JPH09315861A - Dielectric ceramics composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dielectric ceramics compsn. capable of ensuring stable characteristics even when a base metal such as Ni is used as an internal electrode. SOLUTION: A basic compsn. represented by the formula (Ba1-x Cax )m Ti1-y Zry ) O3 (where 0.01<=x<=0.10, 0.125<=y<=0.200 and 1.00<=m<=1.03) is prepd., 0.1-1.00mol% Nd2 O3 and 0.01-0.50mol% MgO are added to 100mol% of the basic compsn., and 0.2-3.0wt.% glass consisting of 30-80mol% SiO2 and 20-70mol% Li2 O and 0.1-0.3wt.% MnO2 is further added to 100wt.% of the basic compsn.

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 suitable for a laminated ceramic capacitor which can use a base metal material such as Ni for its internal electrodes.

[0002]

2. Description of the Related Art In a laminated ceramic capacitor, an internal electrode is printed on a green sheet of a dielectric material made of a predetermined dielectric ceramic composition, a plurality of green sheets are laminated, and the green sheet and the internal electrode are integrated. Is formed by firing.

However, since a conventional dielectric material containing BaTiO ₃ as a main component is processed at a high firing temperature of 1200 to 1500 ° C., it is exclusively used as a material for the internal electrodes, such as a noble metal such as Pt, Pd, or an alloy thereof. Was used.

Moreover, in such a laminated ceramic capacitor, if the number of laminated layers is increased in order to increase the capacity,
There is a problem in that the number of laminated internal electrodes also increases, resulting in a significant increase in cost.

Therefore, it has been attempted to use a relatively inexpensive base metal material such as Ni for the internal electrodes.

However, when the internal electrode of Ni, which is a base metal material, is used, since Ni is easily oxidized, it must be fired in a reducing atmosphere. Conversely, if firing in a reducing atmosphere, a normal dielectric material is used. There is a problem that the insulating property is deteriorated due to reduction.

Therefore, various non-reducing dielectric ceramic compositions have been proposed. For example, Japanese Examined Patent Publication No. 57-42588 may be mentioned.

[0008]

[Problems to be Solved by the Invention]
No. 42588 describes [(Ba _1-xy Ca _x Sr _y ) O].
A composition called _m TiO ₂ has been proposed. Although the dielectric material composed of such a dielectric ceramic composition can suppress the reduction reaction of the dielectric material that occurs during firing,
The firing temperature exceeded 1300 ° C., and when Ni was used for the internal electrodes of the laminated ceramic capacitor, the Ni particles showed an agglutination reaction, and stable electrode formation was difficult.

At the same time, there is a problem that Ni particles show a diffusion reaction in the dielectric ceramics and deteriorate the insulation resistance characteristics.

That is, the dielectric porcelain composition is a material which can suppress the reduction reaction of the porcelain even when fired in a reducing atmosphere and can be fired at a relatively low firing temperature (eg, 1250 ° C. or lower), and A material having a sufficiently high porcelain density after the firing treatment has been desired.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is to reduce the atmosphere in a reducing atmosphere.
It is intended to provide a dielectric ceramic composition which can be fired at a temperature of not higher than 0 ° C. and has excellent basic characteristics such as porcelain density, dielectric constant, dielectric loss and insulation resistance.

The firing temperature is 1250 ° C. or lower, the porcelain density is 5.7 g / cm ³ , and the dielectric constant is 80.
00 or more, dielectric loss 3.0% or less, insulation resistance value 1 × 10
¹¹ Ω or more is desired.

[0013]

[Means for Solving the Problems] Complex oxide (B
a _1-x Ca _x ) _m (Ti _1-y Zr _y ) O ₃ [wherein 0.01 ≦ x ≦ 0.10, 0.125 ≦ y ≦ 0.20
0, 1.00 ≦ m ≦ 1.03), and 0.1 to 1.0 of Nd ₂ O ₃ with respect to 100 mol% of the composite oxide.
0 mol% and 0.01 to 0.50 mol% of MgO are added, and SiO ₂ and Li ₂ O are added to 100% by weight of the basic component in which Nd ₂ O ₃ and MgO are added to the composite oxide.
A glass component containing (provided that SiO _{2 is} 30 to 80 mol%,
Li ₂ O: 20 to 70 mol%, the sum of SiO ₂ and Li ₂ O is 100 mol%) 0.2 to 3.0 wt% and MnO ₂
0.1 to 0.3% by weight is added to the dielectric ceramic composition.

[0014]

With such a dielectric porcelain composition, even if a base metal, such as Ni, is used for the internal electrodes of the laminated porcelain capacitor, the Ni particles exhibit an agglutination reaction because they are fired at a relatively low temperature. It is possible to produce a laminated ceramic capacitor having excellent characteristics such as dielectric constant, dielectric loss, and insulation resistance value without causing Ni particles to show a diffusion reaction in the dielectric ceramic.

In the above composite oxide, x represents the number of Ca atoms in the basic composition formula, and this Ca mainly acts as a depressor for flattening the temperature characteristics and as an element for increasing the insulation resistance value. To do.

If x is less than 0.01, the insulation resistance value will be less than 1.0 × 10 ¹¹ Ω, and x will be 0.
When it exceeds 10, the dielectric constant falls below 8000, and in any case, the basic characteristics of the laminated ceramic capacitor cannot be satisfied. Therefore, the value of x is 0.01 ≦ x ≦
The range of 0.10 is desirable.

In the above composite oxide, y represents the number of Zr atoms in the basic composition formula, and this Zr mainly acts as a shifter for moving the Curie point to the low temperature side.

When y is less than 0.125, the dielectric loss exceeds 3.0%, and the thickness of the dielectric layer becomes large. When y exceeds 0.200, the dielectric constant is 8%.
000, and in any case, the basic characteristics as a laminated ceramic capacitor cannot be satisfied. Therefore,
The value of y is preferably in the range of 0.125 ≦ x ≦ 0.200.

In the above composite oxide, when m is less than 1.00, the insulation resistance value is less than 1 × 10 ¹¹ Ω, and when m is more than 1.03, the porcelain density is 5.7.
If it is less than g / cm ³ , the sinterability is lowered and Ni diffusion reaction occurs.

Therefore, the value of m is preferably in the range of 1.00 to 1.03 mol%.

Although 0.1 to 1.00 mol% of Nd ₂ O ₃ is added to 100 mol% of such a composite oxide, Nd acts as a shifter for moving the Curie point to the low temperature side. It also serves to improve the dielectric constant.

When Nd ₂ O ₃ is less than 0.1 mol%, the dielectric loss exceeds 3.0%, and the dielectric constant also decreases. Also,
If it exceeds 1.00 mol%, the porcelain density will be 5.7 g / cm.
^{If it is} less than ³ , the sinterability is lowered and Ni diffusion reaction or the like occurs. Therefore, the amount of Nd ₂ O ₃ added is
The range of 0.1-1.00 mol% is preferable.

Similarly, with respect to 100 mol% of the composite oxide,
Although 0.01 to 0.50 mol% of MgO is added, M
g acts as an element that improves the insulation resistance value.

If the content of MgO is less than 0.01 mol%, the insulation resistance value will be less than 1 × 10 ¹¹ Ω, and 0.5
If it exceeds 0 mol%, the dielectric constant will decrease.

Therefore, the addition amount of MgO is 0.01 to
The range of 0.50 mol% is preferred.

As described above, the complex oxide is mixed with Nd ₂ O ₃ and M
For 100 wt% of the basic component added with gO, SiO
A glass component consisting of _2, Li ₂ O is added 0.2 to 3.0 wt%. When the glass component is less than 0.2% by weight and exceeds 3.0% by weight, the porcelain density is 5.7 g / cm ^3.
And the sinterability decreases.

This glass component contains SiO _{2 in an amount} of 30 to 80 mol% and Li ₂ O in an amount of 20 to 70 mol%, but if it is out of this range, the electrical characteristics and sinterability will deteriorate.

Further, Nd ₂ O ₃ and MgO are added to the composite oxide.
0.1 to 0.3 wt% of MnO ₂ is added to 100 wt% of the basic component added with. Mn has an effect of improving the sinterability and insulation resistance value. If it is less than 0.1% by weight, the porcelain density will be less than 5.7 g / cm ³ , and the sinterability will decrease, so If it exceeds, the dielectric constant will decrease.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the dielectric ceramic composition of the present invention will be described in detail.

The laminated porcelain capacitor according to the present invention comprises a porcelain body formed by alternately laminating dielectric layers made of a dielectric ceramic and internal electrodes, and first and second terminals formed on opposite end faces of the porcelain body. It is composed of electrodes.

The internal electrodes are formed, for example, such that adjacent internal electrodes are alternately led out to the facing end faces and are connected to the first terminal electrode or the second terminal electrode.

The dielectric is a dielectric material controlled to have the above composition, and the internal electrodes are made of a material containing Ni as a base metal as a main component.

In such a laminated ceramic capacitor, for example, the raw material oxides weighed at a predetermined ratio are calcined and crushed,
An organic vehicle is added, homogeneous mixing is performed, and tape molding is performed by a doctor blade method. Thereafter, the tape is cut into a predetermined size to obtain a green sheet. still,
Such a green sheet is large enough to extract a plurality of elements.

Next, a conductive paste, which is a homogeneous mixture of Ni powder and an organic vehicle, is screen-printed to form a conductor film to be an internal electrode on the green sheet.

In this way, the green sheets on which the conductor films to be the internal electrodes are formed are stacked in consideration of the direction of the internal electrodes leading out, and are pressure-bonded to be integrated.

Then, the green sheet laminate is cut,
The unfired porcelain body cut into individual pieces is
Baking is performed at 0 to 1250 ° C. or lower.

In the above-mentioned laminated porcelain capacitor, when a base metal material such as Ni is used for the internal electrodes, especially when the firing temperature is 1250 ° C. or lower, the agglomeration reaction of Ni particles can be suppressed, and the porcelain density can be improved, and Ni particles are It is possible to effectively suppress the diffusion into the porcelain, stably form the Ni internal electrode, and satisfy the electrical characteristics of the laminated porcelain capacitor.

[0038]

Example As starting materials, BaCo ₃ , CaCO ₃ ,
Special grade reagents of TiO ₂ and ZrO ₂ were weighed so as to have the values shown in Table 1, wet-processed in a ball mill, dried, and then calcined at 1200 ° C. for 2 hours in the air atmosphere, and further coarsely pulverized to perform complex oxidation. It was a thing.

Next, the glass component S having the values shown in Table 2 is added.
iO ₂ and Li ₂ O were weighed and mixed for 2 hours, 1300
It was melted at ℃ and poured into cold water to obtain glass cullet. Add IPA (isopropyl alcohol) to this cullet,
The mixture was wet mixed with a ball mill and dried to obtain a glass component.

Thereafter, as shown in Table 3, the basic component, the additive component and the glass component were weighed, wet-mixed with a ball mill, an organic vehicle was added, dried and granulated to obtain granulated powder.

The additive components Nd ₂ O ₃ and MgO
Is added to the composite oxide in an amount of a predetermined mol% based on 100 mol% of the composite oxide, and thus Nd ₂ O ₃ and Mg are added to the composite oxide.
To 100% by weight of the basic component added with O, a predetermined amount by weight (usually referred to as “parts by weight”) of glass component and MnO ₂ as an additional component are added later.

The formulation examples of Tables 1 to 3 are the cases of sample No. 4 in Table 4, and all the samples other than sample No. 4 were prepared by adjusting like the formulation examples of Tables 1 to 3. can do.

This granulated powder was put in a mold and 1 ton / cm.
^It was pressed at a pressure of ² to have a diameter of 10 mm and a thickness of about 2 mm to form a disk-shaped molded body. This molded body is debindered at 300 ° C. in the atmosphere and 3 × 10 ^{−8 to} 3
Firing was performed at 1150 to 1250 ° C in an atmosphere of × 10 ^-3 Pa, and then heat treatment was performed at 900 to 1100 ° C in a nitrogen atmosphere.

Copper paste was applied to both main surfaces of the thus obtained porcelain and baked at 850 ° C. in a reducing atmosphere.

At the same time, based on the above composition and in accordance with the above-mentioned manufacturing method, F characteristics, plane shape 3.6 mm × 1.6.
mm, the thickness of the dielectric layer was 6 μm (as a raw sheet), and about 50 layers were laminated on the internal electrodes via Ni to prepare a laminated ceramic capacitor.

As characteristics, the dielectric constant ε, the porcelain density and the dielectric loss tan δ were measured using the above-mentioned single plate capacitor,
At a reference temperature of 25 ° C, frequency 1 kHz, measurement voltage 1.0 Vr
The signal of ms was input, it measured using the digital LCR meter (4274A made from YHP), and it calculated considering the sample size. The insulation resistance value was the value obtained by applying a DC voltage of 250 V for 1 minute.

As an evaluation, the permittivity ε is an important characteristic for producing a small-sized capacitor having a high permittivity.
Those exceeding 0 were evaluated as good. Porcelain density is 5.7g for diffusion of base metal particles of internal electrode and maintenance of mechanical strength.
/ Cm ³ or more was considered good.

The dielectric loss tan δ is an important characteristic for realizing a thin dielectric green sheet and producing a small-sized capacitor having a high dielectric constant. A value of 1.0 × 10 ¹¹ Ω or higher was considered good.

The compositions and the results are shown in Tables 4 and 5.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

In the sample numbers 36 to 40, the effect of the range depending on the x value of the composite oxide can be understood.

As shown in sample No. 36, when x is "0", the dielectric loss tan δ becomes 3.7%, and the insulation resistance value IR becomes less than 1 × 10 ^9. . When the value of x exceeds 0.1 as in sample No. 40, the permittivity ε is far below 6800 and 8000.

Therefore, the value of x is 0.01 ≦ x ≦
A desirable value of 0.10. For the other samples, the central value x = 0.05 is used.

In the sample numbers 31 to 35, the effect of the range depending on the y value can be understood.

As shown in sample No. 31, the value of y is 0.0
In the case of 1, the dielectric loss tan δ becomes 3.8%,
At the same time, a dielectric constant ε of only about 6000 can be obtained. Also,
When the value of y is 0.225 as in sample No. 35, the dielectric constant ε is less than 7600 and 8000.

From this, the value of y is 0.125 ≦ y
The range of ≦ 0.200 is desirable. For other samples,
The central value y = 0.15 is used.

In Sample Nos. 26 to 30, the action of the range depending on the value of m of the basic component can be understood.

As shown in sample No. 26, the value of m is 0.9.
In case of 9, the dielectric loss tan δ becomes 3.5%,
At the same time, the insulation resistance value IR becomes 1 × 10 ⁹ Ω.
When m is 1.04 as in Sample No. 30, a sufficient porcelain density (5.7 g / cm ³ ) could not be obtained even if it was fundamentally fired at 1300, and other characteristics Cannot be the subject of evaluation.

From this, the value of m is 1.00≤m≤
The range of 1.03 is desirable. For the other samples, the central value m = 1.02 is used.

Next, regarding the molar ratio of the additive component Nd ₂ O _{3 to} the composite oxide, the action can be understood with sample numbers 20 to 25.

In Sample No. 20, the amount of Nd ₂ O ₃ added was 0.0
At 5 mol%, the dielectric loss tan δ increases to 3.5%, and at the same time the dielectric constant ε becomes 5800. Also,
In Sample No. 25, when the amount of Nd ₂ O ₃ added was 2.0 mol%,
Sufficient porcelain density (5.7 g / cm ³ ) cannot be obtained.

When the amount of Nd ₂ O ₃ added in Sample No. 21 is 0.1 mol%, the dielectric loss tan δ and the dielectric constant ε are improved, and it can be said that the dielectric ceramic composition exhibits stable characteristics. Further, in Sample No. 24, when the amount of Nd ₂ O ₃ added is 1.0 mol%, the porcelain density is 5.87 g / cm ³ , which can be said to be a dielectric porcelain composition exhibiting stable characteristics.

From this, it is desirable to add Nd ₂ O _{3 in} the range of 0.1 to 1.0 mol% with respect to 100 mol% of the basic composition.

Regarding the molar ratio of the additive component MgO to the composite oxide, its action can be understood in Sample Nos. 16 to 19.

When the amount of MgO added was 0 in the sample No. 16, the insulation resistance value IR was below 10 ¹¹ Ω, and the sample No. 19
When the added amount of MgO is 1.0 mol%, the dielectric constant ε is 680.
It will be 0.

When the amount of MgO added in Sample Nos. 17 and 18 is 0.1 to 0.05 mol%, the insulation resistance value IR and the dielectric constant ε are improved, and the dielectric ceramic composition exhibits stable characteristics. Can be said.

Next, SiO ₂ and L constituting the glass component
With respect to the mol% of i ₂ O, the action can be understood in sample numbers 4, 8 to 11. The glass component is 100% by weight of the basic component obtained by adding the above-mentioned additional components to the complex oxide
It is to be added.

Sample No. 8 contained 20 mol% SiO ₂ (Li
₂ O is 80 mol%), the dielectric constant ε is 4700 and 800
It is much lower than 0, and SiO ₂ is 9 in sample number 11.
At 0 mol% (30 mol% of Li ₂ O), a sufficient porcelain density (5.7 g / cm ³ ) cannot be obtained.

Therefore, the glass components are sample numbers 4, 9 and
10, SiO ₂ is 30 to 80 mol%, LiO ₂ 20
It is important to set the content to ˜70 mol%.

[0074] As the components of the glass, for other samples, the SiO ₂ 80 mol%, a sample is prepared by the LiO ₂ and 20 mol%.

Next, the above-mentioned glass components to be added to the basic components can be understood from Sample Nos. 1 to 7, and their operation can be understood.

When sample No. 1 was not added to the glass component at all, a sufficient value (5.7 g / cm ³ ) of porcelain density could not be obtained even at a firing temperature of 1300, and other properties were evaluated. Even if the glass component of Sample No. 7 was added in an amount of 5.0% by weight with respect to the basic component, the porcelain density was at a sufficient value (5.7 g / c) even at a firing temperature of 1300.
m ³ ) cannot be obtained. By controlling the addition amount to be 0.2 to 3.0% by weight as in Sample Nos. 2 to 6, the porcelain density can be improved and other characteristics can be stabilized.

Finally, with respect to the weight% of the additive component MnO ₂ , the action can be understood in sample numbers 12 to 15.

In sample No. 12, when the amount of MnO ₂ added was 0,
Sufficient porcelain density (5.7g /
cm ³ ) cannot be obtained. In addition, when 0.4% by weight is added to Sample No. 15, the dielectric constant ε is much lower than 4800 and 8000.

As described above, from the above example, when a base metal material such as Ni is used for the internal electrodes, it can be fired at 1250 ° C. or lower in order to suppress the agglomeration reaction of the metal particles of the base metal material. In order to prevent the particles from diffusing into the porcelain, the density of the porcelain is set to 5.7 g / cm ³ , and the dielectric porcelain composition has excellent dielectric constant ε, dielectric loss tan δ and insulation resistance IR. to, as described above, the basic components _{x, y, m, Nd 2} O 3, mole% of MgO, mol% of SiO _2, Li ₂ O of the glass component, by weight% of the glass component further, MnO It will be achieved by strictly controlling the weight percentage of ₂ .

[0080]

As described above, according to the dielectric ceramic composition of the present invention, it is fired at 1150 to 1250 ° C. in a reducing atmosphere with an oxygen partial pressure of 3 × 10 ^{−8 to} 3 × 10 ⁻³ Pa. Also,
Since a ceramic with a high dielectric constant, a high insulation resistance value IR, and a small dielectric loss tan δ can be obtained, a base metal material such as Ni can be used inside, and a low-cost laminated ceramic capacitor can be achieved. Become.

Claims (1)

[Claims] 1. A composite oxide (Ba _1-x Ca _x ) _m (Ti
_1-y Zr _y ) O ₃ [wherein 0.01 ≦ x ≦ 0.1
0, 0.125 ≦ y ≦ 0.200, 1.00 ≦ m ≦ 1.
03), Nd ₂ O ₃ is added in an amount of 0.1 to 1.00 mol% and MgO is added in an amount of 0.01 to 0.50 mol% with respect to 100 mol% of the composite oxide. Basic component 100 with Nd ₂ O ₃ and MgO added
A glass component containing SiO ₂ and Li ₂ O with respect to weight% (however, SiO ₂ : 30 to 80 mol%, Li ₂ O: 70 to
20 mol%, the sum of SiO ₂ and Li ₂ O is 100 mol%)
0.2-3.0 wt% and MnO ₂ 0.1-0.3
A dielectric porcelain composition characterized by being added in a weight percentage.