JPS62119805A - Dielectric porcelain compound - 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 the Invention The present invention relates to a high dielectric constant ceramic composition that can be fired at a temperature of 1150° C. or lower.

Conventional technology Barium titanate-based materials have been widely used as high dielectric constant materials for ceramic capacitors, but this material has a high firing temperature of 1300 to 1400°C,
When used in multilayer ceramic capacitors, expensive platinum or palladium electrodes are required as internal electrodes. On the other hand, since the firing temperature is as low as 1150° C. or lower, a lead composite perovskite dielectric has been developed as a material that allows the use of cheaper silver thread electrodes as internal electrodes. For example, PbTi03, Pb (NitzriNb
As a system containing 2/l)03, JP-A-58-4966
The material disclosed in Publication No. 1 is known.

Problems to be Solved by the Invention The PbTiOs Pb(NitzsNb2,5)03-based solid solution has a high dielectric constant, but its dielectric properties are determined by the ratio of PbTios and Pb(Nit, 3Nb2/3)03. Therefore, it is not possible to obtain a material with arbitrary dielectric constant and temperature characteristics. Furthermore, this system has a large rate of change in dielectric constant with temperature.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic composition that provides a high dielectric constant and a relatively small rate of temperature change.

Means to solve the problem PbTiO3 and Pb(Nitzs Nbl2t3)Os
In addition, Pb (Zntz!l) is added as a third component to the solid solution of
Nb5zs)O3 is added.

Action PbTiO3Pb(Ni1,2Nbs,5)O3(7)
By solidly dissolving Pb(ZnxtsNb1zs)03 into the binary composition, various temperature characteristics of dielectric constant can be obtained.

Example Chemically pure pbo as a starting material.

Nb2O5, TiO2, Nip, and ZnO were used. After correcting the purity, a predetermined amount was weighed and mixed in a ball mill for 17 hours using agate cobblestones and pure water as a solvent. This was filtered by suction to remove most of the moisture, then dried, and then thoroughly crushed using a Raikai machine. After that, 5wt% of moisture was added to the powder amount, and a molding pressure of 500 kg/
cl? It was molded into a cylindrical shape with a diameter of 60mm and a height of about 5011II11. This was placed in an aluminum 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 in a ball mill using agate cobblestones and pure water as a solvent for 17 hours, filtered under suction to remove most of the moisture, and then dried. After repeating the above calcining, crushing, and drying several times, 6 wt % of polyvinyl alcohol aqueous solution was added to the powder, and the mixture was granulated through a 32-mesh sieve, and the molding pressure was 100.
It was molded into a cylindrical shape with a diameter of 1311Il11 and a height of about 5mm. The molded product was heated to 700°C in air and held for 1 hour to burn out the polyvinyl alcohol content, and after cooling, it was transferred to a magnesia porcelain container.
Cover with the same type of lid and heat in the air to the specified temperature at 400°C/hr.
The temperature was raised at a rate of 400° C./hr after being maintained for 2 hours.

The fired product was cut into a disk shape with a thickness of lllll, and both sides were coated with Cr.
-Au is evaporated and the dielectric constant, tan δ, is 1 kHzI V
Measurements were made under an electric field of /mm. Further, the resistivity was determined from the value 1 minute after applying a voltage of 1 kV/rm at 20°C. The firing temperature was set to 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, ferroelectric phase transition point, and resistivity.

The figure shows each sample shown in Table 1 as PbTi0a, Pb(Ni
1zs Nb2to )03 , Pb(Zn1z3Nb
2t! 1) This is shown in a triangular composition diagram in which each end member is Oa, and the shaded range indicates the range of the present invention.

For compositions outside the scope of the invention, samples marked with * in No. of Table 1 are given as examples, but the optimum firing temperature is 1150 ° C.
The dielectric constant is below 4000, the ferroelectric phase transition point is far from near room temperature, and the temperature change rate of the dielectric constant is large. ing. In the composition within the scope of the invention, the above-mentioned 3.
All problems have been overcome.

Effects of the Invention According to the dielectric ceramic composition of the present invention, a dielectric material having a high dielectric constant of 4000 or more and a small rate of change thereof can be obtained. Furthermore, since this dielectric material can be fired at temperatures below 1150°C, it is possible to use Ag-Pd-based materials as the internal electrodes of multilayer capacitor elements, making it possible to realize inexpensive multilayer capacitors, which has great industrial value. be.

[Brief explanation of drawings]

The figure is a triangular composition diagram showing the component composition of the porcelain composition according to the present invention. Name of agent: Patent attorney Toshio Nakao and one other person bTiOa

Claims (1)

[Claims] PbTiO_3, Pb(Ni_1_/_3Nb_2_
/_3) O_3, and Pb(Zn_1_/_3Nb_
2_/_3) Pb
Ti_x(Ni_1_/_3Nb_2_/_3)_y(
Zn_1_/_3Nb_2_/_3)_zO_3 (however, x+y+z=1.0), PbTiO_
3, Pb(Ni_1_/_3Nb_2_/_3)O_3
, Pb(Zn_1_/_3Nb_2_/_3) 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 = 0.30 y = 0.69 z = 0 .01B:x=0
．． 00y=0.30z=0.70C:x=0.00y=
0.60z=0.40D:x=0.10y=0.89z
A dielectric ceramic composition characterized in that it lies within a quadrangular region having vertices of =0.01.