JP2902925B2 - Dielectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention, a BaTiO ₃ as a main component, to a Nb ₂ O _5, MgO, the dielectric ceramic composition containing La ₂ O _3, MnO.

[0002]

2. Description of the Related Art Hitherto, dielectric ceramic compositions have been used as materials for multilayer ceramic capacitors and the like. Such a multilayer ceramic capacitor is formed by laminating a plurality of raw sheets of the dielectric ceramic composition on which internal electrodes are formed so as to have a predetermined capacity, and then firing them integrally. For example, X7R (EIA standard: temperature characteristic of capacitance is -55
(± 15% at 125 ° C. to 125 ° C.), the dielectric ceramic composition used at + 25 ° C.
It is important that the relative dielectric constant is as high as 2500 or more, the thickness of a raw sheet per sheet is 15 μm or less, and the firing temperature is, for example, 1300 ° C. or less.

That is, the relative dielectric constant at 25 ° C. is 2500
As described above, by setting the thickness of the raw sheet to 15 μm or less, the thickness and the facing area of the raw sheet between the internal electrodes can be minimized, and the miniaturization of the multilayer ceramic capacitor can be achieved. Further, by setting the firing temperature to 1300 ° C. or lower, the selection range of the material of the internal electrode increases, and for example,
Inexpensive Pd-Ag can be used from expensive Pd 100% 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 sufficiently considered, and it is desired that the AC loss has a small AC voltage dependence.

Conventionally, as a material having an improved relative dielectric constant,
A dielectric porcelain composition containing BaTiO ₃ , Nb ₂ O ₅ , and ZnO has already been proposed (JP-A-59-18162).
And JP-A-59-18159). According to such a dielectric porcelain composition, the relative dielectric constant is 2000
３3000. However, even though the above-mentioned dielectric porcelain composition can obtain a high relative dielectric constant, the dielectric loss tan δ is large, so that the raw sheet cannot be thinned. Dielectric constant was not obtained.

As a system developed to reduce the dielectric loss tan δ, BaTiO ₃ , Nb
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). Further, 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 a rare earth is added in an amount of 0.1 to 0.5% by weight is disclosed (see Japanese Patent Publication No. 55-19007).

[0006]

However, none of the above-mentioned dielectric ceramics has a relative dielectric constant as small as about 2200 or less, and cannot cope with an increase in size and capacity. There is also a problem that the dielectric loss is still large and it is difficult to make the raw sheet thin.

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

[0008]

The present inventors have made intensive studies in view of the above problems and found that barium titanate BaT
iO ₃ as a main component, Nb ₂ O ₅ , MgO, La
It contains ₂ O ₃ and MnO at a predetermined composition ratio, and
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 the EIA standard, and the dielectric loss is 2.5. % Or less, and a dielectric loss of 3.0% or less even when an AC voltage of 2000 V / cm is applied, which has a small AC voltage dependency and can be obtained as a thin dielectric ceramic. Reached.

That is, the dielectric ceramic composition of the present invention comprises Ba
0.8 parts of Nb ₂ O ₅ is added to 100 parts by weight of TiO _3.
~ 2.5 parts by weight, 0.06-0.70 parts by weight of MgO,
0.005 to 0.520 parts by weight La ₂ O _3, 0.01~0.30 parts by weight in terms of MnO in MnCO _3, Si
At least one of O ₂ and Al ₂ O ₃ is 0.05
０．５0.50 parts by weight and Nb ₂ O ₅ Mg
The molar ratio to O is in the range of 0.5 to 2.2. Here, it is desirable that ZnO be contained in an amount of 0.1 part by weight or less based on 100 parts by weight of BaTiO ₃ .

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 .
This is because the temperature characteristics and the sinterability are poor, and if it exceeds 2.5 parts by weight, the relative dielectric constant decreases, and the temperature characteristics deteriorate significantly. Nb ₂ O ₅ is desirably contained in an amount of 1.3 to 2.0 parts by weight based on 100 parts by weight of BaTiO ₃ .

The reason why the MgO content is set to 0.06 to 0.70 parts by weight is that when the content is less than 0.06 parts by weight, the relative dielectric constant and the insulation resistance are reduced, the temperature characteristics are deteriorated, the grains grow, and the voltage of the dielectric loss is reduced. This is because the dependency becomes large. Also, 0.7
If the amount is more than 0 parts by weight, the dielectric constant decreases and the insulation resistance also decreases. MgO is desirably 0.1 to 0.4 parts by weight.

Further, La ₂ O ₃ is added in an amount of 0.005 to 0.5.
The reason for setting the content to 20 parts by weight is that when La ₂ O ₃ is less than 0.005 parts by weight, the relative dielectric constant is lowered, the sinterability is poor, and
If the amount exceeds 0 parts by weight, the temperature characteristics deteriorate. L
a ₂ O ₃ is desirably 0.005 to 0.2 parts by weight.

MnO is converted to MnCO ₃ in an amount of 0.01 to
When it is less than 0.01 part by weight, the insulation resistance is reduced, the dielectric loss and the sinterability deteriorate, and
If the amount exceeds 0 parts by weight, the relative permittivity will decrease. MnO is desirably 0.04 to 0.10 parts by weight in terms of MnCO ₃ .

The reason why the molar ratio of Nb ₂ O ₅ to MgO is set to 0.5 to 2.2 is that when the molar ratio is smaller than 0.5, the relative dielectric constant is deteriorated, and the temperature characteristics and sinterability are deteriorated. This is because if it is not good, and if it is larger than 2.2, the temperature characteristic is bad and the relative dielectric constant is lowered. In the present invention, the molar ratio of MgO Nb ₂ O _5, particularly, it is desirable that the 0.6 to 1.4.

[0015] Further, 0.05 to 0.50 parts by weight of at least one of SiO ₂ and Al ₂ O ₃ is contained per 100 parts by weight of BaTiO ₃ when less than 0.05 part by weight. This is because there is almost no effect of improving the relative dielectric constant, the effect of improving the sinterability, and the effect of improving the voltage dependency, and if 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 desirably contained in an amount of 0.1 to 0.2 parts by weight based on 100 parts by weight of BaTiO ₃ .

Further, the reason that ZnO is contained in an amount of 0.1 part by weight or less based on 100 parts by weight of BaTiO ₃ is that when ZnO is more than 0.1 part by weight, temperature characteristics are poor and dielectric loss tends to increase. Because it is in. ZnO is BaT
It is desirable to contain 0.05 parts by weight or less based on 100 parts by weight of iO ₃ .

BaTiO ₃ used in the present invention is, for example, a BaTiO ₃ powder having an average crystal grain size of 1.0 μm or less produced by any of a solid phase method, a sol-gel method, an oxalic acid method, and a hydrothermal synthesis method. With the main component being BaTiO
₃ Nb ₂ O ₅ , MgO, La ₂
A predetermined amount of each of O ₃ , MnCO ₃ , SiO ₂ , Al ₂ O ₃ , and ZnO powders is weighed, wet-pulverized in a ball mill or the like for 20 to 48 hours, dried, and then added with a predetermined amount of a binder to form a predetermined shape. And 1200 ° C to 13
It is manufactured by baking at 00 ° C. for 1 to 2 hours. When a multilayer ceramic capacitor is manufactured, the above powder is slurried, formed into a sheet by a doctor blade method, and the sheet-shaped formed body is appropriately Ag-
An internal electrode such as Pd is applied, and a plurality of these are laminated,
What is necessary is just to bake simultaneously under the said baking conditions.

The Nb ₂ O ₅ , MgO,
La ₂ O ₃ , MnCO ₃ , SiO ₂ , Al ₂ O ₃ , Zn
O Instead of each powder, Nb, Mg, La, Mn, Si,
Hydroxides, carbonates, nitrates, oxalates of Al and Zn,
An alkoxide or the like that decomposes below the sintering temperature to become an oxide can also be used.

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 set to d <
To control it to 1.0 μm, barium titanate powder having an average crystal grain size of 1.0 μm or less is used 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 and to shorten the firing time.

[0020]

According to the dielectric ceramic composition of the present invention, the temperature coefficient 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 increased. Is 15 μm, the dielectric loss is as small as 2.5% or less, and the AC voltage is 2000 V / cm.
Can be as small as 3% or less. For this reason, a small-sized and large-capacity multilayer capacitor can be obtained. Further, since the sintering temperature is 1300 ° C. or less, it is easy to produce industrially, and inexpensive silver-palladium (Ag / Pd = 20/80 to 40/6) is used for the internal electrode.
Thus, a dielectric porcelain which can be used for a multilayer capacitor using 0) is achieved. Furthermore, dielectric loss, which is a basic characteristic of dielectric porcelain, is 2.5% or less, insulation resistance (IR)
Is sufficiently higher than 10 ⁴ MΩ.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a reference example will be described.

Average particle size produced by hydrothermal synthesis
The main component is BaTiO ₃ powder of 0 μm or less.
Nb ₂ O ₅ , Mg with respect to 100 parts by weight of aTiO ₃
O, La ₂ O ₃ , MnCO ₃ , SiO ₂ , Al ₂ O ₃ ,
Each ZnO powder was weighed as shown in Table 1 and wet-pulverized by a ball mill for 20 to 48 hours, and then an organic binder was added. Then, the mixture was stirred and the thickness was 15 μm by a doctor blade method.
m. 130mm x 1
The sheet is cut into 00 mm, 20 sheets are stacked, and a laminate is prepared by hot pressing at 80 ° C.

[0023]

[Table 1]

Incidentally, an Ag-based paste (A
g / Pd = 30/70). This laminate was used for 3.
Cut to 2mm x 1.6mm, 1250-1 in air
It was baked at 320 ° C. for 2 hours. Furthermore, electrodes made of silver paste were baked on both end surfaces at 800 ° C. for 10 minutes to obtain measurement samples.

For the sample thus formed, the capacitance and dielectric loss were measured at a reference temperature of 25 ° C. and a frequency of 1.0 k.
Hz and a measurement voltage of 1.0 Vrms. The temperature change rate of the capacitance is measured in the range of -55 to + 125 ° C,
Based on the capacity at + 25 ° C. Further, the insulation resistance was measured when a DC voltage of 25 V was applied for one minute.

The relative permittivity was calculated backward from the capacitance.

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

[0028]

[Table 2]

Each of the dielectric ceramics within the scope of the present invention has a relative dielectric constant as large as 2500 or more, and furthermore, the EIA standard X
Satisfies 7R characteristics (capacity change within ± 15% in a temperature range of -55 ° C to 125 ° C). Further, the dielectric loss tan
δ is as small as 2.5% or less, AC voltage 2000Vrms
/ Cm shows a loss of 3.0% or less. Further, the insulation resistance (IR) has a value of 10 ⁴ MΩ or more.

In Table 1, Sample Nos. 1 to 5 are Nb ₂ added to BaTiO ₃ which is a main component of the dielectric ceramic composition.
The value of O ₅ was varied from 0.7 to 2.6 parts by weight. At this time, MgO, La ₂ O ₃ and MnCO ₃
Was added to 0.2 parts by weight, 0.2 parts by weight, and 0.1 parts by weight.

Sample No. 1 (the amount of Nb ₂ O ₅ added: 0.7
(Parts by weight), the dielectric constant ε is 3500, which is a good product, but the dielectric loss tanσ is 3.3%. Further, the temperature characteristic becomes -27%. In sample numbers 2 to 4 (addition amount of Nb ₂ O ₅ : 0.8 to 2.5% by weight), the relative dielectric constant εr was 2700 to 3700,
The dielectric loss tanσ is 2.5% or less, and the temperature characteristic is ±
14% or less, the tan σ when an AC voltage of 2000 V / cm is applied is 3.0% or less, and the insulation resistance (IR) is 3 to 9
× 10 ⁴ MΩ, which is a good product range. That is, the relative permittivity εr
High, excellent temperature characteristics, small dielectric loss tanσ,
Furthermore, a dielectric ceramic having a small AC voltage dependence of dielectric loss is achieved. Sample No. 5 (the amount of Nb ₂ O ₅ added:
2.6 parts by weight), the relative dielectric constant ε is 2200, and the temperature characteristics deteriorate. Therefore, in the present invention, the weight of Nb ₂ O ₅ added to barium titanate BaTiO ₃ is:
For 100 parts by weight of barium titanate BaTiO ₃ ,
The range was 0.8 to 2.5 parts by weight.

In Sample Nos. 6 to 10, the amount of MgO added to BaTiO _{3 as} the main component of the dielectric ceramic composition was varied from 0.05 to 0.75 parts by weight. At this time, Nb ₂ O ₅ , La ₂ O ₃ , and MnCO ₃ were added in amounts of 2.5 parts by weight, 0.2 parts by weight, and 0.1 parts by weight, respectively.

In sample No. 6 (addition amount of MgO: 0.05 parts by weight), the tan at an AC voltage of 2000 V / cm was applied.
σ becomes 4.0%. In addition, sample numbers 7 to 9
(Amount of added MgO: 0.06 to 0.70 parts by weight)
The relative dielectric constant ε becomes 2700-3100, and the dielectric loss ta
n σ is 2.0% or less, temperature characteristics are within ± 13%, tan σ is 2.8% or less when an AC voltage of 2000 V / cm is applied, and insulation resistance (IR) is 3 to 8 × 10 ⁴ M.
Ω and non-defective range. That is, a dielectric ceramic having a high relative dielectric constant ε, excellent temperature characteristics, a small dielectric loss tanσ, and a small AC voltage dependence of the dielectric loss is achieved.
Further, in sample No. 10 (the amount of added MgO: 0.75 parts by weight), the dielectric loss tanσ is 1.7%, which is a good range, but the relative dielectric constant ε is 2100. Therefore, in the present invention, barium titanate BaTiO ₃
The weight of MgO to be added is barium titanate BaTiO
_{3 With} respect to 100 parts by weight, the range was 0.06 to 0.70 parts by weight. In Sample Nos. 11 to 15, the amount of La ₂ O ₃ added to BaTiO _{3 as} the main component of the dielectric ceramic composition was changed from 0.004 to 0.53 parts by weight.

At this time, Nb ₂ O ₅ , MgO and MnCO
1.8 parts by weight ₃ of the added amount of each of 0.3 part by weight,
0.1 parts by weight.

Sample No. 11 (added amount of La ₂ O ₃ : 0.
004 parts by weight), the dielectric loss tanσ is 2.5%, but the relative dielectric constant εr is as low as 2350. Sample Nos. 12 to 14 (added amount of La ₂ O ₃ :
0.005 to 0.52 parts by weight), the relative dielectric constant εr is 2
800 to 3600, and the dielectric loss tan σ is 2.0%
And the temperature characteristic is within ± 11%, and tan σ when an AC voltage of 2000 V / cm is applied is 2.8% or less,
The insulation resistance (IR) is also 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 tanσ, and a small AC voltage dependence of the dielectric loss is achieved. Further, in Sample No. 15 (the amount of La ₂ O ₃ added: 0.53 parts by weight), the relative dielectric constant εr was 3800 and the dielectric loss tanσ was 1.8%, which was in the range of a good product, but the temperature characteristics deteriorated. Would.
Therefore, in the present invention, barium titanate BaTiO
Weight of La ₂ O ₃ to be added to the _3, titanate Baruumu B
0.005 to 0.5 with respect to 100 parts by weight of aTiO ₃
The range was 2 parts by weight.

In Sample Nos. 16 to 20, the amount of MnCO ₃ added to BaTiO _{3 as} the main component of the dielectric ceramic composition was varied from 0.005 to 0.31 part by weight.

At this time, Nb ₂ O ₅ , MgO and La ₂ O
The amounts of ₃ added were 1.8 parts by weight, 0.3 parts by weight, and 0.2 parts by weight.

Sample No. 16 (addition amount of MnCO ₃ : 0.1
005 parts by weight), the relative dielectric constant εr becomes 3000, but the dielectric loss tanσ becomes 2.6%. Further, the insulation resistance becomes 9 × 10 ³ . Sample No. 17
-19 (the amount of MnCO ₃ added: 0.01-0.3% by weight), the relative dielectric constant ε is 2800-3000, the dielectric loss tanσ is 2.2% or less, and the temperature characteristic is ± 6.
%, And ta when an AC voltage of 2000 V / cm is applied.
nσ is 3.0% or less and insulation resistance (IR) is 9 × 10 ⁴
２2 × 10 ⁵ MΩ, which is a good range. That is, a dielectric ceramic having a high relative permittivity εr, excellent temperature characteristics, a small dielectric loss tanσ, and a small AC voltage dependence of the dielectric loss is achieved. Further, in Sample No. 20 (the amount of MnCO ₃ added: 0.31 part by weight), the dielectric loss tanσ was 1.
The relative dielectric constant εr is 210%, which is a good product range of 4%.
It will be as low as 0. 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% by weight based on 100 parts by weight of barium titanate BaTiO ₃ .

Next, an embodiment of the present invention will be described.
First, the composition of Sample No. 13 in Table 1 was added to SiO ₂ and Al ₂
O ₃ and ZnO powder were added and contained as shown in Table 3,
In the same manner as in the above reference example, after forming into a tape shape, this tape was laminated, an internal electrode was formed, and a laminate was produced. And each characteristic was measured similarly to the said reference example, and was described in Table 4.

The composition of the sample was such that Nb ₂ O ₅ was 1.8 parts by weight, MgO was 0.3 parts by weight, La ₂ O _{3 was} 0.2 parts by weight, and MnO was 100 parts by weight of BaTiO _3. Mn
0.1 parts by weight in terms of CO ₃ , SiO ₂ , Al ₂ O
₃ , containing a predetermined amount of ZnO based on 100 parts by weight of BaTiO ₃ .

[0041]

[Table 3]

[0042]

[Table 4]

From these Tables 3 and 4, it can be seen that SiO ₂ , Al ₂
It can be seen that by containing O ₃ and ZnO, the firing temperature is lower and the dielectric constant is higher than in the case where these compounds are not contained (Sample No. 13).

[0044]

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. Further, as other properties, the dielectric loss tanσ is 2.5% or less and the insulation resistance (I
R) is 10 ⁴ MΩ or more, and a dielectric ceramic composition having tan σ of 3% or less when an AC voltage of 2000 V / cm is applied can be obtained.

Thus, for example, when a multilayer ceramic capacitor is made of the above-described dielectric ceramic composition, a small-sized and large-capacity capacitor having excellent temperature characteristics can be obtained. Inexpensive silver-palladium can be used as internal electrodes between the sheets, and an inexpensive multilayer ceramic capacitor can be obtained.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroshi Kojima 1-1, Yamashita-cho, Kokubu-shi, Kagoshima Kyocera Investigator, Kagoshima Kokubu Plant Co., Ltd. (A) JP-A-3-112859 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/46 H01B 3/12 CA (STN) REGISTRY (STN)

Claims (2)

(57) [Claims] (1) 100 parts by weight of BaTiO ₃ and N
0.8 to 2.5 parts by weight of b ₂ O ₅ and 0.06 to
0.70 parts by weight, La ₂ O ₃ is 0.005 to 0.520
0.01 to 0 in terms parts by weight of MnO to MnCO _3.
30 parts by weight, while containing 0.05 to 0.50 parts by weight of at least one of SiO ₂ and Al ₂ O ₃ ,
The dielectric ceramic composition the molar ratio of MgO nb ₂ O _5, characterized in that the in the range of 0.5-2.2. 2. The method according to claim 1, wherein 100 parts by weight of BaTiO _{3 is}
2. The dielectric porcelain composition according to claim 1, comprising 0.1 part by weight or less of nO.