JPH02242519A - dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To enhance the dielectric constant, insulation resistance, insulation breakdown voltage, and quality Q of a dielectric porcelain composition by making the composition contain a specific amount of tantalum oxide as auxiliary components against main components that the composition contains in such a manner that when an expression is given as xBaO-yTiO-z(Re(1-c)Mec)O3/2 (x), (y) and (z) are in a specific mot ratio range. CONSTITUTION:The dielectric porcelain composition is made to contain tantalum oxide as auxiliary component by 0.1 to 12.0 parts by weight in Ta2O5 against 100 parts by weight of main components that the composition contains in such a manner that when an expression is given as xBaO-yTiO-z(Re(1-c)Mec)O3/2 (x+y+z=1.00; 0.01<=C<=0.10, Re is more than one kind of rare earth materials selected among La, Pr, Nd and Sm) (x), (y) and (z) are in a mol ratio range surrounded by points (a) to (f) io the figure. The composition thereby has its dielectric constant, insulation resistance, and insulation breakdown voltage all enhanced, its quality Q largely improved, and its temperature coefficient of electrostatic capacity reduced.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention has high dielectric constant, insulation resistance, and dielectric breakdown voltage, greatly improves quality Q, and has a small capacitance temperature coefficient, and is suitable for multilayer ceramic capacitors. In terms of use, the present invention relates to a dielectric ceramic composition that can prevent a decrease in capacitance and quality Q when the thickness of internal electrodes is reduced, and can reduce variations in capacitance and quality Q.

Conventional technology Conventionally, the dielectric constant and insulation resistance are high, and the quality Q is excellent.
The following systems are known as dielectric ceramic compositions with small capacitance temperature coefficients.

・B a O-T i 02-N d203 series-BaO
Problems to be solved by the -TiO2-8m203-based invention However, these compositions, for example, 0.09BaOO, 5
A dielectric material with a composition ratio of 6Ti020.35NdO3/2 was used, the palladium internal electrode thickness was 4 μm, the dielectric thickness was 12 μm, and the internal electrode overlap dimensions were 1 and 2 m.
When a multilayer ceramic capacitor with a laminated structure of m x 0, 7 mm, and 19 dielectric layers is manufactured, the average capacitance is near 42 pF, and the average quality Q is 8700.
．． Average value of capacitance temperature coefficient: N 35ppm/°C
, the average value of insulation resistance was 6.0×10 12 Ω, and the average value of dielectric breakdown strength was 117 kv/mm, which are not satisfactory values for insulation resistance and dielectric breakdown strength.

In addition, in order to reduce the cost of multilayer ceramic capacitors and to prevent the occurrence of delamination, which is a structural defect inside the element body, the thickness of the palladium internal electrode was increased to 4 μm.
m to 2 μm (then, the average capacitance of a multilayer ceramic capacitor using a dielectric material with the above composition ratio, and having a multilayer structure with the above dielectric thickness, internal electrode claw dimensions, and number of dielectric layers) As the value becomes smaller (610r) F (as the capacitance variation increases from 256 to 713 pF), the average value of the quality Q also decreases to 4000.= and the variation in the quality Q increases from 600 to 8800. There was a problem.

Means for Solving the Problems In order to solve these problems, the present invention provides a formula xBa
O-yT 102-z (Reu-z)Mec)03/
When expressed as 2, (where x+y+z=1.OO 0,01≦C≦0.20 Re is at least one rare earth element selected from La, Pr, Nd, and Sm.

Me is at least one rare earth element selected from rare earth elements excluding La, Pr, Nd, and Sm. ) Each point a, b, c where x, y, z are represented below.

Product component 10 consisting of the molar ratio range surrounded by d, e, f
0 parts by weight, tantalum oxide is added as a subcomponent to Ta2
The present invention proposes a dielectric ceramic composition characterized in that it contains 0.1 to 12.0 parts by weight calculated as 0.05.

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. Furthermore, in region B, the quality Q decreases, making it 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 small (not practical).

Furthermore, by selecting Re 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, as is clear from Tables 1 and 2, which will be described later, L
a, Pr, Nd, and Sm.

A small number ( selected from rare earth elements excluding Pr, Nd, and Sm)
By replacing both with one or more rare earth elements, it has the effect of significantly improving the goodness factor Q, and the amount of substitution C is 0.
If it is less than 0.01, there will be no substitution effect, and if it exceeds 0.20, the dielectric constant will decrease and become impractical.

FIG. 2 is a graph showing the effect of the addition of the subcomponent molecule a205 on the characteristics of a multilayer ceramic capacitor with respect to the main component of the composition according to the present invention. I will explain. As shown in Figure 2, the inclusion of Ta205 improves insulation resistance and dielectric breakdown strength, increases capacitance and quality Q, and reduces variations in capacitance and quality Q. have an effect.

Insulation resistance and dielectric breakdown strength are improved by the inclusion of Ta205, or the content of Ta205 is 100% as the main component.
If the amount is less than 0.1 part by weight, the capacitance and quality Q are low, and the capacitance and quality Q vary widely, so it is excluded from the scope of the present invention. On the other hand, T a 2
If the content of 05 exceeds 12.0 parts by weight based on the main component, the quality Q and insulation resistance will decrease, and the temperature coefficient of capacitance will become large on the negative side, making it impractical.

Example The present invention will be explained below using specific examples.

(Example 1) Chemically highly purified B a C03T i was used as the starting material.
02. L a203. Preo++, Nd2O
3゜Sm2O3, CeO2, Gd2O3, Dy2O3, and Ta205 powders were weighed to have the composition ratio shown in Table 1 below, put into a rubber-lined ball mill equipped with agate balls together with pure water, and after wet mixing, dehydrated and dried. did. Place this dry powder in a high alumina crucible and place it in air for 11. Calcining was performed at 00°C for 2 hours. This calcined powder was put into a rubber-lined ball mill equipped with agate balls together with pure water, wet-pulverized, and then dehydrated and dried. After adding an organic binder to this pulverized powder and making it homogeneous, the powder is sized through a 32-mesh sieve, and the molding pressure is 1 ton/cn using a mold and a hydraulic press. with a diameter of 15 mm and a thickness of 0.
It was molded into 4nun. Next, this molded disk was placed in an alumina pod covered with zirconia powder, and dielectric porcelain having the composition ratio shown in Table 1 below was obtained in air.

The thickness and diameter of the dielectric porcelain disk thus obtained were measured, and the samples for measuring the dielectric constant, goodness Q, and capacitance temperature coefficient were prepared using silver electrodes on both sides of the dielectric porcelain disk. A sample for baking, insulation resistance, and dielectric breakdown strength measurement 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. In addition, the dielectric constant, goodness Q,
The capacitance temperature coefficient was measured using a YHP digital LCR meter model 4275A at a measurement temperature of 20'C and a measurement voltage of 1. OVrms was determined by measurement at a measurement frequency of IMHz. Note that the temperature change in capacitance is 55°C,
The capacitance was measured at -25°C, 20°C, 85°C, and 125°C to confirm linearity, and the temperature coefficient of capacitance was determined using the capacitance at 20°C and 85°C. It was calculated using the formula.

TC-(C-Co)/CoX1/65X
10 GTC: Capacitance temperature coefficient (ppm/℃) 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 , using HR meter model 4329A manufactured by Y HP, measuring voltage 50V.

D, C,... Determined from measurements with a measurement time of 1 minute.

The dielectric breakdown strength was determined by using a high-voltage power supply PH335 manufactured by Kikusui Electronics Co., Ltd., type 13, placing the sample in Zinocon oil, and dividing the dielectric breakdown voltage determined by a voltage increase rate of 50 V/see by the dielectric thickness. Dielectric breakdown strength per 1 mm.

The test conditions are also shown in Table 1, and the test results are shown in Table 2 below.
Shown in the table.

(Left below) (Example 2) The starting material was chemically highly purified BaCO3Ti○2. N
Using d2O+, Ce02 and Ta205 powder,
Main component 0.098 a○-0,56TiCh0.35
[(Nd○3/2) o, 9s (CCO2)0.0
5], Ta205 was 0.0.1, 0.5, 1.0
A calcined and pulverized powder containing 5.0, 10.0, 12.0, and 15.0 t% is prepared in the same manner as in Example 1.

However, the Ta205 content is 0. ], 55.0wt is outside the scope of this invention, and 0.1, 0.5. ],,0゜5
．． 0, 10.0, 12.0 wt% are within the scope of this invention.

An organic binder, a plasticizer 2 dispersant, and an organic solvent were added to this calcined and pulverized powder, and mixed in a polyethylene pot equipped with alumina balls to prepare a slurry. After mixing, 3
00 metsushi. It was filtered using nylon cloth. The slurry after filtration was molded into a sheet using a doctor blade on a polyester film which had been subjected to mold release treatment so that the dielectric thickness after sintering was 12 μm. Next, 10 sheets peeled from the polyester film were laminated on a support base. On top of this, Shoei Kagaku (Kikku's back electrode palladium paste ML-3724) was screen printed so that the internal electrode thickness after sintering was 2 μmk, and dried. On top of this, a sheet peeled from the polyester film was laminated. On top of this, the internal electrode overlap dimension after sintering is 1,
The internal electrode palladium paste was printed by shifting the printing position so that it was 2 mm x 0 and 7 mm, and after drying, one sheet peeled from the polyester film was laminated. These operations were repeated until the number of dielectric layers reached 19. On top of this, add 1 polyester fill!
11 sheets were laminated. After sintering this laminate, the internal electrode overlap dimensions are 1, 2 mm x 0, 7
The capacitor was cut into a multilayer ceramic capacitor having a laminated structure with a dielectric thickness of 12 μm, a dielectric thickness of 12 μm, and 19 dielectric layers. This cut sample was placed in an alumina sheath lined with zirconia powder and exposed to air from room temperature to 350°C.
'C at a rate of 56C/hr, then 10℃ from 350℃.
The temperature was raised at 0'C/hr, and after firing at 1270°C for 24 hours, the temperature was lowered to room temperature at 00C/hr. Next, the fired sample was placed in a polyethylene pot lined with water-resistant sandpaper along with pure water.
The polyethylene bottle 1~ was rotated to polish the sample surface after firing to fully expose the internal electrode portion to be bonded to the external electrode. This sample was removed from the polyethylene pot and dried.
A silver external electrode was baked onto the exposed part of the internal electrode to make it conductive with the internal electrode, creating a multilayer ceramic capacitor.

The capacitance, quality Q, temperature coefficient of capacitance, insulation resistance, and dielectric breakdown strength of these samples were determined by measurements under the same conditions as in Example 1. In addition, confirmation of the laminated structure is approximately 1/2 of the length and width of the laminated ceramic container.
The internal electrode overlap dimension is a polished cross section with a magnification of 100. The dielectric thickness and the internal electrode thickness were determined by optical microscope observation at a magnification of 400.

The results of this E11 determination are shown in FIG.

In addition, the method for manufacturing the dielectric ceramic in the examples is based on Ba
C03, T i○2. L a203. Pr60
IN d203. Sm2O3, Ce 02. G d20
3. Although D y203 and Ta205 were used, the method is not limited to this method, and Bad can be obtained by heating a compound such as BaTiO3, carbonate, or hydroxide in air to obtain a desired composition ratio.

T i 02. L a201 P raou, N
d203Sm203. CeO2, Gd2O+, D'/2
Even if compounds such as 03 and Ta205 are used, properties comparable to those of the examples can be obtained.

Further, even if the main component is roughened and calcined and subcomponents are added, properties comparable to those of the examples can be obtained.

In addition, in the examples, Ce, Dy, and Gd were explained as rare earth elements Me other than La, Pr, Nd, and Sm, but characteristics comparable to those in the examples can be obtained even if other rare earth elements are used. .

In addition to the basic composition mentioned above, SiO2MnO2, F
Salts, oxides, etc., which are generally considered to be fluxes, such as e2O3 and ZnO, can also be added to the extent that they do not impair the properties.

Effects of the Invention As described above, according to the present invention, the dielectric constant, insulation resistance, and dielectric breakdown voltage are high, the quality Q is greatly improved, the capacitance temperature coefficient is small, and the capacitor can be used in multilayer ceramic capacitors. In order to prevent a decrease in capacitance and quality Q when the thickness of the internal electrode is made thinner, and to reduce variations in capacitance and quality Q, the thickness of the internal electrode is made thinner.
The cost of multilayer ceramic capacitors can be reduced, and delamination, which is an internal structural defect, can be prevented from occurring. Furthermore, since the dielectric breakdown voltage is high, the thickness of the dielectric layer can be reduced, making it possible to miniaturize the product and increase the capacity.

[Brief explanation of drawings]

FIG. 1 is a ternary diagram explaining the composition range of the main components of the composition according to the present invention, and FIG. 2 is a ternary diagram illustrating the composition range of the main components according to the present invention.
BaO-0,56TiO20,35[(N d 03/
2) 0.95 (Ce 02) 0.05], the effect of the addition of subcomponent element a205 on dielectric thickness 12 μm
, internal electrode overlap dimensions: 1, 2 mm x 0,
7 mm. This is a graph showing the electrical characteristics of a multilayer ceramic capacitor having a laminated structure with 19 dielectric layers. Name of agent: Patent attorney Shigetaka Awano and 1 other person] 8

Claims (1)

[Claims] General formula xBaO-yTiO_2-z(Re_(_1_-_C_
)Me_C)O_3_/_2 (where x+y+z=1.00 0.01≦C≦0.20 Re is at least one rare earth element selected from La, Pr, Nd, and Sm. Me is , La, Pr, Nd, and at least one rare earth element selected from rare earth elements excluding Sm.) Each point a, b, c, d, e, f where x, y, and z are represented below.
A dielectric ceramic composition characterized in that it contains 0.1 to 12.0 parts by weight of tantalum oxide as a subcomponent in terms of Ta_2O_5 with respect to 100 parts by weight of the main component having a molar ratio within the range of . ▲Contains mathematical formulas, chemical formulas, tables, etc.▼