JP2005225735A - Production method for dielectric porcelain composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dielectric porcelain composition which, though prepared by a solid phase method, yields a fine dielectric powder inhibited from deterioration of dielectric properties. <P>SOLUTION: The dielectric porcelain composition contains a perovskite oxide having an atomic arrangement of an ABO<SB>3</SB>type. The method for producing the composition comprises a calcining step in which a mixture containing an A site raw material powder for constituting an A site and a B site raw material powder having a BET value of 20-40 m<SP>2</SP>/g and for constituting a B site is calcined to yield a calcined product, a grinding step of grinding the calcined product to yield a ground powder, and a firing step in which the ground powder having subjected to a specified treatment is kept heated under specified conditions to yield a fired product. Since the ground powder is prepared by using the B site raw material powder having a BET value of 20-40 m<SP>2</SP>/g, the powder can be made fine, specifically so as to have a D50 (diameters of particles of which the cumulative number is 50%) of 1 μm or less, moreover 0.8 μm or less, without passing through long-time grinding. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a dielectric ceramic composition.

In recent years, miniaturization, weight reduction, and speeding up of communication devices have been strongly desired. Among them, the frequency band of radio waves used for portable mobile communications such as digital cellular phones and satellite communications is in the high frequency band of mega to giga Hz band (referred to as “GHz band”). Amid the rapid development of used communication equipment, the housing, board, and electronic elements have been miniaturized and densely mounted. However, the communication equipment that supports the high frequency band has been further reduced in size and weight. In order to achieve this, materials such as substrates used in communication equipment must be excellent in high-frequency transmission characteristics (low dielectric loss) in the GHz band. Here, the dielectric loss is proportional to the product of the frequency, the relative dielectric constant εr of the substrate, and the dielectric loss tangent (hereinafter referred to as tan δ). Therefore, in order to reduce the dielectric loss, tan δ of the substrate must be reduced. Further, since the wavelength of the electromagnetic wave in the substrate is shortened to 1 / (εr) ^0.5 , the substrate can be downsized as the relative dielectric constant εr increases. As described above, a circuit board used for a small communication device, electronic device, or information device used in a high frequency band has a high relative dielectric constant εr and Qf (quality factor Q = 1 / tan δ, f = resonance frequency). Is required to be large.

  As a material for such a circuit board, a dielectric material (baked product) as an inorganic material, a fluororesin as an organic material, or the like is used. However, a substrate made of a dielectric material has problems in dimensional accuracy and workability, and is fragile, so that there is a problem that chips and cracks are likely to occur. On the other hand, a substrate made of an organic material such as a resin has the advantage of being excellent in moldability and workability, but has a problem that the relative dielectric constant εr is small. Therefore, in recent years, as a substrate having both advantages, for example, a composite substrate made of a dielectric powder and a resin material in Patent Document 1 (Japanese Patent Laid-Open No. 2003-128930) and Patent Document 2 (Japanese Patent Laid-Open No. 2003-151352). Is disclosed.

As the dielectric material, a perovskite oxide having an ABO ₃ type atomic arrangement such as barium titanate and lead zirconate titanate is usually used, and a method for producing the powder (dielectric powder) is a liquid phase. Methods, gas phase methods, flux methods and solid phase methods are known.
In the liquid phase method, a metal oxide precursor powder such as a hydrate is produced using a metal salt aqueous solution or an organic solvent solution as a starting material, and then the precursor powder is fired to contain two or more kinds of metal elements. This is a method for producing a metal oxide powder. As the liquid phase method, a precipitation method, a coprecipitation method, a hydrolysis method and the like are known.
The gas phase method is a method for producing a metal oxide powder by a chemical reaction of a metal vapor or a metal compound in a gas phase state, and has an advantage that a powder having a narrow particle size distribution and less aggregation is obtained.
The flux method is a method for producing a metal oxide powder by adding a flux component to a metal oxide mixed powder and firing it.

JP 2003-128930 A Japanese Patent Laid-Open No. 2003-151352

  The dielectric powder obtained by the above liquid phase method, gas phase method and flux method has the advantage that the particle size can be made fine and the particle size distribution can be narrowed. Here, when the composite substrate described above is manufactured, it is desirable that the dielectric powder mixed with the resin material has a small particle diameter when the interlayer when the composite substrate is laminated is thinned. Since the dielectric powder obtained by the liquid phase method, the gas phase method and the flux method has a fine particle size, it is a desirable method for producing a dielectric powder in producing a composite substrate. However, there is a problem that the cost of the dielectric powder obtained by these methods is high.

A solid phase method is known as a method for obtaining dielectric powder at a lower cost than the above methods. The solid phase method includes a step of calcining a powder of metal oxide, carbonate, etc., crushing the calcined product, calcining it, and crushing the obtained calcined product. For example, when obtaining barium titanate, it can be manufactured through steps of mixing, calcining, pulverizing, baking, and pulverizing the baked product by mixing TiO ₂ powder and BaCO ₃ powder as raw material powders. However, first, distortion occurs in the pulverized powder in the pulverization process after calcination, and the dielectric characteristics deteriorate at that time. Here, in order to obtain a powder having a small particle size by pulverization after firing, it is necessary to obtain pulverization as fine as possible in pulverization after calcination. Therefore, the dielectric properties of the obtained powder are deteriorated. If the pulverization time is shortened in order not to deteriorate the dielectric characteristics, it is impossible to obtain a fine dielectric powder. Therefore, until now, there has been a problem that a composite substrate using a dielectric powder by a solid phase method cannot obtain desired characteristics. On the other hand, if a powder with little deterioration in dielectric properties can be obtained by the solid phase method, it becomes a very desirable method for producing a dielectric powder in order to obtain a composite substrate, considering the cost.

  In view of the above background, the present invention has an object to provide a method for producing a dielectric ceramic composition capable of obtaining a fine dielectric powder in which deterioration of dielectric properties is suppressed while using a solid phase method. To do.

A dielectric ceramic composition containing a perovskite oxide having an ABO ₃ type atomic arrangement targeted by the present invention includes an A site raw material powder for constituting the A site and a B site raw material powder for constituting the B site. Can be obtained by mixing and baking. For example, in order to obtain (Sr, Ca) TiO ₃ , SrCO ₃ powder and CaCO ₃ powder are usually prepared as the A site material, and TiO ₂ powder is prepared as the B site material. According to the study by the present inventors, the dielectric ceramic composition obtained by firing is pulverized by controlling the specific surface area of the B-site raw material (value according to the BET method, referred to as BET value in the present invention) to a specific value. It has been found that a sufficiently fine powder can be obtained even if the amount is small.

The present invention is based on the above knowledge, and is a method for producing a dielectric ceramic composition containing a perovskite oxide having an ABO ₃ type atomic arrangement, and comprising the A site raw material powder and the B site constituting the A site. A calcining step of calcining a mixture including a B-site raw material powder having a BET value of 20 to 40 m ² / g to obtain a calcined product, a crushing step of crushing the calcined product to obtain a pulverized powder, And a calcination step of obtaining a baked product by heating and holding the treated pulverized powder under predetermined conditions. In the present invention, the pulverized powder can be fired after being formed into a predetermined shape, or the pulverized powder can be fired without being formed into a predetermined shape.
The pulverized powder according to the present invention uses a B-site raw material powder having a BET value of 20 m ² / g or more, so it is fine, specifically 1 μm or less, and further 0 without being pulverized for a long time. D50 of 8 μm or less (particle size of particles with a cumulative number of 50%). Since this pulverized powder does not need to be pulverized for a long period of time, distortion caused by pulverization is small and excellent dielectric properties can be exhibited. Therefore, the dielectric ceramic composition of the present invention fired using this pulverized powder, and further, the dielectric powder obtained by pulverizing this dielectric ceramic composition can also exhibit excellent dielectric properties. it can. Similarly to the pulverized powder after calcination, this dielectric powder can be made fine with a D50 of 1 μm or less without being pulverized for a long time. However, when the BET value of the B-site raw material powder exceeds 40 m ² / g, the Qf of the dielectric ceramic composition is lowered. Therefore, in the present invention, the BET value of the B-site raw material powder is set to 20 to 40 m ² / g. The predetermined treatment is a concept including adding and mixing various subcomponents. However, this subcomponent can also be added before calcination.

  In the dielectric ceramic composition according to the present invention, the A site contains one or more atoms selected from Ba, Ca and Sr, and the B site is selected from one or two selected from Ti, Zr and Nb. It is desirable from the viewpoint of dielectric properties to contain more than seed atoms.

  As described above, by using the dielectric ceramic composition of the present invention, a fine dielectric powder can be obtained without being pulverized for a long time. By molding and firing this dielectric powder, a bulk dielectric ceramic composition having excellent dielectric characteristics can be produced. Further, by using this dielectric powder, a composite dielectric material having low cost and excellent dielectric characteristics can be obtained.

The dielectric ceramic composition to which the present invention is applied includes a perovskite oxide having an ABO ₃ type atomic arrangement. Here, the A site contains one or more atoms selected from Ba, Ca and Sr, and the B site contains one or more atoms selected from Ti, Zr and Nb. Is desirable. Therefore, the present invention is desirably applied to at least the following perovskite oxides.
SrTiO ₃ , CaTiO ₃ , (Sr, Ca) TiO ₃ , (Sr, Ba) TiO ₃ , (Ca, Ba) TiO ₃ , (Ba, Sr, Ca) TiO ₃
SrZrO ₃ , CaZrO ₃ , (Sr, Ca) ZrO ₃ , (Sr, Ba) ZrO ₃ , (Ca, Ba) ZrO ₃ , (Ba, Sr, Ca) ZrO ₃
SrNbO ₃ , CaNbO ₃ , (Sr, Ca) NbO ₃ , (Sr, Ba) NbO ₃ , (Ca, Ba) NbO ₃ , (Ba, Sr, Ca) NbO ₃
Sr (Ti, Zr) O ₃ , Ca (Ti, Nb) O ₃ , (Sr, Ca) (Zr, Nb) O ₃ , (Sr, Ba) (Ti, Zr, Nb) O ₃

The dielectric ceramic composition to which the present invention is applied can contain the above-described perovskite oxide as a main component and can further contain various subcomponents. In the present invention, an oxide of A (where A is one or two elements selected from Ni, Mn and Cr) can be added as a subcomponent. In addition, an oxide of X (where X is one or more elements selected from V, Nb, W, Ta, and Mo) can be added as a subcomponent. Further, R (where R is Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu are selected from one or two kinds Oxides of the above elements) can be added. Furthermore, SiO ₂ , MO (where M is one or more elements selected from Ba, Ca, Sr and Mg), Li ₂ O, B ₂ O ₃ and one kind selected from MSiO _3. Alternatively, two or more compounds can be added.

The present invention is a method for producing a dielectric ceramic composition containing a perovskite oxide having the ABO ₃ type atomic arrangement described above. A dielectric ceramic composition made of a fired product includes, for example, a step of mixing raw material powders weighed so as to have a final composition, a step of calcining the mixed powder, a step of grinding the calcined product, and a step of firing the ground powder. It can manufacture by passing. Through this manufacturing method, the dielectric powder can be obtained by pulverizing the above-mentioned calcined product, or can be obtained by pulverizing the fired product obtained through the firing step. Assuming that the former mode is the first mode and the latter mode is the second mode, when the dielectric powder is produced using the dielectric ceramic composition according to the present invention, the second mode falls under the pulverization according to the first mode. It is also possible to produce a dielectric composite material using powder. The effect of controlling the particle size of the B-site raw material powder in the present invention is embodied in the first aspect, that is, the pulverized powder after calcination, and also in the second aspect, that is, the powder obtained by pulverizing the fired product. Embodied. Hereinafter, the first aspect and the second aspect will be described.

First, the first aspect will be described.
As the raw material for obtaining the dielectric ceramic composition of the present invention, a raw material constituting the main component and a raw material constituting the subcomponent are prepared. However, although the addition of subcomponents is desirable, it is not essential in the present invention.
As the raw material constituting the main component, an A site raw material powder for constituting the A site and a B site raw material powder for constituting the B site are prepared. As the A-site raw material powder and the B-site raw material powder, an oxide of the element and / or a compound that becomes an oxide by firing is used. Examples of the compounds that become oxides upon firing include carbonates, nitrates, oxalates, and organometallic compounds. These compounds and oxides may be used in combination. Specifically, as the A site raw material powder, it is desirable to use one or more selected from SrCo ₃ powder, CaCO ₃ powder and BaCO ₃ powder. As the B-site material powder, TiO ₂ powder, to use one or two or more kinds selected from ZrO ₂ powder and NbO ₂ powder desirable.

The present invention is characterized in that a B-site raw material powder having a BET value of 20 m ² / g or more is used. As shown in the examples to be described later, when the BET raw material powder has a BET value of 20 m ² / g or more, a fine dielectric having a D50 of 1 μm or less without pulverization for a long time after calcination. This is because a powder can be obtained. The dielectric ceramic composition obtained according to the present invention has good dielectric properties because it does not require long-term pulverization. As a result, the dielectric characteristics of the dielectric powder obtained by pulverizing the dielectric ceramic composition and the composite dielectric material using the dielectric powder are also good. However, as shown in the examples below, BET value of B site raw material powder because Qf exceeds ^{40 m} 2 / g decreases, the BET value of the B-site material powder and 20 to 40 m ² / g .
On the other hand, in the present invention, the A-site raw material powder does not need to specify the BET value unlike the B-site raw material powder. According to the study by the present inventor, the BET value of the A-site raw material powder does not affect the particle size of the obtained dielectric powder. Therefore, for the A-site raw material powder, D50 may be appropriately selected within the range of 0.01 to 5.0 μm.

The subcomponent raw materials constituting the subcomponent are as follows.
As for the oxide of A, the oxide of A and / or a compound that becomes an oxide of A upon firing can be used as a raw material.
As for the oxide of X, one or more single oxides or composite oxides selected from the oxide of X and / or the compound that becomes an oxide of X by firing can be used as a raw material.
As for the R oxide, one or more single oxides or composite oxides selected from R oxides and / or compounds that become oxides upon firing can be used as raw materials.
SiO ₂ , MO (where M is one or more elements selected from Ba, Ca, Sr and Mg), one or two selected from Li ₂ O, B ₂ O ₃ and MSiO ₃ About the above, the said compound can be used as a raw material.
The auxiliary component raw material powder may also be appropriately selected within a range of D50 from 0.01 to 5.0 μm.

The raw material powders of the above main component and subcomponent are weighed according to a desired composition and wet-mixed by, for example, a ball mill. After the slurry is dried, calcination is performed, for example, in the range of 900 to 1350 ° C. for a predetermined time. The atmosphere at this time may be N ₂ or O ₂ or a mixed gas thereof. What is necessary is just to select suitably the holding time of calcination in the range of 0.5 to 5.0 hours.

The calcined product obtained by calcining is pulverized. A ball mill or other pulverizing means can be used for the pulverization. When wet pulverization is performed, drying is performed after pulverization. According to the present invention, by setting the BET value of the B-site raw material powder to 20 m ² / g or more, D50 is 1 μm or less, further 0.8 μm or less while suppressing distortion due to short grinding time, in other words, distortion due to grinding. It is possible to obtain a fine dielectric powder. This pulverization may be performed under the same conditions as when the main component material and the subcomponent material are mixed.

Next, although a 2nd aspect contains the aspect which adds a subcomponent before calcination, and the aspect which adds a subcomponent after calcination, the aspect which adds a subcomponent after calcination is demonstrated here.
The second aspect is carried out until calcination and pulverization in the same manner as the first aspect described above, except that the subcomponent is not weighed and mixed with the main component. After this pulverization, the auxiliary component raw material is added to and mixed with the powder composed of the main component obtained by pulverization. This mixing may be performed in the same manner as the mixing of the main component material and the subcomponent material in the first embodiment.
The powder obtained by mixing is subjected to firing. Firing may be performed under the same conditions as the calcination described above. However, the present invention includes a case where the powder is molded prior to firing and a case where the powder is not molded. According to the former, a bulk dielectric ceramic composition (fired product) can be obtained after firing. Further, according to the latter, a massive or granular dielectric ceramic composition (fired product) can be obtained after firing. Furthermore, a bulk dielectric ceramic composition can be formed and fired to obtain a bulk dielectric ceramic composition (fired product).
The fired product obtained by firing is pulverized. This pulverization may be performed under the same conditions as the pulverization performed in the first embodiment. However, it is preferable to pulverize the bulk or granular dielectric ceramic composition rather than pulverize the bulk dielectric ceramic composition. Easy to obtain powder.
Similarly to the powder obtained in the first aspect, the dielectric powder obtained by the above process also has a fine particle size by pulverization in a relatively short time.

Hereinafter, the present invention will be described based on specific examples.
The following raw material powders were weighed with a composition of (Sr _0.64 Ca _0.36 ) TiO ₃ , A / B (molar ratio of A site atoms to B site atoms) = 0.994, and wet mixed by a ball mill. As the B site raw material, nine types of TiO ₂ powders having different BET values and D50 (particle diameter of the cumulative number of 50%) shown in Table 1 were prepared.
A-site raw material SrCO ₃ powder (BET value = 6.0 m ^{2 /} g, D50 = 0.50 μm)
CaCO ₃ powder (BET value = 18.8 m ^{2 /} g, D50 = 0.30 μm)
B site raw material TiO ₂ powder (BET value = 2.9 to 51.3 m ^{2 /} g, D50 = 1.75 to 0.27 μm)

Using a 6-inch pot as a ball mill and ZrO ₂ balls (φ10 mm: 1 kg, φ3 mm: 2 kg) as media, the treatment was performed at 120 rpm for 16 hours. The ball mill was charged with 800 g of mixed powder, and the slurry concentration was 33%. Further, prior to mixing, 0.2 wt% of a dispersant (manufactured by Toagosei Co., Ltd .: A-30SL) was added.
After the wet mixing by the ball mill was completed, drying was carried out using a dryer at a temperature of 120 ° C. for 24 hours.
The dried mixed powder was passed through a 355 μm mesh, and then calcined by being held at 1150 ° C. for 2 hours in a MgO bee.

The calcined product obtained using a ball mill was pulverized into a pulverized powder. Using a 4-inch pot as a ball mill and ZrO ₂ balls (φ10 mm: 200 g, φ3 mm: 430 g) as media, treatment was performed at 120 rpm for 16 hours. In addition, 150 g of the fired product was put in the pot, and the slurry concentration was 33%.
After pulverization by the ball mill was completed, drying was carried out using a dryer at a temperature of 120 ° C. for 24 hours. While measuring the particle size distribution of this powder, D50 was determined. The particle size distribution was measured using a Microtrac ultrafine particle size distribution meter (manufactured by Nikkiso Co., Ltd .: 9340-UPA150).

Table 1 shows the measurement results of D50 of the pulverized powder. FIG. 1 shows the relationship between the BET value of the B-site raw material powder (TiO ₂ powder) and D50 of the pulverized powder. It can be seen from Table 1 and FIG. 1 that by setting the BET value to 20 m ² / g or more, the D50 of the pulverized powder can be 1.0 μm or less, and further 0.8 μm or less. This indicates that a finer dielectric powder can be obtained with the same pulverization time. According to the present invention, a dielectric powder made from a fine dielectric powder with less distortion caused by pulverization and high dielectric properties is used. This suggests that a body porcelain composition can be obtained.

Next, after adding the powder of the following subcomponents to 100 mols of nine kinds of pulverized powders, wet mixing was performed by a ball mill. Using a 4-inch pot as a ball mill and ZrO ₂ balls (φ10 mm: 200 g, φ3 mm: 430 g) as media, treatment was performed at 120 rpm for 16 hours. Further, 100 g of the pulverized powder was put into the pot, and the slurry concentration was set to 33%. Further, prior to mixing, 0.2 wt% of a dispersant (manufactured by Toagosei Co., Ltd .: A-30SL) was added.
MnO (D50 = 0.55 μm): 0.365 mol V ₂ O ₅ (D50 = 0.52 μm): 0.1 mol Y ₂ O ₃ (D50 = 0.33 μm): 0.035 mol CaSiO ₃ (D50 = 1.178 μm): 1.616 mol

After the wet mixing by the ball mill was completed, it was dried using a drier at a temperature of 120 ° C. for 24 hours.
After adding 2.5 wt% (5 g) of 15% aqueous solution of AQ nylon P-70 manufactured by Toray Industries, Ltd. as a binder to 30 g of the dried mixed powder, it was dried at 100 ° C. for 90 minutes. And granulated.
This granulated powder was pressure-molded at a pressure of 1 ton / cm ² to obtain a molded body of φ12 mm × t6.2 mm. Next, the molded body was debindered by holding at 650 ° C. for 2 hours, then heated to 1350 ° C. and then held for 4 hours to be fired. The binder removal and firing were performed in an atmospheric flow. Moreover, the temperature increase rate in binder removal and baking is 200 ° C./hr.

  The dielectric ceramic composition obtained above was measured for dielectric constant (εr) and Qf by the dielectric resonator method (n = 2). The results are shown in Table 1. For the measurement, an RF vector network analyzer (manufactured by Yokogawa Hewlett-Packard Co., Ltd .: HP8510) was used. In measurement, the dielectric ceramic composition was polished into a sample having a thickness of 5 ± 0.5 mm.

FIG. 2 shows the relationship between the BET value of the B-site raw material powder and the relative dielectric constant (εr) and Qf of the obtained dielectric ceramic composition. As shown in FIG. 2, the dielectric constant (εr) and Qf of the dielectric ceramic composition increase as the BET value of the B-site raw material powder increases. However, when the BET value peaks at 30 m ² / g, the dielectric constant (εr) and Qf of the dielectric ceramic composition tend to decrease. From this result, in the present invention, the BET value of the B-site raw material powder is set to a range of ²⁰ to 40 m ² / g, desirably 25 to 35 m ² / g.

And BET value of B site material powder (TiO ₂ powder), is a graph showing the relationship between D50 of ground powder. And BET value of B site material powder (TiO ₂ powder), is a graph showing the relationship between the relative dielectric constant (.epsilon.r) and Qf of the dielectric ceramic composition.

Claims (3)

A method for producing a dielectric ceramic composition comprising a perovskite oxide having an ABO ₃ type atomic arrangement,
A calcining step of calcining a mixture containing the A site raw material powder constituting the A site and the B site raw material powder having a BET value of 20 to 40 m ² / g constituting the B site;
A pulverization step of pulverizing the calcined product to obtain a pulverized powder;
And a firing step of obtaining a fired product by heating and holding the pulverized powder subjected to a predetermined treatment under a predetermined condition. In the perovskite oxide having the ABO ₃ type atomic arrangement, the A site contains one or more atoms selected from Ba, Ca and Sr, and the B site is selected from Ti, Zr and Nb. 2. The method for producing a dielectric ceramic composition according to claim 1, wherein the dielectric ceramic composition comprises one or more atoms.   3. The method for producing a dielectric ceramic composition according to claim 1, wherein the pulverized powder has a D50 (particle diameter of 50% cumulative number) of 1 μm or less.

Images