JP2660010B2 - High dielectric constant porcelain composition and ceramic capacitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a high dielectric constant porcelain composition, and particularly to a high dielectric constant porcelain composition mainly composed of Pb having excellent life characteristics. It relates to a ceramic capacitor.

(Prior Art) Conventionally, various dielectric materials have been studied.

A conventionally known high dielectric constant porcelain composition is based on barium titanate, in which lead stannate, lead zirconate, lead titanate or the like is dissolved. Certainly, a material having a high dielectric constant can be obtained, but there has been a problem that the dielectric constant has a large temperature coefficient of permittivity (TCC) and the bias electric field dependency also increases. Further, the firing temperature of the barium titanate-based material is 13
The temperature is as high as about 00 to 1400 ° C., and an expensive material such as platinum and palladium that can withstand a high temperature must be used as an electrode material, which causes an increase in cost.

In order to solve the problems of the barium titanate, various compositions have been studied. For example, those mainly composed of lead iron niobate (JP-A-57-57204), magnesium
There are those mainly composed of lead niobate (JP-A-55-51758) and those mainly composed of magnesium / lead tungstate (JP-A-52-21699). Those mainly composed of lead iron niobate have a problem that the CR value greatly changes depending on the sintering temperature, and particularly, the CR value decreases greatly at high temperatures. Those mainly composed of magnesium and lead niobate have relatively high firing temperatures, and those mainly composed of magnesium and lead tungstate have a low dielectric constant when the CR value is large and a low CR value when the dielectric constant is large. There was a problem of being small. Furthermore, the TCC of these materials is better than barium titanate, but not enough.

Further, a study has been made on a solid solution of lead magnesium niobate and lead titanate in which part of lead is replaced by barium, strontium, or calcium as necessary (Japanese Patent Application Laid-Open No. 55-121959). However, the T.
The best CC at −25 to 85 ° C. is −59.8%, which is not sufficient. Further, the most important CR value as a capacitor material is not described, and its usefulness as a capacitor material is not clear.

JP-A-57-25607 also studies a material of a solid solution of lead magnesium niobate and lead zinc niobate. However, the CR value and TCC are not described, and its usefulness as a capacitor material is not clear.

In consideration of these problems, a high dielectric constant porcelain composition having a large dielectric constant and a small temperature coefficient has been invented (JP-A-61-155245).

Capacitor materials are required to have excellent electrical characteristics such as permittivity, TCC, dielectric loss, dielectric bias electric field dependence, and capacitance-resistance product, but the reliability, that is, the life characteristics of the capacitor is even more important. . However, a high dielectric constant porcelain composition having excellent electrical characteristics and having less deterioration in characteristics even under severe conditions (high temperature, high humidity, and application of a constant voltage) has not yet been obtained.

(Problems to be Solved by the Invention) The present invention has been made in consideration of the above points, and has as its object to provide a high dielectric constant ceramic composition and a ceramic capacitor having excellent life characteristics and excellent reliability. .

[Configuration of the invention]

(Means and Actions for Solving the Problems) The present invention relates to a perovskite-based high dielectric constant porcelain composition containing Pb as a constituent element, wherein yttrium (Y) is converted to Y ₂ O ₃ by a weight ratio of 100 to 50,000 ppm. It is a high dielectric constant porcelain composition characterized by being added and contained, and by using this as a dielectric layer, an excellent ceramic capacitor can be provided.

Yttrium is converted to Y ₂ O ₃ and the weight ratio is 100 ≦ Y ₂ O ₃ ≦ 5
When 0000 ppm is added, the electrical characteristics (especially insulation resistance) of the dielectric to which a voltage is constantly applied hardly deteriorate even in a high temperature and high humidity state. Yttrium exhibits an effect when added at 1000 ppm or more, and exhibits an excellent effect particularly when added at 500 ppm or more. If it exceeds 50,000 ppm, the life characteristics are rather deteriorated.

Although the cause is not clear, Y ₂ O ₃ is hardly dissolved in the perovskite-based high dielectric constant porcelain composition containing Pb as a constituent element, and Y ₂ O ₃ is localized at the triple point of each particle. it is conceivable that. Accordingly, there is no particular limitation as long as it is a perovskite-based high dielectric constant porcelain composition containing Pb. The Pb abundance is preferably 30 to 70 wt% in terms of PbO, and within this range, the dielectric constant is high.

Examples of the perovskite-based high dielectric constant porcelain composition containing Pb include Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Zn _1/3 Nb _2/3 ) O ₃ , PbTi
O ₃ , PbZrO ₃ , Pb (Fe _1/2 Nb _1/2 ) O ₃ , Pb (Fe _2/3 W _1/3 ) O ₃ , Pb
(Mg _1/2 W _1/2 ) O ₃ Pb (Ni _1/3 Nb _1/3 ) O ₃ or the like as a basic component. Naturally, these composite systems are also mentioned,
Needless to say, various additives such as MnO ₂ , Co ₂ O ₃ , La ₂ O ₃ , Sb ₂ O ₃ , NiO, MgO, and ZrO ₂ may be included.

In particular, yttrium is converted to Y ₂ O ₃ in a composition containing at least _{one of} Pb (Mg _1/3 Nb _1/3 ) O ₃ and Pb (Zn _1/3 Nb _1/3 ) O _{3 in} an amount of 50 mol% or more. By adding 100 ≦ Y ₂ O ₃ ≦ 50000 ppm, a material having a high dielectric constant and excellent life characteristics can be obtained. In this case, 1 to 35 mol% of the Pb atom is Ba, Sr,
By substituting at least one of Ca, high dielectric constant and insulation resistance can be further increased.

As a particularly preferred embodiment, when represented by the general formula xPb (Zn _1/3 Nb _2/3 ) O ₃ -yPb (Mg _1/3 Nb _2/3 ) O ₃ -zPbTiO ₃ , each component has a peak. A (x = 0.50, y = 0.00, z = 0.50) b (x = 1.00, y = 0.00, z = 0.00) c (x = 0.20, y = 0.80, z = 0.00) in the ternary diagram (Fig. 1) ) D (x = 0.05, y = 0.90, z = 0.05) A part of Pb of the basic composition in the line connecting the points (except on the line connecting ab) is 1 to 35 mol%. Ba and Sr
The yttrium (Y) element is converted to Y ₂ O ₃ in the basic composition substituted with at least one of
A high dielectric constant porcelain composition characterized by adding 0 ≦ Y ₂ O ₃ ≦ 50000 ppm is provided.

In the present invention, as described above, the basic composition was within the line connecting the points of a, b, c, and d.If the range deviated from this range, the firing temperature would be as high as 1100 ° C. or higher outside the line segment ad. In addition, the insulation resistance is lowered and a high CR value cannot be obtained.

Further, since the Curie temperature is originally around room temperature outside the line segment cd, the dielectric constant largely shifts to a lower temperature side by the replacement with the Me component, and the dielectric constant at room temperature is greatly reduced. When d ₁ (x = 0.10, y = 0.80, z = 0.10), the inside of the line segment cd ₁ is more preferable.

Magnesium / lead niobate exhibits its effect when added or contained in a small amount, but is preferably contained in an amount of 1 mol% or more in practical use.

Also, considering the CR value, 15 mol of zinc and lead niobate
%, More preferably 20 mol% or more. When the content is 20 mol% or more, the dielectric loss is particularly small.

Also, c ₁ (x = 0.40, y = 0.60, z = 0.00), d ₂ (x = 0.15,
y = 0.70, z = 0.15), d ₃ (x = 0.20, y = 0.60, z = 0.20), c
₂ (x = 0.45, y = 0.55, z = 0.00), the line segment c ₁ d ₁
Outside, it is relatively difficult to obtain dense porcelain.

Thus, considering the CR value, TCC, sinterability, etc., the line segment
The inside of c ₁ d ₂ , particularly the line segment c ₂ d _{2, and} more preferably the inside of line segment c ₂ d ₃ is preferred. However, when the dielectric constant and the like are taken into consideration, even a composition system divided by such a line segment has sufficient characteristics. Furthermore, y0.01, z0.01 and Pb (Mg _1/3 Nb _2/3 )
Elements in which O ₃ and PbTiO ₃ are present are more preferable.

On the other hand, Ba and Sr are elements necessary for forming the perovskite structure of the above general formula.
Pyrochlore structure is mixed and does not show high dielectric constant and high insulation resistance. If it is more than 35 mol%, the dielectric constant may be as small as about 1000 or less. Therefore, the substitution amount in the Me component is expressed as 0.01 <α <0.35 when expressed as (Pb ₁ αMeα).

Other xPb (Zn _1/3 Nb _2/3 ) O ₃ − yPb (Mg _1/3 Nb _1/3 ) O ₃ −zPb (Ni _1/3 Nb _2/3 ) O ₃ A (x = 0.50, y = 0.00, z = 0.50) b (x = 1.00, y = 0.00, z = 0.00) c (x = 0.10, y = 0.90, z = 0.00) (1−x) in which a part of Pb of the composition in the line connecting the points shown by (except on the line connecting abc) is substituted with at least one of Ba and Sr of 1 to 30 mol%, (Pb _1-ab Ba _a Sr _b ) ｛(Zn _1/3 Nb _2/3 ) _1-cd (Mg _1/3 Nb _2/3 ) _c Ti _d ｝ O ₃ · xBaTiO ₃ , 0 ≦ a ≦ 0.35 0 ≦ b ≦ 0.35 0.01 ≦ a + b ≦ 0.35 0 <c ≦ 0.9 0 <d ≦ 0.5 0.3 ≦ x ≦ 0.5, x · Pb (Zn _1/3 Nb _2/3 ) O ₃ -y · When represented by Pb (Mg _1/3 Nb _2/3 ) O ₃ .z-PbTiO ₃ , a (x = 0.60, y = 0.40, z = 0.00) b () of a ternary diagram having each component as a vertex x = 0.60, y = 0.05, z = 0.35) c (x = 0.45, y = 0.0 5, z = 0.50) d (x = 0.01, y = 0.49, z = 0.50) e (x = 0.01, y = 0.85, z = 0.14) f (x = 0.15, y = 0.85, z = 0.00) Part of Pb in the line connecting each point
and those substituted with 1% of Ca.

In the case of manufacturing a laminated type element, a binder, a solution, etc. are added to the raw material powder or the powder after mixing and pulverization to form a slurry, a green sheet is formed, and an internal electrode is printed on the green sheet. Is manufactured by laminating, pressing and firing. At this time, since the dielectric material of the present invention can be sintered at a low temperature, an inexpensive material mainly composed of, for example, Ag (Ag: 80 to 50%, Pb: 20 to 50%) can be used as the internal electrode material.

In addition, since firing at such a low temperature is possible,
It is also effective as a material for a thick film dielectric paste printed and fired on a circuit board or the like.

Such a porcelain composition of the present invention has a high dielectric constant and good temperature characteristics. In addition, the CR value is large, and has a sufficient value even at a high temperature, and a ceramic capacitor excellent in reliability at a high temperature can be obtained.

Furthermore, the dielectric constant bias electric field dependency is excellent, and 2kV /
A material of about 10% or less can be obtained even in mm. Therefore, it is effective as a material for BX characteristics and high pressure of MIL.
Further, it has a small dielectric loss and is effective for AC and high frequency applications. Further, as described above, since the temperature characteristics of the dielectric constant are excellent, even when applied to an electrostrictive element, an element having a small temperature change in displacement can be obtained.

(Example) An example of the present invention will be described below.

Example-1 After using a starting material such as an oxide such as Pb, Ba, Sr, Zn, Nb, Y, Fe, W, Ti, or Mg as a starting material, a desired composition was prepared, and then a ball mill or the like was prepared. And calcined at 700-850 ° C. Next, the calcined body was pulverized by a ball mill or the like, dried, and then granulated by adding a binder, followed by pressing to form a disc-shaped element having a diameter of 17 mm and a thickness of about 2 mm. It is preferable to use a ball having high hardness and high toughness, such as a partially stabilized zirconia ball, as a ball for mixing and pulverization in order to prevent contamination of impurities.

The element was sintered in air at 980 to 1080 ° C. for 2 hours, and silver electrodes were baked on both sides. Then, after applying a voltage of 100 V for 2 minutes, the insulation resistance was measured at 25 ° C. using an insulation resistance meter. In the life test, the device was held in a constant temperature / humidity chamber at 55 ° C. and 95% RH, and 100 V was applied. After a lapse of 200 hours, the device was taken out, the surface moisture was removed, the device was left at room temperature for 24 hours, and the insulation resistance was measured again at 25 ° C.

The capacity was measured by a digital LCR meter under the conditions of 1 KHz, 1 Vrms and 25 ° C., and the dielectric constant was determined from this value. The capacitance resistance product CR was determined from (dielectric constant) × (insulation resistance) × (dielectric constant in vacuum) at 25 ° C.

Table 1 shows the initial value of CR and the CR value after a 200-hour life test. As is evident from Table 1, the porcelain composition of the present invention shows little deterioration of the capacitance-resistance product even at high temperature, high humidity and a voltage applied state, and is excellent in reliability.

Example 2 A sintered body having the composition shown in Table 2 was prepared in the same manner as in Example 1, and each characteristic was measured. Dielectric loss, capacity is 1KHz, 1Vrm
s, Measured by a digital LCR meter under the conditions of 25 ° C., from which the dielectric constant was calculated. The insulation resistance was calculated from a value measured using an insulation resistance meter after a voltage of 100 V was applied for 2 minutes. The capacitance-resistance product was determined from (dielectric constant) × (insulation resistance) × (dielectric constant in vacuum) at 25 ° C.

In the life test, the element was held in a constant temperature / humidity chamber at 55 ° C. and 95% RH, and 100 V was applied.

After a lapse of 200 hours, the device was taken out, moisture on the surface was removed, and the device was left at room temperature for 24 hours. Then, the capacitance, dielectric loss, and insulation resistance were measured.

Table 2 shows the results. As is evident from Table 2, the porcelain composition of the present invention has little deterioration in insulation resistance even under high temperature, high humidity and a voltage applied state, and has excellent reliability.

[Effects of the Invention] As described above, according to the present invention, a high dielectric constant porcelain composition having excellent reliability, a high dielectric constant, and excellent temperature characteristics and bias characteristics can be obtained. In particular, since porcelain excellent in such various characteristics can be obtained by firing at low temperature, it is suitable for application to multilayer ceramic elements such as multilayer ceramic capacitors and multilayer ceramic displacement generating elements.

[Brief description of the drawings]

 FIG. 1 is a composition diagram showing the present invention.

Claims (4)

(57) [Claims] (1) Yttrium (Y) is added to Y ₂ O _{5 in} a perovskite-based high dielectric constant porcelain composition containing Pb as a constituent element.
A high dielectric constant porcelain composition characterized by containing 100 to 50,000 ppm by weight in terms of weight. 2. The perovskite-based high dielectric constant porcelain composition comprises at least 50 mol% of at least _{one of} Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb (Zn _1/3 Nb _2/3 ) O _3. Containing 1 to 35 mol% of Pb as B
The high dielectric constant porcelain composition according to claim 1, wherein the composition is substituted with at least one of a, Sr, and Ca. 3. The perovskite-based high dielectric constant porcelain composition is represented by a general formula xPb (Zn _1/3 Nb _2/3 ) O ₃ -yPb (Mg _1/3 Nb _2/3 ) O ₃ -zPbTiO ₃ . Then, a (x = 0.50, y = 0.00, z = 0.50) b (x = 1.00, y = 0.00, z = 0.00) c (x = 0.20, y = 0.80, z = 0.00) d (x = 0.05, y = 0.90, z = 0.05) Part of Pb of the basic composition in the line connecting the points (excluding the line connecting ab) 1 to 35 mol% Ba and Sr
2. The high dielectric constant porcelain composition according to claim 1, wherein the composition is replaced by at least one of the following. 4. A ceramic capacitor having a dielectric layer comprising the high dielectric constant porcelain composition according to claim 1.