JPH04295048A - Dielectric porcelain composition having high dielectric constant - Google Patents

Abstract

PURPOSE:To obtain a dielectric porcelain compsn. having a high dielectric constant, hardly undergoing a change in the capacitance over a wide temp. range and also having a small dielectric loss and superior characteristics. CONSTITUTION:This dielectric porcelain compsn. contains 94.0-99.0mol% BaTiO3 0.5-3.0mol% Nb2O5 and 0.5-3.0mol% CoO as essential components, and further contains 0.2-7.0wt.% one or more among CaZrO3, SrZrO3 and BaZrO3 basing on the total amt. of the essential components.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a high dielectric constant dielectric ceramic composition, and particularly relates to a wide temperature range (-55°C to +150°C).
) The present invention relates to a high dielectric constant dielectric ceramic composition having excellent characteristics such as small change in capacitance and low dielectric loss.

0002

[Prior Art] Conventionally, barium titanate (Ba
TiO3) with a bismuth compound, e.g. Bi2O3
・2SnO2 and Bi2O3 ・2ZrO2 and Ta
2 O5, Nb2 O5, etc. were added to reduce the rate of temperature change.

0003

[Problems to be Solved by the Invention] However, when the dielectric constant of a composition containing these components is increased, the rate of change in capacitance with temperature increases, and there is a natural limit to increasing the dielectric constant. For this reason, when these compositions were used in capacitors, it was difficult to obtain large capacitance with a small size.

[0004] Furthermore, compositions containing bismuth compounds have the problem that the bismuth component evaporates during firing, causing the porcelain composition body to bend.

Furthermore, when a barium titanate multilayer ceramic capacitor containing bismuth is produced, the palladium or silver-palladium alloy that is the internal electrode reacts with bismuth that is a dielectric component, and the function as an electrode is caused. Therefore, expensive platinum must be used for the internal electrodes, which increases the cost of multilayer ceramic capacitors.

[0006] Accordingly, an object of the present invention is to provide a high dielectric constant dielectric ceramic composition which has excellent characteristics such as small change in capacitance over a wide temperature range and low dielectric loss.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present inventors have conducted intensive research and found that BaT is the main component.
iO3: 94.0-99.0 mol% Nb2O5
:0.5 to 3.0 mol%CoO :0
．． 5 to 3.0 mol%, CaZ as an additive
It has been found that by containing 0.2 to 7.0% by weight of one or more of rO3, SrZrO3, and BaZrO3, the Curie point can be shifted to the high temperature side. This makes it possible to expand the region where the capacitance changes little with temperature.

[0008] Also, if necessary, La2 O3, Nd2
0.5 of one or more of O3, Pr6, O11
It has been found that the properties are excellent when the content is less than % by weight.

Furthermore, by containing 0 to 0.3% by weight of MnO and 0 to 0.3% by weight of SiO2, the sinterability is improved and the properties are further improved.

0010

[Function] By using the dielectric ceramic composition of the present invention, it has a high dielectric constant of 2000 to 4700 at room temperature, and the dielectric loss (tan δ) is 1.2%.
It is a small value of less than EI, and the temperature change in capacitance is EI
It satisfies the ×7R characteristic (change in capacitance within ±15% with respect to 25°C in the temperature range of -55°C to +125°C) stipulated by AJ (Japan Electronics Industry Association regulations), and also ×
It is possible to obtain a high dielectric constant dielectric ceramic composition with excellent characteristics that satisfies the 8R characteristics (change in capacitance within ±15% with respect to 25°C in the temperature range of -55°C to +150°C). .

[0011]

[Embodiment] An embodiment of the present invention will be explained using FIGS. 1 to 3. Figure 1 is a ternary composition diagram of the main components of the dielectric ceramic composition of the present invention, Figure 2 is a manufacturing process diagram of the dielectric ceramic composition of the present invention, and Figure 3 is the temperature characteristic curve of capacitance of each sample. show.

As a starting material for forming BaTiO3, highly purified BaCO3 and TiO2 are prepared in a molar ratio of 1:1, and the prepared starting material is subjected to dehydration and drying treatment (see ◯ in FIG. 2).

[0013] Next, these raw materials were temporarily formed and heated to 1000°C.
Stabilize at ~1200°C for 2 hours to carry out a chemical reaction,
Calcination is performed to form BaTiO3, and the obtained Ba
TiO3 is pulverized using, for example, an atomizer (see ■ in FIG. 2).

[0014] The obtained BaTiO3 powder or the BaTiO3 powder prepared by the solution method, Nb2O
5, CoO, CaZrO3, SrZrO3, Ba
ZrO3, Nd2O3, La2O3, Pr6
O11, MnCO3, SiO2, etc. were weighed and wet mixed so that the composition after firing was as shown in Tables 1 and 2.
Dehydrate and dry (see ■ in Figure 2).

[0015]

[Table 1]

[0016]

[Table 2]

[0017] In Tables 1 and 2, each sample number is the same. Add an appropriate amount of organic binder to these raw materials and mold at a molding pressure of about 3 tons/cm2 to a diameter of 16
．． A disc-shaped molded product with a diameter of 5 mm and a thickness of approximately 0.6 mm is prepared. This molded product is stabilized at 1240° C. to 1380° C. for 2 hours and then subjected to main firing (see ■ in FIG. 2).

Silver electrodes are baked on both end faces of the obtained ceramic composition element to form a capacitor (see ■ in FIG. 2).

The electrical characteristics of these capacitors were measured. In other words, the relative permittivity and dielectric loss are calculated at a frequency of 1 KHz and 1
V, and the insulation resistance is D. at room temperature of 20°C. C. 500V
, the measured value was obtained after 1 minute at room temperature at 20°C, and the temperature change rate of capacitance (in Table 3, the capacitance change rate is shown as ΔC/C25°C to simplify the display) is - relative to the value at 25°C.
The rate of change in value at 55°C, +125°C, and +150°C was determined (see ■ in Figure 2).

Table 3 shows the results of each measurement.

[0021]

[Table 3]

[0022] In Table 3, sample No. 1 marked with an
3, 3-4, 3-9, 3-14, 3-17, 3-18,
3-19, 3-20, 3-21, 3-22, 3-23
, 6, 8, and 10 are not included in the scope of the present invention and are shown for comparison with examples of the present invention.

Furthermore, the sample numbers in Table 3 are the same as those in Tables 1 and 2. As is clear from Tables 1 to 3, the dielectric ceramic composition of the present invention has a relative permittivity of 2000 to 2000.
A high value of 4700 and a dielectric loss of 1.2%
It is a small value of less than EI, and the temperature change in capacitance is EI
It is a stable dielectric ceramic composition that satisfies not only the ×7R characteristics specified by AJ but also the ×8R characteristics.

FIG. 1 is a ternary composition diagram of the main components of the dielectric composition of the present invention. The numbers of each point in Figure 1 are shown in Tables 1 to 3.
It matches the sample number in .

From FIG. 1, the main components of the present invention are points 2, 7, 5,
It is clear that the composition will be the inside of the quadrilateral formed by the line connecting 9.

FIG. 3 shows the capacitance temperature characteristic curves of three samples among the samples shown in Tables 1 to 3. In FIG. 3, a curve A connecting points Δ shows the capacitance temperature characteristic cube of sample No. 1 in Tables 1 to 3, and a curve B connecting points Δ similarly shows sample No. 1.
Curve C connecting o3-1 and point x shows each curve of sample No.3-4.

As is clear from FIG. 3, the curve B of sample No. 3-1 is -55°C to +125°C and -55°C to +150°C.
The rate of change in capacitance with temperature is within ±15%, satisfies the ×7R characteristics and ×8R characteristics stipulated by EIAJ, and the temperature change in dielectric constant is small over a wide temperature range.

Next, the reasons for limiting the composition range of the dielectric composition of the present invention will be explained with reference to Tables 1 to 3, FIGS. 1 and 3.

[0029] If BaTiO3 is less than 94.0 mol%, the dielectric constant will be low (for example, sample N in Tables 1 to 3).
(See o6).

[0030] When BaTiO3 exceeds 99.0 mol%, the rate of change in temperature characteristics of dielectric loss (tan δ) and capacitance increases, and sinterability also deteriorates (for example, Tables 1 to 3).
, see sample No. 1 in FIG. 3).

[0031] When Nb2O5 is less than 0.5 mol%, the temperature change rate of dielectric loss and capacitance increases,
Sinterability also deteriorates (for example, Tables 1 to 3, sample No. 3 in Figure 3).
(see 1).

[0032] When Nb2O5 exceeds 3.0 mol%, the dielectric constant becomes low (see, for example, sample No. 6 in Tables 1 to 3), and the temperature change rate of capacitance increases (for example, see Tables 1 to 3). (See sample No. 8 in Table 3).

[0033] If CoO is less than 0.5 mol%, the dielectric loss and the temperature change rate of capacitance will increase, and the sinterability will also deteriorate (for example, Tables 1 to 3, Sample No. 1 in Figure 3).
reference).

[0034] When CoO exceeds 3.0 mol%, the dielectric constant becomes low (for example, sample No. 6 in Tables 1 to 3,
10), and the temperature change rate of capacitance increases (for example, see sample No. 10 in Tables 1 to 3).

[0035] As additives, CaZrO3, SrZr
One or more of O3 and BaZrO3 is 0
．． If it is less than 2% by weight, the temperature change rate of capacitance becomes large, and the ×7R characteristics and ×8R characteristics are not satisfied (for example, see samples No. 3, 3-18, and 3-20 in Tables 1 to 3).
.

[0036] Also, CaZrO3, SrZrO3,
If one or more of BaZrO3 exceeds 7.0% by weight, the rate of change in capacitance with temperature increases, and the ×8R characteristic is no longer satisfied (for example, Tables 1 to 3).
, see sample Nos. 3-4, 3-19, and 3-21 in FIG. 3).

Furthermore, Nd2 O3, La2 O3,
There is no problem in use even if Pr6O11 is not added to the above composition (for example, sample Nos. 3-7 and 3 in Tables 1 to 3).
-12, 3-24, 3-25, 3-26).

However, these Nd2 O3, La2
One or more of O3, Pr6, O11 is 0
．． Addition of up to 5% by weight improves sinterability (for example,
(See 3-8, 3-10, 3-11 in Tables 1 to 3), 0.
If it exceeds 5% by weight, the rate of change in capacitance with temperature becomes large, and the ×8R characteristic is lost (for example, see Sample Nos. 3-9, 3-22, and 3-23 in Tables 1 to 3).

Regarding the addition of MnO, there is no problem in use even if it is not added (for example, see sample No. 3-12 in Tables 1 to 3), but addition of up to 0.3% by weight prevents reduction and reduces dielectric loss. improved, and the sinterability is also improved (for example, Table 1
~See sample No. 3-13 in Table 3).

If MnO exceeds 0.3% by weight, the temperature change rate of capacitance increases, sinterability deteriorates, and dense porcelain cannot be obtained (for example, sample N in Tables 1 to 3
(See o3-14).

Regarding the addition of SiO2, there is no problem in use even without it (for example, sample No. 3 in Tables 1 to 3
-15), addition of up to 0.3% by weight improves sinterability and improves properties.

[0042] When SiO2 exceeds 0.3% by weight,
Not only does the temperature change rate of capacitance increase, but also properties such as dielectric loss deteriorate, and sinterability also deteriorates (for example,
(See sample No. 3-17 in Tables 1 to 3).

[0043] Also, alkali metal oxides contained in the raw materials or trace amounts of Si as impurities mixed in during the manufacturing process.
O2 and Al2 O3 do not significantly deteriorate the characteristics.

[0044]

Effects of the Invention The dielectric ceramic composition of the present invention has a high dielectric constant of about 2000 to 4700, a small dielectric loss of 1.2% or less, and a change in capacitance with temperature. The dielectric constant satisfies the ×7R characteristics and ×8R characteristics stipulated by EIAJ, and the change in dielectric constant is small over a wide temperature range. A dielectric ceramic composition with such excellent properties can be used, for example, in the engine room of an automobile.

Furthermore, since the dielectric ceramic composition of the present invention does not contain bismuth, which easily reacts with palladium or silver-palladium alloy, when manufacturing a multilayer capacitor using this composition as a dielectric layer, palladium is used as the internal electrode. It is possible to use it alone or as a silver-palladium alloy.

Therefore, there is no need to use expensive platinum or platinum-palladium alloys, and the cost of the product can be significantly reduced, resulting in immeasurable industrial benefits.

[Brief explanation of the drawing]

FIG. 1 is a ternary composition diagram of the main components of the dielectric ceramic composition of the present invention.

FIG. 2 is an explanatory diagram of the manufacturing process of the dielectric ceramic composition of the present invention.

FIG. 3 is a temperature characteristic curve of capacitance of a sample.

Claims (4)

[Claims] Claim 1: Main component: BaTiO3: 94.0 to 99.0 mol% Nb2O
5: 0.5 to 3.0 mol%CoO
:0.5 to 3.0 mol%, and 0.2 to 7.0% by weight of one or more of CaZrO3, SrZrO3, and BaZrO3 as additives. constant dielectric porcelain composition. 2. The composition contains La2 O3 and Nd2.
Claim 1 characterized in that it contains 0.5% by weight or less of any one or more of O3, Pr6, O11.
The high dielectric constant dielectric ceramic composition described above. 3. 0.3% by weight of MnO in the above composition.
Claim 1 or Claim 2 characterized by comprising the following:
The high dielectric constant dielectric ceramic composition described above. 4. Claims 1 and 2, wherein the composition contains 0.3% by weight or less of SiO2.
Or the high dielectric constant dielectric ceramic composition according to claim 3.