JPH0821261B2 - Dielectric porcelain composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high dielectric constant type dielectric ceramic composition which is fired in a low oxygen partial pressure atmosphere of 1100 ° C. or less, and particularly, a composition which has a low firing temperature and a 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
It is usually manufactured by a process of integrally firing the internal electrode and the ceramic. 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. Had to use.

On the other hand, the inventors can use a base metal material containing copper as a main component that can be fired at 1100 ° C. or less in a low oxygen partial pressure atmosphere as an internal electrode (PbaMeb) {(Mg _1/3 Nb _2/3 ) xTiy ( Ni _1/2 W _1/2 )
A composition represented by z} O ₂ + a + b, in which Me is Ca, Sr, or Ba, is proposed. This composition can be fired at low temperatures,
It is an excellent dielectric porcelain composition which has a characteristic of having a high resistivity when fired under a low oxygen partial pressure and can be used for a multilayer capacitor element having copper or an internal electrode containing copper as a main component.

Problems to be Solved by the Invention On the other hand, in the above-mentioned manufacturing process of the ceramic multilayer capacitor element, the internal electrode copper or the alloy containing copper as a main component is not oxidized during firing, and the dielectric ceramic is reduced. Firing under oxygen partial pressure that does not reduce resistance 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.

The present invention provides (PbaMeb) {(Mg _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 ) z}.
A dielectric ceramic composition composed mainly of a composition represented by O ₂ + a + b, in which Me is at least one selected from the group consisting of Ca, Sr, and Ba, does not impair the dielectric properties, lowers the firing temperature, and reduces the resistance. An object of the present invention is to provide a dielectric porcelain composition capable of obtaining a dielectric ceramic having a high index.

Means for solving problems (PbaMeb) {(Mg _1/3 Nb _2/3 ) xTiz (Ni _1/2 W _1/2 )} O ₂ + a + b
In the composition consisting of at least one component of the group consisting of Ca, Sr, and Ba, copper oxide is added as a sub-component to Cu.
_The composition contains 0.03 to 0.65% by weight in terms of ₂ O.

Effect In the system of the dielectric ceramic composition of the present invention, the composition containing the additive is sintered at a low firing temperature with respect to the composition containing no additive, the dielectric constant is less decreased, and the increase of the dielectric loss is also small. And, the resistivity is the same or improved.

Example As a starting material, chemically pure PbO, MgO, MeCO ₃ (Me: Ca, S
r, Ba), Nb ₂ O ₅ , TiO ₂ , NiO, 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 and then lysed and crushed with a Lykai machine, and then the powder amount is 5w.
A water content of t% was added, and a column having a diameter of 60 mm and a height of about 50 mm was formed at a forming pressure of 500 kg / cm ² . This was placed in an alumina crucible, covered with the same material, and calcined at 680 ° 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, crushing and drying several times, a 6 wt% aqueous solution of polyvinyl alcohol was added to
wt% was added, 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 600 ° C. in the air and kept for 4 hours to burn out the polyvinyl alcohol content. This is transferred to a magnesia porcelain container laid with about 1 mm of 200 mesh MgO powder on the above calcined powder spread about 1/3 of the volume, covered with the same quality, and inserted into the core tube of the tubular electric furnace, After degassing the inside of the core tube with a rotary pump,
Replaced with N ₂ -H ₂ -H ₂ O gas and oxygen partial pressure (Po ₂ ) is 1.0x10 ^-8 atm
The mixed gas is flowed while adjusting the mixing ratio of N ₂ and H ₂ gas so that the temperature becomes 400 ° C./hr and the temperature is maintained for 2 hours.
The temperature was lowered at 0 ° C / hr. Po ₂ in the core tube was measured by the inserted stabilized zirconia oxygen sensor.

Figure 2 shows the structure of the magnesium porcelain container during firing.
In the figure, the inside of the core tube is shown in cross section. 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 arranged at the bottom of the magnesia container 1, and the magnesia powder 4 was arranged 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 that the components [a, b, x, y, z of the composition range and peripheral composition of the present invention are (PbaMeb) (Mg _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 )
zO ₂ + a + b], the firing temperature when firing in a low oxygen partial pressure atmosphere, the dielectric constant, tan δ, and the resistivity.

FIG. 1 shows the main composition of the present invention as (PbaMeb) TiO ₂ + a + b; (Pba
Meb) (Mg _1/3 Nb _2/3 ) O ₂ + a + b; and (PbaMeb) (Ni
_{It is} shown in the triangular composition diagram with _1/2 W _1/2 ) O ₂ + a + b as the end component, and the range of the shaded area is the range of the main composition.

In the compositions outside the scope of the invention, if the auxiliary component is less than 0.03 wt%, the effect of improving the sintering temperature lowering does not appear, and if it exceeds 0.65 wt%, the dielectric properties, particularly the dielectric constant and the resistivity decrease largely. Compositions within the scope of the invention overcome all of the above problems. The range of the main component is limited by the denseness, resistivity, dielectric constant, and temperature change rate of the dielectric constant of the fired product when fired in a low oxygen partial pressure atmosphere.

The low oxygen partial pressure atmosphere Po ₂ selected as the firing atmosphere;
1.0x10 ^-8 atm is the oxygen partial pressure at which the copper is hardly oxidized at the firing temperature and the resistance reduction due to the reduction of the dielectric ceramic does not occur. It satisfies the manufacturing conditions.

EFFECTS OF THE INVENTION According to the present invention, a dielectric ceramic having a high dielectric constant, a dense and high resistivity, can be obtained by firing at a low oxygen partial pressure atmosphere of 1100 ° C. or lower
In particular, the additive of the present invention lowers the firing temperature and facilitates optimum oxygen partial pressure control during firing. Therefore, when the composition of the present invention is used for the dielectric of the multilayer capacitor element using Cu as the internal electrode, the element can be manufactured under more stable manufacturing conditions without impairing the electrical characteristics, and the mass productivity is improved. .

[Brief description of drawings]

FIG. 1 is a triangular composition diagram showing the main component composition of the dielectric 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. 3 is a sectional view of a core tube during firing. Indicates. 1 ... Magnesia container, 2 ... Magnesia container lid, 3 ...
... Calcination powder, 4 ... Magnesia powder, 5 ... Sample, 6 ... Magnesium container, 7 ... Reactor tube, 8 ... 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 55-121959 (JP, A) JP 55-158685 (JP, A) JP 60-49504 (JP, A) JP 53-82000 (JP, A)

Claims (1)

[Claims] 1. A (PbaMeb) {(Mg _1/3 Nb _2/3 ) xTiy (Ni _1/2 W _1/2 ) z}
It has a composition represented by O ₂ + a + b (where x + y + z
= 1), Me is at least one selected from the group consisting of Ca, Sr, Ba, and is in the range of 0.001 ≤ b ≤ 0.250 1.001 ≤ a + b ≤ 1.200, and for each value of a and b within this range , (PbaMeb) (Mg _1/3 Nb _2/3 ) O ₂ + a + b; (PbaMeb) TiO ₂ + a + b; and (PbaMeb) (Ni _1/2 W _1/2 ) O ₂ + a + b in the triangular coordinates below. Composition point A, B, C, D, E, A; x = 0.950 y = 0.49 z = 0.001 B; x = 0.750 y = 0.249 z = 0.001 C; x = 0.010 y = 0.800 z = 0.190 D; x = 0.010 0.03 to 0.65% by weight% of Cu ₂ O equivalent copper oxide as a secondary component to the composition in the rectangular region with y = 0.450 z = 0.540 as the apex.
A dielectric porcelain composition comprising: