JPS5986103A - High dielectric constant porcelain 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 is particularly applicable to barium titanate (BaTiOs), which is used as a thin film dielectric material such as multilayer ceramic capacitors.
), which has a high dielectric constant value and a dense ceramic structure.

Conventional Structures and Their Problems Many ceramic capacitor compositions [7] whose main constituent is barium titanate have been known. As is well known, barium titanate is a unique material with ferroelectric properties and has a cubic perovskite structure at high temperatures.
Below 120°C, the C axis is slightly elongated to form a tetragonal crystal, which further changes to an orthorhombic crystal at around 0°C and a rhombohedral crystal at around -80°C.

The above-mentioned phase transition point near 120° C. is called the Curie point, and beyond the Curie point, it exhibits paraelectricity at higher temperatures and exhibits ferroelectricity at lower temperatures. At this Curie point, the dielectric constant exhibits an extremely high value of 10,000. Here, barium titanate alone cannot provide a high dielectric constant at room temperature. By moving the high dielectric constant of barium titanate near the Curie point to the low temperature side, small-sized capacitors having an appropriate capacitance near room temperature have been put into practical use more often than in the past. The additive that shifts the temperature at which the peak value of the dielectric constant occurs is called a shifter, and Ba5
nOs-, 5rSnOs, Ca5nOs, Pb
5nOs.

Stannates such as Cu5nO,s, Zn5nO3, CdSnOs, BaZrO3゜CaZr0a, 5rZ
Di/L/:7 phosphate such as rOs and SrTiO3゜P
Titanate salts of bTiOs are generally known, and have the strongest effect as a shifter in the order listed above. Barium titanate ceramic capacitors using these shifters have been used as single-plate lead wire type capacitors. However, recently, with the advancement of stacked chip technology, 30 to 100 μm
So-called laminated ceramic sheets and capacitors, which are made by laminating many layers of this thin film with electrodes sandwiched between them, have entered various electronics industries. It is increasingly being used as such a thin film dielectric for lamination.

However, in conventional single-plate ceramic capacitors, the dielectric thickness is as thick as 100 μm to 1,100,001 t.
Since the laminated ceramic capacitor is thin at 10 μm to 2 ottm, it receives an electric field strength of 5 to 10 times or more. Therefore, there is a need for a composition that has less voltage dependence than conventional single-plate capacitors. In addition, as the dielectric layer becomes thinner, structural defects in the ceramic become more likely to appear in the characteristics, so it is required that the crystal grains be uniform and fine, and that the pores be small and small. .

Purpose of the Invention In view of the above, the present invention provides a ceramic S7 having a high dielectric constant, few structural defects in ceramic, and low voltage dependence.
The present invention aims to provide a high dielectric constant ceramic composition that has few structural defects and has a high withstand voltage.

Structure of the Invention The present invention is based on barium titanate (BaTi0s),
Neodymium oxide (Nd203) and titanium oxide (Ti
It is a high dielectric constant ceramic composition consisting of O2).

DESCRIPTION OF EMBODIMENTS Below, embodiments of the present invention will be described in detail.
Barium titanate (BaTi0s) was synthesized as follows. That is, barium carbonate (BaCO5) and oxidized f ri/(Ti02) are combined at a [Ba]/(Ti) ratio of 1.0.
Mix with an accuracy of 00±0.006, 11oO~116o
After calcining at °C, it is best to crush it. Nd to this BaTi0s
2O3 and TlO2 are added in a ratio of (Nd)/(Ti) = -, mixed, then a binder is added and granulated, formed into a square plate shape and fired at a temperature of 125o to 1360℃. did. After this, a silver electrode was formed.

Table 1 below shows the characteristics of each composition at each firing temperature.

(Left below) As is clear from Table 1 above, Composition Shops 2, 3 and 4
It can be seen that can be used as the EIA standard Y5V characteristic. In other words, as shown in Figure 1, the capacitance change rate is +22% to -82% in the temperature range of -3°C to +86°C.
It fully satisfies the rate of change within the standard (20℃ standard), and still shows a dielectric constant equivalent to that of Y5V characteristic magnetic capacitors generally available on the market, which have a dielectric constant of around 1ωω. At the end of the table, a Y5V characteristic composition containing a zirconate salt is shown as a conventional example. The grain size (particle size) of the ceramic is 1 to 3/Zm in the composition of the present invention,
A multilayer ceramic capacitor as shown in FIG. 2 was prototyped with composition A3, in which the pore size (pore diameter) is about 3 μm at maximum, but in the conventional example, the grain size is 1 to 2 μm, and the pore size is about 20 μm at maximum. The results of a comparison between this and a direconate-based multilayer ceramic '7 capacitor are shown in Table 2 below. In FIG. 2, 1 is a dielectric with a thickness of 35 μm between electrodes, 2 is a palladium electrode, and 3 is a terminal electrode.

(The following is a blank space) As is clear from Table 2 above, it was found to have twice the bending strength and three times the breakdown voltage of the conventional one.

Effects of the Invention As described above, the composition of the present invention has fine grains, a dense ceramic with a small bore, a high dielectric constant, and a change in dielectric constant with temperature that satisfies the EIA standard Y6V characteristics. It can be used as a ceramic capacitor, especially as a multilayer ceramic capacitor. Since the breakdown voltage value is about three times that of conventional multilayer ceramic capacitors, the dielectric thickness of multilayer ceramic capacitors can be made thinner by 1/38 degrees than conventional ones, and the capacitance acquisition range can be increased to three times that of conventional ones. Its industrial value is extremely high, as it has the characteristic of being able to expand up to twice as much.

Although barium titanate was synthesized in the above example, commercially available barium titanate may also be used.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the range of temperature change rate of capacitance for the composition of the present invention, and FIG. 2 is a sectional view of a multilayer ceramic capacitor to which the composition of the present invention is applied. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure - Temperature d■ (・C) Figure 2 3f I7'

Claims (1)

[Claims] A high dielectric constant ceramic composition comprising 100 mol parts of barium titanate (BaTiOs), (7±1) mol parts of neodymium oxide (Nd203) and 7±1 mol parts of titanium oxide (TiO2).