JPS6051206B2 - High dielectric constant porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is particularly applicable to barium titanate (BaTiO0), which is used as a thin film dielectric material such as multilayer ceramic capacitors.
The present invention relates to a high-permittivity ceramic composition having a high dielectric constant and a dense ceramic structure mainly consisting of:

Conventional Structures and Their Problems Many ceramic capacitor compositions based on barium titanate have been known in the past.

As is well known, barium titanate is a unique substance with ferroelectric properties, and at high temperatures it has a cubic perovskite structure.At temperatures below 120°C, the C-axis slightly stretches to become a tetragonal crystal, and furthermore, at temperatures of 0° It changes to orthorhombic crystal at around C, and to rhombohedral crystal at around -80°C. The 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. At this cue 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 near the Curie point of barium titanate to the lower temperature side,
BACKGROUND ART Numerous attempts have been made to put into practical use small capacitors that have an appropriate capacitance near room temperature. The additive that shifts the temperature at which the peak value of the dielectric constant occurs is called a shifter, and BaSnO3, srsno3, casn
oaNpbsno3, cusno3, Znsno3, C
stannate such as dSnOa, Ba2roa) ca2ro3
, zirconates such as sr2ro3 and SrTiO3,
Titanate salts of PbTiO3 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 stacked chip technology, 30 to 100μ
So-called multilayer ceramic chip capacitors, which are made by laminating many layers of thin films with dielectric sheets sandwiching electrodes, are making their way into 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 100μm~10000P771, but in multilayer ceramic capacitors it is 10μ~20μm thick.
Because it is as thin as 1 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 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, an object of the present invention is to provide a high dielectric constant ceramic composition that has a high dielectric constant, has few ceramic structural defects, has low voltage dependence, has few ceramic structural defects, and has a high withstand voltage. It is something.

Structure of the Invention The present invention utilizes barium titanate (BaTlO3), disprosium oxide (Dy2O3) and titanium oxide (TiO3).
2) is a high dielectric constant ceramic composition.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be explained in detail.
** First, barium titanate (BaTiO3) was synthesized as follows. That is, barium carbonate (BaCO
3) and titanium oxide (TiO2)/[TO ratio is 1
．． 000+. Mix with an accuracy of 0.005, 1100-1
It was obtained by calcining at 1500C and pulverizing.

Add Dy2O3 and TiO2 to this BaTiO3 [Dy
]/[Ti] at a ratio of 10, 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 Table 1 above,
Composition No. It can be seen that 2, 3, and 4 can be used as EIA standard Y5V 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 generally Dielectric constant 1 of commercially available Y5V characteristic ceramic capacitors
It shows the same dielectric constant as compared to the one after 000. At the end of Table 1, as a conventional example, zirconate-added Y
5V characteristic composition was shown. The grain size (particle size) of the ceramic is 1 to 3 μm in the composition of the present invention, and the maximum pore size is around 3 μm, but in the conventional example, the grain size is as large as 10 to 20 μm. The maximum bore size is around 20 μm.A multilayer ceramic capacitor with composition No. 3 as shown in FIG. 2 was fabricated as a prototype.

The results of a comparison between this and a zirconate-based multilayer ceramic capacitor are shown in Table 2 below. In FIG. 2, 1 is a dielectric, and the thickness between the electrodes is 35prr1. ,
2 is a palladium electrode, and 3 is a terminal electrode. 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 provides a dense ceramic with fine grains and a small bore.
High dielectric constant, temperature change in dielectric constant is EIA standard Y5V
It can be used as a ceramic capacitor that satisfies the characteristics, especially as a multilayer ceramic capacitor.

Since the breakdown voltage value is approximately three times that of conventional capacitors, the dielectric thickness of multilayer ceramic capacitors can be reduced to about 1B compared to conventional capacitors, expanding the capacitance acquisition range to three times that of conventional capacitors. Its industrial value is extremely high, as it has the characteristics of being able to Although barium titanate was synthesized in the above example, commercially available barium titanate may also be used.

- Brief Description of the Drawings Figure 1 is a diagram showing the range of temperature change rate of capacitance for the composition of the present invention, and Figure 2 is a cross-sectional view of a multilayer ceramic capacitor to which the composition of the present invention is applied.

Claims (1)

[Claims] 1 100 mol parts of barium titanate (BaTiO_3), 1/3 (7 molar parts) of disprosium oxide (Dy_2O_3)
A high dielectric constant ceramic composition consisting of ±1) molar parts and 7±1 molar parts of titanium oxide (TiO_2).