JPH03109256A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide the dielectric porcelain compsn. which can be sintered at a lower temp. and suppresses the growth of crystal grains at the time of calcination by incorporating respectively prescribed ratios of BaO and SiO2 as a side-components into a multi component oxide having a prescribed component compsn. thereby enhancing the sinterability. CONSTITUTION:The desired dielectric porcelain compsn. is obtd. by using the multi component oxide expressed by formula as its essential component and incorporating 0.03 to 2.4 pts.wt. BaO and 0.05 to 0.8 pts.wt. SiO2 and if necessary, 0.30 pts.wt. MgO as the side-components per 100 pts.wt. multi component oxide into the above-mentioned oxide. This compsn. can be calcined at the temp. lower by about 100 deg.C than heretofore, i.e., at <=1200 deg.C and, therefore, the saving of energy is attained and the finer particles and the higher dielectric constant are obtd. The formation of the porcelain dielectric layer to thinner thicknesses is, therefore, possible and large-capacity porcelain condensers satisfying the characteristics stipulated in JIS are produced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dielectric ceramic composition, and particularly to a ceramic composition useful as a dielectric material for a large-capacity multilayer capacitor.

(Prior Art) In order to use Ni and other base metals as internal electrode materials, dielectric ceramics that can be fired in a reducing atmosphere have been developed and put into practical use.

For example, as a dielectric material for multilayer capacitors with F characteristics or E characteristics specified in JIS, BaTi0+CaZrO
S-based or (BaCa)TiO*-based ceramic compositions are employed.

(Problems to be Solved by the Invention) However, since this type of porcelain composition has poor sintering properties, it is necessary to use it at high temperatures (usually around 13 oo'c) when achieving a high dielectric constant.
However, since the growth of crystal grains is unavoidable during firing and only crystal grains with a crystal grain size of about 5 to 10 μm can be obtained, the ceramic dielectric layer is made thinner. It has been extremely difficult to increase the capacity of multilayer ceramic capacitors.

Therefore, the basic objective of the present invention is to improve the sintering properties of a dielectric ceramic composition to enable sintering at a lower temperature, and to suppress the growth of crystal grains during firing. It is.

(Means for Solving the Problems) As a means for solving the problems described above, the present invention has as a main component a composite oxide represented by the general formula: % formula %) ≦1.020), Ba as a subcomponent to 100 parts by weight of oxide
0.03 to 2.4 parts by weight of O, 0.05 to 2 parts of SiO2
．． The content of MnO is 4 parts by weight, and if necessary, 0.30 parts by weight or less.

(Function) In the present invention, (Bat-x-ycaxMgy)m
(ri, -zzrz) Subcomponents added in predetermined amounts to the complex oxide represented by Os, namely BaO and 5ift,
Alternatively, these and MnO form a glass layer at the grain boundaries during firing, and this acts as a flux that coats each crystal grain to perform liquid phase sintering.

Therefore, sintering progresses even at low firing temperatures, and the growth of crystal grains is suppressed, making it possible to achieve finer grain size. Further, the subcomponents act organically on the composite oxide, which is the main component, to improve the electrical characteristics.

The reason why the composition of the main component of the present invention is limited to the above range is as follows.

That is, the composite oxide which is the main component has the general formula =ABO,
The mole fraction of Ca at the A site, xl
is less than 0.05, the capacitance temperature change rate (T Ccap
) becomes large, making it impossible to obtain porcelain that satisfies the E characteristics.
Further, if X exceeds 0.20, sintering will not occur, so X was set in the range of 0.05 to 0.20.

When the molar fraction of Mg, y, is less than 0.001, no sintering occurs,
If it exceeds 0.01, the rate of change in capacitance with temperature will increase and it will not be possible to obtain a porcelain that satisfies the E characteristic.
ot~0. It was set as the range of Ol.

In addition, the mole fraction % Z'% of Zr at the B site is 0
．． If it is less than 10, sintering will not occur, and if it exceeds 0.20, the capacitance temperature change rate will increase and a porcelain satisfying the E characteristic cannot be obtained, so 2 is set in the range of 0.10 to 0.20.

Molar ratio % of A site to B site 11% is 0.9
If it is less than 90, it will be reduced during firing in a reducing atmosphere and the desired electrical characteristics will not be obtained, and if it exceeds 1.020, it will not sinter, so - was set in the range of 0.990 to 1.020.

The reason why the content of the subcomponent based on 100 parts by weight of the main component is limited to the above range is as follows.

That is, the content of BaO is less than 0.03 parts by weight or 2.0 parts by weight.
If it exceeds 4 parts by weight, the growth of crystal grains will proceed, so it was set in the above range. Furthermore, if the SiOt content is less than 0.05 parts by weight, sintering will not occur, and if it exceeds 2.4 parts by weight, crystal grain growth will occur, so the above range was set.

Furthermore, although MnO has the role of lowering the firing temperature, if MnO exceeds 0.30 parts by weight, the insulation resistance decreases, so the content of MnO was set to 0.30 parts by weight or less. Note that this MnO does not necessarily need to be included.

(Example) As starting materials for the main components, BaCO3, CaCO3,
Using M g COs , T i O and ZrO,
These were mixed so that the composite oxide product had the composition shown in Table 1, wet mixed, calcined at 1100° C. for 2 hours, and then crushed to obtain calcined powder. BaCO3, SiO2 and Mn were added to 100 parts by weight of this calcined powder.
After adding O in the proportions shown in Table 1 and heat-treating at 1190°C, a binder was added and granulated, the granules were sized and formed into a disk shape with a diameter of 10 mo+ and a thickness of 111-. The obtained molded product was fired at 350°C in a natural atmosphere to remove the binder, and then heated at 1200°C at an oxygen partial pressure of 10-Torr in a reducing atmosphere consisting of N and Ol.
It was fired under the following conditions.

Silver electrodes were baked on both sides of each of the obtained porcelain disks using a conventional method to prepare a sample.

For each sample, the relative permittivity (εr), dielectric loss (DF, tanδ), capacitance temperature change rate (TC
cap) was determined. For TCc6p, the capacitance at +25°C was taken as a reference value, and the rate of change in capacitance with temperature at -25°C and +85°C with respect to the reference value was determined. The results are shown in Table 2. In the table, * indicates something outside the scope of the present invention.

Furthermore, when the crystal grain size of each porcelain was measured, it was found to be 3 μm or less in all cases.

(Left below) From the results in Table 2, the dielectric ceramic composition according to the present invention
It exhibits a high dielectric constant of up to 8600, has a dielectric loss of less than 1.3%, and has a capacitance change rate of +20% to -55.
Indicates a value within the range of %.

(Effects) According to the present invention, firing can be performed at a temperature approximately 100°C lower than that of conventional methods, that is, at a temperature of 1200°C or less.
Energy saving can be achieved, and the particles can be made finer and the dielectric constant can be increased, so the ceramic dielectric layer can be made thinner and a large capacity ceramic capacitor that satisfies the E characteristics stipulated by JIS. It is characterized by the excellent effect of being able to manufacture

Claims (2)

[Claims] (1) General formula: (Ba_1_−_x_−_yCa_xMg_y)m(T
i_1_−_xZr_x)O_3 (however, 0.05≦x
≦0.20, 0.001≦y≦0.01, 0.10≦z
≦0.20, 0.990≦m≦1.020) as the main component, and 0.03 to 2.4 parts by weight of BaO per 100 parts by weight of the complex oxide as a subcomponent. and 0.05 to 0.8 parts by weight of SiO_2. (2) General formula: (Ba_1_−_x_−_yCa_xMg_y)m(T
i_1_−_xZr_x)O_3) (However, 0.05≦
x≦0.20, 0.001≦y≦0.01, 0.10≦
z≦0.20, 0.990≦m≦1.020) as the main component, and as a subcomponent, 0.03 to 2.4 parts of BaO is added to 100 parts by weight of the complex oxide. Part by weight, 0.05 to 0.8 part by weight of SiO_2, 0 part by weight of MnO
．． A dielectric ceramic composition containing 30 parts by weight or less.