JPH03203118A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To eliminate defects of an SrTiO3-Bi2O-TiO2-PbTiO3-based ceramic dielectric body by containing SrTiO3, PbTiO3, Bi2O3, TiO2 as main components and adding CuO, MnCO3, and MgO to the dielectric body. CONSTITUTION:A dielectric ceramic composition consists of mainly 35-55wt.% of SrTiO3, 25-38wt.% of PbTiO3, 10-24wt.% of Bi2O3, and 3-9wt.% of TiO2. As additives, CuO and MnCO3 and MgO are added to the main components in 0.1-0.5 pt.wt., 0.05-0.5 pt.wt., and 0.05-0.5 pt.wt., respectively per 100 pts.wt. of the main components. As a result, a dielectric ceramic composition having relatively high dielectric constant, good temperature coefficient, small tandelta at high frequency, and high breakdown voltage for dielectric ceramic capacitors is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] This invention relates to a dielectric ceramic composition used as a ceramic capacitor, particularly a 5rTi0. -Bi2O, -T t02
-Relating to a PbT i03-based ceramic dielectric material.

[Prior Art] Barium titanate (BaTiOg) ceramics, which have been widely used in ceramic capacitors and the like, are ferroelectric and piezoelectric ceramics, and those exhibiting ferroelectricity have a perovskite structure.

Generally, the above BaTi0. The larger the dielectric constant of the ceramic dielectric material, the more the temperature change of the dielectric constant, that is, from -25℃ to +
The change from the reference value (value at 20°C) at 85°C is large, for example, 10% of the overlay (also has the disadvantage that tan δ (referred to as dielectric loss tangent), which is an index expressing dielectric loss, is large. On the other hand, in the low frequency band,
5rTiO is a ceramic dielectric material with a relatively small tan δ, that is, low dielectric loss, and small temperature change in dielectric constant.
3Bi2O3-TiO2-PbTiO3-based porcelain dielectrics have come into use.

[Problem to be solved by the invention] However, the 5rTiO3-Bi2O3TiO2
Although the -PbTiO3-based ceramic dielectric has a relatively small tan δ in a low frequency band, it has a drawback that in a high frequency band of about 500 kHz, the tan δ becomes large and energy loss is large.

The object of the present invention is to use the above-mentioned porcelain dielectric, in particular 5rTie,
-Bi2O3-Ti02-PbTiO3 253 system ceramic dielectric has a relatively high dielectric constant and excellent temperature characteristics, and has a small tan δ in the high frequency band.
Another object of the present invention is to provide a dielectric ceramic composition for a ceramic capacitor that has a high boosted breakdown voltage.

[Means and effects for solving the problem] In order to achieve the above object, the present inventors have developed a conventional 5rTi0. -Bi2
While examining the composition ratio of each component (hereinafter referred to as the main component) of the O3-TiO2-PbTiO3-based ceramic dielectric,
As a result of repeated research on the type and amount of trace components (hereinafter referred to as additives) that should be added to the main component, we found that a relatively high dielectric constant can be achieved by adjusting the amount of the main component, especially P b T t O3. In addition, depending on the amount of TiO2 added, t in the high frequency band can be made into a dielectric material with
An δ can be improved, and CuO is added as an additional component.
The present inventors have discovered that excellent temperature characteristics can be provided by adding and coexisting Mn CO3, and that boosted breakdown voltage can be made higher by adding MgO.

Therefore, the present invention contains the following components as main components: S rTi 0335.0-55 wt% PbTi
O325,0~38.0wt%Bi2O31(1,0~
Contains 24.0% by weight of TiO23.0 to 9.0% by weight, and the following components as additives per 100 parts by weight of the above main components: 0.1 to 0.5 parts by weight of CuO M n C0,0.05 ~0.5 parts by weight M g 0
The present invention provides a dielectric ceramic composition characterized by having a composition containing 0.05 to 0.5 parts by weight.

Next, the reason for limiting the component composition as described above in the dielectric ceramic composition of the present invention will be explained.

(a) SrTi (h) If the content in the main component exceeds 55% by weight, the dielectric constant will decrease, and as the content increases, the sintering temperature will increase and the sinterability will deteriorate; 35.0% by weight
Since the dielectric constant decreases when the content is less than 35.0 to 55% by weight.

(b) Bi2O3 When the content in the main component exceeds 24.0% by weight, sintering becomes difficult and the firing temperature range becomes narrow. Even if it is sintered, it becomes porous, making it difficult to obtain a practical device. On the other hand, if the content is less than io, 0% by weight, the temperature characteristics of the dielectric constant deteriorate even though the dielectric constant is not so high. Therefore, the content was determined to be 1010 to 24.0% by weight.

(c) TiCh The Ti02 component has the effect of reducing tan δ in the high frequency band, but if the content of the main component exceeds 9.0% by weight, the temperature characteristics of the dielectric constant deteriorate; ．．
If it is less than 0% by weight, sinterability will deteriorate, so the content was set at 3.0 to 9.0% by weight.

(d) PbTiO3 P b Ti 03 component is blended to make a porcelain composition with a relatively high dielectric constant, but if the content of mo in the main component exceeds 38.0% by weight, the dielectric constant will decrease. Temperature characteristics deteriorate and sinterability also becomes poor. On the other hand, when the content is less than 25.0% by weight, the dielectric constant decreases, so the content is set at 25.0 to 38.0% by weight.

(e) CuO The CuO component coexists with the MnCO3 component and has the effect of maintaining excellent temperature characteristics, but its content is higher than the main component (0
If the amount exceeds 0.5 parts by weight relative to 0 parts by weight, the sintering properties will be reduced, and even if sintering is possible, it will become porous and the required dielectric constant will not be obtained. On the other hand, if the content is less than 0.1 parts by weight based on the above criteria, no effect is observed, so the amount added should be 0.1 to 0.
．． The amount was determined to be 5 parts by weight.

(f) MnCO: + MnCO3 component coexists with the CuO component as mentioned above and has the effect of contributing to temperature characteristics, but if it exceeds 0.5 parts by weight based on 100 parts by weight of the main component, tan δ will decrease. increase On the other hand, based on the same standard, if it is less than 0.05 parts by weight, no effect of improving the dielectric constant and temperature characteristics is observed, so the amount added is set at 0.05 to 0.5 parts by weight per 100 parts by weight of the main component.

(g) MgO The MgO component has the effect of increasing the boost breakdown voltage, but
When the amount exceeds 0.5 parts by weight based on 100 parts by weight of the main component, tan δ on the high frequency side increases. On the other hand, 0.0 based on the same standard
Since the effect of addition is not observed if it is less than 5 parts by weight, the amount added is determined to be 0.5 parts by weight per 100 parts by weight of the main component.

Hereinafter, the dielectric ceramic composition of the present invention will be explained using Examples and in comparison with Comparative Examples.

[S r T i O having a purity of 98% or more in each example]
3, Bi2O3, TiO2 and PbTiO3253 (
above as main components) and CuO1M n CO as an additive
s and MgO were weighed so as to have the composition ratios shown in Table 1. In this case, the amount of the additive is expressed as a weight ratio relative to 100 parts by weight of the main component. Next, the materials having the above composition ratio were wet mixed using a polyethylene pot and a urethane ball to prevent contamination of impurities. Next, after dehydrating and drying the mixture, a polyvinyl alcohol aqueous solution was added as a binder, and a diameter of 18 mm and a thickness (f
It was pressure molded into a flIll disk at a pressure of 2.000 kg/cm'.

Next, the molded body was charged into an electric tunnel furnace using an Elema heating element and main firing was performed at a temperature of about 1,2O0 to 3OOC to obtain Sample 1-12.

Baking a silver electrode onto the porcelain element thus obtained,
Characteristic tests were carried out to determine the dielectric constant ε, l kHz and 500
tan δ (%) in Hz, temperature change rate of dielectric constant TC
(%), i.e. the reference value at -25°C and +85°C (
20° C.) as well as the boosted breakdown voltage (kV/vw), labeled BDV. These results are shown in Table 1.

[Comparative Example] Among the main components and additives used in the examples, and the same types of components, raw materials were weighed so that at least one component was outside the scope of the present invention as shown in Table 2. After producing a molded article in the same manner as in the example, the same characteristic test was conducted. The results are shown in Table 2.

(Left below) Although the present invention has been described based on Examples, methods other than those described in the Examples may be used to manufacture capacitors using the ceramic composition of the present invention. SrT i O3, B l 2O
3, T l O□, PbTiO3, Cu0. MnCO
3 and MgO, but the starting materials are not limited to these, in short, 5rSTi, B15Pb, Cu
It is sufficient that SMn5Mg and the like are contained so as to have the composition of the present invention in terms of their typical oxides.

That is, Sr or a Sr compound and Ti or a Ti compound that can obtain a perovskite structure by sintering;
i or Bi compound from which Bi2O3 can be obtained by sintering, Ti or Ti compound from which TiO2 can be obtained by sintering, P b T I by sintering
For pb or pb compounds capable of obtaining O3, additives CuOlMnCO3, and MgO, the respective metals or their compounds capable of obtaining these by sintering may be used as starting materials.

[Effects of the Invention] As explained above, according to the present invention, 3,000 to 4
, has a relatively high dielectric constant of about 700, and has excellent temperature characteristics such that the temperature change rate of the dielectric constant is within ±10% from -25℃ to +85℃, and tan δ, which is an index expressing dielectric loss, is 0.2 to 0.0 at 1 kHz. fi
(%), especially in the high frequency band 500 kHz, which is small at 2.5
% or less and has a boosted breakdown voltage of 12 kV or more per 11TllT1, thereby providing a dielectric ceramic composition with excellent properties.

Claims (1)

[Claims] The following main components: SrTiO_3 35.0-55% by weight PbTiO_3 25.0-38.0% by weight Bi_2O_3 10.0-24.0% by weight TiO_2 3.0-9.0% by weight % and the following components as additives based on 100 parts by weight of the above main components: CuO 0.1 to 0.5 parts by weight MnCO_3 0.05 to 0.5 parts by weight MgO 0.05 to 0.5 parts by weight A dielectric ceramic composition characterized in that it has a composition comprising: