JPH08129910A - Dielectric porcelain composition - Google Patents

Abstract

(57) [Abstract] [Purpose] A dielectric constant of 2500 or more and a firing temperature of 130
Dielectric porcelain having a temperature change rate of 0 ° C. or less, a temperature change rate of capacitance satisfying X7R of EIA standard, a dielectric loss of 2.5% or less, a small voltage dependency, and an insulation resistance of 10 ⁴ MΩ or more. A composition is provided. [Structure] 100 parts by weight of BaTiO ₃ and Nb ₂ O
₅ to 0.8 to 2.5 parts by weight, MgO to 0.06 to 0.7
0 parts by weight, Nd ₂ O ₃ is 0.005 to 0.520 parts by weight, and MnO is 0.01 to 0.30 in terms of MnCO _3.
In addition to containing by weight, the molar ratio of Nb ₂ O ₅ to MgO is in the range of 0.5 to 2.2.
SiO ₂ and Al ₂ O based on 100 parts by weight of iO _3.
0.05 to 0.50 parts by weight of at least one of ₃ ,
It is desirable to contain ZnO in an amount of 0.5 parts by weight or less.

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 containing BaTiO ₃ as a main component and Nb ₂ O ₅ , MgO, Nd ₂ O ₃ and MnO.

[0002]

2. Description of the Related Art Conventionally, dielectric ceramic compositions have been used as materials for laminated ceramic capacitors and the like. Such a monolithic ceramic capacitor is constructed by laminating a plurality of green sheets of a dielectric ceramic composition having internal electrodes so as to have a predetermined capacity, and then integrally firing them. For example, X7R (EIA standard: temperature characteristic of capacitance is -55
The dielectric ceramic composition used for the laminated ceramic capacitor of +/- 15 ° C at + 25 ° C
It is important that the relative dielectric constant is as high as 2500 or more, the thickness of each green sheet is 15 μm or less, and the firing temperature is 1300 ° C. or less.

That is, the relative dielectric constant at 25 ° C. is 2500
As described above, by setting the thickness of the green sheet to 15 μm or less, the thickness of the green sheet between the internal electrodes and the facing area can be minimized, and the multilayer ceramic capacitor can be downsized. Further, by setting the firing temperature to 1300 ° C. or lower, the selection range of the material of the internal electrodes is increased, and for example,
It is possible to use inexpensive Pd-Ag from expensive 100% Pd material. In addition to the above, the dielectric loss tan δ and the insulation resistance, which are various characteristics of the dielectric ceramic composition, must be fully taken into consideration, and it is further desired that the dielectric loss has a small AC voltage dependency.

Conventionally, as a device having an improved relative dielectric constant,
A dielectric ceramic composition containing BaTiO ₃ , Nb ₂ O ₅ , and ZnO has already been proposed (Japanese Patent Laid-Open No. 59-18162).
JP, JP-A-59-18159, etc.). Such a dielectric ceramic composition has a relative dielectric constant of 2000.
Can be up to 3000. However, even though the above-mentioned dielectric ceramic composition can obtain a high relative permittivity, the dielectric loss tan δ is large, so that the green sheet cannot be thinned, and when used in a multilayer capacitor, a high relative dielectric constant is eventually obtained. Dielectric constant could not be obtained.

As a system developed to reduce the dielectric loss tan δ in this way, BaTiO ₃ , Nb is used.
A dielectric ceramic composition containing ₂ O ₅ , MgO, and La ₂ O ₃ has already been proposed (see Japanese Patent Publication No. 5-10766). In addition, Nb ₂ O ₅ and MgO are mixed so that the molar ratio of Nb ₂ O ₅ / MgO to BaTiO ₃ is in the range of 2.3 to 4.
And a composition in which 0.1 to 0.5% by weight of an oxide of a rare earth element is added thereto is disclosed (JP-B-55-1).
9007).

[0006]

However, none of the above-mentioned dielectric ceramics has a small relative permittivity of about 2200 or less and cannot cope with a reduction in size and capacity. Further, there is a problem that the dielectric loss is still large and it is difficult to make the green sheet thin.

Furthermore, in any of the above-mentioned dielectric ceramics, it is considered that the AC loss dependency of the dielectric loss becomes large and it becomes impossible to cope with the thinning of the dielectric material.
In this case, there is a problem that it is not possible to cope with the miniaturization and the large capacity of the capacitor.

[0008]

[Means for Solving the Problems] As a result of intensive studies made by the present inventors in view of the above problems, barium titanate BaT
iO ₃ as a main component, Nb ₂ O ₅ , MgO, Nd
Nb containing ₂ O ₃ and MnO in a predetermined composition ratio.
By setting the molar ratio of ₂ O ₅ to MgO to 0.5 to 2.2, the relative dielectric constant is 2500 or more, the temperature change rate of the capacitance satisfies X7R of EIA standard, and the dielectric loss is 2.5. The present invention has found that a dielectric porcelain having a small thickness of 10% or less, a dielectric loss of 3.0% or less even when an AC voltage of 2000 V / cm is applied and a small AC voltage dependency, and a thin layer can be obtained. Came to.

That is, the dielectric ceramic of the present invention is made of BaTiO 3.
₃ Nb ₂ O ₅ 0.8 to 2.5 with respect to 100 parts by weight
Parts by weight, MgO 0.06 to 0.70 parts by weight, Nd ₂ O
0.005 to 0.520 parts by weight of ₃ and MnO to MnCO
_{It is} contained in an amount of 0.01 to 0.30 parts by weight in terms of ₃ , and the molar ratio of Nb ₂ O ₅ to MgO is 0.5 to 2.
It is 2. Also, with respect to 100 parts by weight of BaTiO ₃ ,
0.05 at least one of SiO ₂ and Al ₂ O ₃
˜0.50 parts by weight is desirable, and ZnO
It is desirable to contain 0.5 part by weight or less.

In the present invention, Nb ₂ O ₅ is contained in an amount of 0.8 to 2.5 parts by weight with respect to 100 parts by weight of BaTiO _{3 because the} content of less than 0.8 parts by weight deteriorates the dielectric loss.
This is because the temperature characteristics and sinterability are poor, and when the amount exceeds 2.5 parts by weight, the relative dielectric constant decreases and the temperature characteristics deteriorate significantly. Nb ₂ O ₅ is preferably contained in an amount of 1.3 to 2.0 parts by weight based on 100 parts by weight of BaTiO ₃ .

Further, MgO is set to 0.06 to 0.70 parts by weight because when it is less than 0.06 parts by weight, the relative dielectric constant and the insulation resistance are lowered, the temperature characteristics are deteriorated, grain growth is caused, and the voltage of dielectric loss. This is because the dependency becomes large. Also, 0.7
This is because if the amount is more than 0 parts by weight, the dielectric constant decreases and the insulation resistance also decreases. MgO is preferably 0.1 to 0.4 part by weight.

Further, Nd ₂ O ₃ is added in an amount of 0.005 to 0.5.
The content of 20 parts by weight means that when Nd ₂ O ₃ is less than 0.005 parts by weight, the relative dielectric constant is lowered and the sinterability is deteriorated.
This is because if the amount exceeds 0 parts by weight, the temperature characteristics deteriorate. N
It is desirable that d ₂ O ₃ is 0.005 to 0.2 part by weight.

Further, MnO is converted to MnCO ₃ in an amount of 0.01 to
The amount of 0.30 parts by weight is less than 0.01 parts by weight, the insulation resistance decreases, the dielectric loss and the sinterability deteriorate, and
This is because if the amount exceeds 0 parts by weight, the relative dielectric constant decreases. MnO is preferably 0.04 to 0.10 parts by weight in terms of MnCO ₃ .

The molar ratio of Nb ₂ O ₅ to MgO is set to 0.5 to 2.2. When the molar ratio is smaller than 0.5, the relative dielectric constant is deteriorated and the temperature characteristics and sinterability are improved. If it is worse than 2.2, the temperature characteristics are poor and the relative dielectric constant is lowered. In the present invention, the molar ratio of Nb ₂ O ₅ to MgO is particularly preferably set to 0.6 to 1.4.

Further, 0.05 to 0.50 parts by weight of at least one of SiO ₂ and Al ₂ O ₃ is contained in 100 parts by weight of BaTiO ₃ when the amount is less than 0.05 parts by weight. This is because the effect of improving the relative dielectric constant, the effect of improving the sinterability, and the effect of improving the voltage dependence are scarcely present, and when it is more than 0.50 parts by weight, the relative dielectric constant tends to decrease. At least one of SiO ₂ and Al ₂ O ₃ is preferably contained in an amount of 0.1 to 0.2 parts by weight with respect to 100 parts by weight of BaTiO ₃ .

Further, 0.5 parts by weight or less of ZnO is contained with respect to 100 parts by weight of BaTiO ₃ because ZnO is more than 0.5 parts by weight, the temperature characteristics are poor and the dielectric loss tends to increase. Because it is in. ZnO is BaT
It is desirable to contain 0.3 parts by weight or less with respect to 100 parts by weight of iO ₃ .

The BaTiO ₃ used in the present invention is, for example, an average crystal grain size of 1.0 μm produced by any one of the solid phase method, sol-gel method, oxalic acid method, hydrothermal synthesis method and the like.
Based on the following BaTiO ₃ powder as a main component, this BaTi
Nb ₂ O ₅ , MgO, Nd with respect to 100 parts by weight of O _3.
A predetermined amount of each of ₂ O ₃ , MnCO ₃ , SiO ₂ , Al ₂ O ₃ , and ZnO powder was weighed, wet-milled for 20 to 48 hours with a ball mill or the like, dried, and then a predetermined amount of a binder was added to obtain a predetermined amount. Shaped into a shape, 1230 ℃ ~ 1 in air
It is produced by firing at 300 ° C. for 1 to 2 hours.
In the case of producing a monolithic ceramic capacitor, the above powder is slurried and formed into a sheet by the doctor blade method, and the sheet-shaped compact is appropriately made of Ag.
It suffices to apply an internal electrode such as -Pd, stack a plurality of these electrodes, and simultaneously fire them under the above firing conditions.

Nb ₂ O ₅ , MgO, used in the present invention
Nd ₂ O ₃ , MnCO ₃ , SiO ₂ , Al ₂ O ₃ , Zn
Instead of O powders, Nb, Mg, Nd, Mn, Si,
Al, Zn hydroxides, carbonates, nitrates, oxalates,
It is also possible to use an alkoxide or the like that decomposes at a temperature not higher than the sintering temperature to become an oxide.

In order to improve the AC voltage dependency, it is preferable to control the average crystal grain size d of the sintered body to d <1.0 μm. Thus, the average crystal grain size d of the sintered body is d <
To control to 1.0 μm, use barium titanate powder having an average crystal grain size of 1.0 μm or less as a starting material,
It is necessary to carry out wet pulverization for a long time to control the particle size after pulverization to 0.8 μm or less, or to set the firing temperature as low as possible to shorten the firing time.

[0020]

In the dielectric ceramic composition of the present invention, the temperature characteristic of capacitance is within ± 15% in the range of -55 ° C to 125 ° C, the relative dielectric constant at + 25 ° C is 2500 or more, and the thickness of the green sheet is Is 15 μm, the dielectric loss is as small as 2.5% or less, and the AC voltage is 2000 V / cm.
The dielectric loss in 3 can be as small as 3% or less. Therefore, a small-sized and large-capacity multilayer capacitor can be obtained. Moreover, since the firing temperature is 1300 ° C. or less, it is easy to manufacture industrially, and inexpensive silver-palladium (Ag / Pd = 20/80 to 40/6) is used for the internal electrodes.
A dielectric porcelain that can be used for a multilayer capacitor using 0) is achieved. Furthermore, the dielectric loss, which is a basic characteristic of dielectric ceramics, is 2.5% or less, and the insulation resistance (IR)
Of 10 ⁴ MΩ or more, which is a satisfactory dielectric ceramic.

[0021]

EXAMPLES Examples of the present invention will be described in detail below.

Average particle size produced by the oxalic acid method
Based on BaTiO ₃ powder of 0 μm or less as the main component,
100 parts by weight of aTiO ₃ , Nb ₂ O ₅ , Mg
O, Nd ₂ O ₃ , MnCO ₃ , SiO ₂ , Al ₂ O ₃ ,
Each powder of ZnO was weighed as shown in Table 1, wet-milled for 20 to 48 hours in a ball mill, and then an organic binder was added thereto, followed by stirring and a doctor blade method to obtain a thickness of 15 μm.
m was formed into a tape shape. This tape is 130mm x 1
It is cut into 00 mm and 20 sheets are piled up to produce a laminated body.

[0023]

[Table 1]

As the internal electrodes, Ag-Pd paste (Ag / Pd = 30/70) was printed. This laminated body was cut into 3.2 mm × 1.6 mm, and was cut in air to 124 mm.
It was baked at 0 to 1320 ° C. for 2 hours. Further, electrodes made of silver paste were baked on both end faces at 800 ° C. for 10 minutes to prepare a measurement sample.

The capacitance and the dielectric loss of the sample thus formed were measured at a reference temperature of 25 ° C. and a frequency of 1.0 k.
It was measured at Hz and a measurement voltage of 1.0 Vrms. The temperature change rate of the capacity is measured in the range of −55 to + 125 ° C.,
The capacity at + 25 ° C was used as a standard. Furthermore, the insulation resistance was measured by applying a DC voltage of 25 V for 1 minute. The relative permittivity was calculated back from the capacitance.

The average crystal grain size of the sintered porcelain was calculated by observing the surface of the porcelain at 15,000 times with a scanning electron microscope and measuring 500 or more grains by the line intercept method. Furthermore, 2000 Vrms / cm at a frequency of 1 kHz
The dielectric loss was measured when the voltage was applied. Table 2 shows the above results.

[0027]

[Table 2]

Any of the dielectric ceramics within the scope of the present invention has a large relative permittivity of 2500 or more, and moreover, it has an EIA standard of X.
7R characteristics (capacity change rate within ± 15% in the temperature range of −55 ° C. to 125 ° C.) are satisfied. Furthermore, the dielectric loss tan
δ is as small as 2.5% or less, AC voltage 2000 Vrms
A loss of 3.0% or less is shown even under / cm. Further, the insulation resistance (IR) is 10 ⁴ MΩ or more.

In Table 1, sample numbers 1 to 5 are Nb ₂ added to BaTiO ₃ which is the main component of the dielectric ceramic composition.
The amount of O ₅ added was varied from 0.6 to 3.0 parts by weight. At this time, MgO, Nd ₂ O ₃ , and MnCO ₃
Were added to 0.2 parts by weight, 0.2 parts by weight, and 0.1 parts by weight.

Sample No. 1 (Nb ₂ O ₅ addition amount: 0.6
In parts by weight), the relative dielectric constant εr is 3330, which is a good product, but the dielectric loss tan δ is 3.2%. Further, the temperature characteristic becomes -26%. Further, in the sample numbers 2 to 4 (addition amount of Nb ₂ O ₅ : 0.8 to 2.5% by weight), the relative permittivity εr becomes 2570 to 3500,
Dielectric loss tan δ is 2.5% or less, and temperature characteristics are ±
It is within 14%, tan δ is 3.0% or less when an AC voltage of 2000 V / cm is applied, and the insulation resistance (IR) is also 5 to 9.
The range is × 10 ⁴ MΩ, which is a good product. That is, the relative permittivity εr
High, excellent temperature characteristics, small dielectric loss tan δ,
Further, a dielectric ceramic having a small dielectric loss AC voltage dependency is achieved. Further, Sample No. 5 (addition amount of Nb ₂ O ₅ :
At 3.0 parts by weight), the relative dielectric constant ε is 2050, and the temperature characteristics deteriorate. Therefore, in the present invention, the weight of Nb ₂ O ₅ added to barium titanate BaTiO ₃ is in the range of 0.8 to 2.5 parts by weight with respect to 100 parts by weight of barium titanate BaTiO ₃ .

In Sample Nos. 6 to 10, the amount of MgO added to BaTiO ₃ which is the main component of the dielectric ceramic composition was changed to 0.04 to 0.75 parts by weight. At this time, the addition amounts of Nb ₂ O ₅ , Nd ₂ O ₃ , and MnCO ₃ are 2.3 to 2.5 parts by weight, 0.2 parts by weight, and
It was set to 0.1 parts by weight.

Sample No. 6 (amount of MgO added: 0.04 parts by weight) had a tan when an AC voltage of 2000 V / cm was applied.
δ becomes 4.0%. In addition, sample numbers 7 to 9
(In the addition amount of MgO: 0.06 to 0.70 parts by weight),
The relative permittivity εr becomes 2580 to 2950, and the dielectric loss t
an σ is 2.0% or less, temperature characteristics are within ± 13%, tan σ is 2.6% or less when an AC voltage of 2000 V / cm is applied, and insulation resistance (IR) is also 3 to 8 × 10 ⁴ M
Ω and good product range. That is, a dielectric ceramic having a high relative permittivity εr, excellent temperature characteristics, a small dielectric loss tan δ, and a small AC voltage dependency of the dielectric loss can be achieved. Further, in the sample No. 10 (amount of MgO added: 0.75 parts by weight), the dielectric loss tan δ is 1.7%, which is in the range of good products, but the relative dielectric constant εr is 2100. Therefore, in the present invention, barium titanate BaT
The weight of MgO added to iO ₃ is barium titanate Ba.
The range was 0.06 to 0.70 parts by weight with respect to 100 parts by weight of TiO ₃ . Sample Nos. 11 to 15 are Nd ₂ O ₃ added to BaTiO ₃ which is the main component of the dielectric ceramic composition.
The value was changed from 0 to 0.53 parts by weight. At this time, the amounts of Nb ₂ O ₅ , MgO and MnCO ₃ added were 1.8 parts by weight, 0.3 parts by weight and 0.1 parts by weight, respectively.

Sample No. 11 (Nd ₂ O ₃ addition amount: 0)
Then, although the dielectric loss tan δ becomes 2.5%, the relative dielectric constant εr becomes as low as 2350. In addition, sample numbers 12 to 14 (amount of Nd ₂ O ₃ added: 0.005 to 0.
52 parts by weight) has a relative permittivity εr of 2660 to 3420.
The dielectric loss tan δ is 2.0% or less, the temperature characteristic is within ± 11%, and the AC voltage is 2000 V / cm.
When tan δ when applied is 2.8% or less, insulation resistance (IR)
Is in the range of 3 to 7 × 10 ⁴ MΩ, which is a good product. That is, a dielectric ceramic having a high relative permittivity εr, excellent temperature characteristics, a small dielectric loss tan σ, and a small AC voltage dependency of the dielectric loss is achieved. Furthermore, sample number 15 (Nd ₂ O ₃
Of 0.55 parts by weight), the relative dielectric constant εr is 36
30, the dielectric loss tan δ was 1.8%, which was in the range of good products, but the temperature characteristics deteriorate. Therefore, in the present invention, Nd added to barium titanate BaTiO ₃ is used.
The weight of ₂ O ₃ was in the range of 0.005 to 0.52 parts by weight with respect to 100 parts by weight of barium titanate BaTiO ₃ .

In Sample Nos. 16 to 20, the addition amount of MnCO ₃ added to BaTiO ₃ which is the main component of the dielectric ceramic composition was changed to 0.005 to 0.35 parts by weight.

At this time, Nb ₂ O ₅ , MgO and Nd ₂ O
The addition amount of ₃ was 1.8 parts by weight, 0.3 parts by weight, and 0.2 parts by weight.

Sample No. 16 (Amount of MnCO ₃ added: 0.
005 parts by weight), the relative dielectric constant εr is 2850, but the dielectric loss tan δ is 2.6%. Furthermore, the insulation resistance becomes 9 × 10 ³ . In addition, sample number 17
.About.19 (addition amount of MnCO3: 0.01 to 0.3% by weight), the relative dielectric constant .epsilon.r becomes 2650 to 2860,
Dielectric loss tan δ is 2.2% or less, and temperature characteristics are ±
Within 6%, t when AC voltage 2000 V / cm is applied
An δ of 3.0% or less, insulation resistance (IR) of 3 × 10
^It is in the range of ⁴ to 1 × 10 ⁵ MΩ, which is a good product. That is, a dielectric ceramic having a high relative permittivity εr, excellent temperature characteristics, a small dielectric loss tan δ, and a small AC voltage dependency of the dielectric loss can be achieved. Further, in sample No. 20 (amount of MnCO ₃ added: 0.35 parts by weight), the dielectric loss tan δ was 1.4%, which was in the range of good products, but the relative dielectric constant εr was 2
It will be as low as 200. Therefore, in the present invention, the weight of MnCO ₃ added to barium titanate BaTiO ₃ is in the range of 0.01 to 0.3 parts by weight with respect to 100 parts by weight of barium titanate BaTiO ₃ .

Sample Nos. 21 to 29 are MgO of Nb ₂ O ₅
Was varied from 0.5 to 2.3. Ratio 0.4
In both cases, the relative permittivity is lower than 2310, 2030 and 2500, and the temperature characteristic is also deviated. On the other hand, the ratio is 0.5-
In the case of 2.2, the dielectric constant is 2500 or more and the temperature characteristics and other characteristics are also satisfied. Example 2 SiO ₂ , Al ₂ O ₃ , and ZnO powder were added to the composition of Sample No. 13 in Table 1 as shown in Table 3 and formed into a tape in the same manner as in Example 1, The tapes were laminated to form internal electrodes to prepare a laminated body. Then, each characteristic was measured in the same manner as in Example 1 and is shown in Table 4.

The composition of the sample was as follows: 1.8 parts by weight of Nb ₂ O ₅ , 0.3 parts by weight of MgO, 0.2 parts by weight of Nd ₂ O ₃ , and MnO based on 100 parts by weight of BaTiO _3. Mn
Containing 0.1 parts by weight in terms of CO ₃ , SiO ₂ , Al ₂ O
₃ , ZnO is contained in a predetermined amount with respect to 100 parts by weight of BaTiO ₃ .

[0039]

[Table 3]

[0040]

[Table 4]

From these Tables 3 and 4, SiO ₂ , Al ₂
It can be seen that the inclusion of O ₃ and ZnO results in a lower firing temperature and a higher relative dielectric constant than in the case where these compounds are not included (Sample No. 13).

[0042]

As described above, according to the present invention, X7R
The characteristics are satisfied, the relative dielectric constant εr is 2500 or more, and the firing temperature is 1300 ° C. or less. As other characteristics, the dielectric loss tan δ is 2.5% or less, the insulation resistance (I
It is possible to obtain a dielectric ceramic composition in which R) is 10 ⁴ MΩ or more and tan δ is 3% or less when an AC voltage of 2000 V / cm is applied.

Thus, for example, when a monolithic ceramic capacitor is composed of the above-mentioned dielectric ceramic composition, a compact and large-capacity capacitor having excellent temperature characteristics can be obtained, and the firing temperature becomes 1300 ° C. or less, and the capacitors are laminated. It is also possible to use inexpensive silver-palladium as an internal electrode between the sheets, and an inexpensive monolithic ceramic capacitor can be obtained.

Claims (3)

[Claims] 1. Nb based on 100 parts by weight of BaTiO _3.
0.8 to 2.5 parts by weight of ₂ O ₅ and 0.06 to MgO
0.70 parts by weight, 0.005 to 0.520 of Nd ₂ O ₃
0.01 to 0 in terms parts by weight of MnO to MnCO _3.
A dielectric ceramic composition comprising 30 parts by weight and having a molar ratio of Nb ₂ O ₅ to MgO within a range of 0.5 to 2.2. 2. The dielectric according to claim 1, further comprising 0.05 to 0.50 parts by weight of at least one of SiO ₂ and Al ₂ O ₃ with respect to 100 parts by weight of BaTiO _3. Porcelain composition. _3. Zn based on 100 parts by weight of BaTiO ₃
The dielectric porcelain composition according to claim 1 or 2, wherein O is contained in an amount of 0.5 part by weight or less.