JP2505030B2 - High-permittivity porcelain composition for temperature compensation and method for producing the same - Google Patents

Description

The present invention relates to a high-permittivity porcelain composition for temperature compensation, and more particularly to a SrTiO ₃ -CaTiO ₃ -Nb ₂ O ₅ system high-permittivity porcelain for temperature compensation. It relates to improvements in compositions.

[Conventional technology]

Conventionally, it is a porcelain composition having a high dielectric constant, a high Q value, and an excellent electric breakdown voltage at the same time, and yet, the temperature coefficient of the high dielectric constant compensates for the temperature coefficient of many general electric circuits and device characteristics. Various types of high-permittivity porcelain compositions for temperature compensation have been developed.

For example, when trying to find a dielectric constant of 10 to 500 and its temperature coefficient in the range of +100 to −5000 × 10 ⁻⁶ / ° C,
_{Compositions, BaTiO 3, SrTiO 3, CaTiO} 3, MgTiO 3 or _{La 2 O 3, TiO 2,} MgO · SiO 2, Bi 2 O 3 · 2TiO 2 , etc. is selected from the composition system, generally high dielectric Rate-Small temperature coefficient-High Q
It is difficult to find a combination of values for one composition.

That is, in the above composition system, the relationship between the dielectric constant at room temperature and its temperature coefficient is such that the value of the temperature coefficient increases as the dielectric constant increases, and if the use of the temperature coefficient is prioritized, the dielectric constant will increase. The rate becomes small. Further, since the deterioration of the loss angle at high frequencies is also accompanied, even if these temperature compensating compositions can have a sufficiently small temperature coefficient, the dielectric constant having a negative temperature coefficient and the Q value combined therewith are In either case, they are considerably inferior to the electrical elements and circuit characteristics to be temperature-compensated, and they cannot fulfill the necessary and sufficient temperature compensation functions from a practical point of view.

For example, CaO-TiO ₂ -S was proposed as a high-permittivity porcelain composition for temperature compensation, which has a small temperature coefficient and can be controlled freely, and has a high dielectric constant and a high-frequency loss angle.
The iO ₂ -SrO ₂ composition has a dielectric constant of 18.4 to 145 (1MHz25
℃) is considerably low.

Further _{CaTiO 3 -Sb 2 O 3 · 2MgO} -SrO · Nb 2 O 5 based composition or CaTiO ₃ permittivity in _{-La 2 O 3 · 2TiO 2 -PbO} · TiO 3 -Bi 2 O 3 · 2TiO 2 based composition Has stopped at 100 to 180, which is not a practical range.

The present applicant previously proposed a high-permittivity porcelain composition for temperature compensation having excellent characteristics against the background of various developed high-permittivity porcelain compositions (see Japanese Patent Publication No. 56-17771).

By the way, when manufacturing such a high-permittivity ceramic composition for temperature compensation, the method shown in FIG. 7 is also common. That is, mixing SrCO ₃ , TiO ₂ and MnCO ₃ raw material as an oxidant,
After dehydration and drying, temporary forming and preliminary firing are performed and coarse pulverization is performed to complete SrTiO ₃ . Similarly, for CaCO ₃ , TiO ₂ , and MnCO ₃ raw materials, the same procedure is followed to complete CaTiO ₃ . Then, both titanates (SrTiO ₃ and CaTiO ₃ ) are mixed, dehydrated and dried to complete the desired material.

As shown in Fig. 4, the SrTiO ₃ -CaTiO ₃ based porcelain composition, which is the basis of the above composition, is
Since the value, the permittivity ε, and the temperature coefficient TC of the permittivity vary in various ways, only one characteristic was practically used.

However, the applicant's earlier invention (Japanese Patent Publication No. 56-17771)
According to Fig. 6, as shown in Fig. 6, Nb ₂ O ₅ of the third component controls the change with respect to the permittivity ε and Q value, and enables the advanced use of the characteristic properties, and the simple temperature coefficient TC. Changes can occur together. Therefore, it became possible to obtain the temperature coefficient required for the required temperature compensation in combination with a good characteristic value from this simple temperature coefficient variation range that appears stably at each composition point.

[Problems to be solved by the invention]

However, the crystal grain size of these SrTiO ₃ —CaTiO ₃ —Nb ₂ O ₅ based porcelain compositions is relatively large, usually 10 to 25 μm.

Recent dielectric elements, such as multilayer chip capacitors, are required to be small in size, large in capacity, and low in cost. For example, thicknesses of 10 μm are becoming thinner and thinner.
In order to achieve this, it is impossible with the conventional crystal grain size of 10 to 25 μm.

In addition, even if the sheet thickness per capacitor layer is 20
Even if it is ~ 30μm, it is 1 with the conventional crystal grain size.
The calculation results in 1 to 2 crystal grains per sheet. This has been a cause of causing delamination and reducing the insulation resistance and breakdown of the element.

Therefore, an object of the present invention is to provide a temperature-compensating high-dielectric-constant porcelain composition whose crystal grain size is reduced without impairing the various properties of the temperature-compensating high-dielectric-constant porcelain composition previously invented by the applicant. It is provided.

[Means for solving the problem]

In order to achieve the above object, the present invention provides SrTiO ₃ 66 to 71 wt.
%, CaTiO ₃ 29-34 wt% for 100 parts of the composition, N
b ₂ O ₅ 0.2 to 11.0 wt%, SiO ₂ 0.1 to 1.0 wt% SrTiO 3
₃ it is an -CaTiO ₃ -Nb ₂ O ₅ -SiO ₂ system for temperature compensation high dielectric constant ceramic composition.

The difference between the present invention and the previous invention by the applicant, that is, the improvement is that SiO ₂ is added to the SrTiO ₃ -CaTiO ₃ -Nb ₂ O ₅ -based temperature-compensating high-dielectric-constant porcelain composition of the present invention. The one, Si
O ₂ is added in the crushing step after the calcination of the porcelain composition raw material.

[Action]

According to the present invention, by adding a predetermined amount of SiO ₂ during fine pulverization after calcination of the porcelain composition of the previous invention, the main calcination temperature is lowered, and therefore the growth of crystal grains of the composition is suppressed,
The crystal grain size of the manufactured porcelain composition can be reduced.

〔Example〕

 An example of the present invention will be described.

Commercially available industrial raw materials SrCO ₃ , CaCO ₃ , TiO ₂ , Nb ₂ O ₅
As a starting material, SrCO ₃ , CaCO ₃ , TiO ₂ , and Nb ₂ O ₅ are weighed so that the composition after firing is as shown in Table 1 below.

Furthermore, as an oxidant to prevent reducibility during firing,
About 0.2 wt% of MnCO ₃ is added, and at the same time, oxides of rare earth metals such as CeO ₂ and La ₂ O ₃ are added as mineralizers to improve sinterability.

This raw material is wet-mixed for 20 hours in a porcelain pot mill (see FIG. 1 (a)).

Next, this mixture is dehydrated and dried, and then calcined at 1100 to 1200 ° C. for 2 hours (see FIG. 1 (b)).

Furthermore, after roughly crushing this pre-baked product, SiO ₂ was added to the above components in the amounts shown in Table 1, wet mixing was again carried out in the pot mill, and fine grinding was carried out for 20 hours (Fig. 1). (See (c)).

This is dehydrated and dried to complete the material (see FIG. 1 (d)).

After that, a binder is added to the material, and 16.5φ × 0.6tm
1240-132 by press-molding a disk of m with a pressure of about 3 tons / cm ^2.
Main calcination is performed by holding at 0 ° C. for 2 hours to obtain a porcelain composition.

Silver electrodes are baked on the obtained disk-shaped porcelain composition at 850 ° C., lead wires are soldered and washed, and then electrical characteristics are measured. The measurement conditions are room temperature 20 ° C or less, and use the Q meter (4340A) and IR meter (4329A) manufactured by Yokogawa Electric Corporation, the temperature coefficient of the dielectric constant is LCR meter 4274A, and the temperature chamber is BT-made by Elektop. 100 is used, measurement voltage AC1V, frequency 1
Measure in KHz.

Table 1 shows characteristic values and the like of porcelain compositions having different composition ratios manufactured under such manufacturing conditions. In the table, composition ratio is% by weight
The content of each composition is shown in terms of (wt%). The measurement results are: permittivity ε _S , temperature coefficient of permittivity TC, Q value, insulation resistance I
R, grain size, and sinterability.

The particle size of the powder before molding and firing of the composition is 0.5 to 1.5.
μm is desirable.

Materials marked with an X are outside the scope of the present invention.

As shown in Table 1, in the porcelain composition of the present invention, the temperature coefficient of the dielectric constant changes smoothly in the range of (−500 to −3000) × 10 ⁻⁶ / ° C., which is the optimum temperature coefficient for temperature compensation. Can be freely requested. In addition, the permittivity is maintained at 200 to 320, which is significantly higher than the conventional value of this type of porcelain composition, and the Q value is almost
The range is 1500 to 5000, and the addition of Nb ₂ O ₅ makes the insulation resistance 1 to 10 × 10 ¹¹ larger than the conventional 0.8 × 10 ¹¹ Ω.
It can be improved to the value of Ω.

Further, according to the present invention, the main calcination temperature can be lowered to 1240 to 1320 ° C. by adding SiO ₂ in the pulverizing step after the calcination. Along with that, grain growth of crystals is suppressed.

FIG. 2 shows the correlation between the firing temperature of the porcelain composition and the crystal grain size, and FIG. 3 is a photograph showing the crystal structure of the porcelain composition produced.

As is clear from FIGS. 2 and 3, according to the raw blending method of the present invention, in which SiO ₂ is added after calcination, the calcination temperature is 1280 ° C. or less, and the crystal grains of the porcelain composition produced are The diameter is as small as 2 to 5 μm. In this method, adhesion occurs when the firing temperature is 1320 ° C or higher.

On the other hand, when producing a ceramic composition by the conventional titanate method without adding SiO ₂ , if the firing temperature is 1280 ° C, it will be difficult to sinter due to insufficient burning, so it is necessary to fire at 1300 ° C or higher. Also, the crystal grain size produced is relatively large, about 15 to 25 μm. This is also clear from the photograph in FIG.

Here, the correlation between the characteristics and the composition ratio of the porcelain composition of the present invention will be examined.

FIG. 4 is a correlation diagram between the composition ratio and characteristics of the SrTiO ₃ —CaTiO ₃ based porcelain composition which is the basis of the present invention.

In Fig. 4, SrTiO ₃ is 71 wt% or more, that is, CaTiO ₃ is
When it becomes 29 wt%, the temperature coefficient of the dielectric constant becomes large and the sinterability deteriorates. On the other hand, SrTiO ₃ is 66 wt% or less, that is, CaTiO ₃
When the value is more than 34 wt%, the temperature coefficient of permittivity also increases and the Q value decreases.

This tendency is the same when Nb ₂ O ₅ and SiO ₂ are contained as in the present invention (see, for example, Table 1, Nos. ₇ and 8), SrTiO ₃ and CaTi.
It is appropriate that the composition ratio of O ₃ is SrTiO ₃ : 66 to 71 wt% and CaTiO ₃ : 29 to 34 wt%.

Next, the amounts of Nb ₂ O ₅ and SiO ₂ added will be examined.

Figure 5, Figure 6 is _{SrTiO 3: 68wt%, CaTiO 3} : is a correlation diagram between the added amount and the characteristics of the Nb ₂ O ₅ when the 32 wt%.

As is clear from FIGS. 5 and 6, when the amount of Nb ₂ O ₅ added is 0.2 wt% or less, the effect of increasing the temperature coefficient of insulation resistance and dielectric constant is not remarkable. Also, the amount of Nb ₂ O ₅ added is 11 wt%
If it becomes above, Q value will fall remarkably. And these tendencies are the same when SiO ₂ is added (for example, Table 1 N
o.11,12,17), Nb ₂ O ₅ is suitable to be added in the range of 0.2-11.0wt%. In addition, Nb ₂ O ₅ can also be used in the form of CaO · Nb ₂ O ₅ to obtain the same overall improvement effect.

Furthermore, when the amount of SiO ₂ added is 0.1 wt% or less, the effect of lowering the main firing temperature is not remarkable, and the crystal grain size does not decrease (see Table 1, Nos. 18 and 19). The amount of SiO ₂ added is 1.
When it is 0 wt% or more, the dielectric constant is remarkably reduced and it is not practical (for example, see Table 1, No. 23). Therefore, the addition amount of SiO ₂ is 0.1
〜1.0wt% is suitable.

In addition, rare earth element oxides including Mn, Cr, Sb, Fe oxides, Ce, La, etc. or one or more elements of clayey substances such as kaolin, kaolinite, pentonite, etc. Further industrial significance can be expected by relaxing the firing temperature condition of the porcelain composition.

〔The invention's effect〕

By producing a high-permittivity porcelain composition for temperature compensation with a four-component system of SrTiO ₃ -CaTiO ₃ -Nb ₂ O ₅ -SiO _{2 as in} the present invention, a high dielectric constant, a low dielectric constant temperature coefficient and a high Q are obtained. In addition to obtaining the value, it is possible to obtain a material having a fine grain size and good properties.

Moreover, the firing temperature condition of the porcelain composition can be relaxed by including the subcomponent.

Further, by adding SiO ₂ during the fine pulverization after the calcination of the raw material, the main calcination temperature is lowered, so that the growth of the crystal grains of the composition is suppressed and the crystal grain size of the porcelain composition produced is reduced. be able to.

Also, the powder particle size of the composition before the main firing is 0.5 to 1.5 μm.
With the above, it is possible to obtain a fine crystal grain having good properties.

Therefore, using this porcelain composition, it has become possible to manufacture a dielectric element, for example, a laminated multilayer chip capacitor.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the manufacturing process of the porcelain composition of the present invention, FIG. 2 is a correlation diagram of the firing temperature of the porcelain composition and the crystal grain size, and FIG. 3 is a porcelain containing the SiO ₂ of the present invention. A photograph showing the crystal structure of the composition, Fig. 4 is a correlation diagram of composition ratio and characteristics of SrTiO ₃ -CaTiO ₃ based porcelain composition, and Figs. 5 and 6 are Nb ₂ O ₅ addition amount and characteristics FIG. 7 is an explanatory view of the manufacturing process of a conventional porcelain composition, and FIG. 8 is a photograph showing a crystal structure of a conventional porcelain composition to which SiO ₂ is not added.

Claims (4)

(57) [Claims] 1. Nb ₂ O ₅ is 0.2 to 11.0 wt% and SiO ₂ is 0.1 to 1.0 wt% with respect to 100 parts of a composition comprising 66 to 71 wt% of SrTiO _{3 and} 29 to 34 wt% of CaTiO _3. A high dielectric constant porcelain composition for temperature compensation, which is added. 2. Nb ₂ O ₅ is 0.2 to 11.0% by weight and SiO ₂ is 0.1 to 1.0% by weight based on 100 parts of a composition comprising 66 to 71% by weight of SrTiO _{3 and} 29 to 34% by weight of CaTiO _3. One or two or more of rare earth element oxides and clay substances containing Mn, Cr, Sb, Fe oxides, Ce, La, etc. as auxiliary components to the composition whose main component is added. The high dielectric constant porcelain composition for temperature compensation according to claim 1, characterized in that the composition is contained. _3. Nb ₂ O ₅ is 0.2 to 11.0% by weight and SiO ₂ is 0.1 to 1.0% by weight based on 100 parts of a composition containing 66 to 71% by weight of SrTiO _{3 and} 29 to 34% by weight of CaTiO _3. In the method for producing a high-permittivity porcelain composition for temperature compensation to be added, a high-permittivity for temperature compensation, characterized in that 0.1 to 1.0% by weight of SiO ₂ is added during main pulverization after calcination of the raw material to perform main calcination. A method for producing a porcelain composition. 4. The powder particle size of the composition before the main firing is 0.5 to 1.5.
The method for producing a high-permittivity porcelain composition for temperature compensation according to claim (3), wherein the composition is μm.