JP2013028478A - Dielectric ceramic composition and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead-free niobic acid-based dielectric ceramic composition having a small rate of change of relative dielectric constant (for example, ΔC/C=±22% or less) in a wide temperature region (for example -55 to 350°C), various excellent characteristic up to a high temperature region near 350°C, and a high relative dielectric constant, and to provide an electronic component using the dielectric ceramic composition.SOLUTION: A niobic acid compound region and a barium titanate region form respectively a composite structure in a dielectric ceramic composition containing a niobic acid compound represented by general formula (KNa)NbOand barium titanate represented by BaTiO, and further assuming that a solid solution region area of a solid solution represented by [(KNa)Ba](NbTi)Ois A1 and the whole region area is A2, an inequality A1/A2≤0.35 is fulfilled.

Description

  The present invention relates to a dielectric ceramic composition having good characteristics in a high temperature region, and an electronic component using the dielectric ceramic composition.

Conventionally, as electronic parts such as dielectric ceramic compositions and dielectric ceramic capacitors and piezoelectric elements, for example, ceramic compositions containing (Ba, Sr, Ca) (Ti, Zr) O ₃ as main components have been used. (For example, see Patent Documents 1 to 3)
In these compositions, for example, BaTiO ₃ has a Curie point of around 125 ° C., and in a high temperature region of 150 ° C. or higher, it is greatly reduced compared to the relative dielectric constant at room temperature, and in a region of 100 ° C. or higher. Since the relative dielectric constant is remarkably increased as compared to room temperature because it is in the vicinity of the Curie point, the temperature change rate of the relative dielectric constant is very large and cannot be practically used. For this reason, for example, rare earth elements are mixed as subcomponents to control the temperature dependence of the relative permittivity at −55 ° C. to 150 ° C., which is a practical range for ceramic capacitors, and has been widely used in the industrial field.

JP 2007-169090 A JP 2006-342025 A JP, 2005-194138, A For example, a two-component dielectric ceramic component such as PbTiO3-BaZrO3 uses a PbTiO3 Curie point of around 490 ° C to make a dielectric constant up to about 300 ° C. The temperature dependence of the rate can be made relatively small, but Pb must be used for the composition.

  On the other hand, niobic acid-based piezoelectric ceramic compositions that do not contain lead are well known. (For example, refer to Patent Documents 4 to 5), however, none of the documents disclose the temperature dependence of the relative permittivity in a wide temperature range for the dielectric ceramic composition. Further, Patent Document 5 attempts to reduce the temperature dependence of the relative permittivity over a wide temperature range. However, the capacitance change rate (-55 ° C. to 350 ° C.) ΔC / C) exceeds ± 22%, and it cannot be said that satisfactory characteristics are necessarily obtained.

JP 2003-252681 A JP 2009-227482 A JP 2009-249244 A

  For example, in electronic parts for on-vehicle applications, conventionally, for example, EIA standard X8S (capacitance change rate within −22% (−C / C = within ± 22%) at −55 ° C. to 150 ° C.) There is a need for a porcelain capacitor, as electronic components are used closer to the car engine perimeter when more space is required in the car and a more comfortable driving environment is required. There is a demand for a dielectric ceramic capacitor that satisfies ΔC / C = ± 22% even in a temperature region exceeding 150 ° C., which is higher than the maximum temperature guaranteed by the EIA standard.

  Furthermore, the operating temperature range of power devices using SiC or GaN-based semiconductors is beginning to be required up to a high temperature range around 350 ° C., and for use as a smoothing capacitor, for example, a temperature range of −55 to 350 ° C. Also, it is preferable that ΔC / C = ± 22%. However, no description has been made about a dielectric ceramic composition satisfying ΔC / C = ± 22% within a temperature range of −55 to 350 ° C.

In addition, dielectric ceramic capacitors that can satisfy the EIA standard X8S, for example, dielectric ceramic capacitors mainly composed of BaTiO ₃ , SrTiO ₃ , CaTiO _3, etc., are rare earth elements such as Sc, Y, La, Ce. The characteristics are achieved by using rare earth elements such as Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. If the conventional EIA standard X8S characteristics can be achieved without using these rare earth elements, the conventional characteristics can be achieved without using rare elements, depending on market principles such as the recent rise in rare elements. Can be prevented.

Conventionally, there are dielectric ceramic capacitors that satisfy ΔC / C = ± 22% at a high temperature of 150 ° C. or higher by using, for example, PbTiO ₃ as a main component. However, since Pb exists in the composition, For example, PbO, PbO ₂ , Pb ₃ O ₄ or the like must be used, and in the production process, these raw materials may diffuse into the environment. Therefore, solving this requires harmony with the recent environment. It is promising as a technology.

  From the above viewpoint, the present invention has a small relative dielectric constant change rate (for example, ΔC / C = within ± 22%) in a wide temperature range (for example, −55 to 350 ° C.), and is around 350 ° C. An object is to provide a niobic acid-based dielectric ceramic composition that is excellent in various properties up to a high temperature range, has a large relative dielectric constant, and does not contain lead, and an electronic component using the dielectric ceramic composition. To do.

In order to solve the above problems, the present invention provides a dielectric ceramic composition comprising a niobic acid compound represented by the general formula (K _1-x Na _x ) NbO ₃ and barium titanate represented by BaTiO ₃ . Wherein the niobic acid compound region and the barium titanate region form a composite structure, respectively, and the region area of the solid solution in which the (K _1-x Na _x ) NbO ₃ and BaTiO ₃ are solid solution is A1, It is an object of the present invention to provide a dielectric ceramic composition characterized in that A1 / A2 ≦ 0.35 when the total area of the area is A2. Note that the solid solution has the general formula _{[(K 1-x Na x} ) α Ba β] (Nb α Ti β) O 12 represented by like.

  In addition, it is desirable that the niobic acid compound particles constituting the composite structure have a particle size of 100 nm to 1000 nm and the barium titanate particles have a particle size of 50 nm to 1200 nm.

Further, when the area area of the niobic acid compound represented by (K _1-x Na _x ) NbO ₃ forming the composite structure is a and the area area of barium titanate represented by BaTiO ₃ is b, 1 ≦ It is desirable to satisfy the relationship of a / b ≦ 9 and 0 ≦ x ≦ 0.5.

  Moreover, it is desirable to use these dielectric ceramic compositions as electronic parts such as dielectric ceramic capacitors and piezoelectric elements.

  According to the present invention, the change rate of the relative dielectric constant in a wide temperature range (for example, −55 to 350 ° C.) without using a heavy metal element that exerts a load on the environment such as Pb, Bi, or Sb as the main component. Can be flattened within ± 22%, exhibiting good temperature characteristics and a high relative dielectric constant.

  Furthermore, according to the present invention, a dielectric ceramic composition that can exhibit a high relative dielectric constant in a wide temperature range, for example, has a characteristic of a relative dielectric constant of 700 or more at 25 ° C. can be obtained.

  Therefore, as a dielectric ceramic composition according to the present invention, smoothing for a power device using a SiC or GaN-based semiconductor, which is required to be used in a high temperature region, or to a higher temperature region, is required. It is optimal as a capacitor for use.

  Further, the dielectric ceramic composition according to the present invention can satisfy the EIA standard X8S characteristic (ΔC / C at −55 ° C. to 150 ° C. = within ± 22%), and therefore can be used as a capacitor having X8S characteristic.

FIG. It is a figure which shows the change rate of the dielectric constant in -55-350 degreeC in 3, 7, 16, 33, 53, 55. FIG. 2 shows an experiment No. 1 related to the present invention. It is an element mapping image by STEM-EDS of the cross section of 1 dielectric ceramic composition. FIG. 2A shows the distribution state of the Ti element. FIG. 2B shows the distribution state of the K element. FIG. 3 shows an experiment No. 1 relating to a comparative example of the present invention. 5 is an element mapping image by STEM-EDS of a section of dielectric ceramic composition of No. 5. FIG. 3A shows the distribution state of the Ti element. FIG. 3B shows the distribution state of the K element.

  Hereinafter, the present invention will be described based on an embodiment shown in the drawings.

A dielectric ceramic composition according to this embodiment includes a niobic acid compound represented by the general formula (K _1-x Na _x ) NbO ₃ and barium titanate represented by BaTiO ₃ . The niobate compound region and the barium titanate region form a composite structure.

The niobic acid compound particles (K _1-x Na _x ) NbO ₃ constituting one of the composite structures have a Tc (Curie temperature) of about 420 ° C. when x = 0.5, thus improving the relative dielectric constant at high temperatures. can do. On the other hand, the other BaTiO ₃ of the composite structure has a Tc of about 130 ° C. and relatively good room temperature characteristics. Therefore, a part of Ba is replaced with an alkali metal, a part of Ti is replaced with Zr, It is known that a practical composition near room temperature is obtained by addition of a small amount.

Therefore, the (K _1-x Na _x ) NbO ₃ and BaTiO ₃ do not form a solid solution with each other, and a composite structure in which the niobic acid compound region and the barium titanate region are dispersed with each other is formed. it is preferable to take the general formula comprising the solid solution state in each other _{[(K 1-x Na x} ) α Ba β] (Nb α Ti β) the solid solution region represented by _{O 12} is produced relative dielectric constant descend. Therefore, when the area of the solid solution region represented by [(K _1-x Na _x ) _α Ba _β ] (Nb _α Ti _β ) O ₁₂ is A1 and the entire region area is A2, A1 / A2 ≦ It is preferably 0.35.

In addition, when the average particle size of the crystal particles of (K _1-x Na _x ) NbO ₃ is smaller than 100 nm or the average particle size of the crystal particles of BaTiO ₃ is smaller than 50 nm, the formation of the solid solution is likely to proceed. Thus, the dielectric constant of the obtained dielectric ceramic composition is lowered. Further, when the average particle diameter of the crystal grains of BaTiO ₃ is smaller than 50nm, because the dielectric constant of the crystal grains themselves BaTiO ₃ is lowered, form a composite structure _{(K 1-x Na x)} NbO 3 and BaTiO ₃ Since the relative dielectric constant balance is lost, the capacitance change rate within ΔC / C = ± 22% is not satisfied within the temperature range of −55 to 350 ° C.

When the average particle diameter of the crystal particles of (K _1-x Na _x ) NbO ₃ is 1000 nm or the average particle diameter of the crystal particles of BaTiO ₃ is larger than 1200 nm, the effect of flattening the temperature characteristics decreases, − In the temperature range of 55 to 350 ° C., the capacitance change rate is not satisfied within ΔC / C = ± 22%.

  For this reason, it is preferable that the niobic acid compound particles constituting the composite structure have an average particle size of 100 nm to 1000 nm and the barium titanate particles have an average particle size of 50 nm to 1200 nm.

Furthermore, as a method for producing a dielectric ceramic composition, in the case of constituting a composite structure, a condition that the particle diameter of the raw material powder is easily maintained is preferable. The particle diameter of the raw material is 100 nm ≦ (K _1−x Na _x ). It is preferable to use a raw material having an average particle diameter of NbO ₃ ≦ 1000 nm and an average particle diameter of 50 nm ≦ BaTiO ₃ ≦ 1300 nm. These raw materials are used in a predetermined amount. (K _1-x Na _x ) NbO ₃ can be made using various raw materials such as carbonates, nitrates, hydroxides, organometallic compounds such as oxides and composite oxides of K, Na, and Nb. Is a raw material such as an unreacted oxide or compound before becoming (K _1-x Na _x ) NbO ₃ , the niobic acid compound and barium titanate in the baking process after mixing with BaTiO ₃ A large amount of solid solution is generated, leading to a decrease in dielectric constant and various characteristics. Therefore, as the raw material to be used for mixing with barium titanate K, Na, it is preferable to use a raw material left unreacted was no _{(K 1-x Na x)} NbO 3 of Nb. In general, firing is preferably performed while maintaining the particle size of the raw material, but firing may be performed under conditions that allow the grains to grow as long as the solid solution is not generated.

When the area area of (K _1-x Na _x ) NbO ₃ constituting the composite structure is a and the area area of BaTiO ₃ is b, the composite area ratio a / b is in the range of 1 ≦ a / b ≦ 9. Is preferred. When the composite area ratio (a / b) falls outside the range of 1 ≦ a / b ≦ 9, the change in capacitance in the temperature range of −55 to 350 ° C. increases, and the change rate of capacitance within 22% Cannot be achieved.

The _{x of} (K _1-x Na _x ) NbO ₃ constituting one of the composite structures is preferably in the range of 0 ≦ x ≦ 0.5. If x is in a range of 0 ≦ x ≦ 0.5, a capacitance change rate within 22% can be achieved while maintaining a high capacitance in a temperature range of −55 to 350 ° C. When x exceeds 0.5, the solid solution region increases, the capacitance decreases, and a capacitance change rate within 22% cannot be achieved. For this reason, in order to increase the relative dielectric constant, solid solution regions are unlikely to occur, and x = 0 is preferable. However, if x is in the range of 0.5 or less, the capacitance change rate is adjusted by changing x. It is possible to further improve the temperature characteristics at high temperatures.

  In addition, the dielectric ceramic composition according to the present embodiment can contain a subcomponent to reduce the firing temperature and improve the life. Such subcomponents are not particularly limited, and examples thereof include silicon dioxide and aluminum oxide as a compound having an effect of firing temperature. Further, examples of the compound having an effect of improving the life include alkali metal compounds such as magnesium oxide, manganese oxide, rare earth element oxide, vanadium oxide, and the like, but are not limited thereto. The content may be appropriately determined according to the composition and the like.

  Next, a dielectric ceramic composition of the present embodiment and a method for manufacturing a capacitor using the same will be described.

First, crystal particle powder of each component constituting the dielectric ceramic composition is prepared. In the present embodiment, a powder of (K _1-x Na _x ) NbO _{3 and} a powder of BaTiO ₃ are prepared. As for the preparation of these crystal particle powders, for example, a BaTiO3 powder produced using a commercially available hydrothermal synthesis method, oxalate method, sol-gel method, or the like may be used. Further, the powder of (K _1-x Na _x ) NbO ₃ uses a solid phase synthesis method in which mixing, calcining, and pulverization are performed using K ₂ CO ₃ , Na ₂ CO ₃ , and Nb ₂ O ₅ as raw materials. A powder prepared in this manner may be used.

The dielectric ceramic composition of the present invention is obtained by preparing the powder of (K _1-x Na _x ) NbO _{3 and} the powder of BaTiO ₃ in advance by the above-mentioned method and adjusting the firing conditions. _{(K 1-x Na x)} α Ba β] (Nb α Ti β) O 12 it is possible to minimize the generation of a solid solution as represented since.

  Moreover, when the dielectric ceramic composition according to the present embodiment contains the above-described subcomponent, a raw material for the subcomponent is also prepared. The raw material of the subcomponent is not particularly limited, and the above-described oxides and composite oxides of the respective components, or various compounds that become these oxides and composite oxides by firing, such as carbonates, nitrates, hydroxides, organics It can be appropriately selected from metal compounds and the like.

  The prepared raw materials are weighed and mixed so as to have a predetermined composition ratio to obtain a raw material mixture. Examples of the mixing method include wet mixing using a ball mill and dry mixing using a dry mixer.

  The obtained raw material mixture may be granulated by adding a binder resin, or may be granulated, or may be pasted together with a binder resin or a solvent to form a slurry. In addition, the raw material mixture may be preliminarily calcined before making the granulated product or slurry.

  The method for molding the granulated product or slurry is not particularly limited, and examples thereof include a sheet method, a printing method, dry molding, wet molding, and extrusion molding. In the present embodiment, dry molding is adopted, and the granulated product is filled in a mold and molded by compression and pressing (pressing). The shape of the molded body is not particularly limited, and may be appropriately determined according to the application. In the present embodiment, a disk-shaped molded body is used.

  The obtained molded body is baked after removing the binder as necessary.

  The firing conditions may be appropriately determined according to the composition and the like, but the firing temperature is preferably 1000 to 1200 ° C., and the holding time is preferably 1 to 24 hours.

After firing, annealing is performed as necessary to obtain a dielectric ceramic composition as a sintered body. In the present invention, it is not always necessary to perform the annealing treatment, but by adjusting the annealing treatment conditions, the solid solution of (K _1-x Na _x ) NbO ₃ and BaTiO ₃ does not change without changing the grain size after firing. The amount generated can be varied. Next, the obtained dielectric ceramic composition is subjected to end face polishing to form an electrode.

  The dielectric ceramic composition of the present embodiment produced as described above is suitably used for electronic parts such as ceramic capacitors. In the above description, the disk-shaped ceramic capacitor has been exemplified as the dielectric ceramic composition according to the present embodiment. However, the stack is formed by alternately laminating sheets using the dielectric ceramic composition and electrode materials. It may be a dielectric ceramic composition constituting a dielectric layer of an electronic component such as a type dielectric material ceramic capacitor.

  Further, the dielectric ceramic composition of the present embodiment also has good piezoelectric characteristics (for example, piezoelectric constant: d33 = 40 pC / N), and therefore is suitably used for piezoelectric elements.

  Furthermore, the dielectric ceramic composition according to the present invention may be used for an electronic component such as a single-plate capacitor or an electronic component such as a multilayer capacitor. Alternatively, it may be used for a piezoelectric element.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to the embodiment mentioned above at all, and can be variously modified within the range which does not deviate from the summary of this invention.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
First, KNbO ₃ having an average particle diameter of 500 nm and BaTiO ₃ having an average particle diameter of 300 nm are prepared as starting powders, and weighed so as to be 70 mol% KNbO ₃ and 30 mol% BaTiO ₃ , respectively. Wet mixing was performed for 17 hours by a ball mill using water as a dispersion medium. Thereafter, the obtained mixture was dried to obtain a raw material powder.

  A disc-shaped green molded body having a diameter of 10 mm and a thickness of about 1 mm was obtained by adding 2% by weight of PVB as a binder resin to the obtained raw material powder and molding it at a pressure of 250 MPa. This was heated in the air at 700 ° C. for 10 hours for binder removal treatment.

Next, the obtained molded body after the binder removal was fired in air at 1100 to 1200 ° C. for 10 hours to obtain a disk-shaped sintered body. The obtained disc-shaped sintered body was further subjected to annealing treatment in order to adjust the amount of solid solution phase formed of (K _1-x Na _x ) NbO ₃ and BaTiO ₃ . The annealing conditions are as shown in Experiment No. 1 in Table 1. As shown in 1 to 6, heat treatment was performed in air at 825 ° C., 850 ° C., and 900 ° C. for 30 to 600 minutes. Further, the obtained sintered body was polished, an Ag electrode was applied to the main surface thereof, and a baking process was performed in air at 650 ° C. for 20 minutes to obtain a disk-shaped ceramic capacitor sample.

  The obtained material is the experiment No. 1 in Table 1. As shown in 1 to 6, the amount of the solid solution phase generated is longer as the annealing time is longer and the temperature is higher, the relative dielectric constant decreases as the solid solution phase is generated, and the capacitance temperature characteristic is poor in flatness. There is a tendency to become. However, if the area ratio (A1 / A2) of the solid solution produced after firing the material is 0.35 or less, ΔC / C can be within 22% in the temperature range of −55 to 350 ° C.

Moreover, the average particle diameters of (K _1-x Na _x ) NbO ₃ and BaTiO ₃ shown in the table are those obtained by polishing the cross section of the material body after firing and obtaining SEM photographs by image processing. In this firing, although (G _1-x Na _x ) NbO ₃ used as a raw material shows a slight grain growth, conditions were selected so that the grain size before firing can be maintained together with BaTiO ₃ .

Experiment No. No. 7 prepared as starting powders K ₂ CO ₃ and Nb ₂ O _{5 having} an average particle size of 500 nm or less, and BaTiO ₃ having an average particle size of 300 nm, each of 35 mol% K ₂ CO ₃ and Nb ₂ O _5. And weighed so as to be 30 mol% of BaTiO 3, and materials were prepared in the same manner. In this material, since the solid solution of niobic acid compound and barium titanate was produced in large quantities after firing, the aryl treatment was omitted.

Example 2
KNbO _{3 having} an average particle diameter of 50 to 1300 nm and BaTiO ₃ (hereinafter also referred to as BT) having an average particle diameter of 20 to 1500 nm were prepared as starting powders, and 70 mol% of KNbO ₃ and 30 mol% of BaTiO ₃ were prepared. Then, each was weighed and wet mixed by a ball mill for 17 hours using water as a dispersion medium. Thereafter, the obtained mixture was dried to obtain a raw material powder.

  In addition, the materials shown in Table 2 were obtained in the same manner as in Example 1.

The average particle size of KNbO ₃ and BaTiO ₃ constituting the composite structure of the obtained sintered material is almost the same as the particle size of KNbO ₃ and BaTiO ₃ before firing prepared as a starting powder under the current firing conditions. The values shown in Table 2 were obtained.

As shown in Table 2, when the average particle size of KNbO ₃ after firing becomes smaller than 100 nm, the flatness of the capacitance temperature characteristic becomes poor, and when the average particle size exceeds 1000 nm, the relative dielectric constant becomes small. Become. Therefore, the average particle size range of KNbO ₃ is preferably 100 nm or more and 1000 nm or less. In addition, when the average particle size of BaTiO ₃ after firing becomes smaller than 50 nm, the relative dielectric constant of BaTiO ₃ itself decreases, and the amount of solid solution increases, so the relative dielectric constant of the material decreases, and the average particle size When the thickness exceeds 1200 nm, the flatness of the capacitance temperature characteristic becomes poor. Therefore, the average particle diameter range of BaTiO ₃ is preferably 50 nm or more and 1200 nm or less.

Example 3
As a starting material powder, KNbO ₃ having an average particle size of about 500 nm and BaTiO ₃ having an average particle size of about 300 nm in molar ratios of 4: 6, 5: 5, 6: 4, 7: 3, 8: 2, 9: Each was weighed to a ratio of 1, 19: 1 and wet-mixed with a water as a dispersion medium by a ball mill for 17 hours. And the mixture was dried and the raw material powder of the dielectric ceramic composition was obtained.

  Thereafter, materials shown in Table 3 were obtained in the same manner as in Examples 1 and 2.

The composite area ratio (a / b) is in the range of 1 ≦ a / b ≦ 9, where a is the area area of KNbO ₃ and b is the area area of BaTiO _{3 in} the obtained sintered material. Within −55 to 350 ° C., ΔC / C = within 22% can be satisfied, but if this range is exceeded, the composite effect of KNbO ₃ and BaTiO ₃ becomes weak, and the rate of change in capacitance becomes worse.

Example 4
As the starting powder, the average particle diameter is about 500 nm, and x takes values of 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6, respectively (K _1-x Na _x ) NbO ₃ and BaTiO ₃ (hereinafter also referred to as BT) having an average particle size of about 300 nm were prepared. 70 mol% of (K _1-x Na _x ) NbO ₃ having different values of x is prepared, each is weighed so that BaTiO ₃ is 30 mol%, and wetted by a ball mill with water as a dispersion medium for 17 hours. Mixed. And the mixture was dried and the raw material powder of the dielectric ceramic composition was obtained.

  Thereafter, the materials shown in Table 4 were obtained in the same manner as in Examples 1, 2, and 3.

As shown in Table 4, the temperature characteristics can be controlled by increasing x of the niobic acid compound represented by (K _1-x Na _x ) NbO ₃ and increasing Na. Can be flat. However, when x is increased, (K _1-x Na _x ) NbO ₃ reacts with BaTiO ₃ to easily form a solid solution, and the relative permittivity tends to decrease. Therefore, the range of x is preferably 0 or more and 5 or less. Furthermore, if x is 2 or less, a relative dielectric constant of 1000 or more can be secured.

In Table 4, Experiment No. No. 55, a BaTiO ₃ main component and Mg, Ca, Mn, V, Y, Yb, Si, Zr, etc. added as a minor component, which is superior in temperature characteristics to X8S characteristics and satisfies X8R characteristics It is the capacitance change rate for a ceramic capacitor. As shown in FIG. 1, when the use temperature exceeds 150 ° C., the capacitance rapidly decreases and the temperature characteristics deteriorate, so that it is not suitable for use at a high temperature exceeding 150 ° C.

Evaluation of the area by image analysis The niobic acid compound, the barium titanate, and the dielectric ceramic composition obtained by firing in the above-described examples are subjected to micro-sampling using FIB (focused ion beam), A TEM sample was prepared. This sample was subjected to STEM image observation using JEM2200FS and STEM-EDS mapping. The observation visual field was set to 3.0 μm × 3.0 μm, and five or more visual fields were observed for each sample. Using the composition maps obtained by these methods, a region where elements of K, Na, Nb, Ba, and Ti were simultaneously observed was regarded as a solid solution region, and an average area of the results of five or more fields of view was used.

The area ratio (A1 / A2) of the solid solution is such that the area of the solid solution formed by solid solution of (K _1-x Na _x ) NbO ₃ and BaTiO ₃ is A1, the entire area is A2, and the TEM -It calculated | required using the image by EDS mapping. FIG. 2 shows the case where (K _1-x Na _x ) NbO ₃ and BaTiO ₃ are not dissolved (A1 / A2 = 0), and FIG. 3 shows that (K _1-x Na _x ) NbO ₃ and BaTiO ₃ are It is an image by TEM-EDS mapping when it is not solid solution (A1 / A2 = 0.41). The bright portions in FIGS. 2A and 3A indicate regions with a large Ti element, and dark portions indicate regions with a small amount. Moreover, the bright part of FIG.2 (b) and FIG.3 (b) shows an area | region with many K elements, and a dark part shows an area | region with few.

Incidentally, FIG. 2 (a), the show bright areas BaTiO ₃ regions of FIG. 3 (a), a dark portion shows a _{(K 1-x Na x)} NbO 3 region. The region of light and dark colors that is not seen in FIG. 2 but is only seen in FIG. 3 is the area (A1) of the solid solution in which (K _1-x Na _x ) NbO ₃ and BaTiO ₃ are dissolved. .

The area area a of (K _1-x Na _x ) NbO _{3 and} the area area b of BaTiO ₃ were determined in the same manner.

Evaluation of particle diameter by image analysis The average particle diameter of crystals in the composite structure is determined by discriminating niobic acid compound particles and BaTiO ₃ particles using the TEM image and STEM composition image obtained by the above method. Diameter and number were evaluated. The code method was used to measure the particle size.

The capacitance (C) was measured for a dielectric constant capacitor sample at a reference temperature of 25 ° C. using a 4294A manufactured by Agilent Technologies, with a frequency of 1 kHz and a measurement voltage of 1 V. The relative dielectric constant εs (no unit) was calculated based on the thickness of the dielectric ceramic composition, the effective electrode area, and the capacitance obtained as a result of the measurement.

Capacitance temperature characteristic Capacitor sample was placed in a Despatch thermostat, the capacitance at a voltage of 1V was measured in the temperature range of -55 to 350 ° C, and the capacitance at + 25 ° C (C25) The rate of change in capacitance (ΔC / C (%)) with respect to was calculated from the equation: ΔC / C = {(C−C25) / C25} × 100.

  Because the rate of change of relative permittivity is small in a wide temperature range, it is suitable for use as a smoothing capacitor for power devices using SiC or GaN-based semiconductors in an environment close to the engine room for automotive use. Is also applicable.

1 BaTiO ₃
2 (K _1-x Na _x ) NbO ₃
3 (K _1-x Na _x ) NbO ₃ and BaTiO ₃ solid solution

Claims (4)

A dielectric ceramic composition comprising a niobic acid compound represented by the general formula (K _1-x Na _x ) NbO ₃ and barium titanate represented by BaTiO ₃ , wherein the niobic acid compound region and titanic acid When the barium region forms a composite structure, the area of the solid solution formed by dissolving (K _1-x Na _x ) NbO ₃ and BaTiO ₃ is A1, and the total area is A2, /A2≦0.35, wherein the dielectric ceramic composition is characterized.   The average particle size of the niobic acid compound constituting the composite structure is 100 nm or more and 1000 nm or less, and the average particle size of the barium titanate is 50 nm or more and 1200 nm or less. Dielectric porcelain composition. When the area area of the niobic acid compound represented by (K _1-x Na _x ) NbO ₃ forming the composite structure is a and the area area of barium titanate represented by BaTiO ₃ is b, 1 ≦ a / 3. The dielectric ceramic composition according to claim 1, wherein the relation of b ≦ 9 and 0 ≦ x ≦ 0.5 is satisfied.   An electronic component comprising the dielectric ceramic composition according to any one of claims 1 to 3.