JP2006041371A - Laminated ceramic capacitor, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized laminated ceramic capacitor having a high capacity, and to provide a manufacturing method of the capacitor wherein its dielectric constant is high in the range of the AC electric-field strength of 0.002-1 Vrms/μm, and it excels in the reliability comprising its capacity-temperature characteristic, its high-temperature-loaded life time, and the like, even if thinning its dielectric layers. <P>SOLUTION: In each dielectric layer of the laminated ceramic capacitor, there coexist with each other the barium titanate grains, having an alkaline-earth component concentration not higher than 0.2 atom% (BMTL), wherefrom Ba is excluded. and the barium titanate grains having an alkaline-earth component concentration equal to 0.5-2.5 atom% (BMTH), wherefrom Ba is excluded. Also, each dielectric layer satisfies the relation DL/DH=1.1 to 2, when the mean grain sizes of BMTL and BMTH are represented respectively by DL and DH. Further, in the body of the laminated ceramic capacitor, its dielectric layers and its inner-electrode layers are laminated alternately. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a multilayer ceramic capacitor and a method for producing the same, and in particular, is used for high-functional electronic devices such as personal computers and mobile phones, and extremely thin dielectric layers and internal electrode layers are alternately laminated, respectively. The present invention relates to a small-sized and high-capacity multilayer ceramic capacitor excellent in reliability such as a high-temperature load life and a manufacturing method thereof.

  In recent years, along with the downsizing and higher functionality of electronic devices, the multilayer ceramic capacitors used for this purpose have been required to be smaller and have higher capacity. In addition, as the characteristics of a multilayer ceramic capacitor, reliability such as capacity-temperature characteristics and high-temperature load life is improved. And as such a multilayer ceramic capacitor, what is disclosed by the following patent documents 1-3 is known, for example.

First, in the multilayer ceramic capacitor disclosed in Patent Document 1, in preparation of the dielectric ceramic, BaTiO ₃ and MgO are preliminarily calcined, and then various kinds of rare earth elements and acceptor elements are applied to the calcined powder. A method of adding an oxide is used. By adopting such a two-stage mixing method, even after firing, because of MgO previously dissolved, it enters into the BaTiO ₃ crystal particles of various oxides of rare earth elements and acceptor elements added later. It is described that the above-mentioned desired characteristics can be obtained as a result.

  In Patent Document 2, by forming a dielectric ceramic with two or more types of crystal particles having an average particle diameter of 0.1 to 0.3 μm and different capacity-temperature characteristics, the capacity-temperature characteristics are flat and the DC bias characteristics are achieved. It is described that an excellent multilayer ceramic capacitor can be obtained.

According to this publication, in a dielectric particle mainly composed of BaTiO ₃ , when a particle size becomes 1 μm or less, formation of a crystal particle called a core-shell structure, which realizes a flat capacity-temperature characteristic and an excellent DC bias characteristic, is realized. In this way, the dielectric particles having a particle size of 1 μm or less are further atomized to suppress the dielectric activity so that the flat capacitance-temperature characteristics and the excellent characteristics of the dielectric ceramic as a whole are excellent. DC bias characteristics are obtained.

In Patent Document 3, by using Ba _1−x Ca _x TiO _{3 in} which part of BaTiO ₃ constituting the dielectric ceramic is replaced with Ca, this also has flat capacitance temperature characteristics and excellent DC bias characteristics. It is described that it is obtained.
JP 2001-230149 A JP-A-9-241075 JP 2000-58378 A

However, since the multilayer ceramic capacitor disclosed in Patent Document 1 employs a preliminary process of pre-mixing BaTiO ₃ and MgO and calcining, the dielectric constant of the dielectric ceramic can be increased, In addition, the capacity temperature characteristic can satisfy the B characteristic (temperature range: −25 ° C. to 85 ° C., capacity change rate within ± 10%), but the capacity temperature characteristic is wide X7R (temperature range: −55). C.-125.degree. C., capacity change rate within ± 15%).

  Next, in the dielectric ceramic described in Patent Document 2, the relative permittivity increases only to about 2100 at most due to the atomization of the dielectric particles.

Also for the dielectric ceramic described in Patent Document 3, in Ba _1-x Ca _x TiO ₃ , the relative permittivity decreased greatly due to Ca substitution, and it was difficult to make the relative permittivity higher than 2000.

  In particular, the capacitor having the dielectric layer described in Patent Documents 1 to 3 has a low relative dielectric constant in an AC electric field strength range of 0.002 to 1 Vrms / μm.

  Therefore, even if the dielectric layer is thinned, the present invention has a high relative dielectric constant in the AC electric field strength range of 0.002 to 1 Vrms / μm and excellent reliability such as capacity-temperature characteristics and high-temperature load life. An object of the present invention is to provide a small-sized and high-capacity multilayer ceramic capacitor and a method for manufacturing the same.

The multilayer ceramic capacitor of the present invention has (1) barium titanate particles (BMTL) having an alkaline earth component concentration of 0.2 atomic% or less excluding Ba, and an alkaline earth component concentration of 0.5 to 2 excluding Ba. with .5 atomic% of barium titanate particles and (BMTH) coexist, an average particle size of BMTL DL, an average particle size of BMTH when _DH, and is the DL / DH = 1.1 to 2 It is characterized by comprising a capacitor body in which dielectric layers and internal electrode layers are alternately laminated.

  That is, according to the present invention, when two or more kinds of barium titanate particles having different alkaline earth component concentrations coexist, the barium titanate particles having a low alkaline earth component concentration and a large average particle size have a higher relative dielectric constant. The temperature characteristics of the dielectric constant can be flattened by the barium titanate particles having a high alkaline earth component concentration, and the barium titanate particles can be combined to form 0.002 to 1 Vrms / High dielectric constant in the AC electric field strength range of μm, temperature characteristics of dielectric constant can be flattened, and dielectric particles with low alkaline earth component concentration and dielectric particles with high alkaline earth component concentration coexist Therefore, the dielectric layer can be highly insulated.

  In this case, it is desirable that (2) the alkaline earth component is at least one selected from Mg, Ca, and Sr in that the relative permittivity can be maintained high and the temperature characteristics of the relative permittivity can be flattened. Further, (3) by setting the average particle diameters of BMTL and BMTH to 7 μm or less, the grain boundaries in the dielectric layer can be increased, and the insulation of the entire dielectric layer can be improved. Further, according to the present invention, (4) BMTL and BMTH both contain rare earth elements, and the concentration gradient is 0.05 atomic% / nm or more from the surface to the inside, with the particle surface being the highest concentration. It is desirable that the thickness of the dielectric layer is reduced, the capacity is increased, and the insulation is increased. (5) The thickness of the dielectric layer is more preferably 4 μm or less. The internal electrode layer is preferably composed mainly of a base metal in that the internal electrode material cost can be reduced.

Next, the multilayer ceramic capacitor described above is manufactured by the following manufacturing method. That is, the manufacturing method of the multilayer ceramic capacitor of the present invention includes (7) (a) BaTiO ₃ powder having an average particle diameter of 0.05 to 0.5 μm, and Ba ₁₋ having an average particle diameter smaller than that of the BaTiO ₃ powder. _x M _x TiO ₃ powder (M: Mg, Ca, Sr , X = 0.01~0.2) a step of preparing a, (b) the BaTiO ₃ powder and _{Ba 1-x} M x TiO ₃ powder (M : Mg, Ca, Sr, X = 0.01 to 0.2), alkaline earth oxides excluding Ba were added to each, and calcined at a temperature of 850 ° C. or less, respectively, and BaTiO ₃ calcined powder And Ba _1-x M _x TiO ₃ calcined powder, (c) the BaTiO ₃ calcined powder and Ba _1-x M _x TiO ₃ calcined powder, rare earth element compound, Mn compound and alkaline earth Oxide and organic behaviour And a step of preparing a slurry by mixing slurry at a predetermined ratio and forming the slurry to form a dielectric green sheet; and (d) a step of forming an internal electrode pattern on the main surface of the dielectric green sheet; And (e) forming a capacitor body molded body by laminating a plurality of dielectric green sheets on which internal electrode patterns are formed, and firing.

That is, according to the manufacturing method of the present invention, BaTiO ₃ having a different average particle size at the initial starting material stage and different sinterability and grain growth rate as a raw material powder for forming a dielectric ceramic. When using powder and Ba _1-x M _x TiO ₃ powder, in order to suppress the reaction between these powders during firing, alkaline earth elements excluding Ba are previously added to these powders at 850 ° C. or lower. Ba _1-x M _x containing an alkaline earth element is obtained by taking a method of partially dissolving at a low temperature and by dissolving an alkaline earth element in the calcined powder, particularly in the vicinity of the surface layer. from TiO ₃ powder side, it can suppress the diffusion of alkaline earth elements to less BaTiO ₃ side of alkaline earth elements, in maintaining the coexistence of different dielectric particles alkaline earth component concentration in the dielectric layer That.

  In addition, according to the technique in which the alkaline earth component is partially dissolved in both raw material powders at a low temperature of 850 ° C. or less, the solid solution of rare earth elements and other additives to be added later to both raw material powders is reduced. Can also be suppressed.

In this case, the ratio of the alkaline earth element oxide added in the step (8) (b) is 30 to 60% of the oxide of all the alkaline earth elements added in the step (b) (c). In particular, according to the present invention, (9) if the oxide of the alkaline earth element is MgO, for example, the Ba ion of BaTiO ₃ can be increased. Therefore, the solid solution amount of ions in BaTiO ₃ can be reduced.

On the other hand, (10) When M in the Ba _1-x M _x TiO ₃ powder is Ca, an element smaller than M such as Mg is dissolved in the BaTiO ₃ in advance, so that it diffuses later. Diffusion of alkaline earth elements having a large ionic radius such as coming Ca can be suppressed. In other words, the effect of adding the alkaline earth element to the BaTiO ₃ powder in the present invention is such that the smaller the ion radius of the alkaline earth element previously added to the BaTiO ₃ powder is, the more Ba _1-x M _x TiO ₃ powder side is. The diffusion of alkaline earth components from can be suppressed. Furthermore, the internal electrode pattern in the above manufacturing method is preferably composed mainly of a base metal in terms of low cost, and it is desirable to use a conductive pattern made of a plating film in that it can be made thinner.

(Multilayer ceramic capacitor structure)
The multilayer ceramic capacitor of the present invention will be described in detail based on the schematic sectional view of FIG. The multilayer ceramic capacitor of the present invention is configured by forming external electrodes 3 at both ends of a 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 formed by alternately laminating dielectric layers 5 and internal electrode layers 7. The dielectric layer 5 is composed of dielectric particles 11 having Ba and Ti as main components with a low M concentration, dielectric particles 13 having Ba and Ti as main components and a grain boundary phase 15 having a high M concentration. The thickness is preferably 4 μm or less, particularly 3 μm or less from the viewpoint of increasing the capacitance, and 0.5 μm or more, particularly 1 μm or more from the viewpoint of maintaining high insulation. Furthermore, in the present invention, it is more desirable that the thickness variation of the dielectric layer 5 is within 10% in order to stabilize the capacitance variation and capacitance temperature characteristics.

  The internal electrode layer 7 is preferably a base metal such as Ni or Cu from the viewpoint that the manufacturing cost can be suppressed even if the internal electrode layer 7 is made highly laminated, and particularly Ni is more preferable from the viewpoint of simultaneous firing with the dielectric layer of the present invention. . The thickness of the internal electrode layer 7 is preferably 2 μm or less on average.

In particular, in the present invention, (1) BaTiO ₃ particles (BMTL) having an alkaline earth component concentration excluding Ba of 0.2 atomic% or less and an alkaline earth component concentration excluding Ba of 0.5 to 2.5 atomic%. with the BaTiO ₃ particles and (BMTH) coexist, DL an average particle size of BMTL, an average particle size of BMTH _DH, and were at the time, it is important that the DL / DH = 1.1 to 2 .

  When the alkaline earth component concentration of the BMTL particles having a low alkaline earth component concentration is 0.3 atomic% or more, while the alkaline earth component concentration of BMTH is 0.4 atomic% or less, the alkaline earth elements of BMTL and BMTH Concentrations overlap, and it becomes difficult to express the characteristics of the dielectric constant and temperature characteristics of the dielectric particles due to the difference in alkaline earth element concentration, and the coexistence effect of both dielectric particles decreases. Further, when the alkaline earth component concentration of BMTH is 2.5 atomic% or more, the decrease in the relative dielectric constant of BMTH becomes large.

  Further, when the DL / DH ratio is smaller than 1.1, the increase in the relative dielectric constant in the AC electric field of 0.002 to 1 Vrms / μm is not large, while when the DBMTL / DBMTH ratio is larger than 2, Capacitance-temperature characteristics increase. Further, BL / BH = 1 to 1.5 is more preferable in terms of further improving the relative dielectric constant and its temperature characteristics.

The alkaline earth component dissolved in the BMTH particles having a high ratio of alkaline earth elements in the present invention is preferably at least one selected from Mg, Ca, and Sr. In particular, BaTiO ₃ Ca is more desirable in that it has a high solid solution ratio, improves the relative dielectric constant of BaTiO ₃ and improves its temperature characteristics.

  In addition, according to the present invention, the average particle diameters of BMTL and BMTH are both 0.7 μm or less, particularly 0.6 μm or less, which is more desirable in terms of achieving high insulation, and 0 in terms of increasing the relative dielectric constant. .2 μm or more is desirable.

  Furthermore, the dielectric layer 5 has a thickness of 4 μm or less, and the internal electrode layer 7 is made of a base metal (Cu, Ni, Co, etc.), in particular, the sintering temperature of the metal matches the sintering temperature of the dielectric material. Ni is preferable in this respect.

  Further, in the dielectric layer 5 according to the present invention, the rare earth element has a concentration gradient from the crystal grain surface to the inside of the grain with the grain boundary phase 15 which is the grain surface as the maximum concentration, and is 0.05 atomic% / nm or more. It is preferable.

  That is, when the concentration gradient of the rare earth element is in such a condition, it is possible to obtain a capacitor that satisfies the X7R standard as a capacity temperature characteristic as well as an improvement in relative permittivity and high temperature load life.

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

Further, as described above, the BaTiO ₃ crystal particles of the present invention have Mg dissolved in the surface region by calcination, but the Mg concentration gradient in the surface region of the BaTiO ₃ crystal particles is rare earth element. In view of enhancing the suppression of diffusion solid solution, it is desirable that the grain boundary part is set to a high concentration side and 0.003 atomic% / nm or more, desirably 0.01 atomic% / nm or more toward the grain. .

(Manufacturing method)
The production method of the present invention comprises: (a) BaTiO ₃ powder having an average particle diameter of 0.05 to 0.5 μm, and Ba _1-x M _x TiO ₃ (M: Mg, which has an average particle diameter smaller than that of the BaTiO ₃ powder). (Ca, Sr, X = 0.01-0.2) a step of preparing a powder, and (b) an alkaline earth element excluding Ba in the BaTiO ₃ powder and Ba _1-x M _x TiO ₃ powder, respectively. Of BaTiO ₃ and Ba _1-x M _x TiO ₃ (M: Mg, Ca, Sr, X = 0.01 to 0.2). And a step of preparing a calcined powder. Here, a BaTiO ₃ powder and a Ba _1-x M _x TiO ₃ powder were calcined at a temperature of 850 ° C. or less, and a powder in which an oxide of an alkaline earth element was formed as a solid solution on both powder surfaces was obtained. It is important to prepare, and it is desirable that the alkaline earth element oxide is present on the surfaces of both powders.

As the main raw material BaTiO ₃ powder and Ba _1-x M _x TiO ₃ powder used here, a powder obtained by a hydrothermal synthesis method is desirable because the particle size distribution is narrow and the crystallinity is high. .2 μm or more and 0.4 μm or less are desirable. In addition, the specific surface area of such a fine powder is preferably 1.7 to 6.6 (m ² / g). On the other hand, it is important that the average particle size of the Ba _1-x M _x TiO ₃ powder is smaller than that of the BaTiO ₃ powder, and is 0.04 to 0.4 μm, particularly 0.15 to 0.35 μm. Is more preferable.

That is, in the present invention, for example, BaTiO ₃ powder in which MgO is solid-dissolved on the surface is formed by low-temperature calcination, and due to the reason that the AC electric field characteristics after firing are enhanced, it is accompanied by appropriate grain growth and has high reactivity. Since it is necessary to make it into the powder which has, it is desirable to prescribe | regulate the above-mentioned range also to a specific surface area with an average particle diameter.

As the calcining temperature in the production method of the present invention, BaTiO ₃ powder in which MgO is solid-dissolved as described above and Ba _1-x M _x TiO ₃ (M: Mg, Ca, Sr, X = 0.01-0. 2) 850 ° C. or lower, particularly 750 ° C. or lower is desirable for suppressing MgO solid solution in the powder. On the other hand, 600 is used for ensuring reliable diffusion solid solution of MgO on the BaTiO ₃ powder surface. It is desirable that the temperature be 650 ° C. or higher. The average particle diameter of the MgO powder used here is preferably 0.3 μm or less in view of increasing the coating rate on the surface of the BaTiO ₃ powder. In the present invention, by using BaTiO ₃ powder preliminarily calcined with an oxide of an alkaline earth element as described above, diffusion solid solution of rare earth elements can be suppressed and grain growth can also be suppressed.

On the other hand, when the calcination temperature for dissolving an oxide of an alkaline earth element such as MgO in the BaTiO ₃ and Ba _1-x M _x TiO ₃ powder is higher than 850 ° C., the grain boundary Oxidation of alkaline earth elements in the vicinity is easy to diffuse and dissolve, so that the diffusion and solid solution of rare earth elements progresses, so the grain growth of dielectric particles having a low M concentration and mainly composed of barium titanate As a result, the temperature characteristics of the capacitance cannot satisfy the desired characteristics.

Further, for the above-described treatment of the present invention, BaTiO ₃ powder and Ba _1-x M _x TiO ₃ powder and Ba _1-x M _x TiO ₃ powder are not subjected to, for example, a treatment in which MgO is first solid-dissolved, and BaTiO ₃ powder or Ba _1-x M _x When added together with additives such as TiO _{3 and} rare earth elements _, it is difficult to form a solid solution of MgO on the surface layer of BaTiO ₃ , so M from Ba _1-x M _x TiO ₃ The diffusion of components and the like increases, and the inherent dielectric constant of BaTiO ₃ cannot be maintained, resulting in a decrease in capacitance. In addition, grain growth tends to occur. In Ba _1-x M _x TiO _3, M is preferably Ca, and X is preferably in the range of 0.02 to 0.1 because the relative permittivity can be increased and the capacitance-temperature characteristics can be flattened.

The ratio of the alkaline earth element oxides excluding Ba added in the step (b) of this production method is 30 to 60% of the total alkaline earth element oxide added in the steps (b) and (c). % Is preferred, MgO is preferred as the alkaline earth element, and Ca is preferred as the M component in Ba _1-x M _x TiO ₃ . Moreover, although the dielectric material layer concerning this invention contains a glass phase, Si-Li-Ca type | system | group glass powder is suitable as this glass phase.

Next, (c) the BaTiO ₃ calcined powder, the Ba _1-x M _x TiO ₃ calcined powder, a rare earth element compound, a Mn compound, the remaining alkaline earth element oxide, and an organic vehicle Are mixed at a predetermined ratio to prepare a slurry, which is then molded to form a dielectric green sheet. The molding using the above-described slurry is preferably a sheet molding method such as a die coater, and the thickness of the dielectric green sheet formed by such a molding method is preferably 5 μm or less, and particularly preferably 4 μm or less.

  Next, (d) an internal electrode pattern is formed on the main surface of the dielectric green sheet. The internal electrode pattern is formed, for example, by screen printing of a base metal powder such as Ni or Cu that is pasted together with an organic resin or a solvent. The thickness of the internal electrode pattern is preferably smaller than the thickness of the dielectric green sheet and 4 μm or less in terms of reducing the level difference on the dielectric green sheet.

  Next, (e) a plurality of dielectric green sheets on which internal electrode patterns are formed are laminated to form a capacitor body molded body, and then the capacitor body is heated in the atmosphere at a rate of 40 to 80 ° C./h. The binder removal treatment is performed at 400 to 500 ° C., and then the temperature rise rate from 500 ° C. is set to 100 to 400 ° C./h in a reducing atmosphere, followed by baking at a temperature of 1100 to 1300 ° C. for 2 to 5 hours. Cooling is performed at a temperature drop rate of 80 to 400 ° C./h, and reoxidation is performed at 750 to 1100 ° C. in an air atmosphere.

  Finally, the external electrode 3 is formed by applying an external electrode paste on both end faces of the fired capacitor body and baking it in nitrogen, whereby the multilayer ceramic capacitor of the present invention can be obtained.

The multilayer ceramic capacitor of the present invention was produced as follows. First, with respect to 100 mol parts of BaTiO ₃ (BT) + (Ba _0.95 Ca _0.05 ) TiO ₃ (BCT) having an average particle diameter shown in Table 1, 0.25 mol parts of MgO are weighed sufficiently. Mix and heat at the temperature shown in Table 1 for 2 hours. Next, the amount of rare earth elements shown in Table 1 and 0.3 mol part of MnCO ₃ with respect to 100 mol parts of the mixed powder of BaTiO ₃ + (Ba _0.95 Ca _0.05 ) TiO ₃ calcinated. , 0.25 mol part of MgO was mixed.

Next, 0.5 part by mass of additive components composed of Li ₂ O, SiO ₂ and CaO is mixed with 100 parts by mass of BaTiO ₃ + (Ba _0.95 Ca _0.05 ) TiO ₃ , and this mixed powder is mixed. A slurry was prepared by wet grinding with a ball mill using ZrO ₂ balls having a diameter of 5 mmφ and adding an organic binder. Next, using this slurry, a dielectric green sheet having a thickness of 4 μm was prepared by a doctor blade.

  Next, a conductive paste containing Ni metal was screen printed on the dielectric green sheet to form an internal electrode pattern.

  Next, 388 dielectric green sheets on which internal electrode patterns are formed are stacked, and 20 dielectric green sheets on which internal electrode patterns are not formed are stacked on the upper and lower surfaces, and are integrated using a press. A laminate was obtained.

  Thereafter, the base laminate was cut into a lattice shape to produce a capacitor body molded body of 2.3 mm × 1.5 mm × 1.5 mm.

Next, this capacitor body molded body was subjected to binder removal treatment at 500 ° C. in the atmosphere at a temperature increase rate of 50 ° C./h, and the temperature increase rate from 500 ° C. was 1240 ° C. at a temperature increase rate of 200 ° C./h. (Oxygen partial pressure 10 ⁻¹¹ atm) calcination for 2 hours, cooling to 800 ° C. at a temperature decrease rate of 200 ° C./h, followed by re-oxidation treatment at 800 ° C. for 4 hours in air atmosphere, The capacitor body was manufactured by cooling at a temperature drop rate of. The thickness of the dielectric layer was 2.3 μm.

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

  Next, the capacitance and dielectric loss of these samples, which were the produced multilayer ceramic capacitors, were measured at a frequency of 1.0 kHz and an input signal level of 0.5 V using an LCR meter 4284A. The relative dielectric constant was calculated from the capacitance, the effective area of the internal electrode layer, and the thickness of the dielectric layer.

  Subsequently, the temperature characteristics of the capacitance were measured in a range of −55 to 125 ° C. with reference to the capacitance at 25 ° C. The high temperature load test was performed for 1000 hours under the conditions of a temperature of 125 ° C. and a voltage of 9.45 V, and the change in insulation resistance was measured for 30 samples. In this case, a non-defective one was considered good. In addition, the crystal particle diameter and its variation were measured using photographs taken with an electron microscope by the intercept method.

  In addition, the presence of rare earth elements in the crystal grains constituting the dielectric layer was evaluated using a transmission electron microscope and limited-field electron diffraction image analysis on a cross-polished sample.

  Moreover, regarding the Ca concentration, an arbitrary place in the vicinity of the central portion was analyzed using a transmission electron microscope and EDS. At that time, those having a Ca concentration higher than 0.3 at% (rounded to the second decimal place) were made dielectric particles having a high Ca concentration. This analysis was performed on 100 to 150 main crystal particles.

  The average crystal grain size of the crystal particles in the sample of the present invention is 0.4 μm for dielectric particles (BMTL) mainly composed of Ba and Ti having a low Ca concentration, and mainly composed of Ba and Ti having a high Ca concentration. The dielectric particle (BMTH) was 0.3 μm. Further, both of the BMTL and BMTH particles had an average crystal grain size variation (CV value) of 0.5 or less.

As a comparative example, when the raw material particle size is 0.4 μm for BaTiO ₃ and 0.35 μm for (Ba _0.95 Ca _0.05 ) TiO _{3, the} calcining temperature of MgO to BaTiO ₃ is 1150 ° C. The other additive compositions and procedures were the same as those in the process of the present invention (No. 1). In addition, as a comparative example, only BaTiO ₃ powder or (Ba _0.95 Ca _0.05 ) TiO ₃ powder was used, and the other additive compositions and procedures were the same as those in the above-described process of the present invention. (No. 2, 3)

  As is apparent from Tables 1 and 2, sample Nos. Produced using the production method of the present invention. 4-No. 11, the relative dielectric constant was 3100 or more in the range of the AC electric field of 0.02 to 1 Vrms / μm, the capacitance-temperature characteristic satisfied the X7R standard, and the insulation resistance also satisfied 10 GΩ.

  On the other hand, sample No. 1 calcined at 1150 ° C. In No. 1, DL / DH = 0.9, the temperature characteristics of the capacitance were increased, and the X7R characteristics were not satisfied. Also, BMTL alone did not satisfy the X7R characteristics. In addition, in the case of dielectric particles of BMTH alone, the insulation resistance was as low as 0.2 GΩ.

It is a schematic sectional drawing of the multilayer ceramic capacitor of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Capacitor main body 5 ... Dielectric layer 7 ... Internal electrode layer 11 ... Dielectric particle | grains 13 which have a low M density | concentration and which have Ba and Ti as a main component ... A high M density | concentration Ba and Ti Dielectric particle 15 with grain as the main component ...

Claims (11)

Barium titanate particles (BMTL) having an alkaline earth component concentration of 0.2 atomic percent or less excluding Ba, and barium titanate particles (BMTH) having an alkaline earth component concentration of 0.5 to 2.5 atomic percent excluding Ba ) Coexist with
The average particle size of BMTL is DL,
The average particle size of BMTH is DH _,
And when
A multilayer ceramic capacitor comprising a capacitor body in which dielectric layers having DL / DH = 1.1 to 2 and internal electrode layers are alternately stacked. 2. The multilayer ceramic capacitor according to claim 1, wherein the alkaline earth component is at least one selected from Mg, Ca, and Sr. 3. The multilayer ceramic capacitor according to claim 1, wherein the average particle diameters of BMTL and BMTH are both 0.7 μm or less. The BMTL and the BMTH both contain a rare earth element, and the concentration gradient is 0.05 atomic% / nm or more from the surface to the inside with the particle surface being the highest concentration. Multilayer ceramic capacitor. The multilayer ceramic capacitor according to claim 1, wherein the dielectric layer has a thickness of 4 μm or less. The multilayer ceramic capacitor according to claim 1, wherein the internal electrode layer contains a base metal as a main component. (A) BaTiO ₃ powder having an average particle size of 0.05 to 0.5 [mu] m, and an average particle size of the BaTiO ₃ small _{Ba 1-x} M x TiO ₃ powder than powder (M: Mg, Ca, Sr , Preparing X = 0.01-0.2);
(B) To each of the BaTiO ₃ powder and Ba _1-x M _x TiO ₃ powder (M: Mg, Ca, Sr, X = 0.01 to 0.2), an alkaline earth oxide excluding Ba is added. And calcining at a temperature of 850 ° C. or less to prepare BaTiO ₃ calcined powder and Ba _1-x M _x TiO ₃ calcined powder,
(C) The BaTiO ₃ calcined powder and Ba _1-x M _x TiO ₃ calcined powder, rare earth element compound, Mn compound and alkaline earth oxide, and organic vehicle are mixed at a predetermined ratio to obtain a slurry. Preparing and molding to form a dielectric green sheet;
(D) forming an internal electrode pattern on the main surface of the dielectric green sheet;
And (e) forming a capacitor body molded body by laminating a plurality of dielectric green sheets on which internal electrode patterns are formed, and firing the multilayer ceramic capacitor. The ratio of the alkaline earth element oxide added in the step (b) is a molar ratio (mass ratio), and is 30 to 60% of the total alkaline earth element oxide added in the steps (b) and (c). A method for producing a multilayer ceramic capacitor according to claim 7. The method for producing a multilayer ceramic capacitor according to claim 7 or 8, wherein the oxide of the alkaline earth element is MgO. The method for producing a multilayer ceramic capacitor according to claim 7, wherein M in the Ba _1-x M _x TiO ₃ powder is Ca. The method for producing a multilayer ceramic capacitor according to claim 7, wherein the internal electrode pattern contains a base metal as a main component.

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