JPH0821263B2 - Dielectric porcelain composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high-dielectric-constant dielectric ceramic composition that is fired at 1080 ° C. or lower, and in particular, a composition that can be fired in a low oxygen partial pressure atmosphere to obtain high resistivity. Regarding

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 already reduced the oxygen partial pressure below 1080 ° C.
Such as copper or copper-based alloys that can be fired in an atmosphere
Inexpensive base metal materials can be used as internal electrodes, (Pb_a 
Me_b) (Mg_1/3Nb_2/3) XTiy O 2 + a + b (Me is Ca, Ba, S
A dielectric porcelain composition represented by r) is proposed. this
The composition can be fired at low temperature and fired under low oxygen partial pressure
In this case, copper or an alloy containing copper as a main component has a high resistivity.
Can be used for a multilayer capacitor element with
Wear.

On the other hand, in the above-mentioned manufacturing process of the ceramic multilayer capacitor element, the internal electrode such as copper or an alloy containing copper as a main component is not oxidized during firing and the dielectric ceramic is not reduced to reduce the 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 for obtaining the optimum conditions.
Therefore, there has been a demand for a composition which can be fired at a lower temperature and has a high resistivity for the dielectric ceramic.

Problems to be Solved by the Invention (Pb _a Me _b ) (Mg _1/3 Nb _2/3 ) xTiy O ₂ + a + b (Me is C
In the dielectric ceramic composition represented by a, Ba, Sr), the object is to provide a dielectric ceramic composition having a lower firing temperature and a higher resistivity without impairing the dielectric properties.

Means for solving problems (Pb _a Me _b ) (Mg _1/3 Nb _2/3 ) xTiy O ₂₊ a + b (Me is Ca,
Ba, Sr) dielectric ceramic composition (provided that x + y =
In contrast to 1), copper oxide is added as a sub-component in the range of 0.03 to Cu ₂ O equivalent.
The composition contains 0.65% by weight.

In the system of the dielectric porcelain composition of the present invention, the composition containing the accessory component with respect to the composition containing no accessory component 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 As a starting material, chemically high-purity PbO, MgO, Nb ₂ O ₅ ,
TiO ₂ , CaCO ₃ , BaCO ₃ , SrCO 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 remove most of the water content, then dried and then charged and decomposed with a Lykai machine.
Add water to form a cylinder with a diameter of 60 mm and a height of about 50 mm.
It was molded at 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 is roughly crushed in an alumina mortar, and further crushed in a ball mill for 17 hours using pure water as a solvent using zirconia boulders,
This was suction filtered to separate most of the water content and then dried. 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, molding pressure 1000 kg
Molded at / cm ² . Molded product is heated up to 700 ℃ in air 1
Hold the time and burn out the polyvinyl alcohol.
Place the above calcined powder on top of about 1/3 of the volume and put 200
Move the mesh MgO powder to a magnesia porcelain container laid with 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 core tube with a rotary pump, N ₂ -H ₂ -H ₂ O
Oxygen partial pressure (Po ₂ ) at the firing temperature is 1.0 by replacing with mixed gas.
The mixed gas was flowed while adjusting the mixing ratio of N ₂ and H ₂ gas to be x10 ⁻⁸ atm, 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. 1 shows the structure of the magnesium porcelain container at the time of firing, and FIG. 2 shows the inside of the core tube in a sectional view.

In FIG. 1, 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 at the bottom of the magnesia container 1, and a magnesia powder 4 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 with a thickness of 1 mm, Cr-Au was vapor-deposited on both sides, 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,
b, x, y, are (Pb _a Me _b ) (Mg _1/3 Nb _2/3 ) xTiy O ₂₊ a + b values) Firing temperature, dielectric constant, dielectric constant when firing in a low oxygen partial pressure atmosphere The temperature change rate (at 20 ° C), tan δ, resistivity, and density were shown.

In the composition outside the scope of the invention, when a + b is less than 1.010, the firing temperature is 1080 even if copper oxide is added as a subcomponent.
When copper oxide is added until the temperature becomes higher than ℃ or the firing temperature becomes lower than 1080 ℃, the dielectric constant decreases, or the resistivity decreases, and when it exceeds 1.50, the dielectric constant and the resistivity decrease. Has the drawback of diminishing. 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 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 Po ₂ selected as the firing atmosphere;
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 is hardly oxidized.

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 at a low oxygen partial pressure atmosphere of 1080 ° C. or less. The addition of the components lowers 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 cross-sectional view of a magnesia container in which porcelain is placed during firing, and FIG. 2 is a cross-sectional view of the inside of a furnace 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.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Junichi Kato 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Toshihiro Mihara, 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. 56) References JP-A-62-96357 (JP, A) JP-A-55-121959 (JP, A) JP-A-56-2690 (JP, A)

Claims (1)

[Claims] 1. A compound represented by (Pba Meb) (Mg _1/3 Nb _2/3 ) xTiyO _{2 + a + b} , wherein Me is at least one element selected from the group consisting of Ca, Ba and Sr, x + y = 1.00 0.001 ≤ b ≤ 0.225 1.010 ≤ a + b ≤ 1.250 0.650 ≤ x ≤ 0.960 For the composition within the range of copper oxide as a sub-component, it is 0.03% by weight of the sub-components in terms of Cu ₂ O. A dielectric porcelain composition characterized by containing ~ 0.65%.