JPH0353267B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a composite perovskite compound containing Pb (Mg _1/4 Fe _1/4 W _1/2 ) O ₃ and Pb (Mg _1/3
This relates to a ceramic composition whose main component is Nb _2/3 ) O ₃ , and its purpose is to have a high dielectric constant, low dielectric loss, high insulation resistance, and
The object of the present invention is to provide a high dielectric constant ceramic composition that can be sintered at a low temperature of 1000°C or lower. Conventionally, the main component of high-permittivity porcelain is barium titanate BaTiO ₃ , in addition to calcium zirconate CaZrO ₃ and calcium titanate.
Products with improved properties by adding appropriate amounts of CaTiO ₃ , calcium stannate CaSnO ₃ , strontium titanate SrTiO ₃ , etc. have been put into practical use. The sintering temperature of these porcelains was as high as approximately 1300°C to 1400°C. In recent years, with the development of the electronic equipment field, electronic equipment has become significantly smaller and lighter.In order to achieve large capacitance in a smaller size, the ceramic capacitors that were conventionally used in the form of disks have been replaced with multilayer ceramic capacitors that have a laminated structure to achieve large capacitance in a small size. has been developed and widely used. As shown in the drawing, a multilayer ceramic capacitor has a structure in which internal electrodes 2 are arranged above and below a ceramic dielectric 1, and many small single-plate capacitors are connected in parallel and stacked one on top of the other.
are alternately connected to either the left or right external electrode 3. In order to manufacture this multilayer ceramic capacitor, it is necessary to sinter the internal electrodes while embedding them in the ceramic dielectric, but as mentioned above, the firing temperature for conventional high dielectric constant ceramic compositions is 1300°C or higher. As a result, the internal electrodes had to be made of platinum, which is stable even at such high temperatures, or expensive noble metals such as palladium. accordingly
If we can develop a porcelain dielectric material that can be sintered at low temperatures below 1000°C and use it in multilayer ceramic capacitors, it will be possible to use inexpensive metal materials such as silver-based alloys and nickel-based alloys as internal electrode materials. This makes it possible to supply low-cost multilayer ceramic capacitors. Based on the above _- mentioned background, _the present invention _was developed as a result of repeated research on _various composite perovskite compounds. By using the compound represented by Mg _1/3 Nb _2/3 ) O ₃ , we are developing a porcelain dielectric material that has a high dielectric constant, low dielectric loss, high insulation resistance, and can be sintered at low temperatures. It was a success. Examples of the present invention will be described in detail below. First, Pb (Mg _1/4 Fe _1/4 W _1/2 ) O ₃ and Pb are sintered.
Weigh appropriate amounts of lead oxide, iron oxide, tungsten oxide, magnesium oxide, and niobium oxide so that the molar ratio of (Mg _1/3 Nb _2/3 ) O ₃ is as shown in the table below, and then mill them using a ball mill. Mixed. This powder raw material
After calcining at 750° C. to 850° C., the material was pulverized again using a ball mill, and polyvinyl alcohol was added to the pulverized raw material to granulate it into a disk shape with a diameter of 13 mm and a thickness of 0.8 mm. After that, it was fired in a magnesium pot at a temperature of 920°C to 980°C, and electrodes containing silver as a main component were applied to both sides to prepare a dielectric sample. The results of measuring the electrical properties of the samples thus prepared are shown in the following table. Here, the dielectric constant ε _S and the dielectric loss tan δ were measured at 25° C. at a frequency of 1 kHz. Insulation resistance IR was measured at room temperature by applying 50 V DC. Note that the firing temperature in the table is the lowest temperature for sintering to create dielectric ceramic.

[Table] * Comparative Example Samples No. 1 and 6 in the table are outside the scope of the present invention and are shown for comparison. That is, Pb
(Mg _1/4 Fe _1/4 W _1/2 ) When the molar ratio x of O ₃ exceeds 0.90, the dielectric loss tan δ becomes large and impractical;
If it is less than 0.65, the firing temperature will be high and the proportion of expensive niobium oxide will be large, which is not practical. As detailed above, Pb (Mg _1/4 Fe _1/4
If a W _1/2 ) O ₃ −Pb (Mg _1/3 Nb _2/3 ) O ₃ based ceramic composition is used, the dielectric constant ε _S will be as high as 3510 to 4850, and the dielectric loss tan δ will be as small as 0.7 to 26%. , and the insulation resistance IR is
A new high-performance dielectric ceramic composition exhibiting a high value of 5.1×10 ¹⁰ Ω·cm and a small rate of change in capacitance due to temperature can be obtained. Furthermore, since the firing temperature is as low as 920°C to 980°C, inexpensive metals such as silver-based alloys and nickel-based alloys can be used as internal electrodes when used in multilayer ceramic capacitors. This has a very effective value in reducing costs. In addition, since sintering can be performed at low temperatures, it is not only easier to maintain the electric furnace used for firing, but also energy saving can be achieved in terms of power consumption.
Therefore, it is advantageous in terms of manufacturing costs when applied not only to laminated ceramic capacitors but also to conventional disk-shaped ceramic capacitors.

[Brief explanation of drawings]

The drawing is a partially cutaway perspective view showing an example of a laminated ceramic capacitor. 1...Porcelain dielectric, 2...Internal electrode, 3...External electrode.

Claims (1)

[Claims] 1 Magnesium, iron, lead tungstate Pb
A binary composition consisting of (Mg _1/4 Fe _1/4 W _1/2 ) O ₃ and magnesium lead niobate Pb (Mg _1/3 Nb _2/3 ) O ₃
When expressed as Pb (Mg _1/4 Fe _1/4 W _1/2 ) x (Mg _1/3 Nb _2/3 ) _1-x O ₃ , the composition ratio x must be within the range of 0.65≦x≦0.90. A porcelain composition characterized by.