JPH0688826B2 - High dielectric constant dielectric ceramic 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 1100 ° C. or less, and in particular, the rate of change of the dielectric constant with temperature is EI.
Satisfies the AJ standard Z5U characteristics (dielectric constant at + 10 ° C to + 85 ° C is + 22% to −56% with respect to + 20 ° C), and tan δ at 20 ° C is 200 ×.
Regarding those that satisfy the condition that is 10 ^-4 or less.

2. Description of the Related Art In recent years, with regard to ceramic capacitors, monolithic ceramic capacitors are rapidly becoming popular due to the demand for smaller size and larger capacity of elements. Multilayer ceramic capacitors are usually manufactured by a process of integrally firing internal electrodes and ceramics.
Conventionally, barium titanate-based materials have been used for high dielectric constant ceramic capacitor materials, but since the firing temperature is as high as 1300 ° C, expensive metals such as Pt and Pd are used as internal electrode materials. There was a need.

On the other hand, a silver 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.

The inventors have already reported that PbTiO ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Ni
_A high dielectric constant type dielectric ceramic composition composed of _1/2 W _1/2 ) O ₃ is proposed.

This system PbTiO ₃ -Pb (Mg _1/3 Nb _2/3 ) O ₃ does not impair the high dielectric constant characteristics of binary composition, and is densely sintered to obtain high reliability as a multilayer capacitor element. It has the excellent property that the body can be obtained at a firing temperature of 1100 ° C or lower.

Problems to be Solved by the Invention A porcelain composition comprising three components of PbTiO ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb (Ni _1/2 W _1/2 ) O ₃ is as described above. Although it has excellent characteristics, it has problems that tan δ at room temperature is slightly large, the rate of change in dielectric constant with temperature is rather large, and it is about the limit value of the Z5U standard. In view of the above problems in the present invention, a novel dielectric ceramic composition that does not impair the characteristics that the firing temperature is 1100 ° C. or less with a high dielectric constant, lowers tan δ at room temperature, and reduces the temperature change rate of the dielectric constant. The purpose is to provide.

Means for Solving Problems As a technical means for solving the above problems, as a result of examining various compositions as additives, Pb (Mn _1/3 Nb _2/3 ) O ₃ , Pb (Mn _{1 / 2} W _1/2 ) O ₃ ,, Pb (Mn _1/3 Nb
_The above problem was solved in a composition to which at least one of the group consisting of _2/3 ) O ₃ was added.

Action That is, the present invention is directed to Pb (Mn _1/3 Nb _2/3 ) O ₃ , Pb (Mn _1/2 W
_At least one of the group consisting of _1/2 ) O ₃ , Pb (Mn _1/3 Sb _2/3 ) O ₃ and PbTiO ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Ni _{1 / 2} W _1/2 ) O ₃
Tan δ at room temperature is 200 ×
It is possible to obtain a material that satisfies the Z5U standard by suppressing the temperature change rate of the dielectric constant to 10 ^-4 or less.

Example The starting material chemically highly pure _{Pb 3 O 4, MgO, NiO} , TiO 2, Nb 2
O ₅ , WO ₃ , MnO ₂ and Sb ₂ O ₃ were used. These were subjected to purity correction, weighed a predetermined amount, and wet-mixed in a ball mill for 17 hours using agate stones and pure water as a solvent. This is sucked and 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 form a cylinder with a diameter of 60 mm and a height of about 50 mm Pressure 500Kg / cm
Molded in ² . This was put 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 with alumina powder and further crushed for 17 hours by a ball mill using pure water as a solvent using agate boulders, which was suction-filtered to separate most of the water content and then dried. Calcination above,
After repeating crushing and drying several times, add 6wt% of polyvinyl alcohol aqueous solution to this powder in an amount of 6wt%, granulate through a 32 mesh sieve, and press at a molding pressure of 1000Kg / cm ² .
It was formed into a cylindrical shape with a height of 13 mm and a height of about 5 mm. Moldings in air
The temperature is raised to 700 ° C and kept for 1 hour to burn out the polyvinyl alcohol content. After cooling, this is transferred to a magnesia porcelain container, covered with the same quality, and heated in air to 400 ° C / predetermined temperature.
The temperature was raised at hr and held for 2 hours, and then lowered at 400 ° C / hr.

The fired product was cut into a cylinder with a thickness of 1 mm, Cr-Au was vapor-deposited on both surfaces, and the dielectric constant and tan δ were measured under an electric field of 1 KHz 1 V / mm.

The density of the fired product was measured by the Archimedes method, and the firing temperature that maximizes the density was taken as the optimum firing temperature.

Table 1 shows the claims of the present invention and the optimum firing temperature of the components of the peripheral composition, the dielectric constant at 20 ° C, tan δ, and the temperature change rate of the dielectric constant.

In the figure, the composition range of the main component of the present invention is shown as PbTiO ₃ -Pb (Mg _1/3 N
It is shown in the triangular composition diagram with b _2/3 ) O ₃ and Pb (Ni _1/2 W _1/2 ) O ₃ as the end components.

The reason for limiting the scope of the claims is that the composition out of the range has a tan δ at room temperature of more than 200 × 10 ^-4 , a dielectric constant lowers to 6000 or less, and a temperature change rate of the dielectric constant does not meet the Z5U standard. Due to having any of the above three points, or overlapping difficulties thereof.

As described above, the composition of the claims of the present invention is 11
It can be fired at a temperature of 00 ° C or less, Ag-based materials can be used as internal electrodes, and tan δ at room temperature is 200 × 10 ^-4
The following is an excellent high-dielectric-constant dielectric ceramic composition in which the rate of change in dielectric constant with temperature satisfies the EIAJ standard Z5U characteristics.

[Brief description of drawings]

The figure shows the composition range of the main component of the present invention as PbTiO ₃ , Pb (Mg _1/3 Nb
_2/3 ) O ₃ and Pb (Ni _1/2 W _1/2 ) O ₃ are shown in the triangular composition diagram with end components.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunichiro Kawashima 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hiroshi Ouchi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. PbTiO ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ and Pb (Ni
When representing the _1/2 W _1/2) consisting of O ₃ ternary ceramic composition as _{PbTi x (Mg 1/3 Nb 2/3)} y (Ni 1/2 W 1/2) z O 3 (provided that x + y + z = 1.00) in the ternary composition _{diagram, PbTiO 3, Pb (Mg 1/3} Nb 2/3) O 3, Pb (Ni
_1/2 W _1/2 ) The following composition points A, B, in triangular coordinates with O ₃ as the vertex
C, D, E A x = 2.5 y = 95 z = 2.5 B x = 12.5 y = 85 z = 2.5 C x = 40.0 y = 41 z = 19.0 D x = 20.0 y = 50 z = 30.0 Ex x = 2.5 y = 90 z = 7.5 for the main component composition in the composition range within the pentagonal region, Pb (Mn _1/3 Nb _2/3 ) O ₃ , Pb (Mn
0.5 W-2.5 wt% of at least one of the group consisting of _1/2 W _1/2 ) O ₃ and Pb (Mn _1/3 Sb _2/3 ) O ₃ -Based dielectric ceramic composition.