JPS5918155A - 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 The present invention is a composite perovskite compound containing pbl, pb<Mqy4FeyAA)OJt and Pb(Mq%
This relates to a ceramic composition whose main component is Ta%) 03, and its objectives are to have a high dielectric constant, low dielectric loss, high insulation resistance, and can be sintered at low temperatures below 1000°C. An object of the present invention is to provide a high dielectric constant ceramic composition.

Conventionally, high dielectric constant ceramic compositions include barium titanate BaTiO3 as the main component, and calcium zirconate CaZ rO3 + calcium titanate CaTx.
Os + Calcium stannate Ca5no3. Products with improved characteristics by adding an appropriate amount of strontium titanate S r TiO3 have been put into practical use. The sintering temperature of these porcelains was generally as high as 1300°C to 1400°C.

In recent years, with the development of the electronic equipment field, electronic equipment has become smaller and smaller.
Multilayer ceramic capacitors with a laminated structure have been developed and widely used in order to significantly reduce weight and achieve large capacitance in a compact size compared to the conventionally used disk-shaped ceramic capacitors.

As shown in the drawing, a multilayer ceramic capacitor has a structure in which internal electrodes 2 are arranged above and below a ceramic dielectric 1, and many small single-plate capacitors are connected in parallel and stacked. They are alternately connected to one of the left and right external electrodes 3.

In order to manufacture this multilayer ceramic capacitor, it is necessary to sinter the internal electrodes while embedding them in the ceramic dielectric, but as mentioned above, the firing temperature for conventional high dielectric constant ceramic compositions is 1300°C or higher. As a result, the internal electrodes had to be made of platinum, which is stable even at such high temperatures, or an expensive noble metal such as palladium. Therefore, if we can develop a porcelain dielectric material that can be sintered at a low temperature of 100o'c or less and use it in multilayer ceramic capacitors, we can use inexpensive metal materials such as silver thread alloys and nickel-based alloys as internal electrode materials. This makes it possible to supply low-cost multilayer ceramic capacitors.

The present invention is based on the above-mentioned background.
As a result of repeated research on skite-type compounds, Pb (
%FeyWy)03te and pb(M
By using a compound represented by g%Ta%)o3, we succeeded in developing a porcelain dielectric material that has a high dielectric constant, low dielectric loss, high insulation resistance, and can be sintered at low temperatures. .

Examples of the present invention will be described in detail below.

First, by sintering, P b (Mg%Fe, W, )
Weigh appropriate amounts of lead oxide, iron oxide, tungsten oxide, magnesium oxide, and tantalum oxide so that the ratio of 03 and Pb (MqyT a%)o3 becomes the molar ratio shown in the following table,
This was mixed using a ball mill. This powder raw material is
After calcining at 50'C to 850C, the mixture was pulverized again using a ball mill, and polyvinyl alcohol was added to the pulverized raw material to granulate it, which was molded into a disk shape with a diameter of 13 wn and a thickness of 0.8 mm. After that, it was fired in a magnesia pot at a temperature of 920 to 980°C, and electrodes containing silver as a main component were applied to both sides to prepare a dielectric sample. The results of measuring the electrical properties of the samples thus prepared are shown in the following table. Here, the dielectric constant ε8 and dielectric loss tanδ are frequency 1
k) Measured at 25°C in h. Also, the insulation resistance IR is DC6
The measurement was performed at room temperature by applying 0V. Note that the firing temperature in the table is the lowest temperature for sintering to create dielectric ceramic.

(Margin below) Samples f;, 1 and 6 in the table are outside the scope of the present invention and are shown for comparison.
If the molar ratio X of y4Fe, W, Therefore, it is not practical.

As detailed above, the present invention (7) Pb (Mcr3
AFe, W, )03P b (Mgy'r' a%)0
If a 3-series ceramic composition is used, the dielectric constant ε6 is 3160 to 4.
It has a large dielectric loss of 1oO, a small dielectric loss tan δ of o6% to 26chi, and an insulation resistance IR of 62×1o10Q-Cm.
A novel dielectric ceramic composition with high performance and a small rate of change in capacitance due to temperature can be obtained. Furthermore, since the firing temperature is as low as 920°C to 980°C, the silver thread alloy is used as an internal electrode when used in multilayer ceramic capacitors.

Cheap metals such as nickel-based alloys can be used,
This is extremely effective in reducing the cost of multilayer ceramic capacitors. In addition, since sintering can be performed at low temperatures, it is not only easier to maintain the electric furnace used for firing, but also allows for energy savings in terms of power consumption.

Therefore, it is advantageous in terms of manufacturing costs not only when applied to multilayer ceramic capacitors but also when applied to conventional disk-shaped ceramic capacitors.

[Brief explanation of the drawing]

The drawing is a partially cutaway perspective view showing an example of a multilayer ceramic capacitor. 1... Ceramic dielectric, 2... Internal electrode,
3...External electrode.

Claims (1)

[Claims] Magnesium, iron, lead tungstate pb (Mg, AF
eqVζ)03 and magnesium lead tantalate pb
(Mg%Ta%)o3
A porcelain composition characterized in that the composition ratio X is within the range of 060≦X≦Q90 when expressed as: g, Fe, W, ) x (Mg, Ta,) 1.03.