JPH08319162A - Dielectric ceramic and its production - Google Patents

Abstract

PURPOSE: To obtain a dielectric ceramic which is applicable to high-frequency waves by formulating a composition of a specific formula substantially not containing platinum, and setting the Q value over a prescribed value. CONSTITUTION: A BaO source, an MgO source and a Ta2 O5 source are formulated in a prescribed proportion, mixed, milled to prepare a uniform starting composition and the composition is preliminarily fired at 600-900 deg.C for 1-4 hours. The pre-fired product is crushed and fired in a ceramic vessel not made of platinum to give the objective BaO-MgO-Ta2 O5 dielectric ceramic which has a composition of Bax Mgy Taz Ow (x+y+z=1; (w) is the number that neutralizes the total cationic charge of Ba, Mg, Ta and electrically neutralizes the whole ceramic; 0.500<=x<=0.505; 0.160<=y<=0.165; 0.332<=z<=0.338) substantially not containing platinum and has a Q value over 4,000 at 10GHz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic and a manufacturing method thereof, and more particularly to a high frequency dielectric ceramic which can be suitably applied to a high frequency exceeding 40 GHz and an advantageous manufacturing method thereof.

[0002]

BACKGROUND ART In recent years, JP-A-53-60544, JP-A-58-206003 and JP-A-5-19401.
BaO-MgO-Ta ₂ O ₅ based dielectric ceramic having a composite perovskite crystal structure has been demonstrated in 7 discloses such, like BaO-ZnO-Ta ₂ O ₅ based dielectric ceramic, for high-frequency Has been recognized as a promising high Q material, but such BaO-MgO-T
Even in a ₂ O ₅ based dielectric ceramic, the Q value (at
10 GHz) exceeding 50,000 has not yet been realized, and Q values exceeding 40,000 are simply
Only one or two reports have been made.

For example, in JP-A-5-54718, Ba (Sn _x Mg _y Ta _z ) O is described in Example 13 thereof.
_{In the w} composition, it has been clarified that a dielectric porcelain having a Q value of 46000 was obtained when x = 0.005, y = 0.330, and z = 0.665, but it is only , Sn-added composition, which is different from the dielectric porcelain composed only of BaO, MgO and Ta ₂ O ₅ .

In addition, "JAPANESE JOURNAL OF APPLIED PH
YSICS "VOL.30, No.9B (1991), pp.234
7 to 2349 include Ba (Mg, Ta) O ₃ -BaSn.
An O ₃ -based high-Q dielectric resonator material was clarified, in which the effect of addition of Sn was basically described, but Ba (Mg _1/3 , T without addition of Sn was also described.
It was also clarified that in the a _2/3 ) O ₃ composition, in other words, in the stoichiometric composition, Q = 43000 was obtained. However, there high Q
There is no mention of the reason why the value was obtained,
It is simply said that the manufacturing process adopts a standard synthesis method, and no specific explanation is made about the specific manufacturing conditions.

On the other hand, BaO-MgO-Ta ₂ O ₅ -based dielectric ceramics have hitherto been stoichiometrically composed, that is, Ba (M
g _1/3 , Ta _2/3 ) O ₃ (Ba + Mg + T)
If a = 1, Ba = 0.500, Mg = 0.16
7, which corresponds to Ta = 0.333) has been considered to be the most desirable, and it has been clarified in JP-A-5-194017 that such a stoichiometric composition is conventional BaO-MgO-Ta ₂ O, which adopted
The Q value of the ₅ series dielectric porcelain was low, and therefore there was an inherent problem that required characteristics could not be obtained.

[0006]

The present invention has been made in view of such circumstances, and the problem to be solved is that the Q value at a measurement frequency of 10 GHz is 40,000 or more, further 50000 or more. The present invention is to provide a dielectric ceramic and a manufacturing method thereof which are extremely high, and also to provide a dielectric ceramic applicable to a high frequency band exceeding 40 GHz and a manufacturing method thereof.

[0007]

SOLUTION: As a result of various investigations by the present inventors to solve such a problem, as a result, BaO-MgO
In -ta ₂ O ₅ based dielectric ceramic, the composition of the narrow region very close deviating from the stoichiometric composition, significantly contributing composition dependency area to the improvement of Q value that resides found, also, It has been found that platinum generated from the firing container or the like during the firing is mixed as an impurity in the dielectric porcelain, which has a significant adverse effect on the Q value characteristic.

[0008] In particular, since platinum is extremely stable even at high temperatures, conventionally, when firing a dielectric ceramic, a firing container, a supporting jig, a setter or the like which is exposed to a high temperature is generally made of platinum. Has been done. However, even in a baking container made of platinum, etc., it has been confirmed that weight loss is induced at a high temperature for a long time.
It is due to the evaporation of platinum. However, the amount is very small, and it has been conventionally considered that it does not affect the dielectric porcelain, but by the study of the present inventors, such evaporated platinum is
It has been clarified that even a small amount of the material has a great influence on the dielectric ceramic characteristics, especially the Q value, when mixed in the fired dielectric ceramic.

On the basis of the above two findings, the present invention makes it possible to maintain a very narrow specific composition range by substantially not containing platinum. BaO-MgO-Ta ₂ O ₅ but Q value at 10GHz is 40,000 or more
A realizes a system dielectric ceramic, and has as its features, the general _{formula: Ba x Mg y Ta z O} w ( here, x
+ Y + z = 1, w is a number that neutralizes the total charge of the cations of Ba, Mg, and Ta, and is electrically neutral as a whole porcelain) And in the formula, 0.500 ≦ x ≦ 0.505, 0.1
The dielectric porcelain has characteristics of 60 ≦ y ≦ 0.165, 0.332 ≦ z ≦ 0.338, and substantially no platinum and having a Q value of 40,000 or more at a measurement frequency of 10 GHz.

The present invention also has the general formula: Ba _x Mg _y T
a _z O _w (where x + y + z = 1 and w is Ba, M
A dielectric porcelain having a composition represented by the following formula, which neutralizes the total electric charge of the cations of g and Ta and makes the porcelain electrically neutral as a whole. 501 ≦ x ≦
0.503, 0.162 ≦ y ≦ 0.164, 0.334
≦ z ≦ 0.336, substantially no platinum, and a Q value of 5000 at a measurement frequency of 10 GHz.
A dielectric porcelain having a characteristic of 0 or more is also the subject matter thereof.

When manufacturing the dielectric porcelain according to the present invention, the raw material composition giving the dielectric porcelain is held at a temperature of 600 ° C. to 900 ° C. for at least 1 minute or more to perform calcination. After the squeezing, a technique of firing the platinum material in the ceramic container without allowing the platinum material to exist is adopted.

Further, in the above-mentioned dielectric ceramic according to the present invention, after the raw material composition to give it is calcined, the constituents of the dielectric ceramic or the raw material thereof or the calcined material thereof is placed in a ceramic container. It can also be advantageously produced by a method of firing in the presence of a fired body without allowing the platinum material to be present.

Further, the above-mentioned dielectric ceramic according to the present invention is made of ceramics after being calcined by holding the raw material composition for giving it at a temperature of 600 ° C. to 900 ° C. for at least 1 minute or more. More effectively by adopting a method of firing in a container in the presence of a component constituting the dielectric porcelain or a raw material thereof, or a calcined product or a fired body thereof without allowing a platinum material to exist. It can be manufactured.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION When manufacturing such a dielectric ceramic according to the present invention, the above-mentioned general formula: Ba is used.
_{x Mg y Ta z O w (} x, y, z, w is being as the provisions) to provide a dielectric ceramic having a composition represented by, BaO source material, MgO source material and Ta ₂ O _{The five} source materials are blended to prepare the raw material composition. What is important in the present invention is the composition of the finished dielectric ceramic (after firing). It is necessary to mix the respective raw materials so that the composition shown in FIG.

Therefore, for example, when firing is performed for a long time, the composition of the dielectric ceramic changes during firing, and as a result of the change in the composition, the Q value may vary depending on the firing time. Therefore, the raw material composition needs to be prepared in anticipation of such a change during firing. Further, as will be described later, even if the composition of the raw material composition is different from the composition defined by the general formula (final composition), at the time of firing, a material such as a powder having a composition that complements the composition, It is also possible to put the composition in a baking container such as a baking crucible and control the finished composition within the composition range defined by the above general formula. The BaO source material, MgO source material, T
₂ O ₅ source materials are all oxides of Ba, Mg and Ta,
In addition to hydroxides, they are used in the form of inorganic acid salts such as carbonates and organic acid salts such as acetates.

Then, the raw material components consisting of the BaO source material, the MgO source material and the Ta ₂ O ₅ source material are prepared so as to give a desired dielectric porcelain composition in consideration of firing conditions, and mixed and ground. After being made into a uniform raw material composition, it is subjected to a calcination operation similar to the conventional one. However, in this calcination process, 600 ℃
It is desirable to carry out the calcination operation for 1 minute or more, preferably for 1 hour to 4 hours by adopting a calcination temperature of ˜900 ° C., whereby the target characteristics of the present invention can be advantageously realized. Can be done. If the calcination temperature exceeds 900 ° C, the calcination product becomes hard, and there is a problem that impurities such as abrasion of cobblestones in the crushing process may be caused. The calcination causes unevenness in the sintered body and causes problems such as cracking.

Then, the calcined product thus obtained by calcination is then pulverized according to a conventional method, further granulated if necessary, and then molded into a desired shape, and known in the art. It will be fired according to the firing operation, at that time, members such as firing containers and setters such as firing crucible,
It is made of non-platinum so that no platinum material is present in the firing system. However, even in the case of platinum, which has been conventionally stable at high temperatures, the firing temperature used in firing BaO—MgO—Ta ₂ O ₅ -based dielectric ceramics, for example, 1500
This is because at a high firing temperature of ˜1700 ° C., it volatilizes to some extent and enters the dielectric ceramics, which adversely affects the characteristics of the dielectric ceramics.

In the present invention, the content of platinum is specifically set to 1 ppm or less so as to prevent platinum from being substantially contained in the dielectric porcelain in order to avoid such inclusion of platinum. The characteristics of the dielectric porcelain used can be significantly improved. In particular, in the present invention, a ceramic container is used as a firing container such as a firing crucible so that a platinum material does not exist in such a firing system,
Among the setters and the like, those made of ceramics will be advantageously used, but above all, the firing crucible and the setter made of high-purity magnesia ceramics will be advantageously used.

Further, in such firing, the composition of the obtained dielectric ceramic may change due to long-term firing, and there is a possibility that the composition may deviate from the composition defined by the above-mentioned general formula. It is desirable to carry out firing in the presence of the component constituting the body porcelain, the raw material thereof, the calcined product thereof, or the fired body to adjust the firing atmosphere. Specifically, in the firing system, each component of Ba, Mg, Ta, and O constituting the dielectric porcelain is used alone or in the form of its raw material, or in the form of a calcined product which gives the dielectric porcelain. Is made to exist in the form of the fired porcelain itself. And, the existence thereof controls the composition of the final dielectric ceramic so as to satisfy the general formula. Therefore, even if the composition of the raw material composition that gives the target dielectric porcelain is out of the composition range of the final dielectric porcelain, the above-mentioned materials such as powder of the constituents of the dielectric porcelain having a composition that compensates for it are used. ,
By putting in a firing container such as a firing crucible and performing a firing operation, it is possible to control the finished composition of the obtained dielectric porcelain within a target range, and thereby the Q value thereof. It can be effectively increased.

The general formula thus obtained: Ba _x Mg
_The dielectric porcelain according to the present invention having a composition represented by _y Ta _z O _w has a stoichiometric composition (x = 0.500, y = 0.167, z = 0.33) that has been conventionally desired.
Slightly deviating from 3) and its vicinity composition: 0.500 ≦ x ≦
0.505, 0.160 ≤ y ≤ 0.165, 0.332
≦ z ≦ 0.338, x + y + z = 1, preferably 0.5
01 ≦ x ≦ 0.503, 0.162 ≦ y ≦ 0.164,
0.334 ≦ z ≦ 0.336, x + y + z = 1, so that the composition in an extremely narrow region is satisfied, and thus the Q value at the target measurement frequency of 10 GHz is significantly improved.
That is, it is possible to obtain a dielectric porcelain having such characteristics that the Q value exceeds 40000 and reaches 50,000.

[0021]

The present invention will be described in more detail below by showing examples of the present invention, but the present invention is subject to any restrictions due to the description of such examples. Not to mention that. Also,
In addition to the embodiments shown below, various changes, modifications, improvements, etc. may be added to the present invention based on the knowledge of those skilled in the art without departing from the spirit of the present invention. Should be understood,

First, high-purity barium carbonate, magnesium oxide, and tantalum oxide were weighed under the respective firing conditions so as to have predetermined molar ratios that give the final dielectric ceramic composition shown in Table 1 below. , Zirconia cobblestone, wet-mixed in ethanol, dried, and the dried product in a magnesia crucible at 800 ° C x 2
I calcined for a while. Then, the obtained calcined product was wet-milled in ethanol together with zirconia cobblestone, and granulated through a 100-mesh sieve, and then temporarily molded using a uniaxial press machine. By applying a load of 4 tons / cm ^{2 to} the body and performing CIP molding, various rectangular shaped bodies of 12 mm × 5 mm were obtained.

Then, the following firing operation was carried out on the molded articles of various compositions thus obtained. First, for the compacts of Experiment Nos. 1 to 16, a calcining crucible made of magnesia ceramics was used, and 100 crushed calcined products used for each compact were placed in the calcining crucible.
g, and on the magnesia setter in it,
The compact to be fired was placed and fired at 1650 ° C. for 24 hours. When firing the molded body of Experiment No. 17, a platinum crucible was used as the firing crucible.
When firing the molded body of Experiment No. 18, a firing crucible made of magnesia was used, but a platinum plate was used as the setter. Further, in the firing of the molded body of Experiment No. 19, except that the molded body formed by using the calcined product subjected to the calcination step of 1000 ° C. × 2 hours was used, Dielectric porcelain was manufactured in the same manner as the molded body of 16.

With respect to the various dielectric ceramics (sintered bodies) of Experiment Nos. 1 to 19 thus obtained, the composition of the ceramics was analyzed by the wet analysis method, and the relative permittivity and the measurement frequency were 1
The Q value and the sintered density at 0 GHz were evaluated, and the results are shown in Table 1 below. Note that the analysis of the porcelain composition by the wet analysis method was performed by quantifying Ba and Ta by the gravimetric method (by which Ba and Ta are precipitated and separated), and then by quantifying Mg by the chelate titration method. . Further, the Pt content contained in the dielectric ceramics (sintered body) obtained in Experiment Nos. 9, 17 and 18 was also analyzed, and the results are shown in Table 2 below.

[0025]

[Table 1]

[0026]

[Table 2]

As is clear from the results of Tables 1 and 2, the porcelain compositions of Experiment Nos. 5, 7, 8, 9, and 13 according to the present invention satisfying x, y and z in the above general formula. In all, the Pt content was not detected, and the Q value had excellent characteristics of 40,000 or more, and even more than 50,000. On the other hand, Experiment No. 1 of the composition which does not satisfy any of x, y and z in the above general formula
~ 4, 6, 10-12, 14-16,
Furthermore, even if such a composition was satisfied, the Q value was low in Experiment Nos. 17 and 18 in which Pt was contained in the dielectric ceramic (sintered body).

The composition of the calcined pulverized powder obtained by calcining in the same manner as above, using the ones shown in Table 3 below, was used to obtain a molded body (rectangular plate) obtained in the same manner as described above. , Firing at different firing times, firing in the same manner as above,
With respect to the obtained fired body (dielectric porcelain), the Q value and the values of x, y, and z were examined in the same manner as above, and the result was
The results are shown in Table 3 below.

[0029]

[Table 3]

As is clear from the results shown in Table 3, even if the composition of the calcined pulverized powder, and by extension, the composition of the raw material deviates from the final composition of the dielectric ceramic, x, When each value of y and z falls within the specified range of the present invention, an excellent Q value is realized.

Further, in Table 4 below, there are shown a case in which a calcined pulverized powder having the same composition as that of the molded body and a case in which the calcined pulverized powder having a composition different from that of the molded body are placed in a magnesia-made crucible. Although the results for the final composition and the Q value of the obtained sintered body (dielectric ceramics) are shown, even if the calcined powder composition, and thus the raw material composition, is outside the scope of the present invention, Depending on the composition of the calcined pulverized powder put into the firing crucible, a sintered body within the scope of the present invention can be obtained, and thereby the Q value of the obtained sintered body is also effectively improved. It is recognized that it can be done.

[0032]

[Table 4]

[0033]

As apparent from the above _{description, BaO-MgO-Ta 2 O} 5 based dielectric ceramic according to the present invention, so as to satisfy the composition of the narrow region very near the stoichiometric composition A dielectric porcelain prepared and substantially free of platinum, which has a high Q value in the microwave band and a large relative permittivity, and exceeds 40 GHz. It is of great technical significance that it is a dielectric ceramic that can be applied particularly advantageously to such a high frequency band. Further, the dielectric porcelain having such excellent characteristics, by adopting a specific calcination operation, or together therewith, or in place of it, in the presence of a dielectric porcelain constituent component or its raw material, By adjusting the firing atmosphere and performing firing without allowing the platinum material to exist, it was possible to industrially advantageously manufacture, and there is a great technical significance of the present invention. It exists.

Claims (5)

[Claims] 1. A general formula: Ba _x Mg _y Ta _z O _w (where x + y + z = 1, and w neutralizes the total charge of the cations of Ba, Mg, and Ta, and electrically as a whole porcelain. A dielectric porcelain having a composition represented by the following formula: 0.500 ≦ x ≦ 0.505,
0.160 ≦ y ≦ 0.165, 0.332 ≦ z ≦ 0.3
A dielectric porcelain having a characteristic of having a Q value of 40, 000 or more, which is 38 and does not substantially contain platinum. 2. A general formula: Ba _x Mg _y Ta _z O _w (where x + y + z = 1, and w neutralizes the total charge of the cations of Ba, Mg, and Ta, and electrically as a whole porcelain. A dielectric porcelain having a composition represented by the following formula: 0.501 ≦ x ≦ 0.503,
0.162 ≦ y ≦ 0.164, 0.334 ≦ z ≦ 0.3
36. A dielectric porcelain having a characteristic of having a Q value of 50,000 or more at a measurement frequency of 10 GHz, which is 36, and does not substantially contain platinum. 3. A method for producing a dielectric ceramic according to claim 1 or 2, wherein the raw material composition for providing the dielectric ceramic is held at a temperature of 600 ° C. to 900 ° C. for at least 1 minute or more. As a result, the method for producing a dielectric ceramic is characterized in that, after being calcined, the platinum material is fired in the ceramic container without being allowed to exist. 4. A method for producing a dielectric porcelain according to claim 1 or 2, wherein a raw material composition that gives the dielectric porcelain is calcined, and then the dielectric porcelain is placed in a ceramic container. A method for producing a dielectric ceramic, which comprises firing in the presence of constituent components, raw materials thereof, calcined products thereof, or a fired body thereof without the presence of a platinum material. 5. A method for producing a dielectric porcelain according to claim 1 or 2, wherein the raw material composition for providing the dielectric porcelain is held at a temperature of 600 ° C. to 900 ° C. for at least 1 minute or more. Thus, after calcination, in the ceramic container, in the presence of the components constituting the dielectric porcelain or its raw material or its calcined product or fired body,
A method for manufacturing a dielectric ceramic, which comprises firing without making a platinum material exist.