JPS63239708A - Dielectric ceramic composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 1100°C or lower, and in particular a composition that can be fired in a low oxygen partial pressure atmosphere and has a high resistivity. relating to things.

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.

On the other hand, the inventors proposed that
Pba <Mgxt3Nb2t2)x, which can be fired as follows and can be used as an internal electrode using a base metal material mainly composed of copper
Tiy (Nis/2W1/2)O2 )Z O2+
A dielectric ceramic composition represented by a is proposed. This composition can be fired at low temperatures and has high resistivity when fired under low oxygen partial pressure, making it an excellent material that can be used in multilayer capacitor elements with internal electrodes mainly made of steel or copper. It is a dielectric ceramic composition. On the other hand, in the manufacturing process of the ceramic multilayer capacitor elements mentioned above, during firing, the internal electrodes, which are alloys mainly composed of copper or steel, are not oxidized and the dielectric ceramic is reduced and the resistance is not lowered under oxygen partial pressure. firing 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 dielectric ceramic compositions that can be fired at lower temperatures and have high resistivity.

Problem to be solved by the invention Pb2(MgIts Nb2t3)X Tiy (Ni
1z2W1/2)O2)Z02+a In a dielectric ceramic composition whose main component is a composition represented by Z02+a, it is an object of the present invention to provide a dielectric ceramic composition with high resistivity by lowering the firing temperature without impairing the dielectric properties. The purpose is

Means for solving the problem Pba (Mgtzs Nb5zs ) x Tiy (N
i1z2W1/2)O2)ZO2+a (where x+y+z=1) is a composition containing 0.03 to 0.65% by weight of copper oxide as a subcomponent in terms of Cu2O.

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, the dielectric constant decreases less, the dielectric loss increases less,
And the resistivity is the same or improved.

Example The starting materials are chemically highly pure PbO and MgO.

Nb2O5, TiO2, NiO, WOs, CIJ20
was 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 was filtered by suction to separate most of the water, then dried, and then thoroughly crushed in a Raikai machine, after which 5 wt% of water was added to the powder amount, and the diameter was 60 m.
Molding pressure 500kg/cm to form a cylinder with a height of about 50mm
It was molded with 2. This was placed in an aluminum crucible, covered with a homogeneous lid, 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 in a ball mill using zirconia cobblestones and pure water as a solvent for 17 hours, filtered under suction to remove most of the moisture, and then dried. After repeating the above calcining, crushing, and drying several times, a 6 wt% aqueous solution of polyvinyl alcohol was added to the powder to make 6 wt% of the powder.
wt% was added, granulated through a 32 mesh sieve, and molded at a molding pressure of 1000 kg/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 about 173 of the volume of the calcined powder was spread, and about 1 mm of 200 mesh MgO powder was spread over it, covered with a homogeneous lid, and inserted into the core tube of a tubular electric furnace. After degassing with a rotary pump, it was replaced with a N2H2-H20 mixed gas, and the oxygen partial pressure (PO2) at the firing temperature was 1.
While adjusting the mixture ratio of N2 and H2 gas to obtain oxlo-8 atm, the mixed gas was flowed at 400℃/ to the specified temperature.
The temperature was raised at 400°C/hr, held for 2 hours, and then lowered at 400°C/hr. PO9 in the reactor core tube was measured by an inserted stabilized zirconia oxygen sensor. FIG. 2 shows the structure of the Magnesia porcelain container during firing, and FIG. 3 shows a cross-sectional view of the inside of the furnace tube.

In FIG. 2, 1 is a magnesia container, the upper part of which is sealed with a magnesia container lid 2. Calcined powder 3 was placed in the lower part of magnesia container 1, and magnesia powder 24 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 plates with a thickness of III+, and both sides were coated with C.
r-Au was deposited, and the dielectric constant, tan δ, was 1 ktlz, 1
Measurements were made under an electric field of v/m1. Further, the resistivity was determined from the value 1 minute after applying a voltage of 1 kV/voltage.

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

Table 1 shows the composition range of the present invention and the peripheral composition components (a,
x, 7+ Z is P b (Mgxts Nbzz3)
XTiy (value expressed as Nitz*Wst2>zo*average), firing temperature when fired in a low oxygen partial pressure atmosphere, dielectric constant, temperature change rate of dielectric constant (relative to 20°C), t
anδ, resistivity, and density are shown.

Figure 1 shows each sample shown in Table 1 as P b@T i O
2+@Pba (Mgx/s Nbqt3)02 +a
Pb*・(N i 1/2W1/2)O2)
This is shown in a triangular composition diagram with 02 +a as the end member, and the shaded area is the scope of the invention.

In a composition outside the scope of the invention, if a is smaller than 0.985, the firing temperature will be 1100°C even if copper oxide is added as a subcomponent.
If steel oxide is added until the firing temperature is higher than 1100℃ or lower than 1100℃, the dielectric constant or resistivity will decrease. It has the disadvantage of decreasing.

If the amount of steel oxide as a subcomponent is less than 0.03 wt$, the improvement effect of lowering the firing temperature will not appear, and if it is more than 0.65 wt$, the dielectric properties and dielectric constant and resistivity will decrease significantly. Compositions in which y and z are outside the specified ranges have the disadvantage that the Curie point greatly deviates from room temperature and the dielectric constant becomes low (or the rate of change in dielectric constant with temperature increases). The composition overcomes both of the above problems.

Note that the low oxygen partial pressure atmosphere PO2 selected as the firing atmosphere
;1. It is considered that OxlO-eatw is lower than the equilibrium oxygen partial pressure of copper at the firing temperature, and 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 1100° C. or lower in a low oxygen partial pressure atmosphere. By adding , the firing temperature is lowered and the oxygen partial pressure during firing can be easily controlled. Therefore, when the composition of the present invention is used in a multilayer capacitor element using a base metal material such as Cu as the internal electrode, the element can be manufactured under more stable manufacturing conditions without impairing the electrical characteristics, and mass production is improved. improves.

[Brief explanation of the drawing]

FIG. 1 is a triangular composition diagram showing the component composition of the porcelain composition according to the present invention, FIG. 2 is a cross-sectional view of a magnesia container in which the porcelain is placed during firing, and FIG. 3 is a cross-sectional view of the inside of the furnace tube during firing. l...Magnesha container, 2...Magnesha 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 and one other person Figure 1 Pbn (Ni+/xW+/2)Ox+a z
PbaTi02+sFigure 1Figure 3

Claims (1)

[Claims] Pb_a(Mg_1_/_3Nb_2_/_3)_x
Ti_y(Ni_1_/_2W_1_/_2)_zO_
It has a composition represented by 2_+_a (where x+y+z=
1), a is in the range 0.985≦a≦1.110, and for each value of a within this range, Pb_a
(Mg_1_/_3Nb_2_/_3)O_2_+_a
, Pb_aTiO_2_+_a, Pb_a(Ni_1_
/_2W_1_/_2) In the triangular coordinates with O_2_+_a as the vertex, the following composition points A, B, C, D, E, A; x = 0.950y = 0.025z = 0.025B;
x=0.850y=0.125z=0.025C;x=
0.100y=0.060z=0.300D;x=0.
100y=0.400z=0.500E;x=0.90
For the composition within the pentagonal region with 0y = 0.025z = 0.075 as the apex, it is assumed that copper oxide is contained as a subcomponent in an amount of 0.03 to 0.65% by weight in terms of Cu_2O. Characteristic dielectric porcelain composition.