JPS6283350A - Dielectric ceramic composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high dielectric constant dielectric ceramic composition fired at a temperature of 1100° C. or lower, and particularly to one having a high resistivity at high temperatures.

Conventional technology In recent years, ceramic capacitors have become smaller and smaller.
Due to the demand for larger capacity, multilayer ceramic capacitors are rapidly becoming popular. Multilayer ceramic capacitors are usually manufactured by a process of integrally firing internal electrodes and ceramics. Conventionally, barium titanate-based materials have been used for high-permittivity ceramic capacitor materials, but because the firing temperature is as high as 1300°C, expensive metals such as Pt and Pd have been used as internal electrode materials. It was necessary to use it.

In contrast, a lead-composite perovskite material has been developed that can be fired at 1100° C. or lower and allows the use of Ag-based materials, which are cheaper than the former, as internal electrodes.

For example, PbZr03 and Pb (Mgxts Nb*zs
)03 is included in JP-A-56-48004.
The material described in the publication is known. The inventors also
Already PbZr03, Pb (Mg1zs Nt12
z, J)03, Pb (N1tz2W1/2) O
We have proposed a high dielectric constant dielectric ceramic composition consisting of three components.

Problems to be Solved by the Invention PbZr03-Pb (Mg1/3Nbqts) OG solid solutions have a high dielectric constant, and some can produce dense sintered bodies at sintering temperatures of 1100°C or lower. The resistance value of the element tends to decrease due to evaporation of the lead component during firing, and the resistance value tends to decrease particularly at high temperatures.

In view of such problems, the present invention has developed PbZr0s-Pb (
The object of the present invention is to provide a dielectric ceramic composition that lowers the firing temperature without impairing the high dielectric constant of the Mg1/3Nbqts 03 series, and has a high resistance value especially at high temperatures.

Means to solve the problem PbZrO3-Pb (Mgtz3Nb2z3)03
Pb (Zn*t2W1/2) as a third component in the system
Add 03.

By adding Pb (Znxt2W1/2) 03, a dense sintered body that can provide high reliability as a multilayer capacitor element can be obtained at a firing temperature of 1100°C or less, and Ag-based materials can be used as internal electrodes. This makes it possible to obtain a highly reliable element having a high resistance value under high temperatures.

Starting materials for the examples include chemically highly pure P b O1M g O
zN b 20! , Z r O2, Z n OSW
O3 was used.

After correcting the purity of these, weigh the specified amount,
Mixing was carried out for 17 hours using a ball mill using agate boulders and pure water as a solvent. This was filtered by suction to remove most of the moisture, then dried, and then thoroughly crushed in a Raikai machine. After that, 5wt% of moisture was added to the powder amount, and the molding pressure was 500kg/cm.
2 into a cylindrical shape with a diameter of 60III11 and a height of about 50+w++. This was placed in an alumina crucible, covered with a homogeneous lid, and calcined at 750°C to 880°C for 2 hours. Next, the calcined product was roughly crushed in an alumina mortar, and further crushed for 17 hours in a ball mill using agate boulders and pure water as a solvent.The resulting mixture was filtered under suction to remove most of the moisture, and then dried. After repeating the above calcining, crushing, and drying several times, a 6 wt% aqueous solution of polyvinyl alcohol was added to the powder to give 6 wt% of the powder amount.
t% was added, and the mixture was granulated through a 32-mesh sieve, and molded into a cylindrical shape with a diameter of 13 cm and a height of about 5 m at a molding pressure of 1000 kg/cm2. The molded product was heated to 700°C in air and held for 1 hour to burn out the polyvinyl alcohol content. After cooling, it was transferred to a Magnesia porcelain container, covered with a similar lid, and heated in air to a specified temperature of 400°C. /
The temperature was raised at 400°C/hr, held for 2 hours, and then lowered at 400°C/hr.

The fired product was cut into a disk shape with a thickness of 1 mm, and both sides were coated with Cr −
Au was evaporated, the dielectric constant, tan δ was 1 kHz, I V
Measurements were made under an electric field of /w. Further, the resistivity was determined from the value 1 minute after applying a voltage of 1 kV/+n+a at 20° C. and 85° C.

The firing temperature was set at the temperature at which the density of the fired product was the highest.

Table 1 shows the composition range of the present invention, peripheral composition components, firing temperature, dielectric constant, tan δ, temperature change rate of dielectric constant, and resistivity.

The figure shows each sample shown in Table 1, PbZr0+, Pb(Mg
1/3Nbqts) 03% Pb (Zntt*
It is shown in a triangular composition diagram with W1/2)o3 as an end member, and the shaded range indicates the range of the present invention.

For compositions outside the scope of the invention, samples marked with * in Table 1 are listed as examples, but the optimum firing temperature exceeds 1,100°C, the dielectric constant is 4,000 or less, and the resistance at high temperatures is shown. The composition within the scope of the invention overcomes all three problems.

Effects of the Invention According to the present invention, it is possible to obtain a dense sintered body for achieving high reliability as a multilayer capacitor element at a temperature of 1100°C or lower, making it possible to use Ag-based materials as internal electrodes. An excellent dielectric ceramic composition having a dielectric constant of 4000 or more and high resistivity at high temperatures can be realized.

[Brief explanation of drawings]

The figure is a triangular composition diagram showing the component composition of the porcelain composition according to the present invention.

Claims (1)

[Claims] Pb(Mg_1_/_3Nb_2_/_3)O_3, P
bZrO_3, Pb(Zn_1_/_2W_1_/_2
) Pb(Mg_1_/_3Nb_2_/_3)_xZr_
When expressed as y(Zn_1_/_2W_1_/_2)_zO_3 (however, x+y+z=1.00), P
b(Mg_1_/_3Nb_2_/_3)O_3, Pb
ZrO_3, Pb (Zn_1_/_2W_1_/_2)
In the ternary composition diagram shown in triangular coordinates with O_3 as the vertex, the following composition points A, B, C, D A: x = 0.950 y = 0.025 z = 0.025 B:
x=0.725y=0.250z=0.025C:x=
0.025y=0.825z=0.150D:x=0.
A dielectric ceramic composition characterized by having a composition within a rectangular region having vertices of 025y=0.400z=0.575.