JPH04220905A - Manufacture of sintered body for high frequency dielectric substance - Google Patents

Abstract

PURPOSE:To provide a sintered body for high frequency dielectric substance having excellent dielectric characteristic and high density easily at a low cost by adding B-oxide to a provisionally baked object expressed by AB1/3C2/3O3, and subjecting the resultant to a baking process. CONSTITUTION:To obtain a BMT sintered body for perovskite type high frequency dielectric substance expressed by AB1/3C2/3O3, first the powders of BaCO3, MgO, and Ta2O5 as starting material are measured and subjected to preliminary baking at 1100 deg.C. Then the powders are cooled, crushed in pure water, dried, and subjected to two runs of provisional baking at 1300 deg.C. A powder of MgO is added to this provisionally baked object, and the resultant is subjected to pressure molding into a specified shape, a baking process at 1600 deg.C, and further a heat treatment at 1450 deg.C. Therein the B-oxide added in the regular baking process exerts a sintering promoting effect for the provisionally baked object, so as to accomplish a dense sintered substance with no cracks. Thus a sintered substance equipped with excellent dielectric characteristics is obtained easily and at a low cost.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a sintered body for high frequency dielectrics.

0002

[Prior Art] Conventionally, Ba
Mg1/3 Ta2/3 O3 (=Ba3 MgTa
There is a perovskite-type sintered body for high-frequency dielectrics (hereinafter appropriately referred to as "BMT sintered body") represented by 2O9).

[0003] This sintered body for high-frequency dielectrics is obtained by calcining a calcined material obtained by calcining a raw material mixture, and then subjecting it to main firing and sintering. However, it is generally said that it is difficult to obtain a sintered body with good dielectric properties at a high yield of BMT sintered bodies. This is because the density of the obtained sintered body is often low or cracks are present in the sintered body.

[0004] In order to increase the density, a method has been proposed in which the temperature increase rate in the main firing is rapidly increased to 100°C/min. , resonators), making them unsuitable for mass production and of low practicality.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to provide a method for easily producing an inexpensive sintered body for high-frequency dielectrics having excellent dielectric properties.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the inventors studied BMT sintered bodies from various aspects and found the following. That is, 100
A sintered body obtained by using calcined powder calcined at about 0 to 1100°C does not have sufficient dielectric properties because of cracks, but it has sufficient density. Cracks occur because of BaCO3 and Mg that remain unreacted in the calcined product.
It was thought that this is because O and BaTa2O6 re-react during the firing process. On the other hand, it has been found that a sintered body obtained by firing a powder calcined at about 1300 to 1400° C. has no cracks but is poor in density. Therefore, as a result of a detailed study of the causes of poor density, we found that when the calcination temperature is 1300 to 1400°C, the reaction has progressed sufficiently and almost no MgO remains;
They surmised that this is because MgO remains when the temperature is between 1100°C and 1100°C. Based on this inference, 130
BaMg1/3T fully fired at a temperature above 0℃
It is estimated that if a small amount of MgO is actively added to the hard-to-sinter calcined material represented by a2/3 O3, it may be possible to suppress the occurrence of cracks and create a highly dense sintered material. However, as a result of confirming the correctness of this assumption through experiments, we were able to complete this invention.

Therefore, the method for manufacturing a sintered body for a dielectric according to the present invention is to obtain a sintered body for a perovskite-type high-frequency dielectric body represented by AB1/3 C2/3 O3. The B oxide is added to the calcined product represented by . In this invention, A, B, and C of the calcined product and B oxide represented by AB1/3 C2/3 O3 are appropriately selected and combined from the following A, B, and C.

A; Ba, Sr, Ba1-x Srx (
However, 0 < The B oxide is MgO.

[0009] The amount of B oxide added to the calcined product is usually 3 to 8 with respect to 1 mol of the calcined product.
mol %, more preferably in the range of 4 to 6 mol %. This is because if the content is less than 3 mol%, the effect of increasing density tends to be insufficient, and if it exceeds 8 mol%, it becomes difficult to obtain a sintered body with sufficient dielectric properties and densification. In addition to the above-mentioned BMT, the combination of the calcined material and the oxide added to obtain the perovskite-type sintered body for high-frequency dielectrics may include the following. (a) Calcined product; BaZn1/3 Ta2/3 O3 oxide; ZnO (b) Calcined product; BaNi1/3 Ta2/3 O3 oxide; NiO (c) Calcined product; BaMn1/3 Ta2/3 O3 oxide; MnO (d) Calcined product; BaMg1/3 Nb2/3 O3 oxide; MgO (e) Calcined product; BaZn1/3 Nb2/3 O3 oxide; ZnO (f) Calcined product; BaMn1/3 Nb2/3 O3 oxide ;MnO (g) Calcined product; SrMg1/3 Ta2/3 O3 oxide; MgO (h) Calcined product; SrZn1/3 Ta2/3 O3 oxide; ZnO (i) Calcined product; SrNi1/3 Ta2/3 O3 oxide material; NiO (j) calcined material; Ba1-x Srx Mg1/3 Ta
2/3 O3 oxide; MgO (k) calcined product; Ba1-x Srx Ni1/3 Ta
2/3 O3 oxide; NiO Hereinafter, this invention will be described using the case of a BMT sintered body as an example.
I will explain in detail.

■BaMg1/3 Ta2/3 O3
According to the stoichiometric ratio of starting materials BaCO3, Mg
Weigh the O and Ta2O5 powders respectively. Usually, the average particle size of each powder is of the following order. BaCO3 powder…1 ~15μm MgO powder…1
Ta2 O5 powder...approximately 1 to 15 μm BaO may be used instead of BaCO3, but BaCO3 with high purity and uniform particle size can be obtained at low cost.

(2) Preliminary calcination is performed at a temperature of 1000 to 1100°C. Preliminary calcination is used to remove Mg during subsequent calcination and main firing.
This is to prevent O from volatilizing. However, this preliminary calcination may be omitted. ■ After pre-calcining, the powder is cooled and soaked in pure water for 24 hours.
Grind with a ball mill for about an hour, dry, and then
Calcinate at a temperature of 300-1400°C for 2-10 hours. This calcination is preferably performed two or more times. By repeating calcination, the uniformity of the composition increases. Furthermore, the calcined material is crushed and stirred every time it is calcined. This calcined product is represented by BaMg1/3 Ta2/3O3. The average particle size of the powder obtained by pulverization after the final calcination treatment is about 1 to 15 μm.

The reaction in the calcination step is as follows.

[Chemical formula 1] ■ MgO per 1 mol of the obtained calcined powder
α mol % of powder (however, in the range of 0<α≦8) is added, and a green compact of a predetermined shape is formed by pressure molding. M to add
The average particle size of the gO powder is about 1 to 15 μm.

[0013] MgO is usually used alone, but other oxides such as BaTa2 O6 may also be included. In this way, it is only necessary to add a small amount of MgO, which is one of the raw materials, to the product calcined at a temperature of 1300° C. or higher, so it can be produced extremely easily and at low cost. The calcination temperature is preferably 1300°C or higher. This is because the reaction between the raw materials progresses sufficiently and it is possible to prevent unreacted raw materials from remaining in the calcined product, which inhibits densification. In particular, the diffraction line (10.2
), (20・2), (21・2), (20・4), and (21・4) have half widths of 0.20° and 0.20°, respectively.
Those calcined to angles of 22°, 0.29°, 0.33°, and 0.36° or less tend to have high compositional uniformity and a sufficient Q value.

[0014] After this, main firing is performed. (1) Baking at a temperature of 1500°C or higher for 2 to 5 hours. There is no particular restriction on the heating rate. This firing (1) is for advancing densification. Next, (2)
Heat treatment is performed at 1200 to 1450°C for 10 to 120 hours. This treatment (2) is performed to make the BMT crystal into an ideal hexagonal crystal.

[0015] This makes it possible to easily obtain an excellent BMT sintered body.

[0016]

[Function] In this invention, the B oxide added in the main firing has the effect of promoting sintering of the calcined material represented by AB1/3C2/3 O3, so that a dense sintered body without cracks is produced. It can be obtained reliably (with high yield). B oxide, which is added in small amounts, is usually a raw material for making calcined products and is not special, and there is no need for special treatment such as rapid heating firing, so manufacturing is easy and low cost. There is no such thing as inducing high school.

When the perovskite-type sintered body for high-frequency dielectric material is represented by BaMg1/3 Ta2/3 O3, it is easier to obtain one with excellent dielectric properties compared to the case of other compositions. The amount of B oxide added is AB1
1 mol of calcined material expressed as /3 C2/3 O3
When the amount is 3 to 8 mol %, an appropriate sintering promotion effect is reliably exhibited.

[0018]

[Embodiments] Examples of the present invention will be described below. -Examples 1 to 5- BMT sintered bodies were obtained according to the above-mentioned procedures. However, the addition ratio of MgO to 1 mol of calcined material was as shown in Table 1.

[0019] In addition, in the preliminary calcination step (1), the temperature is 1100°C,
Treatment was carried out for 10 hours, and in the calcination step, the temperature was 1300℃
The 10-hour treatment was performed twice, and the (1) firing step of (1) main firing was performed at 1600° C. for 2 hours, and the (2) firing step was performed at 1450° C. for 100 hours. The average particle size of the raw material powder is approximately 4 μm for BaCO3 powder,
MgO powder is about 4μm, Ta2O5 powder is about 4μm
It is.

The average particle size of the calcined powder after pulverization is about 4 μm, and the average particle size of the MgO powder added is also about 4 μm.
It is μm. - Comparative Example 1 - A BMT sintered body was obtained in the same manner as in Example 1, except that MgO was not added.

-Comparative Example 2- A BMT sintered body was obtained in the same manner as in Comparative Example 1 except that the calcination temperature was 1100°C. Regarding the sintered bodies of Examples and Comparative Examples, the compactness (relative density of the sintered bodies) was measured, and the dielectric constant and Q value were also measured by the dielectric cylinder resonance method (measurement frequency: 10 GHz). The presence or absence of cracks was also investigated. The measurement results are shown in Table 1.

[0022]

[Table 1]

Comparing the sintered bodies of the examples in Table 1 and the sintered bodies of Comparative Examples 1 and 2, the sintered bodies of the examples are dense, have no cracks, and have dielectric properties sufficient for practical use. It can be seen that it is a dielectric material with .

[0024]

Effects of the Invention As described above, in the invention according to claims 1 to 3, it is sufficient to add a small amount of B oxide having a sintering promoting effect to the calcined material represented by AB1/3 C2/3 O3. Therefore, an inexpensive sintered body with excellent high-frequency dielectric properties can be easily obtained. In the invention as claimed in claim 2, since the composition of the perovskite-type sintered body for high-frequency dielectric is BaMg1/3 Ta2/3 O3, the dielectric properties are significantly excellent and the practicality is higher.

In the third aspect of the invention, since the amount of B oxide added is 3 to 8 mol %, an appropriate sintering promoting effect is reliably exerted.

Claims (3)

[Claims] [Claim 1] To obtain a perovskite-type sintered body for high-frequency dielectrics represented by AB1/3 C2/3 O3, B oxide is added to a calcined material represented by AB1/3 C2/3 O3 and fired. A method of manufacturing a sintered body for high frequency dielectric material, characterized in that: [Claim 2] The calcined product is BaMg1/3 Ta2/3
O3, and the added oxide is Mg
2. The method for producing a sintered body for high frequency dielectric material according to claim 1, wherein the sintered body is O. [Claim 3] 3 to 8 mo of B oxide per 1 mol of calcined material expressed as AB1/3 C2/3 O3
3. The method for producing a sintered body for high frequency dielectric material according to claim 1 or 2, wherein the addition amount is 1%.