JPS61181008A - Manufacture of dielectric ceramics - 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 for manufacturing dielectric ceramics, and particularly to a method for manufacturing dielectric ceramics suitable for high frequency use with high no-load Q and low loss.

[Prior art] Generally, it is desirable to use dielectric ceramics that can accommodate a high no-load Q for dielectric resonators and dielectric substrates used in signal circuits in high frequency ranges such as microwaves and millimeter waves. .

By the way, in recent years, the frequency used for communication has rapidly increased, and satellite broadcasting using the SHF band is entering the stage of practical use, so the development of low-loss dielectric ceramics with even higher no-load Q is required. It is strongly required.

The no-load Q of the materials conventionally used as low-loss dielectric porcelain for high frequencies is approximately 3000 to 7000.
Only in recent years have products exceeding this value been manufactured.

In Bao-MgO-Ta2O5-based dielectric ceramic,
Conventionally known Bao-
MgO-Ta2O5-based porcelain has a low no-load Q of about 4.000 (Japanese Unexamined Patent Publication No. 53-60544), and even BaO-MgO-Ta2O5-based porcelain containing other additive elements
The unloaded Q is, for example, 3Bass
Porcelain with a composition of a2O5 is 4360, published in JP-A-54-714.
3BaO-xMgO-(1-7)N disclosed in Publication No. 00
b2Os ・yTm2Oes (1) Mn formation (7) m
Due to the low strength of 4090 mm, these porcelains are not suitable as materials for SHF band communications.

In order to increase the no-load Q of B ao-MgO-Ta2O5 based porcelain, B a (Mgx73T a2/3)
A method was proposed in which a small amount of Mn was added to a perovskite structure oxide mainly composed of 03 and sintered (Japanese Unexamined Patent Application Publication No. 1983-1999).
2O6003), this method certainly yields dielectric porcelain with a high unloaded Q, but adding a different element such as Mn not only complicates the manufacturing process, but also In addition, there is a risk that unnecessary impurities may be mixed in that have a negative effect on the porcelain properties, and furthermore, in terms of product quality control, special attention is required to control the amount of additives and uniform distribution of additives. However, this method is not suitable for mass production.

By the way, conventionally, Bao-MgO-Ta2O5-based dielectric porcelain has been manufactured using a normal firing method.

That is, about 100 press-molded products having a predetermined composition are
This is done by firing at a temperature of 0 to 1,500 degrees Celsius, but in this case, the process of raising the temperature to the firing temperature is not particularly important, and for fear that the porcelain will be damaged by rapid heating,
The temperature of the furnace containing the press-molded product was gradually raised from room temperature to the desired temperature. As a result, heating was typically carried out at a rate of approximately 2-b. This conventional firing method itself has the disadvantage that it requires a long time of several hours for the temperature raising process, which hinders improvement in production efficiency.

The present inventors and others have developed the above-mentioned conventional BaO-MgO-Ta
In order to solve the problems associated with the manufacturing method of 2O5-based porcelain, we first proposed a method in which a pressure-molded product is rapidly heated to a temperature of 1500-1700°C by 100°C and then fired (Japanese Patent Application No. 1983).
-228557), this manufacturing method allows dielectric porcelain with a sufficiently high unloaded Q to be used as an SHF band communication material to be obtained in a short time, and also avoids complicating the manufacturing process because it does not use additive elements such as Mn. However, the degree of firing of each part of each product varies, and the inside of the porcelain tends to shrink more than the outside, resulting in deformation and post-processing such as grinding. In addition, since there are large variations in the degree of firing between products, it is difficult to obtain products with uniform dielectric constant, no-load Q, etc., and these problems reduce the yield of products. tends to be low.

[Problems to be Solved by the Invention] The present invention directly solves the problem by improving the manufacturing method disclosed in Japanese Patent Application No. 59-2.28557, which is the degree of firing for each product and between products. The purpose is to improve uniformity, reduce variations in dielectric properties, and thereby improve product yield.

The production method of the present invention naturally differs from the conventional BaO-MgO-
This is a problem with Ta2O5-based dielectric ceramics. It is also intended to solve problems such as low no-load Q, complicated manufacturing process that makes product quality control difficult, and long manufacturing time.

[Means for Solving the Problems] The present invention solves the above problems by using the general formula:
xBaO@yMgo・zTa2 os 'T', where 0.5≦x≦0.7.0.15≦y≦0.
25, A press-molded article having a composition where 0.15≦z≦0.25 and x+y+z=1 is heated to a temperature of 1500-1700°C in the manufacturing method of 100-b, during heating and firing. Provided is a manufacturing method characterized by wrapping with refractory powder.

As the refractory powder used in the present invention, any powder can be used as long as it does not react with the press-molded product having the above composition at the firing temperature. Examples of such non-reactive refractory powders include ceramic powders such as alumina, zirconia, magnesia, hafnia, and ittria. The particle size of these refractory powders is not particularly limited, but is preferably about 10 gm to about inm.
Particles having a particle size of about 100% are used. If the particle size of the powder is too small, the powder particles may sinter together during firing, making it difficult to take out the porcelain from the powder.If the particle size of the powder is too large, the effect of enveloping the press-formed object in the powder will be poor. Sometimes we just can't get enough.

The method of wrapping the press-molded product with fire-resistant powder is not particularly limited.
Any method may be used as long as the entire pressure-molded product is completely surrounded by a layer of refractory powder of a certain thickness or more. For example, by putting refractory powder into a platinum port for firing,
The method of completely embedding the press-molded product to be treated in the powder is a simple and reliable method. In either method, it is necessary that the entire pressure-molded product is surrounded by a sufficiently thick layer of refractory powder, and if even a portion of the layer of refractory powder is too thin, the effect of the present invention may not be fully achieved. Moreover, if it is too thick, the heat capacity of the powder layer will become excessive and the effect of rapid temperature rise will be reduced. The preferred thickness of the refractory powder layer is
Although this cannot be said depending on the particle size of the refractory powder, heating rate, firing temperature, size of the press-molded product, etc., it is generally 2 to 5 mm.
It is.

The press-molded product used in the method of the present invention is prepared by mixing, for example, barium carbide magnesium llide and ditantalum pentoxide in proportions such that BaO-MgO-Ta2O5 porcelain with the required composition is obtained according to a conventional method. The material was then completely converted into oxide through calcination and then pressure molded. Although there are no particular limitations on the pressure molding method, a method using isostatic pressure is preferred, and the pressure of pressure molding is not particularly limited, but is preferably 1000 kg/cm or more.

The composition of the press-molded product is represented by the general formula, x, y
and 2 must be as defined above, x,
If any one of y and 2 is not within the above range, the resulting porcelain will be.

Not dense, has low mechanical strength and low no-load Q, x
, y and 2 are preferably 0.56≦x≦, respectively.
0.64.0.18≦y≦0.22 and 0.18≦z
The range is ≦0.22.

The temperature increase rate in the method of the present invention is 100 to 1500°C
, preferably at 200 to 1600°C. If the heating rate is less than 100°C, sintering will be insufficient and the resulting porcelain will have a low unloaded state.
Exceeding this may cause the porcelain to crack. Such rapid temperature increase can be carried out by various methods. For example, a method in which a press-formed product wrapped in refractory powder is suspended from above using a thermal shock-resistant platinum support (e.g., a boat) into the heated furnace core tube of a vertical furnace; Examples include a method in which the core tube is placed on a platinum support and pushed up from below, and a method in which it is rapidly heated with an image furnace using infrared rays, a xenon lamp, or sunlight. The first method of suspending the metal into the heated furnace core tube is a simple and suitable method.

Furthermore, the firing temperature in the present invention is 1500 to 1700°C.
, preferably between 1550 and 1650°C; if this temperature is less than 1500°C, the sintering will be insufficient, and the resulting porcelain will have low mechanical strength and low unloaded Q. If the firing temperature exceeds 1.700°C, the treated porcelain will react with the platinum container, which is often used as a holding container for porcelain during the firing process due to its high high temperature stability, and the properties of the resulting porcelain will deteriorate. do.

The holding time after the temperature of the press-molded product reaches a desired temperature in the range of 1,500 to 1,700°C needs to be appropriately selected depending on the rate of temperature increase, etc., but is not particularly limited. Generally, holding for 30 minutes or more is preferred.

The method of the present invention is preferably carried out in an inert atmosphere such as nitrogen gas or argon, or a nurturing atmosphere such as air or oxygen gas.

[Example] The present invention will be specifically explained below using an example, but the scope of the present invention is not limited to these.

In the following Examples and Comparative Examples, heating and firing of the press-molded products were performed in the following manner.

The furnace core tube soaking section of the vertical high-temperature furnace is set in advance to the desired firing temperature.The refractory powder is put into the platinum port, and the press-formed product to be treated is placed on top of it. The top was covered with refractory powder and wrapped to ensure complete burial.
This platinum port is lowered and inserted from the upper end of the furnace core tube into its soaking section.The heating rate of the object to be treated is variable at a speed attached to a cable connected to the other end of the platinum wire. It can be controlled by changing the lowering speed of the platinum port using the motor.

Powders of barium carbonate, barium oxide, and ditantalum pentoxide, each having a purity of 99.9%, were used as raw materials for the example, and these three substances were first mixed at a predetermined ratio. That is, in each of Examples 1 to 28, the general formula xBaOs yMgo11 representing the composition of the obtained porcelain is used.
The x, y, and 2 in zTa2O5 are measured so that they are the values shown in Table 1. 0.
(15≦z≦0.25) was placed in a polyethylene pot together with pure water, and mixed for 16 hours using a pole whose surface was coated with resin. This mixture was taken out from the pot and dried at 120°C for 12 hours.
kg/crn' pressure to form a lump, and in order to convert the carbon salt in the mixture into an oxide, it was heated on a platinum plate in air at 90°C.
Calcining was performed at 0 to 1300°C for 2 hours. After calcining, the mass was crushed in an alumina mortar and passed through a 42-mesh sieve to adjust the particle size. The obtained powder was crushed to a diameter of 10 mm at a pressure of 500 kg/cm'.
After primary forming into a disk shape with a thickness of about 5 mm, pressure 2
It was compressed under an isostatic pressure of 000 kg/cm'' to form a molded product.The resulting press-molded product was wrapped in a refractory powder in a platinum port as described above and subjected to firing.The refractory powder was alumina, Using zirconia or magnesia powder, conditions were set such that the heating rate was within the range of 100 to 0-1700°C and the holding time at the firing temperature was within the range of 30 minutes to 4 hours. The type and particle size of the refractory powder, temperature increase rate, firing temperature, and holding time at the firing temperature in each example are shown in Table 1.The press-molded products of Examples 12 to 17 were They were put together into two platinum ports and fired at the same time. Examples 18 to 23 were also fired at the same time. Other examples were fired individually.

Relative permittivity (ε) and unloaded Q (Qu) of the obtained porcelain
was measured at a frequency near IIGH2 using the dielectric resonator method. The results obtained are shown in Table 1.

In Table 1, the degree of deformation was evaluated based on the following criteria.

○...There is no deformation of the porcelain at all.

Δ... Deformation of the porcelain has occurred.

×: Significant deformation of the porcelain occurs.

Note that the measurements of porcelain (and Qu), which are significantly deformed, were performed after shaping by machining such as grinding.

Comparative Examples As shown in Table 1, porcelains of Comparative Examples 1 to 12 were produced in the same manner as in the Examples except that the molded bodies were not wrapped in refractory powder. In Comparative Examples 1 to 6 and Comparative Examples 7 to 12, the press-molded products were placed together in a platinum port and fired at the same time.

From the results in Table 1, it can be seen that in the case of Examples, the obtained porcelain was not deformed at all and was fired uniformly. Furthermore, it can be seen that the ε and Qu of the porcelains obtained in Examples 12 to 17 and Examples 18 to 23, which were treated at the same time, had extremely small variations, and that porcelains with uniform characteristics were manufactured. On the other hand, in the comparative example, it was found that the individual porcelains were deformed and the firing was uneven, and even among the pieces fired at the same time, there was a large variation in ε and Qu, and the firing was uneven between the products. I understand that there is something.

[Effect of the invention] As is clear from the results of the examples, the Bao-MgO-Ta2O5-based dielectric ceramic obtained by the present invention has a high no-load Q without adding elements such as Mn. In particular, it has a high dielectric constant of about 23 or more and an unloaded Q of 9000 or more at a frequency around 11 GHz, which is suitable for satellite communications, etc., making it excellent as a low-loss dielectric ceramic for high frequencies. In addition, the manufacturing method of the present invention has a simple manufacturing process and relies on rapid temperature raising firing, so the heating time that conventionally required several hours can be shortened to several minutes, making the firing process extremely simple. It has the effect of being simple and speedy.

Furthermore, since the side porcelain obtained by the manufacturing method of the present invention is fired uniformly throughout, no deformation occurs, and therefore it can be used as a low-loss dielectric for high frequency applications such as dielectric resonators without post-processing such as grinding. It can be put to practical use as porcelain. In addition, the degree of firing is highly uniform between products, and the variation in dielectric properties between products is small.
Therefore, since porcelain of uniform quality can be obtained, quality control is easy and the product yield is high.

Claims (1)

[Claims] General formula: xBaO・yMgO・zTa_2O_5, where 0.5≦x≦0.7, 0.15≦y≦0.25, 0.15≦z≦0.25 in,
A pressure-molded product having a composition of x+y+z=1 is
In the manufacturing method of dielectric porcelain, which involves heating and firing at a heating rate of 100 to 1600°C/min to a temperature of 00 to 1700°C,
A manufacturing method characterized by wrapping the press-molded product in refractory powder during heating and firing.