JPS6121966A - Low temperature sintering method for dielectric ceramic composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method capable of lowering the sintering temperature of barium titanate-based dielectric material used for microphone limb filters, etc. The present invention relates to a low-temperature sintering method in which a barium titanate-based dielectric material containing niobium is pre-sintered, an appropriate amount of silicic acid powder is added, and then main firing is performed.

[Prior Art] In recent years, dielectric ceramics have been widely used as resonators and filters in microwave areas such as automobile radio and satellite communications. Dielectric porcelain used in such applications is
It is important that the material has a high dielectric constant, low loss, and good stability. Barium titanate-based dielectric materials, which have been commonly used in the past, are known to have a high dielectric constant, low loss, and a relatively small resonant frequency temperature coefficient, and are in practical use.However, due to improvements in circuit technology, etc. When applied to transmitters, etc., even lower loss and higher stability are required, and ordinary barium titanate dielectric materials have insufficient characteristics.

To improve the point B, there is a material having a composition in which an appropriate amount of niobium oxide is added to a barium titanate-based material.

With such a composition, the characteristics of the usual barium titanate dielectric material can be further improved, and lower loss and higher stability can be realized.

[Problems to be Solved by the Invention] However, such barium titanate-based dielectric materials usually require about 14
It is necessary to bake at a high temperature of 00°C or higher. However, firing at such high temperatures not only increases the amount of power used in the electric furnace, but also causes significant wear and tear on the heating element and the furnace body, leading to an increase in firing costs.

The purpose of the present invention is to solve the problems of the prior art as described above, and to provide a method that can lower the sintering temperature without impairing the properties as a microwave dielectric material. be.

[Means for solving the problems] The present invention, which can solve the above problems,
Barium oxide 15-25 mol% and titanium oxide 75-85%
The main component is mol%, and 0.1 to 07% by weight of niobium oxide.
After pre-sintering the dielectric material containing the composition, approximately 500 or less silicic acid powder is added to the dielectric material with a composition of 001 to 005.
This is a low-temperature sintering method for a dielectric ceramic composition, which is characterized by adding and mixing in weight percent and performing main firing.

What is important here is not to add the silicic acid powder at the stage of weighing the raw material powder, but to add the silicic acid powder at the step after pre-calcination. Furthermore, it is preferable that the silicic acid powder be added in the form of as fine a particle size as possible (approximately 500 particles or less) so that it can be mixed uniformly.

[Function] With this configuration, barium titanate-based dielectric porcelain materials, which conventionally required firing at a high temperature of about 1400°C or higher to develop sufficient properties, can be fired at a relatively low temperature of about 1300°C. It becomes possible to perform sintering without impairing electrical properties in the microwave region. Even if the sintering temperature is reduced by several tens to hundreds of degrees Celsius, it will have an extremely significant overall cost reduction effect, considering the amount of electricity used in the electric furnace and the wear and tear on the electric furnace main body and heating element. It is brought about.

[Specific structure of the invention] The present invention will be explained in more detail below.

As described above, the present invention is a method that can significantly reduce the sintering temperature when sintering a barium titanate dielectric material. The dielectric material used in the present invention is barium oxide (
Bad) 15-25 mol% and titanium oxide (Tie, ) 7
The main component is a material with a composition ratio of 5 to 85 mol%, and 01 to 07% by weight of niobium oxide (Nb205).
It is of the composition added. The above composition ratios for barium oxide and titanium oxide are within the composition range commonly used as dielectric materials in the microwave region, and therefore explanations regarding this composition range will be omitted. However, as mentioned above, barium oxide and titanium oxide alone cannot exhibit sufficient electrical characteristics, so niobium oxide is added. The addition range of niobium oxide is 01 to 0.7% by weight based on the above-mentioned main components.

Addition of niobium oxide will result in even lower losses and higher stability.

Such a dielectric material can basically be manufactured by a conventional powder molding method.

That is, each component of the material is weighed in a predetermined amount, thoroughly mixed, and pre-fired. Here, the present invention is significantly different from the prior art in that 0.01 to 0.05% by weight of silicic acid powder is added after pre-calcination. The pre-fired powder obtained by adding silicic acid powder and pulverizing and mixing is granulated by adding an organic binder and the like, pressure-molded into a predetermined shape, and then main firing is performed.

By adding silicic acid powder, the sintering temperature in the main firing can be significantly reduced. The reason for limiting the addition range to 0.01 to 0.05% by weight is that if it is less than 0.01% by weight, there will not be much effect of reducing the firing temperature;
This is because if the amount exceeds 5% by weight, the electrical properties of the resulting dielectric material will deteriorate considerably. Moreover, one major feature of the present invention is that silicic acid powder is added after pre-calcination. If silicic acid powder is mixed in advance, that is, before calcining, experimental results show that unless it is mixed in at least 0.1% by weight, there will be no effect of reducing the sintering temperature, and if it is mixed in such a large amount, the electrical properties will be affected. This is because Q, which is one of the factors, decreases significantly. Further, when adding silicic acid powder, it is preferable to use one having a particle size of about 500 particles or less. If the particle size is large, mix it evenly.
This is because the sintered body tends to become non-uniform.

[Examples] Hereinafter, examples of the present invention will be described while comparing them with those outside the scope of the present invention. Bad.

Each raw material of TlO2 and Nb2O5 was weighed so as to have a predetermined composition, wet-mixed using a ball mill, etc., and then dried and pre-calcined at 1000°C for 6 hours. Silicic acid powder was added to this in a range of 0 (no additive) to 01% by weight, pulverized, dried, and then granulated by adding a binder such as polyvinyl alcohol, and molded at a pressure of 300 kg/at. . After firing the molded product B for 3 hours at a temperature of 1270 to 1360°C, the molded product had a diameter of 11 mmφ and a thickness of 5III11.
It was processed into a cylinder and used as a measurement sample. Then, Q and dielectric constant ε were measured using a dielectric resonance method. The measurement frequency is 6.
It is 5GHz. The relationship between Q and dielectric constant with respect to the firing temperature and the amount of silicic acid added is shown in the following table.

Table As is clear from this table, the sintering temperature can be lowered by adding silicic acid powder.

In particular, materials added with 1,001% by weight of silicic acid powder and fired at 1,330°C have excellent properties that are comparable to those of dielectric materials that could previously only be obtained by firing at a high temperature of 1,400°C or higher. It was dielectric porcelain for microwave use. In addition, in the case of conventional methods that do not add silicic acid powder, even those that did not sinter at temperatures below 1330°C can be sintered by adding silicic acid powder, and have good electrical properties. The expression B was created.

[Effects of the Invention] The present invention is a low-temperature sintering method for a barium titanate-based dielectric ceramic composition configured as described above.
Materials that could only be sintered at high temperatures above 0°C were made into 133
It can be sintered at a relatively low temperature of around 0°C to produce approximately the same or better properties, and therefore not only can it significantly reduce the amount of electricity used in the electric furnace used for firing. This has the excellent effect of reducing wear and tear on the heating element and the electric furnace main body, and significantly reducing manufacturing costs as a whole.

Claims (1)

[Claims] 1. Barium oxide 15~25 mol% and titanium oxide 75~
The main component is 85 mol%, and 0.1 to 0.7 niobium oxide.
After pre-sintering the dielectric material having a composition containing 0.01% by weight of silicic acid powder of about 500 Å or less,
A low-temperature sintering method for a dielectric ceramic composition, characterized by adding and mixing ~0.05% by weight and performing main firing.