JPH0638321B2 - Dielectric porcelain composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high dielectric constant dielectric ceramic composition that is fired at 1100 ° C. or lower, 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 about 1300 ° C., expensive metals such as Pt and Pd are used as internal electrode materials. There was a need.

On the other hand, a lead perovskite material which can be fired at about 1000 ° C. in air and which can use an inexpensive Ag material as an internal electrode has been proposed. As a system similar to the present invention, JP-A-60-86072 is proposed. PbTiO described in the publication
_3- Pb (Ni _1/3 Nb _2/3 ) O _3- Pb (Ni _1/2 W _1/2 ) O
_A composition consisting of ₃ is known. This system has excellent properties with high dielectric constant and low firing temperature.

INVENTION AND SUMMARY Problems _{PbTiO 3 -Pb (Ni 1/3 Nb 2/3} ) O 3 -Pb (Ni 1/2 W
_{Since the} composition consisting of _1/2 ) O ₃ has an even cheaper internal electrode containing copper as a main component, when fired in a low oxygen partial pressure atmosphere, it does not densely sinter and the resistivity decreases. I had a problem. The present invention uses PbTiO ₃ -Pb (Ni _1/3 Nb
_2/3 ) O ₃ -Pb (Ni _1/2 W _1/2 ) O ₃ Dielectric material with high resistivity by lowering the firing temperature when firing under low oxygen partial pressure without impairing the high dielectric constant of the system The purpose is to provide a porcelain composition.

Means for Solving Problems For a porcelain composition represented by Pba (Ni _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 ) zO _{2 + a} (where x + y + z = 1),
Copper oxide as a secondary component is converted to Cu ₂ O in an amount of 0.03 to 0.6.
The composition contains 5% by weight.

In the system of the derivative porcelain composition of the present invention, the composition containing the accessory component with respect to the composition containing no accessory component, when fired under a low oxygen partial pressure, sinters at a low temperature and the decrease in the dielectric constant is small, The increase in dielectric loss is small, and the resistivity is the same or improved.

Example As a starting material, chemically pure PbO, NiO, and Nb were used.
₂ O ₅ , TiO ₂ , WO ₃ and Cu ₂ O were used. These were subjected to purity correction, then weighed a predetermined amount, and wet-mixed in a ball mill for 17 hours using zirconia cobblestone and pure water as a solvent. This is filtered through trading to remove most of the water content, then dried, and then lysed and crushed with a liquor machine to obtain a powder amount of 5
Moisture of wt% was added to form a column having a diameter of 60 mm and a height of about 50 mm at a forming pressure of 500 kg / cm ² . Put this in an alumina crucible and cover with the same material.
I calcined for an hour. Next, the calcined product was roughly crushed in an alumina mortar and further crushed in a ball mill for 17 hours using pure water as a solvent using zirconia cobblestone, and this was suction filtered to separate most of the water content, and then dried. After repeating the above-mentioned calcination, pulverization and drying several times, 6 wt% of a 6 wt% aqueous solution of polyvinyl alcohol 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 air and kept for 1 hour to burn out the polyvinyl alcohol content. Transfer this to a magnesia porcelain container in which about 1/3 of the volume of the above-mentioned calcined powder is spread, and 200 mesh MgO powder is spread about 1 mm, put a lid of the same quality, and insert it into the core tube of the tubular electric furnace. After degassing the inside of the tube with a rotary pump, it was replaced with a N ₂ —H ₂ —H ₂ O mixed gas, and the oxygen partial pressure (Po ₂ ) at the firing temperature was 1.0 × 1.
The mixed gas was allowed to flow while adjusting the mixing ratio of N ₂ and H ₂ gas so as to be 0 ⁻⁸ atm, the temperature was raised to 400 ° C./hr up to a predetermined temperature, and the temperature was kept at 400 ° C./hr for 2 hours. 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. The calcined powder 3 was placed in the lower part of the magnesia container 1, and the 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 determined 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 is _{Pb a (Ni 1/3 Nb 2/3)} xTiy (Ni 1/2 W
_1/2 ) zO _{2 + a} ) The firing temperature when firing in a low oxygen partial pressure atmosphere, the dielectric constant, the temperature change rate of the dielectric constant (with respect to 20 ° C.), tan δ, the resistivity, and the density are Indicated.

FIG. 1 shows Pb _a TiO _{2 + a} Pb _a (Ni
_{1/3 Nb 2/3) O 2 + a} -Pb a (Ni 1/2 W 1/2) O 2 + a
Is shown in the triangular composition diagram with the end component being, and the range of the diagonal line is the range of the invention.

In the composition outside the scope of the invention, when a is smaller than 0.985, the firing temperature is 1100 even if copper oxide is added as a subcomponent.
If copper oxide is added until the temperature becomes higher than ℃ or the firing temperature becomes lower than 1100 ℃, the dielectric constant or the resistivity decreases, and if it exceeds 1.110, the dielectric constant and the resistance decrease. There is a drawback that the rate decreases. If the amount of the copper oxide as an accessory component is less than 0.03 wt%, the effect of improving the firing temperature is not improved, and if it is more than 0.65 wt%, the dielectric properties, particularly the dielectric constant and the resistivity are significantly reduced. Further, a composition in which x, y, z is out of the limited range has a problem that the Curie point is largely deviated from room temperature and the dielectric constant is lowered, or the temperature change rate of the dielectric constant is large. Compositions within the scope of the claims overcome all of the above problems.

The low oxygen partial pressure atmosphere P selected as the firing atmosphere
o ₂ ; 1.0 × 10 ⁻⁸ atm is lower than the equilibrium oxygen partial pressure of copper at the firing temperature, and it is considered that the metal is hardly oxidized.

EFFECTS OF THE INVENTION According to the present invention, a dense and high-resistivity sintered body for obtaining high reliability as a multilayer capacitor element can be obtained by firing at a low oxygen partial pressure atmosphere of 1100 ° C. or less, and in particular, a subcomponent of the present invention. 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 sectional view of a magnesia container in which porcelain is put in during firing, and FIG. 1 …… Magnesia container, 2 …… Magnesia container lid, 3 ……
Calcined powder, 4 …… Magnesia powder, 5 …… Sample, 6 …… Core tube, 7 …… Stabilized zirconia oxygen sensor.

Front page continuation (72) Inventor Junichi Kato 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toshihiro Mihara, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) Reference Documents JP-A-60-86072 (JP, A) JP-A-62-12652 (JP, A)

Claims (1)

[Claims] 1. Pba (Ni _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2
) zO _{2 + a} (where x + y + z =
1), a is in the range of _{0.985 ≦ a ≦ 1.110, Pb a} (Ni 1/3 Nb 2/3 to the value of each a in this _{range) O 2 + a 'Pb a} TiO 2 + a, Pb _a (Ni _1/2 W _1/2 ) O _{2 + a} in the triangular coordinates with the apex as the following composition points A, B, C, DA; x = 0.850 y = 0.149 z = 0.001 B; x = 0.450 y = 0.549 z = 0.001 C; x = 0.001 y = 0.750 z = 0.249 D; x = 0.001 y = 0.400 z = 0.599 For the composition within the rectangular region, copper oxide was added as a sub-component to Cu. 0.03% by weight in terms of ₂ O
A dielectric porcelain composition characterized by containing ~ 0.65%.