JPH0635339B2 - High dielectric constant porcelain composition - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high dielectric constant porcelain composition, and more particularly to a low temperature sintering type high dielectric constant porcelain composition synthesized by a solid phase reaction of a complex oxide.

Conventional technology Conventionally, as a high dielectric constant porcelain composition, a composite dielectric porcelain material containing barium titanate as a main component and calcium zirconate (CaZrO ₃ ), calcium titanate (CaTiO ₃ ) and the like has been widely used. Has been converted. On the other hand, there is a demand for a small-sized large-capacity capacitor for both general use and industrial use, which requires smaller size and larger capacity than ever before, and in order to meet the demand, a monolithic ceramic capacitor has been put into practical use. In the case of this monolithic ceramic capacitor, gold (A
Noble metals such as u), platinum, palladium (Pd) or platinum palladium are used. This is due to the following reasons. A monolithic ceramic capacitor is manufactured by stacking ceramic green sheets on which internal electrodes are printed, thermocompressing them, firing them at 1200 to 1400 ° C. in air, and then providing external electrodes on both ends. Therefore, the internal electrode material is required to be a metal that does not react with the dielectric ceramic material even if it is fired in the air at such a high temperature and does not oxidize, and it is limited to noble metals such as palladium and platinum that satisfy this requirement. Is.

However, these internal electrode materials account for 30 to 50% of the product price, which is a major obstacle to lowering the price of monolithic ceramic capacitors. Furthermore, there were many problems such as loss of time and cost associated with maintenance of the firing electric furnace.

Problems to be Solved by the Invention By improving the above drawbacks, it is not necessary to use an expensive noble metal as an internal electrode material, and the dielectric constant and the insulation resistance are large.
It is to provide a dielectric ceramic composition that can be fired at a low temperature of ˜1100 ° C.

B. To achieve the construction problem of the Invention The present invention is lead oxide, magnesium oxide, niobium oxide, made of indium oxide, the general formula _{^{x pb (Mg 1/3 Nb}} 2/3) O 3-y (In 1
/ ₂ Nb ^_1/2) when expressed in O ₃ (where, x + y = 1), x = 0.
It is a high dielectric constant porcelain composition characterized by comprising a composition range of 5 to 0.9 and y = 0.1 to 0.5.

In _{^{x pb (Mg 1/3 Nb}} 2/3) O 3-y (In 1/2 Nb 1/2) O 3 _{^{system, Pb (Mg 1/3 Nb}} 2/3) which is one of the main components O ₃ Is a ferroelectric material with a perovskite structure and a high dielectric constant (approximately 20000) and high insulation resistance (> 10 ¹² Ω), but it has a high sintering temperature (> 1200 ° C) and a Curie temperature of -8. It cannot be used because it is on the low temperature side of ℃. Moreover, the temperature characteristics are not sufficient for use as a capacitor material. Inventors have result of various studies the ^{_{Pb (Mg 1/3 Nb 2}} /3) O 3 system ^{_{Pb (In 1/2 Nb 1}} /2) O 3
By adding the system, the binary system material is Pb (Mg ^{1
_{/ 3 Nb 2/3) O}} 3 above the sintering temperature drop while maintaining high characteristics of system, reduction of the Curie temperature, in which found a good material that solves improvements such as temperature characteristics.

Next, the reasons for limiting the composition range of the present invention will be described. Pb
_{^{(Mg 1/3 Nb 2/}} 3) added to the content of O ₃ to system _{^{Pb (In 1/2 Nb 1}} /2) O 3 is lowered sinterability and exceeds 50%, the dielectric constant Is significantly reduced. If the content is less than 10%, the sintering temperature is high and the Curie temperature is low, and the effect of the addition cannot be obtained.

Example The present invention uses lead oxide (PbO), magnesium oxide (MgO), niobium oxide (Nb ₂ O ₅ ), indium oxide (In
₂ O ₃ ) and weigh it to the mixing ratio shown in Table 1. Next, this was wet-mixed in a ball mill and then calcined at 800 ° C. This powder was wet pulverized and dried in a ball mill, mixed with an organic binder, pressure-molded at a pressure of 3.0 ton / cm ² into pellets having a diameter of about 16 mm and a thickness of 2 mm, and fired at 900 to 1100 ° C. After that, silver paste was applied to the sintered body and baked at 600 ° C. to obtain a measurement sample. Capacity and tan δ are frequency 1kHZ,
The relative permittivity ε was calculated by the following equation, using an impedance analyzer at room temperature of 25 ° C.

C: Capacitance (pF) S: Electrode area (cm ² ) d: Dielectric thickness (cm) Next, a ratio of 100 V applied with a super insulation resistance meter for 1 minute and insulation resistance measured at a temperature of 25 ° C. The resistance was calculated. The characteristics corresponding to each composition were obtained from the average of 10 points of each sample. The results are shown in Table 1, of which Sample Nos. 1 to 5 are N
o is a comparative example. As is clear from Table 1, the porcelain composition of the present invention was sintered at a temperature of 1100 ° C. or lower, and the sintered body had a high dielectric constant of 5000 to 8000 at room temperature and a dielectric loss (tan
It can be seen that δ) is as small as 3% or less. The temperature characteristics of the dielectric constant are shown in FIG. Each number in the figure is the sample No. in Table 1.
It corresponds to. XPb As can be seen from FIG. _{^{(Mg 1/3 Nb 2/}} 3) O
Curie point of the _{3 ^{(In 1/2 Nb 1/}} 2) porcelain composition according slide into increasing the amount of O ₃ becomes smaller even if the temperature change rate of the shift to the high temperature side dielectric constant. Then, the Curie point coincides with the room temperature (25 ° C.) by adding 50 mol%.

As described above, the porcelain composition of the present invention can be sintered at a temperature of 1100 ° C. or less and has a high dielectric constant of 5000 to 8000 and 3%.
It has the following low dielectric loss (tan δ) and is suitable not only for ordinary disk capacitors but also for multilayer capacitors and thick film capacitors.

C. Therefore, according to the present invention, the firing furnace for firing the porcelain composition is
Heat resistance up to 1100 ° C is all that is required, so it is inexpensive, and energy consumption for low temperature firing can be saved. Furthermore, low cost is achieved without using expensive metals such as gold, platinum, and palladium for the internal electrodes in multilayer ceramic capacitors. The effect of the present invention is great because inexpensive silver-based metals can be used.

[Brief description of drawings]

FIG. 1 shows the temperature characteristics of the dielectric constant of the high dielectric constant porcelain composition. In the figure, 1, 2 and 4 are the examples of the present invention, and sample No. 1 of Table 1
Nos. 2 and 4 correspond to No. in the comparative example.

Claims (1)

[Claims] 1. Lead oxide, magnesium oxide, niobium oxide,
Made of indium oxide, when expressed by the general formula _{^{x pb (Mg 1/3 Nb}} 2/3) O 3-y (In 1/2 Nb 1/2) O 3 ( where, x + y = 1), x = 0.5-0.9, y = 0.1
A high dielectric constant porcelain composition characterized by comprising a composition range of 0.5.