JPS5910951B2 - Raw material composition for manufacturing high dielectric constant porcelain - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a raw material composition for producing high dielectric constant porcelain, which can maintain a particularly high dielectric constant and improve dielectric loss, while significantly expanding the porcelain firing temperature range. The present invention provides a raw material composition for producing dielectric ceramics.

Conventionally, dielectric ceramics have been used as ceramic capacitors, for example, for extinguishing sparks in current circuit breakers, and also in voltage doubler rectifier circuits for TV receivers, oscilloscopes, and the like.

Dielectric ceramics used as ceramic capacitors and the like used in such applications generally have barium titanate or a mixture capable of producing barium titanate as a main component, with shifters, mineralizers, etc. added as necessary. It is obtained by firing a raw material composition at a predetermined temperature to form porcelain, but the firing temperature in this case has a great influence on the properties of the resulting porcelain.

By the way, the appropriate firing temperature range of the raw material composition for producing the conventional barium titanate-based porcelain as described above is usually 13
It is necessary to control the temperature around 40°C within a narrow range of 20 to 40°C. However, in order to control firing within a narrow temperature range of about 20 to 40 degrees Celsius at such high temperatures, the influence of the structure of the firing furnace, the shape of the sagger, the posture of the fired product within the sagger, etc. These factors appear in subtle ways, and it is therefore necessary to control all of these factors, which brings about many difficulties in the firing process.

The present invention has been developed against the background of the above, and is characterized by containing barium titanate or a mixture capable of producing barium titanate as a main component, and optionally using a shifter. In the raw material composition for producing dielectric ceramics containing auxiliary components such as 0.
The reason is that 1 to 10% by weight of zinc niobate or a mixture capable of producing zinc niobate is blended, and the electrical properties of the resulting porcelain are improved or equivalent to those of conventional ones. In other words, the dielectric constant is further improved, the dielectric loss is improved, and the temperature change rate of the dielectric constant is suppressed from decreasing, while the porcelain firing temperature range of the raw material composition ( This made it possible to significantly expand the porcelain firing temperature range. That is, according to the present invention, the raw material composition according to the present invention can be fired in the range of about 1250°C to 1450°C. Previously, the firing temperature range was only about 200°C, but now it is possible to use porcelain firing conditions within a temperature range of 200°C or wider. There is no need to strictly control the shape of the pot, etc.
This made the firing process much easier.

The raw material composition according to the present invention provides a barium titanate-based ceramic capacitor, and therefore the barium titanate component is replaced with barium titanate (BaTl).
O3) itself or in the course of calcination can produce barium titanate, e.g. barium carbonate (BaCO
3) and titanium oxide (TiO2), which is contained as a main component (generally 50 mol% or more).

In addition, such raw material compositions may include auxiliary ingredients, if necessary.
For example, a shifter that changes the temperature coefficient of the dielectric constant to a desired value, a mineralizing agent that improves the sinterability of porcelain, and other property improvers (electrical properties, etc.) are blended. It will be done. This shifter includes tin, zirconium, strontium, magnesium,
One or more oxides of calcium, lead, bismuth, etc. or their salts are preferably used in a desired blending ratio. Additionally, known mineralizers and other property improvers can be used as appropriate in desired amounts. In addition, according to the present invention, a raw material composition (compound) containing such barium titanate component and, if necessary, auxiliary components such as the above-mentioned shifter, further contains 0.1 to 10% by weight of a zinc niobate component. is a mixture in which zinc niobate (Zn3Nb2O8) can be produced as a solid solution) itself or in the course of calcination,
For example, zinc oxide (ZnO) and niobium oxide (Nb2O5)
It is blended as a mixture with In particular, by blending the zinc niobate component in such a proportion, it becomes possible to achieve the object of the present invention for the first time, and if the blending amount is too small, the effect of adding the zinc niobate component cannot be sufficiently exhibited. Furthermore, if the zinc niobate component is present in the composition in a proportion exceeding 10% by weight, it will have an adverse effect on the dielectric constant and other performance of the ceramic obtained by firing, and the properties required for a ceramic capacitor will be adversely affected. O, which must be avoided because it reduces the This allows for advantageous porcelain firing in a wide range of firing areas, which not only facilitates the firing operation, but also increases the dielectric constant of the porcelain obtained by firing, and significantly improves dielectric loss. This provides excellent effects such as:

In order to clarify the present invention that has been explained above more specifically, Examples are shown below, but it goes without saying that the present invention {1] is not in any way restricted by the description of such Examples. .

Example barium titanate components include BacO3 and TlO2
: ZnO and Nb2O as zinc niobate components: ZrO2 as a shifter; MncO3 as a mineralizer were weighed out and wet mixed in a ball mill at the blending ratio shown in Table 1. A chemical reaction is carried out by calcining for 3 hours at a low temperature (BaT
(formation of iO3, Zn3Nb2O8) Then, this calcined product was again put into a ball mill and pulverized until the average particle size was about 1 micron.

Next, after drying the calcined and pulverized mixture thus obtained, an appropriate amount of polyvinyl alcohol (PVA) was added as a binder, and the mixture was molded under a molding pressure of about 1 ton/d to a diameter of 16 m/k thickness. A large number of disc-shaped molded products with a diameter of 0.5 m/m were produced.

Then, using this disk-shaped molded product, 1200 to 1500
The moldings were main fired at various temperatures in the temperature range of 0.degree. C. for 3 hours each. After observing the degree of porcelainization of the fired product obtained by this main firing,
Among them, those that were porcelain but not fused were made into samples by baking silver electrodes on both sides, and the electrical properties of each were measured and the results are shown in Table 2. On the other hand, using the same procedure as the above experiment, a conventional barium titanate-based raw material composition having the blending ratio shown in Table 3 below was prepared.
Wet mixing, calcination, crushing, molding, 1300-1400'C
Similarly, regarding the fired products that were made into porcelain (not fused) after main firing at various temperatures,
Silver electrodes were baked and the electrical characteristics of each were measured and the results are shown in Table 4.

*As is clear from comparing the results in Table 2 (invention) and Table 4 (conventional examples), by distributing the Zn3Nb2O8 component in the porcelain raw material composition according to the present invention, the firing The possible temperature is about 1330
~1370°C to 1250°C as shown in Figure 2
The temperature range has increased significantly to about 1450°C, and the temperature range has now exceeded 200°C.

Claims (1)

[Claims] 1. In a raw material composition for producing dielectric porcelain containing barium titanate or a mixture capable of producing barium titanate as a main component, and optionally containing auxiliary components such as a shifter, 0.1 to 10% by weight of niobic acid is further added. A raw material composition for producing high dielectric constant porcelain, characterized in that it contains a mixture capable of producing zinc or zinc niobate.