JPS6236327B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high dielectric constant ceramic composition mainly containing barium titanate and having a high dielectric constant and a dense ceramic structure.

Conventional Structures and Problems There have been many known ceramic capacitor compositions based on 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 C-axis slightly stretches to become a tetragonal crystal, and furthermore, at 0°C. It changes to orthorhombic crystal at around -80℃ and to rhombohedral crystal at around -80℃. The above-mentioned phase transition point near 120°C is particularly called the Curie point, and beyond this Curie point, it exhibits paraelectricity at higher temperatures and exhibits ferroelectricity at lower temperatures. At this Curie point, the dielectric constant is approximately 10,000.
shows an extremely high value. Here, barium titanate alone cannot provide a high dielectric constant at room temperature. Furthermore, by moving the high dielectric constant of barium titanate near the Curie point to the lower temperature side, many attempts have been made to put into practical use small capacitors that have an appropriate capacitance near room temperature. Additives that shift the temperature at which the peak value of the dielectric constant appears is called a shifter, and include BaSnO ₃ , SrSnO ₃ ,
_CaSnO3 , _PbSnO3 , _CuSnO3 , _ZnSnO3 , _CdSnO3
stannates such as BaZrO ₃ , CaZrO ₃ , SrZrO ₃ , and titanates such as SrTiO ₃ and PbTiO ₃ 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 leaded types. However, with recent advances in stacking chip technology, 30 to 100μ
So-called multilayer ceramic chip capacitors, which are made by laminating many layers of this thin film with electrodes sandwiched between them, have been making their way into various electronics industries. It is increasingly being used as such a laminated thin film dielectric. however,
In conventional single-plate ceramic capacitors, the dielectric thickness is
It is thick at 100μm to 10,000μm, but thick ceramic chip capacitors are thin at 10μm to 20μm, so
~10 times more electric field 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 become more likely to appear in the characteristics, so it is desirable that the crystal grains be uniform and fine, and that the number of pores be small and small.

Against this background, the inventors of the present invention
No. 57-16809 has already developed a ceramic with a high dielectric constant, few structural defects, and low voltage dependence.
Moreover, it provides a high dielectric constant ceramic composition with high voltage resistance. That is, for 100 mole parts of BaTiO ₃ ,
This is a high dielectric constant ceramic composition consisting of 7±1 molar parts of CeO ₂ 2/3 and 7±1 molar parts of TiO ₂ .

However, with this composition, the insulation resistance was rather low and the color was bright red, and the palladium electrodes of the multilayer ceramic chip capacitor were visible through it, which caused quality problems.

OBJECT OF THE INVENTION The present invention seeks to eliminate the above-mentioned drawbacks by obtaining a higher characteristic of leading edge resistance and at the same time obtaining a high dielectric constant porcelain composition in which the palladium electrodes of a multilayer ceramic chip capacitor are not visible through the porcelain. aim at something.

Structure of the Invention In order to achieve this object, the high dielectric constant ceramic composition of the present invention contains 100 mol parts of BaTiO ₃ , GeO ₂ 2/3 (7±
1) A small amount of nickel oxide (NiO) is added to a porcelain composition consisting of a molar part and 7±1 molar part of TiO ₂ . This structure improves insulation resistance, reduces the brightness of the coloring of the porcelain, and improves quality by making the palladium electrodes of the multilayer ceramic chip capacitor invisible through the magnetism.

Description of examples The present invention will be described in detail below based on Examples.

First, barium titanate (BaTiO ₃ ) was synthesized as follows. In other words, barium carbonate (BaCO ₃ ) and titanium oxide (TiO ₂ ) are combined into [Ba]/[Ti]
Mixed with an accuracy of ratio 1.000±0.005, 1100~1150℃
After calcination, the powder was pulverized to obtain BaTiO ₃ . this
CeO ₂ 2/3 (7±1) for 100 mol parts of BaTiO ₃
molar parts and 7±1 molar parts of TiO ₂ were added, and
NiO was added and mixed in various proportions. A binder was added to this mixture, the mixture was granulated, formed into a square plate shape, and fired at a temperature in the range of 1250 to 1350°C. After this, a silver electrode was formed.

FIGS. 1A, B, and C are diagrams showing the relationship between the amount of NiO added and electrical characteristics. As is clear from FIG. 1, the dielectric constant ε in FIG. 1A tends to gradually decrease when the amount of MnO ₂ added exceeds 0.2 mole part. Also, the dielectric loss angle tan δ shown in Figure 1B is
If it exceeds 0.5 mole part, it tends to increase.
Furthermore, the insulation resistance IR shown in FIG. 1C gradually increases as the NiO content increases.

Next, trial production of multilayer ceramic chip capacitors as shown in FIG. 2 was carried out using the compositions with various amounts of NiO added as described above. In FIG. 2, numeral 1 is a dielectric with a thickness of 35 μm between electrodes, 2 is a palladium electrode, and 3 is a silver terminal electrode.

FIGS. 3A, B, and C show the relationship between the amount of NiO added and the electrical characteristics of such multilayer ceramic chip capacitors. Furthermore, the shaded area indicates the range where the palladium electrode can be seen through the 35 μm thick dielectric layer. As is clear from FIG. 3, the dependence on the amount of NiO added is relatively large compared to the electrical characteristic values of the square plate shown in FIG. First, when more than 0.2 mol part of NiO is added, the dielectric constant ε is extremely reduced as shown in FIG. 3A, but within 0.2 mol part, the dielectric constant ε hardly changes. Furthermore, as shown in FIG. 3B, the insulation resistance IR at 0.2 mol part is about 5 times that of the case without NiO addition. Furthermore, as shown in FIG. 3C, the dielectric loss angle tan δ becomes large at 0.3 molar parts or more.

From the above results, the range of the optimal amount of NiO to be added is limited to between 0.05 mol parts, at which the palladium electrode is not visible, and 0.2 mol parts, at which the dielectric constant begins to drop suddenly.

Incidentally, the grain size was on average 2 to 3 μm throughout the Examples, and the grain size was also 2 to 3 μm or less.

Effects of the Invention From the above, the composition of the present invention
Similar to the composition of No. 57-16809, the grains are fine,
It has the advantage of being able to produce small, dense ceramics with fewer pores.
No. 16809 can provide a significant improvement in insulation resistance and a multilayer ceramic chip capacitor made of ceramic in which the palladium electrodes cannot be seen through. In particular, it is extremely effective as a dielectric composition for multilayer ceramic chip capacitors with Y5V characteristics according to the EIA standard, and its industrial value is great.

Although barium titanate was synthesized in the examples, it is of course possible to use commercially available barium titanate.

[Brief explanation of the drawing]

Figures 1A, B, and C relate to compositions of the invention.
Figure 2 is a cross-sectional view of a multilayer ceramic chip capacitor to which the composition of the present invention is applied; Figures A, B, and C are diagrams showing the amount of NiO added and the characteristics of the rectangular plate dielectric. FIG. 3 is a diagram showing the amount of addition and the characteristics of a multilayer ceramic chip capacitor.

Claims (1)

[Claims] 1 100 mol parts of barium titanate (BaTiO ₃ ), 2/3 (7±1) mol parts of cerium oxide (CeO ₂ ), 7±1 mol parts of titanium oxide (TiO ₂ ), and 0.05 to 0.2 mol of nickel oxide (NiO). A high dielectric constant porcelain composition consisting of parts.