JP3468245B2 - Dielectric porcelain composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition, and more particularly to a dielectric ceramic composition containing lead as a main component and used for example as a dielectric material of a laminated ceramic capacitor. About things. 2. Description of the Related Art Conventionally, BaTiO ₃ is mainly used as a dielectric material of a high dielectric constant ceramic capacitor, and CaTiO ₃ , BaSnO ₃ , CaZrO ₃ , and the like are used as shifters.
Porcelain compositions to which SrTiO ₃ or the like has been added have been used. Porcelain made of these porcelain compositions has a high dielectric constant at room temperature of 2000 to 15000. However, these porcelain compositions have firing temperatures of 1300 ° C.
欠 点 1400 ° C., a high defect. Therefore, those porcelain compositions have high firing costs. Further, when the ceramic compositions are used for a laminated ceramic capacitor, a plurality of ceramic green sheets made of the ceramic compositions formed in advance with an electrode material are fired after being stacked, so that the electrode material is For example, noble metals having a high melting point, such as platinum and palladium, which do not melt, oxidize, or react with a dielectric at a high temperature of 1300 ° C. or more must be used. In order to solve the above-mentioned drawbacks, studies have been made on lead-based composite perovskite dielectric porcelain compositions mainly composed of lead which can be fired at a low temperature. In the lead-based composite perovskite dielectric porcelain composition, the firing temperature is 1050.
A porcelain composition having a relative dielectric constant of 10,000 or more at a temperature of not more than ℃ is already known. It is also known that when an excessive amount of lead is added to a lead-based composite perovskite dielectric porcelain composition, a high dielectric constant is obtained and the DC bias characteristics are improved. However, these lead-based porcelain compositions, when used in multilayer ceramic capacitors, have low mechanical strength and are susceptible to cracking, chipping and cracking. It has the disadvantage that it is easy to do. In particular, in a porcelain composition to which lead is added excessively, the mechanical strength is further reduced. Further, when cracks or voids occur in the laminated ceramic capacitor, moisture in the air permeates into the inside, causing a great decrease in the reliability of the capacitor. In particular, in a multilayer ceramic capacitor using a ceramic composition containing lead as a main component, the shape becomes large in order to obtain a large capacity, so that the influence of mechanical stress and thermal stress increases. Therefore, it is desired to improve the mechanical strength of the laminated ceramic capacitor. Therefore, a main object of the present invention is to provide a dielectric porcelain composition which can be fired at a low temperature, can obtain a porcelain having a large dielectric constant and excellent mechanical strength. . The present invention provides aPb (M
g _1/3 Nb _2/3 ) O ₃ -bPbTiO ₃ -cPb (Zn _1/3
Nb _2/3 ) O ₃ (where a, b and c are mol% and 5
9.5 ≦ a ≦ 98.5, 0.5 ≦ b ≦ 10.0, 1.0
≤ c ≤ 40.0. ) Or dPb (Mg _1/3 N
b _2/3 ) O ₃ -ePbTiO ₃ -fPb (Ni _1/3 N
b _2/3 ) O ₃ -gPb (Zn _1/2 W _1/2 ) O ₃ (provided that
d, e, f, and g are mol%, and 47.3 ≦ d ≦ 93.
0, 4.0 ≦ e ≦ 19.5, 2.0 ≦ f ≦ 21.7,
1.0 ≦ g ≦ 14.5. ) And represented by the general formula A
When represented by (B _y B ′ _1-y ) O ₃ , A is Pb,
B and B 'are the same or different divalent to hexavalent metals, (B _y B' _1-y ) is tetravalent, and A / (B _y B ' _1-y )
Is a main component having a value of 0.99 to 1.00, and 100 to 20,000 ppm by weight of Si as an auxiliary component is added as SiO ₂ (excluding colloid). is there. According to the present invention, 900 ° C. to 1100 ° C.
Can be fired at a low temperature of not more than 1000 ° C. and has a dielectric constant of 1000
A dielectric porcelain composition is obtained, which can obtain a porcelain as large as 0 or more and excellent in mechanical strength. Therefore, when the dielectric ceramic composition according to the present invention is used, relatively inexpensive silver or silver alloy can be used as the electrode material of the laminated ceramic capacitor. Moreover, if the dielectric porcelain composition according to the present invention is used,
A multilayer ceramic capacitor having excellent mechanical strength can be obtained. Further, when the dielectric ceramic composition according to the present invention is used, a ceramic capacitor having a high insulation resistance value and excellent reliability at high temperatures can be obtained. The above objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings. EXAMPLES Example 1 Industrial-use PbO, MgO, Nb ₂ O ₅ ,
Each raw material was weighed using TiO ₂ and ZnO so that a porcelain composition having a composition ratio shown in Table 1 was finally obtained. In Table 1, A / (B _y B ′ _1-y ) represents Pb, Ti,
(Mg _1/3 Nb _2/3 ) and (Zn _1/3 Nb _2/3 ). In Table 1, those marked with * are comparative examples of the present invention and are outside the scope of the present invention. [Table 1] [0013] After each weighed raw material is 100 g and mixed,
The mixture was calcined at 700 ° C. for 2 hours and pulverized by a ball mill. SiO ₂ was added to the ground mixture at the ratio shown in Table 1,
After wet mixing with a ball mill again, evaporate the water,
A porcelain raw material powder was obtained. A ceramic slurry was prepared by adding a polyvinyl butyral-based binder and an organic binder such as ethanol to the above porcelain raw material powder and then wet-mixing with a ball mill. Thereafter, the ceramic slurry is formed into a sheet by the doctor blade method, and the thickness is set to 20.
A rectangular ceramic green sheet of μm was obtained. next,
A conductive paste containing silver as a main component was printed on the obtained ceramic green sheet to form a conductive paste layer for forming internal electrodes. Then, a plurality of ceramic green sheets on which the conductive paste layer was formed were laminated to obtain a laminate. Then, the obtained laminate was fired in air at a temperature shown in Table 2 for 2 hours to obtain a sintered ceramic body. In Table 2, those marked with * are comparative examples of the present invention and are outside the scope of the present invention. [Table 2] An electrode material made of silver is applied to both end surfaces of the obtained porcelain sintered body, and baked at 750 ° C. in the air to form external electrodes electrically connected to the internal electrodes. Thus, a laminated ceramic capacitor as a sample was obtained. The outer diameter of the laminated ceramic capacitor used as a sample is 1.6 mm in width, 3.2 mm in length, 1.2 mm in thickness, and 13 μm in thickness of the dielectric ceramic layer between the internal electrodes. there were. The total number of effective dielectric ceramic layers was 10, and the facing area per layer was 2.1 mm ² . With respect to these samples, a voltage of 1 kHz and 1 Vrms was applied between external electrodes by an automatic bridge type measuring instrument, and a capacitance C and a dielectric loss tan at 20 ° C.
δ was measured. Then, the dielectric constant ε was determined from the capacitance C and the like. Further, these samples were measured at -25.degree.
And at 80 ° C., respectively,
-25 ° C and 80 with reference to the capacitance C at
The rate of change of capacitance Tcc (%) at ° C. was determined. Next, a voltage of 16 V was applied to these samples between the external electrodes with an insulation resistance meter for 2 minutes, and the temperature was adjusted to 20 ° C.
Was measured for the insulation resistance R. Then, the product of the capacitance C and the insulation resistance R before the moisture resistance test described later, that is, the CR product was obtained. Further, with respect to these samples, a temperature of 80
After a humidity resistance test was performed for 1000 hours in an atmosphere at 95 ° C. and a humidity of 95%, the capacitance C and the insulation resistance R after the humidity resistance test were measured, and the CR product after the humidity resistance test was determined. The bending strength of these samples was measured using a bending strength measuring apparatus 10 shown in FIG. In FIG. 1, reference numeral 12 denotes a multilayer ceramic capacitor under test as a sample, and reference numeral 14 denotes a sample holder. The laminated ceramic capacitor 12 placed on the sample holder 14 is pressed by a pressing pin 16. Then, the pressurized pressure is displayed by the tension gauge with a placement needle 18. In this measurement, the distance between the jigs of the sample holder 14 was 2 mm. Table 2 shows the above results. Example 2 PbO, NiO, Nb ₂ O ₅ , T having a purity of 99.9% or more
using iO ₂ , ZnO, WO ₃ and MgO as starting materials,
Each raw material was weighed so that a porcelain composition having a composition ratio shown in Table 3 was finally obtained. In Table 3, A / (B _y B '
_1-y ) is Pb, Ti, (Mg _1/3 Nb _2/3 ), (N
i _1/3 Nb _2/3 ) and (Zn _1/2 W _1/2 ). In Table 3, those marked with * are comparative examples of the present invention and are outside the scope of the present invention. [Table 3] After each weighing material was made 100 g and mixed,
The mixture was calcined at 750 ° C. for 2 hours and pulverized with a ball mill. SiO ₂ was added to the pulverized mixture at the ratio shown in Table 3,
After wet mixing with a ball mill again, evaporate the water,
A porcelain raw material powder was obtained. A ceramic slurry was prepared by adding a polyvinyl butyral-based binder and an organic binder such as ethanol to the above-mentioned porcelain raw material powder and wet-mixing with a ball mill. Thereafter, the ceramic slurry is formed into a sheet by the doctor blade method, and the thickness is set to 20.
A rectangular ceramic green sheet of μm was obtained. next,
A conductive paste containing silver as a main component was printed on the obtained ceramic green sheet to form a conductive paste layer for forming internal electrodes. Then, a plurality of ceramic green sheets on which the conductive paste layer was formed were laminated to obtain a laminate. Then, the obtained laminate was fired in air at a temperature shown in Table 4 for 2 hours to obtain a sintered ceramic body. In Table 4, those marked with * are comparative examples of the present invention and are outside the scope of the present invention. [Table 4] An electrode material made of silver was applied to both end surfaces of the obtained ceramic sintered body, and baked at a temperature of 750 ° C. in air to form external electrodes electrically connected to the internal electrodes. Thus, a laminated ceramic capacitor as a sample was obtained. The outer diameter of the laminated ceramic capacitor used as a sample is 1.6 mm in width, 3.2 mm in length, 1.2 mm in thickness, and 13 μm in thickness of the dielectric ceramic layer between the internal electrodes. there were. The total number of effective dielectric ceramic layers was 10, and the facing area per layer was 2.1 mm ² . For these samples, the dielectric constant ε, the dielectric loss tan δ, the capacitance change rate Tcc at −25 ° C. and 80 ° C. based on the capacitance at 20 ° C., CR product before and after the moisture resistance test,
And the precipitation strength was determined. Table 4 shows the above results. As is clear from the results shown in Tables 2 and 4, the dielectric ceramic compositions falling within the scope of the present invention can be fired at a low firing temperature of 1100 ° C. or lower. Moreover, it can be seen that the porcelain made of the dielectric porcelain composition within the scope of the present invention has a high dielectric constant of 10,000 or more, exhibits excellent moisture resistance, and has excellent mechanical strength. However, it can be seen that the following characteristics are exhibited outside the scope of the present invention. As shown in Sample Nos. 6 and 16, A / (B _y
When the value of B ′ _1-y ) is less than 0.99, the firing temperature is 1
When the temperature exceeds 100 ° C., the dielectric constant also decreases. When the value of A / (B _y B ′ _1-y ) exceeds 1.00 as in Sample Nos. 7 and 17, the firing temperature is lowered, but the bending strength is extremely lowered. As shown in sample numbers 8, 9, 18, and 19,
_When the addition amount of ₂ is less than 100 ppm, both the bending strength and the moisture resistance decrease. When the addition amount of SiO ₂ exceeds 20,000 ppm as in Sample Nos. 10 and 20, the transverse rupture strength increases, but the dielectric constant (ε) is 100%.
00 or less. As described above, in the laminated ceramic capacitor using the dielectric ceramic composition according to the present invention, the dielectric constant of the ceramic forming the dielectric layer exhibits a value of 10,000 or more, and the firing temperature is low. Relatively inexpensive silver or silver alloy can be used as the material for the internal electrodes, and the insulation resistance is high, the mechanical strength is excellent, and the reliability at high temperatures is excellent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustrative view showing the bending strength measuring apparatus for measuring the bending strength of the sample. [Description of Signs] 10 Flexural strength measuring device 12 Laminated ceramic capacitor 14 Sample holder 16 Pressure pin 18 Tension gauge with placement needle

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Yukio Sakabe               2-26-10 Tenjin, Nagaokakyo-shi, Kyoto, Japan               Expression company Murata Manufacturing                (56) References JP-A-2-263752 (JP, A)                 JP-A-57-27974 (JP, A)                 JP-A-4-108658 (JP, A)                 JP-A-51-83751 (JP, A)

Claims (1)

(57) [Claims] [Claim 1] aPb (Mg _1/3 Nb _2/3 ) O ₃ -bPb
TiO ₃ -cPb (Zn _1/3 Nb _2/3 ) O ₃ (where a,
b and c are mol%, and 59.5 ≦ a ≦ 98.5, 0.
5 ≦ b ≦ 10.0 and 1.0 ≦ c ≦ 40.0. ),
Or dPb (Mg _1/3 Nb _2/3 ) O ₃ -ePbTiO _3-
fPb (Ni _1/3 Nb _2/3 ) O ₃ -gPb (Zn
_1/2 W _1/2 ) O ₃ (where d, e, f, and g are mol%, and 47.3 ≦ d ≦ 93.0, 4.0 ≦ e ≦ 19.5,
2.0 ≦ f ≦ 21.7 and 1.0 ≦ g ≦ 14.5. ) And represented by the general formula A (B _y B ' _1-y ) O ₃ , A is Pb, B and B' are the same or different divalent to hexavalent metals, and B _y B _'1-y) is a tetravalent, a / (B _y B' as a main component value of _1-y) is from 0.99 to 1.00, Si as an auxiliary component SiO ₂ (provided that ,
Excluding colloids) by weight ratio of 100-20,000p
A dielectric porcelain composition characterized by being baked with pm added.