JPH04292459A - Dielectric ceramic composition having high dielectric constant - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic composition having high dielectric constant and excellent characteristics comprising small temperature dependence of dielectric capacity over a wide temperature range and low dielectric loss. CONSTITUTION:The objective dielectric ceramic composition having high dielectric constant contains 94.0-99.0mol% of BaTiO3, 0.5-3.0mol% of Nb2O5 and 0.5-3.0mol% of CoO as main components and further contains 0.2-7.0wt.% of SrZrO3 as an additive.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a high dielectric constant dielectric ceramic composition, particularly over a wide temperature range (-55°C to +150°C).
The present invention relates to a high dielectric constant dielectric ceramic composition that has a small change in capacitance and a small 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, Sm2 O3, etc. are added to reduce the rate of temperature change.

0003

However, in compositions containing these components, increasing the dielectric constant increases the rate of change in capacitance, 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.

Among the above-mentioned compositions, those containing a bismuth compound have the problem that the bismuth component evaporates during firing, resulting in bending of the porcelain composition body.

Furthermore, when a barium titanate multilayer ceramic capacitor containing bismuth is manufactured, the palladium or silver-palladium alloy that is the internal electrode reacts with bismuth, which is a dielectric component, and loses its function as an electrode. . For this reason, expensive noble metals such as platinum must be used for the internal electrodes, which has been a factor in increasing the cost of multilayer ceramic capacitors.

[0006] Accordingly, an object of the present invention is to provide an excellent high dielectric constant ceramic composition which exhibits little 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 inventors of the present invention have conducted extensive research and found that BaTi is the main component.
O3: 94.0 to 99.0 mol% Nb2 O5
: 0.5 to 3.0 mol% CoO : 0
．． 5 to 3.0 mol%, SrZr as an additive
It has been found that the Curie point shifts to the high temperature side by containing 0.2 to 7.0% by weight of O3. This expands the area where the capacitance changes little with temperature.

[0008] Also, if necessary, add 0.5 Nd2 O3.
It has been found that the properties are excellent when the content is less than % by weight.

Furthermore, it has been found that by adding 0 to 0.3% by weight of MnO to these materials, the sinterability is improved and the properties are further improved.

0010

[Function] By using the dielectric ceramic composition of the present invention, the dielectric constant at room temperature shows a high value of 2000 to 4700, 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). Ta.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a ternary composition diagram of the main components of the dielectric ceramic composition of the present invention, FIG. 2 is a manufacturing process diagram of the dielectric ceramic composition, and FIG. 3 is a temperature characteristic curve of capacitance.

Highly purified BaCO3 and TiO2 are prepared in a molar ratio of 1:1 as starting materials for barium titanate, and the prepared starting materials are dehydrated and dried (see FIG. 2).

[0013] Next, these raw materials are temporarily formed and
Stabilize at 1200°C for 2 hours to carry out a chemical reaction, and
Temporary firing is performed to form aTiO3. Obtained BaT
Finely pulverize iO3 using an atomizer, etc. (Figure 2)
reference).

BaTiO3 powder thus obtained or BaTiO3 prepared by solution method
Powder, Nb2O5, CoO, SrZrO3, Nd
2 O3 and MnO are weighed so that the composition after firing is as shown in Table 1 (see Figure 2).

[0015]

[Table 1]

[0016] After the weighed raw material powders are wet-mixed, they are dehydrated and dried (see Figure 2).

[0017] Add an appropriate amount of organic binder to this, and make about 3 tons.
Molded at a molding pressure of on/cm2, diameter 16.5mm
, A disc-shaped molded product with a thickness of approximately 0.6 mm is created. Next, this molded product is stabilized at 1260° C. to 1380° C. for 2 hours and subjected to main firing (see FIG. 2).

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

Each of the electrical properties of these capacitors, ie, relative dielectric constant (εs), dielectric loss (tan δ), insulation resistance, and rate of change in capacitance with temperature, was measured. In addition,
The relative permittivity and dielectric loss are at a frequency of 1KHz, 1V, and a room temperature of 20°C.Insulation resistance is a DC, 500V, and a room temperature of 2
The measured value was obtained after 1 minute at 0°C, and the temperature change rate of capacitance was -55°C and +12 compared to the value at 25°C.
The rate of change in value at 5°C and +150°C is calculated (see Figure 2 ■).

The results of each measurement are shown in Tables 1 and 2.

[0021]

[Table 2]

Here, the sample numbers in Tables 1 and 2 are the same; the same numbers indicate the same samples, Table 1 shows the composition of each sample, and Table 2 shows the electrical characteristics of the corresponding samples.

[0023] In addition, in Tables 1 and 2, sample Nos. 1, 3-3, 3-4, 3-8, 3-12, 6, and
8 and 10 are outside the scope of the present invention and are shown for comparison with examples of the present invention.

As is clear from Tables 1 and 2, the dielectric ceramic composition of the present invention has a dielectric constant of 2000 to 470 at room temperature.
0, the dielectric loss is a small value of 1.2% or less, and the temperature change rate of the capacitance is EIAJ.
Satisfies the ×7R characteristics and ×8R characteristics specified in .

FIG. 1 is a ternary composition diagram showing the composition of the main components of the dielectric ceramic composition of the present invention, and the numbers of each point in FIG. 1 are the same as the sample numbers in Tables 1 and 2. be.

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

FIG. 3 shows the capacitance temperature characteristic curves of three of the samples in Tables 1 and 2.

In FIG. 3, curve A corresponds to sample No. 1 in Tables 1 and 2, and each point (Δ) on curve A corresponds to the rate of change of capacitance at each temperature in Tables 1 and 2. . Similarly,
Curve B including the point (・) is sample No. 3 in Tables 1 and 2.
Curve C including -1 and point (x) corresponds to sample No. 3-3 in Tables 1 and 2.

As is clear from FIG. 3, the porcelain composition having a composition within the range of the present invention (curve B, ie, sample No. 3-1) has a temperature change rate of capacitance over a wide temperature range (-55°C to +150°C).
°C), it is small and stable at less than ±15%.

Next, the reason for limiting the composition range of the dielectric ceramic composition of the present invention will be explained. BaTiO3 is 94.00
If it is less than mol %, the dielectric constant will be as low as 2000 or less (see, for example, sample No. 6 in Tables 1 and 2).

[0031] When BaTiO3 exceeds 99.0 mol%, the dielectric loss increases beyond 1.2%, the temperature change rate of capacitance increases, and the sinterability deteriorates (
For example, see Tables 1 and 2 and sample No. 1 in FIG. 3).

[0032] Furthermore, if Nb2O5 is less than 0.50 mol%, the dielectric loss increases beyond 1.2%, the temperature change rate of capacitance also increases, and sinterability deteriorates. (For example, see Table 1, Table 2 and sample No. 1 in Figure 3)
.

[0033] When Nb2O5 exceeds 3.0 mol%, the dielectric constant becomes low (see, for example, sample No. 6 in Tables 1 and 2), and the temperature change rate of capacitance becomes large (for example, as shown in Table 1). , see sample No. 8 in Table 2).

Furthermore, if the CoO content is less than 0.5 mol %, the dielectric loss will increase to more than 1.2 %, the temperature change rate of capacitance will increase, and the sinterability will deteriorate (
For example, see Tables 1 and 2 and sample No. 1 in FIG. 3).

[0035] When CoO exceeds 3.0 mol%, the dielectric constant becomes as low as 2000 or less (see, for example, sample No. 6 in Tables 1 and 2), and the temperature change rate of capacitance becomes large. (For example, see sample No. 10 in Tables 1 and 2).

[0036] Also, the additive BaZrO3 is 0.2
If it is less than % by weight, the rate of change in capacitance with temperature becomes large;
×8R characteristics are no longer satisfied (for example, see sample No. 3-4 in Tables 1 and 2).

[0037] When SrZrO3 exceeds 7.0% by weight, the temperature change rate of capacitance becomes large and the x8R characteristic is no longer satisfied (for example, sample No. 3-8 in Tables 1 and 2
reference).

[0038] Furthermore, with respect to the above composition, Nd2O3
Although there is no problem in use without the addition (for example, see sample No. 3 in Tables 1 and 2), the sinterability improves with addition of up to 0.5% by weight (for example, sample No. 3-1 in Tables 1 and 2). ,3-
(see 2).

However, if Nd2O3 is 0.5% by weight
If it exceeds , the temperature change rate of capacitance increases and
The R characteristic is no longer satisfied (for example, see Table 1, Table 2, and sample No. 3-3 in FIG. 3).

[0040] Even if MnO is not added, there is no problem in use (see, for example, sample No. 3-9 in Tables 1 and 2).
Addition of up to 0.3% by weight prevents reduction, improves dielectric loss, and improves sinterability (for example, Table 1, Table 2).
(See 3-10, 3-11).

When the amount of MnO added exceeds 0.3% by weight, the temperature change rate of capacitance becomes large, sinterability deteriorates, and dense porcelain cannot be obtained (for example, Table 1, Table 2
(See sample No. 3-12).

[0042] Furthermore, Si as an alkali metal oxide contained in the raw material or a trace amount of impurity mixed in during the manufacturing process.
O2 and Al2 O3 do not significantly deteriorate the characteristics.

[0043]

Effects of the Invention The dielectric ceramic composition of the present invention has a high dielectric constant of approximately 2000 to 4700, a dielectric loss of 1.2% or less, and a temperature change rate of capacitance of E
Not only does it satisfy the ×7R characteristics specified by IAJ,
It is possible to obtain an excellent dielectric ceramic composition with a high dielectric constant, which has excellent characteristics satisfying the x8R characteristic and can be used, for example, in the engine room of an automobile.

Furthermore, since this dielectric ceramic composition 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 alone or palladium may be used as the internal electrode. It becomes possible to use silver-palladium alloys.

[0045] Therefore, there is no need to use expensive platinum or platinum-palladium, and a significant reduction in the cost of the product can be achieved, resulting in immeasurable industrial benefits.

[Brief explanation of drawings]

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 an embodiment of the present invention.

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

Claims (3)

[Claims] Claim 1: BaTiO3 as main component: 94.0 to 99.0 mol% Nb2O
5: 0.5-3.0 mol%CoO
: A high dielectric constant dielectric ceramic composition containing 0.2 to 7.0% by weight of SrZrO3 as an additive with respect to 0.5 to 3.0 mol%. 2. Adding 0.5 of Nd2O3 to the composition
2. The high dielectric constant dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition contains not more than % by weight. 3. 0.3% by weight of MnO in the composition
The high dielectric constant dielectric ceramic composition according to claim 1 or 2, characterized in that it contains the following: