JP3397099B2 - Dielectric porcelain composition and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition used for, for example, a monolithic ceramic capacitor and a method for producing the same.

[0002]

2. Description of the Related Art Hitherto, as a dielectric ceramic composition having a high dielectric constant, a low dielectric loss, and a low dielectric constant temperature characteristic, JP-A-7-22 has been known.
The one disclosed in Japanese Patent No. 0525 is known. Further, in recent years, in response to the demand for smaller size and larger capacity of the monolithic ceramic capacitor, the ceramic dielectric effective layer of the monolithic ceramic capacitor has been rapidly thinned and highly laminated. Corresponding to this, in addition to high permittivity, low permittivity loss, and flat permittivity-temperature characteristic, higher withstand voltage characteristic has been demanded as performance required for the dielectric ceramic material.

[0003]

However, the above-mentioned conventional dielectric ceramic composition is a dielectric material excellent in high dielectric constant, low dielectric loss, and flat dielectric constant temperature characteristics, but has a low withstand voltage. There was a problem such as.

The present invention solves the above-mentioned conventional problems, and has a high dielectric constant, a low dielectric loss, a flat dielectric constant temperature characteristic,
An object of the present invention is to provide a dielectric ceramic composition having a high withstand voltage characteristic and suitable for thinning and highly laminating a ceramic dielectric effective layer in a monolithic ceramic capacitor.

[0005]

In order to achieve the above object, the dielectric ceramic composition of the present invention has a specific surface area of 0.8 to
In a dielectric porcelain composition containing barium titanate adjusted to 2.8 m ² / g as a main component and at least niobium pentoxide, nickel oxide, and strontium oxide as sub-components, pentoxide was added to barium titanate. 0.8 to 2.0 wt% of niobium, nickel oxide and strontium oxide in a weight ratio to niobium pentoxide of 3 ≦ niobium pentoxide / (nickel oxide + strontium oxide) ≦ 8
(However, nickel oxide and strontium oxide are 0
When it is wt%, it is possible to achieve the intended purpose.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises, as a main component, barium titanate whose specific surface area is adjusted to 0.8 to 2.8 m ² / g, and at least niobium pentoxide as a subcomponent. In a dielectric porcelain composition containing nickel oxide, nickel oxide, and strontium oxide, 0.8 to 2.0 wt% of niobium pentoxide is added to the barium titanate, and nickel oxide and strontium oxide are added to niobium pentoxide. A dielectric porcelain composition characterized in that the ratio is 3 ≦ niobium pentoxide / (nickel oxide + strontium oxide) ≦ 8 (except when nickel oxide and strontium oxide are 0 wt%). By adding niobium pentoxide to barium titanate with a controlled specific surface area, the dielectric loss is reduced and the withstand voltage is increased. By adding strontium, it has the effect that the dielectric constant temperature characteristic be flat.

According to a second aspect of the present invention, with respect to barium titanate whose specific surface area is controlled, 0.02 of silicon dioxide is added.
The dielectric porcelain composition according to claim 1, containing 5 to 0.30 wt%, which is further sintered while maintaining high dielectric constant, flat dielectric constant temperature characteristics, low dielectric loss, and high withstand voltage characteristics. It has the effect of improving the sex.

According to a third aspect of the present invention, 0.05 to 0.40 wt% of either lanthanum oxide or cerium oxide is contained in barium titanate whose specific surface area is controlled. The dielectric porcelain composition according to, having a high dielectric constant similar to that of silicon dioxide, a flat dielectric constant temperature characteristic,
It defines an oxide element and its content that can further improve the sinterability while maintaining low dielectric loss and high withstand voltage characteristics.

According to a fourth aspect of the present invention, any one selected from neodymium oxide, samarium oxide and dysprosium oxide is added to barium titanate having a controlled specific surface area in an amount of 0.05 to 0. The dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition contains 50 wt%, and has a high dielectric constant, a flat dielectric constant temperature characteristic, a low dielectric loss, similar to silicon dioxide.
It defines an oxide element and its content that can further improve the sinterability while maintaining the high withstand voltage characteristics.

According to a fifth aspect of the present invention, in contrast to barium titanate whose specific surface area is controlled, ytribium oxide,
Or, one of praseodymium oxide is 0.05 to
The dielectric ceramic composition according to claim 1, containing 0.70 wt% of the dielectric ceramic composition, which has a high dielectric constant, a flat dielectric constant temperature characteristic, a low dielectric loss, and a high withstand voltage characteristic as in the case of silicon dioxide. It defines an oxide element capable of improving its sinterability and its content.

According to a sixth aspect of the present invention, nickel oxide and strontium oxide are contained in a weight ratio of 3 ≦ niobium pentoxide / (nickel oxide + strontium oxide) ≦ 8 (provided that nickel oxide and strontium oxide are used). , Except that when strontium oxide is 0 wt%), the material having a specific surface area of 0.8 to 2.8 m ² /
A method for producing a dielectric ceramic composition, characterized in that niobium pentoxide is added to 0.8 to 2.0 wt% to barium titanate adjusted to g, and a small amount of nickel oxide is added. , And strontium oxide were mixed with niobium pentoxide, and then added to fine powder of barium titanate adjusted to have a specific surface area of 0.8 to 2.8 m ² / g. , And strontium oxide are uniformly mixed with barium titanate, which has the effect of producing a dielectric ceramic composition having excellent characteristics with good reproducibility.

Next, one embodiment of the present invention will be described based on a concrete example. (Embodiment 1) This embodiment corresponds to the invention described in claim 1 and is one in which niobium pentoxide, nickel oxide, and strontium oxide are added to barium titanate whose specific surface area is adjusted.

First, 900 to 900 barium titanate fine powder having an average particle size of 0.1 μm and a purity of 99.99% or more, which is produced by a hydrothermal synthesis reaction using titanium hydroxide and barium hydroxide is used.
Powder calcination was performed at a temperature of 1150 ° C. to obtain a specific surface area of 0.
Barium titanate adjusted to sizes of 4, 0.8, 1.2, 2.8, and 3.0 m ² / g is prepared.

Next, each barium titanate whose specific surface area was adjusted so as to have the composition shown in (Table 1), niobium pentoxide, nickel oxide, and strontium oxide were weighed, and the diameter was 5 mm in a polyethylene container. The zirconia cobblestone and pure water were mixed for 20 hours.

[0015]

[Table 1]

In Table 1, niobium pentoxide is represented as Nb, nickel oxide is represented as Ni, and strontium oxide is represented as Sr. Further, the sample No. 16 in (Table 1) is a predetermined amount of Nb, N
Only the additives of i and Sr were premixed with pure water in the polyethylene container for 10 hours in advance, barium titanate was added, and the mixture was further mixed for 20 hours.

After drying the mixed slurry, 9 wt% of a 5% polyvinyl alcohol aqueous solution was added to the mixture for granulation, and then this granulated powder was formed into a disk having a diameter of 15 mm and a thickness of 0.5 mm at 1 ton / cm ^2. Was molded under pressure. Then 1300
After baking for 2 hours at a temperature of ~ 1400 ° C and baking silver electrodes on both sides of the obtained sintered body, a sample for measurement was prepared. Then, at each room temperature, the dielectric constant was applied at a frequency of 1 kHz and a capacitance of 1 Vrms. The dielectric loss was measured by applying 50 Vrms / mm. The withstand voltage was calculated by applying a direct current voltage in silicon oil at a boosting rate of 50 V per second and converting the broken voltage into a unit thickness. Further, the temperature change rate characteristic of the dielectric constant was obtained by dividing the dielectric constant measured in the range of -60 ° C to 135 ° C by the dielectric constant of 20 ° C.

A sample whose sintered density did not reach 95% of the theoretical density at a firing temperature of 1400 ° C. or lower was judged not to be sintered, and the measurement of electrical characteristics was omitted.

The results are shown in (Table 2).

[0020]

[Table 2]

As shown in (Table 2), No. 1 having a specific surface area of barium titanate produced by the hydrothermal method of less than 0.8 m ² / g has a large dielectric loss and No 5 of more than 2.8 m ² / g. Has a large rate of change in dielectric constant with temperature. The amount of niobium pentoxide added to barium titanate is 0.8w.
No6 with less than t% has poor sinterability, and No10 with more than 2.0 wt% has a low dielectric constant. Furthermore, No15 having a weight ratio of nickel oxide + strontium oxide to niobium pentoxide smaller than 3 has a large temperature change rate of the dielectric constant, and No10 having a weight ratio larger than 8 has a low dielectric constant.
No. 11 has poor sinterability. From this result, a powder material in which the specific surface area of barium titanate was controlled to a size of 0.8 to 2.8 m ² / g was used, and niobium pentoxide was added to a powder material of 0.8 to
2.0 wt%, and by adding nickel oxide and strontium oxide at a weight ratio of 3 to 8 with respect to niobium pentoxide, the dielectric constant is 2800 or more and the dielectric loss is 2.5.
It can be seen that a dielectric ceramic composition having a dielectric strength temperature characteristic of not more than%, a withstand voltage of not less than 12 kV / mm, and excellent dielectric constant temperature characteristics can be obtained.

No. 16 premixed with only the additive
In comparison with No. 3, sinterability, dielectric loss, withstand voltage, and dielectric constant temperature characteristics are further improved. From this result, niobium pentoxide was mixed with a predetermined amount of trace amounts of nickel oxide and strontium oxide in advance, and then pulverized, and then mixed with barium titanate adjusted to a fine powder, whereby the trace additive titanium was the main component. It can be seen that this is an effective means for improving the characteristics by being uniformly dispersed in barium acid.

(Embodiment 2) This embodiment corresponds to the invention described in claim 3, is a composition in which silicon dioxide is further added to the composition of claim 1, and is based on the No. 3 composition of embodiment 1. It is a form.

First, niobium pentoxide, nickel oxide, strontium oxide, and silicon dioxide were weighed to the above barium titanate so as to have the respective compositions (Table 3).
A sample was prepared by the same procedure as in (Embodiment 1) and evaluated.

[0025]

[Table 3]

In Table 3 as well, niobium pentoxide was used as N.
b, nickel oxide is Ni, strontium oxide is Sr,
Silicon dioxide was designated as Si.

The evaluation results of the prepared sample are shown in (Table 4).

[0028]

[Table 4]

In (Table 4), the dielectric constant and the dielectric loss are those of the sintered body at a temperature of 1330 ° C.

As shown in (Table 4), the specific surface area of 1.2
barium titanate adjusted to m ² / g, niobium pentoxide,
By adding silicon dioxide to the No. 3 composition containing nickel oxide and strontium oxide (Embodiment 1), the sintering density becomes 6 g / cm ³ or more even at a low firing temperature of 1300 to 1330 ° C. You can see that it has been improved. However, No21 having an addition amount of more than 0.3 wt% has an effect of improving the sinterability, but the dielectric constant is remarkably decreased, while No17 having an addition amount of less than 0.05 wt% does not show the effect of improving the sinterability. It was excluded from the claims because of its poor withstand voltage characteristics and dielectric loss.

(Embodiment 3) This embodiment corresponds to the invention described in claim 3, and is a composition obtained by further adding lanthanum oxide or cerium oxide to the composition of claim 1, and No. 3 of (embodiment 1). It is a composition-based embodiment.
In this embodiment, barium titanate whose specific surface area was adjusted to 1.2 m ² / g was used as in (Embodiment 2).

The barium titanate was added with niobium pentoxide, nickel oxide, and strontium oxide, and then lanthanum oxide and cerium oxide were weighed so as to have the respective compositions (Table 5). Samples were prepared by the same procedure as the above) and evaluated.

[0033]

[Table 5]

In Table 5 as well, niobium pentoxide was used as N.
b, nickel oxide is Ni, strontium oxide is Sr,
The lanthanum oxide was represented by La and the cerium oxide was represented by Ce.

The evaluation results of the prepared sample are shown in (Table 6).

[0036]

[Table 6]

In (Table 6), the dielectric constant and the dielectric loss are those of the sintered body at a temperature of 1330 ° C.

As shown in (Table 6), the specific surface area of 1.2
barium titanate adjusted to m ² / g, niobium pentoxide,
By adding lanthanum oxide or cerium oxide to the No3 composition of nickel oxide and strontium oxide (Embodiment 1), 1300 to 1330 ° C.
It can be seen that the sintering density is 5.9 g / cm ³ or more and the sinterability is improved even when firing is low. However, in both cases of lanthanum oxide and cerium oxide, No26 and No31 with the addition amount exceeding 0.4 wt% have the effect of improving the sinterability, but the decrease in the dielectric constant becomes remarkable, while the amount of 0.05 wt. No2 less than%
Nos. 2 and No. 27 did not show the effect of improving the sinterability and were inferior in withstand voltage characteristics and dielectric loss, so were excluded from the claims.

(Embodiment 4) This embodiment corresponds to the invention described in claim 4 and is a composition obtained by adding any one of neodymium oxide, samarium oxide and dysprosium oxide to the composition of claim 1. (Embodiment 1) based on No. 3 composition. Further, in this embodiment, the specific surface area is 1.2 m ² / g as in the case of (Embodiment 2).
Barium titanate adjusted to was used. Niobium pentoxide, nickel oxide, and strontium oxide were added to barium titanate, and neodymium oxide, samarium oxide, and dysprosium oxide were weighed so as to have the respective compositions (Table 7) (Embodiment 1). A sample was prepared by the same procedure as above and evaluated.

[0040]

[Table 7]

In Table 7 as well, niobium pentoxide was used as N.
b, nickel oxide is Ni, strontium oxide is Sr,
Neodymium oxide was represented as Nd, samarium oxide as Sm, and dysprosium oxide as Dy.

The evaluation results of the prepared sample are shown in (Table 8).

[0043]

[Table 8]

In Table 8, the dielectric constant and the dielectric loss are those of the sintered body at a temperature of 1330 ° C.

As shown in (Table 8), the specific surface area of 1.2
barium titanate adjusted to m ² / g, niobium pentoxide,
By adding neodymium oxide, samarium oxide, or dysprosium oxide to the No3 composition of nickel oxide and strontium oxide (Embodiment 1), the sintered density is 5.8 g even at low firing of 1300 to 1330 ° C. / Cm ³ or more, indicating that the sinterability is improved. However, the addition amount of neodymium oxide, samarium oxide, or dysprosium oxide was all 0.
No. 36, No. 41, and No. 46, which exceed 5 wt%, have the effect of improving the sinterability, but the decrease in the dielectric constant becomes remarkable, while No. 3 less than 0.05 wt%.
Nos. 2, No. 37, and No. 42 did not show the effect of improving the sinterability and were poor in withstand voltage characteristics and dielectric loss, so were excluded from the claims.

(Embodiment 5) This embodiment corresponds to the invention described in claim 5, and is a composition obtained by further adding ytterbium oxide or praseodymium oxide to the composition of claim 1, and No. 3 of (embodiment 1). It is a composition-based embodiment. In this embodiment, barium titanate whose specific surface area was adjusted to 1.2 m ² / g was used as in (Embodiment 2). Niobium pentoxide, nickel oxide, and strontium oxide were added to barium titanate, and then ytterbium oxide or praseodymium oxide was weighed so as to have the composition shown in Table 9, and then the same as (Embodiment 1). A sample was prepared by the procedure of 1. and evaluated.

[0047]

[Table 9]

In Table 9 as well, niobium pentoxide is added to N
b, nickel oxide is Ni, strontium oxide is Sr,
Yt is yttrium oxide and praseodymium oxide is Pr
Was expressed.

The evaluation results of the prepared sample are shown in (Table 10).

[0050]

[Table 10]

Further, in (Table 10), the dielectric constant and the dielectric loss are those of the sintered body at a temperature of 1330 ° C.

As shown in (Table 10), the specific surface area of 1.
In contrast to the No3 composition of niobium pentoxide, nickel oxide, and strontium oxide added to barium titanate adjusted to ² m ² / g (comparative embodiment 1), yttrium oxide,
Or by adding praseodymium oxide,
It can be seen that with low firing of 00 to 1330 ° C., the sintering density becomes 5.8 g / cm ³ or more and the sinterability is improved in any addition. However, ytterbium oxide,
Alternatively, No51 and No56 in which the amount of praseodymium oxide added exceeds 0.7 wt% have an effect of improving the sinterability, but the dielectric constant is significantly decreased, while No47 and No52 having less than 0.05 wt% are burned. It was excluded from the claims because the effect of improving the binding property does not appear and the withstand voltage characteristics and the dielectric loss are poor.

As described above, from (Embodiment 1) to (Embodiment 5)
From the results of the above, the composition in which a specific amount of niobium pentoxide, nickel oxide, and strontium oxide was added to barium titanate whose specific surface area was adjusted to 0.8 to 2.8 m ² / g had excellent sinterability and high dielectric constant. In addition to high dielectric constant, low dielectric loss, flat temperature characteristics of dielectric constant, high dielectric strength ceramic composition. Further, by adding silicon dioxide, lanthanum oxide, cerium oxide, neodymium oxide, samarium oxide, dysprosium oxide, ytterbium oxide, praseodymium oxide to the above composition base, a dielectric ceramic with high withstand voltage and more excellent in sinterability. It will be appreciated that the composition may be provided.

[0054]

As described above, according to the present invention, excellent sinterability,
It is possible to manufacture an excellent dielectric ceramic composition having a dielectric constant of 2800 or more and a dielectric loss of 2.0% or less and having a flat dielectric constant temperature characteristic and a withstand voltage of 13 kV / mm. Therefore, in a monolithic ceramic capacitor that requires thinning and high lamination, it is possible to reduce the thickness of the dielectric layer, and to provide an industrially effective composition that can easily realize miniaturization and large capacitance. Is possible.

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Claims (6)

(57) [Claims] 1. A dielectric ceramic composition containing barium titanate as a main component whose specific surface area is adjusted to 0.8 to 2.8 m ² / g and containing at least niobium pentoxide, nickel oxide, and strontium oxide as auxiliary components. Of the barium titanate, the niobium pentoxide is 0.8 to
2.0 wt% of the nickel oxide and the strontium oxide in a weight ratio to the niobium pentoxide of 3 ≦ niobium pentoxide / (nickel oxide + strontium oxide) ≦ 8
(However, nickel oxide and strontium oxide are 0
(Except when wt%) The dielectric ceramic composition. 2. The dielectric ceramic composition according to claim 1, further comprising 0.05 to 0.30 wt% of silicon dioxide with respect to barium titanate. 3. A lanthanum oxide or a cerium oxide is added to barium titanate in an amount of 0.05 to 0.05.
The dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition contains 0.40 wt%. 4. A barium titanate containing 0.05 to 0.50 wt% of any one selected from neodymium oxide, samarium oxide, and dysprosium oxide.
%, The dielectric ceramic composition according to claim 1. 5. The dielectric ceramic composition according to claim 1, wherein the barium titanate further contains 0.05 to 0.70 wt% of any one of ytterbium oxide and praseodymium oxide. object. 6. A weight ratio of nickel oxide and strontium oxide to niobium pentoxide is 3 ≦ niobium pentoxide /
(Nickel oxide + strontium oxide) ≤ 8 (however,
The composition of nickel oxide and strontium oxide (excluding when it is 0 wt%) is mixed and pulverized in advance, and the specific surface area is adjusted to 0.8 to 2.8 m ² / g. Is added in an amount of 0.8 to 2.0 wt%.