JPH0323259A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To enhance the insulation resistance, dielectric breakdown strength, etc., of 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].-z(Re(1-n)Men) O3/2 and by adding a specified amt. (expressed in terms of Ta2O5) of tantalum oxide. 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, 0.01<=n<=0.20, Re is one or more kinds of rare earth elements selected among La, Pr, Nd and Sm, and Me is one or more kinds of rare earth elements other than Re) and 0.1-10.0 pts. wt. (expressed in terms of Ta2O5) tantalum oxide as a secondary component. ZrO2 enhances dielectric breakdown strength and Ta2O5 enhances insulation resistance, dielectric breakdown strength, satisfaction Q, etc.

Description

[Detailed description of the invention] Industrial application field The present invention has high dielectric constant, insulation resistance, and dielectric breakdown voltage, greatly improves the quality Q, and has a small capacitance temperature coefficient, and is suitable for multilayer ceramic capacitors. In terms of usage, the present invention relates to a dielectric magnetic composition that can prevent a decrease in capacitance and quality Q when the thickness of internal electrodes is reduced, and 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 temperature coefficients.

・BaO Ti02-Nd20z system ・BaO-TiO2 Sm203 system Problems to be solved by the invention However, these compositions, for example, 0.09BaOO. 5
6T i 02-A dielectric material with a composition ratio of 0.35NdOs/t is used, and the internal electrode thickness of palladium is 4μ.
m, dielectric thickness 12 μm, internal electrode overlap dimension 1.
2 win XO. 7 wa, number of dielectric layers 19
When a multilayer ceramic capacitor with a multilayer structure is manufactured, the average capacitance is 742 pF, and the average quality Q is . 8700, average value of capacitance temperature coefficient: N35ppm
/°C, average value of insulation resistance: 6. OX1012Ω, average value of dielectric breakdown strength: 117 kv/Ilml, which is not a satisfactory value in terms of insulation resistance. Further, since the crystal grain size is large, 1 to 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)(+−11>(Z
r 02)III-z(Rer+-n)M
en) When expressed as 03/2 (however, x+y+z=
1. OO, 0.001≦m≦0.200, 0.01≦n
≦0.20, Re is L a + P r , N d ,
One or more rare earth elements selected from Sm, Me is selected from La.
One or more rare earth elements selected from rare earth elements excluding Pr, Nd, and Sm. ), x. Each point a.y,z represents below.
b, c. With respect to 100 parts by weight of the product having a molar ratio within the range of d, e, and f, tantalum oxide is added as a subcomponent in terms of Ta205 of 0.1 to io. The present invention proposes a dielectric porcelain assembly characterized by containing 0 parts by weight.

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, in regions C and D, the capacitance coefficient becomes too large on the negative side, making it impractical. In region E, the temperature coefficient of capacitance shifts to a positive direction, but the dielectric constant is too small to be practical.

Also, Re is La. Pr, Nd. By selecting from Sm, La. Pr. It is possible to shift the capacitance temperature coefficient in the positive direction without significantly lowering the dielectric constant in the order of Nd and Sm, and La. Pr. Nd. The capacitance temperature coefficient can be adjusted by using one type or a combination of Sm. Furthermore, La, Pr, Nd. A part of one or more rare earth elements selected from Sm, La, Pr. Substitution with one or more rare earth elements selected from rare earth elements other than Nd and Sm has the effect of significantly improving the goodness factor Q, and if the amount of substitution is less than 0.01, there is no substitution effect. ．．
When it exceeds 20, the dielectric constant decreases and becomes impractical.

In addition, by replacing Ti02 with Zr02, the dielectric constant, goodness factor Q, capacitance temperature coefficient. It has the effect of reducing the crystal grain size and increasing the dielectric breakdown strength without greatly changing the value of insulation resistance, and the substitution rate m is o. If it is less than ooi, there will be no substitution effect, while if it exceeds 0.200, the dielectric constant, goodness factor Q, and insulation resistance will decrease.

FIGS. 2(a) to (e) are graphs showing the effect of the addition of the secondary component Ta205 on the characteristics of a multilayer ceramic capacitor with respect to the main component of the composition according to the present invention, and the reason why the content range of Ta20s was limited. will be explained with reference to the graph. As shown in Figure 2, the inclusion of Ta205 improves insulation resistance and dielectric breakdown strength, increases capacitance and quality Q, and has the effect of reducing variations in capacitance and quality Q. . And, due to the inclusion of Ta205,
Insulation resistance. Although the dielectric breakdown strength is improved, if the content of Ta20s is less than 0.1 parts by weight per 100 parts by weight of the main component, the capacitance and goodness Q are low, and the capacitance and goodness Q are highly variable. Therefore, it was excluded from the scope of this invention.

On the other hand, the content of Ta205 is 1 0.0
If it exceeds parts by weight, the quality Q and insulation resistance will decrease, and the temperature coefficient of capacitance will become negative, making it impractical.

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

(Example 1) Chemically high purity BaCO3T i 02 was used as the starting material.
．． 2 r02. La203, Preo++. Nd20
3Sm203, Ce02, Gd203, Dy203, and Ta205 powders were weighed to have the composition ratio shown in Table 1 below, put into a rubber-lined pole mill equipped with an agate ball together with pure water, wet mixed, and then dehydrated and dried.

This dry powder was placed in a high alumina crucible and calcined in air at 1100° 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. In this crushed powder,
After adding an organic binder and making it homogeneous, the particles were sized through a 32-mesh sieve, and molded using a mold and hydraulic press at a molding pressure of 1 ton/cj to a diameter of 15 wa and a thickness of 0. 4+n
It was molded into m. 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.

(Left below) The thickness and diameter of the dielectric porcelain disk prepared in this manner were measured, and the sample for measuring the dielectric constant, goodness Q, and capacitance temperature coefficient was measured on both sides of the dielectric porcelain disk. A sample for measuring insulation resistance and dielectric breakdown strength was prepared by providing a 1-width portion without a silver electrode inside the outer periphery of a dielectric ceramic disk, and baking a silver electrode thereon. Then, the dielectric constant, the goodness Q,
The capacitance temperature coefficient was measured using a YHP digital LCR meter model 4275A at a measurement temperature of 20°C and a measurement voltage of 1. OVrms, +11 constant frequency #! It was determined by measurement at ilMHz. In addition, the capacitance temperature coefficient is 20℃ and 8
The capacitance at 5° C. was measured and calculated using the following formula.

TC-(C-Co)/CoX1/65X106TC: Capacitance salinity coefficient (ppm/℃) Co: Capacitance at 20℃ (pF) C: Capacitance at 85℃ (pF) Also, dielectric The rate was calculated using the following formula.

K=143.8 It was determined by measurement using an HR meter model 4329A manufactured by Co., Ltd., at a measurement voltage of 50 V.D.C., and a measurement time of 1 minute.

Then, the dielectric breakdown strength was determined by using a high voltage power supply PH835K-3 manufactured by Kikusui Electronics Co., Ltd., 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. Dielectric breakdown strength per 1++s. In addition, the crystal grain size is the optical R at a magnification of 400.
Obtained from microscopic observation.

The test results are shown in Table 2 below.

(Left below) (Example 2) Chemically high-purity BaCO3TiOz.
ZrO2. Nd20s. Using CeO2 and Ta20s powder, composition ratio 0.09BaO-0,56toni0
2-0.35[(NdO3/2)o. ss( C e
02) O. For 100 parts by weight of the main component of 051, Ta
20s is 0.0.05.0.1.0.50, 1.00,
5.00, 10.00, 12. A calcined pulverized powder containing parts by weight of OO is prepared in the same manner as in Example 1.

However, Ta205 content is 0.0.05.1 2.0
0 parts by weight is outside the scope of this invention, and 0.100,0 parts by weight is outside the scope of this invention.
．． 500, 1.00, 5.00.10.00 parts by weight are
It 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 best ML-3724 manufactured by Shoei Kagaku C Co., Ltd. was sintered so that the internal electrode thickness would be 2 um. screen print on
Dry. A green sheet is laminated on top of this, and after sintering, the internal electrode dimensions are 1. 2 w X 0.
Internal electrode palladium paste was printed by shifting the printing position so that the distance was 7 m, and after drying, one green sheet was stacked. These operations were repeated until the number of dielectric layers reached 19. Ten green sheets were laminated on this L. After sintering this laminate, the internal electrode overlap dimension is 1
．． It was cut into a multilayer ceramic capacitor having a laminated structure of 21IIll x 0.7ml and 19 dielectric layers. The cut sample was placed in an alumina pod covered with zirconia powder and heated from room temperature to 350°C in the air.
Itching was carried out for 7 hours at 5℃, and
After increasing the temperature at ℃/hr and baking at 1270℃ for 2 hours, 1
The temperature was lowered to room temperature at a rate of 00°C/hr. 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, capacitance absorption coefficient, and insulation resistance of these samples. The dielectric breakdown strength was determined by measurement under the same conditions as in Example 1. In addition, the laminated structure was confirmed by approximately 17 mm in the length and width directions of the laminated ceramic capacitor.
72 polished cross section, internal electrode overlap dimension is magnification 100,
The dielectric thickness and the internal electrode thickness were determined by optical microscope observation at a magnification of 400.

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

In addition, in the method for producing dielectric ceramic in the example, B
a CO3, T i 02, Z r 02, L
a201Pr6011. Nd203, Sm203. C
Although e02Gd203, Dy2o3 and Ta205 were used, the method is not limited to this method, and by heating in air a compound such as BaTi03, or a carbonate, a hydroxide, etc., to obtain the desired composition ratio. B
ad, TiO2, Zr02, La2
03PrsO++, NdzO:+. SIT1203
．． Cen2Gd203, Dy20:+ and T a 2
Even if one compound having a value of 0.05 is 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 the examples, rare earth elements Me other than La, Pr, Nd, and Sm include Ce, Dy. Although Gd has been described, characteristics comparable to those of the examples can be obtained even if other rare earth elements are used.

In addition to the basic composition mentioned above, SiO2Mn02, F
e203. Salts, oxides, etc., which are generally considered to be fluxes, such as ZnO, can also be added within a range that does not impair the properties.

Effects of the Invention According to the present invention, as shown in E, the crystal grain size is small and the dielectric constant. The insulation resistance and breakdown voltage are high, the quality Q is greatly improved, the temperature coefficient of capacitance is small, and when used in multilayer ceramic capacitors, the capacitance is better than that of thinner internal electrodes. The internal t
By reducing the thickness of 44i by 79, the cost of the multilayer ceramic capacitor can be reduced by 1, and the occurrence of delamination, which is an internal structural defect, can be prevented. In addition, because the dielectric breakdown voltage is high, the thickness of the dielectric layer has been reduced7, and the element body has been made smaller. Larger capacity is possible.

[Brief explanation of the drawing]

Figure 1 is a ternary diagram explaining the illumination range of the main components of the composition according to the present invention, and Figures 2 (a) to (e) are composition ratios of 0.09BaO-0.56T i O20 according to the present invention. ．．
3 5 [ (N d 03/2) 0.95 (C
e 02) The effect of the addition of Ta205 as a subcomponent to 100 parts by weight of the main component of 0.051 is calculated using the dielectric thickness of 12 μm.
, is a graph showing the electrical characteristics of a multilayer ceramic capacitor having a multilayer structure in which internal electrode dimensions + 1.2 llw IX 0.7 m and number of dielectric layers = 1!1.

Claims (1)

[Claims] General formula xBaO-y[(TiO_2)_(_1_-_m_)(
ZrO_2)_m]-z(Re_(_1_-_n_)M
e_n) When expressed as O_3_/_2 (however, x+y+
z=1.00,0.001≦m≦0.200,0.01
≦n≦0.20, Re is one or more rare earth elements selected from La, Pr, Nd, Sm, Me is La, Pr, Nd
, one or more rare earth elements selected from rare earth elements excluding Sm. ), x, y, z are the points a, b, c, d represented below
, e, f consisting of a range of molar ratios
Based on the weight part, tantalum oxide is added as a subcomponent to Ta_2
A dielectric ceramic composition containing 0.1 to 10.0 parts by weight calculated as O_5. ▲Contains mathematical formulas, chemical formulas, tables, etc.▼