JPH0323257A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To enhance the insulation resistance, dielectric breakdown strength, etc., the title compsn. by specifying x, y and z when the principal component is represented by a general formula xBaO.Y[ (TiO2)(1-m)(ZrO2)m].zRe2O3 and by adding a specified amt. of two or more among Nb2O5, Ta2O5 and V2O5. CONSTITUTION:This dielectric porcelain compsn. contains 100 pts. wt. principal component represented by the above-mentioned general formula (where x, y and z show a molar ratio within the ranges each defined by points a-f in the table, x+y+z=1.00, 0.001<=m<=0.200 and Re2O3 is one or more kinds of oxides of rare earth elements selected among La2O3, Pr2O3, Nd2O3 and Sm2O3) and 0.001-0.010 pt. mol, in total, of two or more among Nb2O5, Ta3O5 and V2O5 as secondary components. ZrO2 enhances dielectric breakdown strength. Nb2O5, Ta2O5 and V2O5 enhances insulation resistance and dielectric breakdown strength.

Description

[Detailed Description of the Invention] Industrial Application The present invention has high dielectric constant, insulation resistance, and dielectric breakdown voltage, excellent quality Q, and small temperature coefficient of capacitance, and is suitable for use in multilayer ceramic capacitors. prevents the decrease in capacitance and quality Q when the thickness of the internal electrode is reduced,
The present invention relates to a dielectric magnetic composition that can reduce variations in capacitance and quality Q.

Conventional technology Conventionally, the dielectric constant and insulation resistance are high, and the quality Q is excellent.
The following systems are known as dielectric magnetic compositions with small capacitance wideness coefficients.

・BaO-Ti 02-Nd203 series ・BaO-Ti
Problems to be solved by the 02-Sm203 series invention However, these group precepts, for example, 0.11BaOO. 6
A dielectric material with a composition ratio of 8T i 02 -0.21NdtO3 was used, and the palladium internal electrode thickness was 4μ.
m, dielectric thickness 12 μm, internal electrode overlap dimension 1.
2 wa X 0. 7. When a multilayer ceramic capacitor with a laminated structure with 19 dielectric layers is manufactured, the average value of capacitance: 742 pF, and the average value of quality Q:
8700, average value of capacitance temperature coefficient: N35ppm/
°C, average value of insulation resistance: 6. OX1012Ω, average value of dielectric breakdown strength: 117 kv/rfa, which is not a satisfactory value in terms of insulation resistance. In addition, the crystal grain size is l~
Since it is as large as 5 μm, the porosity in the element body becomes large, and the electric field strength applied to each crystal grain becomes large, and the dielectric breakdown strength is also not a satisfactory value.

Furthermore, in order to reduce the cost of multilayer ceramic capacitors and to prevent the occurrence of delamination, which is a structural defect inside the element body, the thickness of the palladium internal electrode was increased by 4.
When thinning from μm to 2 μm, a dielectric material with the above composition ratio is used, the dielectric thickness is the above, the internal electrode overlap dimension is
The average value of capacitance of a multilayer ceramic capacitor having a laminated structure with a number of dielectric layers is as small as 610 pF, and the variation in capacitance is large as 256 to 713 pF. Furthermore, there was a problem in that the average value of the quality level Q was as low as 4,000, and the variation in the quality level Q was large, ranging from 600 to 8,800.

Means for Solving the Problems In order to solve these problems, the present invention provides the general formula x B
a O − y[(T i 02)(+−111(
Z r 02) When expressed as IIIzRe203 (x+y+z=1.00, 0.001≦m≦0.200
．． Re203 is La20co. P r2o11/3
T An oxide of one or more rare earth elements selected from Nd203 and Sm203. ), x. y. Nb20s rTa20s+V2 as a subcomponent to 100 parts by weight of the main component consisting of the molar ratio range surrounded by each point a r b + C, d + e, f where z is expressed below.
Two or more types selected from 0S, total 0.001 to 0.0
The present invention proposes a dielectric ceramic composition characterized by containing 10 mole parts.

FIG. 1 is a ternary diagram showing the composition range of the main components of the composition according to the present invention, and the reason for limiting the composition range of the main components will be explained with reference to FIG. That is, sintering is extremely difficult in region A. Furthermore, in region B, the quality Q decreases, making it impractical. Furthermore, C. D(; In the J region, the capacitance temperature coefficient becomes too large to be negative, making it impractical.

In the E region, the capacitance temperature coefficient shifts to the positive direction, but the dielectric constant is too small to be practical.
e203 to La203. P xo+ws. Nd203.
By selecting from Sm20s, La203. P r2
0x/s+ It is possible to shift the capacitance temperature coefficient in the positive direction without significantly lowering the dielectric constant in the order of Nd203, Sm203, and La203. P r20+
+i3. Nd203. The temperature coefficient of capacitance can be adjusted by one type or combination of SmzOz.

In addition, by replacing TiO2 with ZrO2, the effect of reducing the crystal grain size and increasing the dielectric breakdown strength can be achieved without significantly changing the values of dielectric constant, quality Q, temperature coefficient of capacitance, and insulation resistance. and its substitution rate m is 0.001
If it is less than 0.200, there will be no substitution effect, while if it exceeds 0.200, the dielectric constant, quality Q, and insulation resistance will decrease.

FIGS. 2(a) to (e) are graphs showing the effect of the addition of subcomponents Nb20B, Ta20s, and V2OS on the characteristics of a multilayer ceramic capacitor with respect to the main components of the composition according to the present invention. The reason for limiting the contained dry range will be explained with reference to the graph. Second
As shown in the figure, Nb20a, Ta20s. By containing v2o5, insulation resistance and dielectric breakdown strength are improved,
It also has the effect of increasing the capacitance and quality Q and reducing variations in capacitance and quality Q. And Nb20
B, Ta20B. The inclusion of V20S improves insulation resistance and dielectric breakdown strength, but Nb20S. Ta20s+
The total content of V205 is based on 100 parts by weight of the main component,
If it is less than 0.001 mole part, the dielectric breakdown strength is not so high, the capacitance and the quality Q are low, and the variation in the capacitance and the quality Q is large, so it is excluded from the scope of this invention. On the other hand, if the total content of Nb20s, Tazos, and V205 exceeds 0.01 mole part with respect to the main components, the quality Q and insulation resistance will decrease, and the capacitance temperature coefficient will become negative, making it impractical for practical use. It will no longer be.

Also, Nb20s. Ta20s. By containing two or more selected from V205, Nb20s, Ta20
Compared to those containing one selected from s+ V201+, the dielectric constant, insulation resistance, and dielectric breakdown voltage are higher, and the quality level Q is higher.
The capacitance temperature coefficient can be reduced.

Example The present invention will be explained below using specific examples.

(Example 1) Chemically high purity BaCO3T i O2 was used as the starting material.
, Z r 02, L a203, P r6011. Nd
203. Sm20z. Nb20s, Ta20s. and v2o5 powder were weighed so as to have the composition ratio shown in Table 1 below, put into a rubber-lined ball mill equipped with agate balls together with pure water, wet mixed, and then dehydrated and dried. This dry powder was placed in a high alumina crucible and exposed to air for 11 hours.
It was calcined at 00°C for 2 hours. This calcined powder was put into a rubber-lined ball mill equipped with agate balls together with pure water, wet-pulverized, and then dehydrated and dried. An organic binder was added to this pulverized powder to make it homogeneous, and then the powder was sized through a 32 mesh sieve and molded into a diameter of 15 m and a thickness of 0.4 m using a mold and a hydraulic press at a molding pressure of 1 ton/unit. Next, the molded disk was placed in an alumina pod covered with zirconia powder and fired in air at the temperature shown in Table 1 below for 2 hours to obtain dielectric porcelain having the composition ratio shown in Table 1. Ta.

(Margin below) The thickness and diameter of the dielectric porcelain disk thus obtained were measured, and the dielectric constant, goodness Q, and capacitance temperature coefficient measurement samples were measured using the dielectric porcelain disk. A silver electrode was baked on the entire surface of both sides, and a sample for measuring insulation resistance and dielectric breakdown strength was prepared by providing a part with no silver electrode on the inside of the outer periphery of a dielectric ceramic disk with a width of 1-, and baking a silver electrode on it. The dielectric constant, goodness Q, and capacitance temperature coefficient were measured using YHPtf. digital LCR meter model 4275A at a measurement temperature of 20°C.
1 constant voltage 1. OVrms. It was determined by measurement at a constant frequency of 11 MHz. In addition, the capacitance temperature coefficient is 20℃
The capacitance at 85° C. was measured and calculated using the following formula.

TC= (C-Co)/CoX1/65X10'TC:
Temperature coefficient of capacitance (ppm/°C) Co: Capacitance at 20°C (pF) C: Capacitance at 85°C (pF) Further, the dielectric constant was determined from the following formula.

K=143.8XCoXt/D! K: Dielectric constant Co: Capacitance at 20°C (pF) D: Diameter of dielectric porcelain (llII1〉t: Thickness of dielectric porcelain (m) Furthermore, the insulation resistance is measured using YHP HR meter model 4.
329A, measuring voltage 50V. D. C. , was determined from measurements over a measurement time of 1 minute.

The dielectric breakdown strength was determined by using a high-voltage power supply PH335K-3 type manufactured by Kikusui Electronics Corporation, placing the sample in silicone oil, and dividing the dielectric breakdown voltage determined by a voltage increase rate of 50 V/sec by the dielectric thickness. It was defined as dielectric breakdown strength per 1lIll. Further, the crystal grain size was determined by optical microscope observation at a magnification of 400.

The test results are shown in Table 2 below.

(Left below) (Example 2) Chemically high purity BaCO3TiO2.Z was used as the starting material.
r02. NdxO3. NbgOs, Ta2es and v
205 powder was used, and the main component was 0.11BaO1O. 68
T i 02-0.2 100 parts by weight of 1Nd20z, [(Nb20s)o. 4(Ta2es) o. s
(V205)0.3] to 0, 0.0001, 0.001
A calcined pulverized powder containing 0.0, 0.0100.0.0200 mol parts is prepared in the same manner as in Example 1. however,((
Nb20s) o. 4(Ta2OS)0.3(V2
OS) 0.3 1 content is 0,0.000 1,0.0
200 molar parts are outside the range of this invention, and 0.001
0.0100 mole part is within the scope of this invention.

An organic binder, plasticizer, dispersant, and organic solvent were added to this calcined and pulverized powder and mixed in a pot equipped with alumina balls to prepare a slurry. After mixing, the filtered slurry was processed into a green sheet having a dielectric thickness of 12 μm after sintering. Ten such green sheets were stacked on a support stand, and internal electrode palladium paste ML-3724 manufactured by Shoei Chemical Co., Ltd. was screen printed so that the internal electrode thickness after sintering would be 2 μm, and dried. A green sheet was laminated on top of this, and internal electrode palladium paste was printed by shifting the printing position so that the internal electrode overlap dimensions after sintering were 1.2 m x 0.7 m, and dried. After that, one green sheet was laminated. These operations were repeated until the number of dielectric layers reached 19. On top of this, ten green sheets were laminated. After sintering this laminated body, , internal electrode overlap dimension is 1.2 wm
X 0. It was cut into a multilayer ceramic capacitor having a multilayer structure with 7 wxa and 19 dielectric layers. The cut sample was placed in an alumina pod covered with zirconia powder, heated in air from room temperature to 350°C at a rate of 5°C/hr, and from 350°C to 100°C/hr.
After baking at 1270℃ for 2 hours, 100℃/hr
The temperature was lowered to room temperature. Next, the sample surface of the fired sample is polished to fully expose the internal electrode part that will be connected to the external electrode, and a silver external electrode is baked on the exposed part of the internal electrode to make it conductive with the internal electrode, producing a multilayer ceramic capacitor. did.

The capacitance, quality Q, temperature coefficient of capacitance, insulation resistance, and dielectric breakdown strength of these samples were determined by measurements under the same conditions as in Example 1. In addition, confirming the laminated structure is approximately 1/2 of the length and width of the laminated ceramic capacitor.
The polished cross section of the internal electrode overlap dimension was determined by optical microscope observation at a magnification of 100, and the dielectric thickness and internal electrode thickness at a magnification of 400.

The measurement results are shown in FIGS. 2(a) to (e).

In addition, in the method for manufacturing dielectric ceramic in the example, B
a CO3. T i 02. Z r 02. L
a203P zO++. Nd203. Smz(h.N
b20s. Ta205. and V205 were used, but
The method is not limited to this method, but by heating in air a compound such as BaTi03, carbonate, hydroxide, etc. to obtain a desired composition ratio.
T i 02. Z r o2. L a203,P
reo++. Nd203, SmzOa, Nb20s, T
a2es. Even if compounds of v2o5 and v2o5 are used, properties comparable to those of the examples can be obtained.

Further, even if the main component is calcined in advance and the subcomponents are added, properties comparable to those of the examples can be obtained.

In addition to the above-mentioned main components and subcomponents, Si02. M
n 02. Salts, oxides, etc. that are generally considered to be fluxes, such as Feto3 and ZnO, can also be added within a range that does not impair the properties.

Effects of the Invention As described above, according to the present invention, the crystal grain size is small, the dielectric constant, insulation resistance, and dielectric breakdown voltage are high, the quality factor Q is excellent, the capacitance salinity coefficient is small, and a multilayer ceramic capacitor is manufactured. In applications, it is possible to prevent a decrease in capacitance and quality Q when the thickness of the internal electrode is made thinner, and to reduce variations in capacitance and quality Q. The cost of multilayer ceramic capacitors can be reduced, and delamination, which is an internal structural defect, can be prevented from occurring. Furthermore, since the dielectric breakdown voltage is high, the thickness of the dielectric layer can be made thinner, and the element body can be made smaller and larger in capacity.

[Brief explanation of the drawing]

FIG. 1 is a ternary diagram explaining the composition range of the main components of the composition according to the present invention, and FIGS. (TiO2)0
．． 9(Z.rOt)o. + 1-0.21Nd20
Subcomponent [(N b
xos) 0.4 (T axos) 0.3 (V20
s) 0.3], dielectric thickness = 12 μm,
Internal electrode overlap dimension = 1.2wa x 0. 7 m
, is a graph showing the electrical characteristics of a multilayer ceramic capacitor having a multilayer structure with the number of dielectric layers: 19.

Claims (1)

[Claims] General formula xBaO-y[(TiO_2)_(_1_-_m_)(
ZrO_2)_m]-zRe_2O_3 (where x+y+z=1.00, 0.001≦m≦0.2
00, Re_2O_3 is La_2O_3, Pr_2O_
1_1_/_3, Nd_2O_3, Sm_2O_3 oxide of one or more rare earth elements. ), x, y,
Nb_2O_5, Ta_2O_5, V_2O_ as subcomponents to 100 parts by weight of the main component consisting of a range of molar ratios where z is surrounded by each point a, b, c, d, e, f shown below.
5, two or more types selected from 0.001 to 0.0 in total
A dielectric ceramic composition characterized in that it contains 10 mole parts. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼