JPH04260661A - Irreducible dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To provide an irreducible dielectric ceramic composition sinterable at a low temperature (<=1080 deg.C) and free from deterioration of the electric characteristics even by baking in a reducing atmosphere. CONSTITUTION:The objective irreducible dielectric ceramic composition contains (A) 85.0-99.95wt.% of main components composed of 30.0-85.0mol% of Pb(Ni1/3 Nb2/3)O3, 1.0-69.0mol% of Pb(Zn1/3Nb2/3)O3 and 1.0-35.0mol% of PbTiO3 and (B) 0.05-15.0wt.% of subsidiary component expressed by the general formula aLi2O+bRO+cB2O3+(100-a-b-c)SiO2 (RO is at least one kind of oxide selected from MgO, CaO, SrO and BaO; a, b and c are mol% satisfying the formulas 0<=a<20, 10<=b<55 and 0<=c<40).

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a non-reducible dielectric ceramic composition, and in particular, a Pb composite perovskite type dielectric ceramic material as a main component has a subcomponent effective in preventing reduction of the dielectric ceramic. The present invention relates to a non-reducible dielectric ceramic composition that is used in a ceramic multilayer capacitor by being fired simultaneously with an internal electrode material made of a base metal.

0002

[Prior Art] Conventionally, ceramic multilayer capacitors with Pb-based high permittivity ceramic materials as dielectrics and Ag-Pd-based or Pt-based alloys as internal electrodes have required small size, large capacity, and high reliability. It has been widely used in various consumer and industrial electronic circuits. In order to manufacture a porcelain multilayer capacitor, for example, a porcelain green sheet with a thickness of 30 to 50 μm is created by a doctor blade method, a metal conductor layer that becomes an internal electrode is formed on this porcelain green sheet, and a plurality of these sheets are formed. They are laminated and integrated by thermocompression bonding, and the integrated product is fired at, for example, 1050 to 1200°C in a natural atmosphere to create a sintered body, and the end face of the sintered body is provided with an external lead-out electrode that is electrically connected to the internal electrode. was burned.

0003

SUMMARY OF THE INVENTION In conventional ceramic multilayer capacitors, the material for the internal electrodes must satisfy the following two conditions. First, since the dielectric porcelain material and the internal electrode material are fired at the same time, they have a melting point higher than the sintering temperature of the dielectric porcelain material, and second, they do not oxidize even in an oxidizing high-temperature atmosphere. Moreover, it does not react with dielectric materials. Noble metals such as platinum, gold, palladium, or alloys thereof are available as electrode materials that satisfy these conditions, and until now these precious metals have been mainly used as internal electrode materials for ceramic multilayer capacitors. However, although these electrode materials have excellent characteristics, they are expensive, and for this reason, the proportion of electrode material costs in ceramic multilayer capacitors is 30 to 70%.
%, and was the biggest factor in increasing costs.

On the other hand, as an electrode material other than noble metals, Ni
There are base metals such as , Fe, Co, and Cu, but in recent years, there has been an increasing demand for electronic components to be compatible with high frequencies, and materials with high conductivity and low equivalent series resistance are required as internal electrodes for ceramic multilayer capacitors. There is. For this reason, it has been considered to use Cu or a Cu-based alloy among base metal internal electrode materials. However, base metals such as Cu and Cu-based alloys are easily oxidized in a high-temperature oxidizing atmosphere and no longer function as an electrode. Therefore, in order to use these base metals for the internal electrodes of a ceramic multilayer capacitor, it is necessary to sinter them together with a dielectric ceramic material in a neutral or reducing atmosphere.

However, conventional dielectric ceramic materials have the disadvantage that when fired in such a reducing atmosphere, they are significantly reduced and become semiconductors. Furthermore, since the melting point of Cu and Cu-based alloys is 1080° C. or lower, the sintering temperature of the dielectric material must be lower than that.

[0006] Therefore, when a metal that is easily oxidized and has a low melting point, such as Cu or a Cu-based alloy, is used as the internal electrode of a multilayer capacitor, a dielectric material that has excellent reduction resistance and can be sintered at low temperatures is required. It is.

[0007] Therefore, the main objectives of this invention are: 1.
It is an object of the present invention to provide a non-reducible dielectric ceramic composition which can be sintered at a low temperature of 080° C. or lower and whose electrical characteristics do not deteriorate even when fired in a reducing atmosphere.

[0008]

[Means for Solving the Problems] This invention provides Pb(Ni
1/3 Nb2/3 )O3 ,Pb(Zn1/3 N
The blending ratio (mol%) of b2/3)O3 and PbTiO3 is Pb(Ni1/3 Nb2/3)O3
30.0~85.0, Pb(Zn1/3 Nb2/3
)O3 1.0-69.0, and PbTiO3
Main component within the range of 1.0-35.0 85.0-
For 99.95% by weight, the general formula is aLi2O+bRO+cB2O3+(100-a
-b-c) SiO2 (However, RO is MgO, CaO
, SrO and BaO, a, b and c are mol%), and a, b and c are respectively 0≦a<20
, 10≦b<55, 0≦c<40 in an amount of 0.05 to 15.0% by weight.

[0009]

Effects of the Invention The non-reducible dielectric ceramic composition according to the present invention has excellent reduction resistance, does not deteriorate in dielectric properties and insulation resistance even after reduction firing, has a specific resistance of 1010 Ωcm or more, and has a dielectric constant of 1010 Ωcm or more. It has a dielectric loss of 3,000 or more and a dielectric loss of 3% or less, and has excellent sinterability, and can be sintered at a low temperature of 1,080°C or less. Therefore, if the non-reducible dielectric ceramic composition according to the present invention is used as a ceramic multilayer capacitor material, Cu or a Cu-based alloy can be used as the internal electrode material. Therefore, compared to conventional capacitors using noble metals, it is possible to obtain a ceramic multilayer capacitor that is less expensive and has a smaller equivalent series resistance.

The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0011]

[Example] Pb3O, an industrial raw material, as a starting material
4, Nb2O5, TiO2, NiO, ZnO, etc. were prepared. Weigh these raw materials and preliminarily prepare Pb(N
i1/3 Nb2/3 )O3 ,Pb(Zn1/3
Nb2/3)O3 and PbTiO3 were blended, wet mixed in a ball mill for 16 hours, and then evaporated to dryness to obtain a mixed powder. The obtained mixed powder was put into a zirconia box and PbT
iO3 was calcined at 950°C, and other compositions were calcined at 850°C for 2 hours to obtain desired compounds.

Next, the compound thus obtained was coarsely ground so as to pass through a 200 mesh sieve, and then mixed so as to obtain the desired compounding ratio of each of the dielectric materials in sample numbers 1 to 24 shown in Table 1. It was blended into.

[0013]

[Table 1]

[0014] Furthermore, as a subcomponent, in order to obtain a reduction inhibitor which has an excellent effect of preventing reduction of dielectric porcelain when fired in a reducing atmosphere, for example, reduction inhibitors in sample numbers 31 to 58 shown in Table 2, , mix the oxides, carbonates, or hydroxides of each component, and mill them in a ball mill for 16 minutes.
After wet mixing and pulverization for a period of time, the mixture was evaporated and dried to obtain a powder. The obtained powder was placed in an alumina crucible and left at a temperature of 1300° C. for 1 hour, and then rapidly cooled to vitrify. Coarsely grind this to pass through a 200 mesh sieve,
A reduction inhibitor was prepared.

[0015]

[Table 2]

Next, Table 1 and Table 2 are applied to the above dielectric material.
A reduction inhibitor was added in the proportion shown in . In this case, in sample numbers 1 to 24, sample numbers 32 to 3
5, 56-58, 5Li2 O+20BaO+
15CaO+5SrO+5MgO+25B2 O3 +
A reduction inhibitor of 25SiO2 was added. In addition, in sample numbers 31 to 58, 70Pb(Ni1/3 Nb2/3)O3 + was used as the dielectric material, similar to sample number 8.
10Pb(Zn1/3 Nb2/3)O3 +20P
A dielectric material of bTiO3 was used.

A polyvinyl butyral binder and an organic solvent were added thereto, wet mixed in a ball mill for 16 hours, and formed into a sheet by a doctor blade method to obtain a porcelain green sheet. After drying this porcelain green sheet, it was cut into an appropriate size, a Cu electrode paste was printed on the cut porcelain green sheet by a screen printing method, and a predetermined number of sheets were stacked and thermocompression bonded to obtain a laminate. After cutting the obtained laminate into a predetermined standard, a Cu electrode paste was applied as an external electrode to obtain a raw unit. This raw unit is N2, H2
It was placed in an electric furnace adjusted to a reducing atmosphere that does not oxidize the Cu electrode using a mixed gas of H2O and 820~10
A ceramic multilayer capacitor was obtained by firing at 80° C. for 2 hours.

The obtained porcelain multilayer capacitor was immersed in a sintering solution to test the degree of sintering, and the optimum firing temperature was determined. Furthermore, 1kHz, 1Vrms at a temperature of 25°C
The electrical characteristics of dielectric constant ε, dielectric loss tan δ, and insulation resistance were measured. Sample numbers 1 to 24 and sample number 3
Table 3 and Table 4 show the optimum firing temperature and electrical characteristics of No. 1 to No. 58.
are shown respectively.

[0019]

[Table 3]

[0020]

[Table 4]

Further, FIG. 1 shows the composition ratios of dielectric materials as main components in sample numbers 1 to 58 in a three-component composition diagram. In this case, the numbers in the figure represent each sample number.

Furthermore, in FIG. 1, regions showing the composition ratios of dielectric materials as main components within the scope of the present invention are shown as pentagons with composition points A, B, C, D, and E as vertices. Indicated. That is, the main components in the non-reducible dielectric ceramic composition according to the present invention are [Pb(Ni1/3 Nb2/
3)O3]x+[Pb(Zn1/3 Nb2/3
)O3 ]y+[PbTiO3]z (however, x+y
+z=1.00), when x, y and z are expressed as A (0.64, 0.01, 0.35)B in the three-component composition diagram in Figure 1.
(0.30, 0.35, 0.35)C (
0.30, 0.69, 0.01)D (0.
85, 0.14, 0.01)E (0.85
, 0.01, 0.14).

In order to obtain the main component in the non-reducible dielectric ceramic composition according to the present invention, for example, Pb3
O4: 66.60 to 69.20 (wt%),
NiO: 2.17-6.27
(wt%), ZnO: 0.08~
5.45 (wt%), Nb2O5: 1
7.38-25.63 (wt%), and TiO2: 0.23-8.47
(% by weight) of each oxide may be used.

The reason for limiting the ranges of the main component and subcomponents as described above in this invention is as follows. First, the reason for limiting the main components will be explained. Outside the line connecting composition points A and B in FIG. 1, that is, in a range where PbTiO3 is more than 35 mol %, the dielectric loss becomes larger than 3.0%, which is not preferable, as shown in sample numbers 1 and 2. Similarly, outside the line connecting composition points B and C, that is, P
Even in the range where b(Ni1/3 Nb2/3)O3 is less than 30 mol%, or outside the line connecting composition points A and E, that is, in the range where Pb(Zn1/3 Nb2/3)O3 is less than 1 mol%. As shown in sample numbers 10 and 11 and sample numbers 6 and 7, the dielectric loss is greater than 3.0%, which is undesirable. Also, outside the line connecting composition points C and D, that is, in the range where PbTiO3 is less than 1 mol %, or outside the line connecting composition points D and E, that is, P
In a range in which b(Ni1/3 Nb2/3 )O3 is more than 85 mol %, the dielectric constant becomes less than 3000, as shown in sample numbers 18, 19, 20 and sample number 13, which is not preferable.

[0025] Next, the reason for limiting the reduction inhibitor as an auxiliary component will be explained. As shown in sample numbers 44, 45, 46 and 47, when b is less than 10 mol%,
The insulation resistance becomes smaller than 1010 Ωcm, and the dielectric loss becomes larger than 3.0%, which is not preferable. Also,
As in sample numbers 36, 37, 38 and 39, b is 5
If it exceeds 5 mol%, the firing temperature will exceed 1080°C, which is not preferable. Like sample number 52, Li2
O is 20 mol% or more, or B as in sample number 54
If 2O3 exceeds 40 mol%, the dielectric properties will be significantly impaired or the material will be softened and deformed before sintering is completed. Furthermore, when the amount of reduction inhibitor added is less than 0.05% by weight, as in Sample No. 31, sintering of the dielectric is insufficient and reduction progresses, resulting in deterioration of insulation resistance. Also,
If the amount of the reduction inhibitor added exceeds 15% by weight, as in Sample No. 58, the dielectric constant becomes less than 3000, which is not preferable.

[0026] In the non-reducible dielectric ceramic composition according to the present invention, 2 mol% of the main component is contained in the composition.
Even if MnO2, Fe2 O3, Cr2 O3, or CoO is added up to this level, the properties will not be impaired in any way.

[0027] In the above-mentioned examples, as a reduction inhibitor, an agent which was previously blended in a predetermined proportion, heat-treated at high temperature to melt it, and then crushed and vitrified was added and mixed with the main component. However, other methods for adding the reducing inhibitor include adding a powder that has been blended in a predetermined ratio and heat-treated, or adding the reducing inhibitor individually to the main components. .

[0028] When firing a laminate consisting of a Pb composite perovskite dielectric material and a Cu-based internal electrode material, it is necessary to maintain it in an oxygen atmosphere in which the dielectric is not reduced and the internal electrodes are not oxidized. be. That is, when the dielectric substance is reduced, the insulation resistance decreases, and when the internal electrodes are oxidized, problems such as an increase in the equivalent series resistance occur, and in either case, the capacitor loses its function as a capacitor.

On the other hand, according to the present invention, by adding a reduction inhibitor to the dielectric material, the oxygen partial pressure in the firing atmosphere spreads particularly to the low oxygen partial pressure side. It is possible to obtain products with a high yield rate under an appropriate reducing atmosphere without any control. That is, the non-reducible dielectric ceramic composition according to the present invention is not easily reduced even when fired in a reducing atmosphere. Porcelain made of such a composition does not deteriorate in dielectric properties or insulation resistance, has a specific resistance of 1010 Ωcm or more, has a dielectric constant of 3000 or more, and has a dielectric loss of 3% or less. Furthermore, the non-reducible dielectric ceramic composition according to the present invention has a firing temperature of 1050° C. or lower. Therefore, if the non-reducible dielectric ceramic composition according to the present invention is used as a material for a multilayer capacitor, Cu or Cu can be used as an internal electrode material.
A series alloy etc. can be used. As a result, the cost can be significantly reduced compared to the case where conventional noble metal electrodes such as Pd-Ag or Pt-based electrodes are used, and a multilayer ceramic capacitor with a small equivalent series resistance can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a three-component composition diagram showing the range of main components in a non-reducible dielectric ceramic composition according to the present invention.

Claims (1)

[Claims] [Claim 1] Pb(Ni1/3 Nb2/3)O
3, the blending ratio (mol%) of Pb(Zn1/3 Nb2/3)O3 and PbTiO3 is Pb(Ni1/3 Nb2/3)O3 30.0
~85.0, Pb(Zn1/3 Nb2/3)O3
1.0-69.0, and PbTiO3
Main component within the range of 1.0-35.0 85.0-
For 99.95% by weight, the general formula is aLi2O+bRO+cB2O3+(100-a
-b-c) SiO2 (However, RO is MgO, CaO
, SrO and BaO, a, b and c are mol%), and a, b and c are respectively 0≦a<20
, 10≦b<55, 0≦c<40.