JPH02267165A - dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain dielectric porcelain composition having high dielectric constant and small crystal grain size by preparing a composition using specific ratio of BaO, TiO2 and CeO2. CONSTITUTION:A dielectric porcelain composition is prepared from raw materials composed of a range of the molar ratio surrounded by every points of a, b, c and d expressed with x, y and z in the table for general formula xBaO-yTiO2-zCeO2 (x+y+z=1.00). By said method, a composition having high dielectric constant exhibiting temperature characteristic of electrostatic capacity satisfying Y-class F-characteristic of JIS standard is obtained and crystal grain size is able to be about 5-10mu, then thickness of dielectric is able to be thin, thus a product is able to have small size and large capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dielectric ceramic composition having a high dielectric constant whose capacitance-temperature characteristics satisfy the JIS Y class F characteristic standard and a small crystal grain size. It is.

Conventional technology As a dielectric ceramic composition having a high dielectric constant,
It is known that a suitable amount of BaO, CaO, T i 02°zr02, etc. is added to BaTiOs.

Problems to be Solved by the Invention However, these dielectric ceramic compositions have crystal grain sizes of 10 to 10.
Because it is large at 20 μm and has a high porosity, it is suitable for application to products with thin dielectrics such as multilayer ceramic capacitors, which have low dielectric breakdown voltage and low dielectric breakdown voltage and insulation resistance during plating processing to form external electrodes. There were issues such as a decline in

Means for Solving the Problems In order to solve these problems, the present invention provides a formula xBa
When expressed as o-yT 1o2-zce02, (however,
x+y+z=1. The present invention provides a dielectric ceramic composition characterized in that x, y, and z are in a molar ratio range surrounded by points a, b, c, and d shown below.

FIG. 1 is a ternary diagram showing the composition range of the composition according to the present invention, and the reason for limiting the composition range will be explained with reference to FIG. First, the dielectric constant in region A is small, making it impractical. Further, in region B, the rate of change of the capacitance temperature characteristic becomes too large on the positive side, and the JIS Y and IF characteristic standards are not satisfied, making it impractical. Furthermore, sintering is extremely difficult in the C region. Furthermore, in region D, the rate of change in capacitance temperature characteristics becomes too large on the positive side, and J
It does not satisfy the IS Y class F characteristic standard and is not practical.

According to the configuration of the present invention related to the above composition system 1 composition range, the capacitance temperature characteristics exhibit a high dielectric constant that satisfies the JIS Y class F characteristic standard, and the crystal grain size is 5 to 10 μm. As a result, the dielectric thickness can be reduced, making it possible to miniaturize products and increase capacity.

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

As starting materials, chemically high-purity Ba C0aTi○2 and Ce○2 powders were weighed so as to have the composition ratio shown in Table 1 below, and put into a rubber-lined ball mill equipped with agate balls together with pure water. After wet mixing, the mixture was 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, it was sized through a 32-mesh sieve, and molded using a mold and hydraulic press at a molding pressure of 1 ton/cd to a diameter of 15 mm and a thickness of 0.4 mm.
It was molded into. Next, this molded disk was placed in an alumina pod covered with zirconia powder, and the following first step was carried out in the air.
Dielectric ceramics having the composition ratios shown in the table were obtained.

The thickness and diameter of the dielectric porcelain disk obtained in this way were measured, and the samples for measuring permittivity, dielectric loss, and capacitance temperature characteristics were prepared by baking silver electrodes on both sides of the dielectric porcelain disk. Ta. The dielectric constant, dielectric loss, and capacitance temperature characteristics are
Y HP digital LCR meter model 4274A
was used, the measurement temperature was 20°C, and the measurement voltage was 1. OVrms,
It was determined by measurement at a measurement frequency of IKHz.

Further, the dielectric constant was determined from the following formula.

K=143.8XCoXT/D2 K: Dielectric constant Co: Capacitance at 20°C (pF) D: Diameter of dielectric ceramic (mm) t: Thickness of dielectric ceramic (mm) Furthermore, the crystal grain size is It was determined by optical microscope observation at a magnification of 400. The test conditions and test results are also shown in Table 1 below.

In addition, in the method for manufacturing dielectric ceramic in the example, Ba
Although CO3, TiO2 and CeO2 are used, the method is not limited to this method, and compounds such as BaTiOs, carbonates, hydroxides, etc. can be heated in air to obtain the desired composition ratio. Even when using compounds that become TiO2 and CeO2, 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.

Effects of the Invention As described above, according to the present invention, the capacitance temperature characteristic is JI
It has a high dielectric constant that satisfies the Y-class F characteristic specifications of S, and the small crystal grain size allows the dielectric thickness to be reduced, allowing for smaller products and larger capacity.

[Brief explanation of drawings]

FIG. 1 is a ternary diagram showing the composition range of the dielectric ceramic composition according to the present invention.

Claims (1)

[Claims] When expressed as the general formula xBaO-yTiO_2-zCeO_2,
(However, x+y+z=1.00) A dielectric ceramic composition characterized in that x, y, and z are in a molar ratio range surrounded by points a, b, c, and d shown below.