JP6064315B2 - Magnetic oxide sintered body, and antenna and wireless communication device using the same - Google Patents

Description

The present invention relates to a magnetic oxide sintered body suitable for antenna use, and an antenna and a wireless communication device using the same.

In recent years, the radio signal frequency used in wireless communication devices such as mobile phones and portable information terminals has been increased. For example, in the first generation mobile phone, the use frequency was in the 800 MHz band, whereas in the third generation mobile phone, the service of which was started in 2001, the use frequency has increased to the 2 GHz band. There is a demand for an antenna that can be used in the GHz band including Bluetooth (registered trademark) and wireless LAN applications. In addition, with the multi-functionalization of wireless communication devices, multi-band mode has been developed to support multiple wireless systems, and antennas used in such wireless communication devices can be used in a wide frequency band. It is also required to be possible. Furthermore, with the recent miniaturization of wireless communication devices, further miniaturization of the antenna itself has become an urgent issue. Thus, antennas used in recent wireless communication devices are eagerly desired to achieve both high bandwidth and small size.

With regard to such technology, for example, Patent Document 1 discloses a chip type having a microstrip structure for obtaining a small size, a low profile, a high gain, and a wide band characteristic by appropriately selecting the shapes of the radiation electrode and the ground electrode. An antenna element is described. Patent Document 2 describes a hexagonal ferrite containing Y-type ferrite as a main phase and an antenna using the hexagonal ferrite. Further, Patent Document 3 proposes an antenna using a nanocomposite magnetic dielectric material in which superparamagnetic magnetic nanoparticles are dispersed in a nonmagnetic matrix as an electromagnetic coupling regulator. Furthermore, Patent Document 4 describes a composite magnetic material in which a magnetic oxide mainly composed of Co-substituted W-type hexagonal ferrite is dispersed in a resin, and an antenna using the same. Furthermore, Patent Document 5 describes an antenna device including an insulator layer made of an oxide-based magnetic material made of a Y-type, Z-type, or M-type ferrite compound.

Japanese Patent No. 3625191 International Publication No. 2006/064839 Pamphlet JP 2008-228227 A JP 2010-238748 A JP 2005-278067 A JP 2006-117515 A

Here, regarding the miniaturization of the antenna, the wavelength shortening rate of the electromagnetic wave is equal to the rate of decrease of the phase velocity of the electromagnetic wave in the transmission medium, and the phase velocity is theoretically the product of the relative permeability and the relative dielectric constant of the medium. In general, the wavelength of the electromagnetic wave propagating in the antenna by using a material having a larger permeability and / or dielectric constant than that in a vacuum as the base material or matrix of the antenna. Can be shortened and the size can be reduced. Specifically, the wavelength λ of the electromagnetic wave (radio wave) passing through the magnetic material is represented by λ∝1 / √ (μ′r × ε′r) (wavelength shortening effect). Here, the factor μ′r indicates the real part of the complex relative permeability μr of the magnetic material, and the factor ε′r indicates the real part of the complex relative permittivity εr of the magnetic material. The “wavelength shortening rate” here is a value represented by “wavelength of electromagnetic wave propagating through transmission medium / wavelength of electromagnetic wave in vacuum”. The smaller this value, the higher the wavelength shortening effect. Indicates.

In this regard, for example, Japanese Patent Laid-Open No. 2004-228561 has a description regarding miniaturization of an antenna by increasing a relative dielectric constant. However, when a base material with a large relative dielectric constant is used in the antenna described in Patent Document 1, the frequency band where high efficiency is obtained is narrowed, and as a result, the usable frequency band is limited to an inconvenient level. End up.

In addition, when a magnetic material such as Y-type hexagonal ferrite described in Patent Document 2 is used, the magnetic loss in the high frequency band of GHz or higher becomes excessive. In this case, the usable frequency band is inconvenient. It will be limited to a certain extent.

Furthermore, in the antenna described in Patent Document 3, since the particle diameter of the magnetic nanoparticles used is literally on the order of nanometers, the dispersibility in the resin material as the dispersion medium is insufficient, It is difficult to obtain sufficient antenna performance due to the difficulty of high filling. In addition, it is difficult to say that such magnetic nanoparticles are suitable for mass production of products because the handling property is inferior and the manufacturing cost is increased.

On the other hand, the composite magnetic material described in Patent Document 4 by the present applicant has an advantage that magnetic loss and dielectric loss at high frequencies can be reduced because W-type ferrite is used. However, since W-type ferrite has a relatively low magnetic permeability, and the composite formed by mixing W-type ferrite with a resin is adopted, the overall magnetic permeability is further reduced. The composite magnetic material described in 1) may be insufficient from the viewpoint of further miniaturizing the antenna by sufficiently reducing the wavelength shortening rate described above.

On the other hand, although Patent Document 5 discloses ferrites having various compositions as antenna materials as described above, their detailed material properties are unknown, and generally antennas using such materials are used. However, there is a possibility that the magnetic loss in the high frequency band of GHz or higher becomes large.

M-type ferrites with various compositions have been studied extensively as ferrite magnets. However, when used as magnets, M-type ferrite causes a significant decrease in coercive force, which is one of the magnet characteristics. Is generally suppressed and the reduction of the anisotropic magnetic field is suppressed (Patent Document 6). An antenna using M-type ferrite for such a ferrite magnet may also have a large magnetic loss in a high frequency band of GHz or higher.

Therefore, the present invention has been made in view of such circumstances. In the composition of the M-type hexagonal ferrite, a range satisfying the efficiency as an antenna accompanying reduction of magnetic loss and dielectric loss is found, and in the high frequency band, the broadband An object is to provide an antenna that can be used and has high efficiency. Furthermore, since it has a higher real permeability relative to the conventional dielectric material (μ′r = 1) and the magnetic material, the product of the magnetic permeability and the dielectric constant of the entire material is lower than that of the conventional material. Thus, the wavelength shortening effect is effectively enhanced, and the wavelength of the electromagnetic wave to be received can be shortened. As a result, the antenna can be miniaturized. At the same time, the powder particle size at the material stage is sufficiently large, about 1 μm, so that it is superior in handling properties compared to the case of using the above conventional magnetic nanoparticles and can prevent an increase in the cost of manufacturing the antenna. As a result, an object of the present invention is to provide a magnetic oxide sintered body that is excellent in handling and economy at the time of manufacture and can realize a small antenna suitable for mass production, and an antenna and a wireless communication device using the same. And

In order to solve the above problems, the present inventor has intensively studied paying attention to the composition and physical properties of ferrite having a specific crystal structure, and as a result, has found an effective means for solving the above problems and completed the present invention. It came to do.

That is, the magnetic oxide sintered body according to the present invention has the following general formula (1):
MA _α [Fe _β MB _γ Mn _δ ] O ₁₉ (1)
M-type hexagonal ferrite represented by the following formula and having an average crystal grain size of 5 μm or more.

In the general formula (1), MA is at least one selected from the group consisting of Sr and Ba, MB is at least one selected from the group consisting of Ti, Sn, and Zr, and 1 ≦ α <1.4, 7 ≦ β ≦ 11, 11.8 ≦ β + (γ + δ) ≦ 12.1, 1 ≦ δ / γ ≦ 1.2.

In the above, the “main phase” refers to a component contained in the magnetic oxide sintered body as a main component (a component having a ratio of more than 50 mass% with respect to the entire crystal particles). Further, the “average crystal particle diameter (major diameter)” is a median diameter D50% measured by a method specifically described in Examples described later.

When the inventors measured the characteristics of an antenna manufactured using a magnetic oxide sintered body having such a configuration, the antenna has an effective bandwidth and efficiency in a high frequency band as compared with the conventional antenna. It was confirmed to be excellent. The details of the action mechanism that produces such advantageous effects are not yet clear, but are estimated as follows, for example. However, the action is not limited to them (the same applies hereinafter).

In the magnetic oxide sintered body containing the ferrite having the above-described composition and having an average crystal grain size of 5 μm or more, the M-type hexagonal ferrite as the main phase is added to the main component metals (MA and Fe). Since the secondary component metal (MB, Mn) is contained, the magnetocrystalline anisotropy energy is lowered, and the natural resonance frequency f0 (n) is shifted to a lower frequency side. At the same time, the real part μ′r of the complex relative permeability is further increased. More specifically, natural resonance appears in a frequency band of about 5 GHz or more, and magnetic loss due to natural resonance at frequencies lower than that is sufficiently suppressed. In addition, since the magnetic oxide sintered body is sufficiently grown so that the average crystal particle diameter is particularly 5 μm or more, the resonance of the domain wall becomes prominent in an alternating magnetic field having a lower frequency, that is, the domain wall resonance frequency. f0 (d · w) shifts to a lower frequency side. More specifically, the domain wall resonance appears in a frequency band of about 1 GHz or less, and the magnetic loss due to the domain wall resonance at a frequency exceeding that is sufficiently suppressed. As a result, the permeability loss coefficient tanδμ (imaginary part μ ”r of complex relative permeability μr / real part μ′r of complex relative permeability μr) is effective over a wide high frequency band of about 1 to 5 GHz. It is presumed that an excessive decrease in antenna efficiency due to an increase in magnetic loss is effectively suppressed.

Furthermore, the magnetic oxide sintered body described above contains an excessive amount of MA as compared with a normal M-type stoichiometric composition, and the ratio of the subcomponent metals MB and Mn is an Mn excess composition. Loss factor tan δε (imaginary part ε ″ r of complex relative permittivity εr / real part ε′r of complex relative permittivity εr) is effectively reduced, and excessive reduction in antenna efficiency due to increased dielectric loss Is presumed to have been effectively suppressed.

In addition, since it has a higher real permeability real part than a conventional dielectric material (μ′r = 1) and a magnetic material, the permeability and dielectric of the entire material in a wide frequency band of about 1 to 5 GHz. As a result, the wavelength shortening effect can be effectively enhanced and the wavelength of the electromagnetic wave to be received can be shortened. As a result, the antenna can be miniaturized. At the same time, the powder particle size at the material stage is sufficiently large, about 1 μm, so that it is superior in handling properties compared to the case of using the above conventional magnetic nanoparticles and can prevent an increase in the cost of manufacturing the antenna. As a result, the mass productivity and economic efficiency of the product can be significantly improved.

In addition, by growing the average crystal grain size (major axis) to 100 μm or more, the domain wall resonance frequency f0 (d · w) is shifted to a lower frequency side. As a result, the domain wall resonance in the antenna operating frequency range occurs. The resulting magnetic loss can be further reduced.

Furthermore, the magnetic oxide sintered body according to the present invention can reduce the dielectric loss by increasing the ratio of Mn ³⁺ to the total amount of Mn contained and reducing the ratio of Fe ^{2+ to} the total amount of Fe. Efficiency is improved. In particular, the ratio of Mn ^{3+ to} the total amount of Mn is preferably 5% or more, and the ratio of Fe ^{2+ to} the total amount of Fe is preferably 0.2% or less.

The magnetic oxide sintered body preferably has a natural resonance frequency f0 (n) of 5 GHz or more and a domain wall resonance frequency f0 (d · w) of 0.5 GHz or less.

The antenna according to the present invention can be effectively manufactured using the magnetic oxide sintered body of the present invention, and a base including the magnetic oxide sintered body and a conductor provided on the surface or inside of the base And a power supply terminal connected to the conductor and supplying electric energy to the conductor.

Furthermore, a wireless communication device according to the present invention is obtained effectively using the antenna of the present invention, and is characterized by including the antenna of the present invention described above.

According to the magnetic oxide sintered body of the present invention, since the specific M-type hexagonal ferrite is included as the main phase and the average crystal particle diameter is 5 μm or more, the bandwidth is sufficiently increased in the high frequency band. While maintaining a wide range, the wavelength of the electromagnetic wave to be received can be shortened to reduce the size of the antenna and the wireless communication device including the antenna, and the handling in the manufacturing process is easy (high handling). It is also very suitable for mass production, and as a result, the characteristics, productivity, and economics of antennas and wireless communication devices using the same can be improved.

It is a perspective view which shows notionally the structure of suitable one Embodiment of the antenna formed using the magnetic oxide sintered compact concerning this invention. It is a top view which shows schematic structure of suitable one Embodiment of a radio | wireless communication apparatus provided with the antenna using the magnetic oxide sintered compact concerning this invention.

Hereinafter, embodiments of the present invention will be described in detail. The positional relationship such as up, down, left, and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios. Furthermore, the following embodiment is an illustration for explaining the present invention, and is not intended to limit the present invention only to the embodiment. Furthermore, the present invention can be variously modified without departing from the gist thereof.

[Magnetic oxide sintered body]
The magnetic oxide sintered body of the present embodiment contains M-type hexagonal ferrite as the main phase, and the average crystal particle diameter D50 is 5 μm or more. The M-type hexagonal ferrite has the following formula (1):
MA _α [Fe _β MB _γ Mn _δ ] O ₁₉ (1)
In the formula, “MA” is at least one selected from the group consisting of Sr and Ba, “MB” is at least one selected from the group consisting of Ti, Sn, and Zr, α, β, γ, and δ are 1 ≦ α <1.4 (preferably 1 <α <1.2), 7 ≦ β ≦ 11 (preferably 7.5 ≦ β ≦ 9), and 11.8, respectively. ≦ β + (γ + δ) ≦ 12.1 (preferably 11.9 ≦ β + (γ + δ) ≦ 12.0), 1 ≦ δ / γ ≦ 1.2 (preferably 1.05 ≦ δ / γ ≦ 1. 2).

Further, the magnetic oxide sintered body of the present embodiment may include a single phase of M-type hexagonal ferrite represented by the above formula (1) or a phase different from that of M-type hexagonal ferrite. Good.

According to the magnetic oxide sintered body whose composition is controlled in this way, the M-type hexagonal ferrite contained as the main phase contains the subcomponent metals (MB and Mn) in addition to the main component metals (MA and Fe). As a result, the real part of the complex relative permeability is further increased, and the crystal is sufficiently grown so that the average crystal particle diameter is 5 μm or more. Therefore, the domain wall resonance frequency f0 (d · w) is set to a lower frequency side. Can be shifted to. As a result, the loss factor tan δμ of the magnetic permeability can be remarkably reduced over a wide high frequency band of about 1 to 5 GHz. As a result, the antenna efficiency is sufficiently reduced due to the increase in magnetic loss. Can be deterred. Further, from the viewpoint of shifting the domain wall resonance to the low frequency side and reducing the magnetic loss due to the domain wall resonance in the antenna operating frequency range, the average crystal particle diameter (major axis) is more preferably 100 μm or more.

Further, the magnetic oxide sintered body described above contains an excessive amount of MA as compared with a normal M-type stoichiometric composition, and the ratio of the subcomponent metals MB and Mn is an Mn excess composition. It is possible to reduce the rate loss coefficient tan δε. Similarly, by increasing the ratio of Mn ³⁺ to the total amount of Mn contained and reducing the ratio of Fe ^{2+ to} the total amount of Fe, it is possible to reduce the loss factor of the dielectric constant, resulting from an increase in dielectric loss. An excessive decrease in antenna efficiency is effectively suppressed, and the antenna efficiency is improved.

When the ratio of Mn3 + to the total amount of Mn contained in the magnetic oxide sintered body is less than 5%, the dielectric loss coefficient increases and the antenna efficiency decreases.

If the ratio of Fe2 + to the total amount of Fe contained in the magnetic oxide sintered body is greater than 0.2%, the dielectric loss coefficient increases and the antenna efficiency decreases.

In the formula (1), when α <1, the ratio of Fe 2+ to the total Fe amount increases, leading to an increase in dielectric loss coefficient and a decrease in antenna efficiency. On the other hand, when 1.4 ≦ α, the complex permeability μ ′ decreases, and the wavelength shortening effect becomes insufficient.
When β <7, natural resonance appears on the lower frequency side than 5 GHz, and the magnetic loss coefficient due to natural resonance increases in the antenna operating frequency range, leading to a decrease in antenna efficiency. On the other hand, when 11 <β, the magnetocrystalline anisotropy energy is not sufficiently lowered, the complex permeability μ ′ is lowered, and the wavelength shortening effect is insufficient.
When β + (γ + δ) <11.8, an increase in α due to charge compensation is observed, the complex permeability μ ′ decreases, and the wavelength shortening effect becomes insufficient. On the other hand, when 12.1 <β + (γ + δ), α decreases due to charge compensation, the ratio of Fe 2+ to the total Fe amount increases, leading to an increase in dielectric loss coefficient and a decrease in antenna efficiency.
If δ / γ <1, the ratio of Fe 2+ to the total Fe amount increases, leading to an increase in dielectric loss coefficient and a decrease in antenna efficiency. On the other hand, when 1.2 <δ / γ, the ratio of Mn3 + to the total amount of Mn decreases, leading to an increase in magnetic loss coefficient, an increase in dielectric loss coefficient, and a decrease in antenna efficiency.
If the average crystal particle diameter (major axis) is less than 5 μm, the domain wall resonance appears at a frequency higher than 0.5 GHz, the magnetic loss coefficient due to the domain wall resonance increases in the antenna operating frequency region, and the antenna efficiency decreases. .

Considering these points, the magnetic oxide sintered body of the present embodiment has a natural resonance frequency f0 (n) of 5 GHz or more and a domain wall resonance frequency f0 (d · w) of 0.5 GHz or less. Is preferable.

Furthermore, in addition to the magnetic component containing M-type hexagonal ferrite as the main phase, at least one subcomponent selected from the group consisting of SiO2, CaO, and Bi2O3 is within a range that does not depart from the operational effects of the present invention. You may make it contain.

[antenna]
FIG. 1 is a perspective view conceptually showing a configuration of a preferred embodiment of an antenna formed using a magnetic oxide sintered body of the present invention. The antenna 1 has at least one conductor 4 formed on the surface and / or inside of a base 2. The base 2 is formed using the magnetic oxide sintered body of the present embodiment described above, and the shape thereof is not particularly limited, and various shapes required when mounted on a wireless communication device are adopted. In general, for example, a rectangular parallelepiped block shape as shown in FIG. 1 is preferably used.

When such a substrate 2 is a sintered body, it can be manufactured by a normal ceramic manufacturing process. An example will be described. First, each raw material is weighed so that the composition after sintering becomes a desired composition, wet-mixed for a predetermined time, and from a metal compound containing a metal element constituting the M-type hexagonal ferrite. A ferrite precursor is prepared. The metal compound includes an iron (Fe) compound, a manganese (Mn) compound, and another metal (MA, MB) compound. As the raw material, for example, an iron compound such as Fe ₂ O _{3 is} oxidized. Oxides such as Mn ₃ O ₄ as manganese (Mn) compounds, carbonates such as BaCO ₃ (SrCO ₃ ), and oxides such as TiO ₂ , ZrO ₂ , and SnO ₂ as other metal compounds it can.

In addition, for example, a ball mill or a bead mill using a steel medium, a mixer, a stirrer, a disperser, or the like can be appropriately applied to the wet mixing process.

Next, the ferrite precursor is calcined at an appropriate temperature and time, for example, in the atmosphere, and then pulverized for an appropriate time to obtain an M-type hexagonal ferrite powder (powder). On the other hand, if necessary, an additive known in the art such as a dispersant that disappears in the subsequent baking treatment may be added to the powder.

Then, the prepared raw material powder is granulated by an appropriate method, formed into a desired shape at a predetermined pressure, and then the molded body is heat-treated (fired) at an appropriate atmosphere and at an appropriate temperature for an appropriate time. As a result, the substrate 2 which is a sintered body is obtained. The average crystal particle size of the sintered body can be formed to grow from a fine crystal particle size of 1 μm or less to 5 μm or more by appropriately controlling the firing conditions. Similarly, by appropriately controlling the firing conditions, the ratio of Fe ²⁺ to the total amount of Fe contained in the sintered body and the ratio of Mn ³⁺ to the total amount of Mn contained can be increased or decreased. For example, the higher the processing temperature and the longer the processing time, the larger the average crystal particle diameter of the sintered body tends to be. In addition, by setting the oxygen partial pressure during firing high, the Fe ²⁺ ratio tends to decrease and the Mn ³⁺ ratio tends to increase. Specifically, the processing temperature is appropriately set in an atmosphere of 1100 ° C. to 1380 ° C. and an oxygen partial pressure of 0% to 100%, and the ratio of Fe ²⁺ to the total amount of Fe contained in the sintered body is contained. The ratio of Mn ^{3+ to} the total amount of Mn was adjusted.

The conductor 4 formed on one surface of the base 2 can be formed by, for example, copper or copper alloy by an appropriate method such as printing, vapor deposition, bonding, or plating. In FIG. 4, a power supply terminal 6 provided on the other surface of the base 2 is electrically connected. The shape of the conductor 4 is not particularly limited, and may be various shapes such as a meander shape and a helical shape in addition to a flat sheet shape or a flat film shape as shown in FIG. The power supply terminal 6 is a terminal for electrically connecting the conductor 4 and an external power supply line, and a voltage supplied from a predetermined power supply line is applied to the conductor 4 via the power supply terminal 6. Is done.

[Wireless communication equipment]
FIG. 2 is a plan view (front view) illustrating a schematic configuration of a preferred embodiment of a wireless communication device including an antenna using the magnetic oxide sintered body of the present invention. The mobile phone 10 that is a wireless communication device is a kind of a foldable mobile terminal in which a first housing 10CA and a second housing 10CB are connected by a hinge 13, and the frequency band used is, for example, 2 GHz. It is. A first antenna 11 (antenna) is disposed at the end located on the opposite side of the hinge 13 side in the second housing 10CB. The first antenna 11 is a transmission / reception antenna used for wireless communication of the mobile phone 10 and is used for transmission / reception of radio waves for exchanging data such as calls and e-mails between the mobile phone 10 and a base station. It is done.

In addition, a second antenna 12 (antenna) is disposed inside the second housing 10CB at a portion opposite to the hinge 13 side. The second antenna 12 is, for example, a receiving antenna used for receiving GPS radio signals, and is used for receiving radio waves transmitted from GPS satellites. The frequency band thereof is, for example, 1.5 GHz band.

In the mobile phone 10 having such a configuration, the base of the first antenna 11 is formed using the magnetic oxide sintered body according to the present invention, whereby the first antenna 11 can be reduced in size. The first antenna 11 can be used in a wide band (for example, several tens of MHz) at a frequency (2 GHz band in the above example) used for the wireless communication of the mobile phone 10. In addition, since the first antenna 11 can be reduced in size, the degree of freedom of arrangement of devices, parts, wiring, etc. provided in the mobile phone 10 is increased, thereby reducing the size of the casing of the mobile phone 10. You can also plan.

The base of the second antenna 12 is also formed using a magnetic oxide sintered body that is a magnetic material for an antenna according to the present invention, whereby the second antenna 12 can be miniaturized, In the frequency band used for receiving the GPS radio signal, the second antenna 12 can be used in a wide band (for example, several tens of MHz). Furthermore, although the second antenna 12 usually tends to be limited in the arrangement of the mobile phone 10 in the casing, according to the present embodiment, the second antenna 12 can be reduced in size. It is also possible to improve the degree of freedom of arrangement of the second antenna 12.

In addition, as above-mentioned, this invention is not limited to said each embodiment, A various deformation | transformation is possible in the limit which does not change the summary. For example, the magnetic oxide sintered body according to the present invention is not limited to the antenna 1 and the antenna of the mobile phone 10, and is applicable to all wireless communication devices using the GHz band, particularly 2 to 5 GHz band. Can do. In addition to portable devices, the wireless communication device according to the present invention includes, for example, indoor and outdoor antennas for mobile phones, wireless LAN transceivers (parent devices, slave devices), and the like. Among them, it is extremely useful particularly for those requiring miniaturization.

Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1-15 and Comparative Examples 1-9)
Each raw material powder was prepared so that the magnetic oxide sintered body had a composition ratio indicated by α, β, γ, and δ in Table 1, and samples for evaluating physical properties and characteristics of each Example and each Comparative Example were prepared. The raw material powder was prepared by wet mixing of each material in a steel ball mill for 16 hours, calcining the mixed powder in the atmosphere at 1200 ° C. for 2 hours and then pulverizing in a steel ball mill for 20 hours. did. The raw material powder is fired by granulating the raw material powder into a predetermined shape at a pressure of 100 MPa, and then molding the molded body in an atmosphere having an oxygen partial pressure of 0 to 100% (20% in Example 8). In Example 9, it was set to 100%, and the others were finely adjusted so as to be the target Fe ²⁺ ratio and Mn ³⁺ ratio by using these as indices, and a temperature of 1100 to 1380 ° C. (in Example 1, 1350 ° C. In Example 2, the temperature was 1300 ° C., and the others were finely adjusted according to the target average crystal particle diameter using these as indices.

(Reference Example 1)
A sample for evaluating physical properties and characteristics of Reference Example 1 was prepared in the same manner as in the above Examples and Comparative Examples, except that dielectric powder based on the formula CaTiO3 was used as a raw material powder.

(Physical properties and property evaluation)
<Average crystal particle size>
The surface of the sintered compact sample after etching with concentrated hydrochloric acid was observed with a scanning electron microscope and determined from an average of N = 150. At that time, the average crystal particle diameter was obtained by multiplying the length of the long side of the circumscribed square that minimizes the area for each particle by π / 2.
<Fe ²⁺ / Fe, Mn ³⁺ / Mn>
The composition analysis and the determination of Fe ²⁺ and Mn ³⁺ were performed. In the composition analysis, the sintered body was pulverized and powdered, and then measured by a glass bead method using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, Simultic 3530). The amount of Fe 2+ was determined by potentiometric titration using 200 mg of the above powdered sample after adding oxalic acid and strong phosphoric acid to dissolve with heating, adding degassed water, and using an N / 500 K2Cr2O7 solution. The amount of Mn ³⁺ is obtained by adding potent phosphoric acid to 200 mg of the above powdered sample, dissolving by heating, adding degassed water, potentiometric titration using an N / 100 ferrous ammonium sulfate solution, and the previously obtained value of Fe ²⁺ amount. I asked more.

<Material constant>
A ring-shaped sample (outer diameter 7 mm × inner diameter 3.04 mm × thickness 1 to 2 mm) is molded from each of the prepared sintered powders of the raw materials, and the complex relative permeability of each ring-shaped sample obtained at room temperature of 25 ° C. The real part μr ′, the imaginary part μr ″, and the magnetic loss tan δμ of the magnetic susceptibility μr were derived from the results of S parameters at a frequency of 0.1 to 18 GHz measured using a network analyzer (manufactured by Agilent: HP8510C). In addition, a rod-shaped sample (1 mm × 1 mm × 80 mm) was molded from each of the prepared sintered powders of raw materials, and the real part εr ′, imaginary number of the complex relative permittivity εr at room temperature of 25 ° C. of each rod-shaped sample obtained. The part εr ″ and the dielectric loss tan δε were measured by the cavity resonator perturbation method at a frequency of 2 GHz using the network analyzer.

Furthermore, from the frequency dependence of the imaginary part μr ″ of the complex relative permeability of each ring-shaped sample, the natural resonance frequency f0 (n) (the frequency at which the value of the imaginary part μ ″ peaks in a frequency band of 5 GHz or higher). And the domain wall resonance frequency f0 (d · w) (frequency at which the value of the imaginary part μ ″ has a peak in a frequency band of 1 GHz or less).

<Antenna characteristics>
A rectangular parallelepiped block-shaped sample (10 mm × 3 mm × 4 mm) is molded from each of the prepared sintered powders of raw materials, and an electrode is formed on the surface of each obtained rectangular parallelepiped block-shaped sample (an electrode pattern depending on each sample). Each chip type antenna having a resonance frequency of 1.5 GHz having a configuration substantially equivalent to that shown in FIG. 1 was manufactured. From the radiation efficiency measured by using a small 3D radiation directivity measuring instrument (SATIMO: STARLAB) with each of the obtained chip-type antennas mounted on a flat substrate and one end of the electrode connected to the feeding electrode, Radiation efficiency and bandwidth (frequency range centered on 1.5 GHz where the radiation efficiency is 50% or more) were evaluated.

The obtained measurement evaluation results are summarized in Tables 1 and 2. From these results, the magnetic oxide sintered bodies and antennas of the examples according to the present invention have a natural resonance frequency f0 (n) of 5 GHz or more and a domain wall resonance frequency f0 (d · w) of 0.5 GHz or less. For example, the real part (μ′r) of the complex relative permeability at 2 GHz is 1.2 or more, and the magnetic loss (loss coefficient tan δμ) is 0.01 or less. Further, the magnetic material for the antenna has a real part (ε′r) of a complex relative dielectric constant at 2 GHz of 25 or less and a dielectric loss (a loss coefficient tan δε of dielectric constant) of 0.01 or less. As compared with those of the comparative example and the reference example, the superiority in the radiation efficiency and the bandwidth was confirmed.

As described above, according to the magnetic oxide sintered body of the present invention, the specific M-type hexagonal ferrite is included as a main phase, and the average crystal particle diameter is 5 μm or more, so that at a high frequency. Since it is possible to reduce the size of the antenna and the wireless communication device including the antenna while maintaining high efficiency and a sufficiently wide bandwidth, it is also possible to improve productivity and economy. A magnetic oxide sintered body according to the present invention, and an antenna and a wireless communication device using the magnetic oxide sintered body are useful for widening and reducing the size of antennas for high frequency signals such as 1 GHz or more. , DV camera, PND, car navigation system, game machine, PDA, personal computer, indoor antenna, wireless LAN transceiver, information communication card, etc. Communication devices and mobile communication devices, and systems and facilities provided with them, can be utilized widely and effectively.

DESCRIPTION OF SYMBOLS 1 Antenna 2 Base | substrate 4 Conductor 6 Feeding terminal 10 Mobile phone (wireless communication apparatus)
10CA First housing 10CB Second housing 11 First antenna (antenna)
12 Second antenna (antenna)
13 Hinge.

Claims (6)

MA _α [Fe _β MB _γ Mn _δ ] O ₁₉ (wherein MA is at least one selected from the group consisting of Sr and Ba, and MB is at least one selected from the group consisting of Ti and Zr) M type hexagonal ferrite represented by 1 ≦ α <1.4, 7 ≦ β ≦ 11, 11.8 ≦ β + (γ + δ) ≦ 12.1, 1 ≦ δ / γ ≦ 1.2) A magnetic oxide sintered body which is included as a main phase and has an average crystal particle diameter (major axis) of 5 μm or more , wherein the ratio of Mn ³⁺ to the total amount of Mn contained in the magnetic oxide sintered body is 5% or more. Furthermore, the ratio of Fe ²⁺ to the total amount of Fe contained in the magnetic oxide sintered body is 0.2% or less, and the magnetic oxide sintered body is characterized in that: The magnetic oxide sintered body according to claim 1, wherein the M-type hexagonal ferrite is MA. _α [Fe _β MB _γ Mn _δ ] O ₁₉   (In the formula, MA is at least one selected from the group consisting of Sr and Ba, MB is at least one selected from the group consisting of Ti and Zr, and 1 <α <1.4, 7 The magnetic oxide sintered body according to claim 1, characterized by: ≦ β ≦ 11, 11.8 ≦ β + (γ + δ) ≦ 12.1, 1 <δ / γ ≦ 1.2) . The magnetic oxide sintered body according to claim 1, wherein the average crystal particle diameter (major axis) is 100 μm or more. The magnetic oxide according to any one of claims 1 to 3 , wherein the natural resonance frequency f0 (n) is 5 GHz or more and the domain wall resonance frequency f0 (d · w) is 0.5 GHz or less. Sintered body. A base including the magnetic oxide sintered body according to any one of claims 1 to 4 , a conductor provided on or in the surface of the base, connected to the conductor, and the conductor An antenna including a power supply terminal for supplying electric energy. A wireless communication device comprising the antenna according to claim 5 .

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