JP3250917B2 - Dielectric porcelain composition - 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 porcelain composition, and more particularly to a dielectric porcelain composition used for capacitors, resonators and the like.

[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 ₂ O ₃ , M
It contains nO, ZnO, SiO ₂ and / or Al ₂ O ₃ at a predetermined composition ratio, and the molar ratio of Nb ₂ O _{5 to} the total amount of ZnO and MgO is set to 0.5 to 2.2. The dielectric constant is 2500 or more, the temperature change rate of the capacitance satisfies EIA standard X7R, the dielectric loss is as small as 2.5% or less, and the dielectric loss is 3 even when an AC voltage of 2000 V / cm is applied. 0% or less and low AC voltage dependency,
The present inventors have found that a dielectric porcelain that can be made thinner can be obtained, and have reached the present invention.

That is, the dielectric porcelain of the present invention is made of BaTiO.
_{3 With} respect to 100 parts by weight, Nb ₂ O ₅ is 0.8 to 2.5 parts by weight, MgO is 0.06 to 0.70 parts by weight, La ₂ O ₃ is 0.005 to 0.520 parts by weight, MnO is converted to MnCO ₃ at 0.01 to 0.30 parts by weight, and ZnO is 0.1 to
0.5 part 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 molar ratio of Nb ₂ O _{5 to} the total amount of ZnO and MgO is 0.
It is in the range of 5-2.2.

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 properties and the sinterability are poor, and when it exceeds 2.5 parts by weight, the relative dielectric constant is lowered, and the temperature characteristics are greatly deteriorated. 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 .

Further, the reason why ZnO is set to 0.10 to 0.50 parts by weight is that if less than 0.10 parts by weight, the insulation resistance is low.
This is because the dielectric loss and sinterability deteriorate, and if it exceeds 0.50 parts by weight, the relative dielectric constant decreases, and the temperature characteristics deteriorate. It is desirable that ZnO be 0.10 to 0.30 parts by weight.

[0015] Then, N with respect to the total amount of ZnO and MgO is
The reason why the molar ratio of b ₂ O ₅ is 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 are poor. This is because the characteristics are poor and the relative dielectric constant is reduced. In the present invention, ZnO and MgO
The molar ratio of Nb ₂ O _{5 to} the total amount of
It is desirable to be 1.4.

If at least one of SiO ₂ and Al ₂ O ₃ is contained in an amount of 0.05 to 0.50 parts by weight with respect to 100 parts by weight of BaTiO ₃ , the firing temperature may be further lowered depending on the composition, and the static electricity may be reduced. Capacitance and relative permittivity can be increased. The above effects of SiO ₂ and Al ₂ O ₃ are not so remarkable when the amount is less than 0.05 part by weight, and the relative dielectric constant tends to decrease when the amount is more than 0.50 part by weight. It is. At least one of SiO ₂ and Al ₂ O ₃ is BaTiO ₃ 1
It is desirable to contain 0.1 to 0.2 parts by weight based on 00 parts by weight.

The dielectric porcelain of the present invention comprises, as a main component, BaTiO ₃ powder having an average crystal grain size of 1.0 μm or less, which is produced by a solid phase sol-gel method, an oxalic acid method, a hydrothermal synthesis method or the like. Nb ₂ O ₅ , MgO, La ₂ O ₃ , MnCO ₃ , S based on 100 parts by weight of this BaTiO ₃
A predetermined amount of each of iO ₂ , Al ₂ O ₃ , and ZnO powder is weighed, wet-pulverized by a ball mill or the like for 20 to 48 hours, dried, and then added with a predetermined amount of an organic binder and the like, and molded into a predetermined shape. 1-2 at 1200 ° C-1300 ° C in air
It is manufactured by firing for a time. In the case of producing a multilayer ceramic capacitor, the above powder is slurried, formed into a sheet by a method such as a doctor blade, and an internal electrode such as Ag-Pd is applied to the sheet-shaped molded body as appropriate. A plurality of these may be laminated and fired simultaneously under the above firing conditions.

The Nb ₂ O ₅ , M used in the present invention
gO, La ₂ O ₃ , MnCO ₃ , SiO ₂ , Al
Instead of powders of ₂ O ₃ and ZnO, Nb, Mg, L
a, Mn, Si, Al, Zn hydroxides, carbonates, nitrates, oxalates, alkoxides, etc., which decompose below the sintering temperature to become oxides, 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,
In addition to controlling the particle size after pulverization to 0.8 μm or less by wet pulverization for a long time, it is necessary to set the baking temperature as low as possible and shorten the baking time.

[0020]

According to the dielectric ceramic composition of the present invention, the temperature characteristic of the capacitance is within ± 15% within 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]

EXAMPLES Examples of the present invention will be described below in detail with reference to Reference Examples.

[0022] as a main component (Reference Example) Average particle size 1.0μm or less of BaTiO ₃ powder produced by hydrothermal synthesis method, the BaTiO ₃ 10
Nb ₂ O ₅ , MgO, La ₂ O ₃ , Mn
Each powder of CO ₃ and ZnO 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 15 μm thick by a doctor blade method. Into a tape shape. 13 this tape
The sheet is cut into 0 mm × 100 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. Further, electrodes 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 the 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, the 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, the added amounts of MgO, La ₂ O ₃ , MnCO ₃ and ZnO were 0.1 parts by weight, 0.2 parts by weight,
Parts by weight, 0.1 to 0.2 parts by weight.

Sample No. 1 (the amount of Nb ₂ O ₅ added: 0.7
(Parts by weight), the dielectric constant εr is 3700, which is a good product, but the dielectric loss tan δ is 3.4%. Further, the temperature characteristic becomes -25%. In sample numbers 2 to 4 (the amount of Nb ₂ O ₅ added: 0.8 to 2.5% by weight), the relative dielectric constant εr was 2700 to 3600,
The dielectric loss tan δ is 2.5% or less, and the temperature characteristic is ±
13% or less, tan δ when an AC voltage of 2000 V / cm is applied is 3.0% or less, and insulation resistance (IR) is 4-6.
× 10 ⁴ MΩ, which is a good product range. That is, the relative permittivity εr
High, excellent temperature characteristics, small dielectric loss tanδ,
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 2300, 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 based on 100 parts by weight of barium titanate BaTiO ₃ .

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 , MnCO ₃ and ZnO
Was adjusted to 1.8 to 2.5 parts by weight, 0.2 parts by weight, 0.1 parts by weight, and 0.1 to 0.2 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.
δ becomes 3.8%. In addition, sample numbers 7 to 9
(Amount of added MgO: 0.06 to 0.70 parts by weight)
The relative dielectric constant εr becomes 2600 to 2900, and the dielectric loss t
is less than ± 13%, the tan δ is 2.8% or less when an AC voltage of 2000 V / cm is applied, and the insulation resistance (IR) is 3 to 5 × 10 ⁴ M.
Ω and non-defective 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 dependence of the dielectric loss is achieved. Furthermore, in sample No. 10 (the amount of added MgO: 0.75 parts by weight), the dielectric loss tan δ is 1.8%, which is a good range, 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 based on 100 parts by weight of TiO ₃ . Sample Nos. 11 to 15 are La ₂ O ₃ added to BaTiO ₃ which is a main component of the dielectric ceramic composition.
Was varied from 0.004 to 0.53 parts by weight.

At this time, Nb ₂ O ₅ , MgO, MnCO ₃
And the amount of ZnO added was 1.8 parts by weight, 0.2 parts by weight, 0.1 parts by weight, and 0.2 parts by weight, respectively.

Sample No. 11 (added amount of La ₂ O ₃ : 0.
004 parts by weight), the dielectric loss tan δ is 2.4%, but the relative dielectric constant εr is as low as 2400. 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 3500, and the dielectric loss tan δ is 2.1%
And the temperature characteristics are within ± 11%, and tan δ when an AC voltage of 2000 V / cm is applied is 2.8% or less,
The insulation resistance (IR) is 3 to 6 × 10 ⁴ MΩ, which is a good 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 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 3700 and the dielectric loss tan δ was 1.8%, which was a good product range, but the temperature characteristics deteriorated. Would.
Therefore, in the present invention, barium titanate BaTiO
Added to ₃ weight of La ₂ O ₃ is barium titanate 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, La ₂ O ₃
And the amount of ZnO added is 1.8 parts by weight, 0.2 parts by weight,
0.2 parts by weight, 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 tan δ becomes 2.5%. Further, the insulation resistance becomes 8 × 10 ³ MΩ. In sample numbers 17 to 19 (the amount of MnCO ₃ added: 0.01 to 0.3% by weight), the relative dielectric constant εr was 2800 to 3000, the dielectric loss tan δ was 2.2% or less, and the temperature characteristics Is within ± 7%, the tan δ when an AC voltage of 2000 V / cm is applied is 3.0% or less, and the insulation resistance (IR) is 2 ×.
10 ^{4 to} 9 × 10 ⁴ MΩ, which is a good range. That is, the dielectric constant εr is high, the temperature characteristics are excellent, and the dielectric loss tan δ
And a dielectric porcelain having a small AC loss dependence on dielectric loss. Further, sample number 20 (MnCO
₃ is 0.31 part by weight), the dielectric loss tan δ
Is 1.4%, which is a good product range, but the relative dielectric constant εr is as low as 2200. Therefore, in the present invention, MnCO ₃ added to barium titanate BaTiO ₃ is used.
Weight, relative to barium BaTiO ₃ 100 parts by weight titanate, ranged from 0.01 to 0.3 parts by weight.

Sample Nos. 21 to 26 are cases in which the amount of ZnO added to BaTiO _{3 as} the main component of the dielectric ceramic composition was changed from 0.1 to 0.8 parts by weight. At this time, Nb ₂ O ₅ , MgO, La ₂ O ₃ and M
1.8 to 2.1 parts by weight of nCO ₃ each,
0.1 to 0.15 parts by weight, 0.2 parts by weight, and 0.1 parts by weight.

Sample Nos. 21 to 25 (Amount of ZnO added:
0.1 to 0.5 parts by weight), the relative dielectric constant εr is 2800
To 3200, the dielectric loss tan δ is 1.8% or less, the temperature characteristics are within ± 14%, and the AC voltage 200
When 0 V / cm is applied, tan δ is 2.8% or less, and the insulation resistance (IR) is 4 to 5 × 10 ⁴ MΩ, which is a good 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 dependence of the dielectric loss is achieved. In sample No. 26 (addition amount of ZnO: 0.8 parts by weight), the dielectric loss tan δ was 2.0%, which was a good product, but the relative dielectric constant εr was low, 2200, and the temperature characteristics and insulation resistance were deteriorated. I do. Therefore, in the present invention, barium titanate Ba
The amount of ZnO added to TiO ₃ is barium titanate Ba.
The range was 0.1 to 0.5 parts by weight based on 100 parts by weight of TiO ₃ .

(Example) Sample No. 1 in Table 1 As shown in Table 3, SiO ₂ and Al ₂ O ₃ powders were added to and contained in the composition of No. 13 and formed into a tape in the same manner as in Reference Example, and then the tape was laminated to form internal electrodes. A laminate was produced. And each characteristic was measured similarly to the 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 0.2 parts by weight, La ₂ O _{3 was} 0.2 parts by weight, and MnO was 100 parts by weight of BaTiO _3. Mn
It contains 0.1 parts by weight in terms of CO ₃ , 0.2 parts by weight of ZnO, and a predetermined amount of SiO ₂ and Al ₂ O _{3 based} on 100 parts by weight of BaTiO ₃ .

[0044]

[Table 3]

[0045]

[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 , the firing temperature is lower and the dielectric constant is higher than in the case where these compounds are not contained (sample No. 13).

[0047]

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

Thus, for example, when a laminated ceramic capacitor is made of the above-described dielectric ceramic composition, a small-sized and large-capacity capacitor excellent in temperature characteristics can be obtained, and the firing temperature is 1300 ° C. or less, and Inexpensive silver-palladium can be used as an internal electrode between the formed sheets, and an inexpensive multilayer ceramic capacitor can be obtained.

Continuation of the front page (56) References JP-A-3-112859 (JP, A) JP-A-61-99208 (JP, A) JP-A-8-183658 (JP, A) JP-A-8-151260 (JP, A) JP-A-8-169759 (JP, A) JP-A-7-187780 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 35/42-35/50 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] (1) 100 parts by weight of BaTiO ₃ and Nb ₂
O ₅ and 0.8 to 2.5 parts by weight, the MgO .06 to 0.
70 parts by weight, 0.005 to 0.520 parts by weight of La ₂ O ₃ and 0.01 to 0.30 of MnO converted to MnCO _3.
Parts by weight, 0.1 to 0.5 parts by weight of ZnO, and further SiO
0.05 at least one of the _two and Al ₂ O ₃
Together containing 0.50 parts by weight, the dielectric ceramic composition the molar ratio of Nb ₂ O ₅ with respect to the total amount of ZnO and MgO, characterized in that the in the range of 0.5-2.2.