JPH0821260B2 - Dielectric porcelain composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high dielectric constant dielectric ceramic composition that is fired at 1100 ° C. or less, and in particular, a composition that can be fired in a low oxygen partial pressure atmosphere to obtain high resistivity. Regarding things.

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, 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, the inventors have found that Pba (Mg _1/3 Nb _2/3 ) xTiy (Ni _{1 /} that can be fired at 1100 ° C. or lower in a low oxygen partial pressure atmosphere and can use a base metal material containing copper as a main component as an internal electrode ₂ W _1/2 ) zO _{2 + a}
The dielectric porcelain composition represented by is proposed. This composition has a characteristic that it can be fired at a low temperature and has a high resistivity when fired under a low oxygen partial pressure, and it can also be used as a laminated capacitor element using copper or an internal electrode containing copper as a main component. It is a dielectric ceramic composition. On the other hand, in the manufacturing process of the ceramic multilayer capacitor element described above, the internal electrode copper or the alloy containing copper as a main component is not oxidized during firing, and the dielectric ceramic is reduced under oxygen partial pressure that does not reduce the resistance. Firing is required. In controlling the oxygen partial pressure, the higher the firing temperature, the more difficult it becomes to control the gas mixture ratio to obtain the optimum conditions. Therefore, there has been a demand for a dielectric ceramic that can be fired at a lower temperature and has a high resistivity.

Problems to be Solved by the Invention Pb _a (Mg _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 ) zO _{2 + a} A dielectric ceramic composition whose main component is a composition It is an object of the present invention to provide a dielectric ceramic composition having a low firing temperature and a high resistivity without impairing dielectric properties.

Means for Solving Problems For a porcelain composition represented by Pb _a (Mg _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 ) zO _{2 + a} (where x + y + z = 1) The composition contains copper oxide as an accessory component in an amount of 0.03 to 0.65% by weight in terms of Cu ₂ O.

Action In the system of the dielectric porcelain composition of the present invention, with respect to the composition containing no subcomponent, the composition containing the subcomponent is sintered at a low temperature, the decrease in the dielectric constant is small, and the increase in the dielectric loss is small, And the resistivity is equal to or improved.

Example The starting materials were chemically high purity PbO, MgO, Nb ₂ O ₅ , TiO ₂ and Ni.
O, WO ₃ and Cu ₂ O were used. These were subjected to purity correction, then weighed a predetermined amount, and wet mixed with a zirconia cobblestone using pure water as a solvent in a ball mill for 17 hours. This is suction-filtered to separate most of the water content, then dried, then charged and decomposed with a Lykai machine, and then added with 5 wt% of the powder amount of water to obtain a diameter of 6
It was molded into a cylinder with a height of 0 mm and a height of about 50 mm at a molding pressure of 500 kg / cm ² . Put this in an alumina crucible and cover with the same material.
It was calcined at 0 ° C to 760 ° 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 water as a solvent using zirconia cobblestone, which was suction filtered to separate most of the water content, and then dried. After repeating the above calcination, pulverization and drying several times, a 6 wt% aqueous solution of polyvinyl alcohol (6 wt%) was added to this powder, and the mixture was granulated through a 32 mesh sieve and molded at a molding pressure of 1000 kg / cm ² . The molded product was heated to 700 ° C. in the air and held for 1 hour to burn out the polyvinyl alcohol content. Approximately 1/3 of the volume of the above calcined powder is spread and 200 mesh MgO powder is applied to about 1/3.
Move to a magnesia porcelain container laid with mm, cover with the same quality,
Inserted in the core tube of the tubular electric furnace, and after degassing the inside of the core tube with a rotary pump, replace with N ₂ -H ₂ -H ₂ O mixed gas,
N ₂ so that the oxygen partial pressure (Po ₂ ) at the firing temperature is 1.0x10 ^-8 atm
The mixed gas was flowed while adjusting the mixing ratio of the H ₂ gas and H ₂ gas, the temperature was raised to a predetermined temperature at 400 ° C./hr, the temperature was held for 2 hours, and then the temperature was lowered at 400 ° C./hr. Po ₂ in the core tube was measured by a stabilized zirconia oxygen sensor inserted. FIG. 2 shows the structure of the magnesium porcelain container at the time of firing, and FIG. 3 shows a cross-sectional view of the inside of the core tube.

In FIG. 2, reference numeral 1 is a magnesia container, and the upper part thereof is sealed with a magnesia container lid 2. A calcined powder 3 was placed in the lower part of the magnesia container 1, and a magnesia powder 24 was placed thereon. Furthermore, the sample 5 was arranged on it.

The magnesia container 1 prepared as shown in FIG. 2 was placed in the core tube 6 as shown in FIG. 7 is a stabilized zirconia oxygen sensor.

The fired product was cut into a plate having 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 and 1 V / mm.
The resistivity was calculated from the value of 1 minute after applying a voltage of 1 kV / mm.

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

Table 1 shows the components of the composition range and peripheral composition of the present invention [a,
x, y, z are values expressed as Pb (Mg _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 ) zO _{2 + a} ], when fired in a low oxygen partial pressure atmosphere Firing temperature, dielectric constant, temperature change rate of dielectric constant (for 20 ℃),
Tan δ, resistivity and density are shown.

Fig. 1 shows the samples shown in Table 1 for PbTiO _{2 + a} Pb _a (Mg _1/3 N
b _2/3 ) O _{2 + a} -Pb _a (Ni _1/2 W _1/2 ) O _{2 + a} is shown in the triangular composition diagram, and the range of diagonal lines is the scope of the invention. .

In the composition outside the scope of the invention, when a is smaller than 0.985, even if copper oxide is added as a subcomponent, the firing temperature is higher than 1100 ° C, or the copper oxide is added until the firing temperature is lower than 1100 ° C. There is a problem that the permittivity decreases or the resistivity decreases, and when it exceeds 1100, the permittivity and the resistivity decrease. If the copper oxide as an accessory component is less than 0.03 wt%, the effect of improving the firing temperature will not be improved, and if it is more than 0.65 wt%, the dielectric properties, particularly the dielectric constant and the resistivity will be significantly reduced. Further, a composition in which x, y, z is out of the limited range has a problem that the Curie point largely deviates from room temperature and the dielectric constant decreases, or the temperature change rate of the dielectric constant increases. Compositions within the scope of the claims overcome all of the above problems.

In the low oxygen partial pressure atmosphere selected as the firing atmosphere, Po
₂ ; 1.0x10 ^-8 atm is lower than the equilibrium oxygen partial pressure of copper at the firing temperature, and it is considered that the metal hardly oxidizes.

EFFECTS OF THE INVENTION According to the present invention, it is possible to obtain a dense and high-resistivity sintered body for obtaining high reliability as a multilayer capacitor element by firing in a low oxygen partial pressure atmosphere at 1100 ° C. or less. The addition of Al reduces the firing temperature and facilitates control of the oxygen partial pressure during firing. Therefore, when the composition of the present invention is used for a multilayer capacitor element using a base metal material such as Cu as an internal electrode, the element can be manufactured under more stable manufacturing conditions without impairing the electrical characteristics, and mass productivity is improved. To do.

[Brief description of drawings]

FIG. 1 is a triangular composition diagram showing the component composition of a porcelain composition according to the present invention, FIG. 2 is a cross-sectional view of a magnesia container in which porcelain is put in during firing, and FIG. 3 is a cross-sectional view of a core tube during firing. 1 ... Magnesia container, 2 ... Magnesia container lid, 3 ...
... Calcination powder, 4 ... Magnesia powder, 5 ... Sample, 6 ... Reactor tube, 7 ... Stabilized zirconia oxygen sensor.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Junichi Kato 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toshihiro Mihara 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 56) References JP-A-55-51758 (JP, A) JP-A-59-57953 (JP, A) JP-A-53-82000 (JP, A)

Claims (1)

[Claims] 1. A composition represented by Pba (Mg _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 ) zO _{2 + a} (where x + y + z = 1) and a is 0.985 ≦ a ≦ 1.110, and for each value of a within this range, Pba (Mg _1/3 Nb _2/3 ) O _{2 + a} , PbaTiO _{2 + a} , Pba (Ni _1/2 W _1/2 ) In the triangular coordinate system with O _{2 + a} as the apex, the following composition points A, B, C, D, E, A; x = 0.950 y ＝ 0.025 z ＝ 0.025 B; x ＝ 0.850 y ＝ 0.125 z ＝ 0.025 C; x = 0.100 y = 0.060 z = 0.300 D; x = 0.100 y = 0.400 z = 0.500 E; x = 0.900 y = 0.250 z = 0.75 For the composition within the pentagonal region, copper is added as a sub-component. Oxide is 0.03 to 0.65 in Cu ₂ O equivalent weight%.
% Dielectric ceramic composition.