JPH0451408A - Dielectric porcelain composite - Google Patents

Abstract

PURPOSE:To enhance dielectric constant, dielectric breakdown voltage and insulation resistance, and reduce a crystal grain diameter size to reduce dielectric substance thickness by having specific pts.wt. of Nb2O5 and MnO2 contained in 100 pts.wt. of a main component constituted within a mole ratio in a specific formula wherein (x), (y), and (z) are enclosed by points (a), (b), (c), and (d). CONSTITUTION:In 100 pts.wt. of a main component constituted within a mole ratio wherein (x), (y), and (z) are enclosed by points (a), (b), (c), and (d), as shown in the Table 1 when a general formula is expressed as xBaO-yTiO2-zCeO2 (where x+y+z=1.00), 0.3-3.0 pts.wt. of Nb2O5 and 0.05-0.25 pts.wt. of MnO2 are contained. For example, powder of high purity of BaCO3, TiO2, CeO2, Nb2O5 and MnO2 is weighed, put in a ball mill with pure water, wet-blended, dehydrated and dried. It is put in a high-alumina crucible to be calcined in the atomophere. It is put in a ball mill with pure water, wet-milled, dehydrated and dried. An organic binder is added for homogenizing and grading process is performed through a screen. A metal mold and hydraulic press are used for forming. It is put in an alumina sheath where zirconium power is laid on to obtain dielectric porcelain.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a dielectric ceramic composition having a high dielectric constant, high dielectric breakdown voltage and high insulation resistance, and small crystal grain size.

BACKGROUND ART Conventionally, as a dielectric ceramic composition having a high dielectric constant, BaTiO3 is combined with Bad, Cab, TiO2, and Zr.
It is known that a suitable amount of 0z or the like is added.

Problems to be Solved by the Invention However, these dielectric ceramic compositions have crystal grain sizes of 10 to 10.
Since 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 solves the problems when expressed as the general formula x BaO-y Tie□-z CeO□ (
However, χ+y+z=1. OO), x, y,
For 100 parts by weight of the main component, where z consists of the molar ratio range surrounded by each point a, b, c, d shown below,
The present invention provides a dielectric ceramic composition characterized in that it contains 0.3 to 3.0 parts by weight of Nb2O5 (!: 0.05 to 0.25 parts by weight of MnO□).

FIG. 1 is a ternary diagram showing the composition range of the main components 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. In addition, in the B region, the Curie point becomes too large on the negative side, and the capacitance change rate of the temperature characteristic greatly deviates to the positive side, making it impractical.Furthermore, in the C region, sintering is extremely difficult. Further, in the D region, the dielectric constant is small, making it impractical.

According to the composition system and composition range of the present invention, by containing Nb and O in the main components,
It has the effect of improving the product of capacitance and insulation resistance (CR product) and dielectric breakdown voltage, but its content is
If the content is less than 0.3 parts by weight, there will be no effect, while if it exceeds 3.0 parts by weight, the Curie point will shift to the negative side and the dielectric constant will decrease. Also, for the main component, M
Containing nO□ has the effect of increasing the CR product, but if the content is less than 0.05 parts by weight or more than 0.25 parts by weight based on 100 parts by weight of the main component, the CR product increases. decreases. Furthermore, the dielectric ceramic composition of the present invention can have a crystal grain size of 5 to 10 μm.

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

First, the starting material is chemically highly purified BaC0,3Ti.
Oz, Ce0z, NbzOs, and Mn0z powders were weighed to have the composition ratios shown in Table 1 below, placed in a rubber-lined ball mill equipped with agate balls together with pure water, wet mixed, and then dehydrated and dried. Next, this dry powder was placed in a high alumina crucible and heated to 1100°C in air.
It was calcined for 2 hours. Next, 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. Next, an organic binder was added to the pulverized powder to make it homogeneous, and then the particles were sized through a 32-mesh sieve, and the molding pressure was 1 t using a mold and a hydraulic press.

It was molded to a diameter of 15 mm and a thickness of 0.4 mm at n/ca. Next, this molded disk was placed in an alumina sheath covered with zirconia powder, and dielectric porcelain having the composition ratio shown in Table 1 below was obtained in air.

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. For the samples for measuring dielectric breakdown voltage and insulation resistance, a silver electrode was baked to a depth of 1 mm inside the outer periphery of a dielectric ceramic disk. The dielectric constant, dielectric loss, and capacitance temperature characteristics are
Digital L CR manufactured by Yokogawa Hurent Vano Card ■
Measured temperature 20° using meter model 4274 A.
C3 measurement voltage 1. OVrms was determined by measurement at a measurement frequency of 1 kHz. In addition, the dielectric breakdown voltage is determined by Kikusui Electronics Co., Ltd.
It was determined from measurements using a high-voltage DC power supply made by Manufacturer. Furthermore, the insulation resistance was determined by measurement using a high resistance meter manufactured by Kukeda Riken Kogyo ■.

Then, the dielectric constant was calculated from the following formula.

K = 143.8X Co n+m) Furthermore, the dielectric breakdown voltage was determined from the following formula.

B1=BO/l B1: Breakdown voltage (kv/mm) BO: Breakdown voltage (kv) Furthermore, the insulation resistance was determined as a CR product using the following formula.

CR=Co The test conditions and test results are also shown in Table 1 below.

(Left below) In addition, in the method for producing dielectric ceramic in the example, Ba
Although C0z, TiO2, Ce0z, Nb2o5, and MnO2 were used, the method is not limited to this method. Compounds such as BaTiO3, carbonates, hydroxides, etc. may be heated in air to obtain the desired composition ratio. Accordingly, even if compounds such as [laO, Ti0z, CeO, 11bzos, and Mn0z are used, properties comparable to those of the examples can be obtained.

In addition, BaTiOi of commonly used industrial BaTiOi
/Ti ratio is 0.98 or more, and when BaTiO3 is used as a starting material, properties comparable to those of the examples can be obtained even if the insufficient amount of TiO□ is added.

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

Furthermore, titanium oxide, an industrial raw material commonly used for dielectric porcelain, such as titanium oxide KA-10 manufactured by Titan Industries ■ and titanium oxide FA-5H manufactured by Furukawa Mining ■, contains up to 0.45% by weight of NbzOs. However, even if these titanium oxides are used to create dielectric porcelain as the main component, the content of Nb2O5 is at most 0.17% by weight based on 100% by weight of the main component. Although it is outside the scope of the invention, considering the amount of Nb2O5 in titanium oxide, which is an industrial raw material,
By containing the insufficient amount of Nb2O5, characteristics comparable to those of the examples can be obtained.

Then, in addition to the basic composition mentioned above, ZnO, 5in2
Salts, oxides, etc., which are generally considered to be fluxes, such as Fe20a, can also be added within a range that does not impair the properties.

Effects of the Invention As described above, the present invention has a high dielectric constant, high dielectric breakdown voltage and high insulation resistance, and has a small crystal grain size, so the dielectric thickness can be reduced, and the product can be made smaller. Larger capacity is possible.

[Brief explanation of drawings]

FIG. 1 is a ternary diagram illustrating the composition range according to the present invention.

Claims (1)

[Claims] When expressed as the general formula xBaO-yTiO_2-zCeO_2 (where x+y+z=1.00), the molar ratio where x, y, and z are surrounded by the points a, b, c, and d shown below. 0.3 to 3 Nb_2O_2 to 100 weight of the main component consisting of the range of
．． A dielectric ceramic composition characterized by containing 0 parts by weight of MnO_2 and 0.05 to 0.25 parts by weight of MnO_2.