JPH04174908A - Dielectric porcelain composition material - Google Patents

Abstract

PURPOSE:To miniaturize a dielectric porcelain composition material and increase its capacity by containing specific pts.wt. of Nb2O5 and MnO2 against a main component 100 pts.wt. with a specific mole ratio. CONSTITUTION:Nb2O5 0.3-3.0 pts.wt. and MnO2 0.05-0.25 pt.wt. are contained against a main component 100 pts.wt. with the mole ratio surrounded by points (a), (b), (c), (d) shown by the table I for (x), (y), (z) expressed by the formula I. A high dielectric constant is obtained, the dielectric breakdown voltage and insulation resistance are increased, the dielectric substance can be made thin in thickness because the crystal grain size is small, the dielectric porcelain composition material can be miniaturized, and its capacity can be increased. In the formula I, x+y+z=1.00.

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, BaTi0. Bad, Cab, Ti0z, Z
It is known that a suitable amount of r0z 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.
Because it is large at 20 μm and has a high porosity, it can be applied to products with thin dielectrics such as multilayer ceramic capacitors.
There were issues such as a low dielectric breakdown voltage and a decrease in dielectric breakdown voltage and insulation resistance during the plating process to form the external electrodes.

Means for Solving the Problems In order to solve these problems, the present invention provides the general formula x B
When expressed as aO-y Ti0z-z LaOx/z (however, x+y+z-1,00), x, y, and z consist of the molar ratio range surrounded by each point a, b, c, and d shown below. 0.3 to 3 NbtOs per 100 parts by weight of the main component
．． The purpose of the present invention is to provide a dielectric ceramic composition characterized by containing 0 parts by weight of Mn01 and 0.05 to 0.25 parts by weight of Mn01. The reason for limiting the composition range will be explained with reference to FIG. 1. First, the dielectric constant is small in the At+i region, making it impractical. Furthermore, in the BeJf region, the Curie point becomes too large on the negative side, and the capacitance change rate of the temperature characteristic deviates greatly on the positive side, making it impractical. moreover,
Sintering is extremely difficult in the C region. Furthermore, De
In the ff range, the dielectric constant is small, making it impractical.

According to the structure of the present invention related to the above composition system and composition range, by containing NbzOs in the main component, it has the effect of improving the product of capacitance and insulation resistance (CR product) and dielectric breakdown voltage. However, the content of the main component is 10
If the content is less than 0.3 parts by weight, there will be no effect, whereas if it exceeds 3.0 parts by weight, the Curie point will shift to the negative side and the dielectric constant will decrease. In addition, Mn0 for the main component
By containing z, it has the effect of increasing the CR product, but its content is 100 parts by weight of the main component,
If it is less than 0.05 part by weight or more than 0.25 part by weight, the CR product will decrease. Furthermore, the composition of the present invention can have a crystal grain size of 2 to 8 μm.

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

The starting material is chemically highly purified B a COs + T.
10 z +Lazy, NbtOs and Mn0t
Weigh the powder so that it has the composition ratio shown in Table 1 below,
The mixture was placed in a rubber-lined ball mill equipped with agate balls together with pure water, and after wet mixing, it was dehydrated and dried. This dry powder was placed in a high alumina crucible and heated to 1100'C in air.
It was calcined 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. After adding an organic binder to this pulverized powder and making it homogeneous, it is sized through a 32-mesh sieve, and then molded under a pressure of 1 to 1 using a mold and hydraulic press.
It was molded to a diameter of 15-2 and a thickness of 0.4 wa.

Next, this molded disk was placed in an alumina pod 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 ceramic disc thus obtained were measured, and the dielectric constant, dielectric loss, and capacitance were measured using silver electrodes on both sides of the disc. As a sample for measuring dielectric breakdown voltage and insulation resistance, a silver electrode was baked to a depth of 1 m from the outer circumference of the inner disk of the dielectric Mi device. The dielectric constant, dielectric loss, and capacitance temperature characteristics were measured using a digital LCR meter model 4274A manufactured by Yokogawa/Heuret/Paracard at a measurement temperature of 20"C2.
It was determined from measurements at a measurement voltage of 1.0Vr and a measurement frequency of 1. Further, the dielectric breakdown voltage was determined by measurement using a high-voltage DC power supply manufactured by Kikusui Electronics Co., Ltd. Aji. Furthermore, the insulation resistance was determined by measurement using a high resistance meter manufactured by Takeda Riken Kogyo ■.

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

K-143,8XCoXt/D2 K: Dielectric constant Co: Capacitance at 20°C (pF) D: Diameter of dielectric ceramic disc (m) t: Thickness of dielectric ceramic disc (11111) The dielectric breakdown voltage was calculated from the following formula.

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

CR=CoXRO/10" CR: CR product (Mn pF) RO: Insulation resistance (Ω) Furthermore, the crystal grain size was determined by optical microscope observation at a magnification of 400. The test conditions and test results are as follows. It is also shown in Table 1.

(Left below) In addition, in the method for producing dielectric ceramic in the example, Ba
Although CO3, Ti0z, LatC13, NbzO6 and MnO were used, the method is not limited to this method. Compounds such as BaTi0+, carbonates, hydroxides, etc., were used in the air to obtain the desired composition ratio. By heating Bad, TiO2, La20. NbzOs
Even if a compound serving as Mn0z is used, properties comparable to those of the example can be obtained.

In addition, the BaTrOs of commonly used industrial BaTrOs
/Ti ratio is 0.98 or more, and when BaTiOi 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, which is an industrial raw material commonly used for dielectric porcelain, such as titanium oxide KA-10 manufactured by Titan Industrial Hachi Co., Ltd. and titanium oxide FA-55W manufactured by Furukawa Mining Co., Ltd., contains up to 0.45% by weight of Nb2Ol. However, even if dielectric porcelain is made using these titanium oxides as the main component, the NbzOs content is at most 0.17 per 100% of the main component! Although it is outside the scope of the present invention, considering the amount of Nb2O2 in titanium oxide as an industrial raw material,
By containing the insufficient amount of Nb2o, properties comparable to those of the examples can be obtained.

Then, in addition to the basic composition mentioned above, ZnO.

Salts If, M compounds, etc., which are generally considered to be fluxes, such as SiO□1FezO, etc., 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 made thinner and the product can be made smaller and larger. It is possible to increase the capacity.

[Brief explanation of drawings]

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

Claims (1)

[Claims] General formula xBaO-yTiO_2-zLaO_3_/_
2 (however, x+y+z=1.00), x,
For 100 parts by weight of the main component, where y and z are in the range of molar ratios surrounded by points a, b, c, and d shown below, Nb_2
0.3 to 3.0 parts by weight of O_5 and 0.05 parts of MnO_2
A dielectric ceramic composition characterized in that it contains ~0.25 parts by weight.