JPS63297266A - Dielectric ceramic composition - Google Patents

Abstract

PURPOSE:To obtain a dielectric porcelain composition which can be fired in a low oxygen-partial pressure atmosphere and gives high resistivity by adding a prescribed amount of Cu oxide as minor component to the main composition consisting of Pb, alkaline earth metal, Ni, Nb, Ti and O in a specific proportion. CONSTITUTION:The subject dielectric porcelain composition is obtained by mixing a composition which is represented with the formula and satisfies the equations: x+y=1.00, 0.001<=b<=0.150, 1.000<=1+b<=1.120, 0.450<=x<=0.770 with Cu oxide, as a minor component, in an amount of 0.03-0.65wt.% calculated as Cu2. According to the present invention, a sintered product which is dense and high in resistivity for giving high reliability as a laminated condenser element is obtained by firing the composition at a temperature lower than 1,080 deg.C in a low oxygen-partial pressure atmosphere. Especially, the addition of the minor component lowers the firing temperature and facilitates the control of oxygen partial pressure in firing. Thus, when a base metal material such as Cu is used as an inner electrode in a laminated condenser element, the element can be produced without adverse effects on its electric properties under more stable manufacturing conditions and the massproductivity increases.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a high dielectric constant dielectric ceramic composition that is fired at 1080°C or lower, and particularly to a composition that can be fired in a low oxygen partial pressure atmosphere and has a high resistivity. Regarding.

BACKGROUND OF THE INVENTION In recent years, multilayer ceramic capacitors are rapidly becoming popular due to the demand for smaller elements and larger capacitance in ceramic capacitors. Multilayer ceramic capacitors are typically manufactured by a process of integrally firing internal electrodes and ceramics. Barium titanate-based materials have traditionally been used as high-permittivity ceramic capacitor materials, but
Since the firing temperature is as high as about 1300° C., it is necessary to use expensive metals such as Pt and Pd as internal electrode materials.

In contrast, the inventors have already discovered that it is possible to use inexpensive base metal materials such as copper or copper-based alloys as internal electrodes, which can be fired in a low oxygen partial pressure atmosphere at temperatures below 1080°C (P
ba Meb ) (Mg+/3Nb++z3)xTiy
We propose a dielectric ceramic composition represented by Oe+a+b (Me is Ca, Ba, Sr). This composition can be fired at low temperatures, has high resistivity when fired under low oxygen partial pressure, and can be used in multilayer capacitor elements with internal electrodes made of steel or an alloy mainly composed of copper.

On the other hand, in the manufacturing process of the ceramic multilayer capacitor element mentioned above, firing is performed under an oxygen partial pressure that does not oxidize the steel or copper-based alloy that is the internal electrode during firing and does not reduce the dielectric ceramic and reduce its resistance. is required. In controlling this oxygen partial pressure, the higher the firing temperature is, the more difficult it becomes to control the gas mixture ratio to obtain optimal conditions. For this reason, there has been a demand for a dielectric ceramic composition that can be fired at a lower temperature and has a high resistivity.

Problem to be solved by the invention (Pba Meb) (Mg+/3Nb2/3)xTi
The purpose of the present invention is to provide a dielectric ceramic composition represented by yO2+a+b (Me is Ca, Ba, Sr), which has high resistivity by lowering the firing temperature without impairing the dielectric properties.

Means to solve the problem (Pba Meb) (Mg+/3Nb2/5)XTi
V Og + m + b (Me is Ca, Ba, Sr) For a dielectric ceramic composition (where x + y = 1) expressed as
．． The composition contains 65% by weight.

Function: In the dielectric ceramic composition system of the present invention, the composition containing the subcomponent is sintered at a lower temperature than the composition containing no subcomponent, and the decrease in dielectric constant is small (and the increase in dielectric loss is also small). And the resistivity is the same or improved.

Example The starting material is chemically highly purified pbo.

Nip, Nb2O5, TiO2, CaCO3, BaCO
3°5rCOs and Cu2O were used. After correcting the purity of these, a predetermined amount was weighed and mixed in a ball mill for 17 hours using zirconia cobblestones and pure water as a solvent. This is filtered by suction to remove most of the moisture, then dried, and then thoroughly crushed in a Raikai machine, resulting in 5wt% of the powder amount.
of water was added thereto, and molded into a cylindrical shape with a diameter of 60 nm and a MR height of approximately 50 nm at a molding pressure of 500 kg/cm2. Place this in an aluminum crucible, cover with a similar lid, and heat at 680°C to 76°C.
It was calcined at 0°C for 2 hours. Next, the calcined product was roughly crushed in an alumina mortar, and further crushed in a ball mill using zirconia cobblestones and pure water as a solvent for 17 hours, filtered with suction to remove most of the moisture, and then dried. Calcining and crushing above.

After drying was repeated several times, a 6 wt % aqueous solution of polyvinyl alcohol was added to the powder in an amount of 6 wt %, and the mixture was granulated through a 32-mesh sieve at a compacting pressure of 1000 kg/kg.
It was molded in cm2. The molded product was heated to 700'C in air and held for 1 hour to burn out the polyvinyl alcohol content. This was transferred to a Magnesia porcelain container in which the above-mentioned calcined powder was spread to a volume of about 173 cm, and 200 mesh MgO powder was spread to a thickness of about 1+ nm, covered with a homogeneous lid, and inserted into the core tube of a tubular electric furnace. After degassing the inside of the furnace core tube with a rotary pump, it was replaced with N2-H2H20 mixed gas, and the oxygen partial pressure (PO2) at the firing temperature was 1.0 x 10-'
A mixed gas was flowed while adjusting the mixing ratio of N2 and H2 gas so that the mixture became atm, and the temperature was raised to a predetermined temperature at a rate of 400°C/hr. After being maintained for 2 hours, the temperature was lowered at a rate of 400°C/hr. Poa in the reactor core tube was measured by an inserted stabilized zirconia oxygen sensor. FIG. 1 shows the structure of the Magnesia porcelain container during firing, and FIG. 2 shows a cross-sectional view of the inside of the furnace tube.

In FIG. 1, 1 is a magnesia container, the upper part of which is sealed with a magnesia container lid 2. Calcined powder 3 was placed at the bottom of magnesia container 1, and magnesia powder 4 was placed on top of it. Further, sample 5 was placed on top of it.

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

The fired product was cut into a plate shape with a thickness of 1 orchid, Cr-Au was deposited on both sides, and the dielectric constant, tan δ, was set at 1 kHz, I V /
Measurements were made under an electric field of am. Also, the resistivity is 1kV/
The voltage of nun was determined from the value 1 minute after application.

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

Table 1 shows the composition range of the present invention and peripheral composition components, (a,
b, x, y, (PbaMeb) (Ni1/3Nb
2/3) Value of X Ti y Oa+a+b) Firing temperature, dielectric constant, temperature change rate of dielectric constant (relative to 20° C.), tan δ, resistivity, and density when fired in a low oxygen partial pressure atmosphere are shown.

(Left below) In a composition outside the scope of the invention, if a+b is less than 1.000, the firing temperature will be 10% even if copper oxide is added as a subcomponent.
The firing temperature is higher than 80℃ or lower than 1080℃ (
If copper oxide is added to a value of 1.120, the dielectric constant or resistivity will decrease, and if it exceeds 1.120, the dielectric constant and resistivity will decrease.

If the amount of copper oxide as a subcomponent is smaller than 0.03wt5, the improvement effect of lowering the firing temperature will not appear, and if it is larger than 0.65wt1, the dielectric properties, especially the dielectric constant and resistivity, will be significantly reduced. Further, compositions in which X is outside the specified range have the disadvantage that the Curie point deviates significantly from room temperature and the dielectric constant becomes low, or the rate of change of the dielectric constant with temperature increases. Both of the aforementioned problems are overcome in the claimed compositions.

The firing atmosphere was a low oxygen partial pressure atmosphere PO selected as the atmosphere.
2; 1. Ox 100-8at is lower than the equilibrium oxygen partial pressure of copper at the firing temperature (it is thought that the metal is hardly oxidized).

Effects of the Invention According to the present invention, a dense and highly resistive sintered body for obtaining high reliability as a multilayer capacitor element can be obtained by firing at 1080° C. or lower in a low oxygen partial pressure atmosphere. The addition of the components lowers the firing temperature, making it easier to control the oxygen partial pressure during firing.

For the second reason, when the composition of the present invention is used in 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 (the element can be manufactured under more stable manufacturing conditions, and mass production is easier. will improve.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a magnesia container into which porcelain is placed during firing, and FIG. 2 is a sectional view of the inside of the furnace tube during firing. ■... Magnesia container, 2... Magnesia container lid, 3... Calcined powder, 4... Magnesia powder, 5...
...Sample, 6.. Furnace tube, 7.. Stabilized zirconia oxygen sensor. Name of agent: Patent attorney Toshio Nakao One idiot Figure 2

Claims (1)

[Claims] (PbaMeb) (Ni_1_/_3Nb_2_/_3
)xTiyO_2_+_a_+_b, Me is C
It consists of at least one element selected from the group consisting of a, Ba, and Sr, x+y=1.00 0.001≦b≦0.150 1.000≦a+b≦1.120 0.450≦x≦0. For compositions within the range of
A dielectric ceramic composition characterized by containing 0.65%.