JP6020252B2 - Dielectric porcelain composition and electronic component - Google Patents

Description

  The present invention relates to a dielectric ceramic composition and an electronic component including a dielectric layer containing the dielectric ceramic composition.

  In recent years, due to increasing global interest in energy issues, there is a great demand for vehicles such as electric vehicles (EV) and hybrid vehicles (HEV) that emit less carbon dioxide, or power generation devices that use natural energy such as solar cells. It has become to. Since these are used after converting a large voltage, the conversion efficiency of the mounted converter, inverter and power conditioner greatly affects the performance of the apparatus. Therefore, research on power semiconductor elements such as SiC (silicon carbide) and GaN (gallium nitride) is being actively conducted. These power semiconductors have lower on-resistance than conventional Si (silicon) -based semiconductors, so the elements can be made smaller and more efficient, and because they can be used up to 400 ° C, the surrounding cooling devices can also be made smaller. There is a merit.

  For example, a multilayer ceramic capacitor used for removing a surge voltage from a power device based on SiC or GaN or removing noise in an automobile engine room is required to have a wide range of temperature guarantees. ) To 400 ° C., the capacitance change rate is required to be within ± 40%. In addition, since there is a demand for high capacitance, a dielectric ceramic composition having a relatively high relative dielectric constant of 1000 or more is required.

  However, the barium titanate-based material, which is currently the mainstream material for ceramic capacitors, has a Curie point near 130 ° C., and in a high temperature environment of 130 ° C. or higher where a power device based on SiC or GaN can be used, The relative dielectric constant is significantly reduced. In addition, although the relative permittivity of calcium zirconate-based material is stable from room temperature to 400 ° C., since the value of the relative permittivity is small, when trying to create a ceramic capacitor having a desired capacitance, There was a problem that the size would increase.

As a technique for this problem, for example, Patent Document 1 discloses a dielectric ceramic composition having a relative dielectric constant of 500 or more at room temperature and a capacitance change rate ΔC ₃₅₀ / C ₂₅ within ± 15% up to 350 ° C. Things are disclosed. ΔC _x / C ₂₅ represents the rate of change in capacitance at a specified temperature x ° C. with respect to the capacitance at room temperature (25 ° C.), and is obtained by the following formula 1.

A dielectric ceramic composition having a high Curie point is disclosed in Patent Document 1. However, in the dielectric ceramic composition in this document, the relative permittivity is significantly reduced at 350 ° C. or higher, and the absolute value of ΔC ₄₀₀ / C ₂₅ is large. Therefore, it cannot be used as a ceramic capacitor material for SiC or GaN-based power devices.

JP 2011-195359 A

In view of the above situation, the present invention provides a dielectric ceramic composition having a high relative dielectric constant and a small absolute value of ΔC ₄₀₀ / C ₂₅ , and an electronic component using the dielectric ceramic composition. With the goal.

In order to achieve the above object, in the dielectric ceramic composition of the present invention, the general formula a (Bi _0.5 K _0.5 ) TiO ₃ -bBi (M _0.5 Ti _0.5 ) O ₃ -cANbO ₃ Wherein a, b, and c are a + b + c = 1.0, and all of a, b, and c satisfy 0.10 or more, and M is a divalent metal element And at least one element selected from Zn, Mg, Ca, Mn, Fe, Co, Ni, Cu, Sn and Ba, and A is at least one element selected from Li, Na and K, which are alkali metal elements It is an element.

According to the present invention, the relative dielectric constant is 1000 or more and ΔC ₄₀₀ that is optimal for electronic components such as ceramic capacitors used in the vicinity of SiC or GaN-based power devices or in high-temperature environments such as in an automobile engine room. / dielectric ceramic composition C ₂₅ is in the range of ± 40% is obtained.

FIG. 1 is a phase diagram showing composition ranges of Examples and Comparative Examples.

Hereinafter, modes for carrying out the present invention will be described. The dielectric ceramic composition of the present invention contains as a main component a compound represented by the general formula a (Bi _0.5 K _0.5 ) TiO ₃ —bBi (M _0.5 Ti _0.5 ) O ₃ —cANbO _3. A, b and c are a + b + c = 1.0, and all of a, b and c satisfy 0.10 or more, and M is a divalent metal element such as Zn, Mg, Ca, Mn , Fe, Co, Ni, Cu, Sn and Ba, wherein A is at least one element selected from Li, Na and K which are alkali metal elements .

  Furthermore, in the dielectric ceramic composition, it is desirable that 0.30 ≦ a ≦ 0.55, 0.15 ≦ b ≦ 0.40, and 0.30 ≦ c ≦ 0.55.

  In the dielectric ceramic composition, M is more preferably Zn.

  In the dielectric ceramic composition, A is more preferably K.

By setting the composition range, a dielectric ceramic composition having a nanodomain structure, which is an aggregate of ferroelectric domains having a size of several nanometers, can be obtained. In this nanodomain structure, domain walls having a high relative dielectric constant are present in high density and are paraelectric, so that ΔC ₄₀₀ / C ₂₅ is also good. Since this nanodomain structure is an intermediate structure between a relaxor dielectric and a ferroelectric, it can be formed by mixing both. In the present invention, (Bi _0.5 K _0.5 ) TiO ₃ and Bi (M _0.5 Ti _0.5 ) O ₃ form a relaxor dielectric, and ANbO ₃ is a ferroelectric. Where M is at least one element selected from Zn, Mg, Ca, Mn, Fe, Co, Ni, Cu, Sn, and Ba, which are divalent metal elements, and A is an alkali metal element, Li, It is at least one element selected from Na and K.

The general formula _{a (Bi 0.5 K 0.5) TiO} 3 -bBi (M 0.5 Ti 0.5) O 3 is represented by -CANbO ₃ compounds as a main component, wherein a, b and c is, a + b + c = 1.0, and satisfying the relationship that all of a, b and c are 0.10 or more, the relative dielectric constant at room temperature is 1000 or more, and ΔC ₄₀₀ / C ₂₅ is in the range of ± 40%. An inner dielectric ceramic composition can be produced.

Preferably, the ratios a, b, and c of the main components are set to values in a range of 0.30 ≦ a ≦ 0.55, 0.15 ≦ b ≦ 0.40, and 0.30 ≦ c ≦ 0.55. Accordingly, the relative dielectric constant at room temperature can be 1000 or more and ΔC ₄₀₀ / C ₂₅ can be within the range of ± 22%.

More preferably, when M is Zn, a ceramic sintered body having a uniform composition can be obtained. More preferably, when A is K, the relative dielectric constant can be increased and the absolute value of ΔC ₄₀₀ / C ₂₅ can be decreased.

  An example of a method for producing a dielectric ceramic composition according to this embodiment will be described. First, a powder of a compound containing Bi, K, Ti, Zn, Mg, Ca, Mn, Fe, Co, Ni, Cu, Sn, Ba, K, Na, Li, and Nb is mixed with a ball mill so as to have a predetermined composition. Use to wet mix and dry to obtain mixed powder. Examples of the compound powder include oxides, carbonates, nitrates, titanates, sulfides, sulfates, and the like. Next, the obtained mixed powder is calcined at a temperature of 800 ° C. or higher and 1000 ° C. or lower, for example, in the air to obtain a calcined powder.

  Further, the obtained calcined powder is mixed with a binder resin such as polyvinyl butyral and polyvinyl alcohol and an organic solvent at a predetermined ratio to prepare a dielectric paste. This dielectric paste is formed into a sheet shape using a doctor blade or the like. The obtained sheet is cut into a predetermined size, stacked, and hot-pressed to obtain a rectangular parallelepiped sample. The molded product obtained by cutting the rectangular parallelepiped sample is fired, for example, in the atmosphere at a temperature of 900 ° C. or higher and 1100 ° C. or lower to obtain a dielectric ceramic composition.

  In particular, when the dielectric ceramic composition is applied to a multilayer ceramic capacitor, the above-mentioned calcined product is mixed with a binder resin and an organic solvent to prepare a paste as a base of the dielectric layer, and this paste is used as an internal electrode layer. Or by alternately printing and laminating pastes that form the base, or mixing a calcined product with a binder resin to form a ceramic green sheet, and alternately laminating sheets with internal electrodes printed on this sheet And the laminate may be fired. After firing, a multilayer ceramic capacitor is manufactured by connecting terminal electrodes.

  The dielectric ceramic composition according to the present embodiment is mainly used for ceramic capacitors, but can be applied to other electronic components.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, the structure of this invention is not limited to these Examples.

Bi ₂ O ₃ , KHCO ₃ , TiO ₂ , ZnO, Nb ₂ O ₅ powder, the composition of the dielectric ceramic composition after firing was (Bi _0.5 K _0.5 ) TiO ₃ , Bi (Zn _{0 .5} Ti _0.5 ) O ₃ and KNbO ₃ were prepared such that a + b + c = 1.0 when the ratios were a, b, and c. FIG. 1 is a phase diagram showing the composition of this study. The composition of Example 1 to Example 49 is indicated by ○, and the composition of Comparative Example 1 to Comparative Example 15 is indicated by ▲. The prepared powder and YTZ balls were ball mill mixed in an organic solvent, dried, and ground in a mortar to produce a mixed powder.

  Next, this mixed powder was calcined at 800 to 1000 ° C. in the air to obtain a calcined powder.

  A binder resin and an organic solvent were mixed with the calcined powder by a ball mill to obtain a dielectric paste.

  Thereafter, a ceramic green sheet having a thickness of about 10 μm was molded from the dielectric paste by a doctor blade method, laminated to a thickness of about 600 μm, and cut into 12 mm × 12 mm to obtain a laminate.

  Next, the obtained laminate was maintained in the atmosphere at 900 ° C. or higher and 1100 ° C. or lower for 2 hours to obtain a sintered body sample of the dielectric ceramic composition. The obtained dielectric porcelain composition was pulverized with a mortar, and the inductively coupled plasma (ICP) emission spectroscopic analysis method was used to confirm that the prepared composition was the target composition.

  An In-Ga paste was applied as an electrode to both the upper and lower surfaces of the obtained dielectric ceramic composition sintered body sample to obtain an electrical property evaluation sample. The capacitance of this sample was measured using an LCR meter (HEWLETT 4284A) at room temperature, and the relative permittivity when regarded as a parallel plate capacitor was calculated. The measurement frequency was 1 kHz and the voltage was 1V. The voltage is preferably measured at 1 V or higher.

Moreover, the sample for electrical property evaluation was put into a transparent electric furnace (Ishikawa Sangyo) and heated to 500 ° C. at a temperature rising rate of 300 ° C. per hour. At that time, using a digital thermometer (ADVANTEST) and an LCR meter (HEWLETT 4284A), temperature and capacitance were measured every minute. It was regarded as a parallel plate capacitor, and obtained by calculating the relative dielectric constant and ΔC ₄₀₀ / C ₂₅ at each temperature.

Table 1 shows the evaluation results when M in claim 1 is considered as Zn and A as K. In the composition range with a large amount of (Bi _0.5 K _0.5 ) TiO ₃ and Bi (Zn _0.5 Ti _0.5 ) O ₃ , the relative dielectric constant is high, but the absolute value of ΔC ₄₀₀ / C ₂₅ tends to be large. It is in. In the composition range with a large amount of KNbO ₃ , the absolute value of ΔC ₄₀₀ / C ₂₅ is small, but the relative dielectric constant tends to be low.
In the compositions of Comparative Examples 1 to 15 in which any one of a, b, and c is less than 0.10, the specific dielectric constant is 1000 or more and ΔC ₄₀₀ / C ₂₅ is in the range of ± 40%. Absent. In order to set the relative dielectric constant to 1000 or more and ΔC ₄₀₀ / C ₂₅ within the range of ± 40%, all of a, b and c shown in Examples 1 to 33 are within the composition range of 0.10 or more. Must be.

Table 2 shows the evaluation results when M in claim 2 is considered as Zn and A is considered as K. To set the relative dielectric constant to 1000 or more and ΔC ₄₀₀ / C ₂₅ within the range of ± 22%, as shown in Table 2, 0.30 ≦ a ≦ 0.55, 0.15 ≦ b ≦ 0.40 and 0 .30 ≦ c ≦ 0.55 must be within the composition range.

Table 3 shows the evaluation results when the element M of claim 3 is examined. When an X-ray diffraction spectrum of the sintered dielectric ceramic composition sample was measured using an X-ray diffractometer (Panalytic X'pert Pro), when Zn was selected as M (Example 49), (B ₂ O ₃ etc.) was the least. If a different phase exists, the electrical characteristics of the different phase itself have an influence, and in particular, the absolute value of ΔC ₄₀₀ / C ₂₅ increases.

Table 4 shows the evaluation results when the element A of claim 4 was examined. When K having a large atomic number is used as A (Example 49), the relative dielectric constant is high and the absolute value of ΔC ₄₀₀ / C ₂₅ is also small.

Table 5 shows the results of investigation when one or more elements are used as M and Zn, Mg, and Ni are blended simultaneously. _{M x} is element used in Table 5, _{b x} represents the content of _{M x.} That is, b = b ₁ + b ₂ + b ₃ . When Zn is replaced with Mg (Example 49, Example 61 and Example 50), the relative dielectric constant increases due to the compositional non-uniformity in the sample, and the absolute value of ΔC ₄₀₀ / C ₂₅ also increases. In any case, the relative dielectric constant is 1000 or more and the absolute value of ΔC ₄₀₀ / C ₂₅ is within 22%. Even when three types of Zn, Mg, and Ni were blended simultaneously (Example 62, Example 63, and Example 64), the relative dielectric constant was 1000 or more and the absolute value of ΔC ₄₀₀ / C ₂₅ was within 22%. ing.

Table 6 shows the results of investigation when one or more elements are used as A and K, Na, and Li are blended simultaneously. _{A x} is element used in Table 6, _{c x} represents the content of _{A x.} That is, c = c ₁ + c ₂ + c ₃ . When K is replaced by Na (Example 49, Example 65, Example 66, Example 67 and Example 59), it exhibits relaxor behavior at an intermediate value (Example 66), and has a relative dielectric constant. The absolute value of ΔC ₄₀₀ / C ₂₅ increases, but the relative dielectric constant is 1000 or more and the absolute value of ΔC ₄₀₀ / C ₂₅ is within 22%. Even when three types of K, Na, and Li were blended simultaneously (Example 68, Example 69, and Example 70), the relative dielectric constant was 1000 or more and the absolute value of ΔC ₄₀₀ / C ₂₅ was within 22%. ing.

  According to the present invention, a dielectric ceramic composition and an electronic component that are optimal for electronic components such as ceramic capacitors and piezoelectric actuators used in the vicinity of SiC or GaN-based power devices and in high-temperature environments such as in an engine room of an automobile. Is obtained.

Claims (5)

The general formula _{a (Bi 0.5 K 0.5) TiO} 3 -bBi (M 0.5 Ti 0.5) O 3 is represented by -CANbO ₃ compounds as a main component, wherein a, b and c is, a + b + c = 1.0 and all of a, b and c satisfy the relationship of 0.10 or more, and M is a divalent metal element, Zn, Mg, Ca, Mn, Fe, Co, Ni, Cu, Sn A dielectric ceramic composition comprising at least one element selected from Ba and Ba, wherein A is at least one element selected from Li, Na and K, which are alkali metal elements.   The a, b, and c satisfy the relationship of 0.30 ≦ a ≦ 0.55, 0.15 ≦ b ≦ 0.40, and 0.30 ≦ c ≦ 0.55, respectively. The dielectric ceramic composition as described.   3. The dielectric ceramic composition according to claim 1, wherein M is Zn.   The dielectric ceramic composition according to claim 1, wherein A is K.   The electronic component using the said dielectric ceramic composition in any one of Claims 1-4.

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