JPH068206B2 - Dielectric porcelain composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high dielectric constant dielectric ceramic composition that is fired at a firing temperature of 1000 ° C. or less, and more particularly to a composition having a high resistivity at high temperature.

2. Description of the Related Art In recent years, in ceramic capacitors, miniaturization of elements,
Due to the demand for larger capacity, multilayer ceramic capacitors are rapidly becoming popular. Multilayer ceramic capacitors are usually manufactured by a process of integrally firing internal electrodes and ceramics. Conventionally, a barium titanate-based material has been used as a high dielectric constant ceramic capacitor material, but since the firing temperature is as high as about 1300 ° C., an expensive metal such as Pt or Pd is used as the internal electrode material. There was a need.

On the other hand, a lead composite perovskite-based material has been developed which can be fired at 1100 ° C. or lower and can use an Ag-based material that is cheaper than the former as an internal electrode.

Of these, for example, pb (Zn _1/3 Nb _2/3 ) O ₃ and Pb (Mg _1/3
The one containing Nb _2/3 ) O ₃ is disclosed in JP-A-57-25607.
The materials described in Japanese Patent Publication No. 57-27974 and Japanese Patent Publication No. 57-27974 are known.

Problems to be Solved by the Invention Pb (Zn _1/3 Nb _2/3 ) O ₃ -Pb (Mg _1/3 Nb _2/3 ) O ₃ based solid solutions have high dielectric constants, but especially at high temperatures. Had a tendency to decrease its resistance value.

In the present invention, in view of such problems, Pb (Zn _1/3 Nb _2/3 ) O ₃ -P
b (Mg _1/3 Nb _2/3 ) O ₃ system's high dielectric constant
It is an object of the present invention to provide a dielectric ceramic composition having a high resistance value at high temperature.

Means for Solving Problems Pb (Zn _1/3 Nb _2/3 ) O ₃ -Pb (Mg _1/3 Nb _2/3 ) O ₃ The third component, Pb (Zn _1/2 W _{1 / 2)} and O ₃ composition was added.

In the composition within the scope of the present invention, Pb (Zn _1/2 W _1/2 ) O ₃ is added to P
By adding b (Zn _1/3 Nb _2/3 ) O ₃ -Pb (Mg _1/3 Nb _2/3 ) O ₃ system, it is possible to obtain high reliability as a multilayer capacitor element at a firing temperature of 1000 ° C. or less. Thus, a dense sintered body can be obtained, an Ag-based material can be used for the internal electrode, and an element having a high resistance value at high temperature can be obtained.

Example Starting materials were chemically high-purity PbO, MgO, Nb ₂ O ₅ , ZnO,
WO ₃ was used. These were subjected to purity correction, weighed in predetermined amounts, and wet-mixed for 17 hours in a ball mill using agate stones and pure water as a solvent. This is suction filtered to separate most of the water content, then dried, and then lyophilized and crushed with a Lykai machine, and then 5 wt% of the powder amount of water is added to give a diameter of 6
Molding pressure of 500 kg / cm ^{2 in} a cylindrical shape of 0 mm and height of about 50 mm
It was molded in. This was placed in an alumina crucible, covered with the same material, and calcined at 750 ° C. to 880 ° C. for 2 hours. Next, the calcined product was roughly crushed in an alumina mortar, and further crushed for 17 hours in a ball mill using pure stone as a solvent with a pure stone as a solvent, and this was suction-filtered to separate most of the water content and then dried. After repeating the above calcination, pulverization and drying several times, add 6 wt% of polyvinyl alcohol aqueous solution to this powder, and add 3 wt%
Granulate through a 2-mesh sieve, molding pressure 1000 kg
It was molded into a columnar shape having a diameter of 13 mm and a height of about 5 mm at / cm ² .
The molded product is heated to 700 ° C in air and kept for 1 hour to burn out the polyvinyl alcohol content, and after cooling, transfer it to a magnesia porcelain container, cover it with the same material, and in air to 400 ° C / hr up to a predetermined temperature After heating for 2 hours and holding at 400
The temperature was lowered at ° C / hr.

The fired product is cut into a disc with a thickness of 1 mm, and Cr-Au is cut on both sides.
Was vapor-deposited, and the dielectric constant and tan δ were measured under an electric field of 1 kHz and 1 V / mm. The resistivity is 1k at 20 ℃ and 85 ℃.
It was determined from the value of 1 minute after applying a voltage of V / mm.

The firing temperature was the temperature at which the density of the fired product was the highest.

Table 1 shows components of the composition range and peripheral composition of the present invention, firing temperature, dielectric constant, tan δ, temperature change rate of dielectric constant, and resistivity.

The figure shows the Pb (Zn _1/3 Nb _2/3 ) O ₃ -Pb (M
It is shown in the triangular composition diagram with g _1/3 Nb _2/3 ) O ₃ -Pb (Zn _1/2 W _1/2 ) O ₃ as the end component, and is within the scope of the invention of diagonal lines.

For compositions outside the scope of the invention, the samples marked with * in Table 1 were taken as an example, but the optimum firing temperature was 110.
It has any of the three points of exceeding 0 ° C., having a dielectric constant of 4000 or less, and having a low resistance value at high temperature, or having a duplicated point thereof. Compositions within the scope of the invention overcome all three of the above problems.

EFFECTS OF THE INVENTION According to the present invention, a dense sintered body for obtaining high reliability as a multilayer capacitor element can be obtained at a temperature of 1000 ° C. or less, and an Ag-based material can be used as an internal electrode. And an excellent dielectric ceramic composition having a dielectric constant of 4000 or more and a high resistivity at high temperature can be obtained.

[Brief description of drawings]

The figure is a triangular composition diagram showing the component composition of the porcelain composition according to the present invention.

Claims (1)

[Claims] 1. Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Zn _1/3 Nb _2/3 ) O ₃
A ternary porcelain composition consisting of Pb (Zn _1/2 W _1/2 ) O ₃ was added to Pb (Mg _1/3 Nb _2/3 ) _x (Zn _1/3 Nb _2/3 ) _y (Zn _1/2 When expressed as W _1/2 ) _{zO 3} (where x + y + z = 1.00), Pb (M
g _1/3 Nb _2/3 ) O ₃ , Pb (Zn _1/3 Nb _2/3 ) O ₃ , Pb (Zn
_1/2 W _1/2 ) O _{3 In the} three-component composition diagram shown in triangular coordinates with the apex, the following composition points A, B, C, D A: x = 0.875 y = 0.100 z = 0.0025 B: x = 0.600 y = 0.375 z = 0.025 C: x = 0.300 y = 0.600 z = 0.100 D: x = 0.300 y = 0.400 Dielectric porcelain characterized by being in the composition range within a rectangular region with z = 0.300 as the apex. Composition.