TWI412045B - Laminated ceramic capacitors - Google Patents

Abstract

Disclosed is a laminated ceramic capacitor comprising a dielectric ceramic that is composed mainly of barium titanate and contains vanadium, magnesium, manganese, rare earth elements stated in the description, and terbium in respective proportions specified in the description. The crystal constituting the dielectric ceramic comprises a first group of crystals formed of first crystal grains having a calcium concentration of not more than 0.2 atomic% and a second group of crystals formed of second crystal grains having a calcium concentration of not less than 0.4 atomic%. The dielectric ceramic satisfies a requirement of C2/(C1 + C2) of 0.3 to 0.7 wherein C1 represents the area of the first crystal grains that appear on a polished surface of the dielectric ceramic; and C2 represents the area of the second crystal grains that appear on the polished surface of the dielectric ceramic. In an X-ray diffraction chart for the dielectric ceramic, the diffraction intensity of (200) plane attributable to cubic barium titanate is larger than the diffraction intensity of (002) plane attributable to tetragonal barium titanate. The Curie temperature is 95 to 105°C.

Description

Multilayer ceramic capacitor

The present invention relates to a multilayer ceramic capacitor, and more particularly to a small-sized and high-capacitance multilayer ceramic capacitor in which a dielectric layer is composed of barium titanate having a different calcium concentration.

In recent years, with the spread of mobile devices such as mobile phones and the high-speed and high-frequency of semiconductor devices, which are main components of personal computers, etc., the multilayer ceramic capacitors mounted on such electronic devices are small and highly capacitive. Increasingly demanding. Therefore, for the dielectric layer constituting the laminated ceramic capacitor, thinning and high buildup are required.

Further, as a dielectric ceramic which is a dielectric layer constituting a laminated ceramic capacitor, a dielectric material containing barium titanate as a main component has been conventionally used. In recent years, a composite dielectric material in which barium titanate powder is mixed with a powder in which calcium is dissolved in barium titanate to coexist the dielectric materials is being developed and applied to a laminated ceramic capacitor (for example). Refer to Patent Document 1).

In the dielectric ceramic produced by using the above-described barium titanate powder and a powder in which calcium is dissolved in barium titanate, each oxide of magnesium, a rare earth element, and manganese is used as an additive. Then, at the time of calcination, the additives are solid-dissolved in the vicinity of the surface of each of the barium titanate powder and the powder in which the calcium is solid-dissolved in the barium titanate to form a crystal having a so-called core-shell structure to realize dielectric. The constant and the temperature characteristics of the dielectric constant are improved.

Here, the core-shell structure of a crystal grain refers to a structure in which a core portion which is a central portion of a crystal grain and a shell portion which is a shell portion form a physically and chemically different phase. The crystal grains containing barium titanate as a main component have a state in which the core portion is occupied by the crystal phase of the tetragonal crystal and the shell portion is occupied by the crystal phase of the cubic crystal.

A dielectric ceramic having a dielectric ceramic composed of such a core-shell structure is used as a multilayer ceramic capacitor of a dielectric layer, and the dielectric constant is improved, and the temperature characteristic of the dielectric constant satisfies X7R (based on 25 ° C as a reference) The temperature change rate of the electric constant is within ±15% at -55 to 125 °C). Further, the change in the dielectric constant when the applied AC voltage is increased is small.

However, in the above-mentioned multilayer ceramic capacitor, when the thickness of the dielectric layer is thinned to, for example, about 2 μm, there is a problem that the life characteristics in the high-temperature load test are largely lowered.

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-156450

An object of the present invention is to provide a multilayer ceramic capacitor having a dielectric layer which is excellent in stability of temperature characteristics of a high dielectric constant and a dielectric constant, and a dielectric constant when an AC voltage is increased. The increase is small and the life characteristics are excellent in the high temperature load test.

The multilayer ceramic capacitor of the present invention is formed by alternately laminating a dielectric layer and an internal electrode layer containing barium titanate as a main component and containing calcium, magnesium, vanadium, manganese, and lanthanum, and self-enthalpy. A dielectric ceramic of at least one rare earth element selected from the group consisting of ruthenium, osmium and iridium. In the above-mentioned dielectric ceramic, the above-mentioned vanadium in an amount of 0.02 to 0.2 mol in terms of V ₂ O _{5 is} contained in the range of 0.2 to 0.8 mol in terms of MgO, in terms of 100 mol of titanium constituting the barium titanate. Magnesium, in terms of MnO, is 0.1 to 0.5 mol of the above-mentioned manganese, and is at least one of the above-mentioned rare earth elements selected from the group consisting of ruthenium, osmium, iridium and osmium in an amount of 0.3 to 0.8 mol in terms of RE ₂ O ₃ . The above-mentioned enthalpy of 0.02 to 0.2 m is calculated in terms of Tb ₄ O ₇ conversion. The crystal constituting the dielectric ceramic has a first crystal group composed of the first crystal grains having the barium titanate as a main component and the calcium concentration of 0.2 atom% or less; and the second crystal The group consists of a second crystal grain having the above-mentioned barium titanate as a main component and having a calcium concentration of 0.4 atom% or more. When the area of the first crystal grain observed on the polished surface of the dielectric ceramic is C1 and the area of the second crystal grain is C2, C2/(C1+C2) is 0.3~ 0.7. In the X-ray diffraction pattern of the above dielectric ceramic, it is shown that the diffraction intensity of the (200) plane of the cubic crystal of barium titanate is larger than the diffraction intensity of the (002) plane of the barium titanate exhibiting tetragonal crystal. The Curie temperature is 95~105 °C.

Further, the above rare earth element is represented by RE, which is based on the English notation (Rare earth) of the rare earth element in the periodic table.

According to the present invention, a multilayer ceramic capacitor having a dielectric layer having a high dielectric constant and a decrease in dielectric constant temperature change can be obtained. The rate is small, and the increase in the dielectric constant when the applied AC voltage is increased is small (the AC voltage dependence of the dielectric constant is small), and the lifetime in the high-temperature load test is excellent.

The multilayer ceramic capacitor of the present invention will be described in detail with reference to Figs. 1 and 2 . As shown in FIG. 1, the multilayer ceramic capacitor of the present invention has external electrodes 3 formed at both end portions of the capacitor body 1. The external electrode 3 is formed, for example, by firing an alloy paste of Cu or Cu and Ni.

The capacitor body 1 is configured by alternately laminating a dielectric layer 5 made of a dielectric ceramic and an internal electrode layer 7. In Fig. 1, the laminated state of the dielectric layer 5 and the internal electrode layer 7 is simplified. The multilayer ceramic capacitor of the present invention has a dielectric layer 5 and an internal electrode layer 7 of up to several hundred layers.

As shown in FIG. 2, the dielectric layer 5 composed of a dielectric ceramic is composed of crystal grains 9 and a grain boundary phase 11. The thickness of the dielectric layer 5 is preferably 2 μm or less, and particularly preferably 1 μm or less. Thereby, the multilayer ceramic capacitor can be made small and high in capacitance. Further, when the thickness of the dielectric layer 5 is 0.4 μm or more, the unevenness of the capacitance can be reduced, and the capacitance temperature characteristics can be stabilized.

As a material for forming the internal electrode layer 7, even if the high buildup can suppress the manufacturing cost, it is preferable to use a base metal such as Ni or Cu, in particular, simultaneously with the dielectric layer 5 of the present invention. In terms of calcination, Ni is more preferable.

The dielectric ceramic constituting the dielectric layer 5 in the multilayer ceramic capacitor of the present invention contains barium titanate as a main component and contains calcium (Ca), magnesium (Mg), vanadium (V), and manganese (Mn). And strontium (Tb) and a sintered body of at least one rare earth element (RE) selected from the group consisting of yttrium (Y), yttrium (Dy), yttrium (Ho), and yttrium (Er).

The sintered body contains 0.02 to 0.2 m of vanadium in terms of V ₂ O _{5 and} 0.2 to 0.8 m of magnesium in terms of MgO, in terms of MnO, in terms of 100 mol of titanium constituting barium titanate. It is 0.1 to 0.5 mol of manganese, and is at least one rare earth element selected from the group consisting of ruthenium, osmium, iridium and osmium in the range of 0.3 to 0.8 mol in terms of RE ₂ O ₃ , and is calculated in terms of Tb ₄ O ₇ 0.02~0.2 moles.

Further, the crystal grains 9 formed in the dielectric ceramic are composed of the first crystal grains 9a and the second crystal grains 9b, and the first crystal grains 9a are composed of barium titanate as a main component and having a calcium concentration of a first crystal group composed of crystal grains of 0.2 atom% or less, and the second crystal grain 9b constitutes a second crystal group composed of crystal grains having barium titanate as a main component and having a calcium concentration of 0.4 atom% or more. group. A grain boundary phase 11 is formed between the crystal grains 9, 9. The main component of the grain boundary phase 11 is a glass component, and partially contains an auxiliary component such as magnesium, vanadium, manganese, cerium, or a rare earth element contained in the dielectric ceramic.

In the dielectric ceramic, the ratio of the first crystal grains 9a to the second crystal grains 9b is such that the area of the first crystal grains 9a observed on the polished surface of the dielectric ceramic is C1. When the area of the second crystal grain 9b is C2, C2/(C1+C2) is 0.3 to 0.7.

Further, in the X-ray diffraction pattern of the dielectric ceramic, the diffraction intensity of the (200) plane of the cubic crystal of barium titanate is larger than the diffraction intensity of the (002) plane of the barium titanate exhibiting tetragonal, And the Curie temperature is 95~105 °C.

The dielectric ceramic of the present invention having such a specific configuration has a dielectric constant at room temperature (25 ° C) of 3,500 or more, a dielectric loss of 12.5% or less, and a temperature characteristic of a dielectric constant satisfying X6S (ie, The temperature change rate of the dielectric constant at 25 ° C is within ±22% from -55 to 105 ° C, and may be simply referred to as "X6S" hereinafter. Further, in the dielectric ceramic, when the AC voltage is 1 V, the dielectric constant is twice or less the dielectric constant when the AC voltage is 0.01 V. Further, in the high-temperature load test (temperature: 105 ° C, voltage: 1.5 times the rated voltage, test time: 1000 hours, hereinafter sometimes referred to as "high-temperature load test"), the occurrence of defects is suppressed. Therefore, the multilayer ceramic capacitor of the present invention having the dielectric layer 5 composed of the dielectric ceramic has high reliability. Hereinafter, the reason will be described in detail.

In other words, when the content of vanadium is less than 0.02 mol in terms of V ₂ O ₅ with respect to 100 mol of titanium constituting barium titanate, the reliability in the high-temperature load test is lowered. On the other hand, if the content of vanadium is more than 0.2 mol in terms of V ₂ O ₅ , the dielectric constant at room temperature becomes low.

With respect to 100 mol of titanium constituting barium titanate, if the content of magnesium is less than 0.2 mol in terms of MgO, the temperature characteristic of the dielectric constant is likely to largely deviate from the + side, and the temperature characteristic as an electrostatic capacitance is not satisfied. The X6S condition. another On the one hand, if the content of magnesium is more than 0.8 mol, the dielectric constant at room temperature becomes low.

With respect to 100 mol of titanium constituting barium titanate, if the content of manganese is less than 0.1 mol in terms of MnO, the insulation resistance of the dielectric layer 5 is lowered, so that the reliability in the high-temperature load test is lowered. On the other hand, if the content of manganese is more than 0.5 mol in terms of MnO, the dielectric constant at room temperature becomes low.

The content of at least one rare earth element selected from lanthanum, cerium, lanthanum and cerium is less than 0.3 mol in terms of RE ₂ O ₃ relative to 100 mol of titanium constituting barium titanate, in the high temperature load test Reliability is declining. On the other hand, when the content of the rare earth element is more than 0.8 mol in terms of RE ₂ O ₃ , the dielectric constant at room temperature becomes low.

100 parts of titanium constituting barium titanate, and if the content of strontium is less than 0.02 mol in terms of Tb ₄ O ₇ , vanadium, magnesium, manganese and rare earth elements in barium titanate as a main component The amount of solid solution is reduced. Therefore, the Curie temperature of the dielectric ceramic is equivalent to the Curie temperature (about 125 ° C) of the barium titanate showing the core-shell structure, and the reliability under the high temperature load test is lowered. On the other hand, when the content of niobium is more than 0.2 mol in terms of Tb ₄ O ₇ , the amount of solid solution of vanadium, magnesium, manganese, and a rare earth element in barium titanate as a main component increases. Therefore, compared with the dielectric constant when the AC voltage is set to 0.01 V, the dielectric constant increases when the AC voltage is 1 V (the AC voltage dependence of the dielectric constant is large), and the rated voltage changes. The change in the electrostatic capacitance of the dielectric ceramic becomes large.

The composition of the preferred dielectric ceramic is preferably 0.02 to 0.08 mol of vanadium in terms of V ₂ O ₅ with respect to 100 mol of titanium constituting barium titanate, and 0.3 to 0.6 in terms of MgO. Molybdenum magnesium, which is 0.2 to 0.4 mol of manganese in terms of MnO, and is at least one rare earth element selected from the group consisting of ~, 镝, 鈥, and 0.4 in the range of 0.4 to 0.6 mol in terms of RE ₂ O ₃ , and It is 0.02 to 0.08 moles in terms of Tb ₄ O ₇ conversion.

The dielectric ceramics having the composition can increase the dielectric constant at room temperature to 3700 or more, and the dielectric constant when the AC voltage is 1 V can be set to be 0.01 V when the AC voltage is set to 0.01 V. The electrical constant is 1.5 times or less. Further, as the rare earth element, a higher dielectric constant and a higher insulation resistance are preferable.

Further, the dielectric ceramic is preferably contained in an amount of 0.05 to 0.08 mol in terms of Tb ₄ O ₇ with respect to 100 mol of titanium constituting barium titanate. Thereby, the coefficient of variation (σ/x, σ: standard deviation, x: average value) of the dielectric constant of the dielectric ceramic can be reduced. Therefore, in the case of manufacturing a laminated ceramic capacitor, even if there is a difference in the calcination temperature, a laminated ceramic capacitor having a small uneven capacitance can be obtained.

Further, as described above, in the dielectric ceramic, the ratio of the first crystal grains 9a to the second crystal grains 9b is such that the first crystal grains 9a are observed on the polished surface of the dielectric ceramic. When the area is C1 and the area of the second crystal grain 9b is C2, C2/(C1+C2) is 0.3 to 0.7.

That is, when C2/(C1+C2) is less than 0.3, the ratio of the second crystal grains 9b containing Ca is small, so the dielectric constant at room temperature becomes low. On the other hand, if When C2/(C1+C2) is more than 0.7, the dielectric constant at room temperature increases, but the lifetime in the high-temperature load test decreases.

C2/(C1+C2) is particularly preferably 0.4 to 0.6. If it is in this range, the dielectric constant of the dielectric ceramic at room temperature can be increased to 4,000 or more.

Further, the calcium concentration of the second crystal grains 9b is particularly preferably 0.5 to 2.5 atom%. If the calcium concentration is in this range, calcium can be sufficiently dissolved in barium titanate. Further, since the compound which is not solid-solved and remains in the grain boundary or the like is reduced, the AC voltage dependence of the dielectric constant is increased, so that a high dielectric constant can be achieved. Further, the first crystal grains 9a include those having a calcium concentration of zero. Further, the Curie temperature in the present invention means a temperature at which the dielectric constant is maximized in the range of the temperature characteristic (-60 to 150 ° C) at which the dielectric constant is measured.

Regarding the calcium concentration in the crystal grains 9, a cross-section electron microscope with an elemental analysis device is used to polish the cross section of the dielectric layer 5 by ion milling to the extent that it can be observed. The grain 9 was subjected to elemental analysis.

At this time, the spot size of the electron beam was set to 5 nm. Further, the analysis portion is set at a substantially equal interval from the grain boundary in the straight line drawn from the vicinity of the grain boundary of the crystal grain 9 to 4 to 5 points. The ratio of calcium when the total amount of Ba, Ti, Ca, V, Mg, RE (rare earth element) and Mn detected from each measurement point was 100% was determined and determined at each measurement point. The average of the calcium ratios is taken as the calcium concentration. Then, the obtained crystal grain having a calcium concentration of 0.2 atom% or less is used as the first crystal grain 9a, and the obtained calcium concentration is 0.4 atom% or more. The crystal grains serve as the second crystal grains 9b.

The crystal grain 9 of the calcium concentration was selected in the following manner. First, a photograph of a polished surface obtained by polishing a cross section of the dielectric layer 5 constituting the laminated ceramic capacitor (magnification: 20,000 to 100,000 times) was taken using a transmission electron microscope. Then, a circle enclosing 30 crystal grains 9 is drawn on the photograph, and the area of each particle is obtained by image processing according to the contour of each of the crystal grains 9 located in the circle and the circumference, and is calculated to be replaced with the same area. The diameter of the circle. Next, the diameter of the obtained crystal grain 9 is in the range of ±30% of the average particle diameter determined by the method described later.

Further, the total area of each of the first crystal grains 9a and the second crystal grains 9b selected and measured from the respective crystal grains 9 located in the circle and the circumference is obtained, and the value of C2/(C1+C2) is obtained. .

Further, the center of the crystal grain 9 is the center of the inscribed circle of the crystal grain 9, and the vicinity of the grain boundary of the crystal grain 9 means a region from the grain boundary of the crystal grain 9 to the inner side of 5 nm. Moreover, the inscribed circle of the die 9 takes the image reflected by the transmission electron microscope into the computer, draws an inscribed circle on the grain 9 on its screen, and determines the center of the die 9.

Fig. 3 is a view showing an X-ray diffraction pattern of a dielectric ceramic constituting the multilayer ceramic capacitor of the sample No. 3 in the embodiment to be described later. The dielectric ceramic constituting the multilayer ceramic capacitor of the present invention has a diffraction pattern as shown in the X-ray diffraction pattern of Fig. 3. 4 is a graph showing the temperature characteristics of the electrostatic capacitance of the multilayer ceramic capacitor of Sample No. 3. Multilayer ceramic capacitor device of the invention There is a temperature characteristic of the electrostatic capacitance as shown in FIG.

In the X-ray diffraction diagram of Fig. 3, the (200) plane of the cubic crystal barium titanate (near 2 θ = 45.3 °) and the (002) plane of the barium titanate exhibiting tetragonal (2 θ = 45.1 °) are shown. The nearby X-ray diffraction peaks overlap and become wide diffraction peaks. Further, the diffraction intensity (Ic) of the (200) plane showing the cubic crystal of barium titanate is larger than the diffraction intensity (It) of the (002) plane showing the tetragonal barium titanate. The crystal structure is similar to the X-ray diffraction pattern of the conventional core-shell structure, but as shown in FIG. 4, the dielectric ceramic (Tc) constituting the multilayer ceramic capacitor of the present invention has a Curie temperature (Tc) of 95 to 105 ° C. The dielectric properties of a dielectric ceramic having a core-shell structure with a Curie temperature of 125 ° C are different.

That is, a dielectric ceramic having a core-shell structure obtained by solid-solving an additive component such as magnesium, manganese, and a rare earth element in a barium titanate as a main component shows a Curie temperature of pure barium titanate (125 ° C) ) Curie temperature nearby. On the other hand, as described above, the dielectric ceramic constituting the dielectric layer 5 of the multilayer ceramic capacitor of the present invention is solid-dissolved with calcium, vanadium, magnesium, manganese, and ruthenium, osmium, iridium and the like in barium titanate. At least one rare earth element selected from the group and strontium. Therefore, although the diffraction intensity of the (200) plane having the cubic crystal of barium titanate in the X-ray diffraction pattern is larger than the crystal structure of the diffraction intensity of the (002) plane showing the tetragonal barium titanate, The temperature is 95 to 105 ° C and has a characteristic of being biased toward the room temperature side.

It is considered that the reason is that a small amount of cerium is solid-dissolved in addition to the added components such as vanadium, magnesium, manganese, and a rare earth element, whereby the additive component is diffused in a specific state inside the dielectric ceramic, so that Curie can be made. Temperature is 95~105 °C.

For example, in the dielectric ceramic constituting the multilayer ceramic capacitor of the present invention, the first crystal grains 9a and the second crystal grains 9b are obtained by subtracting the manganese concentration at a depth of 10 nm from the surface layer portion. The difference is 0.3 atom% or less, and the concentration of the rare earth element in the surface layer portion minus the concentration of the rare earth element at a position having a depth of 10 nm is 0.7 atom% or more. Specifically, it is as shown in FIGS. 5(a) to (c).

Fig. 5 (a) is a graph showing changes in concentration of rare earth elements and manganese contained in crystal grains of a dielectric ceramic constituting the multilayer ceramic capacitor of sample No. 3 in the example described later. The dielectric ceramic is within the scope of the invention.

Fig. 5 (b) is a graph showing changes in concentration of rare earth elements and manganese contained in crystal grains of a dielectric ceramic constituting the multilayer ceramic capacitor of sample No. 1 in the example described later. This dielectric ceramic has a core-shell structure in which a solid component of magnesium, manganese, and a rare earth element is dissolved in barium titanate as a main component, and has a Curie temperature of 125 °C.

Fig. 5 (c) is a graph showing changes in concentration of rare earth elements and manganese contained in crystal grains of a dielectric ceramic constituting the multilayer ceramic capacitor of sample No. 6 in the example described later. This dielectric ceramic is obtained by dissolving such an additive component of magnesium, manganese, and a rare earth element in barium titanate as a main component, and adding hydrazine in excess. Further, in FIGS. 5(a) to (c), the rare earth element is yttrium (Y).

In Fig. 5(a), the rare earth element (Y) shows a large concentration change in the vicinity of the surface of the crystal grain 9, whereas the concentration change of manganese (Mn) in the vicinity of the surface is small.

On the other hand, in FIG. 5(b), both the rare earth element (Y) and the manganese (Mn) component show a large concentration change in the vicinity of the surface of the crystal grain 9. In Fig. 5(c), the concentration changes of the rare earth element (Y) and the manganese (Mn) component in the vicinity of the surface of the crystal grain 9 are small.

As described above, the multilayer ceramic capacitor of the present invention has a large change in the concentration of the rare earth element (Y) in the vicinity of the surface of the crystal grain 9 constituting the dielectric ceramic, and the change in the concentration of manganese (Mn) is small. There is an intermediate structure between sample No. 1 and sample No. 6. Therefore, even if the crystal structure is similar to the core-shell structure, the Curie temperature is also 95 to 105 °C.

Therefore, in the multilayer ceramic capacitor of the present invention, the element of diffusion compensates for oxygen defects in the crystal grains, whereby the dielectric properties of the dielectric ceramic are improved, and the life in the high-temperature load test can be improved.

In other words, when the amount of solid solution of manganese and rare earth elements in the crystal grains 9 is small, the proportion of the core portion including defects such as a large number of oxygen vacancies increases. Therefore, it is considered that, in the case where a direct current voltage is applied, oxygen vacancies or the like easily become a carrier for carrying electric charges inside the crystal grains 9 constituting the dielectric ceramic, and the dielectric properties of the dielectric ceramic are lowered. Vanadium and yttrium are added to the dielectric ceramic constituting the dielectric layer 5 in the multilayer ceramic capacitor of the present invention, and the solid solution state of the manganese and the rare earth element including the additive component of the vanadium and niobium is different. The Curie temperature is in the range of 95 to 105 °C. Therefore, it is generally considered that the carrier density of the oxygen vacancies or the like in the crystal grains 9 can be reduced, and the rare earth element and manganese are contained more, and the oxygen vacancies inside the crystal grains 9 are less, so that a higher insulation can be obtained. Sex.

The measurement of the concentration of the rare earth element and manganese contained in the crystal grains 9 was carried out using a transmission electron microscope with an elemental analyzer (EDS). For the sample to be analyzed, the laminated ceramic capacitor was polished to a level at which observation was possible by ion milling in the lamination direction, and the surface of the ground dielectric layer 5 was selected and determined by the measurement of the calcium concentration. The first crystal grain 9a and the second crystal grain 9b.

For each of the selected crystal grains 9a and 9b, the area of each particle is obtained from the contour by image processing, and the diameter when replacing the circle having the same area is calculated, and the respective crystal grains 9a and 9b are set to be at The first crystal grains 9a and the second crystal grains 9b in the range are selected from the crystal grains in the range of ±30% of the average particle diameter by the measurement method described later.

The spot size of the electron beam when performing elemental analysis is set to 1 to 3 nm. Further, the analysis portion is at least a surface portion of the crystal grain 9 and a depth of 5 nm, 10 nm, and 20 nm from the surface portion. Further, in the present invention, the surface layer portion of the crystal grain 9 means a region within 3 nm from the grain boundary of the cross section of the crystal grain 9.

Then, the concentration of the rare earth element and the manganese in the surface layer portion of each of the crystal grains 9a and 9b is obtained for each of the first crystal grains 9a and the second crystal grains 9b, and a rare earth having a depth of 10 nm from the surface layer portion is obtained. The concentration of elements and manganese. In Figs. 5(a) to 5(c), the position indicated by the arrow is a position at a depth of 10 nm from the surface layer portion.

Next, the surface layer portions of the respective crystal grains 9a and 9b are obtained from the respective concentrations of the rare earth element and the manganese at a position where the depth of the surface layer portion and the surface layer portion of the respective crystal grains 9a and 9b are 10 nm. The difference in concentration between the concentration of manganese minus the concentration of manganese at a depth of 10 nm, and the concentration of rare earth elements in the surface layer of each of the grains 9a and 9b minus the concentration of rare earth elements at a position of 10 nm in depth . Specifically, this operation is performed for each of 10 pairs of crystal grains, and the average value of the crystal grains 9 is calculated for a total of 20 values obtained from the respective crystal grains 9a and 9b.

Further, although not shown, magnesium, vanadium and niobium are the same as manganese, and the concentration of each surface layer portion is reduced by a concentration at a position at a depth of 10 nm, and the difference in concentration is 0.3 atom% or less.

In the dielectric ceramic constituting the dielectric layer 5 in the multilayer ceramic capacitor of the present invention, the first crystal grain 9a and the second crystal are included in terms of maintaining high dielectric constant and reducing dielectric loss. The average particle diameter of the crystal grains 9 of the particles 9b may be 0.1 μm or more, and if the capacitance is not uniform, it may be 0.3 μm or less, preferably 0.14 to 0.28 μm.

If the average grain size of the crystal grains 9 is 0.14 to 0.28 μm, the dielectric constant is 3500 or more, the dielectric loss is 12.5% or less, the dielectric constant temperature characteristic satisfies X6S, and the AC voltage is set. The dielectric constant at 1 V is 1.9 times or less of the dielectric constant when the AC voltage is set to 0.01 V, and satisfies the reliability in the high-temperature load test (at 105 ° C, 1.5 times the rated voltage, and 1000 hours or more). No defects under the conditions).

For the average particle diameter of the crystal grains 9, first, the fracture surface of the sample composed of the calcined capacitor body 1 was ground, and then a photograph of the internal structure (magnification: 20,000 to 100,000 times) was taken using a scanning electron microscope.

Then, a circle enclosing 20 to 30 crystal grains 9 is drawn on the photograph, and the crystal grains 9 in the circle and on the circumference are selected. Next, the contour of each of the crystal grains 9 was subjected to image processing, and the area of each particle was determined, and the diameter when the circle having the same area was replaced was calculated, and the average particle diameter was obtained from the average value.

On the other hand, in order to obtain a multilayer ceramic capacitor which can further improve the life characteristics in the high-temperature load test, as another preferable composition of the dielectric ceramic, it is preferable to contain 100 mol of the titanium constituting the barium titanate. The V ₂ O ₅ conversion is 0.05 to 0.1 m of vanadium, and is 0.2 to 0.8 m of magnesium in terms of MgO, 0.2 to 0.3 mol of manganese in terms of MnO, and 0.4 in terms of RE ₂ O ₃ . ~0.6 moles of at least one rare earth element selected from lanthanum, cerium, lanthanum and cerium, and 0.05 to 0.1 moles in terms of Tb ₄ O ₇ , and preferably first grain and second The average grain size of the crystal grains is from 0.14 to 0.19 μm.

A dielectric ceramic having such a composition and an average particle diameter of the crystal grains can obtain a laminated ceramic capacitor which is not defective even if the temperature of the high-temperature load test is raised to 125 ° C for 1,000 hours or more.

Further, in the dielectric ceramic of the present invention, a glass component may be contained as an auxiliary agent (sintering aid) for improving the sinterability as long as the range of the desired dielectric properties can be maintained.

Next, a method of manufacturing the multilayer ceramic capacitor of the present invention will be described. First, as the raw material powder, barium titanate powder (hereinafter referred to as BT powder) having a purity of 99% or more and a powder in which calcium is dissolved in barium titanate (hereinafter referred to as BCT powder) are prepared. Further, the V ₂ O ₅ powder and the MgO powder are prepared, and further, an oxide powder of at least one rare earth element selected from the group consisting of Y ₂ O ₃ powder, Dy ₂ O ₃ powder, Ho ₂ O ₃ powder, and Er ₂ O ₃ powder is prepared. And Tb ₄ O ₇ powder and MnCO ₃ powder.

The BCT powder is a solid solution in which a part of the A site is calcium (Ca)-substituted barium titanate as a main component, and is represented by (Ba _1-x Ca _x )TiO ₃ . In the compound, the substitution amount of Ca in the A site is preferably X = 0.01 to 0.2. When the substitution amount of Ca is within this range, a crystal structure in which grain growth is suppressed can be formed by the coexistence structure with the first crystal grains 9a. Thereby, in the case where the obtained dielectric ceramic is used as a laminated ceramic capacitor, excellent temperature characteristics of the electrostatic capacitance can be obtained in the use temperature range. Further, Ca contained in the second crystal grains 9b is solid-dissolved in a state of being dispersed in the second crystal grains 9b.

Further, the specific surface area of the BT powder and the BCT powder to be used is preferably 2 to 6 m ² /g. When the specific surface area of the BT powder and the BCT powder is 2 to 6 m ² /g, the first crystal grains 9a and the second crystal grains 9b are easily maintained in a crystal structure similar to the core-shell structure, and the added components are easily dissolved. The Curie temperature is biased toward the low temperature side in the crystal grains. In addition, an increase in the dielectric constant can be achieved, and the insulation of the dielectric ceramic can be improved, whereby the reliability in the high-temperature load test can be improved.

Further, as an additive, an oxide powder of at least one rare earth element selected from Y ₂ O ₃ powder, Dy ₂ O ₃ powder, Ho ₂ O ₃ powder, and Er ₂ O ₃ powder, Tb ₄ O ₇ powder, V _{The 2} O ₅ powder, the MgO powder, and the MnCO ₃ powder are preferably the same in particle size (or specific surface area) as the dielectric powder.

Then, relative to the total amount of BT powder and BCT powder of 100 moles, 0.02 to 0.2 moles of V ₂ O ₅ powder, 0.2 to 0.8 moles of MgO powder, 0.3 to 0.8 moles of rare earth element oxide powder And 0.1 to 0.5 mol of MnCO ₃ powder and 0.02 to 0.2 mol of Tb ₄ O ₇ powder to prepare the raw material powders, and further, as needed, to be added as a sintering aid in a range capable of maintaining desired dielectric properties. A glass powder of the agent to obtain a raw material powder. When the total amount of the BT powder and the BCT powder as the main raw material powder is 100 parts by mass, the amount of the glass powder added is preferably 0.5 to 2 parts by mass.

Next, a ceramic slurry is prepared by adding a dedicated organic vehicle to the raw material powder, and a ceramic green sheet is formed by a sheet forming method such as a doctor blade method or a slit extrusion coating method. In this case, the thickness of the ceramic green sheet is preferably 0.5 to 3 μm in terms of thinning and high insulation for achieving high capacitance of the dielectric layer 5.

Thereafter, a rectangular internal electrode pattern was printed on the main surface of the obtained ceramic green sheet. The conductive paste to be the internal electrode pattern is preferably an alloy powder of Ni, Cu or the like.

Then, the desired number of ceramic green sheets in which the internal electrode patterns are formed are overlapped, and the upper and lower layers are in the same number of sheets. The ceramic green sheets of the electrode patterns form a sheet laminate. In this case, the internal electrode patterns in the sheet laminate are shifted by half a pattern in the longitudinal direction.

Next, the obtained sheet laminated body was cut into a lattice shape, and the capacitor main body molded body was formed so that the end part of the internal electrode pattern was exposed. According to such a lamination method, the internal electrode pattern can be formed so that the end faces of the capacitor body molded body after the cutting are alternately exposed.

Then, the obtained capacitor body formed body was degreased and then calcined. The calcination temperature is preferably from 1100 to 1200 ° C for the purpose of controlling the solid solution of the additive in the BT powder and the BCT powder and the growth of the crystal grains of the crystal grains.

In order to obtain the dielectric ceramic of the present invention, BT powder and BCT powder having a specific surface area of 2 to 6 m ² /g are used, and in each case, a predetermined amount of each of oxides of magnesium, manganese, vanadium and niobium is added as described above. And each of the oxide powders of at least one of the above-mentioned rare earth elements selected from lanthanum, cerium, lanthanum and cerium is used as an additive and calcined at the above temperature. Thereby, the crystal grains obtained by using the BT powder and the BCT powder as main raw materials contain various additives, and the crystal structure exhibited by the crystal grains is a structure similar to the core-shell structure, and the Curie temperature is lower than the conventional one. The range of the Curie temperature of the dielectric ceramic showing the core-shell structure. After calcination, the first crystal grains 9a and the second crystal grains 9b are added by calcining so that the Curie temperature is lower than the range of the Curie temperature of the dielectric ceramics of the conventional display core-shell structure. The solid solution is improved, and as a result, a dielectric ceramic having high insulation and good life in a high-temperature load test can be obtained. Further, in the present invention, in order to make the average particle diameter of the crystal grains 9 constituting the dielectric ceramic to be 0.19 μm or less, it is preferable to select a powder having a specific surface area of more than 5 m ² /g.

Further, after calcination, heat treatment was again performed in a weakly reducing atmosphere. This heat treatment is carried out in order to reoxidize the reduced dielectric ceramic during calcination in a reducing environment, and to restore the insulation resistance which is reduced by reduction during calcination. The temperature of the heat treatment is preferably 900 to 1100 ° C for the purpose of suppressing further grain growth of the first crystal grains 9 a and the second crystal grains 9 b and increasing the amount of reoxidation. In the above manner, a multilayer ceramic capacitor in which the first crystal grains 9a and the second crystal grains 9b are highly insulating and exhibits a Curie temperature of 95 to 105 ° C can be produced.

Then, an external electrode paste is applied to the opposite end portions of the capacitor body 1 obtained by the above heat treatment, and fired to form the external electrode 3. Further, a plating film may be formed on the surface of the external electrode 3 to improve mountability. The multilayer ceramic capacitor of the present invention can be obtained in the above manner.

Hereinafter, the present invention will be further described by way of examples, but the present invention is not limited to the following examples.

[Examples] <Production of laminated ceramic capacitors>

First, as a raw material powder, BT powder, BCT powder (composition of (Ba _1-x Ca _x )TiO ₃ , X = 0.05), MgO powder, Y ₂ O ₃ powder, Dy ₂ O ₃ powder, Ho ₂ O _{3 were prepared.} Powder, Er ₂ O ₃ powder, Tb ₄ O ₇ powder, MnCO ₃ powder, and V ₂ O ₅ powder.

Then, the various powders were mixed at a ratio shown in Tables 1 to 3. In Tables 1 to 3, the blending ratios of the two powders are shown for the BT powder and the BCT powder. Further, the ratio of MgO powder, Y ₂ O ₃ powder, Dy ₂ O ₃ powder, Ho ₂ O ₃ powder, Er ₂ O ₃ powder, Tb ₄ O ₇ powder, MnCO ₃ powder, and V ₂ O ₅ powder is BT powder. The ratio with the total amount of BCT powder is set to 100 mol.

The purity of the raw material powders was 99.9%. The BT powder and the BCT powder were used in Sample Nos. 1 to 80 in which the specific surface area was 4 m ² /g, and in Sample Nos. 81 to 110, the specific surface area was 6 m ² /g. MgO powder, Y ₂ O ₃ powder, Dy ₂ O ₃ powder, Ho ₂ O ₃ powder, Er ₂ O ₃ powder, Tb ₄ O ₇ powder, MnCO ₃ powder, and V ₂ O ₅ powder have an average particle diameter of 0.1 μm. By. As the sintering aid, a glass powder having a composition of SiO ₂ = 55, BaO = 20, CaO = 15, and Li ₂ O = 10 (mole %) was used. The amount of the glass powder added is 1 part by mass based on 100 parts by mass of the total of the BT powder and the BCT powder.

Next, a mixed solvent of toluene and ethanol as a solvent was added using a zirconia ball having a diameter of 5 mm, and the raw material powders were wet-mixed.

Then, the wet-mixed powder was placed together with a polyvinyl butyral resin in a mixed solvent of toluene and ethanol, and wet-mixed using a zirconia ball having a diameter of 5 mm to prepare a ceramic slurry. Using this ceramic slurry, ceramic green sheets having a thickness of 1.5 μm and 2.5 μm were produced by doctor blade forming.

Next, on the upper surface of the ceramic green sheets having thicknesses of 1.5 μm and 2.5 μm, a plurality of rectangular internal electrode patterns having Ni as a main component were formed. The conductive paste for forming the internal electrode pattern was used by adding 15 parts by mass of BT powder to 100 parts by mass of Ni powder having an average particle diameter of 0.3 μm.

Then, 200 pieces of ceramic green sheets printed with internal electrode patterns were laminated, and 20 pieces of ceramic green sheets having unprinted internal electrode patterns were laminated on the upper and lower surfaces thereof, using a press at a temperature of 60 ° C and a pressure of 10 ⁷ Pa. After the time was 10 minutes, the sheets were laminated, and a sheet laminate using a ceramic green sheet having a thickness of 1.5 μm and a sheet laminate using a ceramic green sheet having a thickness of 2.5 μm were produced. Thereafter, each of the sheet laminates is cut into a predetermined size to form a capacitor body molded body.

Next, the capacitor body molded body was subjected to a debonding treatment in the air, and then calcined at 1,120 to 1,135 ° C for 2 hours in a hydrogen gas to nitrogen gas to prepare a capacitor body. Further, the produced capacitor system was further subjected to reoxidation treatment at 1000 ° C for 4 hours in a nitrogen atmosphere. The size of the capacitor body is 0.95 x 0.48 x 0.48 mm ³ , the thickness of the dielectric layer is 1 μm or 2 μm, and the effective area of the inner electrode layer of one layer is 0.3 mm ² . In addition, the effective area means an area of a portion where the internal electrode layers alternately formed in the lamination direction so as to be exposed on different end faces of the capacitor body, respectively.

Thereafter, the calcined capacitor body was subjected to barrel polishing, and then an external electrode paste containing Cu powder and glass was applied to both end portions of the capacitor body, and fired at 850 ° C to form an external electrode. Thereafter, Ni plating and tin plating (Sn) are sequentially performed on the surface of the external electrode using an electrolytic roller machine. Laminated ceramic capacitors (sample No. 1 to 110 in Tables 1 to 3).

<evaluation>

Then, the obtained multilayer ceramic capacitor was subjected to the following evaluation.

(dielectric constant and dielectric loss)

For the dielectric constant and dielectric loss, the electrostatic capacitance is measured at a temperature of 25 ° C and a frequency of 1.0 kHz, and the measurement voltage is set to 0.01 Vrms or 1 Vrms, and the thickness of the dielectric layer and the internal electrode layer are determined. The effective area is determined. The evaluation of the dielectric constant and the dielectric loss was carried out by setting the number of samples to 20 and calculating the average value. Further, in the evaluation of the dielectric constant, the standard deviation σ is obtained, and the coefficient of variation (σ/x) is obtained from the average value x.

(temperature characteristic of dielectric constant)

The temperature characteristic of the dielectric constant is measured by measuring the electrostatic capacitance in the range of -55 to 150 °C. When the temperature characteristic of the dielectric constant satisfies X6S (in the range of -55 to 105 ° C and within ±22% on the basis of 25 ° C), it is evaluated as ○, and the case where it is not satisfied is evaluated as ×. The evaluation of the temperature characteristics of the dielectric constant was carried out by setting the number of samples to 10 and calculating the average value.

(Curie temperature)

The Curie temperature is obtained as the temperature at which the dielectric constant reaches the maximum in the range in which the temperature characteristics of the dielectric constant are measured.

(High temperature load test)

The high temperature load test was carried out at a temperature of 105 ° C or 125 ° C and an applied voltage of 6 V / μm for 1000 hours. Number of samples in high temperature load test Twenty samples were used for each sample, and those that did not deteriorate until 1000 hours were evaluated as good. Further, regarding the above temperature, samples No. 1 to 80 were carried out at 105 ° C, and sample Nos. 81 to 110 were carried out at 125 ° C.

(The average particle size)

The average particle diameter of the crystal grains constituting the dielectric layer was determined as follows. First, the fracture surface of the sample as the capacitor body after calcination was ground, and then a photograph of the internal structure (magnification: 30,000 times) was taken using a scanning electron microscope. Then, draw a circle surrounded by 20 to 30 crystal grains on the photo, and select the crystal grains in the circle and on the circumference. Next, the contour of each crystal grain was subjected to image processing to determine the area of each particle, and the diameter when the circle having the same area was replaced was calculated, and the average particle diameter was obtained from the average value.

Further, the above-mentioned polishing was carried out by first rough grinding the fracture surface using a diamond plate, and then grinding it using #1000 sandpaper. Then, grinding was carried out using a diamond liquid coated on a hard polishing wheel, and alumina abrasive grains having a particle diameter of 0.3 μm were applied to a soft polishing wheel to perform finish polishing.

(calcium concentration. C2/(C1+C2))

Regarding the calcium concentration in the crystal grains, the cross section of the dielectric layer constituting the laminated ceramic capacitor is polished to a level that can be observed by ion milling using a transmission electron microscope with an elemental analysis device. The crystal grains present on the upper surface were obtained by elemental analysis.

At this time, the spot size of the electron beam was set to 5 nm. Analysis site is based on The straight line drawn toward the center near the grain boundary of the crystal grain is set at 4 to 5 points at substantially equal intervals from the grain boundary. Then, the ratio of calcium when the total amount of Ba, Ti, Ca, V, Mg, RE (rare earth element) and Mn detected from each measurement point is 100% is obtained, and the ratio obtained from each measurement point is obtained. The average of the calcium ratios is taken as the calcium concentration.

The crystallites for determining the calcium concentration were selected in the following manner. First, a photograph of a polished surface obtained by polishing a cross section of a dielectric layer constituting a laminated ceramic capacitor was taken using a transmission electron microscope. Then, a circle enclosing 20 to 30 crystal grains is drawn on the photo, and the area of each particle is obtained by image processing according to the contours of the respective crystal grains located in the circle and the circumference, and is calculated to be replaced with the same area. The diameter of the circle. Next, the crystal grain is in the range of ±30% of the above average particle diameter as the crystal grains.

Further, the total area of each of the first crystal grains and the second crystal grains selected and measured from the respective crystal grains located in the circle and the circumference was determined, and the value of C2/(C1+C2) was calculated.

Further, as described above, the center of the crystal grain is the center of the inscribed circle of the crystal grain, and the vicinity of the grain boundary of the crystal grain means a region from the grain boundary of the crystal grain to the inner side of 5 nm. Moreover, the inscribed circle of the die takes the image reflected by the transmission electron microscope into the computer, draws an inscribed circle on the grain on the screen, and determines the center of the die.

(X-ray diffraction: XRD)

Shows the diffraction intensity of the (200) plane of cubic titanate, and shows the square The ratio of the diffraction intensity of the (002) plane of the strontium titanate is measured by using an X-ray diffraction apparatus having a Cuk-α tube, measured at an angle of 2 θ=44 to 46°, according to the peak The ratio of the strength is obtained.

(difference in concentration of rare earth elements and manganese)

The measurement of the concentration of the rare earth element and manganese contained in the crystal grains was carried out using a transmission electron microscope attached with an elemental analyzer (EDS). For the sample to be analyzed, the multilayer ceramic capacitor was polished to a level that can be observed by ion milling in the lamination direction, and the surface of the ground dielectric layer was determined by the measurement of the calcium concentration. The first crystal grain and the second crystal grain.

For the selected first crystal grain and the second crystal grain, the area of each particle is obtained from the contour by image processing, and the diameter when replacing the circle having the same area is calculated, and each crystal grain is set to be borrowed. The crystal grains in the range of ±30% of the average particle diameter obtained by the above measurement method. Ten first crystal grains and second crystal grains in the range are selected.

The spot size of the electron beam when performing elemental analysis is set to 1 to 3 nm. Further, the analysis portion is a surface portion of the crystal grain (a region within 3 nm from the grain boundary of the crystal grain profile) and a depth of 10 nm from the surface layer portion.

Then, the concentration of the rare earth element and manganese in the surface layer portion of each of the first and second crystal grains was determined by the above method, and the concentration of the rare earth element and manganese at a position having a depth of 10 nm from the surface layer portion was determined.

According to the rare earth elements of each of the first and second crystal grains obtained in the above manner, The concentration of manganese is determined by determining the concentration of manganese in the surface layer of each crystal grain minus the concentration of manganese at a depth of 10 nm, and the concentration of rare earth elements in the surface layer of each crystal grain minus 10 nm. The concentration difference of the rare earth element concentration at the position. Specifically, this operation is performed for each of 10 pairs of crystal grains, and the average value of the crystal grains is calculated for a total of 20 values obtained from the respective crystal grains.

Further, in the samples shown in Tables 1, 2, 4, 5 and 7 to 10, the rare earth element and manganese (Mn) contained in the crystal grains of the dielectric ceramic constituting the laminated ceramic capacitor of the sample of the present invention. The change in concentration showed the same tendency as sample No. 3.

(composition analysis)

The composition analysis of the sample of the obtained sintered body was carried out by inductively coupled plasma (ICP) analysis or atomic absorption analysis. In this case, the obtained dielectric ceramics were mixed with boric acid and sodium carbonate and melted, and dissolved in hydrochloric acid. First, qualitative analysis of the elements contained in the dielectric ceramics was carried out by atomic absorption analysis. Then, for each specific element, the standard solution was diluted as a standard sample, and quantified by ICP emission spectrometry. Further, the amount of oxygen is determined by setting the valence of each element to the valence shown in the periodic table.

The composition and calcination temperature are shown in Tables 1 to 3, respectively. The composition of each element in the sintered body in terms of oxide is shown in Tables 4 to 6, and the thickness of the dielectric layer after calcination and the crystal grains are Ratio (C2/(C1+C2)), average particle size, Density and characteristics of rare earth elements and manganese at a position where the intensity ratio of the cubic crystal and the tetragonal crystal is measured by X-ray diffraction, the Curie temperature, the surface portion of the crystal grain, and the depth of the surface layer portion are 10 nm (dielectric The results of the constant, dielectric loss, dielectric constant (determined from the temperature characteristics of the electrostatic capacitance) and the lifetime in the high-temperature load test are shown in Tables 7 to 12.

According to the results of Tables 1 to 12, samples No. 2 to 5, 8 to 13, 16 to 19, 22 to 25, 28 to 31, 33 to 35, 37 to 39, 41 to 80, and 82 of the present invention can be clarified. 83, 86~88, 91~94, 97, 100, 101, 103~105 and 107~109 have a dielectric constant of 3500 or more at room temperature (25 °C), a dielectric loss of 12.5% or less, and a dielectric constant. The temperature characteristic satisfies X6S, and the dielectric constant when the AC voltage is 1 V is twice or less the dielectric constant when the AC voltage is 0.01 V, and further, there is no defect in the high-temperature load test.

Further, the area ratio of the first crystal grains composed of crystal grains having a calcium concentration of 0.2 atom% or less and the second crystal grains composed of crystal grains having a calcium concentration of 0.4 atom% or more are set to C2/(C1+C2). Sample No. 38, 39, 42, 43, 45, 46, 48, 49, 51, 52, 54, 55, 57-67, 69, 70, 72, 73, 75, 76, 78~ from 0.4 to 0.6 The dielectric constants of room temperature (25 ° C) of 80, 108 and 109 are 4000 or more.

In addition, as a composition of the dielectric ceramic constituting the dielectric layer, the vanadium is set to 0.02 to 0.08 mol in terms of V ₂ O ₅ with respect to 100 mol of titanium constituting barium titanate, and magnesium is set. It is 0.3 to 0.6 m in terms of MgO, and 0.2 to 0.4 m in terms of MnO, and at least one rare earth element selected from lanthanum, cerium, lanthanum and cerium is set to RE ₂ O _{3 .} The conversion is 0.4 to 0.6 m, and the 鋱 is set to 0.02 to 0.08 mol in terms of Tb ₄ O ₇ . No. 50 to 80. The dielectric constant when the AC voltage is 1 V is AC. The voltage is set to be less than 1.5 times the dielectric constant at 0.01 V.

In addition, the average particle diameter of the crystal grains constituting the dielectric layer is set to 0.14 to 0.28. Samples No. 2~5, 8~12, 16~19, 22~25, 28~31, 33~35, 37~39, 41~77, 79, 80, 82, 83, 86~88 in the range of μm The dielectric constants of 91~94, 97, 100, 101, 103~105 and 107~109 are more than 3500, the dielectric loss is below 12.5%, the dielectric constant of the dielectric constant satisfies X6S, and the AC voltage is set to 1 V. The dielectric constant at this time is 1.9 times or less of the dielectric constant when the AC voltage is set to 0.01 V.

Further, as a composition of the dielectric ceramic constituting the dielectric layer, 鋱 is a sample No. 2, 53-67, 71-80, and 82-series in the range of 0.05 to 0.08 mol in terms of Tb ₄ O ₇ . The coefficient of variation of the electric constant is 0.9 or less, and the unevenness is small.

Further, as is clear from Fig. 5(a), in the first crystal grain and the second crystal grain of the dielectric layer in the multilayer ceramic capacitor of the sample No. 3, the manganese (Mn) concentration in the surface layer portion is subtracted from the depth. The concentration difference of manganese (Mn) at a position of 10 nm is 0.3 atom% or less, and the concentration of the rare earth element (Y) in the surface layer is subtracted from the concentration of the rare earth element (Y) at a depth of 10 nm. The difference is 0.7 atom% or more. In addition, other samples of the present invention (sample No. 2, 4, 5, 8 to 13, 16 to 19, 22 to 25, 28 to 31, 33 to 35, 37 to 39, 41 to 80, 82, 83, 86~88, 91~94, 97, 100, 101, 103~105, and 107~109) also have the following concentration difference similarly to sample No. 3: manganese (Mn) concentration in the surface layer minus 10 nm The concentration difference of the manganese (Mn) concentration at the position is 0.3 atom% or less, and the concentration of the rare earth element in the surface layer portion minus the concentration of the rare earth element at a position having a depth of 10 nm is 0.7 atom% or more.

In addition, as a composition of the dielectric ceramic constituting the dielectric layer, the vanadium is set to 0.05 to 0.1 m in terms of V ₂ O ₅ with respect to 100 mol of titanium constituting barium titanate, and magnesium is set to In terms of MgO, it is 0.2 to 0.8 m, and manganese is 0.2 to 0.3 m in terms of MnO, and at least one rare earth element selected from lanthanum, cerium, lanthanum and cerium is set to RE ₂ O _{3 .} The conversion is 0.4 to 0.6 m, and the enthalpy is set to 0.05 to 0.1 m in terms of Tb ₄ O ₇ , and the average grain size of the first crystal grain and the second crystal grain is set to 0.14 to 0.19 μm. Sample Nos. 82, 83, 86 to 88, 91 to 94, 97, 100, 101, 103 to 105, and 107 to 109, which were set to a temperature of 125 ° C and a voltage of 6 V in a high temperature load test. The lower ones are not bad for more than 1000 hours.

In contrast, samples No. 1, 6, 7, 14, 15, 20, 21, 26, 27, 32, 36, 40, 81, 84, 85, 89, 90, 95, 96 outside the scope of the present invention , 98, 99, 102, 106, and 110 do not satisfy any of the following characteristics: a dielectric constant of 3500 or more at room temperature (25 ° C), a dielectric loss of 12.5% or less, and a temperature characteristic of the dielectric constant satisfying X6S, When the AC voltage is set to 1 V, the dielectric constant is twice or less the dielectric constant when the AC voltage is set to 0.01 V, and the lifetime in the high-temperature load test.

In addition, the concentration of manganese and rare earth element (Y) of sample No. 1 in which the crystal structure is a core-shell structure and the dielectric ceramic having a Curie temperature of 125 ° C is used as the dielectric layer is observed. (b) It can be seen that the concentration of manganese in the surface layer minus the concentration of manganese at a depth of 10 nm is 0.5 atom%, and the concentration of the rare earth element (Y) in the surface portion is reduced to a depth of 10 nm. The concentration difference of the rare earth element (Y) concentration was 0.8 atom%.

Further, when the concentration of the manganese and the rare earth element (Y) of the sample No. 6 in which the cubic crystal wave peak intensity is less than the tetragonal peak intensity and the Curie temperature is 91 ° C is observed, it is understood from Fig. 5 (c) that the surface layer portion is The difference in concentration between the concentration of manganese minus the concentration of manganese at a depth of 10 nm, and the concentration of rare earth element (Y) in the surface layer minus the concentration of rare earth element (Y) at a depth of 10 nm Less than 0.2 atom%.

Further, in the crystal grains constituting the dielectric layer of the produced multilayer ceramic capacitor, the calcium concentration of the second crystal grains is 0.5 to 1.5 atom% in the analysis range.

1‧‧‧ capacitor body

3‧‧‧External electrode

5‧‧‧ dielectric layer

7‧‧‧Internal electrode layer

9‧‧‧ grain

9a‧‧‧1st grain

9b‧‧‧2nd grain

11‧‧‧ grain boundary phase

Fig. 1 is a schematic cross-sectional view showing an example of a multilayer ceramic capacitor of the present invention.

Fig. 2 is an enlarged view showing a dielectric layer constituting the multilayer ceramic capacitor shown in Fig. 1, and is a view showing a crystal grain and a grain boundary phase.

Figure 3 is an X-ray diffraction pattern of sample No. 3 in the examples.

Fig. 4 is a graph showing the temperature characteristics of the electrostatic capacitance of the sample No. 3 in the examples.

Fig. 5 (a) is a graph showing changes in the concentration of rare earth elements and manganese contained in crystal grains of a dielectric ceramic constituting the multilayer ceramic capacitor of sample No. 3 of the example, and Fig. 5 (b) shows the composition. A graph showing changes in the concentration of rare earth elements and manganese contained in the crystal grains of the dielectric ceramic of the multilayer ceramic capacitor of the sample No. 1 in the example, and FIG. 5(c) shows the sample No. 6 constituting the example. A graph showing the change in concentration of rare earth elements and manganese contained in the crystal grains of the dielectric ceramic of the multilayer ceramic capacitor.

1‧‧‧ capacitor body

3‧‧‧External electrode

5‧‧‧ dielectric layer

7‧‧‧Internal electrode layer

Claims (6)

A multilayer ceramic capacitor formed by alternately laminating a dielectric layer and a internal electrode layer, wherein the dielectric layer contains barium titanate as a main component and contains calcium, magnesium, vanadium, manganese, lanthanum, and a dielectric ceramic of at least one rare earth element selected from the group consisting of lanthanum, cerium, lanthanum and cerium, wherein the above-mentioned multilayer ceramic capacitor is characterized in that the dielectric ceramic is 100 mils relative to the titanium strontium titanate. The above-mentioned vanadium containing 0.02 to 0.2 mol of V ₂ O ₅ in terms of MgO, 0.2 to 0.8 mol of the above-mentioned magnesium in terms of MgO, and 0.1 to 0.5 mol of the above-mentioned manganese in terms of MnO, The RE ₂ O ₃ conversion is at least one of the above-mentioned rare earth elements selected from the group consisting of ruthenium, osmium, iridium and osmium in an amount of from 0.3 to 0.8 mol, and the above-mentioned ruthenium of from 0.02 to 0.2 mol in terms of Tb ₄ O ₇ ; The crystal system constituting the dielectric ceramic has a first crystal group composed of the first crystal grains having the barium titanate as a main component and the calcium concentration of 0.2 atom% or less; a group of 2 crystals obtained by using the above barium titanate as a main component, and the concentration of the above calcium is 0 a second crystal grain of 4 atom% or more; the area of the first crystal grain observed on the polished surface of the dielectric ceramic is C1, and the area of the second crystal grain is C2 When C2/(C1+C2) is 0.3~0.7; in the X-ray diffraction diagram of the above dielectric ceramic, it is shown that the diffraction intensity of the (200) plane of the cubic crystal of barium titanate is larger than that of the square crystal The diffraction intensity of the (002) plane of barium titanate, and the Curie temperature is 95 to 105 °C. The multilayer ceramic capacitor according to the first aspect of the invention, wherein the first crystal grain and the second crystal grain have an average particle diameter of 0.14 to 0.28 μm. The multilayer ceramic capacitor of the first aspect of the patent application, wherein the C2/(C1+C2) is 0.4 to 0.6. The multilayer ceramic capacitor according to the first or third aspect of the invention, wherein the dielectric ceramic includes: 0.02 to 0.08 in terms of V ₂ O ₅ with respect to 100 mol of titanium constituting the barium titanate. The vanadium of the moir is 0.3 to 0.6 m of the above-mentioned magnesium in terms of MgO, and the above-mentioned manganese is 0.2 to 0.4 mol in terms of MnO, and is 0.4 to 0.6 m in terms of RE ₂ O ₃ . At least one of the above-mentioned rare earth elements selected from the group consisting of ruthenium, osmium and iridium, and the above-mentioned ruthenium in an amount of from 0.02 to 0.08 mol in terms of Tb ₄ O ₇ . The multilayer ceramic capacitor according to the first aspect of the invention, wherein the dielectric ceramic is contained in an amount of 0.05 to 0.08 m in terms of Tb ₄ O ₇ with respect to 100 mol of titanium constituting the barium titanate. The above 鋱. The multilayer ceramic capacitor according to the first aspect of the invention, wherein the dielectric ceramic comprises: 0.05 to 0.1 m in terms of V ₂ O ₅ with respect to 100 mol of titanium constituting the barium titanate. The vanadium is 0.2 to 0.8 m of the above-mentioned magnesium in terms of MgO, and the manganese is 0.2 to 0.3 mol in terms of MnO, and is 0.4 to 0.6 m in terms of RE ₂ O ₃ . And at least one of the rare earth elements selected from the group consisting of ruthenium and osmium, and the ruthenium of 0.05 to 0.1 mol in terms of Tb ₄ O ₇ ; and the average grain size of the first crystal grain and the second crystal grain are 0.14~0.19 μm.