JPS63239709A - 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 porcelain composition fired at 1100° C. or lower in a low oxygen partial pressure atmosphere, and particularly to a composition that can obtain high resistivity at a low firing temperature. 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. Traditionally, barium titanate-based materials have been used for high-permittivity ceramic capacitor materials, but because the firing temperature is as high as 1,300°C, expensive metals such as Pt and Pd have been used as internal electrode materials. It was necessary to use it.

On the other hand, the inventors proposed that
Base metal materials containing steel as the main component can be used as internal electrodes (Pb a Me b) (<Mgxt
3Nbqt3) x Ti y (Ni1z2Wl/2
) ZIQ2+a+b, Me is Ca, S
The present invention proposes a composition consisting of R, and also Ba. 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.

Problems to be Solved by the Invention On the other hand, in the manufacturing process of the ceramic multilayer capacitor element mentioned above, during firing, the copper or copper-based alloy that is the internal electrode does not oxidize, and the dielectric ceramic is reduced. Firing is required under an oxygen partial pressure that does not lower the resistance. 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.

Therefore, for dielectric ceramics, there has been a demand for a composition that can be fired at a lower temperature and has a high resistivity.

The present invention provides (Pb a Me b) l(Mg1/3N
b2z3)xTi y (Ni1z2Wl/2)
zlo2"a"b, where Me is Ca, Sr, Ba
A dielectric ceramic selected from the group consisting of a dielectric ceramic composition whose main component is a dielectric ceramic composition that can be fired at a lower firing temperature without impairing the dielectric properties and yielding a dielectric ceramic with high resistivity. The purpose is to provide a porcelain composition.

Means to solve the problem (Pb * Me b ) <Mg5ts Nbs+
zs) x Ti z(N1xt2Wl/2)02
It is represented by +a+b, and Me is Ca.

A composition containing at least one component of the group consisting of Sr and Ba contains 0.03 to 0.65% by weight of steel oxide as a subcomponent in terms of Cu2O.

Effect: In the dielectric ceramic composition system of the present invention, the composition containing additives is sintered at a lower firing temperature than the composition containing no additives, and the decrease in dielectric constant is small and the increase in dielectric loss is small. , and the resistivity is the same or improved.

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

MeCOs (Me:Ca, Sr, Ba)*Nb
2O5°TiO2, Nip, WC)a, 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, dried, and then thoroughly crushed using a Raikai machine. After adding 5wt% of moisture to the powder, it is molded into a cylindrical shape with a diameter of 60M and a height of about 50m at a pressure of 500kg/ It was molded with c1. This was placed in an alumina 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 for 17 hours in a ball mill using zirconia cobblestones and pure water as a solvent.The resulting mixture was filtered under suction to remove most of the moisture, and then dried. After repeating the above steps of calcination, crushing, and drying several times, a 6 wt% aqueous solution of polyvinyl alcohol was added to the powder in an amount equal to 6 wt%.
wt% was added, granulated through a 32 mesh sieve, and molded at a molding pressure of 1000 kg/co+z. The molded product was heated to 600°C in air and held for 4 hours to burn out the polyvinyl alcohol content. This was transferred to a Magnesia porcelain container in which about 1/3 of the volume of the calcined powder was spread, and about 1 m+a of 200 mesh MgO powder was spread, covered with a homogeneous lid, and inserted into the core tube of a tubular electric furnace. After deaerating the inside of the reactor core tube with a rotary pump, it was replaced with N2-N2-N20 gas until the oxygen partial pressure (PO2) was 1. oxlO-8a
A mixed gas was flowed while adjusting the mixing ratio of N2 and N2 gas so that the temperature became tm, the temperature was raised to a predetermined temperature at a rate of 400°C/hr, and after being held for 2 hours, the temperature was lowered at a rate of 400°C/hr. P in the core tube
o2 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 magnesia powder 4 was placed above 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 m, Cr-Au was evaporated on both sides, and the dielectric constant and tan δ were set to 1 kHz and IV/rt.
Measurements were made under an electric field of m. Further, the resistivity was determined from the value 1 minute after applying a voltage of 1 kV/lW+.

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 the surrounding composition components [a
, b, x, y, z are (Pb-Meb) (Mgszs
Nb+;i/3) x Ti y (N15zs+
Value J1 when expressed as Wl/2)z02+Q+l) shows the firing temperature, dielectric constant, tan δ, and resistivity when fired in a low oxygen partial pressure atmosphere.

Figure 1 shows the main composition of the present invention as (Pb a Me b) T
iO2+a+b; (Pb a Me
b) (Mgt/+Nb2/3)02”+b
; and (Pb a Me b) (Nit/2W12
)02+a+b is shown in a triangular composition diagram with end members, and the diagonally shaded range is the main composition range.

In a composition outside the scope of the invention, if the subcomponents are smaller than 0.03wt%, the improvement effect of lowering the sintering temperature will not appear;
t%, the dielectric properties and dielectric constant and resistivity decrease significantly. Compositions within the scope of the invention overcome both of the aforementioned problems. The compactness and resistivity of the fired product when fired in an atmosphere,
It is limited by the dielectric constant and the temperature change rate of the dielectric constant.

Note that the low oxygen partial pressure atmosphere PO2 selected as the firing atmosphere
: 1.0x 10-"atm is an oxygen partial pressure at which the steel is hardly oxidized at the firing temperature and the resistance does not decrease due to reduction of the dielectric ceramic, and it is the oxygen partial pressure that does not cause any reduction in resistance due to reduction of the dielectric ceramic. This satisfies the manufacturing conditions for @ layer capacitors including:

Effects of the Invention According to the present invention, dielectric porcelain with high dielectric constant, high density, and high resistivity can be obtained by firing at 1100°C or lower in a low oxygen partial pressure atmosphere, and (by using the additives of the present invention, the firing temperature can be reduced. is reduced, making it easier to control the optimum oxygen partial pressure during firing.For this reason, when the composition of the present invention is used as the dielectric of a multilayer capacitor element using Cu as the internal electrode, the electrical properties will not be impaired (
, devices can be manufactured under more stable manufacturing conditions, improving mass productivity.

[Brief explanation of the drawing]

Fig. 1 is a triangular composition diagram showing the product composition of the dielectric porcelain composition according to the present invention, Fig. 2 is a cross-sectional view of the magnesia container in which the porcelain is placed during firing, and Fig. 3 is a cross-sectional view of the furnace tube during firing. shows. 1...Magnesha container, 2...Magnesha container lid, 3...Calcined powder, 4...
... Magnesia powder, 5 ... Sample, 6 ...
・Magnesha container, 7...Furnace tube, 8...
...Stabilized zirconia oxygen sensor.・Name of 1 agent: Patent attorney Toshio Nakao and 1 other person (P
baMeb) (Mg+zJlt)2/5)Q2+a+b
80 Go 40
20(PbaMebXNil/2WI/2)0
2+a+b” (PbaMeb)Ti
02+s+b Figure 1

Claims (1)

[Claims] (Pb_aMe_b) {(Mg_1_/_3Nb_2
___/_3)_xTi_y(Ni_1_/_2W_1_/
_2)_z}O_2_+_a_+_b (however, x+y+z=1), Me is Ca, Sr,
is at least one selected from the group consisting of 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, ( P
b_aMe_b)(Mg_1_/_3Nb_2_/_3
)O_2_+_a_+_b; (Pb_aMe_b)Ti
O_2_+_a_+_b; and (Pb_aMe_b)
(Ni_1_/_2W_1_/_2)O_2_+_a_
In the triangular coordinates with +_b as the vertex, the following composition point, A,
B, C, D, E, A: x=0.950y=0.049z=0.001B;
x=0.750y=0.249z=0.001C;x=
0.010y=0.800z=0.190D;x=0.
010y=0.450z=0.540 as the apex of the composition, containing 0.03 to 0.65% by weight of copper oxide as a subcomponent in terms of Cu_2O. Characteristic dielectric ceramic composition.