JPS6283354A - 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 1100° C. or lower, and particularly relates to one in which the dielectric constant changes little with temperature.

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 as high-permittivity ceramic capacitor materials, but because the firing temperature is as high as 1300'C, expensive metals such as Pt and Pd are used as internal electrode materials. It was necessary to use

On the other hand, 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.

The problem to be solved by the present invention is that when Pb(Zrxt3Nb2z+)03 is fired as a dielectric ceramic under normal conditions, it does not have a perovskite structure and exhibits a low dielectric constant.

On the other hand, it is known that when fired under high pressure and high temperature, it takes on a perovskite structure and exhibits a high dielectric constant, but there is a problem in that the Curie point is at 140°C and the rate of change in dielectric constant with temperature is large.

The present invention uses Pb(Z
An object of the present invention is to provide a dielectric ceramic composition based on ntz+ Nbzz+ )03.

Means for solving the problem P b (Z n1/:l Nb213) 031::,
The composition includes Pb(NiI, 2Wri, 2)03 as a second component.

Action Pb(Znx, 3Nb2.s)03Pb(Ni
I, 2Wl, 2)03-based compositions have a perovskite structure when fired as dielectric porcelain under normal conditions, have a high dielectric constant and a small temperature change rate of the dielectric constant, and have a high dielectric constant of 1100℃.
At the following firing temperature, a dense sintered body that can provide high reliability as a multilayer capacitor element can be obtained.

The starting materials for the examples include chemically highly pure Pb0, Zn○, and WO3.
, Ni○, and Nb2 os were used. After correcting the purity of these, a predetermined amount was weighed, and mixed using an agate cobblestone and pure water as a solvent in a ball mill for 17 hours. This was suction-filtered to remove most of the moisture, then dried, and then thoroughly crushed in a Raikai machine, after which 5wt% of moisture was added to the powder, and the powder was shaped into a cylinder with a diameter of 6Q mm and a height of about 50mm.
Molding was performed at a molding pressure of 500 kg/cm2. Place this in an aluminum crucible, cover with a similar lid, and heat to 750°C to 810°C.
It was calcined 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 powder was granulated through a 32 mesh sieve, with a diameter of 13 mm at a compacting pressure of 1000 kg/cn2.
IiI111 It was molded into a cylindrical shape with a height of about 5III [11]. The molded product was heated to 700°C in air and held for 1 hour to burn out the polyvinyl alcohol. 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/ After increasing the temperature for 2 hours and holding it for 2 hours,
The temperature was lowered at a rate of 00°C/hr.

The fired product was cut into a disk shape with a thickness of 1 mm, and both sides were coated with Cr-A.
evaporated with dielectric constant, tan δ of 1 kHz, IV/mm
Measured under an electric field of

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, and temperature change rate of dielectric constant.

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

The samples marked with an asterisk (*) are taken as examples, but they have the disadvantage that the Curie point deviates significantly from room temperature, the dielectric constant decreases, and the temperature change rate of the dielectric constant increases. Compositions within the scope of the invention overcome the aforementioned disadvantages.

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 1100°C or less, and it is possible to use Ag-based materials as internal electrodes. An excellent dielectric ceramic composition having a high dielectric constant and a small temperature change in the dielectric constant can be obtained.

Claims (1)

[Claims] Pb(Zn_1_/_3Nb_2_/_3)O_3, P
A two-component ceramic composition consisting of b(Ni_1_/_2W_1_/_2)O_3 was mixed with Pb(Zn_1_/_3Nb_2
___/_3)_x(Ni_1_/_2W_1_/_2)_
When expressed as yO_3 (x+y=1.00)
A dielectric ceramic composition characterized by having a composition within the range of 0.70≦x≦0.92.