JPS61188811A - High 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-permittivity ceramic composition containing barium titanate as a main component and having a high dielectric constant and a dense ceramic structure.

BACKGROUND OF THE INVENTION Many ceramic capacitor compositions based on barium titanate have been known in the past. As is well known, barium titanate is a unique ferroelectric substance that has a cubic perovskite structure at high temperatures.
Below 12O'C, the C axis is slightly elongated and becomes a tetragonal crystal9.
Furthermore, it changes to orthorhombic crystal at around 0''C and to rhombohedral crystal at around -80°C.

The phase transition point near 12O″C mentioned above is called the Curie point,
It exhibits paraelectricity at temperatures higher than this Curie point,
It exhibits ferroelectricity at low temperatures. At this Curie point, the dielectric constant exhibits an extremely high value of about 10ooO. Many attempts have been made to commercialize small capacitors having an appropriate capacitance near room temperature by moving the high dielectric constant of barium titanate near the Curie point to the low temperature side. The additive that shifts the temperature at which the peak value of the dielectric constant occurs is called a shifter, and BaS
nO3,5rSn○3. CaSnO3゜PbSnO3,
Cu5n○3. Zn5no3. stannates such as CdSnO3, zirconates such as BaZrO3, CaZrO3, 5rZr○3, and 5rTi○3. Titanate salts such as P bT l○3 are generally known, and their effect as a shifter is strong in the order listed above.

Barium titanate ceramic capacitors using these shifters have been used as single-plate lead wire type capacitors. However, with recent advances in laminated chip technology, dielectric sheets of about 30 to 100 μm can be easily obtained, and so-called laminated ceramic chip capacitors, in which many layers of these sheets are laminated with electrodes sandwiched between them, have become popular in various electronics industries. As a result, conventional dielectric ceramic compositions are increasingly being used as dielectric materials for such laminations.

Problems to be Solved by the Invention However, in conventional single-plate ceramic capacitors, the dielectric thickness is as thick as 100 μm to 10,000 μm, but in multilayer ceramic chip capacitors, the thickness is as thin as 10 μm to 2 μm, so the electric field is 6 to 10 times greater. Receive strength. Therefore, there is a need for a composition that has less voltage dependence than conventional single-plate capacitors. Furthermore, as the dielectric layer becomes thinner, structural defects in the ceramic tend to appear in the characteristics, so it is required that the crystal grains be fine and uniform, and that the pores be small and small.

The object of the present invention is to obtain a dense porcelain composition with low voltage dependence and a small and small bore.

Means for Solving the Problems The present invention solves the above problems by adding 2±1 mol parts of europium oxide (Eu2o3) and zirconium oxide (ZrO□) to 100 mol parts of barium titanate (BaTiO3). The present invention provides a high dielectric constant ceramic composition to which 4±1 mole parts of the present invention are added.

Function: The high dielectric constant ceramic composition of the present invention has a grain size of 3 μm.
It is possible to obtain an extremely dense sintered body with fine holes of ~1 μm and pores of 5 μm or less, a normal temperature frequency of 1 convex, and an AC voltage of 1 V.
It has a high dielectric constant of 60oO to 80oO and exhibits good characteristics with a dielectric loss -δ value of 1% or less, so it satisfies the requirements for a high-permittivity ceramic composition for multilayer ceramic chip capacitors. It is something.

Example Hereinafter, the present invention will be explained in detail based on Examples.

First, barium titanate (BaTiO3) was synthesized as follows. That is, barium carbonate (BaC0s)
and titanium oxide (T i O2) as CBa'll/CTi
:L ratio is mixed with an accuracy of 1.000±0.05, 11o
It was obtained by calcining at 0 to 1150°C and pulverizing. This BaT
Eu2O3 and Z r02 to iO3 cEu+/cz
r]== After mixing, add a binder and granulate it, form it into a square plate shape and make it 1260~13
It was fired at a temperature of 6°C. After this, a silver electrode was formed.

Table 1 below shows the characteristics of each composition at each firing temperature.0 As is clear from the table above, compositions &2, 3 and 4 are E
It can be seen that this can be used as the YsU characteristic specified in the IA standard. That is, as shown in Figure 2, the capacitance change rate is +22°C in the temperature range of -30''C to +85°C.
% to -56%, the rate of change in the diagonally lined range in the figure (25”C
YsU which fully satisfies the standard) and is generally commercially available.
The dielectric constant is approximately the same as that of a characteristic ceramic capacitor, which has a dielectric constant of 500 to 10,000. At the end of Table 1, a zirconate-based YsU characteristic composition is shown as a conventional example. The grain size (particle size) of the ceramic is around 1 to 3 μm in the composition of the present invention, and the maximum pore size is around 3 to 4 μm, but in the conventional example, the grain size is as large as around 8 to 15 μm. Pore size up to 2o
It is around μm.

A multilayer ceramic chip capacitor with composition f3 as shown in FIG. 11 was manufactured as a prototype. Table 2 shows the results of a comparison between this capacitor and a zirconate-based multilayer ceramic capacitor. In FIG. 1, 1 is a dielectric with a thickness of 35 μm between the electrodes, 2 is a palladium electrode, and 3 is a pin terminal electrode.

As is clear from Table 2 above, it can be seen that the flexural strength is twice that of the conventional one.

Effects of the Invention As described above, the composition of the present invention can produce a dense ceramic with fine grains and small bores.
High dielectric constant, temperature change in dielectric constant is EIA standard YsU
It can be used as a ceramic capacitor that satisfies the characteristics, especially as a multilayer ceramic chip capacitor. In addition, because it has a three-value breakdown acid that is about 2 to 3 times as large as that of conventional multilayer ceramic chip capacitors, it is possible to reduce the dielectric layer thickness to about Z compared to conventional ones, and the capacitance acquisition range can be up to three times that of conventional ones. It has extremely high industrial value, such as its ability to be expanded.

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

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a multilayer ceramic chip capacitor to which the composition of the present invention is applied, and FIG. 2 is a diagram showing the range of temperature change rate of capacitance regarding the composition of the present invention. 1... Dielectric material, 2... Palladium electrode, 3... Silver terminal electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person! I
gJ Hitoshi

Claims (1)

[Claims] A high dielectric constant ceramic composition comprising 100 mol parts of barium titanate (BaTiO_3), 2±1 mol parts of europium oxide (Eu_2O_3) and 4±2 mol parts of zirconium oxide (ZrO_2).