JP2676778B2 - Dielectric porcelain composition - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention has high dielectric constant, insulation resistance and breakdown voltage,
The present invention relates to a dielectric ceramic composition which is excellent in goodness Q, has a small temperature coefficient, and is not easily affected by fluctuations in firing temperature.

2. Description of the Related Art Conventionally, the following systems have been known as dielectric ceramic compositions.

La ₂ O ₅ −2TiO ₂ −CaTiO ₃ −2MgO−TiO ₂ system TiO ₂ −BaTiO ₃ −Bi ₂ O ₅ −La ₂ O ₅ system BaTiO ₃ system SrTiO ₃ system CaTiO ₃ system SrTiO ₃ −CaTiO ₃ system MgTiO ₃ system SrTiO ₃ —CaTiO ₃ —Nb ₂ O ₅ system Problems to be solved by the invention However, one of these compositions has a high dielectric constant, a small temperature coefficient, excellent goodness, and is hardly affected by fluctuations in firing temperature. It is impossible to satisfy all.

Further, those containing Bi ₂ O ₅ have a problem that Pb cannot be used as the internal electrodes of the laminated ceramic capacitor.

Therefore, an object of the present invention is to obtain a dielectric porcelain composition having a high dielectric constant, insulation resistance and dielectric breakdown voltage, excellent satisfactorily, a small temperature coefficient and being hardly affected by fluctuations in firing temperature.

When SUMMARY OF invention in order to solve this problem, which represents the general formula xSrO-yCaO-Z _{[(TiO 2) (1-m} ) · (ZrO 2) m ], however, x + y + z = 1.00 0.01 ≤ m ≤ 0.20 The main component is the range of molar ratios where x, y, z are represented by the points a, b, c, d shown in the table below, and Nb as a sub-component to this main component
A dielectric ceramic composition containing 0.1 to 10.0% by weight of ₂ O ₅ .

Function According to this structure, by replacing TiO ₂ with ZrO ₂ , the insulation resistance can be increased, the fluctuation of the temperature coefficient due to the firing temperature can be reduced, and Nb ₂ O ₅ increases the breakdown voltage. The resistance and dielectric breakdown voltage are high, the Q is excellent, the temperature coefficient is small, and it is not easily affected by fluctuations in firing temperature.

Examples Hereinafter, the present invention will be described with reference to specific examples.

Example 1 As a starting material, chemically high purity SrCO ₃ , CaCO ₃ , TiO ₂ , and ZrO were used.
₂ , Nb ₂ O ₅ powder was weighed so as to have the composition shown in Table 1 below, put into a rubber-lined ball mill equipped with agate balls together with pure water, and wet-mixed for 20 hours. This mixture was dehydrated and dried, and then calcined at 1100 ° C. for 2 hours. After the coarse pulverization, the mixture was again put in a rubber-lined ball mill equipped with agate balls together with pure water and wet-pulverized for 20 hours.
The pulverized product was dehydrated and dried, and then 9% by weight of a polyvinyl alcohol aqueous solution having a concentration of 5% was added as a binder to the powder to homogenize it, and the powder was sized through a 32 mesh sieve. Next, this sized powder was molded into a diameter of 15 mm and a thickness of 0.4 mm at a molding pressure of 1 ton / cm ² using a die and a hydraulic press, and then this molded product was filled with ZrO ₂ powder to form a high-purity alumina box. The mixture was placed in a pot and fired in the air at the temperature shown in Table 1 below for 2 hours to obtain a dielectric porcelain having the composition shown in Table 1 below.

The electrical characteristics of these samples were as follows: silver electrodes were baked on both sides of the samples, and the dielectric constant, goodness Q, and temperature coefficient were measured using Yokogawa Hewlett-Packard Co., Ltd. Digital LCR meter model 4275A. , Measurement voltage 1.0 Vrms, measurement frequency 1
Obtained by measurement in MHz. The temperature coefficient was calculated from the following equation with the capacity value at 20 ° C. as a reference.

Temperature coefficient = (C _{85 ℃} -C _{20 ℃} ) / (C _{20 ℃} × 65) × 10 ⁶ (ppm / ℃) Insulation resistance is Yokogawa / Hewlett-Packard Co. HR meter model 4329A. , Measuring voltage DC5
It was determined by measurement at 0 V and a measurement time of 1 minute. Furthermore, the breakdown voltage is the high voltage power supply PHS35K-3 from Kikusui Electronics Co., Ltd.
Using the shape, the breakdown voltage obtained at a boosting rate of 50 V / sec was divided by the element thickness to obtain the breakdown voltage value per unit length. Table 1 also shows these test conditions and results.

Here, FIG. 1 is a triangular diagram showing the composition range of the main component of the composition according to the present invention, and the reason why the composition range of the main component is limited will be described with reference to the drawing. That is, area A and C
In the region, the temperature coefficient becomes too large on the (-) side, which is not practical. Further, in the B region and the D region, it becomes difficult to sinter, and the dielectric constant, the goodness Q, and the insulation resistance decrease.

2 and 3 replace a part of TiO _{2 in} the main component
Is a graph showing the effect of ZrO ₂ ratio m, will be described with reference to graph the reason for limiting the substitution range of ZrO _2. First, by substituting a part of TiO ₂ with ZrO ₂ , it has the effect of increasing the insulation resistance as shown in FIG. 2 and reducing the temperature coefficient fluctuation due to the firing temperature as shown in FIG. If the replacement rate m is less than 0.01, there is no replacement effect, while
If it exceeds 0.2, it becomes difficult to sinter, and the dielectric constant, goodness Q, and insulation resistance decrease.

FIG. 4 is a graph showing the effect of the inclusion of Nb ₂ O ₅ as an auxiliary component added as a proportion to the main component. The reason for limiting the content range of Nb ₂ O ₅ is shown in the graph. explain. First, as shown in FIG. 4, by containing Nb ₂ O ₅ , it has the effect of increasing the breakdown voltage. If the content is less than 0.1 wt% with respect to the main component, there is no effect, and conversely 1
When it exceeds 0.0% by weight, the goodness Q is lowered and the temperature coefficient is increased to the (-) side, which is not practical.

(Example 2) The starting material chemically high purity _{SrCO 3, CaCO 3, TiO 2} , ZrO
₂ , Nb ₂ O ₅ , MnO ₂ , FeO, NiO, CoO and SiO ₂ powders were weighed so as to have the composition shown in Table 2 below, and thereafter treated in the same manner as in the above (Example 1). Then, a dielectric ceramic composition having the composition shown in Table 2 was obtained.

The test method for these samples is the same as in (Example 1), and the test conditions and results are also shown in Table 2.

In this embodiment also includes (Embodiment 1) of the dielectric ceramic composition, manganese, chromium, iron, nickel, at least one of each MnO selected from among cobalt and the group consisting of oxides of silicon ₂ , Cr ₂ O ₅ , FeO, NiO, CoO and SiO ₂
It is a composition containing 0.05 to 1.00% by weight based on the main component. These additives have the effect of improving the sinterability of porcelain. If the amount of addition is less than 0.05% by weight, there is no addition effect, and if it exceeds 1.00% by weight, the dielectric constant decreases.

EFFECTS OF THE INVENTION According to the present invention, by replacing TiO ₂ with ZrO ₂ , it is possible to increase the insulation resistance and reduce the variation of the temperature coefficient due to the firing temperature, and Nb ₂ O ₅ increases the breakdown voltage, so that the dielectric It is possible to obtain a dielectric ceramic composition having a high rate, a high insulation resistance, a high dielectric breakdown voltage, an excellent Q, a low temperature coefficient, and a low effect of fluctuations in firing temperature.

Further, the obtained dielectric porcelain composition has a high dielectric constant, so that the element body can be made extremely small, and it is effective for miniaturization of the circuit. Particularly, by making it into a thin plate shape, a laminated ceramic capacitor, It is suitable for applications such as hybrid microcircuits.

[Brief description of the drawings]

Figure 1 is a triangular diagram showing the composition range of the main component containing 1 wt% Nb ₂ O ₅ as an auxiliary component according to the present invention, Figure 2 is a 1 wt% Nb ₂ O ₅ as an auxiliary component according to the present invention contains, when expressed with the general formula xSrO-yCaO-Z of the main component _{[(TiO 2) (1-m} ) · (ZrO 2) m ], x = 0.30, y = 0.19 , and z = 0.51, ZrO ₂ 3 is a graph showing changes in temperature characteristics when the substitution ratio m of is changed to 0.25. FIG. 3 contains 1 wt% Nb ₂ O ₅ as a sub-component according to the present invention and has the general formula xSrO-yCaO. When expressed as −Z [(TiO ₂ ) _(1-m)・ (ZrO ₂ ) _m ], x = 0.30, y = 0.19, z = 0.51, the substitution ratio m of ZrO ₂ was changed to 0.25, and Firing temperature 1340 ~
FIG. 4 is a graph showing changes in temperature characteristics when the temperature was changed up to 1380 ° C., and FIG. 4 shows the general formula xSrO-yCaO-Z [(TiO ₂ ) _(1-m). (ZrO ₂ ) _m ] Is a graph showing changes in characteristics when x = 0.30, y = 0.19, z = 0.51, m = 0.05 and the content of the subcomponent Nb ₂ O ₅ is changed to 15% by weight. .

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Takashi Iguchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP 60-131708 (JP, A) Japanese Patent Publication 45- 4458 (JP, B2) JP 45-4460 (JP, B2) JP 45-27627 (JP, B2)

Claims (2)

(57) [Claims] 1. When represented by the general formula xSrO-yCaO-Z [(TiO ₂ ) _(1-m). (ZrO ₂ ) _m ], where x + y + z = 1.00 0.01 ≦ m ≦ 0.20 x, y, z The main component is the range of molar ratios surrounded by points a, b, c, and d shown in the table below.
A dielectric ceramic composition containing 0.1 to 10.0% by weight of ₂ O ₅ . 2. At least one selected from the group consisting of oxides of manganese, chromium, iron, nickel, cobalt and silicon is added to MnO ₂ , Cr ₂ O ₅ , FeO, NiO, CoO and Si, respectively.
The dielectric porcelain composition according to claim 1, which is contained in an amount of 0.05 to 1.00 wt% with respect to the main component in terms of O ₂ .