JPS61188809A - 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 dielectric constant ceramic composition mainly composed of titanate and thurium and having a high dielectric constant and a dense ceramic structure. Many ceramic capacitor compositions are known that mainly contain barium titanate. As is well known, barium titanate is a unique ferroelectric substance that has a cubic perovskite structure at high temperatures.
At temperatures below 120°C, the drawing power of HatiIt1 increases and becomes a lower product, and furthermore, it becomes orthorhombic at around 0°C, and -80°C.
Nearby, it transforms into rhombohedral crystals.

The phase transition point near 12O'C mentioned above is called the Keili point,
It exhibits paraelectricity at temperatures higher than this point,
It exhibits ferroelectricity at low temperatures. At this single point, the dielectric constant exhibits an extremely high value of approximately 1000o. 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 key point to a lower temperature side. The additive that shifts the temperature at which the peak value of the dielectric constant occurs is called a shifter, and BaSn
O3,5rSn03. CaSnO3, PbSnO3, C
u5n03, Zn5n03.

stannates such as CdS nO3, BaZrO3, CaZ
Zirconates such as rO3, SrZrO3 and 5rTi
Titanates such as 03 and PbTiO3 are generally known, and the effect as a shifter is stronger in the above order. Barium titanate ceramic capacitors using these shifters have been used as single-plate lead wire type capacitors.

However, with recent advances in stacked chip technology,
Dielectric sheets of about 100 μm can be easily obtained, and so-called laminated ceramic capacitors, which are made by stacking many layers of these sheets with electrodes sandwiched between them, have entered various electronics industries, and the conventional dielectric ceramic composition Increasingly, materials are 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/IrrL~1000Q)Im, while in multilayer ceramic TEP capacitors it is as thick as 10μ.
Since it is thin at ~20 μm, the electric field strength is 5 to 10 times higher than that of a tuning fork. 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 samarium oxide (Sm2O3) 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 fine grain size of 3 mtn to 1 m) and pores of 5.0 m to 1 m. Ill? It is possible to obtain an extremely dense sintered body of 1 L or less, and the normal temperature frequency is 1.
KHz, dielectric constant at AC voltage 1v is 6o00~8000
It has a high dielectric constant and exhibits good characteristics with a dielectric loss tan δ of 1% or less, so it satisfies the requirements for a high dielectric constant ceramic composition for a multilayer ceramic chip capacitor.

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 (BaCo3) and titanium oxide y (Ti02) are mixed with an accuracy of (Ba)/[Ti] ratio of 1,000±0.05,
It was obtained by calcining at 50'C and pulverizing. Sm2O3 and zrO□ are added to this BaTiO3 as (Sm)/[Zr)=-z
After mixing, add a binder and granulate it, form it into a square plate shape and make it 1250~1350'.
It was fired in a range of C. 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 the table above, compositions No. 2, 3 and 4
It can be seen that this can be used as the YsU characteristic specified in the KIA standard. That is, as shown in the detailed capacitance change rate in Figure 2, +
22% to -56%, the rate of change in the diagonally lined range in the figure (25%)
°C standard) and is generally available on the market.
Dielectric constant of 5U characteristic ceramic capacitor 5ooo~1o00o
The dielectric constant is almost the same as that of . At the end of Table 1, a zirconate-based Y6U 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 around 8 to 1571 μm. It is large, with a maximum pore size of around 2O/1rIL.

A multilayer ceramic chip capacitor with composition No. 3 as shown in FIG. 1 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, and the thickness between the electrodes is 35. Ill? 7L, 2 is a palladium electrode, and 3 is a silver terminal electrode.

(The following is a blank space) As is clear from Table 2 above, it can be seen that the bending strength is twice that of the conventional one.

Effects of the Invention As described above, the composition of the present invention provides a dense ceramic with fine grains, few bores, and small size, has a high dielectric constant, and has a temperature change in the dielectric constant that meets the XIM standard Ys.
It can be used as a ceramic capacitor that satisfies U characteristics, and as a multilayer ceramic chip capacitor.

Since the breakdown voltage value is approximately 2 to 3 times higher, the dielectric thickness of multilayer ceramic chip capacitors can be reduced to the same level as conventional capacitors, expanding the capacitance acquisition range to three times that of conventional capacitors. It has extremely high industrial value, such as the ability to

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 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 for 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 - Electrostatic charge (/,)
To envy
1 ticket

Claims (1)

[Claims] A high dielectric constant ceramic composition comprising 100 mol parts of barium titanate (BaTiO_3), 2±1 mol parts of samarium oxide (Sm_2O_3) and 4±2 mol parts of zirconium oxide (ZrO_2).