JPS6317254A - 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 fired at 1100° C. or lower, particularly 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, there are lead composite perovskite materials that can be fired in air at temperatures below 1000°C and inexpensive Ag-based materials used as internal electrodes, and base metal materials such as Ni that can be fired in low oxygen partial pressure atmospheres. Barium titanate-based materials have been developed that can be used as internal electrodes. Regarding the former, JP-A-58-176175 describes Pb(Ni!
z+ Nb*z+ )OF3- PbTiQ 3- P
A dielectric ceramic composition containing b(Mg1z2Wl/2)03 is described. Regarding the latter, the Special Public Interest Publication of 1984-1984
Materials such as those described in Japanese Patent No. 641 are known.

Pb (Ni1zs Nb2z3)03-PbTiO3
-Pb(Mg/2Wl/2)Os-based solid solution can be fired at low temperatures and has a higher dielectric constant than barium titanate-based materials, which have a similar rate of change in dielectric constant with temperature. Therefore, a multilayer capacitor made of this dielectric ceramic composition and an Ag-based internal electrode has the advantage of allowing the device to have a large capacity, be small in size, and be low in cost. However, in recent years, there has been a demand for the use of base metals such as Cu as internal electrodes, which can further reduce the cost of internal electrode materials.For this reason, it is necessary to create an atmosphere with a low oxygen partial pressure in which metals such as Cu do not oxidize when co-fired. There is a need for materials that can be fired at high temperatures and have high resistivities.

Problem to be solved by the invention Pb (Nil/3 Nbυ3 )03- PbTi
03-Pb(Mg1t*Wl/2)03-based solid solution does not sinter densely when fired in a low oxygen partial pressure atmosphere and tends to have a low resistivity.

The present invention provides Pb (Ni1zs Nbzz+)03-
PbTi0CI-Pb (Mg1/* w,,, )
The object of the present invention is to provide a dielectric ceramic composition that has a high resistance value when fired in a low oxygen partial pressure atmosphere without impairing the high dielectric constant and low-temperature sintering properties of the Os system.

Means to solve the problemPba(Nixzs Nb2.s)xTiy(Mg1
z2Wl/2) In the composition formula represented by Z02+a (however, x+y+z=1), 1.001≦a≦1.1
10, and for each value of a within this range, Pb, (N15z3Nb2zs) 02+a,
P b@T i O2+a % and Pba (Mg
s/2Wl/2) In the triangular coordinates with 02+1 as the vertex, the following composition point A.

Let the composition be within a rectangular region with B, C, and D as vertices.

A: x=o, 700 y=0.27F+z
=0.025B; x=o, 500 y=0.47
5z=0.025C;x=0.100y=0.450z
=0.450D; x=0.100y=0.300z
= 0.600 Effect In the composition of the present invention, by increasing the A-site component in excess, a dense fired product can be obtained in a low oxygen partial pressure atmosphere at 1100°C or less, and a highly reliable product with high resistivity can be obtained. Elements can be changed.

Example Starting materials include chemically highly pure PbO and Nip.

MgO, Nb2O5, TiO2, and WO3 were used.

After correcting the purity of these, weigh the specified amount,
Wet mixing was carried out for 17 hours in a ball mill using agate boulders and pure water as a solvent. This was filtered with suction to remove most of the water, then dried, and then thoroughly crushed in a Raikai machine, after which 5 wt% of water was added to the mass of the material.
It was molded into a cylindrical shape with a molding pressure of 500 kg/cm2. Place this in an aluminum pot and cover with the same material, 7
Calcining was performed at 50°C to 880°C for 2 hours. Next, the calcined product was roughly crushed in an alumina mortar, and further crushed in a ball mill using agate 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 in an amount of 6 wt %, and 32
Granulate through mesh sieve and press at 1000kg
/cm2, and was molded into a cylindrical shape with a diameter of 13m+n and a height of about 5mn1. 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 200 meshes of ZrO2 powder was spread to a thickness of about 1 mm, covered with a homogeneous lid, and inserted into the core tube of a tubular electric furnace. After degassing the inside of the reactor core tube with a rotary pump, it was replaced with N2-82 mixed gas, and the oxygen partial pressure (PO2
) is 1. N2 and H2 to make Ox 10-”atm
Flow the mixed gas while adjusting the gas mixture ratio, raise the temperature to the specified temperature at 400℃/hr, hold it for 2 hours, and then increase the temperature to 400℃/hr.
The temperature decreased in hr. Po2 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 at the bottom of magnesia container 1, and zirconia 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 disk shape with a thickness of 1 thick, and Cr-Au was coated on both sides.
, and the dielectric constant, tan δ, is 1 kll z .

Measurements were made under an electric field of 1v/lWI. Also, the resistivity is 1k
The voltage of V/m+n was determined from the value 1 minute after application.

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 peripheral composition components (a, x
, y, z are Pb3 (Ni1z+ Nbzz+ )X T
iy (value expressed as Mg1t2Wl/2)Z 02□), firing temperature when firing in a low oxygen partial pressure atmosphere,
Dielectric constant, temperature change rate of dielectric constant (relative to 20°C), ta
nδ, resistivity, and density are shown.

, FIG. 1 shows the samples shown in Table 1, P ba T i O
2+a, Pba (Nirls Nbs+/s) Oz
+a N and Pl:h(Mgl/2Wl/2)02+
This is shown in a triangular composition diagram with a as an end member, and the shaded area is the scope of the invention.

(Left below) For compositions outside the scope of the invention, if a is smaller than 1.001, a dense sintered product cannot be obtained when fired in a low oxygen partial pressure atmosphere, or the resistivity may be low. 1
．． When the value exceeds 110, the dielectric constant and resistivity decrease. In addition, for compositions in which x, y, and z are outside the specified ranges, the Curie point will deviate significantly from room temperature and the dielectric constant will be low (
However, the temperature change rate of the dielectric constant becomes large. Both of the aforementioned problems are overcome in the claimed compositions.

Note that the low oxygen partial pressure atmosphere PO2 selected as the firing atmosphere
;1. OX 10-'at+++ is lower than the equilibrium oxygen partial pressure of the steel at the firing temperature (it is thought that the metal hardly oxidizes).

Effects of the Invention According to the present invention, a dense, high-resistivity 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, and a sintered body made of Cu or the like as an internal electrode can be obtained. An excellent dielectric ceramic composition that allows the use of base metal materials can be obtained.

[Brief explanation of drawings]

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. ■... Magnesia container, 2... Magnesia container lid, 3... Calcined powder, 4... Zirconia powder, 5...
- Sample, 6... Furnace tube, 7... Stabilized zirconia oxygen sensor. Name of agent: Patent attorney Toshio Nakao and one other person Figure 1

Claims (1)

[Claims] Pb_a(Ni_1_/_3Nb_2_/_3)_xT
i_y(Mg_1_/_2W_1_/_2)_zO_2
Compositional formula represented by ___+_a (x+y+z=1)
is in the range of 1.001≦a≦1.110,
For each value of a within this range, Pb_a(Ni_1_/_3Nb_2_/_3)O_2
_+_a, Pb_aTiO_2_+_a and Pb_a(Mg_1_/_2W_1_/_2)O_2_
In the triangular coordinates with +_a as the vertex, the following composition point A,
A dielectric ceramic composition comprising a composition within a rectangular region with vertices B, C, and D. A; x=0.700 y=0.275 z=0.025
B; x=0.500 y=0.475 z=0.025
C; x=0.100 y=0.450 z=0.450
D; x=0.100 y=0.300 z=0.600