JPS6283351A - 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 that is fired at a firing temperature of 1000° C. or lower, and particularly to one that has a high resistivity at high temperatures.

Conventional technology In recent years, ceramic capacitors have become smaller and smaller.
Multilayer ceramic capacitors are rapidly becoming popular due to the demand for larger capacitance. Multilayer ceramic capacitors are typically manufactured by a process of integrally firing internal electrodes and ceramics. Barium titanate-based materials have traditionally been used for high-permittivity ceramic capacitor materials, but because the firing temperature is as high as 1,300°C, expensive metals such as Pi and Pd are used as internal electrode materials. There was a need.

In contrast, lead composite perovskite materials have been developed that can be fired at temperatures below 1100° C. and can use Ag-based materials, which are cheaper than the former, as internal electrodes.

Among these, for example, Pb(Zn1ts Nbzz+
) 03 and Pb (Mgtz+Nb2ts > 03) as disclosed in JP-A-57-25607 and JP-A-57-25607.
Materials described in JP 7-27974 and the like are known.

Problem to be solved by the invention Pb(Znx/3Nbzzs)O* -Pb(Mg1
Although the zsNb2ts) Oo-based solid solution has a high dielectric constant, its resistance value tends to decrease slightly, especially at high temperatures.

In view of this problem, the present invention uses Pb(Zn1z+Nb2
zs)OsPb(Mgtz3Nb*zs)It is an object of the present invention to provide a dielectric ceramic composition that does not impair the high dielectric constant of the Os system and has a high resistance value at high temperatures.

Means for solving the problemPb(Zntzz Nb2t3)03-Pb(Mg*/
5Nb2,3)03 system as a third component, Pb(7,n
1tx Wl/2) 03 was added to the composition.

Effect In the composition within the scope of the present invention, Pb (Znsz2Wl
,3Nb2/3)O3Pb(Zn1/2W1/2)O3
Pb(Zntzs Nb2z3)Oz Pb(Mg
i/3Nb2z*) By adding it to the Os system, 10
At a firing temperature of 00°C or less, a dense sintered body that provides high reliability as a multilayer capacitor element can be obtained, and it is possible to use Ag-based materials as internal electrodes, and it also has a high resistance value at high temperatures. An element having the following properties is obtained.

The starting materials for the examples include chemically highly pure P b ON M go
, Nb20s 1ZnO1W Os were used. After correcting the purity of these, a predetermined amount was weighed and mixed in a ball mill for 17 hours using agate cobblestones and pure water as a solvent. This is suction filtered to remove most of the moisture, dried, and then thoroughly crushed in a Raikai machine.
After adding wt% of water, it was molded into a cylinder with a diameter of 60++ll111 and a height of about 50mm at a molding pressure of 500kg/cm2. 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 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, a 6 wt % aqueous solution of polyvinyl alcohol was added to the powder in an amount of 6 wt % of the powder amount.
Granulated through a 32 mesh sieve and molded under a pressure of 1000
kg/c+a2, and was molded into a cylindrical shape with a diameter of 13 days and a height of about 511 Ill. 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 to a specified temperature in air at 400°C/h. 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 m, and both sides were coated with Cr-Au.
was deposited, and the dielectric constant, tan δ, was 1kHz, IV/lll.
Measurements were made under an electric field of 111 degrees. Moreover, the resistivity was determined from the value 1 minute after applying a voltage of 1 kV/mm at 20°C and 85°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, and resistivity.

The figure shows each sample shown in Table 1 with Pb (Zn1z+Nb2zs
)03-Pb (Mg!z+ Nb2t3) 03-
Pb(Zn+t2Wl/2) This is shown in a triangular composition diagram with Ch as an end member, and the shaded range is the scope of the invention.

For compositions outside the scope of the invention, No. in Table 1.

The samples marked with * are given as examples; the optimum firing temperature exceeds 1100°C and the dielectric constant is 4000 or less.
It has one or more of the following three problems: the resistance value becomes low under high temperatures, or a combination of these three problems. Compositions within the scope of the invention overcome all three problems mentioned above.

Effects of the Invention According to the present invention, a dense sintered body for obtaining high reliability as a multilayer capacitor element can be obtained at a temperature of 1000°C or less, and it is 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 obtained.

[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
b(Zn_1_/_3Nb_2_/_3)O_3Pb(
A three-component ceramic composition consisting of Zn_1_/_2W_1_/_2)O_3 was mixed with Pb(Mg_1_/_3Nb_2_/_3)_x(Zn
_1_/_3Nb_2_/_3)_y(Zn_1_/_
2W_1_/_2)_zO_3 (however, x+y+z=1.00), Pb(Mg_1_/_3N
b_2_/_3) O_3, Pb(Zn_1_/_3Nb
_2_/_3) O_3, Pb(Zn_1_/_2W_1
___/_2) The following composition points A, B, C, D in the ternary composition diagram indicated by triangular coordinates with O_3 as the vertex A: x = 0.875y = 0.100z = 0.025B:
x=0.600y=0.375z=0.025C:x=
0.300y=0.600z=0.100D:x=0.
A dielectric ceramic composition characterized by having a composition within a rectangular region having vertices of 300y=0.400z=0.300.