JPH0644409B2 - Dielectric porcelain composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high dielectric ceramic composition that can be fired at a temperature of 1000 ° C. or lower.

2. Description of the Related Art Barium titanate-based materials have been widely used as high dielectric constant materials for ceramic capacitors. However, since this material has a high firing temperature of 1300 to 1400 ° C.,
When used in a monolithic ceramic capacitor, expensive platinum or palladium electrodes are required as internal electrodes. On the other hand, since the firing temperature is a low temperature of 1150 ° C. or lower, a lead composite perovskite-based dielectric has been developed as a material that can use a cheaper silver-based electrode as the internal electrode. For example, PbTiO ₃ , Pb (Ni _1/2 W
A system containing _½ ) O ₃ is disclosed in JP-A-59-57953.
The material disclosed in Japanese Patent Publication No.
_The material disclosed in JP-A-57-157407 is known as a system containing ₃ , Pb (Mg _1/2 W _1/2 ) O ₃ .

Problems to be Solved by the Invention PbTiO ₃ —Pb (Ni _1/2 W _1/2 ) O ₃ -based solid solutions have a high dielectric constant, but their dielectric properties are Pb.
Since it is determined by the ratio of TiO ₃ and Pb (Ni _1/3 Nb _2/3 ) O ₃ , it is not possible to obtain a material having arbitrary permittivity and temperature characteristics, and the rate of change in permittivity with temperature is large. .
The solid solution of PbTiO ₃ —Pb (Mg _1/2 W _1/2 ) O ₃ system has high insulation resistance, but its dielectric constant is 40.
Only materials with low values below 00 can be obtained. The present invention has been made in view of such problems, and an object thereof is to provide a porcelain composition which can obtain a high dielectric constant of 4000 or more and a relatively small temperature change rate.

Means for Solving Problems PbTiO ₃ and Pb (Ni _1/2 W _1/2 ) O ₃ solid solution, and Pb (Mg) as a third component
Add _1/2 W _1/2 ) O ₃ .

By solid solution _{Pb (Mg 1/2 W 1/2) O} 3 in binary compositions of action _{PbTiO 3 -Pb (Ni 1/2 W 1/2} ) O 3, and has a high dielectric constant It is possible to obtain a dielectric material whose rate of change is relatively small.

Example As a starting material, chemically high purity PbO, TiO ₂ ,
NiO, MgO, and WO ₃ were 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, dried, and then lyophilized and crushed with a Lykai machine, and then 5 wt% of the powder amount of water is added, and the molding pressure is 500 kg / cm ² and the diameter is 60 mm and the height is about 50 mm. Was molded into a cylindrical shape. This was placed in an alumina crucible, covered with the same material, and calcined at 750 ° C. to 800 ° 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 agate stones, and this was suction filtered to separate most of the water content, followed by drying. After repeating the above calcination, crushing, and drying several times, add 6 wt% of polyvinyl alcohol 6 wt% aqueous solution to this powder, granulate through a 32 mesh sieve, and with a molding pressure of 1000 kg / cm ² , a diameter of 13 mm It was formed into a cylindrical shape having a size of about 5 mm. The molded product was heated to 700 ° C. in air and held for 1 hour to burn out the polyvinyl alcohol content, and after cooling, transfer it to a magnesia porcelain container,
A lid of the same quality was put on, the temperature was raised to 400 ° C./hr in air, the temperature was kept for 2 hours, and the temperature was lowered at 400 ° 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 was calculated from the value of 1 minute after applying a voltage of 1 kV / mm at 20 ° C. 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, ferroelectric phase transition point, and resistivity.

The figures show the samples shown in Table 1 for PbTiO ₃ , Pb (Mg
_1/2 W _1/2 ) O ₃ , Pb (Ni _1/2 W _1/2 ) O
_It is shown in a triangular composition diagram in which ₃ is an end component, and the range of the hatched line shows the range of the present invention.

For compositions outside the scope of the invention, No. 1 in Table 1 was used. The sample marked with * is given as an example, but the optimum firing temperature is 1000 ° C.
Or more, the dielectric constant is 4000 or less, and the temperature change rate of the dielectric constant is large, or any of these three points is difficult. Compositions within the scope of the invention overcome all three of the above problems.

Effects of the Invention According to the dielectric ceramic composition of the present invention, it is possible to obtain a dielectric constant having a high dielectric constant of 4000 or more and a small change rate thereof. Furthermore, since this dielectric can be fired at a temperature of 1000 ° C. or less, it is possible to use an Ag—Pd-based material as the internal electrode of the multilayer capacitor element, and an inexpensive multilayer capacitor can be realized, which is of great industrial value. is there.

[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. PbTiO ₃ , Pb (Mg
_1/2 W _1/2 ) O ₃ , and Pb (Ni _1/2 W
_A ternary porcelain composition consisting of _1/2 ) O ₃ was added to PbTi _x
(Mg _1/2 W _1/2 ) _y (Ni _1/2 W _1/2 ) _z O
When expressed as ₃ (however, x + y + z = 1.0), Pb
TiO ₃ , Pb (Mg _1/2 W _1/2 ) O ₃ , Pb (N
In the ternary composition diagram shown by the triangular coordinates with i _1/2 W _1/2 ) O ₃ as the vertex, the following composition points A, B, C,
DA: x = 0.55 y = 0.01 z = 0.44 B: x = 0.45 y = 0.35 z = 0.20 C: x = 0.25 y = 0.35 z = 0 .40 D: x = 0.45, y = 0.01, z = 0.55, which is in the region of a square system having the apex thereof.