JPH04357616A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a porcelain composition having a high dielectric constant, a low dielectric loss, a large dielectric voltage, large insulating resistance, and a small diameter of a crystalline particle by using a compound having a specific composition including Ba, Mg, Ti, Zr and rare earth oxide. CONSTITUTION:A composition expressed by Formula (x)>>(BaO)(1-m).(MgO)m].(y)>>(TiO2)(1-n)(ZrO2)n].(z)(R(1-t)Me)t)O3/2 is used, wherein R represents one kind or more of La, Pr, Nd and Sm; Me, a rare earth element other than La, Pr, Nd and Sm; and (m) ranges from 0.01 to 0.50; (n), from 0.001 to 0.200; and (t), from 0.01 to 0.20. (x)+(y)+(z)=1. 0.3-5.0 parts by weight of niobium in a form of Nb2O5 are incorporated into 100 parts by weight of a main component within a range of mol ratios surrounded by a point (a) of (x)=0.15, (y)=0.50, and (z)=0.35, a point (b) of (x)=0.16, (y)=0.61, and (z)=0.23, a point (c) of (x)=0.10, (y)=0.67, and (z)=0.23, a point (d) of (x)=0.09, (y)=0.60, and (z)=0.31, a point (e) of (x)=0.02, (y)=0.58, and (z)=0.40, and a point (f) of (x)=0.02. (y)=0.52, and (z)=0.46.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition for a fixed ceramic capacitor for electronic equipment.

0002

BACKGROUND OF THE INVENTION Conventional dielectric ceramic compositions will be explained below. The following systems are known as dielectric ceramic compositions.

[0003] BaO・TiO2・Nd2O3 system BaO・
TiO2/Sm2O3 system e.g. 0.09BaO/0.56TiO2/0.35N
A dielectric ceramic disk was prepared using a dielectric ceramic composition having a composition ratio of dO3/2, and its electrical properties and crystal grain size were measured. Dielectric constant: 67, Capacitance temperature coefficient: N40
ppm/℃, Q: 3000, insulation resistance: 8.0×101
2Ω, dielectric breakdown strength: 30kv/mm and crystal grain size:
Values of 1-5 μm were obtained.

0004

[Problems to be Solved by the Invention] However, in the above conventional configuration, the insulation resistance is low and the crystal grain size is large, so the porosity in the element body increases and the electric field strength applied to each crystal grain increases. Since this increases, there is a problem in that the dielectric breakdown strength is also low.

The present invention solves the above-mentioned conventional problems, and aims to provide a dielectric ceramic composition capable of obtaining a dielectric ceramic having a small crystal grain size and high insulation resistance and dielectric breakdown strength. shall be.

[0006]

[Means for Solving the Problem] In order to solve this problem, the dielectric ceramic composition of the present invention has the general formula x[(BaO)
(1-m)(MgO)m]・y[(TiO2)(1-n
)(ZrO2)n]・z(R(1-t)Met)O3/
2, where R is one or more rare earth elements selected from La, Pr, Nd, and Sm, and Me is La, Pr, and Nd.
, one or more rare earth elements selected from rare earth elements excluding Sm, and the values of m, n and t are 0.01≦m≦0.
50, 0.001≦n≦0.200 and 0.01≦t
≦0.20, and x, y, and z represent molar ratios, where x+y+z=1, the values of x, y, and z are in the range of x=0.15, y=0. 50, z=0.35,
b is x=0.16, y=0.61, z=0.23, c is x=0.10, y=0.67, z=0.23, d is x=
0.09, y=0.60, z=0.31, e is x=0.
02, y=0.58, z=0.40, f is x=0.02
, y=0.52, z=0.46, a, b, c, d
, e, and f, and 0.3 to 5.0 parts by weight of niobium in the form of Nb2O5.

[0007] Also, instead of niobium, tantalum can be used as Ta2.
It is contained in an amount of 0.1 to 10.0 parts by weight in terms of O5 form.

Furthermore, instead of niobium, vanadium is contained in an amount of 0.005 to 1.000 parts by weight in the form of V2O5.

Furthermore, in place of niobium, two or more selected from niobium, tantalum, and vanadium are Nb2O5.
, Ta2O5, V2O5 in total is 0.00
It contains 1 to 0.010 mole part.

0010

[Operation] With this configuration, R can be changed to La, Pr, Nd, S
By selecting from m, the capacitance temperature coefficient shifts in the positive direction in the order of La, Pr, Nd, and Sm.

[0011] Further, a part of one or more rare earth elements selected from La, Pr, Nd, and Sm may be replaced with La, Pr, Nd,
Q can be increased by substituting with one or more rare earth elements selected from rare earth elements other than Sm.

Furthermore, by substituting BaO with MgO, the temperature coefficient of capacitance is shifted to the positive direction, and the insulation resistance is increased.

[0013] By substituting TiO2 with ZrO2, the crystal grain size is reduced and the dielectric breakdown strength is increased.

Furthermore, by containing niobium, tantalum, vanadium, or two or more selected from these as subcomponents, the insulation resistance and dielectric breakdown strength can be increased.

[0015]

[Embodiment] An embodiment of the present invention will be described below.

(Example 1) Chemically high-purity Nb2O5, La2O3, Pr6O11, Nd2O3 are used as starting materials.
, Sm2O3, CeO2, Gd2O3, Dy2O3, Z
rO2, TiO2, MgO and BaCO3 powders were weighed so as to have the composition ratios shown below (Table 1), put into a rubber-lined ball mill equipped with agate balls together with pure water, wet mixed, and then dehydrated and dried. This dry powder was placed in a high alumina crucible and calcined in air at 1100°C for 2 hours. This calcined powder was put into a rubber-lined ball mill equipped with agate balls together with pure water, and after wet grinding,
Dehydrated and dried. After adding an organic binder to this pulverized powder and making it homogeneous, the powder was sized through a 32-mesh sieve, and the molding pressure was 1 ton/cm2 using a mold and a hydraulic press.
It was molded to a diameter of 15 mm and a thickness of 0.4 mm. Then,
The thus obtained molded disks were placed in an alumina pod covered with zirconia powder and fired in air at the firing temperatures shown in Table 1 for 2 hours. A dielectric ceramic disk with a composition ratio was obtained.

[0017]

[Table 1]

The thickness and diameter of the dielectric ceramic disk thus obtained were measured, and the sample for measuring the dielectric constant, Q, and capacitance temperature coefficient was prepared using silver electrodes on both sides of the dielectric ceramic disk. A sample for measuring insulation resistance and dielectric breakdown strength was prepared by providing a 1 mm wide portion without a silver electrode inside the outer periphery of a dielectric ceramic disk, and baking a silver electrode thereon. And the dielectric constant, Q,
The capacitance temperature coefficient was determined using a digital LCR meter model 4275A manufactured by Yokogawa-Hewlett-Packard Co., Ltd. at a measurement temperature of 20° C., a measurement voltage of 1.0 Vrms, and a measurement frequency of 1 MHz. The capacitance temperature coefficient was determined by measuring capacitance at 20° C. and 85° C. using the following formula.

TC=(C-Co)/Co×1/65×106TC: Temperature coefficient of capacitance (ppm/°C) Co: Capacitance at 20°C (pF) C: Capacitance at 85°C (pF) Further, the dielectric constant was determined from the following formula.

K=143.8×Co×t/D2K: Dielectric constant Co: Capacitance at 20°C (pF) D: Diameter of dielectric ceramic (mm) t: Thickness of dielectric ceramic (mm) Further , insulation resistance was measured using Yokogawa-Hewlett-Packard Co., Ltd. HR meter model 4329A, and the measurement voltage was 50V. D. C. , was determined from measurements with a measurement time of 1 minute.

[0021]The dielectric breakdown strength was determined by Kikusui Electronics (
Using a high voltage power supply model PHS35K-3 manufactured by Co., Ltd., the sample was placed in silicone oil, and the dielectric breakdown voltage determined at a voltage increase rate of 50 V/sec was divided by the dielectric thickness to obtain the dielectric breakdown strength per 1 mm.

Further, the crystal grain size was determined by optical microscope observation at a magnification of 400. The above measurement results are sample numbers 1 to 10.
It is shown separately (Table 2).

[0023]

[Table 2]

FIG. 1 is a ternary diagram showing the composition range of the main components of the composition according to the present invention, and the reason for limiting the composition range of the main components will be explained with reference to FIG. That is, sintering is extremely difficult in region A. Further, in region B, Q is small and becomes impractical. Furthermore, in regions C and D, the capacitance temperature coefficient becomes too large on the negative side, making it impractical. In region E, the temperature coefficient of capacitance shifts to a positive direction, but the dielectric constant is too small to be practical. In addition, by selecting R from La, Pr, Nd, and Sm, it is possible to shift the capacitance temperature coefficient in the positive direction without significantly lowering the dielectric constant in the order of La, Pr, Nd, and Sm. , La, Pr, Nd, and Sm, or a combination thereof, the capacitance temperature coefficient can be adjusted.

Furthermore, a part of one or more rare earth elements selected from La, Pr, Nd, and Sm is
, Sm is substituted with one or more rare earth elements selected from rare earth elements other than Sm, which has the effect of increasing Q. However, if the substitution rate t is less than 0.01, there is no substitution effect; If it exceeds 20, the dielectric constant becomes too small to be practical.

[0026] Furthermore, by replacing BaO with MgO, it is possible to shift the capacitance temperature coefficient in the positive direction and increase the insulation resistance without significantly changing the values of dielectric constant, Q, and dielectric breakdown strength. However, if the substitution rate m is less than 0.01, there is no substitution effect, while if it exceeds 0.50, the dielectric constant becomes small and is not practical.

Furthermore, by replacing TiO2 with ZrO2, it is possible to reduce the crystal grain size and increase the dielectric breakdown strength without significantly changing the dielectric constant, Q, temperature coefficient of capacitance, and insulation resistance. However, if the substitution rate n is less than 0.001, there is no substitution effect; on the other hand, 0.20
When it exceeds 0, the dielectric constant, Q, and insulation resistance become small.

[0028] Then, with respect to the main component, N as a subcomponent
Containing b2O5 has the effect of increasing insulation resistance and dielectric breakdown strength, but if the content of Nb2O5 is less than 0.3 parts by weight per 100 parts by weight of the main component, the dielectric breakdown strength is not so high. Therefore, it is excluded from the scope of this invention. On the other hand, the content of Nb2O5 is
If it exceeds 5.0 parts by weight, the insulation resistance (Q) decreases and the temperature coefficient of capacitance increases to the negative side, making it impractical.

(Example 2) High-purity Ta2O5 powder was used in place of high-purity Nb2O5 in the raw materials of Example 1, and the composition ratio was as shown in Table 3 below. Dielectric ceramic disks having the composition ratios shown in sample numbers 11 to 20 in Table 3 were obtained by processing the steps in the same manner as in Example 1, and the results were obtained by processing in the same manner as in Example 1 and measuring the characteristics. Sample number 1
1 to 20 (Table 4).

[0030]

[Table 3]

[0031]

[Table 4]

[0032] Here, the reason for limiting the composition range and structure of the main components is the same as in Example 1, so the explanation will be omitted. The addition of Ta2O5 as a subcomponent to the main component has the effect of increasing insulation resistance and dielectric breakdown strength;
If the amount is less than 0.1 part by weight, the dielectric breakdown strength is not so large and it is excluded from the scope of the present invention. On the other hand, if the content of Ta2O5 exceeds 10.0 parts by weight based on the main component, the insulation resistance (Q) decreases and the temperature coefficient of capacitance increases to the negative side, making it impractical.

(Example 3) High-purity V2O5 powder was used in place of high-purity Nb2O5 in the raw materials of Example 1, and the composition ratio was as shown in Table 5 below. Dielectric ceramic disks having the composition ratios shown in sample numbers 21 to 30 in Table 5 were obtained by processing the steps in the same manner as in Example 1, and the results were obtained by processing in the same manner as in Example 1 and measuring the characteristics. Sample number 21
~30 separately (Table 6).

[0034]

[Table 5]

[0035]

[Table 6]

[0036] Here, the reason for limiting the composition range and structure of the main components is the same as in Example 1, so the explanation will be omitted. By containing V2O5 as a subcomponent to the main component, it has the effect of increasing insulation resistance and dielectric breakdown strength, but the content of V2O5 is 100% of the main component.
If the amount is less than 0.005 parts by weight, the dielectric breakdown strength is not so high and it is excluded from the scope of the present invention. On the other hand, if the content of V2O5 exceeds 1.000 parts by weight based on the main component, the insulation resistance will decrease, making it impractical.

(Example 4) In place of high-purity Nb2O5 among the raw materials of Example 1, high-purity Nb2O5, Ta2O
5 and V2O5 powder were weighed so as to have the composition ratio shown in Table 7 below, and the subsequent steps were performed in the same manner as in Example 1 to obtain the compositions shown in sample numbers 31 to 40 (Table 7). Dielectric ceramic disks of different proportions were obtained, treated in the same manner as in Example 1, and their characteristics were measured. The results are shown in Table 8 for sample numbers 31 to 40.

[0038]

[Table 7]

[0039]

[Table 8]

[0040] Here, the reason for limiting the composition range and structure of the main components is the same as in Example 1, so the explanation will be omitted. Then, with respect to the main component, Nb2O5 and T as subcomponents
By containing a2O5 and V2O5, insulation resistance,
Although it has the effect of increasing dielectric breakdown strength, Nb2
The total content of O5, Ta2O5, and V2O5 is the main component 1
If the amount is less than 0.001 parts by mole, the dielectric breakdown strength is not so large and is excluded from the scope of the present invention. On the other hand, if the total content of Nb2O5, Ta2O5, and V2O5 exceeds 0.010 mole part based on the main components, Q,
The insulation resistance becomes small and the temperature coefficient of capacitance becomes large on the negative side, making it impractical. Also, Nb2O5,T
By containing two or more types selected from a2O5 and V2O5, the dielectric constant, Q, insulation resistance, and dielectric breakdown voltage are larger, and the capacitance temperature coefficient is higher than those containing one type selected from Nb2O5, Ta2O5, and V2O5. can be made smaller.

[0041] In the method for manufacturing dielectric ceramic in the above embodiment, V2O5, Ta2O5, Nb2O5, La
2O3, Pr6O11, Nd2O3, Sm2O3, Ce
O2, Gd2O3, Dy2O3, ZrO2, TiO2,
Although MgO and BaCO3 were used, the method is not limited to this method, and BaCO3 can be used to obtain a desired composition ratio.
By heating compounds such as TiO3, carbonates, and hydroxides in air, V2O5, Ta2O5, Nb2
O5, La2O3, Pr6O11, Nd2O3, Sm2
O3, CeO2, Gd2O3, Dy2O3, ZrO2,
Even if compounds such as TiO2, MgO, and BaO are used, properties comparable to those of the examples can be obtained.

[0042] Furthermore, even if the main component is calcined in advance and subcomponents are added, properties comparable to those of the examples can be obtained.

Furthermore, titanium dioxide, an industrial raw material commonly used for dielectric ceramics, such as titanium dioxide KA-10C manufactured by Titan Kogyo Co., Ltd. and titanium dioxide FA-55W manufactured by Furukawa Mining Co., Ltd., has a maximum of 0. 45% by weight Nb2
Although O5 is included, even if the dielectric ceramic having the main component of Example 1 is made using these titanium dioxides, the main component is 100%.
The content of Nb2O5 is at most 0.2 parts by weight, which is outside the scope of this invention, but considering the amount of Nb2O5 in titanium dioxide, which is an industrial raw material,
By containing 2O5, properties comparable to those of the examples can be obtained.

[0044] In addition to the above basic composition, SiO2
, MnO2, Fe2O3, ZnO, Al2O3, and other salts and oxides that are generally considered to be fluxes.
It can also be added within a range that does not impair the characteristics.

[0045]

Effects of the Invention As is clear from the description of the examples above, the present invention provides the following advantages:
)m]・y[(TiO2)(1-n)(ZrO2)n]
・Represented by z(R(1-t)Met)O3/2, in the formula R
is one or more rare earth elements selected from La, Pr, Nd, and Sm; Me is one or more rare earth elements selected from rare earth elements other than La, Pr, Nd, and Sm;
and the value of t is 0.01≦m≦0.50, 0.001≦
It has a composition in the range of n≦0.200 and 0.01≦t≦0.20, and x, y, and z represent the molar ratio, and when x+y+z=1, the values of x, y, and z are in the predetermined range. The main component is a composition in the molar ratio range surrounded by a, b, c, d, e, f indicating the numerical value of Depending on the structure of the dielectric ceramic composition, it is possible to obtain a dielectric ceramic having a small crystal grain size, a large dielectric constant, Q, insulation resistance, and dielectric breakdown voltage, and a small temperature coefficient of capacitance.

[Brief explanation of the drawing]

FIG. 1 is a ternary diagram illustrating the composition range of the main components of a dielectric ceramic composition in one embodiment of the present invention.

Claims (4)

[Claims] Claim 1: The general formula is x[(BaO)(1-m)(
MgO)m]・y[(TiO2)(1-n)(ZrO2
)n]・z(R(1-t)Met)O3/2,
In the formula, R is one or more rare earth elements selected from La, Pr, Nd, and Sm; Me is one or more rare earth elements selected from rare earth elements other than La, Pr, Nd, and Sm;
The values of m, n and t are 0.01≦m≦0.50, 0.0
01≦n≦0.200 and 0.01≦t≦0.20, and x, y and z represent molar ratios, and x
+y+z=1 and the values of x, y, z are: a is x=0.15, y=0.50, z=0.35, b is x=0.16, y=0.61, z=0 .23, c is x=
0.10, y=0.67, z=0.23, d is x=0.
09, y=0.60, z=0.31, e is x=0.02
, y=0.58, z=0.40, f is x=0.02, y
=0.52, z=0.46, a, b, c, d, e
, f, and 0.3 to 5.0 parts by weight of niobium in the form of Nb2O5. 2. The dielectric ceramic composition according to claim 1, containing 0.1 to 10.0 parts by weight of tantalum in the form of Ta2O5 instead of niobium. 3. The dielectric ceramic composition according to claim 1, which contains 0.005 to 1.000 parts by weight of vanadium in the form of V2O5 in place of niobium. Claim 4: Instead of niobium, two or more selected from niobium, tantalum, and vanadium are Nb2O5, Ta2O5
, 0.001 to 0.01 in total when converted to V2O5 form
The dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition contains 0 mole part.