JP7028020B2 - Dielectric compositions and electronic components - Google Patents

Description

The present invention relates to dielectric compositions and electronic components.

There is a high demand for higher performance of mobile communication devices such as smartphones, and for example, the number of frequency domains used is increasing in order to enable high-speed, large-capacity communication. The frequency domain used is a high frequency region such as the GHz band. Some high-frequency components such as baluns, couplers, filters, or duplexers and diplexers combined with filters that operate in such a high-frequency region use a dielectric material as a resonator. Such a dielectric material is required to have a small dielectric loss and good frequency selectivity in a high frequency region.

In addition, as the performance of mobile communication devices increases, the number of electronic components mounted on one mobile communication device tends to increase, and in order to maintain the size of the mobile communication device, the size of the electronic components is small. At the same time, conversion is required. In order to reduce the size of high-frequency components that use a dielectric material, it is necessary to reduce the electrode area. Therefore, in order to compensate for the decrease in capacitance due to this, the relative permittivity of the dielectric material is high in the high-frequency region. Desired.

Such mobile communication devices are exposed to temperature changes due to the usage environment, heat generation of parts used in the devices, and the like. On the other hand, since the resonance frequency of a high-frequency component using a dielectric material changes depending on the temperature, the dielectric material is required to have a small temperature dependence of the resonance frequency, that is, a small temperature coefficient of resonance frequency within a predetermined temperature range. ..

Therefore, the dielectric material applied to the high-frequency component used in the high-frequency region is required to have a small dielectric loss, a high relative permittivity, and a small resonance frequency temperature coefficient in the high-frequency region. Since the reciprocal of the dielectric loss can be expressed as the no-load quality coefficient Qu, in other words, the dielectric constant and the no-load quality coefficient Qu are high in the high frequency region, and the resonance frequency temperature coefficient is small in a predetermined temperature range. Body materials are desired.

Conventionally, a Bi—Zn—Nb—O oxide is known as a material having a high dielectric constant in a high frequency region. For example, Patent Document 1 discloses a mixture of Bi ₃ NbO ₇ phase and Bi ₂ (Zn _2/3 Nb _4/3 ) O ₇ phase. Further, Patent Document 2 discloses a sintered body obtained by mixing Bi ₂ O ₃ , ZnO and Nb ₂ O ₅ at a predetermined ratio and firing them.

Special Table 2009-537444 Gazette Japanese Unexamined Patent Publication No. 4-285046

However, in Patent Document 1, the absolute value of the temperature coefficient of the dielectric constant is 10 ppm or less for a mixture in which the Bi ₃ NbO ₇ phase and the Bi ₂ (Zn _2/3 Nb _4/3 ) O ₇ phase are mixed at a ratio of 1: 1. However, since the relative permittivity is 100 or less and the dielectric quality coefficient Q at 1 GHz is about 1000, the dielectric property in the high frequency region is not sufficient.

Further, in Patent Document 2, the absolute value of the temperature coefficient of the dielectric constant is 100 ppm or less and the relative permittivity of the sintered body obtained by mixing Bi ₂ O ₃ , ZnO and Nb ₂ O ₅ at a predetermined ratio and firing. Is 140 or less, and the no-load Q value at 1 GHz is 400 or less, so that the dielectric property in the high frequency region was not sufficient.

The present invention has been made in view of such circumstances, and a dielectric composition having a high relative permittivity εr and no-load quality coefficient Qu in a high frequency region and a small absolute value of resonance frequency temperature coefficient τf in a predetermined temperature range is provided. The purpose is to provide.

In order to achieve the above object, the present invention
[1] A dielectric composition having a composite oxide containing bismuth, zinc and niobium.
When the composite oxide is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} , x, y and z are x + y + z = 1.00, 0.31 ≦ y ≦ 0.50, 2/3 ≦ x. It is a dielectric composition characterized by satisfying the relationship of / z ≦ 3/2.

[2] The dielectric composition according to [1], wherein y satisfies the relationship of 0.40 ≦ y ≦ 0.50.

[3] The dielectric composition according to [1] or [2], wherein x and z satisfy the relationship of 1.20 ≦ x / z ≦ 1.50.

[4] The dielectric composition according to [1] or [2], wherein x and z satisfy the relationship of 0.90 ≦ x / z ≦ 1.10.

[5] An electronic component comprising the dielectric composition according to any one of [1] to [4].

According to the present invention, it is possible to provide a dielectric composition having a high relative permittivity εr and no-load quality coefficient Qu in a high frequency region and a small absolute value of the resonance frequency temperature coefficient τf in a predetermined temperature range.

FIG. 1 is a perspective view of a single-layer capacitor as an electronic component according to the present embodiment.

Hereinafter, the present invention will be described in detail in the following order based on specific embodiments.
1. 1. Electronic components 1.1. Overall configuration of single-layer capacitor 1.2. Dielectric layer 1.2.1. Dielectric composition 2. Manufacturing method of electronic parts 3. Effect in this embodiment 4. Modification example

(1. Electronic components)
First, a single-layer capacitor will be described as an example of the electronic components according to the present embodiment.

(1.1. Overall configuration of single-layer capacitor)
As shown in FIG. 1, the single-layer capacitor 100 according to the present embodiment includes a columnar dielectric layer 11 and a pair of electrodes 10A formed on a pair of facing surfaces which are both main surfaces of the dielectric layer 11. It is equipped with 10B. The dielectric layer 11 and the pair of electrodes 10A and 10B form a capacitor portion, and when the pair of electrodes 10A and 10B are connected to an external circuit and a voltage is applied, the dielectric layer 11 is predetermined. It shows the capacitance and can function as a capacitor.

The conductive material contained in the electrodes 10A and 10B is not particularly limited, and can be arbitrarily set according to desired characteristics, applications, and the like. In this embodiment, for example, silver (Ag), gold (Au), copper (Cu), platinum (Pt) and the like are exemplified.

Although the dielectric layer 11 has a cylindrical shape in FIG. 1, the shape of the dielectric layer 11 is not particularly limited and can be arbitrarily set according to desired characteristics, applications, and the like. Further, the dimensions of the dielectric layer 11 are not particularly limited, and can be arbitrarily set according to desired characteristics, applications, and the like.

(1.2. Dielectric layer)
In this embodiment, the dielectric layer 11 is composed of the dielectric composition shown below.

(1.2.1. Dielectric composition)
The dielectric composition according to the present embodiment contains a composite oxide containing bismuth (Bi), zinc (Zn) and niobium (Nb) as a main component. In the present embodiment, the main component is a component that occupies 90% by mass or more with respect to 100% by mass of the dielectric composition.

The composite oxide has a pyrochlore-type crystal structure. The pyrochlore-type crystal structure is represented by the general formula A ₂ B ₂ O ₇ . In the pyrochlore-type crystal structure, oxygen is eight-coordinated to the element occupying A site (A site element), and oxygen is six-coordinated to the element occupying B site (B site element). Then, the BO ₆ octahedron in which the B-site element is located in the center of the octahedron composed of oxygen constitutes a three-dimensional network in which the vertices of each other are shared, and the A-site element is located in the gap of this network and A. The site element is located in the center of a hexahedron composed of oxygen.

In the present embodiment, the general formula A ₂ B ₂ O ₇ can be represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} . That is, the above-mentioned composite oxide has a pyrochlore-type crystal structure and is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} . In this composition formula, "x", "y" and "z" are x + y + z = 1.00.

Further, in the composite oxide, the amount of oxygen (O) may be a stoichiometric ratio or may be slightly deviated from the stoichiometric ratio. The amount of deviation from the stoichiometric ratio varies depending on the type of element to be substituted and the amount of substitution thereof, and is represented by "δ" in the above composition formula.

Therefore, "x" indicates the content ratio of Bi among the metal elements in the composition formula of the above composite oxide, and "y" is the content of Zn among the metal elements in the composition formula of the above composite oxide. The ratio is shown, and "z" indicates the content ratio of Nb among the metal elements in the composition formula of the above composite oxide.

In the above general formula, Bi occupies the A site and Nb occupies the B site. On the other hand, Zn can occupy both A site and B site in the above general formula. Therefore, in the pyrochlore-type crystal structure of the above-mentioned composite oxide, in addition to the hexahedron in which oxygen is 8-coordinated to Bi and the octahedron in which oxygen is 6-coordinated to Nb, the hexahedron in which oxygen is 8-coordinated to Zn and Zn. There is an octahedron in which oxygen is coordinated in six.

In the composite oxide containing Bi, Zn and Nb and having a pyrochlore-type crystal structure, the proportion of the polyhedron in which oxygen is coordinated with Zn affects the stability of the pyrochlore-type crystal structure. Therefore, in the present embodiment, "y" indicating the Zn content ratio is controlled to 0.31 or more and 0.50 or less. Further, "y" is preferably 0.40 or more.

By setting "y" within the above range, the proportion of hexahedrons in which oxygen is 8-coordinated to Zn and octahedrons in which oxygen is 6-coordinated to Zn increases in the pyrochlorite crystal structure, and the polyhedra in the crystal structure. Structural variation is suppressed, and structural changes due to temperature changes are less likely to occur. As a result, the resonance frequency tends to be kept constant even if the temperature changes, so that the absolute value (| τf |) of the resonance frequency temperature coefficient τf can be set within a predetermined range.

If "y" is too small, the proportion of the hexahedron in which oxygen is 8-coordinated to Bi and the octahedron in which oxygen is 6-coordinated to Nb increases in the pyrochlore type crystal structure, and the variation in the polyhedral structure becomes large, resulting in structural changes. Since it tends to be easy to do, the resonance frequency temperature coefficient τf tends to deteriorate. On the other hand, if "y" is too large, the proportion of the polyhedron in which oxygen is coordinated with Zn becomes too large, and the component that contributes to the relative permittivity in the composite oxide decreases, so that the relative permittivity εr tends to deteriorate. be.

Further, in the present embodiment, "x / z" indicating the Bi content ratio ("x") with respect to the Nb content ratio ("z") is 2/3 or more and 3/2 or less. By setting "x / z" to the above range, the Bi content ratio and the Nb content ratio are relatively close to each other, so that defects in the pyrochlore type crystal structure are reduced and the no-load quality coefficient Qu is improved. can do.

"X / z" is preferably 1.20 or more and 1.50 or less. By setting it within the above range, the disorder of the crystal structure (disorder) occurs in the A site within an appropriate range. Therefore, while maintaining the no-load quality coefficient Qu well, the relative permittivity is caused by this disorder. The coefficient εr can be further improved. If "x / z" is too large, the disorder tends to be too large, and conversely, the no-load quality coefficient Qu tends to decrease.

Further, it is also preferable that "x / z" is 0.90 or more and 1.10 or less. By setting the content within the above range, the Bi content ratio and the Nb content ratio are almost the same, so that the number of defects in the pyrochlore type crystal structure is further reduced, and the no-load quality coefficient Qu can be further improved. ..

By setting "x", "y" and "z" within the above ranges in the above composition formula, the relative permittivity εr, the no-load quality coefficient Qu, and the resonance frequency temperature coefficient τf are improved. be able to.

Further, the dielectric composition according to the present embodiment may contain a trace amount of impurities, subcomponents and the like within the range in which the effect of the present invention is exhibited. Examples of such a component include Mn, Ca, Ba and the like.

(2. Manufacturing method of electronic parts)
Next, as an example of the method of manufacturing the electronic component, an example of the method of manufacturing the single-layer capacitor 100 shown in FIG. 1 will be described below.

First, a starting material for the dielectric composition is prepared. As a starting material, a metal oxide contained in the composite oxide constituting the above-mentioned dielectric composition, a mixture thereof, or a composite oxide can be used. In addition, various compounds that become the above-mentioned oxides and composite oxides by firing, such as carbonates, oxalates, nitrates, hydroxides, and organic metal compounds, can be appropriately selected and mixed for use. For example, Bi ₂ O ₃ powder, Zn O powder and Nb ₂ O ₅ powder may be prepared. The average particle size of each powder is preferably 1.0 μm or less.

The prepared starting materials are weighed so that the final composition has a desired composition, and then mixed to obtain a mixture. As a method of mixing, wet mixing or dry mixing may be used. In the case of wet mixing, the dispersion medium at the time of mixing is not particularly limited, but for example, water, lower alcohols and the like can be used. Further, these may be mixed and used.

In the case of wet mixing, the mixture is dried to obtain a mixed powder. The obtained mixed powder is usually calcined. The calcining is performed at a temperature lower than the firing temperature.

When the obtained calcination powder is agglomerated, it is preferable to roughly pulverize the calcination powder for a predetermined time using a ball mill or the like to obtain pulverized powder. The average particle size of the coarsely pulverized powder may be about 0.5 to 3.0 μm. When wet pulverization is performed, one or more dispersion media used in the above wet mixing may be mixed and used.

The method for forming the pulverized powder is not particularly limited. Usually, about 2.0 to 5.0 parts by weight of a binder may be added to 100 parts by weight of the crushed powder and mixed, and then pressure molding may be performed. As the binder, polyvinyl alcohol or the like is usually used. The pressure molding may be carried out under the condition that a mold of an appropriate size is filled with crushed powder mixed with a binder or the like and the molding pressure is about 2 to 5 t / cm ² .

Subsequently, the obtained molded product is fired. The firing conditions are not particularly limited. For example, the temperature rise rate may be about 50 to 300 ° C./h, the firing temperature may be about 1000 ° C. to 1100 ° C., the holding time may be about 12 hours, and the atmosphere may be an oxygen atmosphere such as in the atmosphere.

Terminal electrodes are printed on the main surface of the obtained sintered body and baked as necessary to form electrodes. The method for forming the electrode is not particularly limited, and the electrode may be formed by vapor deposition, sputtering, or the like.

By going through the above steps, the single-layer capacitor shown in FIG. 1 can be obtained.

(3. Effect in this embodiment)
In this embodiment, Bi-Zn-Nb-O-based oxides are focused on as a composite oxide having a pyrochlore-type crystal structure. In this composite oxide, Zn can occupy both A-sites and B-sites, forming two types of polyhedra. The present inventors have found that by increasing the ratio of these two types of polyhedra, the pyrochlore-type crystal structure is stabilized and structural changes due to temperature changes are less likely to occur. Therefore, in the present embodiment, the resonance frequency temperature coefficient τf is improved by setting the Zn content ratio in the pyrochlore-type crystal structure within the above range.

In addition, the present inventors reduced the defects of the pyrochlore-type crystal structure by making the content of Bi occupying the A site and the content of Nb occupying the B site relatively close to each other, resulting in no-load quality. We also found that the coefficient Qu is improved. Therefore, in the present embodiment, a high no-load quality coefficient Qu is obtained by setting the ratio of the Bi content ratio and the Nb content ratio within the above range.

Specifically, the dielectric composition according to the present embodiment exhibits a high relative permittivity εr of 150 or more and a high no-load quality coefficient Qu of 2500 or more even in a high frequency region of 2 GHz or more, and also resonates. The absolute value of the frequency temperature coefficient τf can be 30 ppm / ° C. or less.

Further, a dielectric composition that emphasizes obtaining a high relative permittivity εr by changing the value of x / z, and a dielectric composition that emphasizes obtaining a high no-load quality coefficient Qu. Can be obtained according to the application.

(4. Modification example)
In the above-described embodiment, the single-layer capacitor in which the dielectric layer is a single layer has been described as the electronic component, but the electronic component may be a laminated capacitor. Such a laminated capacitor has a laminated body having a structure in which a plurality of dielectric layers composed of the above-mentioned dielectric composition and internal electrode layers are alternately laminated. A pair of terminal electrodes conducting with the internal electrode layer are formed at both ends of the laminated body. The shape of the laminated body is not particularly limited, but it is usually a rectangular parallelepiped shape. Further, the dimensions are not particularly limited, and may be appropriate dimensions according to the intended use.

Further, the electronic component may be a thin film capacitor. In this case, the dielectric layer of the thin film capacitor may be composed of the above-mentioned dielectric composition. The dielectric layer of this thin film capacitor can be formed by depositing the elements constituting the above-mentioned dielectric composition on a substrate by using, for example, a thin film forming method or the like. As the thin film forming method, a known vapor phase growth method such as a sputtering method or a chemical vapor deposition method is preferable.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and may be modified in various ways within the scope of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.

First, powders of bismuth oxide (Bi ₂ O ₃ ), zinc oxide (Zn O) and niobium oxide (Nb ₂ O ₅ ) were prepared as starting materials for the composite oxide which is the main component of the dielectric composition. The average particle size of each powder was 1.0 μm or less. The above starting materials were weighed so that the dielectric composition (sintered body) after firing had the composition shown in Table 1.

Next, each weighed starting raw material powder was wet-mixed with a ball mill for 16 hours using ethanol as a dispersion medium, and the mixture was dried to obtain a mixed raw material powder. Then, the obtained mixed raw material powder was heat-treated in the air under the conditions of a holding temperature of 800 ° C. and a holding time of 2 hours to obtain a calcined powder.

The obtained calcined powder was roughly pulverized and wet-pulverized with a ball mill using ethanol as a dispersion medium to obtain pulverized powder.

Polyvinyl alcohol was added as a binder to the obtained pulverized powder, and the mixture was mixed and granulated by a known method. The obtained granulated powder was processed and molded into a cylinder having a diameter of 12 mm and a height of 8 mm by a press molding machine to obtain a molded product. The obtained molded product was fired at 1000 ° C. for 12 hours to obtain a dielectric composition (sintered product). Both end faces of the obtained sintered body were polished to form electrodes, and a sample was prepared.

The relative permittivity εr and the no-load quality coefficient Qu at a measurement frequency of 2 to 5 GHz were measured for the obtained sample by the parallel conductor plate type dielectric resonator method. In this example, a sample having a relative permittivity εr of 150 or more was good, and a sample having a no-load quality coefficient Qu of 2500 or more was good. The resonance frequency temperature coefficient τf was calculated by measuring the resonance frequency at 25 ° C. and 80 ° C. and using the value at 25 ° C. as a reference. In this embodiment, a sample having an absolute value (| τf |) of the resonance frequency temperature coefficient τf of 30 ppm or less is considered to be good. The results obtained are shown in Table 1.

From Table 1, in the composite oxide containing Bi, Zn and Nb, the sample in which the relationship of “x”, “y” and “z” is within the above-mentioned range has a high relative permittivity εr in the high frequency region (2 GHz). It was confirmed that it had (150 or more), a high no-load quality coefficient Qu (2500 or more), and good temperature characteristics (| τf | ≦ 30 ppm / ° C.).

Further, by limiting the Zn content ratio (“y”), it has better temperature characteristics (| τf | ≦ 15 ppm / ° C.) while maintaining a high relative permittivity εr and a high no-load quality coefficient Qu. I was able to confirm that.

Further, by increasing "x / z", that is, increasing the content ratio of Bi, a higher relative permittivity εr (180 or more) can be obtained while maintaining a high no-load quality coefficient Qu and good temperature characteristics. It was confirmed that it could be obtained.

Further, by making "x / z" close to 1, that is, by making the Bi content ratio and the Nb content ratio almost the same, the relative permittivity εr and the good temperature characteristics are maintained and higher. It was confirmed that the no-load quality coefficient Qu (3000 or more) can be obtained.

According to the present invention, it is possible to obtain a dielectric composition having a high relative permittivity and Qu in a high frequency region and a small resonance frequency temperature coefficient in a predetermined temperature range. Such a dielectric composition is suitable for high frequency electronic components such as baluns, couplers, filters, or duplexers and diplexers combined with filters.

100 ... Single-layer capacitor 10A, 10B ... Terminal electrode 11 ... Dielectric layer

Claims (4)

A dielectric composition having a composite oxide containing bismuth, zinc and niobium.
When the composite oxide is represented by the composition formula Bi _x Zn _y Nb _z O _{1.75 + δ} , the x, y and z are x + y + z = 1.00, 0.40 ≦ y ≦ 0.50, 2/3. A dielectric composition characterized by satisfying the relationship of ≦ x / z ≦ 3/2. The dielectric composition according to claim 1, wherein x and z satisfy the relationship of 1.20 ≦ x / z ≦ 1.50. The dielectric composition according to claim 1, wherein x and z satisfy the relationship of 0.90 ≦ x / z ≦ 1.10. An electronic component comprising a dielectric layer containing the dielectric composition according to any one of claims 1 to 3 .

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