JPS61248304A - Non-reducing 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 [Industrial Field of Application] The present invention relates to a ceramic capacitor, particularly an internal capacitor made of nickel.
The present invention relates to a non-reducible dielectric ceramic composition for a laminated ceramic capacitor having electrodes.

[Conventional technology]

Conventionally, a multilayer ceramic capacitor generally consists of laminating a plurality of sheets of dielectric material mainly composed of BaTiO3 with internal electrodes coated on the surface, and the internal electrodes of each sheet are alternately connected in parallel with a pair of external connection electrodes. It is formed by connecting the two to one another and sintering them into one piece. Such laminated ceramic capacitors have come to be used in a wide range of electronic circuits as electronic components have rapidly become smaller with the advancement of electronics in recent years.

However, this conventional dielectric material mainly composed of BaTiOx needs to be fired at a high temperature of 1250°C to 1350°C, and when this material is used as the dielectric of a laminated ceramic capacitor, the internal electrodes are Badgelum (melting point: 1555°C), an expensive precious metal that does not melt or oxidize at firing temperatures of Therefore, it had the disadvantage of high cost.

Therefore, although conventional multilayer ceramic capacitors have high capacitance efficiency, other excellent dielectric properties, and high reliability, their price has been a major obstacle to their progress.

Therefore, in order to eliminate the disadvantage of the high cost of the conventional multilayer ceramic capacitors, attempts have been made to use inexpensive base metals, such as nickel-P, as internal electrodes. However, when a base metal such as nickel is used as an internal electrode, when co-firing a dielectric material such as barium titanate (BaTiOs) and a base metal internal electrode, the conditions for sintering the base metal as a metal film without oxidation are insufficient. Ni
The equilibrium oxygen partial pressure of /NiO is approximately 3X at 1300℃
10 atm, the oxygen partial pressure must be lower than that, and in this case, a dielectric material made of barium titanate or a solid solution thereof will generally be reduced under the above oxygen partial pressure and will not lose its insulating properties. The drawback is that it is difficult to obtain practical dielectric properties for a multilayer ceramic capacitor.

On the other hand, barium titanate solid solutions (Ba, Ca,
Sr) is a basic oxide in TiO2 (
Ba, Oa, Sr)O is converted into T1, which is an acidic oxide.
A non-reducible dielectric ceramic composition in which a base metal such as nickel can be used as an internal electrode in excess of the stoichiometric ratio with respect to 0x)C has been proposed in Japanese Patent Publication No. 57-42588 and other publications.

This is because, in general, in an ABDj-type crystal, the A ion, which has a 1z coordination with respect to oxygen, which is larger than the B ion, has a stoichiometric relationship with respect to the B ion located at the center of the oxygen octahedral (progusskite) structure. It is known that when the ratio is in excess, the crystal lattice strongly attracts oxygen atoms and it is difficult to reduce them.The invention described in the above publication is based on this stoichiometric ratio deviation, It has improved reducibility.

However, the dielectric ceramic composition described in the above-mentioned publication had the disadvantage that the rate of change in dielectric constant with temperature was large and the dielectric properties deteriorated.

Further, as a high dielectric constant dielectric ceramic composition having a small rate of change in dielectric constant with temperature, there is a composition in which a bismuth compound such as bismuth stannate or bismuth zirconate is added to BaTiOs. This is because the maximum value of the dielectric constant near the Curie point of BaTi0z is lowered due to the strong de-deressor effect of the bismuth-based compound, and the temperature change rate of the dielectric constant is reduced. However, when a dielectric material made of BaT10s with a base metal such as nickel rho as an internal electrode and a bismuth compound added thereto is co-fired at a temperature below the equilibrium oxygen partial pressure of NL'NiO, the bismuth compound is reduced and the insulating properties are lost. However, as a result, satisfactory dielectric properties cannot be obtained.

Furthermore, the dielectric material itself is not reduced even when fired near the equilibrium oxygen partial pressure of Ni/NiO, and BaTiOs is used as a non-reducible dielectric ceramic composition having a small temperature change rate of dielectric constant.
-MnO-MgO based composition disclosed in JP-A-57-71866
It is proposed in the publication No.

This is because MnO and MgO act to suppress the reduction of BaTiOs, and the dielectric is not reduced even when fired near the equilibrium oxygen partial pressure, and has sufficient insulating properties. Since it has a similar de-deressor effect, the rate of change in dielectric constant with temperature is reduced. However, the dielectric ceramic composition described in the above-mentioned publication has a low dielectric constant, and when the amount of MgOm is increased, F
, 1. A. Standards (Electroni, c engineering
stries ASSOOl, atlOn 5tand
ard) temperature change rate of dielectric constant (however, -55°C to +
±15% of +25°C in the range of 125°C
If it is less than 2,200, the dielectric constant becomes even lower to 2200 or less, which has the disadvantage that practical dielectric properties cannot be obtained.

[Purpose of the invention]

The present invention was devised in view of the above-mentioned drawbacks, and its purpose is to provide a composition of BaTiOs, Nbz○5 and MnO with an oxygen partial pressure of 3 at 1250°C to 1350°C.
When fired in an atmosphere of It is an object of the present invention to provide a highly economical high-permittivity non-reducible dielectric ceramic composition that has insulating properties, has a small temperature change rate of dielectric constant over a wide temperature range, and has a small dielectric loss tangent.

[Means for solving problems]

The non-reducible dielectric ceramic composition of the present invention has a composition formula (BaT
i-03)X -(Nb*05)Y @ (Mn○)Z
This is a three-component porcelain composition shown in Figure 1, which is characterized by having a composition within the range surrounded by the following points A, B, C, and D. However, in the above composition formula,
X, Y, Z represent the mole fraction, X + Y + Z
= 100 is satisfied.

YZ A 98.75 0.25 1.0B
89.75 0.25 10.0C89,001,
0010, O D 95.00 1.00 4.0 The present invention improves the curve of BaTj-Os by adding niobium pentoxide (NbzOi), which exhibits the same de-deressor effect as the bismuth-based compounds, to BaTi and Os. By adding Mn○, the maximum value of the dielectric constant in the vicinity is lowered, and the donor level electrons formed by the oxygen defects generated when firing under the low oxygen partial pressure of the temperature change ATM of the dielectric constant are formed by adding Mn○. By recombining at the acceptor level, the dielectric ceramic is prevented from becoming a semiconductor and maintains high insulation properties.

〔Example〕

Next, the present invention will be explained based on examples. As starting materials, BaCO5, Ti, and Ot were subjected to a solid phase reaction at 1150°C to synthesize BaTiOs, which was then pulverized. Next, the synthetic fine powder BaT101, NbgOs and MnC
0z was weighed so as to have the proportions shown in Table 1, and mixed together with a dispersant and a dispersion medium in a ball mill to prepare a raw material souffle. Next, an organic binder was added together with a plasticizer to this raw material Softfree, and after thorough stirring and vacuum defoaming, it was formed into a film using a doctor blade method. Next, 20 sheets of the above films were stacked and bonded together using a hot press to form a plate-shaped sample (thickness: 0.5 m
ll) was cut into a length of about IQ*m and a width of about IQ mm.

The oxygen partial pressure of this sample was controlled at 3 x 10 - 3 x 10 atm, and the carrier gas was N2 gas, and the temperature was 1250'C - 1.
It was baked at 350°C for 2 hours. Finally, an indium-gallium (In-Ga) alloy was applied to both the upper and lower surfaces of the obtained fired body.

After these evaluation samples were left at room temperature for 48 hours, a frequency of 1.00 KHz and an input signal level of 1. O.V.
The capacitance and dielectric loss tangent were measured at rms, and the relative dielectric constant was calculated from the capacitance. Thereafter, a DC voltage of 50 V was applied for 1 minute, and the insulation resistance at that time was measured.

In addition, capacitance and dielectric loss tangent were measured under the same conditions as above in the temperature range of -55℃ to +125℃, and +2
The rate of change in capacitance at each temperature with respect to the capacitance at 5° C. was calculated.

The above results are shown in Table 1. However, the insulation resistance in the table is the product (C
! R, Mn・μF).

As is clear from Table 1, sample numbers 1, 4, 10.15
is Nb20iH (Mo'y fraction ratio Z of pair of MnO
If /Y is less than 4.0, the dielectric ceramic becomes a semiconductor, the insulation resistances C and R are extremely low at 1 to 13 MΩ・μF, and the dielectric loss tangent tan δ is also 4.15 to 12.50%. It has become very large. Also sample number 2, 11.22
As shown in ゜26.33.37, Nt) gos (7
) If the content is less than 0.25 mol% or more than 1600 mol%, the above-mentioned temperature change rate of dielectric constant is ±15
% and deviates from the standard. Further, sample number 38 is a case in which the amount of addition in the order ○ exceeds io, oo%~%, and the dielectric constant is as small as 2500 or less, and practical dielectric properties are not obtained in either case.

On the other hand, the dielectric ceramic composition within the scope of the claims of the present invention has a sufficiently large dielectric constant of 2591 to 3537, an extremely small dielectric loss tangent tan δ of 0.26 to 1.18%, and insulation resistances C and R. The dielectric constant is extremely large, 527 to 1125 MΩ·μF, and the temperature change rate of the above-mentioned dielectric constant is within ±15%, and both have excellent dielectric properties.

〔Effect of the invention〕

The dielectric ceramic composition within the scope of the present invention surrounded by each point ABCD in FIG. 1 has a relative dielectric constant, a dielectric loss tangent tan δ,
Both the insulation resistance C@R and the temperature characteristics of the dielectric constant are satisfactory.

Further, in the present invention, the firing temperature is 1250°C to 13°C.
Under firing conditions where the oxygen partial pressure is less than the equilibrium oxygen partial pressure of Ni/NiO in the range of 50°C, dielectric porcelain can be sintered simultaneously with nickel metal electrodes and satisfies all the dielectric properties of sintered porcelain. Moreover, since the nickel metal fine particles are sintered into a metal film without being oxidized, it is understood that the material is sufficiently practical as a dielectric ceramic for a laminated ceramic capacitor using nickel as an internal electrode.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a ternary diagram showing the composition range of the non-reducible dielectric ceramic composition of the present invention.

Claims (1)

[Claims] The compositional formula is (BaTiO_3)X・(Nb_2O_5)Y・(Mn
O) A non-reducible dielectric ceramic composition, which is a three-component ceramic composition indicated by Z and has a composition within the range surrounded by the following points A, B, C, and D in FIG. However, in the above composition formula, X, Y, and Z represent the mole fraction, and X+Y+Z=10
Satisfies 0. X Y Z A 98.75 0.25 1.0 B 89.75 0.25 10.0 C 89.00 1.00 10.0 D 95.00 1.00 4.0