JPH05279110A - Ceramic composition - Google Patents

Abstract

PURPOSE:To improve dielectric constant and insulation resistance of a ceramic composition by showing a three-component composition expressed by a specific formula using a three-component composition figure and replacing a part of Pb of a composition on a line binding each point or a composition in the range of a composition enclosed by each point with La. CONSTITUTION:PbO, MgO, WO3, Nb2O5, ZnO, TiO2 and La2O3 are subjected to wet mixing at a prescribed blend ratio and calcined at 750-850 deg.C. Then the calcined material is pulverized and dried and an organic binder is added thereto and the mixture is kneaded and formed to afford a formed product. The formed product is burned to form a three-component composition expressed by the formula (x+y+z=1.0). The three-component composition is expressed by three- component figure consisting of a composition on lines binding the point (a) (x=0.98, y=0, z=0.02), the point (b) (x=0.43, y=0.55, z=0.22), the point (c) (x=0.20, y=0.20, z=0.60) and the point (d) (x=0.40, y=0 and z=0.60) and slant line region enclosed by these four points. Since the main composition and a composition obtained by replacing 0.01-30mol% of Pb with La have high dielectric constant and insulation resistance, the composition is suitable as a ceramic composition for condenser.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porcelain composition, and more particularly to a porcelain composition having a high dielectric constant and insulation resistance and a small temperature change rate of the dielectric constant.

[0002]

2. Description of the Related Art Conventionally, barium titanate (BaTiO ₃ ) system has been well known as a high dielectric constant porcelain composition,
Calcium titanate (CaTiO ₃ ), lead titanate (P
The temperature characteristics are improved by adding and substituting bTiO ₃ ).

[0003]

When a material having a small temperature change rate is realized by a conventional material, the obtained dielectric constant is about 2000 at most, which is too small as a material for a capacitor. In recent years, a lead-based composite perovskite compound has been reported as a material that is sintered at a low temperature and has a high dielectric constant. For example, magnesium lead niobate [Pb (Mg
_1/3 Nb _2/3 ) O ₃ ], nickel lead niobate [Pb (N
i _1/3 Nb _2/3 ) O ₃ ] and lead titanate [PbTiO ₃ ]
The three-component composition consisting of (3) has a dielectric constant of 20,000 or more, but has a drawback that the rate of change in dielectric constant with temperature is not sufficiently small. From the above, it was difficult to design a capacitor having a small rate of change in capacitance with temperature. The present invention has been made to solve the above-described conventional problems, and satisfies the excellent characteristics of the above three-component composition,
It is intended to provide a porcelain composition having a high specific resistance value and a small rate of change in dielectric constant with temperature.

[0004]

The present invention is directed to lead magnesium tungstate [Pb (Mg _1/2 W _1/2 ) O ₃ ], lead titanate [PbTiO ₃ ] and zinc lead niobate [P
[Pb (Mg _1/2 W _1/2 ) O ₃ ] x [PbTiO ₃ ] y [Pb] is a three-component composition composed of b (Zn _1/3 Nb _2/3 ) O ₃ ].
(Zn _1/3 Nb _2/3 ] O ₃ ] z (where x + y + z = 1.
0), in the three-component composition diagram, the following composition points, (x = 0.98, y = 0, z = 0.02) (a) (x = 0.43, y = 0.55, z = 0.02) ... (b) (x = 0.20, y = 0.20, z = 0.60) ... (c) (x = 0.40, y = 0, z = 0.60) ... (d) on the line connecting the points and within the composition range surrounded by these four points, lead (Pb) of the main component composition is replaced with lanthanum (La).
It is a porcelain composition characterized by being replaced by 0.01 to 30 mol%.

FIG. 1 shows a three-component composition diagram showing the main component composition range in the present invention. In the figure, (a) to (d) represent respective composition points, and the composition range included in the present invention is the range indicated by the diagonal lines in the figure and the boundary line thereof. The main composition of the present invention and the composition in which the amount of substitution of La is out of the scope of claims are not suitable as a porcelain composition for a capacitor because of the adverse effect that the absolute value of the dielectric constant and the specific resistance decrease. Therefore, it is limited to the above range.

[0006]

EXAMPLES Examples of the present invention will be described in detail below. Example 1 Lead oxide (PbO), magnesium oxide (MgO), tungsten oxide (WO ₃ ), niobium oxide (Nb ₂ O ₅ ), zinc oxide (ZnO), titanium oxide (Ti) were used as starting materials.
O ₂ ) and lanthanum oxide (La ₂ O ₃ ) are used and weighed so that the compounding ratios shown in Table 1, Table 3 and Table 5 are obtained. Next, the weighed materials are wet-mixed in a ball mill, then calcined at 750 to 850 ° C., the powder is crushed by a ball mill, filtered, dried, and then an organic binder is added to adjust the particle size, followed by pressing. Two discs having a thickness of about 16 mm and a thickness of about 2 mm and a cylinder having a diameter of about 16 mm and a thickness of about 10 mm were produced. Next, samples in these composition ranges are set to 950 to 10
Firing was performed at a temperature of 50 ° C. for 1 hour.

The density was determined on the fired cylinder using the Archimedes method. Next, silver electrodes were baked on the upper and lower surfaces of the disc at 600 ° C., and the frequency was 1 kHz and the voltage was 1 Vr. m. s, the capacitance and the dielectric loss were measured at room temperature to obtain the dielectric constant. Next, a voltage of 50 V was applied for 1 minute with an insulation resistance meter, the insulation resistance was measured, and the specific resistance was calculated.

The main component of the porcelain thus obtained,
[Pb (Mg _1/2 W _1/2 ) O ₃ ] x [PbTiO ₃ ] y [Pb
The compounding ratios x, y, z and the La substitution amount of (Zn _1/3 Nb _2/3 ] O ₃ ] z are shown in Tables 1, 3 and 5, and the dielectric constant at room temperature, the specific resistance and the dielectric constant The rate of change (based on the dielectric constant at 20 ° C.) is shown in Tables 2, 4, and 6. In the table, the sample number, * indicates a composition having a La substitution amount outside the range of the present invention, ** indicates a composition whose main component composition is out of the range of the present invention .. As is clear from Tables 1 to 6, Pb
(Mg _1/2 W _1/2 ) O ₃ -PbTiO ₃ -Pb (Zn _1/3 N
The porcelain composition of the present invention in which lead (Pb) in the b _2/3 ) O ₃ ternary composition is replaced by lanthanum (La) in an amount of 0.01 to 30 mol% retains a high specific resistance and has a dielectric constant temperature of An excellent material is provided as a ceramic composition for a monolithic ceramic capacitor having a small change rate.

[0009]

[Table 1] Mixing ratio of sample numbers 1 to 20 ───────────────────────────────── Sample Pb (Mg _{1 / 2} w _1/2 ) O ₃ PbTiO ₃ Pb (Zn _1/3 Nb _2/3 ) O ₃ La Substitution number Number (mol%) (mol%) (mol%) (mol%) ─────── ─────────────────────────── 1 ^* 70 0 30 0 2 ^* 50 10 40 0 3 50 10 40 10 4 ^* 40 10 50 0 5 40 10 50 5 6 ^* 30 10 60 0 7 ^** 25 10 65 08 8 ^* 40 20 40 0 9 40 20 40 0.01 10 40 20 40 10 11 40 20 40 20 12 ^* 35 20 45 0 13 ^* 30 20 50 0 14 30 20 50 10 15 30 20 50 30 16 ^* 20 20 60 0 17 20 20 60 0.01 18 20 20 60 2 19 20 20 60 10 20 20 20 60 30 ───────────── ─────────────────────

[0010]

[Table 2] Characteristics of sample numbers 1 to 20 ────────────────────────────────── Sample dielectric constant Specific resistance Percentage change in permittivity (Ωcm) ───────────── −30 ℃ (%) 85 ℃ (%) ──────────────── ─────────────────── 1 ^* 2870 3.8 × 10 ¹⁴ ＋20.2 −31.6 2 ^* 3700 5.3 × 10 ¹³ +15.8 −28.7 3 3300 1.5 × 10 ¹⁴ ＋16 .5 −23.8 4 ^* 3950 7.3 × 10 ¹³ +16.5 −27.4 5 3530 1.6 × 10 ¹⁴ +17.1 −24.8 6 ^* 3400 5.6 × 10 ¹² −21.1 −18.5 7 ^** 2920 2.8 × 10 ¹¹ −36.3 −4.3 8 ^* 6180 8.8 × 10 ¹² −8.5 −29.8 9 6070 1.4 × 10 ¹³ −6.3 −31.5 10 5160 1.9 × 10 ¹³ +1.2 −26.1 11 4100 2.8 × 10 ¹³ +11.3 −25.5 12 ^* 7420 4.2 × 10 ¹² −28.5 −27.5 13 ^* 8480 2.6 × 10 ¹² −44.3 −10.3 14 6870 5.8 × 10 ¹² −36.1 −12.5 15 4750 1.9 × 10 ¹³ −26.3 −17.5 16 ^* 10060 1.2 × 10 ¹² −55.6 −1.2 17 9 900 1.6 × 10 ¹² −53.7 −2.5 18 9260 1.9 × 10 ¹² −43.1 −7.6 19 8750 2.8 × 10 ¹² −37.3 −16.3 20 7300 4.3 × 10 ¹² −28.5 −25.1 ─────────── ───────────────────────

[0011]

[Table 3] Mixing ratio of sample numbers 21 to 40 ────────────────────────────────── Sample Pb (Mg _1/2 w _1/2 ) O ₃ PbTiO ₃ Pb (Zn _1/3 Nb _2/3 ) O ₃ La Substitution number Number (mol%) (mol%) (mol%) (mol%) ───── ───────────────────────────── 21 ^* 20 20 60 40 22 22 ^** 15 20 65 0 23 ^* 40 30 30 0 24 40 30 30 10 25 40 30 30 30 26 ^* 30 30 40 0 27 ^** 25 30 45 0 28 ^* 40 40 20 0 29 40 40 20 10 30 ^* 35 40 25 0 31 35 40 25 0.01 32 35 40 25 1 33 35 40 25 10 34 35 40 25 30 35 ^* 35 40 25 40 36 ^** 30 40 30 0 37 ^* 40 50 10 0 38 40 50 10 1 39 40 50 10 10 40 40 50 10 30 ───────── ───────────────────────────

[0012]

[Table 4] Characteristics of Sample Nos. 21 to 40 ────────────────────────────────── Sample dielectric constant Specific resistance Dielectric constant change number (Ωcm) ──────────── −30 ℃ (%) 85 ℃ (%) ───────────────── ────────────────── 21 ^* 4730 1.1 × 10 ¹² −53.1 −23.5 22 ^** 9850 3.5 × 10 ¹¹ −65.1 +3.5 23 ^* 10400 1.4 × 10 ¹³ − 45.6 -28.0 24 8310 3.1 x 10 ¹³ -43.2 -29.5 25 5300 3.8 x 10 ¹³ -40.6 -27.3 26 ^* 8680 3.6 x 10 ¹² -29.8 -11.4 27 ^** 7420 5.6 x 10 ¹¹ -19.5 -2.6 28 ^* 9680 7.4 × 10 ¹² -51.3 -17.5 29 8310 1.1 × 10 ¹³ -33.1 -17.2 30 ^* 10 220 5.3 × 10 ¹² -54.7 -13.5 31 100 30 7.1 × 10 ¹² -50.5 -18.7 32 9260 8.8 × 10 ¹² -45.3 -16.1 33 33 8110 1.2 × 10 ¹³ −41.3 −21.6 34 6520 1.5 × 10 ¹³ −31.7 −28.1 35 ^* 3700 6.1 × 10 ¹² −35.3 −25.6 36 ^** 8150 8 .6 × 10 ¹¹ −59.8 −9.8 37 ^* 12,500 2.1 × 10 ¹² −51.2 −16.3 38 11980 2.3 × 10 ¹² −50.3 −17.1 39 39850 4.3 × 10 ¹² −31.1 −22.1 40 6870 7.8 × 10 ¹² −22.1 −11.5 ───────────────────────────────────

[0013]

[Table 5] Mixing ratio of sample numbers 41 to 42 ─────────────────────────────────── Sample Pb (Mg _1/2 w _1/2 ) O ₃ PbTiO ₃ Pb (Zn _1/3 Nb _2/3 ) O ₃ La Substitution number Number (mol%) (mol%) (mol%) (mol%) ───── ───────────────────────────── 41 ^* 49 49 2 0 42 49 49 2 10 ─────────── ────────────────────────

[0014]

[Table 6] Characteristics of sample Nos. 41 to 42 ────────────────────────────────── Sample dielectric constant Specific resistance Dielectric constant change number (Ωcm) ──────────── −30 ℃ (%) 85 ℃ (%) ───────────────── ────────────────── 41 ^* 7830 5.6 × 10 ¹² −46.8 −28.3 42 6320 9.5 × 10 ¹² −37.8 −32.5 ──────────── ───────────────────────

[0015]

As described above, the porcelain composition of the present invention has a high specific resistance value and a small rate of change in dielectric constant with temperature.
Therefore, when the porcelain composition of the present invention is used, there is an effect such that the rate of change in capacitance with temperature is small and a highly reliable laminated ceramic capacitor can be designed.

[Brief description of drawings]

FIG. 1 shows Pb (Mg _1/2) showing the main component composition range of the present invention.
_{W 1/2) O 3 -PbTiO 3 -Pb} (Zn 1/3 Nb 2/3) O 3
It is a three-component composition diagram.

Claims (1)

[Claims] 1. Magnesium lead tungstate [Pb
(Mg _1/2 W _1/2 ) O ₃ ], lead titanate [PbTiO ₃ ] and lead zinc niobate [Pb (Zn _1/3 Nb _2/3 ) O ₃ ].
A three-component composition consisting of [Pb (Mg _1/2 W _1/2 ) O ₃ ] x
When expressed as [PbTiO _3] y [Pb (Zn _1/3 Nb _2/3 ] O ₃ ] z (where x + y + z = 1.0), in the three-component composition diagram, the following composition points, (x = 0 .98, y = 0, z = 0.02) (x = 0.43, y = 0.55, z = 0.02) (x = 0.20, y = 0.20, z = 0.60) ) (X = 0.40, y = 0, z = 0.60) on the line connecting the respective points and within the composition range surrounded by these four points, lead (Pb) of the main component composition is replaced with lanthanum (La). )
A porcelain composition characterized by being replaced by 0.01 to 30 mol%.