JPS6341866B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a temperature-compensating dielectric ceramic composition composed of a Pb ₂ Nb ₂ O ₇ -Bi ₂ O ₃ .2TiO ₂ system. [Prior Art] and [Problems to be Solved by the Invention] Conventionally, temperature-compensating dielectric ceramic compositions include SrTiO ₃ , CaTiO ₃ , MgTiO ₃ , La ₂ O ₃ .2TiO ₂
It is known that the main component is a TiO ₂ -based composition such as . However, products containing these compositions as main ingredients have a high firing temperature of 1300 to 1400°C, a temperature coefficient of dielectric constant T・C in the range of -650 ppm/°C to -1200 ppm/°C, and a dielectric constant of 120 to 1400°C. 150th place is common,
The biggest drawback of the above composition is that the relationship between the dielectric constant and the temperature coefficient at room temperature is that the larger the dielectric constant, the larger the temperature coefficient, and the smaller the temperature coefficient, the smaller the dielectric constant. Ta. On the other hand, the recent demand for ultra-small, large-capacity capacitors is expanding not only to general use but also to the application field of the communication industry, and smaller capacitors and larger capacitances are required than ever before. In order to meet these demands, methods have been put into practical use in which the thickness of dielectric ceramic is reduced to 0.1 to 0.2 mm, and multilayer ceramic capacitors in which multiple layers are formed with a film thickness of about 50 μm. However, it has been difficult to reduce the thickness of porcelain using the above-mentioned conventional dielectric compositions. In other words, the firing temperature is as high as 1,300 to 1,400°C, which not only causes deformation of the element and a decrease in manufacturing yield, but also requires a large amount of thermal energy during sintering, which reduces the thermal efficiency of the firing furnace material. There were drawbacks such as severe deterioration losses and increased maintenance costs for the firing equipment. Furthermore, in the case of multilayer porcelain capacitors, which are rapidly becoming popular these days, the manufacturing method requires that the internal electrodes be sintered while being embedded in a porcelain dielectric material, which is different from conventional porcelain dielectric capacitors whose firing temperature exceeds 1000°C. In the body,
Although stable at high temperatures of 1300°C or higher, expensive precious metals such as platinum, palladium, or alloys thereof had to be used. Therefore, if 1000
If it is possible to use a ceramic dielectric material that can be sintered at low temperatures below ℃ as a multilayer ceramic capacitor, inexpensive metal materials such as silver, nickel, and aluminum can be used for the embedded internal electrodes. This is extremely advantageous in terms of manufacturing costs. Of course, the porcelain dielectric obtained by low-temperature sintering is required to have high insulation resistance, relatively large dielectric constant, small dielectric loss, and excellent temperature change rate. However, until now, there have been few stable ceramic dielectric materials that meet these conditions and are produced by low-temperature sintering, and the realization of such materials has been desired. [Means for Solving the Problems] In view of the above-mentioned requirements, the present inventors have conducted intensive research and have developed a ceramic composition composed of the Pb ₂ Nb ₂ O ₇ -Bi ₂ O ₃ .2TiO ₂ system. In addition, by changing the blending ratio of these two components, low temperature sintering around 1000℃ is possible, the dielectric constant is high, the temperature change rate is linear, and the capacitance temperature characteristics are extremely high. The present invention was developed based on the discovery that an excellent dielectric ceramic composition for temperature compensation can be obtained. That is, the present invention provides Pb ₂ Nb ₂ O ₇ ...40.0 to 99.0 mol
%, Bi ₂ O ₃ .2TiO ₂ ...1.0 to 60.0 mol % of the powder composition for manufacturing dielectric ceramics for temperature compensation. Hereinafter, the present invention will be explained in detail with reference to Examples. [Example] Using lead oxide (PbO), niobium oxide (Nb ₂ O ₅ ), bismuth oxide (Bi ₂ O ₃ ), titanium oxide (TiO ₂ ), and manganese carbonate (MnCO ₃ ) as starting materials,
Intermediate raw materials in the form of Pb ₂ Nb ₂ O ₇ .Bi ₂ O ₃ .2TiO ₂ were prepared in advance and weighed and mixed into the component ratios shown in Table 1. These raw material mixtures were wet mixed in a synthetic resin ball mill and then calcined at 700-850°C for 2 hours to carry out a chemical reaction. This reaction product was pulverized and mixed again using a ball mill to a particle size of approximately several μm. An appropriate amount of polyvinyl alcohol (PVA) was added as a binder to this mixture, and a disc-shaped molded product with a diameter of 16.5 mm and a thickness of 0.6 mm was produced at a molding pressure of about 3 tons/cm ² . This molded product is sealed in a magnesia porcelain container to prevent the lead component from evaporating at high temperatures.
Main firing was performed at 930-1050°C for 2 hours. Silver electrodes were baked at 780°C on both end faces of the porcelain body thus obtained. The results of measuring the electrical characteristics of each of the samples thus manufactured are shown in Table 1, FIG. 1, and FIG. 2. Here, the dielectric constant ε _s and dielectric loss (tan δ) are
Measured at a frequency of 1KHz. The capacitance was measured based on a room temperature of 20° C., and the Q value was measured using a Q meter manufactured by YEW (Model No. 4043A). Regarding the capacitance temperature coefficient, the capacitance bridge manufactured by Bunton (Model No. 74D) and the capacitance bridge manufactured by Electop (Model No. EW-102) are used.
A constant temperature bath was used. FIG. 1 shows the relationship between the composition ratio of Pb ₂ Nb ₂ O ₇ and Bi ₂ O ₃ .2TiO ₃ and the firing temperature and dielectric constant of the ceramic composition. FIG. 2 similarly shows the relationship between the composition ratio, Q value, and capacitance temperature coefficient.

【table】

〔Effect of the invention〕

As described above, the Pb ₂ Nb ₂ O ₇ ―Bi ₂ O ₃・
According to the 2TiO ₂ -based dielectric ceramic composition for temperature compensation, the capacitance temperature coefficient is approximately -650×10 ^-6 /℃ ~ 1200×
The dielectric constant improves to approximately 160 to 180 in the range of 10 ^-6 /℃,
Moreover, since low-temperature sintering of 930 to 1050°C has become possible, when used in a multilayer ceramic capacitor, it has become possible to use low-melting point metals such as silver alloys for the internal electrodes. Therefore, compared to conventional high-temperature sintered materials, it consumes less thermal energy, has a significant effect on reducing maintenance costs for firing furnace materials, etc., and is extremely cost-effective from an energy-saving perspective. Since a dielectric ceramic composition for temperature compensation can be provided, there are great industrial benefits.

[Brief explanation of the drawing]

Figure 1 shows the porcelain composition according to the present invention.
This is a graph showing the relationship between the composition ratio of Pb ₂ Nb ₂ O ₇ and Bi ₂ O ₂ 2TiO ₂ and the firing temperature and dielectric constant of the ceramic composition. It is a graph showing the relationship between capacitance and temperature relationship coefficient.

Claims (1)

[Claims] 1. A dielectric material for temperature compensation characterized by having a composition in the range of 1 Pb ₂ Nb ₂ O ₇ ...40.0 to 99.0 mol% Bi ₂ O ₃ 2TiO ₂ ...1.0 to 60.0 mol% Powder composition for porcelain production. 2 For the above composition, MnCO ₃ was added as an oxidizing agent to prevent reduction during firing, and La, Ce, and Sb were added as mineralizing agents.
2. A powder composition for producing temperature-compensating dielectric ceramics according to claim 1, which additionally contains an oxide such as oxide.