less. Niobium oxide is added in the method of the present invention to enable low-temperature, high-density sintering and to effectively improve the magnetic core properties, but this is in the range of 0.02 to 0.10% by weight based on the total amount of raw materials. It is necessary to contain it within the range. If this amount is less than 0.02% by weight, the magnetic core characteristics will not be improved no matter how the manufacturing conditions are controlled, and if this amount is less than 0.10% by weight
If it exceeds this, it becomes difficult to control the sintering process, resulting in deterioration of the magnetic core properties. In the magnetic material obtained by the method of the present invention, it is not necessary to specifically contain components other than iron oxide, manganese oxide, zinc oxide, and niobium oxide;
Impurities caused by raw materials, contaminants mixed in during the manufacturing process, or other trace components that do not inhibit the effects of niobium oxide, such as CaCO ₃ , SiO ₂ ,
Additions such as Ta ₂ O ₅ and TiO ₂ are allowed. The method of the invention requires that the magnetic material be manufactured according to a controlled and specific manufacturing process. That is, according to the method of the present invention, in producing manganese-zinc ferrite, after adding a compound that produces niobium oxide as a trace component to the raw material mixture at a ratio of 0.02 to 0.10% by weight calculated as Nb ₂ O ₅ . The above magnetic material can be obtained by raising the temperature to a predetermined sintering temperature through a gradual heating step under atmospheric pressure and a rapid heating step in an atmosphere with controlled oxygen concentration, and completing sintering at that temperature. can. As the main raw material in the method of the present invention, a mixture of an iron oxide component, a manganese oxide component, and a zinc oxide component is used. This iron oxide component includes Fe ₂ O ₃ ,
In addition to oxides such as FeO and Fe ₃ O ₄ , compounds that can be converted into iron oxide by firing, such as iron hydroxide and iron oxalate, are used. Further, as the manganese oxide component, in addition to oxides such as MnO, MnO ₂ , and Mn ₃ O ₄ , compounds that can be converted into manganese oxide by firing, such as manganese carbonate and manganese oxalate, are used. Furthermore, as zinc oxide, in addition to oxides such as ZnO, zinc carbonate,
Compounds that can be converted to zinc oxide by calcination, such as zinc oxalate, are used. These iron oxide components, manganese oxide components, and zinc oxide components have a ratio of 52 to 54.5 mol% in terms of Fe ₂ O ₃ , 25 to 37 mol% in terms of MnO, and 7 to 21 mol% in terms of ZnO, respectively, as the final composition of the magnetic material. It is mixed so that it becomes the same and used as a raw material. Generally speaking, the niobium oxide contained in the magnetic material of the present invention is usually added as Nb ₂ O ₅ to the raw material mixture, but it can be converted into Nb ₂ O in the final product by calcination, such as carbonate or oxalate. ₅ can also be used. In order to suitably produce a desired magnetic material by the method of the present invention, first, the raw material mixture is calcined at a temperature of 800 to 1000°C, the calcined product is crushed, and a small amount of a suitable binder such as polyvinyl alcohol is added thereto. and mold it. Next, this molded product is placed under atmospheric pressure.
200-350 to a specified temperature within the range of 800-1100℃
After rapid heating at a heating rate of ℃/hr, the temperature rises to 1000~
Slow heat to a preselected temperature within the range of 1150°C at a heating rate of 30-70°C/hr. Next, in an atmosphere with controlled oxygen concentration, the material is rapidly heated to the required sintering temperature at a heating rate of 200 to 350°C/hr.
Sintering is completed at that temperature. The firing atmosphere conditions at this time are preferably a nitrogen atmosphere with an oxygen concentration controlled to about 0.1 to 5%.
This is carried out by maintaining a predetermined temperature in the range of 1250 to 1350°C for 1 to 10 hours. The cooling process after sintering is completed in this way is carried out in an atmosphere where the oxygen concentration is controlled according to the temperature from the sintering temperature to about 1100-1200℃, and thereafter in an inert atmosphere, such as a nitrogen atmosphere. is preferable. The cooling rate is usually in the range of 200 to 350°C/hr. The magnetic material obtained in this way has a B-H loop Bm/Br of 3.0 or more, a frequency of 100 KHz, a magnetic flux density of 2000 G, and a power loss of 100°C.
It is characterized by a property of 450mW/cc or less. In other words, this magnetic material has a saturation magnetic flux density
Since Bm is large and residual magnetic flux density Br is small,
At the same time as Bm-Br becomes large, it also has the characteristics of low power loss in high frequency, high magnetic flux density, and high temperature regions. Therefore, this magnetic material is suitable as a magnetic core of a transformer for high frequency power supply. Next, the present invention will be explained in more detail with reference to Examples. Example 1 Fe ₂ O ₃ 53.7 mol%, ZnO 10.6 mol% and
CaCO ₃ and Nb ₂ O ₅ in amounts shown in Table 1 were added as trace components to a raw material mixture consisting of 5.7 mol % of MnO3, calcined at 950°C according to a conventional method, and then ground in a wet ball mill. It was made into a powder with an average particle size of 1.0μ. Next, polyvinyl alcohol is added as a binder to this calcined product, formed into a ring shape, heated to 900℃ in the atmosphere, and then heated to 1050℃ for 50 minutes.
The temperature was gradually increased at a temperature increase rate of °C/hr. Then 300℃/hr up to 1320℃ in an atmosphere containing 0.5% oxygen
After heating up rapidly at a temperature increase rate of 3 hours and completing sintering by holding at this temperature for 3 hours, the furnace was turned off and cooling started. When the temperature reached 1200℃, the atmosphere was switched to pure nitrogen and the temperature was lowered to room temperature. Cooled. Table 1 shows the magnetic properties of the six types of magnetic materials thus obtained.

[Table] As can be seen from this table, the addition of CaCO ₃ is effective in reducing the residual magnetic flux density (Br), but it also reduces the saturation magnetic flux density (Bm) and therefore increases Bm/Br. cannot be obtained. On the other hand, addition of Nb ₂ O ₅ increases Bm and decreases Br, so Bm/Br increases significantly. Furthermore, the power loss under high frequency, high magnetic flux density, and high temperature ranges is significantly lowered by the addition of Nb ₂ O ₅ , particularly by the addition of about 0.05% by weight. Example 2 CaCO ₃ , Nb ₂ O ₅ and trace components were added to manganese-zinc ferrite having the same composition as in Example 1.
V ₂ O ₅ was added and the magnetic core properties were measured. The same conditions as in Example 1 were used as the manufacturing conditions for the magnetic material at this time. The results obtained are shown in Table 2.

[Table] It is known that adding an appropriate amount of V ₂ O ₅ to manganese-zinc ferrite improves weak magnetic field characteristics such as μi and tanδ/μi, but as is clear from this table, Nb ₂ O ₅ Comparable improvement in weak magnetic field characteristics is also observed by adding . Example 3 Using the same composition as Sample 5 of Example 1 but changing the processing conditions, a magnetic material was manufactured and its magnetic core characteristics were measured. The results are shown in Table 3. The processing conditions used at this time were as follows. Treatment conditions: The same conditions as for the heat treatment in Example 1 were used. Processing conditions: The sample was heated to 900°C in the atmosphere, slowly heated to 1050°C at a heating rate of 50°C/hr, and then rapidly heated to 1320°C at a heating rate of 300°C/hr. Next, the sintering was completed by heating at 1320°C for 3 hours in a nitrogen atmosphere containing 0.5% oxygen, and then the heating was stopped and allowed to cool.
When the temperature was reached, the atmosphere was switched to pure nitrogen and cooled to room temperature. In this process, the temperature curve up to the stable temperature is the same as the process conditions, but the difference is that the atmosphere control to reach the stable temperature after slow heating at 1050° C. or higher is omitted. Processing conditions: The sample was heated to 1050°C in the air without an annealing process, and then heated to 1320°C for 300°C in a nitrogen atmosphere containing 0.5% oxygen.
Rapidly heat the mixture at a heating rate of °C/hr and hold at this temperature for 3 hours to complete combustion. Next, heating was stopped and allowed to cool, and when the temperature reached 1200°C, the atmosphere was switched to pure nitrogen and further cooled to room temperature. This treatment differs from the treatment conditions in that an annealing step from 900°C to 1050°C is not performed. Processing conditions: sample in the atmosphere up to 1320℃
After rapid heating at a heating rate of 300°C/hr, heating in a nitrogen atmosphere containing 0.5% oxygen for 3 hours to complete combustion, heating was stopped and allowed to cool until it reached 1200°C. Then, the atmosphere was changed to pure nitrogen and cooled to room temperature. This treatment differs from the treatment conditions in that the annealing step and the atmosphere control to reach a stable temperature of 1050° C. or higher are omitted.

[Table] As is clear from this table, regarding B-H characteristics and power loss in high frequency, high magnetic flux density, and high temperature regions, the processing conditions have the lowest power loss, and the annealing process under atmospheric pressure and oxygen concentration control If it is missing, power loss will increase.

Claims (1)

[Claims] 1. In producing manganese-zinc ferrite, niobium oxide or a compound that produces niobium oxide upon calcination is added as a trace component to the raw material mixture using Nb ₂ O ₅
After adding at a ratio of 0.02 to 0.10% by weight,
The B-H loop is characterized by raising the temperature to a predetermined combustion temperature through a gradual heating process under atmospheric pressure and a rapid heating process in an atmosphere with controlled oxygen concentration, and completing combustion at this temperature. Bm／Br
is 3.0 or higher, and 100KHz, 2000G, 100℃
A method for manufacturing a magnetic material that has a power loss of 450 mW/cc or less under the following conditions.