JP2002037667A - Dielectric ceramic composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonreducing dielectric ceramic composition that, as its electrical characteristics, satisfies NPO characteristics, which is specified in the EIA standard, within ±3% of a temperature-changing ratio of electric capacity over such a wide temperature range as -55 deg.C to +125 deg.C, has a specific dielectric constant of >=200, and has the tan δ of <=0.01, which can be sintered at a low temperature of <=1,300 deg.C in a reducing atmosphere of 1% H2-99% N2, and in which inexpensive Ni can be used as an internal electrode. SOLUTION: The composition has a core-shell structure in which crystal grains contain at least two components, or the composition is composed of a composite which contains at least two components. The composition is a reduction-resistant dielectric ceramic composition in which each of the above two components has a temperature characteristic of a dielectric constant having a sign opposite to each other, which has a specific dielectric constant of >=200, has the tan δ of <=0.01, and can be sintered at <=1,300 deg.C. A preferable embodiment is as follows: one of the above two components is BaTiO3-based dielectric ceramic composition, which contains BaTiO3 as a main component and Cr2O7, Fe2O3, or MnO as an additive, and the other of the above two components is (Ca, Sr) (Ti, Zr)-based dielectric ceramic composition to which SiO2 is added.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reduction-resistant dielectric which is mainly used for a high dielectric constant type ceramic porcelain composition and a temperature-compensated dielectric porcelain composition and which is fired simultaneously with an internal electrode material composed of a base metal. It relates to a porcelain composition.

[0002]

2. Description of the Related Art In recent years, the miniaturization, price reduction and high functioning of electronic equipment have been rapidly progressing, and it has been desired to reduce the size and cost of electronic components such as multilayer ceramic capacitors and filters used therein. ing. For miniaturization and high functionality, it is necessary that the dielectric constant is high, tanδ is low, and the temperature dependence of the capacitance is low. To reduce the cost, expensive Pt, Au, Pd, Alternatively, it is effective to use an inexpensive base metal from Pd-Ag as the internal electrode. But,
Since a base metal such as Ni is easily oxidized when sintered in an acidic atmosphere, firing in a reducing atmosphere is necessary, and ceramic itself co-fired with an internal electrode also needs to have reduction resistance. JP-A-5-78166 discloses such a material. However, there is no material that does not contain Bi or Pb compounds that are harmful to the environment, and also has a high dielectric constant of 200 or more and a low dielectric constant that satisfies NPO characteristics.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and an object of the present invention is to provide a high dielectric constant, which does not contain Bi and Pb which are harmful to the environment, and has high electrical permittivity. An object of the present invention is to provide a dielectric ceramic composition which satisfies a low dielectric loss tan δ and the NPO characteristics and can use inexpensive Ni as an internal electrode. Specifically, an object of the present invention is to achieve a dielectric constant of 200 or more and a dielectric loss
nδ is 0.01 or less, and 130% in a reducing atmosphere of 1% H ₂ -99% N ₂
An object of the present invention is to obtain a non-reducing dielectric ceramic composition that can be sintered at a temperature as low as 0 ° C. or less.

[0004]

According to the present invention, there is provided a dielectric ceramic composition having a core-shell structure in which crystal grains have at least two components, wherein the two components have dielectric constants opposite to each other. It has a temperature characteristic of In the dielectric porcelain composition, the crystal grains have a double structure of a core (core) portion composed of one component and a shell portion composed of the other component different from the one component. This structure is called a core-shell structure. The present inventor has found that the above-mentioned object can be achieved by selecting components having temperature characteristics of opposite signs to each other forming the core-shell structure.
Ceramics composed of these two components have a high relative dielectric constant and a low dielectric loss, and can be sintered at a low temperature in a reducing atmosphere, but have poor temperature characteristics. However, since these two components have temperature characteristics of opposite signs to each other, they compensate each other while maintaining a high relative dielectric constant and the like, so that good temperature characteristics can be obtained.

In another embodiment of the dielectric ceramic composition according to the present invention, instead of having a core-shell structure, the dielectric ceramic composition is a composite having at least two components which do not react with each other, It is characterized in that these two components consist of a composite having temperature characteristics of opposite signs. As in the above-described manner, the two components have temperature characteristics of opposite signs to each other, thereby compensating for the temperature characteristics.

The two components of the dielectric porcelain composition according to the present invention are, for example, BaTiO ₃ -based ceramics containing Cr ₂ O ₃ , Fe ₂ O ₃ or MnO as an additive, and SiO ₂ or the like as the other component. (Ca, Sr) (Ti, Zr) O ₃ -based ceramics containing the above glass as an additive is preferable. The one component, BaTiO ₃ ceramics, has, for example, a relative dielectric constant of 1000 and a temperature characteristic of a dielectric constant of +.
The other component (Ca, Sr) (Ti, Zr) O ₃ -based ceramics has a relative dielectric constant of 200 and a temperature characteristic of a dielectric constant of −2, for example, 2000 ppm / ° C., a dielectric loss tan δ of 0.01 or less, and the other component.
000 ppm / ° C. and dielectric loss tan δ is 0.01 or less. Since the temperature characteristics of these two components have opposite signs, the temperature change rate of the capacitance, that is, the temperature change rate of the relative permittivity is flat within ± 0.3% while maintaining a high relative permittivity. Properties can be obtained.

[0007] The present inventors have found that N-free harmful Bi and Pb
The objective is to obtain a reduction-resistant dielectric porcelain composition having a relative dielectric constant of 200 or more, a dielectric loss tan δ of 0.01 or less, and a low-temperature sintering of 1300 ° C or less in a reducing atmosphere, while satisfying PO characteristics. As a result of research, it has been found that the dielectric of the present invention achieves this goal as described above.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing a dielectric porcelain composition according to the present invention will be described, and the electrical characteristics of the dielectric porcelain composition produced by the production method will be described based on theoretical values. Embodiments of the present invention will be described in detail with reference to the drawings.

One preferred embodiment of the present invention is a dielectric ceramic composition used for a single-plate type ceramic capacitor.

[0010] The dielectric ceramic composition according to the present invention is prepared as follows. One component (called component a)
The relative dielectric constant is 800, and the temperature characteristic of the dielectric constant is +15.
It has characteristics of 00 ppm / ° C and dielectric loss tanδ of 0.01.
B containing ₂ mol% of Cr ₂ O ₃ as an additive to BaTiO _{3 as the} main component
and ATiO ₃ based ceramic, as the other component (referred to as component b), the dielectric constant is 220, the temperature characteristics of dielectric constant -182
0ppm / ℃, dielectric loss tanδ has the property of 0.0001,
(Ca0.297, Sr0.693) (Ti0.97, Zr0.03) O ₃ -x ceramics are each 1300 ° C. so as not to react with each other.
It is calcined at the above high temperature. These are wet-mixed for a short time using yttria-stabilized zirconia balls using water as a solvent, and then dried. The resulting mixed powder is granulated by adding PVA as an organic binder. Using the powder thus prepared, a press molding machine is used to apply a surface pressure of 3 to.
After uniaxial pressure molding of a disk-shaped sample with a size of 16.5 mmΦ and a thickness of 0.7 mm at n / cm2, liquid phase sintering in a reducing atmosphere of 1% H ₂ -99% N ₂ at 1300 ° C or less for 2 hours To obtain a core-shell structure or a composite. After firing, a silver paste is applied to both surfaces of the ceramic sintered body and baked at 750 ° C. in the air to form external electrodes.

FIG. 1 shows the relative dielectric constant and the temperature characteristic of the dielectric constant in the case of a single-plate capacitor of a sintered body having a core-shell structure or a composite formed as described above. It is a theoretical value expressed as a ratio of two components (Vb / (Va + Vb)).

[0012] These theoretical values were obtained by the following two equations. log k = (Va x logka + Vb x logkb) / (Va + Vb) (1) Tcc = Va x Tcca + Vb x Tccb (2) where k and Tcc have a core-shell structure composed of two components or The relative dielectric constant of the porcelain composition, which is a composite, and the temperature dependence of the relative dielectric constant (ppm / ° C.), where Va and Vb are the volume fractions of components a and b, respectively, and ka and kb are the components a and b, respectively
, And Tcca and Tccb represent the temperature dependence (ppm / ° C.) of the relative permittivity of the components a and b, respectively. From this figure, when the two components form a complex without reacting with each other or have a core-shell structure, the temperature dependence of the relative permittivity is 0 ppm / ° C.
It has been found that the relative dielectric constant has a high value of 400 or more at a mixing ratio of

Another preferred embodiment of the present invention is a dielectric ceramic composition used for a multilayer ceramic capacitor.

In the same manner as described above, the two-component ceramics are wet-mixed, and PVA as an organic binder is added to the obtained mixed powder, and the mixture is wet-mixed to adjust the ceramic slip. This ceramic
The slip is formed into a sheet by the doctor blade method,
A rectangular green sheet having a thickness of 21 μm is obtained. Next, a conductive paste of Ni is printed on the ceramic green sheets to form internal electrodes. A plurality of the ceramic green sheets on which the internal electrodes are formed are stacked so that the side from which the conductive paste layer is drawn out is alternately formed to obtain a laminate. The above laminate is heated at 1300 ° C. or lower for 2
Firing in a reducing atmosphere of 1% H ₂ -99% N ₂ for a time. After firing, a silver paste is applied to both sides of the ceramic sintered body and baked at 750 ° C. in the air to form external electrodes electrically connected to the internal electrodes.

The external dimensions of the multilayer ceramic capacitor obtained as described above are 3.2 mm in width and 1.6 m in length.
m, thickness 0.5 mm. Further, the thickness of each dielectric ceramic layer interposed between the internal electrodes is 10 μm,
The total number of effective dielectric ceramic layers is five. The characteristics of the dielectric ceramic composition thus obtained are as follows.
Sintering at 150 to 1300 ° C. for 2 hours is sufficient, and a high relative dielectric constant and good temperature characteristics similar to those of a single-plate ceramic capacitor can be obtained.

As described above, the present invention provides a monolithic ceramic capacitor having a good relative dielectric constant of 200 or more and a dielectric loss tan δ of 0.01 or less without containing Bi and Pb which are harmful to the environment. At a low sintering temperature of 1150 ° C to 1300 ° C.

[Brief description of the drawings]

FIG. 1 is a graph showing the relative permittivity and temperature characteristics of permittivity,
The abscissa is a theoretical value expressed as a ratio (Vb / (Va + Vb)) of these two components.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01G 4/12 415 H01P 7/10 H01P 7/10 C04B 35/00 J F term (Reference) 4G030 AA08 AA09 AA10 AA16 AA17 BA09 CA05 GA09 GA18 4G031 AA04 AA05 AA06 AA11 AA12 BA09 CA05 GA02 GA05 5E001 AB01 AB03 AC09 AE00 AE01 AE02 AE03 AE04 AF06 AH05 AH09 AJ02 5G303 AA01 AB06 AB07 AB11 AB20 CB13 CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB CB

Claims (4)

[Claims] 1. A dielectric ceramic composition having a core-shell structure in which crystal grains have at least two components, wherein said two components have temperature characteristics of dielectric constants having opposite signs to each other. object. 2. A dielectric porcelain composition comprising a composite having at least two components, wherein the two components have temperature characteristics of dielectric constants of opposite signs to each other. 3. One of the two components is BaTiO._Three
With Cr as the main component_TwoO _Three, Fe_TwoO_ThreeOr BaTi with MnO added
O_ThreeSystem ceramics and the other component is SiO_TwoWas added
(Ca, Sr) (Ti, Zr) O_ThreeCharacterized by being a ceramic
The dielectric ceramic composition according to claim 1. 4. The dielectric ceramic composition according to claim 1, wherein each of the two components has a relative dielectric constant of 200 or more.