JP2803320B2 - Dielectric porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a dielectric porcelain composition, in particular, which can be sintered at a low temperature of 1000 ° C. or lower, has a high dielectric constant, a small temperature change rate of the dielectric constant, and a room temperature. The present invention also relates to a dielectric ceramic composition for a ceramic capacitor having a high insulation resistance at a high temperature, a high mechanical strength, a low dependence of electrical characteristics on a sintering temperature, and a small sintered particle size.

[Prior Art and Problems to be Solved by the Invention] Conventionally, as a dielectric ceramic composition for ceramic capacitors, porcelain mainly containing barium titanate (BaTiO ₃ ) has been widely put into practical use. Those containing barium as a main component generally have a high sintering temperature of 1300 to 1400 ° C. When this is used for a multilayer ceramic capacitor, a material that can withstand this sintering temperature as an internal electrode,
For example, expensive precious metals such as platinum and palladium have to be used, and there is a disadvantage that the production cost is increased. To make multilayer ceramic capacitors cheap,
There is a need for a porcelain that can be sintered at as low a temperature as possible, in particular at 1000 ° C. or lower, so that an inexpensive metal mainly composed of silver, nickel or the like can be used for the internal electrodes.

Further, the electrical characteristics of the dielectric ceramic composition are basically required to have a high dielectric constant, a small dielectric loss, and a high insulation resistance.

In the case of a multilayer chip capacitor, when the chip capacitor is mounted on a board, mechanical distortion is applied to the chip capacitor due to the difference in thermal expansion coefficient between the board and the porcelain that constitutes the chip capacitor, and the chip capacitor cracks. May occur or be damaged.
In this case, the lower the mechanical strength of the porcelain forming the capacitor, the more likely it is to crack, easily break and reduce reliability, so it is extremely important in practical use to increase the mechanical strength of the porcelain as much as possible. It is.

In the case of a composite laminated ceramic component having a structure in which a dielectric layer and an insulator layer are laminated, the sintering temperature of the insulator is 850 to 1000 ° C, and silver, nickel, etc. In order to use inexpensive metals as conductors, to generate stress due to compounding during sintering, and to match with the shrinkage characteristics of insulators,
A dielectric porcelain that can be sintered at 1000 ° C or less and has high mechanical strength is required.

In recent years, a multilayer ceramic capacitor has been required to have a small capacity change rate with respect to a use temperature and to have a small and large capacity in order to use electronic components at a high temperature and to stabilize circuit characteristics. Regarding the rate of change in capacitance, for example, there have been known some that satisfy the Y5T characteristic of the EIA standard in a temperature range of −30 to + 85 ° C., but all have a low dielectric constant of about 6000 to 8000. Therefore, in order to reduce the size and capacitance of the multilayer capacitor and improve the temperature characteristics, it is necessary to find a dielectric ceramic composition having a high dielectric constant and a small rate of change in capacitance with respect to the measurement temperature. It is necessary to increase the capacitance by increasing the number of layers by reducing the thickness as much as possible. However, in conventional barium titanate-based porcelain, increasing the dielectric constant increases the grain size of the sintered body, and decreasing the dielectric breakdown voltage decreases the reliability of manufacturing a multilayer capacitor with a thin dielectric layer. Also had the disadvantage that it became worse.

The Pb (Mg _1/2 W _1/2 ) O ₃ -Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ system is disclosed in JP-A-55-116662 and the like. It is known that a dielectric porcelain composition containing a large amount of lead tungstate has excellent characteristics in which the temperature change of capacitance is small. However, on the other hand, it is also known that there is a problem that the electrical characteristics are highly dependent on the sintering temperature and it is difficult to obtain a sintered body having stable electrical characteristics. In addition, since the particle size of the sintered ceramic is large, it is difficult to manufacture a multilayer chip capacitor having a thinner film thickness. In order to improve this, various methods for synthesizing the raw material powder have been studied, but all have the drawback of increasing the production cost.

The present invention solves the problems described above,
Can be sintered in a low temperature range of 1000 ° C or less, has a high dielectric constant, a small rate of change in dielectric constant with temperature, has a high insulation resistance at room temperature and high temperature, has a high mechanical strength, and has low sintering temperature dependence of electrical characteristics. An object of the present invention is to provide a dielectric ceramic composition having a small sintered body particle size.

[Means for Solving the Problems] The present invention relates to a magnesium / lead tungstate [Pb (Mg
_1/2 W _1/2 ) O ₃ ], lead magnesium niobate [Pb (Mg
_1/3 Nb _2/3 ) O ₃ ], lead titanate [PbTiO ₃ ] and lead zirconate [PbZrO ₃ ] quaternary solid solution porcelain composition [Pb (Mg _1/2 W _1/2 ) O _{3] X - [Pb (Mg} 1/3 Nb 2/3) O 3] Y - [PbTiO 3] Z - [PbZrO 3] U ( However, X, Y, Z and U represents a molar fraction, X + Y
+ Z + U = 1) When X, Y, Z, U are respectively represented by 0.05 ≦ X ≦ 0.3 0.3 ≦ Y ≦ 0.85 0.05 ≦ Z ≦ 0.3 0.05 ≦ U ≦ 0.3 A dielectric ceramic composition characterized in that a composite oxide containing manganese as an additive is added and contained in an amount of 0 to 4 mol% with respect to the main component composition.

The dielectric porcelain composition of the present invention uses, as a starting material, an oxide, a hydroxide, and a raw material compound that becomes an oxide at a temperature of 600 ° C. or more, such as a carbonate, and wet-mixes the weighed raw material compounds using a ball mill. 700-900 ° C, preferably 75
Perform calcination at 0 to 850 ° C to obtain a raw material powder for the porcelain composition,
After molding using the obtained raw material powder, 850-1
It can be manufactured by sintering at 100 ° C, preferably 950 to 1100 ° C.

In a composition in which the main component magnesium / lead tungstate is more than the range of the present invention, the dielectric constant is small, the electrical characteristics are highly dependent on the sintering temperature, and the particle size of the sintered porcelain composition is large, and the is not. On the other hand, a composition having a content of less than 0.05 has a disadvantage that the temperature change of the dielectric constant is large.

In the porcelain composition of the present invention containing four components including lead zirconate as a main component, the temperature change of the dielectric constant is suppressed,
Moreover, sintering can be performed while suppressing the grain growth by reducing the sintering temperature dependence of the electrical characteristics. However, in a composition containing more lead zirconate than the range of the present invention, the dielectric constant is small and the dielectric loss at room temperature is large, which is not practical. On the other hand, a composition having a content of less than 0.05 has a disadvantage that the temperature change of the dielectric constant is large, grain growth cannot be suppressed, and the transverse rupture strength is low.

The content of magnesium / lead niobate / lead titanate is 0.
When the composition is less than 05, the dielectric constant becomes small and is not practical. On the other hand, a composition having a large content of these components has a disadvantage that the temperature change of the dielectric constant is large.

Further, when a composite oxide containing manganese is added as an additive, although the capacitance decreases, the temperature characteristic of the capacitance change is greatly improved as shown in the examples. A similar effect can be obtained by increasing the proportion of magnesium / lead tungstate or lead zirconate contained in the main component. However, since the contents of both are limited as described above, a composite oxide containing manganese is used. The desired electrical properties can be obtained by adding an appropriate amount of the substance.

Pb (Mn _1/3 Nb _2/3 ) as a composite oxide containing manganese
O ₃ , Pb (Mn _1/2 Nb _1/2 ) O ₃ , Pb (Mn _1/3 Ta _2/3 ) O ₃ , Pb (Mn _1/2
W _1/2 ) O ₃ , Pb (Mn _1/3 Sb _2/3 ) O _{3 and the} like, and in each case, the same effect can be obtained. The addition amount of these manganese-containing composite oxides is slightly different depending on the kind, but is preferably 4 mol% or less with respect to the main component. Absent.

[Examples] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 Lead oxide (PbO), magnesium oxide (MgO), tungsten oxide (WO ₃ ), niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO) having a purity of 99.9% or more as starting materials ₂ ) and manganese carbonate (MnCO ₃ ) were used and weighed so that the mixing ratio shown in Table 1 was obtained. However, in Table 1, the main components magnesium / lead tungstate are represented by PMW, magnesium / niobate by PMN, lead titanate by PT, and lead zirconate by PZ.
Z and U (molar fractions) are expressed as percentages and X ', Y', Z ', U'
(X '+ Y' + Z '+ U' = 100).

Next, the weighed raw materials are wet-mixed in acetone using a ball mill, and then calcined in a magnesia crucible at 700 to 800 ° C. And Using the obtained raw material powder, a disk with a diameter of 10 mm and a thickness of 3 mm was created,
Baking was performed at 0 ° C. for 1 hour. Silver electrodes were baked on the upper and lower surfaces of the sintered disc, and a voltage of 50 V DC was applied for 1 minute at room temperature with a super insulation resistance meter to measure insulation resistance and calculate specific resistance.
Next, the sample was placed in a thermostat, and the capacitance and the dielectric loss at 25 ° C. were measured at a frequency of 1 kHz and a voltage of 1 Vrms using a digital LCR meter, and the dielectric constant was calculated. The average value of the four samples was taken as a representative value. Further, the capacitance and the dielectric loss were measured in the temperature range of -55 to + 125 ° C, and the capacitance change rate based on the capacitance at 20 ° C was calculated.

Table 1 shows the compounding ratio of each main component, the type and amount of additives, the dielectric constant and dielectric loss at 25 ° C, the specific resistance at room temperature, and the capacitance at -30 ° C and 85 ° C based on 20 ° C. The values of the rate of change are shown.

Further, as a result of observing the fractured surface of the sintered body with a scanning electron microscope, it was found that the average particle size was 2 μm, which was a small and uniform microstructure.

Examples 2 to 11 Raw material powders having the composition shown in Table 1 were prepared in the same manner as in Example 1, and a sintered body was prepared at a sintering temperature of 1000 ° C., and the electrical characteristics were measured. Table 1 summarizes the measured results. Further, the fracture surface of the sintered body of Example 11 was observed with a scanning electron microscope, and the result as shown in the photograph of FIG. 1 was obtained. First
As can be seen from the figure, the average particle size was as small as 2 μm and the microstructure was uniform.

Examples 12 to 14 Raw material powders having the composition shown in Table 1 were prepared in the same manner as in Example 1, and sintered bodies were prepared by changing the sintering temperature to 950, 1000 and 1050 ° C., and the electrical characteristics were measured. Even if the sintering temperature changed by 100 ° C., almost no change was observed in the electrical characteristics. Table 1 summarizes the measured results.

Examples 15 to 28 In the same manner as in Example 1, raw material powders having the composition shown in Table 1 were prepared, sintered bodies were prepared at sintering temperatures of 1000 ° C. and 1050 ° C., and the electrical characteristics were measured. Table 1 summarizes the measured results.

Comparative Examples 1 and 2 Powders having the main component mixing ratios shown in Table 2 were prepared in the same manner as in Example 1. A sintered body of the porcelain composition was prepared at a sintering temperature of 1050 ° C., and the electrical characteristics were measured. The results shown were obtained.

Comparative Examples 3 to 5 In the same manner as in Example 1, raw material powders having the mixing ratios of main components shown in Table 2 were prepared, sintered bodies were prepared at sintering temperatures of 1000, 1050, and 1100 ° C., and electrical characteristics were measured. Table 2 summarizes the measured results. As shown in Table 2, when the sintering temperature changed by 100 ° C., the electrical characteristics changed significantly.

Comparative Examples 6 to 12 In the same manner as in Example 1, raw material powders having the main component mixing ratios shown in Table 2 were prepared, and sintered bodies were prepared at sintering temperatures of 1050 and 1100 ° C., and electrical characteristics were measured. Table 2 summarizes the measured results. Further, the fracture surface of the sintered body of Comparative Example 4 was observed with a scanning electron microscope, and a photograph as shown in FIG. 2 was obtained.
As can be seen from the figure, the average particle size was as large as 5 to 7 μm, and the particle size distribution was not uniform.

(Measurement of bending strength) From the sintered bodies of Examples 1, 2, 4, 5, 25, and 26 and Comparative Examples 2, 4, and 8, strip-shaped samples having a width of 2 mm, a thickness of 0.5 mm, and a length of 12 mm were obtained. The bending strength was measured with a 10-piece bending strength tester. It was measured
Table 3 summarizes the average values of the ten tubes.

[Effects of the Invention] As is clear from the results shown in Table 1, Pb (Mg
_{1/2 W 1/2) O 3 -Pb (} Mg 1/3 Nb 2/3) O 3 -PbTiO 3 composite oxide containing manganese as an additive to the four component composition of -PbZrO ₃ 0~4mol% Those added within the range of the present invention have a high dielectric constant, a small dielectric loss of 3% or less, a high specific resistance of 1 × 10 ¹² Ωcm or more at room temperature, and a temperature of −30 to +85.
Among those showing a capacitance change rate of -33% to + 22% based on the capacitance at 20 ° C in a temperature range of 20 ° C, those having a dielectric constant of 10,000 or more, 56
% To + 22%, the dielectric constant is 16
A ceramic composition having a value close to 000 was obtained, and the ceramic composition was suitable for a small and large-capacity multilayer ceramic capacitor having a small capacity change rate.

As is clear from an electron micrograph showing the fractured surface of the sintered body, the porcelain in the composition region of the present invention has an extremely fine and uniform microstructure, so that a multilayer ceramic capacitor having a thinner film thickness can be obtained. It can be said that it is suitable for manufacturing. on the other hand,
As shown in the comparative example, in the porcelain outside the composition range of the present invention, since the particle size is large and the particle size distribution is not uniform, when a multilayer ceramic capacitor having a small film thickness is manufactured, the dielectric breakdown voltage is lowered or the reliability is reduced. Because of its lowering, it was unsuitable as a practical material.

The dielectric porcelain composition of the present invention has a low sintering temperature, so that the price can be reduced by making the internal electrodes of the multilayer capacitor an inexpensive base metal, and the obtained porcelain has excellent electrical characteristics and is excellent in dielectric properties. Since it is possible to cope with the thinning of the layers, a multilayer ceramic capacitor having a small size and a large capacity can be manufactured. In addition, since the PbZrO ₃ component is contained, a porcelain having excellent characteristics can be obtained without employing a method of synthesizing a raw material powder that increases the production cost, and the particle size of the sintered body can be reduced. As a result, as shown in Table 3, the mechanical strength is improved, the dielectric breakdown voltage is increased, and a highly reliable ceramic capacitor can be manufactured. Further, as shown in Examples and Comparative Examples, the use of the composition within the composition range of the present invention provides a porcelain with stable electrical characteristics even when the sintering temperature changes, and is practically usable. It can be said that the characteristics are extremely excellent. Therefore, it can be said that the industrial significance of the present invention is extremely large.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electron micrograph of a grain structure of a sintered body of Example 11, and FIG. 2 is an electron micrograph of a grain structure of a sintered body of Comparative Example 4. . However, the white bar in the figure is 10μ
m.

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 35/00 C04B 35/49 H01B 3/12 313

Claims (1)

(57) [Claims] Claims: 1. Magnesium lead tungstate [Pb (Mg
_1/2 W _1/2 ) O ₃ )], lead magnesium niobate [Pb (Mg
_1/3 Nb _2/3 ) O ₃ ], lead titanate [PbTiO ₃ ] and lead zirconate [PbZrO ₃ ] quaternary solid solution porcelain composition [Pb (Mg _1/2 W _1/2 ) O _{3] X - [Pb (Mg} 1/3 Nb 2/3) O 3] Y - [PbTiO 3) Z - [PbZrO 3] U ( However, X, Y, Z and U represents a molar fraction, X + Y
+ Z + U = 1) When X, Y, Z, U are respectively represented by 0.05 ≦ X ≦ 0.3 0.3 ≦ Y ≦ 0.85 0.05 ≦ Z ≦ 0.3 0.05 ≦ U ≦ 0.3 A dielectric porcelain composition characterized in that a composite oxide containing manganese as an additive is added and contained in an amount of 0 to 4 mol% with respect to the main component composition.