DE19902151A1 - Dielectric ceramic for a laminated ceramic electronic element e.g. a miniature capacitor - Google Patents

Abstract

A dielectric ceramic, obtained by firing a barium titanate powder having a perovskite structure with a c-axis/a-axis ratio of 1.003-1.010 and an OH group content of <= 1 wt.% in its crystal lattice, is new. Independent claims are also included for the following: (i) production of a dielectric ceramic by firing the barium titanate powder described above; (ii) a laminated ceramic electronic element with an internal conductor between two adjacent layers of the above dielectric ceramic; and (iii) a process for producing the above laminated ceramic electronic element.

Description

The present invention relates to a dielectric ceramic, which advantageously in a laminated ceramic electronic element is used, such as. B. in one Laminated ceramic capacitor, which has an inner conductor made of a base metal or base metal, e.g. B. nickel or a nickel alloy, and it relates to a method for producing the dielectric ceramic. The present The invention also relates to a laminated ceramic electronic element resulting from the dielectric ceramic is formed, and a method for producing the same.

Miniaturization and cost reduction in laminated ceramic elec tronic elements continues to advance. For example, in such a ke Raman electronic element has been thinned a ceramic layer, and a base Metal has been used as an inner conductor. In the case of a laminated ceramic capacitor, which is a kind of a laminated ceramic electronic element a dielectric ceramic layer is only about 3 µm thin, and a base metal such as B. Cu or Ni is as a material for producing a Inner conductor, e.g. B. an inner electrode has been used.

But when the ceramic layer becomes thin, the strength of an electric field increases which is applied to the layer, causing a problem in use  dielectric caused as a ceramic layer, which makes a big change which shows dielectric constants induced by an electric field. A reduction in the size of the ceramic grains in the thickness direction of the ceramic layer also causes a reliability problem.

In order to cope with such situations, there are Japanese patents reporting disclosure documents (kokai) of numbers 9-241074, 9-241 075, etc., Ceramic materials have been proposed that have improved reliability by increasing the size of the ceramic grains in the thickness direction of the allow dielectric ceramic layer. Consequently, the control of the grain allows size of the ceramic grains a reduction in the change in dielectric constant ate that is induced by an electric field or temperature.

But when in the prior art described above, the thickness of a dielectric ceramic layer is about 1 µm or less, the fluctuation of the Temperature / Dielectric constant characteristics, although the Reliable is maintained, which makes it difficult to produce products with a stable temperature rature / dielectric constant characteristics with high reproducibility to obtain. To stable temperature / dielectric constant characteristics ensure, the field strength must be reduced and the nominal voltage of the The resulting laminated ceramic electronic elements must be reduced the. That is why the realization of a thin layer with a thickness of only 1 µm or less difficult or even impossible as long as the state described above technology is used to solve this problem.

In view of the above, the present invention is based on a dielectric Ceramic, which is advantageously in a laminated ceramic electronic element is used, which is a thin ceramic layer with a thickness of only 1 µm or less, and a method of manufacturing the dielectric ceramic aligned. The present invention is also based on a laminated ceramic  Electronic element, which is made of the dielectric ceramic, and on a Process for producing the same.

In one embodiment of the present invention is a dielectric ceramic provided which is obtained by firing barium titanate powder, which has a perovskite structure in which a ratio of the c-axis to the a-axis (hereinafter referred to as the c-axis / a-axis ratio) in the perovskite structure in the Range is 1.003 to 1.010, and an amount of OH groups in the crystal lattice is 1% by weight or less.

In another embodiment of the present invention, a method for Manufacture of the dielectric ceramic provided, the process following the steps include: providing the above barium titanate powder in which the c-axis / a-axis ratio in the perovskite structure in the range of 1.003 is up to 1.010 and an amount of OH groups in the crystal lattice is 1% by weight or is less, and the burning of the barium titanate powder.

The amount of OH groups is based on the loss at 150 ° C or more determined, which is measured during the thermogravimetric analysis of the test specimens becomes.

The barium titanate powder preferably has a maximum particle size of 0.5 µm or less and an average particle size of 0.1-0.3 µm.

In addition, each particle of the barium titanate powder described above preferably comprises a portion with a low crystallinity and a portion with a high crystallinity, the diameter of the portion with the low crystallinity being less than 0.65 times the particle size of the powder. As shown in Fig. 2, which is a transmission electron micrograph of barium titanate powder, and shown in Fig. 3, which is an explanatory sketch thereof, the term "portion 21 having a low crystallinity" as used herein refers to a domain, which a number of lattice defects such. B. has a cavity 22 , whereas the term "section 23 with a high crystallinity" used here refers to a domain that has no such lattice defects.

So if the ratio (average grain size of the fired dielectri ceramics) / (average particle size of the intended barium titanate Powder) is embodied by R, R preferably falls in the range of 0.90-1.2.

Grains that form the dielectric ceramic of the present invention can be one Core-shell structure, in which the composition and the crystal system the core and the shell differ from each other, or a homogeneous structure have a uniform composition and a uniform crystal sy stem has.

The term "crystal system" used here refers to a crystal system of Perovskite crystals, d. H. on a cubic system with a c-axis / a-axis Ratio in the perovskite structure from 1 or to a tetragonal system with ei A c-axis / a-axis ratio in the perovskite structure of 1 or more.

In yet another embodiment of the present invention is a lami Ceramic electronic element is provided, which is a laminate (laminate), which is formed from a plurality of ceramic layers, and an inner conductor summarizes the along a special transition point between adjacent dielectri ceramic layers is formed.

Especially in the present invention, the dielectric ceramic layer that is in the laminated ceramic electronic element is contained by a dielectri ceramics formed by burning barium titanate powder which has a perovskite structure in which a c-axis / a-axis ratio in the perovskite structure is in the range of 1.003 to 1.010 and an amount OH groups in the crystal lattice is 1% by weight or less.  

Included in the laminated ceramic electronic element described above the inner conductor preferably a base metal such as. B. nickel or a nickel alloy tion.

The laminated ceramic electronic element can also have a variety of Au have external electrodes at different locations on one side surface. In this case the inner conductors are designed in such a way that one end of each inner conductor faces the side surface che exposed, so that he is electrically connected to one of the outer electrodes that can. Such a structure is typically used in laminated ceramic Capacitors used.

In yet another embodiment of the present invention, there is a method ren intended for producing a laminated ceramic electronic element, the method comprising the steps of providing a barium titanate Powder with a c-axis / a-axis ratio in the perovskite structure in the Range is 1.003 to 1.010 and an amount of OH groups in the crystal lattice Is 1% by weight or less; Manufacture of a laminate in which a variety of ceramic green sheets that contain the barium titanate powder included, and inner electrodes are layered (laminated) so that the inner electrodes along certain transition points of the ceramic green foils are; and firing the barium titanate powder to thereby form a dielectric core ramic.

Various other tasks, features and many of those with the present inven The associated benefits will become apparent from the detailed description that follows of the preferred embodiments clearly when related to be considered in the accompanying drawings. Show it:

Fig. 1 is a cross sectional view of a laminated ceramic capacitor 1 according to an embodiment of the present invention,

Fig. 2 is a transmission electron microscope image of a barium titanate powder, which is provided for the production of a dielectric ceramic according to the present invention, and

Fig. 3 is an explanatory sketch of the electron microscope image shown in Fig. 2.

The barium titanate powder used in the present invention has a composition represented by the following formula: (Ba _1-x X _x ) _m (Ti _1-y Y _y ) O ₃ . The composition is not particularly limited. X can include Ca, individual types of rare earth metals, and a combination of two or more of them. Y can single types such. B. Zr or Mn and a combination of two or more types thereof. In general, m is preferably 1,000-1,035, depending on the composition of the barium titanate powder, in order to obtain a non-reducing dielectric ceramic.

The barium titanate powder which is suitably used has a pe rowskit structure with a c-axis / a-axis ratio in the range of 1.003 up to 1.010. In addition, the amount of OH groups in the crystal grid is ter 1 wt .-% or less, a maximum particle size is 0.5 microns or less ger, and an average particle size is 0.1-0.3 microns. Such a bari Umtitanat powder can he by a heat treatment of the barium titanate powder will hold, which is produced by a wet synthesis process, such as. B. a Hydrothermal synthesis process, a hydrolysis process, or a sol-gel process Ren. A solid phase method can also be used for the synthesis, at a carbonate, an oxide, etc. of the elements that make up the barium titanate powder, be mixed and heat treated.

In the heat treatment described above, the conditions for moderate grain growth are selected so that a c-axis / a-axis ratio of 1.003 to 1.010 is realized. For example, effective heat treatment can be performed in an atmosphere containing H ₂ O. Of course, the above range can be maintained by appropriately setting the temperature and the duration of the heat treatment. If a solid phase method is used, the disintegration conditions must be checked since the c-axis / a-axis ratio could decrease depending on the conditions for the disintegration of the synthesized powder.

The diameter ratio of the low crystallinity section 21 , that is, a ratio of the diameter of the low crystallinity section 21 to the particle size of the powder after the heat treatment described above, is predetermined to be less than 0.65 in each particle of the one shown in FIG. showed 3 ge 2 and FIG. barium titanate powder is. Such a diameter ratio can be obtained by heat treatment at a temperature increase rate of 1 ° C / min or less.

The relationship between the average particle size of the thus obtained Barium titanate powder and the average grain size of the fired dielectri ceramics, d. H. the ratio of (average grain size of the burned Ceramic) / (average particle size of the intended barium titanate pulp vers) represented by R is preferably 0.09-1.2. In short, a be Pregnant grain growth is preferred to be generated during sintering the ceramic materials prevented. For example, a Mn component and / or a Mg component, a sintering aid based on Si, etc. added to the barium titanate powder. In general, these additives the barium titanate powder in the form of oxide powder or carbonate powder beige be mixed. Alternatively, a method can be used in which the Barium titanate powder is coated with a solution containing these additives, and then heat treated.  

This barium titanate powder is fired to thereby produce a dielectric ceramic that is used in a laminated ceramic electronic element, e.g. B. in a laminated ceramic capacitor 1 , as is illustrated in Fig. 1 light.

As shown in Fig. 1, the laminated ceramic capacitor 1 comprises a laminate 3 containing a plurality of laminated dielectric layers 2 , and a first outer electrode 6 and a second outer electrode 7 , each on a first side surface 4 and a second Side surface 5 of the laminate 3 are provided. The laminated ceramic capacitor 1 in its entirety forms a rectangular, parallelepiped-shaped chip-like electronic element.

In the laminate 3 , first inner electrodes 8 and second electrodes 9 are alternately arranged as the inner conductors. The first inner electrodes 8 are formed along special transition points between dielectric ceramic layers 2 such that one end of each inner electrode 8 is exposed to the first side surface 4 of the laminate 3 so that it can be electrically connected to the first outer electrode 6 , while the second Inner electrodes 9 are formed along special transition points between the dielectric ceramic layers 2 such that one end of each inner electrode 9 to the second side surface 5 of the layer 3 is exposed so that it can be electrically connected to the second outer electrode 7 .

In the laminated ceramic capacitor 1 , the dielectric ceramic layers 2 contained in the laminate 3 include the above-mentioned dielectric ceramic.

To produce the laminated ceramic capacitor 1 , starting materials are provided which have a primary component such as e.g. B. barium titanate and an additive to improve the characteristics, etc., include. The materials are weighed in predetermined amounts and wet mixed to form a mixed powder.

Then, an organic binder and a solvent are added to the mixed powder to thereby give a slurry, and a ceramic green sheet forming the dielectric ceramic layer 2 is produced using the slurry.

Thereafter, electrically conductive thin paste films, which form the inner electrodes 8 and 9, are formed on the special ceramic green sheets. The conductive paste film contains a base metal such as nickel or copper, or an alloy thereof, and is made by a method such as e.g. B. screen printing, vapor deposition, or plating.

A variety of ceramic green sheets, including those on which a paste paste film has been formed as described above, are layered, pressed and, if necessary, cut to size. Thus, a green laminate 3 is produced in which the ceramic green sheets and the inner electrodes 8 and 9 , which are formed along special transition points between the ceramic green sheets, are laminated, with one end of each of the inner electrodes 8 and 9 toward the side surface 4 and 5 , respectively is open.

The laminate 3 is then fired in a reducing atmosphere in order to be converted into a dielectric ceramic by the barium titanate powder. In this step, the grain size ratio R described above is controlled so that it falls in the range of 0.90 ≦ R ≦ 1.2.

The first outer electrode 6 and the second outer electrode 7 are each formed on the first side surface 4 and on the second side surface 5 of the laminate 3 so that they are in the fired laminate 3 with the exposed ends of the first inner electrodes 8 and the second inner electrodes 9 get in touch.

No special restrictions are imposed on the composition of the materials for producing the outer electrodes 6 and 7 . Above all, the same materials can be used as for the inner electrodes 8 and 9 . The Außenelek electrodes can also be constructed from a sintered layer, the an electrically conductive metal powder, such as. B. comprises a powder of Ag, Pd, Ag-Pd, Cu, or a Cu alloy, or of a sintered layer comprising the above conductive metal powder mixed with earth glass ("glass frit"), such as e.g. B. B ₂ O ₃ -Li ₂ O-SiO ₂ - BaO, B ₂ O ₃ -SiO ₂ -BaO, Li ₂ O-SiO ₂ -BaO or B ₂ O ₃ -SiO ₂ -ZnO. The composition of the materials for producing the outer electrodes 6 and 7 is determined in an appropriate manner taking into account factors that affect the laminated ceramic capacitor 1 , such as. B. use or the environment for use.

As has been described above, the outer electrodes 6 and 7 can be formed by applying the metal powder paste which forms them to the fired layer 3 and firing them. The electrodes can also be formed by bringing the paste onto the unfired laminate 3 and can be fired simultaneously with the firing of the laminate 3 .

The outer electrodes 6 and 7 can be coated with application layers 10 and 11 , which are formed from Ni, Cu, a Ni-Cu alloy, etc., depending on the requirements. The application layers 10 and 11 can also be coated with second application layers 12 and 13 , each of which is formed by a solder, tin, etc.

The present invention will now be described in more detail by way of examples, but this should not be construed as a limitation of the invention.

Examples

The laminated ceramic capacitor manufactured in this example is a laminated ceramic capacitor 1 having a structure as shown in FIG. 1.

Different barium titanate materials with compositions as shown in Table 1 were made by hydrolysis. The resulting alpine powders have a particle size of 50 to 70 nm and a cubic structure that contains many OH groups in the lattices of the perovskite structure. By heat treatment of these materials under a variety of conditions, e.g. B. in an atmosphere containing H ₂ O, were barium titanate powders A to N with different "c / a" values (c-axis / a-axis ratio), average particle sizes, maximum particle sizes, amounts of OH -Groups, and diameter ratios. Aggregations generated during the heat treatment were disassembled after the heat treatment.

Table 1

The "c / a" values shown in Table 1 were determined by X-ray diffraction from the Bari umtitanate powder determined. That is, the Er obtained by X-ray diffraction Results were made using an X-ray profile fitting subjected to a Rietveld analysis to precisely determine the lattice constants. The average particle size and the maximum particle size were determined by Viewing the barium titanate powder under a scanning electron microscope measure up. An amount of OH groups was determined by a loss weight at a tem temperature of 150 ° C or higher, measured by thermogravimetry of the barium titanate powder was measured.

The diameter ratio shown in Table 1 is a ratio of the Diameter of the portion with a low crystallinity to the particle size of the powder and was determined by cutting the powder was subjected so as to obtain a thin film sample, and under a trans mission electron microscope was considered. If the film-like sample of the Pul verse is produced by a cutting process, the particle size of the Powder and the diameter of a portion of low crystallinity in the powder ver. Because a section with low crystallinity is not always on average point of a powder particle, the size of the section with the deviation be measured by the interface when manufacturing the thin film depends. Thus, particles were selected for the measurement that have a particle size which was similar to the particle size used with the scanning electron micro skop has been observed. The diameter ratio was determined by measuring  of 10 or more such particles and calculating the average Diameter ratio determined.

In the "BaTiO ₃ powder" column in Table 1, the value "x" of the materials (Ba _1-x Ca _x ) _m TiO ₃ for powders A to H is 0.00, so that powders A to H are none Contain Ca, but powders I through N contain Ca because their "x" values are 0.05 and 0.10, respectively.

As additives to be added to the barium titanate powders shown in Table 1, those having the compositions shown in Tables 2 and 3 were provided. Especially with regard to samples Nos. 1 to 17, which are shown in Table 2, RE (RE stands for an element from the group Gd, Dy, Ho and Er), Mg and Mn were provided as additives which the BaTiO _{3 were added} in the form of one of the above samples A to H. A sintering aid containing Si as a primary ingredient has also been provided. Regarding the samples of Nos. 18 to 29 shown in Table 3, Mg and Mn were provided as additives that added to the (Ba _1-x Ca _x ) TiO ₃ in the form of one of the above samples I to N. should be. A sintering aid containing (Si, Ti) -Ba as a primary component has also been provided.

Table 2

Table 3

The additives shown in Tables 2 and 3, respectively, were converted into alkoxide compounds which are soluble in an organic solvent, and then they were added to the barium titanate powders which had been dispersed in an organic solvent. Especially with regard to samples Nos. 1 to 17, the respective additives were added to the barium titanate powders in such a way that "α", "β", "γ" and the "Si-containing sintering aid", all based on molar proportions, in "(Ba _1-x Ca _x ) TiO ₃ + Mg + γMn" as shown in Table 2. In view of the samples of the numbers 18 to 29, the respective additives were added to the barium titanate powders such that "β", "γ" and the "(Si, Ti) -Ba-containing sintering aid", all on the Base of molar proportions in "(Ba _1-x Ca _x ) TiO ₃ + βMg + γMn" as shown in Table 3.

To dissolve the above additives in an organic solvent these can be converted into alkoxides as described above, or they can be converted to acetylacetonates or metal soap.

The resulting slurries underwent evaporation of the organic solvent subjected to dryness and further heat treatment to thereby to remove the organic components.

After that, each sample was given the barium titanate powder containing the respective additives have been added, a polyvinyl butyral binder and an organic solvent means such. B. ethanol was added and the ingredients were wet ground subjected to a ceramic pulp. The porridge thus obtained became un ter using a squeegee formed into a sheet, thereby forming a rectangular To obtain green film with a thickness of 1.5 microns. Then was received on the ceramic green sheet is a conductive paste that contains Ni as a primary component held, applied by printing, to form a conductive paste film Form internal electrodes.

Thereafter, a plurality of the ceramic green sheets thus obtained were laminated such that the front ends of the above-mentioned conductive paste films were alternately arranged on the sheets to thereby obtain a laminate. The resulting laminate was heated at 350 ° C in an N ₂ atmosphere so as to burn the binder, and then at a temperature as shown in Table 4 in a reducing atmosphere of H ₂ -N ₂ for two hours -H ₂ O gas burned at an oxygen partial pressure of 10 ^-9 to 10 ^-12 MPa.

A silver paste containing B ₂ O ₃ -Li ₂ O-SiO ₂ -BaO earth glaze was applied to the opposite side surfaces of the fired laminate, followed by firing in a nitrogen atmosphere at 600 ° C to obtain external electrodes which were electrically connected the internal electrodes are connected.

The outer size of the resulting laminated ceramic capacitor was 5.0 mm in width, 5.7 mm in length and 2.4 mm in thickness, and the thickness of the dielectric ceramic layer existing between the inner electrodes was 1 µm. The total number of effective dielectric ceramic layers was five, and the area of the opposing electrodes per layer was 16.3 × 10 ^-6 m ² .

The electrical properties of the resulting samples were as follows measured.

The electrostatic capacitance (C) and the dielectric loss (tanδ) were below Use of an automatic bridge instrument according to JIS (Japanese Indu strienorm) 5102, and the dielectric constant (ε) was determined using determination of the electrostatic capacity obtained.

An insulation tester was used to measure the insulation resistance (R) det; by applying 10 V DC for two minutes at 25 ° C Insulation resistance (R) was obtained, and the specific electrical resistance was calculated.

As for the rate of change in electrostatic capacity with respect to the temperature change, the rate of change (ΔC / C ₂₀ ) is in a range from -25 ° C to + 85 ° C with reference to the electrostatic capacity at 20 ° C and the am rate of change (ΔC / C ₂₅ ) in a range from -55 ° C to + 125 ° C with reference to the electrostatic capacity at 25 ° C shown.

In a high-temperature load test, the change in the time course of the insulation resistance was measured when 10 V direct current was applied at 150 ° C. In this test, the average life of the samples was calculated, and the life of a sample was considered equal to the time to breakdown when the insulation resistance (R) of each sample fell to 10 ⁵ Ω or less.

The breakdown voltage was measured using a DC voltage at a voltage increase rate of 100 V / sec. was created.

An average grain size of the dielectric ceramic obtained in the Laminated ceramic capacitor is included by chemical etching of polished cross-sectional areas of the laminate and the consideration of the surface Chen obtained under a scanning microscope. By using the results and the average particle sizes of the starting raw materials described in Ta belle 1, a ratio R, i. H. (average grain size of the dielectric ceramic) / (average particle size of the raw material i en) measured.

The results are shown in Table 4.  

Table 4

The dielectric ceramic of the present invention is characterized by the following marked times. First, it is obtained by burning barium titanate powder which has a perovskite structure in which a c-axis / a-axis ratio in the perovskite structure is in the range of 1.003 to 1.010 and an amount of OH groups in the crystal lattice is 1% by weight or less. Preferably be the barium titanate powder that serves as the raw material sits a maximum part size of 0.5 µm or less and an average particle size of 0.1 to 0.3 µm. Also include individual particles of the barium titanate powder preferably a section with a low crystallinity and a section with high crystallinity in each particle, and the diameter of the section with the low crystallinity is less than 0.65 times the particle size of the pul verse. In addition, a ratio R, i.e. H. (average grain size of the dielectri ceramics) / (average particle size of the barium titanate powder) 0.90 to 1,2, so that no significant grain growth during the sintering of the ceramic occurs.

The sample numbers marked with * in Table 4 and the powders marked marked with * in Table 1 are outside the scope of the present Er invention or the preferred ranges listed above.  

First of all, a transmission electron microscope analysis showed a ge fired ceramics with respect to the samples numbered 1 to 17 shown in Table 4 are shown and obtained by using one of the raw material powders A to H. shown in Table 1 that near the grain boundary of a ceramic korns the rare earth metal (RE), such as B. Gd, Dy, Ho or Er, is diffused and egg has formed a shell portion; and was in the center of the ceramic grain a core section is formed; d. that is, the fired ceramic takes one in each grain Core-shell structure, in which the core and the shell different together have settings and crystal systems.

As can be seen from the data of Sample No. 1 in Table 4, the use is a material powder with a c-axis / a-axis ratio in the perovskite structure less than 1.003, e.g. B. the material powder A shown in Table 1, not advantageous because the reactivity of an additive is excessively high, which is unpredictable partly to an enlarged grain size of the sintered ceramic and egg an increased variation in the temperature / dielectric constant characteristics ken leads.

As is clear from the data of Sample No. 15 in Table 4, the use of a Material powder with a c-axis / a-axis ratio of more than 1.010, such as. B. the material powder F shown in Table 1, not preferable because the reactivity with an additive is bad, so that the average lifespan it shortens and, moreover, the reliability deteriorates in a disadvantageous manner Way, when the dielectric ceramic layers are thinned, as in the case of this example.

Even if the c-axis / a-axis ratio of the material powder is 1.003-1.010 is and the amount of OH groups is 1 wt .-% or less, demon data of Sample No. 16 in Table 4 show that when a powder with a average particle size of more than 0.3 microns is used, such as. B. that Material powder G listed in Table 1, the average lifespan relative  can be short, and also the reliability can be disadvantageous are deteriorated if the dielectric ceramic layers are made thinner as in the case of this example.

Similarly, the data of Sample No. 17 in Table 4 show even in the case in which the c-axis / a-axis ratio and the amount of OH groups of matter fall into the areas of the present invention described above, clearly that if a material powder with a maximum particle size of more than 0.5 µm is used, such as. B. the material powder H, the ge in Table 1 shows is the average lifespan can be relatively short and if the di electrical ceramic layers can be made thinner, which can be reliable disadvantageously worsen.

Even in the cases of material powders C, D and E in Table 1 where the c-axis / a-axis ratio of the material powder is 1.003-1.010, the amount OH groups is 1% by weight or less, the maximum particle size is 0.5 mm or less, and the average particle size is 0.1-0.3 µm, as from the data of Sample Nos. 4, 9 and 11 (where R is less than 0.90) or Sample Nos. 8 and 14 (where R is greater than 1.2) in Table 4 the temperature-dependent fluctuation in the dielectric constant climb.

Although for Sample Nos. 5, 6, 7, 10, 12 and 13 shown in Table 4, the In contrast, the thickness of the dielectric ceramic layer is only 1 µm thin the rate of change of electrostatic capacity with temperature caused by the JIS specifications set B characteristics in the range from -25 ° C to + 85 ° C, and fulfills the X7R characteristics, which are defined by the EIA specifications (EIA = Electronic Industries Association) are set in the range from -55 ° C to + 125 ° C. In addition, the samples can last for 70 hours or more until it breaks down in a high temperature stress test, and they can be sintered at 1200 ° C or less. The change in electrostatics  capacity when applying a DC voltage is small and can therefore ensure a high voltage rating.

The fired ceramics of Sample Nos. 18 to 29 listed in Table 4 and using the material powders I to N listed in Table 1 were kept under a transmission electron microscope analysis pulled. It was confirmed that compositional and unevenness a non-uniform crystal system, such as that of individual ceramic grains in combination 1 to 17 were not observed.

If a material is used that has a c-axis / a-axis ratio of the Perows kit structure less than 1.003, such as. B. the material powder J, which in Ta belle 1 is shown, the temperature characteristics of the dielectric con constant increase, as can be seen from the data of the sample No. 22 and 23 in Table 4 becomes. This increase occurs regardless of the degree of grain growth during the Burning on as from the comparison of the ratio R of Sample No. 22 and of sample No. 23 becomes clear.

As is clear from the data of Sample No. 27 shown in Table 4, the ver use of a material powder with a c-axis / a-axis ratio of more than 1.010, such as B. the material powder L in Table 1, not advantageous in view of not satisfactory temperature / dielectric constant characteristics of the kur zen average lifespan and poor reliability.

Even in the case of the material powders I and K of Table 1, in which the c-axis / a- Axis ratio of the material powder is 1.003-10.010, the amount of OH group pen is 1% by weight or less, the maximum particle size is 0.5 µm or less ger, and the average particle size is 0.1-0.3 µm, show the Data of Sample Nos. 18 and 24 (where R is less than 0.90) or the Sample No. 21 (where R is greater than 1.2) in Table 4 clearly shows that a swan  dielectric constant can increase depending on whether the R is less than 0.90 or greater than 1.2.

So even if the c-axis / a-axis ratio of the material powder Is 1.003-1.010 and the amount of OH groups is 1% by weight or less, zei the data of Sample No. 28 in Table 4 that when a powder is used is that an average particle size of more than 0.3 microns and a maxi male particle size of more than 0.5 microns, such as. B. the material powder M As shown in Table 1, the temperature / dielectric constant characteristics may not be satisfactory, the average lifespan is relatively short can be, and also when the dielectric ceramic layers thin ner be designed, the reliability can deteriorate disadvantageously.

As is clear from Example No. 29 in Table 4, when the mate rial powder N shown in Table 1, in which each particle of Barium titanate powder has a low crystallinity section with a Has a diameter of not less than 0.65 times the particle size of the powder, deteriorate the temperature / dielectric constant characteristics.

In contrast, the rate of change in electrostatic capacity also complies with the temperature with reference to Sample Nos. 19, 20, 25 and 26 described in Ta belle 4 are shown, B characteristics determined by the JIS specifications are in the range of -25 ° C to + 85 ° C, and meets the X7R characteristics that specified by the EIA specifications, in the range from -55 ° C to + 125 ° C, although the thickness of the dielectric ceramic layer is only 1 µm thin. Furthermore can last for 70 hours or more until a breakdown in a high temperature stress test occurs, and the samples can be Temperature of not higher than 1200 ° C. The change in elec trostatic capacity when applying a DC voltage is small, and one high voltage rating can be guaranteed.  

As mentioned above, even if the grains are dielectric Ceramic has a homogeneous composition and a uniform crystal system each particle - namely when the grains do not have core-shell Having structure - controlling grain growth during sintering dielectric ceramic with excellent temperature / dielectric constant character produce characteristics and high reliability, as is the case with sample no. 19, 20, 25 and 26 is the case.

The example described above is on a laminated ceramic electronic element ment directed in the form of a laminated ceramic capacitor; but also in that Case of other laminated ceramic electronic elements, such as. B. a lot layered ceramic substrate made by almost the same process As confirmed, the same results were achieved.

As described above, the dielectric ceramics are the present invention an excellent temperature / dielectric constant character tics and improved reliability realized by the c-axis / a-axis Ratio in the perovskite structure and the amount of OH groups in the crystal grid can be controlled, and preferably by further controlling the maximum Particle size, the average particle size, the structure of the powder particles based on the crystallinity and grain growth during the firing of the Barium titanate powder, which serves as the starting material.

Consequently, by using the dielectric ceramic, the present Invention a laminated ceramic high-performance electronic element with a excellent temperature / dielectric constant characteristics and high reliability be preserved. Especially when the dielectric ceramic is used for one Laminated ceramic electronic element is used, which is a laminate includes, in which dielectric ceramic layers and internal electrodes on one another are layered, e.g. B. in a laminated ceramic capacitor, the Temperature / dielectric characteristics can be stabilized even if one  thin ceramic layer with a thickness of about 1 micron or less, and follow Lich this is advantageous for the miniaturization and the thinner design of the laminated ceramic electronic elements.

When making the dielectric ceramic by firing in one cut The ceramic is not reduced to the atmosphere during firing. Therefore The laminated ceramic electronic element of the present invention allows the made using the dielectric ceramic, using a base metal, such as. B. nickel or a nickel alloy as the material for the Inner conductor to reduce the cost of a laminated ceramic electronics ment, e.g. B. a laminated ceramic capacitor.

The dielectric ceramic according to the present invention looks excellent nete temperature / dielectric constant characteristic and an excellent Reliability before, regardless of whether it has a core-shell structure has or not. Therefore, the temperature characteristics and the zuver casualness if the dielectric ceramic does not have a core-shell structure does not suffer from the state of dispersion of an additional ingredient, whereby the variation of the characteristics with the firing conditions is reduced is set.

Claims (30)

1. Dielectric ceramic, characterized in that it is obtained by firing a barium titanate powder in which a c-axis / a-axis ratio in the perovskite structure is in the range of 1.003 to 1.010 and an amount OH groups in the crystal lattice are 1% by weight or less. 2. Dielectric ceramic according to claim 1, characterized in that the Barium titanate powder has a maximum particle size of 0.5 µm or less and has an average particle size of 0.1-0.3 µm. 3. Dielectric ceramic according to claim 1, characterized in that the individual particles of the barium titanate powder a section with a low gene crystallinity and a portion with a high crystallinity and the diameter of the portion with the low crystallinity is less than 0.65 times the particle size of the powder.   4. Dielectric ceramic according to claim 1, characterized in that a Ratio R, which is the (average grain size of the dielectric Kera mic) / (average particle size of the intended barium titanate Powder) is defined, is in the range of 0.90-1.2. 5. Dielectric ceramic according to claim 1, characterized in that the Grains that form the dielectric ceramic have a core-shell structure point in the composition and the crystal system of the core and distinguish the shell from each other. 6. Dielectric ceramic according to claim 1, characterized in that the Grains in the dielectric ceramic have a homogeneous structure that a uniform composition and a uniform crystal system points. 7. A method for producing a dielectric ceramic, characterized by the following steps:
Providing a barium titanate powder in which the c-axis / a-axis ratio in the perovskite structure is in the range of 1.003 to 1.010 and an amount of OH groups in the crystal lattice is 1% by weight or less , and
Firing the barium titanate powder. 8. A method for producing a dielectric ceramic according to claim 7, there characterized in that in the step of providing a barium titanate Powder a barium titanate powder is provided which is a maximum part size of 0.5 µm or less and an average particle size of 0.1-0.3 µm. 9. A method for producing a dielectric ceramic according to claim 7, there characterized in that in the step of providing a barium tita  nat powder individual particles of the barium titanate powder with a section of low crystallinity and a section of high crystallinity include and the diameter of the portion with the low crystallinity is less than 0.65 times the particle size of the powder. 10. A method for producing a dielectric ceramic according to claim 7, because characterized in that in the firing step a ratio R, which is called (average grain size of dielectric ceramic after firing) / (by average particle size of the intended barium titanate powder) is controlled to fall in the range of 0.90-1.2. 11. A method for producing a dielectric ceramic according to claim 7, there characterized in that the grains that form the dielectric ceramic after firing have a core-shell structure in which the Zu composition and the crystal system of the core and the shell from each other who differentiate. 12. A method for producing a dielectric ceramic according to claim 7, there characterized in that the grains in the dielectric ceramic after the Burning have a homogeneous structure that is uniform together setting and has a uniform crystal system. 13. Laminated ceramic electronic element with a laminate made of a plurality of dielectric ceramic layers is formed, and one Inner conductor that runs along a special transition point between two ne dielectric ceramic layers lying next to one another is formed there characterized in that the dielectric ceramic layers have a dielectri ceramics by firing a barium titanate powder is obtained with a c-axis / a-axis ratio in the perovskite Structure is in the range of 1.003-1.010 and an amount of OH groups in the crystal lattice is 1% by weight or less.   14. Laminated ceramic electronic element according to claim 13, characterized ge indicates that the barium titanate powder has a maximum particle size of 0.5 µm or less and an average particle size of 0.1-0.3 µm owns. 15. Laminated ceramic electronic element according to claim 13, characterized ge indicates that individual particles of the barium titanate powder have an Ab cut with a low crystallinity and a section with a high Include crystallinity and the diameter of the section with the lowest Crystallinity is less than 0.65 times the particle size of the powder. 16. Laminated ceramic electronic element according to claim 13, characterized ge indicates that a ratio R, which is (average grain size of the dielectric ceramic) / (average particle size of barium titanate Powder) is defined, is in the range of 0.90-1.2. 17. Laminated ceramic electronic element according to claim 13, characterized ge indicates that the grains that form the dielectric ceramic have a core Have shell structure in which the composition and the Kri distinguish between the stable system of the core and the shell. 18. Laminated ceramic electronic element according to claim 13, characterized ge indicates that the grains in the dielectric ceramic are homogeneous Have structure that have a uniform composition and a uniform ches crystal system. 19. Laminated ceramic electronic element according to claim 13, characterized ge indicates that the inner conductor contains a base metal.   20. Laminated ceramic electronic element according to claim 19, characterized ge indicates that the inner conductor contains nickel or a nickel alloy. 21. Laminated ceramic electronic element according to claim 13, characterized ge indicates that it also includes a plurality of external electrodes, which are featured in various places on one side surface of the laminate are seen, wherein a plurality of inner conductors is designed so that a End of each inner conductor is exposed to the side surface so that it is electrical can be connected to one of the outer electrodes. 22. A method for producing a laminated ceramic electronic element, characterized by the following steps:
Providing a barium titanate powder in which a c-axis / a-axis ratio in the perovskite structure is in the range of 1.003 to 1.010 and an amount of OH groups in the crystal lattice is 1% by weight or less ;
Producing a laminate in which a plurality of ceramic green foils containing the barium titanate powder and inner electrodes are laminated such that the inner electrodes are along certain transition points of the ceramic green foils; and
Firing the barium titanate powder to thereby provide a dielectric ceramic. 23. Process for producing a laminated ceramic electronic element according to claim 22, characterized in that in the step of Vorse a barium titanate powder is provided, which has a maximum particle size of 0.5 µm or less and one through Average particle size of 0.1-0.3 microns. 24. Process for producing a laminated ceramic electronic element according to claim 22, characterized in that in the step of Vorse a barium titanate powder, individual particles of the barium titanate powder  a section with a low crystallinity and a section with a high crystallinity and the diameter of the section with the low crystallinity is less than 0.65 times the particle size of the powder. 25. Process for producing a laminated ceramic electronic element according to claim 22, characterized in that a Ver ratio R, which as (average grain size of the dielectric ceramic after firing) / (average particle size of the intended bari umtitanate powder) is controlled to be in the range of 0.90-1.2 falls. 26. A method of manufacturing a laminated ceramic electronic element according to claim 22, characterized in that grains which the dielectric Form ceramic, after firing have a core-shell structure, at which is the composition and the crystal system of the nucleus and the Differentiate the shell from each other 27. A method of manufacturing a laminated ceramic electronic element according to claim 22, characterized in that grains in the dielectric Ceramics after firing have a homogeneous structure, which is a uniform composition and a uniform crystal system. 28. A method of manufacturing a laminated ceramic electronic element according to claim 22, characterized in that the inner conductor is a base Metal includes. 29. Process for producing a laminated ceramic electronic element according to claim 22, characterized in that the inner conductor nickel or includes a nickel alloy.   30. A method of manufacturing a laminated ceramic electronic element according to claim 22, characterized in that the step of manufacturing of a laminate to the sub-steps of providing the internal electrodes together with special transition points between two neighboring kera mix green foils such that one end of each inner conductor becomes a side surface surface of the laminate is exposed, and forming a variety of exterior electrodes on the side surface of the laminate such that the bare end of each of the inner conductors electrically connected to the corresponding one of the External electrodes is connected.