JP2008109019A - Multilayer ceramic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer ceramic capacitor employing a dielectric porcelain composed of BT crystal grains and BCT crystal grains as a dielectric layer in which deterioration incident to time variation in high temperature load test can be suppressed, and a high insulation multilayer ceramic capacitor can be obtained without providing a step for reoxidation processing in the fabrication process. <P>SOLUTION: In a multilayer ceramic capacitor where a dielectric layer 5 composed of titanic acid barium crystal grains (BT crystal grains 9b) having Ca concentration of 0.2 atm.% or less and titanic acid barium calcium crystal grains (BCT crystal grains 9a) having Ca concentration of 0.4 atm.% or above, and an inner electrode layer 7 are laminated alternately, the BT crystal grains 9b and the BCT crystal grains 9a contain Mg, and rare earth element and vanadium and the content of Mg and rare earth element contained in the center of the BT crystal grains 9b is higher than the content of Mg and rare earth element contained in the center of the BCT crystal grains 9a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a multilayer ceramic capacitor, and more particularly, to a small and high capacity multilayer ceramic capacitor in which a dielectric layer is composed of barium titanate crystal particles having different Ca concentrations.

  In recent years, with the spread of mobile devices such as mobile phones and the high speed and high frequency of semiconductor elements, which are the main components of personal computers, multilayer ceramic capacitors mounted on such electronic devices are required to be smaller and have higher capacities. Increasingly. For this reason, the dielectric layers constituting the multilayer ceramic capacitor are made thin and highly laminated.

For example, in Patent Document 1, with respect to the dielectric powder constituting the dielectric ceramic, barium titanate powder (BCT powder) in which a part of the A site is replaced with Ca, and barium titanate powder not containing Ca (BCT powder) BT powder) is used as a mixture, and the fired dielectric layer is made into composite particles of barium titanate crystal particles (BT crystal particles) and barium calcium titanate crystal particles (BCT crystal particles). Describes a multilayer ceramic capacitor that can be made as thin as 2 μm.
JP 2006-156450 A

  However, the multilayer ceramic capacitor using the dielectric layer composed of the composite particles disclosed in Patent Document 1 has a problem that the insulation resistance gradually decreases with the high temperature standing time in the evaluation of the high temperature load life. It was.

  Furthermore, when manufacturing the above multilayer ceramic capacitor, the capacitor body before forming the external electrode immediately after the main firing in a strong reducing atmosphere at a temperature of about 1200 ° C. has a reduced dielectric layer and is practical. It did not have insulation resistance.

  Therefore, the capacitor body after the main firing usually needs to be reoxidized in an atmosphere at a lower temperature and higher oxygen concentration than the conditions for the main firing.

  This re-oxidation treatment requires the same amount of labor, time, and expense as the firing step, which has caused high manufacturing costs.

  Accordingly, the present invention relates to a multilayer ceramic capacitor having a dielectric ceramic layer composed of BT crystal particles and BCT crystal particles as a dielectric layer, a multilayer ceramic capacitor capable of suppressing a decrease in insulation resistance with time change in a high temperature load test, Another object of the present invention is to provide a highly insulating multilayer ceramic capacitor without providing a reoxidation process in the manufacturing process.

  The multilayer ceramic capacitor of the present invention includes a barium titanate crystal particle (BT crystal particle) having a Ca concentration of 0.2 atomic% or less and a barium calcium titanate crystal particle (BCT crystal particle) having a Ca concentration of 0.4 atomic% or more. In the multilayer ceramic capacitor in which the dielectric layers constituted by and the internal electrode layers are alternately laminated, the BT crystal particles and the BCT crystal particles contain Mg, a rare earth element, and vanadium, and the BT crystal particles The content of Mg and rare earth elements contained in the central part of the BCT is larger than the contents of Mg and rare earth elements contained in the central part of the BCT crystal particles.

  In the multilayer ceramic capacitor, vanadium is an oxide when the average particle size of the BT crystal particles is larger than the average particle size of the BCT crystal particles, and the barium titanate in the dielectric layer is 100 mol parts. It is desirable to contain 0.1-0.4 mol part in conversion.

  According to the present invention, the dielectric layer constituting the multilayer ceramic capacitor is composed of BCT crystal particles and BT crystal particles, vanadium is contained in these crystal particles, and Mg and rare earth elements contained in the BT crystal particles By making the content of Mg higher than the contents of Mg and rare earth elements contained in the BCT crystal particles, the BT crystal particles become highly cubic with a collapsed core-shell structure. By coexisting the crystal grains between the BCT crystal grains, the insulation resistance of the dielectric ceramic composed of the BT crystal grains and the BCT crystal grains has high insulating properties even after the main firing, and in the high temperature load test. A monolithic ceramic capacitor can be obtained in which the insulation resistance is less lowered with time.

  The multilayer ceramic capacitor of the present invention will be described in detail based on the schematic sectional view of FIG. FIG. 1 is a schematic cross-sectional view showing a multilayer ceramic capacitor of the present invention. The enlarged drawing of the drawer is a schematic diagram showing the main crystal grains and the grain boundary layer constituting the dielectric layer. In the multilayer ceramic capacitor of the present invention, external electrodes 3 are formed at both ends of the capacitor body 1. The external electrode 3 is formed, for example, by baking Cu or an alloy paste of Cu and Ni.

  The capacitor body 1 is configured by alternately laminating dielectric layers 5 and internal electrode layers 7. The dielectric layer 5 includes crystal grains 9 and a grain boundary layer 11. The thickness is preferably 3 μm or less, and particularly preferably 2.5 μm or less in order to reduce the size and capacity of the multilayer ceramic capacitor. Further, in the present invention, in order to stabilize the capacitance variation and the capacitance-temperature characteristics, The thickness of the dielectric layer 5 is more preferably 1 μm or more.

  The internal electrode layer 7 is preferably a base metal such as nickel (Ni) or copper (Cu) in that the manufacturing cost can be suppressed even if the internal electrode layer 7 is highly laminated. In particular, simultaneous firing with the dielectric layer 5 according to the present invention is possible. Nickel (Ni) is more preferable in that it can be achieved.

  The crystal particles 9 constituting the dielectric layer 5 in the multilayer ceramic capacitor of the present invention are perovskite barium titanate crystal particles having different Ca concentrations. That is, it is composed of perovskite-type barium titanate crystal particles (BCT crystal particles) 9a in which a part of the A site is substituted with Ca and perovskite-type barium titanate crystal particles (BT crystal particles) 9b not containing Ca.

  That is, the crystal particle 9 according to the present invention contains the BCT crystal particle 9a and the BT crystal particle 9b, and as described above, excellent dielectric properties can be obtained by the coexistence of these two kinds of crystal particles. Show.

  In the present invention, the BT crystal particles 9b are barium titanate crystal particles having a Ca concentration of 0.2 atomic% or less, while the BCT crystal particles 9a have a Ca concentration of 0.4 atomic% or more, in particular, the BCT crystal particles 9a. In view of maintaining the function as a ferroelectric having a high relative dielectric constant, it is desirable that the Ca concentration be 0.5 to 2.5 atomic% of barium titanate crystal particles.

  In addition, the average particle diameter of the crystal particles 9 (BCT crystal particles 9a and BT crystal particles 9b) in the present invention is 0.45 μm in that high capacity and high insulation are achieved by thinning the dielectric layer 5. The following is preferred. On the other hand, the lower limit of the particle diameters of the BCT crystal particles 9a and the BT crystal particles 9b is 0.15 μm or more because the dielectric constant of the dielectric layer 5 is increased and the temperature dependence of the dielectric constant is suppressed. preferable.

Here, the BCT crystal particle 9a which is one crystal particle constituting the crystal particle 9 is a perovskite-type barium titanate in which a part of the A site is substituted with Ca as described above, and ideally (Ba _1-x Ca _x ) TiO ₃ In the present invention, the amount of Ca substitution in the A site in the BCT crystal particles 9a is preferably X = 0.01 to 0.2, particularly preferably X = 0.02 to 0.07. If the amount of Ca substitution is within this range, the phase transition point near room temperature is shifted to a sufficiently low temperature side, and due to the coexistence structure with the BT crystal particles 9b, excellent temperature characteristics and DC bias characteristics in the temperature range used as a capacitor. This is because it can be secured.

On the other hand, the BT crystal particles 9b are barium titanate having a perovskite structure that does not contain Ca, and are ideally represented by BaTiO ₃ . In the present invention, the BT crystal particles 9b have a Ca concentration of 0.2 atomic% or less as an analytical value.

The BCT crystal particles 9a and the BT crystal particles 9b both contain Mg, rare earth elements and Mn, and the contents of Mg, rare earth elements and Mn contained in the crystal particles 9 are as follows: per 100 parts by mol main crystal grains (BCT crystal grain 9a and the BT crystal grain 9b), 0.5 to 1 parts by mole Mg is as MgO, 0.5 to 1 mol part rare earth element as _RE 2 _{O 3,} Mn If MnO is 0.1 to 0.3 mol part, there is an advantage that the temperature characteristics of the capacitance can be further stabilized, the insulation resistance can be increased, and further, the decrease of the insulation resistance in the high temperature load test can be suppressed. is there.

  In particular, in the present invention, vanadium is contained in the crystal particle 9 for the reason that the BT crystal particle has high cubicity with a collapsed core-shell structure, and Mg and rare earth contained in the central portion of the BT crystal particle 9b. It is important that the concentration of any of the elements is higher than the concentration of any of Mg and rare earth elements contained in the central portion of the BCT crystal particle 9a.

  On the other hand, the dielectric layer does not contain vanadium, and the content of Mg and rare earth elements contained in the central portion of the BT crystal particles is the content of Mg and rare earth elements contained in the central portion of the BCT crystal particles. When the content is the same or low, the BT crystal particles maintain the core-shell structure and thus have a high tetragonal property, and both the BT crystal particles and the BCT crystal particles maintain the core-shell structure. The ceramic capacitor has a low insulation resistance after the main firing. The central part of the BT crystal particle 9b and the BCT crystal particle 9a is a region deeper than 60 nm from the surface of these crystal particles according to the embodiment.

  FIG. 2A is a graph showing the concentration distribution of Mg and Y with respect to BT crystal particles in the dielectric layer constituting the multilayer ceramic capacitor of the present invention, and FIG. 2B is the dielectric constituting the multilayer ceramic capacitor of the present invention. It is a graph which shows density | concentration distribution of Mg and Y about the BCT crystal grain in a layer. This example is a sample No. in Examples described later. 5 was evaluated. The concentrations of Mg and rare earth elements in the crystal particles 9 can be analyzed by a transmission electron microscope and an analyzer (EPMA) attached thereto. In this case, the concentration of Mg and rare earth elements in each crystal particle can be determined by performing elemental analysis by EDX at intervals of 5 nm from the surface to the inside of the selected crystal particle to determine the concentration distribution. In the graph of FIG. 2, 0 nm as the distance from the grain boundary is the surface of the crystal grain, and the plot point at one end of the graph is the center of the crystal grain.

  As is clear from FIG. 2, the BT crystal particles 9b constituting the dielectric layer 5 in the multilayer ceramic capacitor of the present invention have Mg and Y concentration changes from the surface to the center of the crystal particles as compared with the BCT crystal particles 9a. Is moderate. On the other hand, the BCT crystal particle 9a has a large change in the concentration of Mg and Y from the surface to the center of the crystal particle. From this, in the BT crystal particle 9b, compared with the BCT crystal particle 9b, Mg and Y are dissolved in the BT crystal particle 9b, so that the core-shell structure in the BT crystal particle is broken. On the other hand, the BCT crystal particle 9a has a large change in the concentration of Mg and Y from the surface of the crystal particle to the center as described above, and the state of the core-shell structure is maintained because the concentration of Mg and Y in the crystal particle is low. .

  Here, the rare earth element in the present invention is preferably at least one of La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Y, Er, Tm, Yb, Lu, and Sc.

  On the other hand, when the concentration of either Mg or rare earth element contained in the BT crystal particle 9b is lower than the concentration of either Mg or rare earth element contained in the BCT crystal particle 9a, the BT crystal particle has a core-shell structure. Therefore, it is difficult to achieve a high cubic crystallinity, and high insulation cannot be achieved.

  In addition, in the present invention, it is desirable that the average particle size of the BT crystal particles 9b is larger than the average particle size of the BCT crystal particles 9a. As a result, the insulating properties of the dielectric layer 5 can be increased due to the large size of the highly insulating BT crystal particles 9b.

  In the present invention, when the content of barium titanate contained in the composite particles 9a and 9b constituting the dielectric layer 5 is 100 mol parts, vanadium is converted to 0.1 to 0.4 mol parts in terms of oxide. It is desirable to contain. By containing vanadium as an oxide, there is an advantage that the insulation of the capacitor body after reduction firing is further enhanced.

  Next, the manufacturing method of the multilayer ceramic capacitor according to the present invention will be described in detail. FIG. 4 is a process diagram showing a method for producing the multilayer ceramic capacitor of the present invention.

  FIG. 3 is a process diagram showing a method for producing the multilayer ceramic capacitor of the present invention.

  Step (a): In the production method of the present invention, first, a ceramic slurry is prepared by mixing the following raw material powder with an organic resin such as polyvinyl butyral resin and a solvent such as toluene and alcohol using a ball mill or the like, The ceramic green sheet 21 is formed from the ceramic slurry using a sheet forming method such as a doctor blade method or a die coater method. The thickness of the ceramic green sheet 21 is preferably 1 to 4 μm from the viewpoint of reducing the thickness of the dielectric layer for increasing the capacity and maintaining high insulation.

In the production method of the present invention, a perovskite-type barium titanate powder (BCT powder) in which a part of the A site is substituted with Ca and a perovskite-type barium titanate powder (BT powder) not containing Ca are used. The dielectric powder is a raw material powder represented by (Ba _1-x Ca _x ) TiO ₃ and BaTiO ₃ . Here, the Ca substitution amount in the A site in the BCT powder is preferably X = 0.01 to 0.2, particularly preferably X = 0.03 to 0.1. The BCT powder preferably has an atomic ratio A / B of A site (barium) and B site (titanium), which are constituent components, of 1.003 or more, and the BT powder has an A / B of 1.002. The following is desirable. When A / B is 1.002 or less, the BT powder has an advantage that the solid solution of additives such as Mg and rare earth elements can be enhanced.

  These BT powder and BCT powder are synthesized by mixing a compound containing a Ba component, a Ca component and a Ti component so as to have a predetermined composition. These dielectric powders are obtained by a synthesis method selected from a solid phase method, a liquid phase method (including a method of generating via oxalate), a hydrothermal synthesis method, and the like. Among these, the dielectric powder obtained by the hydrothermal synthesis method is desirable because the particle size distribution of the obtained dielectric powder is narrow and the crystallinity is high.

  The particle size distribution of barium titanate powder (BT powder) and barium calcium titanate powder (BCT powder), which are dielectric powders used in the present invention, facilitates thinning of the dielectric layer 5 and It is desirable to be 0.15 to 0.4 μm from the viewpoint of increasing the relative dielectric constant.

  Mg to be added to the dielectric powder is 0.4 to 1 mole part in terms of oxide with respect to 100 mole part of dielectric powder which is a mixture of BCT powder and BT powder, and the rare earth element is BCT powder and BT powder. 0.5 to 1 mol part in terms of oxide with respect to 100 mol part of dielectric powder as a mixture, and Mn is 0 in terms of oxide with respect to 100 mol part of dielectric powder that is a mixture of BCT powder and BT powder. It is preferable that it is 0.1-0.3 mol part.

The sintering aid added to the dielectric powder is composed of Li ₂ O, SiO ₂ , BaO, and CaO as constituent components. The addition amount of the sintering aid is preferably 0.5 to 2 parts by mass with respect to 100 parts by mass of the dielectric powder, which is a mixture of BCT powder and BT powder, from the viewpoint of enhancing the sinterability of the porcelain. Its _composition, Li 2 O = 1 to 15 _mol%, SiO 2 = 40 to 60 mol%, BaO = 15 to 35 mol%, and CaO = 5 to 25 mol% is desirable.

  (B) Step: Next, a rectangular internal electrode pattern 23 is printed and formed on the main surface of the ceramic green sheet 21 obtained above. The conductor paste used as the internal electrode pattern 23 is prepared by mixing Ni, Cu or an alloy powder thereof as a main component metal, mixing ceramic powder as a co-material with this, and adding an organic binder, a solvent and a dispersant. As the metal powder, Ni is preferable because it enables simultaneous firing with the dielectric powder and is low in cost. The ceramic powder is preferably a BT powder having a low Ca concentration. However, the internal electrode layer 7 according to the present invention connects the upper and lower dielectric layers 5 through the electrode layer by containing the ceramic powder in the conductor paste. Thus, columnar ceramics are formed. Thereby, peeling between the dielectric layer 5 and the internal electrode layer 7 can be prevented. The ceramic powder used here can suppress abnormal grain growth of columnar ceramics during firing, and can increase mechanical strength. In addition, the capacitance temperature dependency of the multilayer ceramic capacitor can be reduced by suppressing the abnormal grain growth of the columnar ceramics formed in the internal electrode layer. The thickness of the internal electrode pattern 23 is preferably 1 μm or less because the multilayer ceramic capacitor is miniaturized and the steps due to the internal electrode pattern 23 are reduced.

  According to the present invention, the ceramic pattern 25 is formed around the internal electrode pattern 23 with substantially the same thickness as the internal electrode pattern 23 in order to eliminate the step due to the internal electrode pattern 23 on the ceramic green sheet 21. Is preferred. As the ceramic component constituting the ceramic pattern 25, it is preferable to use the dielectric powder in terms of making the firing shrinkage in the simultaneous firing the same.

  Step (c): Next, a desired number of ceramic green sheets 21 on which the internal electrode patterns 23 are formed are stacked, a plurality of ceramic green sheets 21 on which the internal electrode patterns 23 are not formed are the same, and the upper and lower layers are the same. The temporary laminated body is formed by overlapping the number of sheets. The internal electrode pattern 23 in the temporary laminate is shifted by a half pattern in the longitudinal direction. By such a laminating method, the internal electrode patterns 23 can be alternately exposed on the end faces of the cut laminate.

  In the present invention, as described above, in addition to the method of forming the internal electrode pattern 23 in advance on the main surface of the ceramic green sheet 21 and laminating it, the ceramic green sheet 21 is once brought into close contact with the lower layer side equipment. After the internal electrode pattern 23 is printed and dried, the ceramic green sheet 21 on which the internal electrode pattern 23 is not printed is overlaid and temporarily adhered onto the printed and dried internal electrode pattern 23. It can also be formed by a method in which the adhesion of the ceramic green sheet 21 and the printing of the internal electrode pattern 23 are sequentially performed.

  Next, the temporary laminated body is pressed under conditions of higher temperature and higher pressure than the temperature pressure during the temporary lamination to form a laminated body 29 in which the ceramic green sheet 21 and the internal electrode pattern 23 are firmly adhered.

  Next, the laminated body 29 is cut along the cutting line h, that is, approximately at the center of the ceramic pattern 29 formed in the laminated body in a direction perpendicular to the longitudinal direction of the internal electrode pattern 25 ((( c1) and (c2) of FIG. 4 are cut in parallel to the longitudinal direction of the internal electrode pattern 23 to form a capacitor body molded body so that the end of the internal electrode pattern 23 is exposed. On the other hand, in the widest portion of the internal electrode pattern 23, the internal electrode pattern is formed in an unexposed state on the side margin portion side.

  Next, this capacitor body molded body is fired under a predetermined atmosphere at a temperature condition to form a capacitor body. In some cases, the capacitor body is chamfered at the ridge line portion, and from the opposite end surface of the capacitor body. Barrel polishing may be performed to expose the exposed internal electrode layer. In the production method of the present invention, degreasing is in the temperature range up to 500 ° C., the heating rate is 5 to 20 ° C./h, the firing temperature is in the range of 1100 to 1250 ° C., and the heating rate from degreasing to the maximum temperature is 200 to 500 ° C./h, holding time at the maximum temperature of 0.5 to 4 hours, rate of cooling from the maximum temperature to 1000 ° C. is 200 to 500 ° C./h, atmosphere is hydrogen-nitrogen, heat treatment after firing (re- Oxidation treatment) It is preferable that the maximum temperature is 900 to 1100 ° C. and the atmosphere is nitrogen.

  Next, an external electrode paste is applied to the opposite ends of the capacitor body 1 and baked to form the external electrode 1. A plating film is formed on the surface of the external electrode 3 in order to improve mountability.

First, as raw material powders, BT powder, BCT powder (Ba _0.95 Ca _0.05 TiO ₃ ), MgO, Y ₂ O ₃ , MnCO ₃ and V ₂ O ₅ were prepared, and these various powders are shown in Table 1. Mixed at the indicated ratio. These raw material powders having a purity of 99.9% were used. The average particle diameters of the BT powder and the BCT powder are shown in Sample No. 1 in Table 1. About 1-22, all were 100 nm. Sample No. For No. 23, BT powder having an average particle size of 100 nm and BCT powder having an average particle size of 150 nm was used. The Ba / Ti ratio of the BT powder was 1.001, and the Ba / Ti ratio of the BCT powder was 1.003. As the sintering aid, glass powder having a composition of SiO ₂ = 55, BaO = 20, CaO = 15, and Li ₂ O = 10 (mol%) was used. The addition amount of the glass powder was 1 part by mass with respect to 100 parts by mass of the BT powder and the BCT powder.

  Next, these raw material powders were wet mixed by adding a mixed solvent of toluene and alcohol as a solvent using zirconia balls having a diameter of 5 mm.

  Next, a polyvinyl butyral resin and a mixed solvent of toluene and alcohol are added to the wet-mixed powder, and wet-mixed using a zirconia ball having a diameter of 5 mm to prepare a ceramic slurry, and a ceramic green sheet having a thickness of 3 μm by the doctor blade method. Was made.

  Next, a plurality of rectangular internal electrode patterns mainly composed of Ni were formed on the upper surface of the ceramic green sheet. The conductor paste used for the internal electrode pattern was Ni powder having an average particle size of 0.3 μm, and 30 parts by mass of BT powder used for a green sheet as a co-material with respect to 100 parts by mass of Ni powder.

Next, 360 ceramic green sheets on which internal electrode patterns were printed were laminated, and 20 ceramic green sheets on which the internal electrode patterns were not printed were laminated on the upper and lower surfaces, respectively. The layers were laminated together under the conditions of 10 ⁷ Pa and time 10 minutes, and cut into predetermined dimensions.

  Next, the laminated molded body was subjected to binder removal treatment at 300 ° C./h in the atmosphere at a heating rate of 10 ° C./h, and the temperature rising rate from 500 ° C. was 300 ° C./h. -A capacitor body was fabricated by firing at 1150-1200 ° C for 2 hours in nitrogen. In this case, sample no. About 11-13 and 18, it was set to 1150 degreeC and others set to 1200 degreeC.

The sample was then cooled to 1000 ° C. at a rate of 300 ° C./h, reoxidized at 1000 ° C. for 4 hours in a nitrogen atmosphere, and cooled at a rate of 300 ° C./h to produce a capacitor body. did. The size of the capacitor body was 0.95 × 0.48 × 0.48 mm ³ , and the thickness of the dielectric layer was 2 μm.

  Next, after the sintered electronic component body was barrel-polished, an external electrode paste containing Cu powder and glass was applied to both ends of the electronic component body, and baked at 850 ° C. to form external electrodes. Thereafter, using an electrolytic barrel machine, Ni plating and Sn plating were sequentially performed on the surface of the external electrode to produce a multilayer ceramic capacitor.

  Next, the following evaluation was performed on these multilayer ceramic capacitors. The capacitance was measured under the measurement conditions of a frequency of 1.0 kHz and a measurement voltage of 1 Vrms. The insulation resistance was evaluated for the capacitor body after firing with the external electrode formed thereon and with the external electrode formed after the re-oxidation treatment.

  The high temperature load test was performed by measuring the insulation resistance after leaving at a temperature of 140 ° C., a voltage of 30 V, and 100 hours. All of these were 30 samples.

Moreover, the average particle diameter of the BT type crystal particles and the BCT type crystal particles constituting the dielectric layer was determined by a scanning electron microscope (SEM). The polished surface is etched, 20 crystal particles in the electron micrograph are arbitrarily selected, the maximum diameter of each crystal particle is obtained by the intercept method, and the average value thereof and D ₉₀ (90% cumulative from small to large diameter) Value).

  Regarding the Ca concentration, an arbitrary place near the center was analyzed using a transmission electron microscope and EDS. At that time, dielectric particles having a high Ca concentration were used for those having a Ca concentration higher than 0.4 atomic% (rounded to the second decimal place). This analysis was performed on 100 to 150 main crystal particles. In the sample used in the examples, the state of the raw material powder used was maintained.

The concentrations of Mg and rare earth elements in the crystal particles 9 were analyzed by a transmission electron microscope and an analyzer (EPMA) attached thereto. In this case, the concentration of Mg and rare earth elements in each crystal particle was determined by performing elemental analysis by EDX at intervals of 5 nm from the surface to the inside of the selected crystal particle to determine the concentration distribution. In this case, the concentration ratio between the surface and the center of the crystal grain was determined. A crystal grain having an aspect ratio of 1.3 or less was selected as the center part of the crystal grain, and such a crystal grain was set in the vicinity of an intersection from two longitudinal and lateral directions. The results are shown in Table 1.

As is clear from the results in Table 1, the dielectric layer is composed of BT crystal particles and BCT crystal particles, and the BT crystal particles contain more Mg and rare earth elements than the BCT crystal particles. Further, the insulation resistance was 10 ⁷ Ω or more, and the insulation resistance after 100 hours of the high temperature load test was 8 × 10 ⁵ Ω or more, indicating high insulation.

When the content of barium titanate in the composite particles was 100 mol parts, sample No. 1 containing 0.1 to 0.4 mol parts of vanadium in terms of oxides. In 4 to 7, the insulation resistance after 100 hours of the high temperature load test was 1 × 10 ⁷ Ω or more.

  On the other hand, samples (sample Nos. 9 and 10) in which the dielectric layer is not composed of BT crystal particles and BCT crystal particles and sample Nos. To which V2O5 is not added. In No. 1, the insulation resistance after the main firing was not measurable.

It is a longitudinal cross-sectional view of the multilayer ceramic capacitor of this invention. (A) is a graph showing the concentration distribution of Mg and Y for BT crystal particles in the dielectric layer constituting the multilayer ceramic capacitor of the present invention, and (b) is in the dielectric layer constituting the multilayer ceramic capacitor of the present invention. It is a graph which shows density | concentration distribution of Mg and Y about a BCT crystal particle. It is process drawing which shows the manufacturing method of the multilayer ceramic capacitor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitor body 3 External electrode 5 Dielectric layer 7 Internal electrode layer 9 Crystal particle 9a BCT crystal particle 9b BT crystal particle 21 Ceramic green sheet 23 Internal electrode pattern 25 Ceramic pattern 29 Laminate

Claims (3)

A dielectric layer composed of barium titanate crystal particles (BT crystal particles) having a Ca concentration of 0.2 atomic percent or less and barium calcium titanate crystal particles (BCT crystal particles) having a Ca concentration of 0.4 atomic percent or more; In the multilayer ceramic capacitor in which the internal electrode layers are alternately stacked, the BT crystal particles and the BCT crystal particles contain Mg, a rare earth element, and vanadium, and Mg contained in a central portion of the BT crystal particles and A multilayer ceramic capacitor, wherein the content of rare earth elements is larger than the contents of Mg and rare earth elements contained in the central part of the BCT crystal particles. The multilayer ceramic capacitor according to claim 1, wherein an average particle diameter of the BT crystal particles is larger than an average particle diameter of the BCT crystal particles. 3. The multilayer ceramic capacitor according to claim 1, wherein vanadium is contained in an amount of 0.1 to 0.4 mol in terms of oxide when the amount of barium titanate in the dielectric layer is 100 mol.

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