JP5471093B2 - Method for producing dielectric ceramic composition - Google Patents

Description

  The present invention relates to a method for manufacturing a dielectric ceramic composition, and more particularly to a method for manufacturing a dielectric ceramic composition mainly composed of barium titanate.

  With the recent development of electronics technology, electronic parts such as multilayer ceramic capacitors have been rapidly reduced in size and capacity.

  In order to obtain a high-performance ceramic capacitor, various devices have been conventionally made in terms of materials.

For example, in Patent Document 1, the impurities are Ca, Sr, Mg, Y, Zr and alkali metal oxide, and the amount of Ca as the impurity is 4 to 340 ppm with respect to 100% by weight of the barium titanate powder. And
The amount of Sr as the impurity is 120 to 1500 ppm, the amount of Mg as the impurity is 0.6 to 150 ppm, the amount of Y as the impurity is 5 to 1000 ppm,
A barium titanate powder having a Zr content of 85 to 2000 ppm as the impurity and an alkali metal oxide content of 300 to 2000 ppm as the impurity has been proposed.

  In Patent Document 1, by setting impurities such as Ca, Sr, Mg, Y, Zr, and alkali metal oxides within the predetermined range, the dielectric layer constituting an electronic component such as a multilayer ceramic capacitor is further thinned. Even when layering or increasing the number of layers is achieved, the generation of cracks can be reduced and the manufacturing yield can be improved.

  That is, for example, regarding Ca among the above impurities, if the amount of Ca is too small, when the sintered body is produced using the obtained barium titanate powder, the sintering shrinkage behavior of the ceramic material and the conductive material On the other hand, mismatching of sintering shrinkage behavior is likely to occur. On the other hand, if the amount of Ca is too large, the crack rate and electrical characteristics may be deteriorated, resulting in a decrease in sinterability.

  Therefore, in Patent Document 1, sinterability is stabilized by setting the content of Ca as an impurity in the barium titanate powder to 4 to 340 ppm.

JP 2008-105870 A (Claim 1, paragraph number [0062], etc.)

  However, in Patent Document 1, as described above, the sinterability is stabilized by adjusting the content of Ca, which is an impurity, to 4 to 340 ppm, but in this case, the relative dielectric constant decreases, There has been a problem that electrical characteristics such as relative permittivity and temperature characteristics may not be stable.

  The present invention has been made in view of such circumstances, and is a dielectric ceramic composition capable of ensuring a desired high relative dielectric constant and maintaining a stable and stable temperature characteristic of capacitance. It is an object of the present invention to provide a method for producing a dielectric ceramic composition that can be obtained.

In a dielectric ceramic composition for a ceramic capacitor having a high relative dielectric constant based on barium titanate as a main component, CaZrO ₃ and other various complex oxides and oxides are usually appropriately added as subcomponents, depending on the application. I try to get electrical characteristics.

  Moreover, the ceramic raw material for synthesizing these dielectric ceramic compositions usually contains Ca or the like as an impurity.

  Then, the dielectric ceramic composition was prepared by adding the subcomponent powder to the main component powder containing barium titanate as the main component, and the electrical characteristics were evaluated. The amount of Ca contained in the subcomponent powder was reduced to the electrical characteristics. While the influence was small, it was found that the amount of Ca contained in the main component powder, barium titanate, had a great influence on the electrical characteristics.

  Therefore, the present inventors conducted further research, and as a result, by adjusting the content of the Ca component contained in the barium titanate to 200 to 322 ppm, a desired high relative dielectric constant can be secured and static It was found that a dielectric ceramic composition having a good temperature characteristic of capacitance can be obtained stably.

  The present invention has been made on the basis of such knowledge, and a method for producing a dielectric ceramic composition according to the present invention comprises preparing a plurality of ceramic raw materials containing a barium compound and a titanium compound to prepare barium titanate. In the method for manufacturing a dielectric ceramic composition comprising a main component powder preparation step for preparing a main component powder as a main component, the main component powder preparation step has a calcium component content of 200 to 200 in the main component powder. An addition amount adjusting step for adjusting the addition amount of the calcium compound so as to be 322 ppm is included.

  Moreover, the method for producing a dielectric ceramic composition of the present invention is characterized in that the calcium component contains inevitable impurities.

  Furthermore, in the method for producing a dielectric ceramic composition of the present invention, the main component powder preparation step includes calcining a preparation of the barium compound and the titanium compound and the calcium compound added in the addition amount adjusting step. It is characterized by including a calcination step.

  In addition, the method for producing a dielectric ceramic composition of the present invention is characterized by including a blending step of blending the main component powder and at least one subcomponent powder in a predetermined ratio.

Moreover, the method for producing a dielectric ceramic composition of the present invention is characterized in that the subcomponent powder contains CaZrO ₃ .

  According to the above method for producing a dielectric ceramic composition, the amount of calcium compound added is adjusted so that the content of the calcium component in the main component powder mainly composed of barium titanate is 200 to 322 ppm. Thus, it is possible to stably obtain a dielectric ceramic composition having a high specific dielectric constant and excellent temperature characteristics of capacitance.

  Moreover, since Ca component contains inevitable impurities, the Ca content can be managed accurately.

In addition, since it includes a blending step of blending the main component powder and at least one subcomponent powder such as CaZrO ₃ in a predetermined ratio, the main component powder is not dependent on the Ca content in the subcomponent powder. By simply managing the Ca component, it is possible to easily obtain a dielectric ceramic composition that can stabilize the temperature characteristics and relative dielectric constant of the capacitance and can secure a desired high relative dielectric constant, and produces a variety of products. In this case, it is possible to realize an effective manufacturing method for cost reduction.

It is a diagram showing the relationship between the Ca content and the relative permittivity εr in BaTiO ₃ in the sample No. 1-9. Is a graph showing the relationship between the temperature change rate [Delta] C ₊₈₅ of Ca content and the capacitance in BaTiO ₃ in the sample No. 1-9. It is a graph showing the relationship between the temperature change rate [Delta] C _-25 the Ca content and the capacitance in BaTiO ₃ in the sample No. 1-9. It is a diagram showing the relationship between the Ca variation and the relative dielectric constant εr in CaZrO ₃ in Sample No. 11 to 17. It is a graph showing the relationship between the temperature change rate [Delta] C ₊₈₅ of Ca variation and the electrostatic capacitance in CaZrO ₃ in Sample No. 11 to 17. It is a graph showing the relationship between the temperature change rate [Delta] C _-25 the Ca variation and the electrostatic capacitance in CaZrO ₃ in Sample No. 11 to 17.

  Next, an embodiment of the present invention will be described in detail.

In the dielectric ceramic composition manufactured by the manufacturing method of the present invention, a subcomponent powder is blended with a main component powder containing BaTiO ₃ as a main component.

As the subcomponent powder, various complex oxides such as CaZrO ₃ , SrTiO ₃ , MgTiO ₃ , rare earth oxidation such as Y ₂ O ₃ , Dy ₂ O _3, etc., as needed, from the viewpoint of obtaining desired electrical characteristics according to the application And various oxides such as SiO ₂ and Al ₂ O ₃ can be appropriately selected and used.

Then, the dielectric ceramic composition, Ca content in the main component BaTiO ₃ powder is adjusted to be 200~322ppm including unavoidable impurities.

  That is, the dielectric ceramic composition inevitably contains various impurities. For example, a small amount of Ca component is contained in the ceramic raw material for synthesizing the main component powder and subcomponent powder. It is contained as.

According to the results of the study by the present inventors, a trace amount of Ca component contained in the main component powder, BaTiO ₃ , whereas a trace amount of Ca component in the subcomponent powder hardly affects the electrical characteristics. Has been found to have a significant effect on electrical properties.

Specifically, when the content of the Ca component in the BaTiO ₃ powder is less than 200 ppm, the relative dielectric constant εr tends to decrease and the desired high relative dielectric constant cannot be maintained. On the other hand, when the content of the Ca component in the BaTiO ₃ powder exceeds 322 ppm, there is a possibility that the temperature change rate of the capacitance increases and the temperature characteristics are deteriorated.

Therefore, in this dielectric ceramic composition, the additive amount of the Ca compound is adjusted so that the Ca content in BaTiO _{3 as the} main component powder is 200 to 322 ppm including inevitable impurities.

  Hereinafter, a method for producing a dielectric ceramic composition according to the present invention will be described in detail.

  First, as a ceramic raw material, a Ba compound and a Ti compound are prepared, and an analysis method such as ICP-AES (inductively coupled plasma mass spectrometry) is used, and the content of the Ca component contained in these ceramic raw materials is determined in advance. taking measurement. That is, as described above, these ceramic raw materials usually contain a Ca component as an inevitable impurity, so the content of the Ca component in these ceramic raw materials is measured in advance.

Next, predetermined amounts of the Ba compound, Ti compound, and Ca compound are weighed so that the content of the Ca component contained in the synthesized BaTiO ₃ powder is 200 to 322 ppm.

  Then, the weighed material thus weighed is put into a stirring mill together with a dispersant and pure water, mixed and pulverized to produce a slurry.

The obtained slurry is heated to a predetermined temperature and calcined, and then pulverized in a dry manner to produce a main component powder mainly composed of BaTiO ₃ powder.

  Next, in order to obtain a desired electrical property, a predetermined amount of a predetermined subcomponent powder is weighed and put into a ball mill having PSZ (partially stabilized zirconia) balls inside together with the main component powder, a binder, pure water and the like, Mix and grind to make slurry. And this slurry is dried, Thereby, a dielectric ceramic composition can be obtained.

Thus, according to the present embodiment, the addition amount of the Ca compound is adjusted so that the content of the Ca component in the main component powder containing BaTiO ₃ as a main component is 200 to 322 ppm including inevitable impurities. Therefore, it is possible to stably obtain a dielectric ceramic composition having good temperature characteristics while ensuring a high relative dielectric constant.

  Moreover, since Ca component contains inevitable impurities, the Ca content can always be managed accurately.

In addition, since it includes a blending step of blending the main component powder and at least one subcomponent powder such as CaZrO ₃ in a predetermined ratio, the main component powder is not dependent on the Ca content in the subcomponent powder. In the case of producing various types of dielectric ceramic compositions that can stabilize the temperature characteristics and relative dielectric constant of capacitance and have a desired high relative dielectric constant simply by managing the Ca component It is possible to realize an effective manufacturing method for cost reduction.

  By using this dielectric ceramic composition as a ceramic raw material, a desired multilayer ceramic capacitor or single plate-shaped ceramic capacitor can be obtained.

  The present invention is not limited to the above embodiment. For example, the presence form of Ca may exist in any of the crystal grains, the crystal grain boundaries, and the crystal triple points. Also, the form of the Ba compound, Ti compound, and Ca compound used as the ceramic raw material may be any of carbonate, hydroxide, oxide, and the like, and is not particularly limited.

  Next, examples of the present invention will be specifically described.

BaCO ₃ and TiO ₂ powders were prepared as ceramic raw materials, and the content of Ca component contained in these ceramic raw materials was measured by ICP-AES (inductively coupled plasma mass spectrometry). It was.

Then, the Ca content contained in BaTiO ₃ powder after synthesis BaCO _3, TiO ₂ in predetermined amounts so that 129～400Ppm, and were weighed powders of CaCO _3.

  Next, together with pure water containing a dispersant in advance, this weighed product was put into a medium type stirring mill, and mixed and pulverized to prepare a slurry.

Next, the obtained slurry was dehydrated and dried, and then charged into a rotary tubular furnace heated to a predetermined temperature. The dry powder thrown into the tubular furnace is sent to the central part as the tubular furnace is rotated and calcined. Then, this calcined product was pulverized by a dry method to prepare BaTiO ₃ powder (main component powder), and the Ca content of the BaTiO ₃ powder was measured by ICP-AES.

Next, as a ceramic raw material, CaCO ₃ powder and ZrO ₂ powder are weighed in predetermined amounts, and in the same manner as described above, the weighed product is put into a medium-type stirring mill together with pure water containing a dispersant in advance. A slurry was prepared by grinding. Into a ball mill containing PSZ balls as a grinding medium, a dispersant and pure water were added, mixed and ground to prepare a slurry.

Next, after the obtained slurry was dehydrated and dried, it was put into a rotary tubular furnace heated to a predetermined temperature, calcined in the same manner as described above, and pulverized in a dry manner to prepare CaZrO ₃ powder.

Next, predetermined amounts of BaTiO ₃ powder and CaZrO ₃ powder are weighed so that the molar ratio is 88:12, and further predetermined amounts of MgTiO ₃ powder, Y ₂ O ₃ powder, SiO ₂ powder, and Al ₂ O ₃ powder. Weighed.

Then, the weighed product is put into a ball mill having PSZ balls inside together with pure water containing a binder and the like, mixed and pulverized to produce a slurry, and the slurry is dried. The composition formula (Ba _0.88 Ca _0.12 ) A dielectric ceramic composition represented by (Ti _0.88 Zr _0.12 ) O ₃ was obtained.

  The dielectric ceramic composition was then pressed to produce a molded body, which was fired by holding at a predetermined temperature for 2 hours to obtain a ceramic sintered body having a diameter of 12.5 mm and a thickness of 1.0 mm.

Next, Ag was vapor-deposited on both main surfaces of the obtained ceramic sintered body to form electrodes, and samples Nos. 1 to 9 were produced.
Next, the relative dielectric constant εr at + 20 ° C. was measured for each sample Nos. 1 to 9 using an LCR meter under the conditions of 1 kHz and 1 Vrms.

Further, the ambient temperature is changed in the range of −25 ° C. to + 85 ° C., the relative dielectric constant εr at + 85 ° C. and −25 ° C. is obtained, and the capacitances C ₊₈₅ and C ₋₂₅ are respectively calculated from the sample dimensions. Based on the following formulas (1) and (2), capacitance temperature change rates ΔC ₊₈₅ and ΔC _-25 based on + 20 ° C. were obtained.

ΔC ₊₈₅ = (C _{+ 85 ° C.−} C _{20 ° C.} ) / C _{20 ° C.} × 100 (1)
ΔC ₋₂₅ = (C _{−25 ° C.−} C _{20 ° C.} ) / C _{20 ° C.} × 100 (2)
Table 1 shows the Ca content, relative dielectric constant εr, and capacitance temperature change rate ΔC ₊₈₅ , ΔC _-25 in BaTiO ₃ .

In Sample Nos. 6 and 7, the Ca content in BaTiO ₃ is as low as 129 ppm and 150 ppm, respectively, so that the temperature change rates ΔC ₊₈₅ and ΔC _-25 of the capacitance are good, but the relative dielectric constant εr is 7500 or less. It has dropped to.

On the other hand, Sample Nos. 8 and 9 have an excessive Ca content in BaTiO _{3 of} 357 ppm and 400 ppm, respectively. Therefore, although the relative permittivity is high, the temperature change rate ΔC _{+85 of the} capacitance is −55.0. %, -55.9%, the fluctuation range is large, and the temperature characteristics are deteriorated.

On the other hand, sample Nos. 1 to 5 have a Ca content in BaTiO _{3 of} 200 to 322 ppm, which is within the range of the present invention. Therefore, a high relative dielectric constant of 7500 or more can be secured, and the capacitance changes with temperature. The ratios ΔC ₊₈₅ and ΔC _-25 are also within the allowable range of −38.0% to −53.5%, and it was found that good temperature characteristics can be obtained.

FIG. 1 is a graph showing the relationship between the Ca content in BaTiO ₃ and the relative dielectric constant εr in sample numbers 1 to 9, with the horizontal axis representing the Ca content (ppm) and the vertical axis representing the relative dielectric constant εr.

2 and 3 are diagrams showing the relationship between the Ca content in BaTiO ₃ and the temperature change rates ΔC ₊₈₅ and ΔC ₋₂₅ of Sample Nos. 1 to 9, with the horizontal axis representing the Ca content. The amount (ppm) and the vertical axis are the temperature change rates ΔC ₊₈₅ and ΔC _-25 (%) of the capacitance.

As apparent from FIGS. 1 to 3, by adjusting the Ca content in BaTiO ₃ to 200 to 322 ppm, the variation ranges of the capacitance temperature change rates ΔC ₊₈₅ and ΔC ₋₂₅ (%) are reduced. It was possible to obtain a dielectric ceramic composition capable of maintaining a high relative dielectric constant of 7500 or higher while suppressing it.

A BaTiO ₃ powder having a Ca content of 257 ppm prepared in Sample No. 3 of Example 1 was prepared.

Next, the CaZrO ₃ powder prepared in Example 1 is prepared, and further MgTiO ₃ powder, Y ₂ O ₃ powder, SiO ₂ powder, and Al ₂ O ₃ powder are prepared, and the same method and procedure as in Example 1 are used. A sample No. 15 represented by the composition formula (Ba _0.88 Ca _0.12 ) (Ti _0.88 Zr _0.12 ) O ₃ was obtained.

Further, by changing the amount of CaZrO ₃ added, the mixing ratio of BaTiO ₃ powder and CaZrO ₃ powder is changed, and the Ca molar ratio of 0.12 is different from the range of -726 ppm to +364 ppm with respect to the Ca molar ratio of 0.12. Samples No. 11 to 14, 16, and 17 were prepared.

Then, as in [Example 1], relative permittivity εr and capacitance temperature change rates ΔC ₊₈₅ and ΔC _-25 were obtained.

Table 2 shows the amount of variation of Ca in CaZrO ₃ and the measurement results.

FIG. 4 is a graph showing the relationship between the Ca fluctuation amount of CaZrO ₃ and the relative dielectric constant εr in Sample Nos. 11 to 17, where the horizontal axis is the Ca fluctuation amount (ppm), and the vertical axis is the relative dielectric constant εr. .

5 and 6 are graphs showing the relationship between the Ca fluctuation amount of CaZrO ₃ and the temperature change rates ΔC ₊₈₅ and ΔC ₋₂₅ of Sample Nos. 11 to 17, and the horizontal axis represents the Ca content. Δα (ppm), and the vertical axis represents capacitance temperature change rates ΔC ₊₈₅ and ΔC _-25 (%).

As is apparent from Table 2 and FIG. 4, if the Ca content in BaTiO ₃ is constant (257 ppm), the relative dielectric constant εr even if the Ca of CaZrO ₃ varies in the range of about −700 ppm to 350 ppm. It was found that 7500 or more can be secured.

Further, as is clear from Table 2 and FIGS. 5 and 6, if the Ca content in BaTiO ₃ is constant (257 ppm), even if the Ca of CaZrO ₃ fluctuates in the range of about −700 ppm to 350 ppm, the temperature It was found that the fluctuation range of the change rate was relatively stable at −37.5 to −54.3%.

As is clear from the above-mentioned [Example 1] and [Example 2], the BaTiO ₃ based dielectric ceramic composition can ensure a high relative dielectric constant and has a stable temperature characteristic of capacitance. to the things, it was confirmed to adjust the addition amount of Ca component contained in the main component BaTiO ₃ powder 200~322ppm is effective.

In a dielectric ceramic composition containing BaTiO ₃ as a main component powder and subcomponent powders added, by adjusting the content of Ca component in BaTiO ₃ to 200 to 322 ppm, a high relative dielectric constant and good temperature characteristics To ensure a stable.

Claims (5)

In a method for manufacturing a dielectric ceramic composition comprising a main component powder preparation step of preparing a main component powder mainly composed of barium titanate by preparing a plurality of ceramic raw materials containing a barium compound and a titanium compound,
The main component powder preparation step includes an addition amount adjusting step of adjusting the addition amount of the calcium compound so that the content of the calcium component in the main component powder is 200 to 322 ppm. Manufacturing method.   The method for producing a dielectric ceramic composition according to claim 1, wherein the calcium component contains inevitable impurities.   The said main component powder preparation process includes the calcining process of calcining the preparation of the said barium compound and the said titanium compound, and the said calcium compound added at the said addition amount adjustment process, The characterized by the above-mentioned. A method for producing a dielectric ceramic composition according to claim 2.   The production of the dielectric ceramic composition according to any one of claims 1 to 3, further comprising a blending step of blending the main component powder and at least one or more subcomponent powders in a predetermined ratio. Method. Wherein the auxiliary component powder, a manufacturing method of claim 4 dielectric ceramic composition, wherein the containing CaZrO _3.

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