JPS6051202B2 - High dielectric constant porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 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 ART Many ceramic capacitor compositions based mainly on barium titanate have been known.

As is well known, barium titanate is a unique ferroelectric substance that has a cubic perovskite structure at high temperatures, and below 120°C, the C-axis slightly stretches to become a tetragonal crystal, and furthermore, the 0' It changes to orthorhombic crystal around C and rhombohedral crystal around -80'C. The above-mentioned phase transition point near 120° C. is called the Curie point, and the material exhibits paraelectricity at higher temperatures beyond the Curie point, and exhibits ferroelectricity at lower temperatures. and,
At this Curie point, the dielectric constant exhibits an extremely high value of approximately 10,000. Here, barium titanate alone cannot provide a high dielectric constant at room temperature. Many attempts have been made to commercialize small capacitors with appropriate capacitance near room temperature by moving the high dielectric constant of barium titanate near its Curie 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 BaSnO3, srsno3, cas
no3, PbSnO3, cusno3, Znsno3,
stannates such as CdSnO3, BaZrO3, ca2ro
3, zirconate such as sr2ro3 and SrTiO3
, PbTiO3 titanates 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, recently, stacked chip technology has progressed, and 30 to 100
Dielectric sheets of about μm size can be easily obtained, and so-called multilayer ceramic chip capacitors, in which many layers of these thin films are laminated with electrodes sandwiched between them, have entered various electronics industries, and conventional dielectric ceramic compositions have been replaced by multilayer ceramic chip capacitors. It is increasingly being used as such a thin film dielectric for lamination. Although he is a sumo wrestler, the dielectric thickness of conventional single-plate magnetic capacitors is as thick as 100 μL to 10,000 μL.
For laminated ceramic chip funda, 10 μL to 20
Because it is as thin as μm, it receives an electric field strength of 5 to 1 pm 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 occur, so it is required that the crystal grains be uniform and fine, and that the pores be small and small. There is. In view of the above, and as a result of various experiments, the present invention has been able to provide a high dielectric constant ceramic composition that has a high dielectric constant, has few ceramic structural defects, has low voltage dependence, and has a high withstand voltage.

Hereinafter, the present invention will be described in detail based on examples.

First, barium titanate (BaTiO3) was synthesized as follows.

That is, barium carbonate (BaCO3) and titanium oxide (
TlO2) [? ]/[Ti)zo) ratio is 1.000±0
．． The mixture was mixed with a precision of 0.05 C, calcined at 1100 to 11500 C, and then ground.

Add CeO2 and TiO2 to this BaTiO3 [Ce]
/ [Ti] ÷ 1 cup of Ti and after mixing,
Add a binder and granulate it, form it into a square plate shape and make 1250
It was fired in the range of ~1350°C. After this, a silver electrode was formed. Table 1 below shows the characteristics of each composition at each firing temperature.

As is clear from the above table, composition NO. It can be seen that 2, 3, 4, and 4 can be used as EIA standard Y5■ characteristics.

In other words, as shown in the detailed capacitance change rate in Figure 1, it fully satisfies the standard change rate of +22% to -82% (20℃ standard) in the temperature range of -30℃ to +85℃, and Acid electric rate 1 of commonly commercially available Y5 ■ characteristic porcelain capacitors
It shows the same dielectric constant as that of around 0000. At the end of Table 1, a Y5V characteristic composition containing a zirconate salt 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, but in the conventional example, the grain size is as large as 10 to 20 μm, and the maximum bore size is around 20 μm. Composition NO. 3
We prototyped a multilayer ceramic chip capacitor as shown in Figure 2.

Table 2 below shows the results of a comparison between this * and a zirconate-based multilayer ceramic chip capacitor.
In Figure 2, A is a dielectric and the thickness between the electrodes is 35μ.
M. ．． B is a palladium electrode, and C is a silver terminal electrode. As is clear from Table 2 above, the bending strength is twice that of the conventional one, and 3
It was found that the breakdown voltage was twice as high.

From the above, the composition of the present invention can be used for magnetic capacitors with fine grains, small bores, small and dense ceramics, high dielectric constant, and temperature change in dielectric constant satisfying EIA standard Y5■ characteristics. In particular, it can be used as a multilayer ceramic chip capacitor.

Since the breakdown voltage value is approximately three times that of conventional capacitors, the dielectric thickness of multilayer ceramic chip capacitors has been reduced to one level compared to conventional ones.
It has extremely high industrial value because it can be made as thin as B, and the capacitance acquisition range can be expanded to three times that of the conventional method. 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 diagram showing a cross-sectional view of a multilayer ceramic chip capacitor to which the composition/product of the present invention is applied.

Claims (1)

[Claims] 1. A high dielectric constant ceramic composition comprising 100 mol parts of barium titanate (BaTiO_3), 2/3 (7±1) mol parts of cerium oxide (CeO_2), and 7±1 mol parts of titanium oxide (TiO_2).