CN102959655B

CN102959655B - Capacitor

Info

Publication number: CN102959655B
Application number: CN201180029005.1A
Authority: CN
Inventors: 名古屋雅昭; 东勇介; 稻山伸悟; 山崎洋一
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2010-06-25
Filing date: 2011-06-24
Publication date: 2016-04-06
Anticipated expiration: 2031-06-24
Also published as: JP5496331B2; JPWO2011162371A1; CN102959655A; WO2011162371A1

Abstract

The invention provides the X5R characteristic that meets EIA standard and dielectric constant is high, the AC biasing characteristic of relative dielectric constant and the little laminated ceramic capacitor of dielectric loss.Dielectric layer 5 is made up of dielectric-porcelain, above-mentioned dielectric-porcelain is made up of crystal grain 9, above-mentioned crystal grain 9 is using barium titanate as principal component and the shell portion 9b that to have crystal structure be tetragonal core 9a and crystal structure is cubic system, wherein, the thickness of above-mentioned shell portion 9b is 11.8 ~ 26.5nm, and the average grain diameter of above-mentioned crystal grain 9 is 0.15 ~ 0.35 μm.

Description

Capacitor

Technical field

The present invention relates to the crystal grain that comprises using barium titanate as principal component and can be thin layer capacitor.

Background technology

All the time, in the dielectric substance of laminated ceramic capacitor, the cause high due to relative dielectric constant and use barium titanate, in addition, in the interior electrode layer of laminated ceramic capacitor, uses cheap base metal (Ni etc.).When by when burning till using barium titanate as the dielectric layer of principal component and interior electrode layer simultaneously, need to not make Ni be oxidized to reduce partial pressure of oxygen (being such as below 0.03Pa at 1300 DEG C), but there is following problem in this case, namely dielectric layer is reduced and insulating properties reduction, can not get practical characteristic.

Therefore, such as, when meeting the laminated ceramic capacitor of X5R characteristic (or JIS standard B characteristic) of EIA standard, as dielectric substance, use such as using barium titanate as principal component and with the addition of wherein the oxide of rare earth element and Mn, V, Cr, Mo, Fe, Ni, Cu, Co etc. by principal mode, donor-type element compound, the dielectric-porcelain (such as with reference to patent documentation 1) of reducing resistance.Make so multiple adding ingredients be solid-solution in barium titanate and the crystal grain obtained to have by crystal structure be that tetragonal core (is generally pure BaTiO ₃) and surround the core shell structure that core and solid solution have the shell portion of adding ingredient to form.

In addition, as the dielectric-porcelain of X5R characteristic meeting EIA standard, the crystal grain proposed using barium titanate as principal component has core shell structure and in barium titanate, adds the dielectric-porcelain (such as with reference to patent documentation 2) of the rare earth elements such as vanadium, magnesium, yttrium and manganese.

Prior art document

Patent documentation

Patent documentation 1: Japanese Unexamined Patent Publication 2001-230150 publication

Patent documentation 2: Japanese Unexamined Patent Publication 2008-239407 publication

Summary of the invention

Invent problem to be solved

And, in recent years, the miniaturization of the electronic equipments such as mobile phone and the densification of installation just constantly advance, for the laminated ceramic capacitor used in so small-sized electronic equipment, also be required to meet the X5R characteristic of EIA standard, and require further high capacity.

Therefore, the object of the present invention is to provide the X5R characteristic meeting EIA standard and the high capacitor of dielectric constant.

For the scheme of dealing with problems

Capacitor of the present invention, it is characterized in that, dielectric layer is made up of dielectric-porcelain, above-mentioned dielectric-porcelain comprises crystal grain, above-mentioned crystal grain is using barium titanate as principal component and the shell portion that to have crystal structure be tetragonal core and crystal structure is cubic system, wherein, the thickness in above-mentioned shell portion is 11.8 ~ 26.5nm, and the average grain diameter of above-mentioned crystal grain is 0.15 ~ 0.35 μm.

In addition, in capacitor of the present invention, preferred above-mentioned dielectric-porcelain is made up of following dielectric-porcelain, and it comprises and is selected from least a kind of rare earth element (RE) in vanadium, magnesium, yttrium, dysprosium, holmium, terbium and ytterbium and manganese, relative to barium titanate 100 moles, contain with V ₂o ₅be scaled the above-mentioned vanadium of 0.04 ~ 0.10 mole, be scaled the above-mentioned magnesium of 0.4 ~ 1.2 mole with MgO, with RE ₂o ₃be scaled the above-mentioned rare earth element (RE) of 0.30 ~ 0.48 mole and be scaled the manganese of 0.05 ~ 0.35 mole with MnO.

In addition, in capacitor of the present invention, preferably: above-mentioned dielectric-porcelain comprises and is selected from least a kind of rare earth element (RE) in vanadium, magnesium, yttrium, dysprosium, holmium, terbium and ytterbium and manganese, relative to barium titanate 100 moles, containing with V ₂o ₅be scaled the above-mentioned vanadium of 0.04 ~ 0.10 mole, be scaled the above-mentioned magnesium of 0.4 ~ 1.2 mole with MgO, with RE ₂o ₃be scaled the above-mentioned rare earth element (RE) of 0.30 ~ 0.48 mole and be scaled the above-mentioned manganese of 0.05 ~ 0.35 mole with MnO.

In addition, in capacitor of the present invention, preferred: above-mentioned dielectric-porcelain has Grain-Boundary Phase at above-mentioned intercrystalline, this Grain-Boundary Phase is formed by Grain-Boundary Phase between two that utilize multiple above-mentioned crystal grain to be formed and the triple point Grain-Boundary Phase that utilizes multiple above-mentioned crystal grain to be formed and is comprised above-mentioned rare earth element, above-mentioned magnesium and silicon, establishing the above-mentioned rare earth element between above-mentioned two in Grain-Boundary Phase, the respective concentration of above-mentioned magnesium and above-mentioned silicon is C1, if the above-mentioned rare earth element in above-mentioned triple point Grain-Boundary Phase, in each element when the respective concentration of above-mentioned magnesium and above-mentioned silicon is C2, the concentration ratio C2/C1 of 2 kinds of elements is 0.8 ~ 1.2.

In addition, in capacitor of the present invention, preferred: above-mentioned dielectric-porcelain has Grain-Boundary Phase at above-mentioned intercrystalline, above-mentioned Grain-Boundary Phase is formed by Grain-Boundary Phase between two that utilize multiple above-mentioned crystal grain to be formed and the triple point Grain-Boundary Phase that utilizes multiple above-mentioned crystal grain to be formed and is comprised above-mentioned rare earth element, above-mentioned magnesium and silicon, establishing the above-mentioned rare earth element between above-mentioned two in Grain-Boundary Phase, the respective concentration of above-mentioned magnesium and above-mentioned silicon is C1, if the above-mentioned rare earth element in above-mentioned triple point Grain-Boundary Phase, when the respective concentration of above-mentioned magnesium and above-mentioned silicon is C2, the concentration ratio C2/C1 of each element is 0.8 ~ 1.2.

Invention effect

According to the present invention, the X5R characteristic of EIA standard can be met and the high capacitor of dielectric constant.

Accompanying drawing explanation

(a) in Fig. 1 is the schematic cross-sectional view of the example representing capacitor of the present invention, and (b) is inner enlarged drawing.

Fig. 2 be represent form present embodiment the dielectric layer of capacitor and dielectric-porcelain in using barium titanate as the generalized section of the internal structure of the crystal grain of principal component.

Fig. 3 be represent in the dielectric layer of capacitor forming present embodiment and dielectric-porcelain for measure the concentration ratio of rare earth element, magnesium and silicon, the generalized section located of Grain-Boundary Phase and the triple point Grain-Boundary Phase that utilizes multiple crystal grain to be formed between utilize multiple crystal grain to be formed two.

Embodiment

For the capacitor of present embodiment, the schematic cross-sectional view based on the laminated ceramic capacitor shown in Fig. 1 is described in detail.Fig. 1 (a) is the schematic cross-sectional view of the example representing capacitor of the present invention, and (b) is inner enlarged drawing.Fig. 2 be represent form present embodiment the dielectric layer of capacitor and dielectric-porcelain in using barium titanate as the generalized section of the internal structure of the crystal grain of principal component.

The capacitor of this execution mode forms outer electrode 3 at the both ends of capacitor body 1.The alloy paste roasting of Cu or Cu and Ni is such as formed by outer electrode 3.

Capacitor body 1 is by the dielectric layer 5 be made up of dielectric-porcelain and interior electrode layer 7 is alternately laminated forms.Simplify the laminated arrangement that dielectric layer 5 and interior electrode layer 7 are shown in Fig. 1, but the capacitor of this execution mode becomes dielectric layer 5 and the interior electrode layer 7 nearly duplexer of hundreds of layers.

The dielectric layer 5 be made up of dielectric-porcelain is made up of crystal grain 9 and Grain-Boundary Phase 11, and its thickness is preferably less than 3 μm, is particularly preferably less than 2 μm, thus can laminated ceramic capacitor is small-sized, high capacity.In addition, if the thickness of dielectric layer 5 is more than 0.5 μm, then the temperature characterisitic stabilisation of static capacity can be made.

Even if interior electrode layer 7 high level dissolves also can suppress manufacturing cost, and can seek to burn till with dielectric layer 5, from this viewpoint, nickel (Ni) is applicable to simultaneously.

In the capacitor of this execution mode, the dielectric-porcelain forming dielectric layer 5 is made up of following dielectric-porcelain, it comprises crystal grain 9, above-mentioned crystal grain 9 is using barium titanate as principal component and the shell portion that to have crystal structure be tetragonal core and crystal structure is cubic system, wherein, the thickness in above-mentioned shell portion is 11.8 ~ 26.5nm, and the average grain diameter of above-mentioned crystal grain is 0.15 ~ 0.35 μm.

If the dielectric layer 5 forming laminated ceramic capacitor has the crystal grain of the scope of above-mentioned average grain diameter, and the crystal structure of crystal grain 9 is the core shell structure of the shell portion 9b with tetragonal core 9a and cubic system, the thickness t of shell portion 9b is above-mentioned scope, then can make the relative dielectric constant of dielectric layer 5 under room temperature (25 DEG C) forming capacitor is more than 3950, and the temperature characterisitic of static capacity meets the laminated ceramic capacitor of the X5R characteristic (based within the rate of change display ± 15% of static capacity when 25 DEG C in the temperature range of-55 ~ 85 DEG C) of EIA standard.

In addition, the X5R characteristic of EIA standard refers in the temperature range of-55 ~ 85 DEG C based within the rate of change display ± 15% of static capacity when 25 DEG C.

In the capacitor of this execution mode, the thickness with the shell portion 9b of the crystal grain 9 of core shell structure is 11.8 ~ 26.5nm.If the Thickness Ratio 11.8nm of shell portion 9b is thin, then the temperature characterisitic of static capacity is difficult to meet X5R characteristic, and on the other hand, if the Thickness Ratio 26.5nm of shell portion 9b is thick, then relative dielectric constant becomes lower than 3950.

In addition, in the capacitor of this execution mode, the average grain diameter formed as the crystal grain 9 of the dielectric-porcelain of dielectric layer 5 is 0.15 ~ 0.35 μm.If the average grain diameter of crystal grain 9 is less than 0.15 μm, is then difficult to form core shell structure in crystal grain 9, becomes the structure of adding ingredient solid solution to the central part of crystal grain 9, therefore the rate of temperature change of static capacity become be greater than ± 15% and do not meet the X5R characteristic of EIA standard.On the other hand, if the average grain diameter of crystal grain 9 is greater than 0.35 μm, then the rate of temperature change of static capacity become be greater than ± 15% and do not meet the X5R characteristic of EIA standard.

In addition, in the capacitor of present embodiment, preferred: the dielectric-porcelain forming dielectric layer 5 is made up of following dielectric-porcelain, it comprises and is selected from least a kind of rare earth element (RE) in vanadium, magnesium, yttrium, dysprosium, holmium, terbium and ytterbium and manganese, relative to barium titanate 100 moles, contain with V ₂o ₅be scaled the vanadium of 0.04 ~ 0.10 mole, be scaled the magnesium of 0.4 ~ 1.2 mole with MgO, with RE ₂o ₃be scaled 0.12 ~ 0.48 mole be selected from least a kind of rare earth element (RE) in yttrium, dysprosium, holmium, terbium and ytterbium and be scaled the manganese of 0.05 ~ 0.35 mole with MnO.

If the composition of dielectric-porcelain forming dielectric layer 5 is set as above-mentioned scope, then make relative dielectric constant be more than 4500 under can obtaining the state that can meet X5R characteristic in the temperature characterisitic of static capacity, simultaneously AC biasing characteristic be less than 30% and dielectric loss is the laminated ceramic capacitor of less than 5%.Here, AC biasing characteristic refer to relative to apply 0.01V/ μm exchange time dielectric constant for applying 1V/ μm exchange time the ratio of variable quantity of dielectric constant.

In addition, in the capacitor of present embodiment, preferably: the dielectric-porcelain forming dielectric layer 5 is made up of following dielectric-porcelain, wherein, relative to barium titanate 100 moles, contain with V ₂o ₅be scaled the vanadium of 0.04 ~ 0.10 mole, be scaled the magnesium of 0.5 ~ 1.2 mole with MgO, with RE ₂o ₃be scaled the rare earth element (RE) of 0.30 ~ 0.48 mole and be scaled the manganese of 0.05 ~ 0.35 mole with MnO.If the dielectric-porcelain forming dielectric layer 5 is set as above-mentioned composition, then can reduce AC biasing characteristic further.

In the capacitor of this execution mode, as long as the scope of desired dielectric property can be being maintained, then in dielectric-porcelain, glass ingredient or other adding ingredient can contained as the auxiliary agent for improving agglutinating property using the ratio of below 4 quality %.

Forming the structure that shell portion 9b surrounds core 9a in the capacitor of present embodiment, confirming that by using the analysis being attached to the transmission electron microscope of elemental analyzer (EDS) shell portion 9b surrounds the crystal grain 9 of core 9a.Extract out the sample made from processing laminated ceramic capacitor 10 ~ 20 particle diameters average grain diameter ± scope of 30% in crystal grain 9, as the sample analyzed.The spot size of electron beam when carrying out elementary analysis is set as 1 ~ 3nm, and the position of carrying out analyzing is set as from the surface of crystal grain 9 and crystal boundary to the region of central portion.In this case, obtain the concentration of element (magnesium or rare earth element) from the surface of crystal grain 9 and crystal boundary towards the every 5 ~ 10nm of central portion, make the chart that transverse axis is distance, the longitudinal axis is the concentration of element.Here, in chart, light from the mensuration closest to crystal boundary side and get 3 points successively, near linear is described with these 3, concentration gradient using the slope of this straight line as the element of skin section side, in addition, lights from the mensuration of the center side closest to crystal grain 9 in the measuring point in the scope of the crystal boundary 30 ~ 100nm of distance crystal grain 9 and gets 3 points successively, near linear is described, the concentration gradient using the slope of this straight line as the element of central portion side by these 3.Further, the concentration gradient of the element in skin section side be 0.15 more than atom %/nm and the concentration gradient of the element of central portion side is 0.5 below atom %/nm time, formed core shell structure.

Then, utilize X-ray diffraction method to obtain and form the core 9a of crystal grain 9 and the respective crystal structure of shell portion 9b.First, according to the X-ray diffraction pattern of dielectric layer 5, (004) face ((040) face, (400) face overlap of the cubic system of the expression barium titanate occurred between tetragonal (004) face representing barium titanate and (400) face.) diffracted intensity with the diffracted intensity of any surface represented in tetragonal (400) face of barium titanate and (004) face equal or larger than it time, crystal grain 9 has the crystal structure of tetragonal system and cubic system.

And, the crystal grain 9 confirmed by utilizing transmission electron microscope has core 9a and surrounds the result that the analysis result of shell portion 9b of core 9a and crystal grain 9 have the crystal structure of tetragonal system and cubic system, judges that crystal grain 9 has tetragonal core 9a and surrounds the shell portion 9b of cubic system of core 9a.

Then, for being judged to be, there is tetragonal core 9a and the crystal grain 9 of the shell portion 9b of the cubic system of encirclement core 9a, obtaining the thickness in the shell portion of crystal grain 9.The thickness of the shell portion 9b of crystal grain 9 is based on use Japanese Unexamined Patent Publication 2006-137647 publication or J.Am.Ceram.Soc., and the evaluation method of the X-ray diffraction method shown in 90 [4] 1107-1111 (2007), is obtained by following formula.

For the crystal structure of the crystal grain 9 as object, in the X-ray diffraction pattern measured, broaden compared with the reflection of selected X-ray diffraction pattern and pure regular crystal (hkl) or cubic crystal (h ' k ' l '), comprised the pattern of the reflection of regular crystal (hkl) and cubic crystal (h ' k ' l ') by the qualification selection of peak position.

And, diffraction data as object is the reflection of regular crystal (hkl) and cubic crystal (h ' k ' l '), is obtained the parameter such as shape function at peak intensity (=integrated intensity), 2 θ positions of summit, half breadth, peak by diffraction maximum.Now, peak separation is carried out as required.In this case, the condition that peak is separated is set as: background function: zero degree multinomial, radiating light: K α 1, profile (profile) function: thepsedo-Voigt function, half breadth: the objectivity for the different half breadth of all reflections, profile: object and data resolution capability: sensitive (minimum half breadth: about 0.1 °).In addition, peak can use commercial software (such as PROFIT) in being separated, and the instrument be separated for peak is not particularly limited.

[mathematical expression 1]

d _obs＝(0.9×λ)/(β×cosθ)

D _obs: the thickness in shell portion

λ: wavelength

θ: Bragg angle (deg)

β: the half breadth (unit: radian) of the reality obtained by following formula

[mathematical expression 2]

β＝√(B ²-b ²)

B: the measured value of the peak half breadth of (h ' k ' l ') of cubic crystal

B: device constant

In addition, the average grain diameter of crystal grain 9 measures according to following step.First, the plane of disruption of the sample as capacitor body 1 after burning till is ground.Afterwards, to the sample photo of scanning electron microscope shooting interior tissue through grinding, this photo is described the circle including 50 ~ 100 crystal grain in, selects in circle and the crystal grain of circumference.Then, image procossing is carried out to the profile of each crystal grain, obtains the area of each crystal grain, calculate the diameter converting to and there is bowlder of the same area, obtained by its mean value.

In addition, about the composition of dielectric-porcelain, to analyze and atomic absorption spectroscopy is obtained laminated ceramic capacitor being dissolved in the solution ICP (InductivelyCoupledPlasma, inductively coupled plasma) that obtains in acid.In this case, if the valence mumber of each element obtains oxygen amount for the valence mumber shown in periodic table.

In addition, in the capacitor of present embodiment, the Grain-Boundary Phase 11 formed as the dielectric-porcelain of dielectric layer 5 has Grain-Boundary Phase and the triple point Grain-Boundary Phase utilizing multiple crystal grain 9 to be formed between two that utilize multiple crystal grain 9 to be formed, about the rare earth element comprised in dielectric-porcelain, magnesium and silicon, preferred: between two between Grain-Boundary Phase and triple point Grain-Boundary Phase, if the rare earth element between two in Grain-Boundary Phase, the respective concentration of magnesium and silicon is C1, if the rare earth element in triple point Grain-Boundary Phase, when the respective concentration of magnesium and silicon is C2, rare earth element, the C2/C1 of 2 kinds of elements in magnesium and silicon is 0.8 ~ 1.2.If the C2/C1 of 2 kinds of elements in rare earth element, magnesium and silicon is 0.8 ~ 1.2, then, at the temperature (such as, 85 DEG C) higher than room temperature (25 DEG C), the deviation (CV) of the static capacity of capacitor can be reduced.And then, when the C2/C1 of the whole element of rare earth element, magnesium and silicon is 0.8 ~ 1.2, the deviation (CV) of the static capacity of the capacitor at the temperature (such as, 85 DEG C) higher than room temperature (25 DEG C) can be made to reduce further.

Fig. 3 be in the dielectric layer 5 i.e. dielectric-porcelain representing the capacitor forming present embodiment for measure the concentration ratio of rare earth element, magnesium and silicon, the generalized section located of Grain-Boundary Phase 11a and the triple point Grain-Boundary Phase 11b that utilizes multiple crystal grain 9 to be formed between utilize multiple crystal grain 9 to be formed two.

The concentration of rare earth element, magnesium and silicon between two in Grain-Boundary Phase 11a and triple point Grain-Boundary Phase 11b utilizes the X-ray microanalysis device (XMA) set up in transmission electron microscope to obtain.In this case, the sample that the sample for analyzing uses the laminal dielectric-porcelain cut out the dielectric layer 5 from capacitor to carry out ion milling (ionmilling) processing and obtains.When the region analyzed is set as that between to two that utilize multiple crystal grain 9 to be formed Grain-Boundary Phase 11a and the triple point Grain-Boundary Phase 11b utilizing multiple crystal grain 9 to be formed analyses and observe, by least 3 crystal grain 9 maximum gauge average grain diameter ± 20% within scope in crystal grain 9 groups of positions formed.And, use X-ray microanalysis device (XMA), as shown in Figure 3, obtain the respective concentration of the rare earth element of the position S1 of Grain-Boundary Phase 11a between two and the position S2 of triple point Grain-Boundary Phase 11b, magnesium and silicon, obtain the concentration C 1 of each element between two in Grain-Boundary Phase 11a and the ratio C2/C1 of the concentration C 2 of each element in triple point Grain-Boundary Phase 11b respectively.Now, between two that carry out analyzing, the position S1 of Grain-Boundary Phase 11a is the substantial middle of the width of Grain-Boundary Phase 11, and the position S2 of triple point Grain-Boundary Phase 11b is the central authorities of triple point Grain-Boundary Phase 11b.In addition, between two, the position S1 of Grain-Boundary Phase 11a is set as that distance determines the position of position more than the 50nm of the position S2 of triple point Grain-Boundary Phase 11b.

Then, the method for the capacitor manufacturing present embodiment is described.

First, the organic resin such as dielectric medium powder and polyvinyl butyral resin, toluene and alcohol equal solvent one are reinstated ball mill etc. and prepares ceramic size, then, ceramic size is formed ceramic green sheet (ceramicgreensheet) with scraping the sheet forming technique such as the skill in using a kitchen knife in cookery or mould Tu Fa on base material.From the viewpoint of for make dielectric layer 5 high capacity thin layer, maintain high-insulativity, the thickness of ceramic green sheet is preferably 1 ~ 5 μm.

The dielectric medium powder used in the method for making of the laminated ceramic capacitor of present embodiment uses barium titanate powder (hereinafter referred to as BT powder.The mol ratio of Ba/Ti is 1.001 ~ 1.009).In addition, the average grain diameter of BT powder is preferably 0.21 ~ 0.30 μm.In method for the manufacture of the laminated ceramic capacitor of present embodiment, as for the formation of the BT powder of crystal grain 9 of dielectric-porcelain becoming dielectric layer 5, use average grain diameter is the powder of the scope of 0.21 ~ 0.30 μm, thus suppress the adding ingredient comprising rare earth element (RE) to the solid solution of BT powder, the shell portion of thickness described later can be formed.Make the thin layer of dielectric layer 5 become easy thus, dielectric constant is high, the crystal grain 9 of the X5R characteristic that meets EIA standard to utilize firing condition described later can make with BT powder.

The powder that the dielectric medium powder that uses when manufacturing the capacitor of this execution mode uses whole composition of the such as vanadium of coating ormal weight using barium titanate as principal component and thereon described later, magnesium, rare earth element, manganese and sintering aid and obtains is better.

In this case, the dielectric medium powder used such as is prepared in the following manner.First, purity be more than 99.9%, the mol ratio of Ba/Ti is 1.001 ~ 1.009, average grain diameter is in the suspension of barium titanate powder (BT powder) of 0.21 ~ 0.30 μm, use ammoniacal liquor as pH adjusting agent, pH is set as the scope of 6 ~ 8, add the lithium aqueous solution, Ludox, the brium carbonate aqueous solution, magnesium hydroxide aqueous solution, calcium hydroxide aqueous solution, the ammonium vanadate aqueous solution, the manganese acetate aqueous solution wherein successively and be selected from the aqueous solution of at least a kind of rare earth element in yttrium, dysprosium, holmium, terbium and ytterbium and mix, thus preparing ceramic size.In addition, for the reason that be mixed into, obtain high dielectric property of inhibition of impurities to obtained dielectric-porcelain, the purity of these source chemicals is more than 99.5% better.

Then, being dropped into by this ceramic size possesses in the spray dryer of four fluid tips, the drop that diameter is less than 10 μm is generated from four fluid tips, drying process is carried out at temperature near 200 DEG C, make the precursor of dielectric medium powder, then, at the temperature higher than the temperature of drying process, heat treated is carried out to the precursor of this dielectric medium powder, prepare dielectric medium powder thus.

As the composition of dielectric medium powder, preferably setting BT powder as ammonium vanadate aqueous solution when 100 moles is with V ₂o ₅be scaled 0.04 ~ 0.10 mole, magnesium hydroxide aqueous solution with MgO be scaled 0.5 ~ 1.2 mole, the manganese acetate aqueous solution with MnO be scaled 0.05 ~ 0.35 mole and be selected from least a kind of rare earth element (RE) in yttrium, dysprosium, holmium, terbium and ytterbium the aqueous solution with RE ₂o ₃be scaled the composition of 0.12 ~ 0.48 mole, can obtain that dielectric constant is high thus and the temperature characterisitic of static capacity meets the little laminated ceramic capacitor of X5R characteristic, AC biasing characteristic and dielectric loss.

In addition, the addition of sintering aid is adjusted to relative to BT powder 100 mass parts is 0.5 ~ 2.0 mass parts.The agglutinating property of dielectric-porcelain can be improved thus further.Its composition is preferably: Li ₂o=1 ~ 15 % by mole, SiO ₂=40 ~ 60 % by mole, BaO=15 ~ 35 % by mole and CaO=5 ~ 25 % by mole.

Then, on the interarea of obtained ceramic green sheet, printing forms the internal electrode pattern of rectangular shape.Form the conductor paste of internal electrode pattern by as principal component metal using Ni or their alloy powder also mixing the ceramic powders as versatile material wherein and add organic bond, solvent and dispersant to prepare.In addition, in order to eliminate the difference of height caused because of internal electrode pattern on ceramic green sheet, preferably around internal electrode pattern, ceramic pattern is formed with the thickness substantially identical with internal electrode pattern.In this case, the aspect that burning till from make simultaneously to burn till is punctured into same degree is considered, the ceramic component forming ceramic pattern preferably uses the dielectric medium powder used in ceramic green sheet.

Then, by be formed with internal electrode pattern ceramic green sheet overlap desired by sheet number, do not form the ceramic green sheet of internal electrode pattern thereon with the overlapping multi-disc of mode making levels reach same piece number, thus form interim duplexer.Internal electrode pattern in interim duplexer respectively staggers half pattern along its length.Utilize so stacked construction method, internal electrode pattern can be formed in the mode of the end face alternately exposing the duplexer after cut-out.

In addition, the capacitor of present embodiment except can by except carrying out stacked construction method to be formed after the interarea of ceramic green sheet is pre-formed internal electrode pattern, can also be formed by following construction method, namely, after making ceramic green sheet mechanical material that is temporary transient and lower layer side closely sealed, printing internal electrode pattern also makes it dry, do not print the ceramic green sheet of internal electrode pattern overlapping on printing, dry internal electrode pattern and make it temporarily closely sealed, successively carrying out the printing of the closely sealed of ceramic green sheet and internal electrode pattern.

Then, by interim duplexer with above-mentioned interim stacked time temperature, pressure compared with high temperature, high pressure condition under suppress, form ceramic green sheet and the closely sealed securely duplexer of internal electrode pattern.

Then, by duplexer is cut into clathrate, the capacitor body formed body that the end forming internal electrode pattern is exposed.

Then, burn till after obtained capacitor body formed body degreasing.Burn till preferably maximum temperature be set as 1150 ~ 1230 DEG C, the retention time be set as 0.1 ~ 4 hour, carry out in the atmosphere of hydrogen-nitrogen.Then, by carrying out oxidation processes again in the temperature range of 900 ~ 1100 DEG C, thus capacitor body 1 is obtained.Then, as required, carry out the chamfered edge of the ridgeline portions of capacitor body 1, and in order to make the interior electrode layer 7 exposed expose from the relative end face of capacitor body 1, also can implement barreling.By burning till in such a situa-tion, thus can obtain the average grain diameter of crystal grain 9 forming dielectric layer 5 to be set as the scope of 0.15 ~ 0.35 μm, the crystal structure of crystal grain 9 are by tetragonal core 9a with surround core and solid solution has the shell portion 9b of the cubic system of at least a kind of adding ingredient in above-mentioned vanadium, magnesium, rare earth element (RE) and manganese to form and the thickness of shell portion 9b is the capacitor body 1 of 10 ~ 20nm.

In addition, when manufacturing the capacitor of present embodiment, preferred: after by obtained capacitor body formed body degreasing and reach maximum temperature in hydrogen-nitrogen atmosphere before, the heat treatment step temporarily keeping 0.5 ~ 3 hours at the temperature of 900 ~ 1000 DEG C is set.By arranging such heat treatment step, thus the composition difference of rare earth element, magnesium and glass ingredient between two that can reduce crystal grain 9 in Grain-Boundary Phase 11a and triple point Grain-Boundary Phase 11b, the deviation (CV) of the static capacity of capacitor at the temperature (about 85 DEG C) higher than room temperature (25 DEG C) can be reduced thus.Here, the deviation (CV) of static capacity is the value represented with the ratio (σ/x) of standard deviation (σ) by the mean value (x) obtained using the measured value of the static capacity of multiple sample as parameter.

As mentioned above, for the capacitor of present embodiment, when making dielectric layer 5, use the material of vanadium, magnesium, rare earth element (RE), manganese and the whole composition of sintering aid being also coated to ormal weight using barium titanate as principal component thereon, obtained unprocessed capacitor body formed body is burnt till under the firing condition that programming rate is high, the crystal grain 9 that the average thickness of shell portion 9b is little can be obtained thus.

Then, be coated with outer electrode paste in the relative end of this capacitor body 1 and carry out roasting, forming outer electrode 3.In addition, according to circumstances, the plated film for improving installation is formed on the surface of this outer electrode 3.Capacitor of the present invention can be obtained like this.

Embodiment 1

First, as material powder, prepare the barium titanate powder (hereinafter referred to as BT powder) that purity is 99.9%, the mol ratio of Ba/Ti is 1.005.

Then, in the suspension of BT powder, use ammoniacal liquor as pH adjusting agent, pH is adjusted to the scope of 6 ~ 8.Then, add the lithium aqueous solution, Ludox, the brium carbonate aqueous solution, magnesium hydroxide aqueous solution, calcium hydroxide aqueous solution, the ammonium vanadate aqueous solution, the manganese acetate aqueous solution wherein successively and be selected from the aqueous solution of at least a kind of rare earth element in yttrium, dysprosium, holmium, terbium and ytterbium and mix, thus preparing ceramic size.

Then, being dropped into by this ceramic size possesses in the spray dryer of four fluid tips, the drop that diameter is less than 10 μm is generated from four fluid tips, drying process is carried out at temperature near 200 DEG C, make the precursor of dielectric medium powder, then, the precursor of this dielectric medium powder is carried out heat treated at 400 DEG C, be prepared in the dielectric medium powder of the vanadium of the surface-coated ormal weight of BT powder, magnesium, rare earth element, manganese and the whole composition of sintering aid.Sintering aid is according to becoming SiO ₂=55, BaO=20, CaO=15, Li ₂the mode of the composition of O=10 (% by mole) adjusts composition, and in addition, it is 1 mass parts that the addition of this sintering aid is adjusted to relative to BT powder 100 mass parts.In addition, make sample (sample No.33) as the glass powder of sintering aid is added to the BT powder of the vanadium being coated with ormal weight, magnesium, rare earth element and manganese.

Then, obtained dielectric medium powder and polyvinyl butyral resin are put in the mixed solvent of toluene and ethanol, use the zirconia ball of diameter 1mm to carry out wet mixed, prepare ceramic size, utilize scraper legal system to make the ceramic green sheet of thickness 2 μm.

Then, the internal electrode pattern of multiple rectangular shape will be formed as the conductor paste of principal component using Ni at the upper surface of this ceramic green sheet.Ni powder 100 mass parts that it is 0.3 μm that conductor paste for the formation of internal electrode pattern uses average grain diameter with the addition of the conductor paste of BT powder.

Then, by stacked 200 of the ceramic green sheet being printed with internal electrode pattern, below stacked 20 ceramic green sheets not printing internal electrode pattern respectively thereon, with forcing press (pressingmachine) at temperature 60 C, pressure 10 ⁷make it closely sealed under Pa, the condition of 10 minutes time, make duplexer, then, this duplexer is cut into the size of regulation, form capacitor body formed body.

Then, after capacitor body formed body is carried out the process of unsticking mixture in an atmosphere, in hydrogen-nitrogen, programming rate is set as 2000 DEG C/h, burns till at the temperature shown in table 1, make capacitor body.This burns till and uses roller hearth furnace to carry out.In addition, the sample (sample No.34) programming rate being set as 500 DEG C/h is made.

Then, made capacitor body oxidation processes 4 hours again at 1000 DEG C in nitrogen atmosphere.The size of this capacitor body is 2.05 × 1.28 × 1.28mm ³, the thickness of dielectric layer is 2.0 μm, and the effective area of 1 layer of interior electrode layer is 1.78mm ².In addition, the area of the part that the interior electrode layer that the mode that effective area refers to expose the different end face of capacitor body respectively is alternately formed in stacked direction overlaps each other.

Then, after barreling is carried out to capacitor body, contain the outer electrode paste of Cu powder and glass in the coating of the both ends of capacitor body, at 850 DEG C, carry out roasting, form outer electrode.Then, use electrolysis cleaning mill, plating Ni and plating Sn is carried out successively to the surface of this outer electrode, makes laminated ceramic capacitor.

Then, following evaluation is carried out to these laminated ceramic capacitors.About the relative dielectric constant under room temperature (25 DEG C), use LCR meter (Hewlett-PackardCompany system), under the condition of temperature 25 DEG C, frequency 1.0kHz, AC voltage 1.0V/ μm, measure static capacity, and obtained by the thickness of dielectric layer and the effective area of interior electrode layer.

Dielectric loss also uses identical LCR to count and measures under the condition identical with static capacity.In addition, about the temperature characterisitic of static capacity, in the scope of temperature-55 ~ 85 DEG C, static capacity is measured.

About AC biasing characteristic, under the condition being located at temperature 25 DEG C, frequency 1.0kHz, AC voltage 0.01 ~ 3.5V/ μm the static capacity applied when exchanging (AC) voltage 0.01V/ μm be C1, be located at temperature 25 DEG C, the static capacity of frequency 1.0kHz when applying AC voltage 3.5V/ μm be when being C2, obtains AC biasing characteristic by ((C2-C1)/C1) × 100 (%).

The average grain diameter forming the crystal grain of dielectric layer is tried to achieve as follows, namely, after the plane of disruption of the sample as capacitor body after burning till is ground, with the photo of scanning electron microscope shooting interior tissue, this photo is described the circle including 30 crystal grain in, selects in circle and the crystal grain of circumference, image procossing is carried out to the profile of each crystal grain, obtain the area of each particle, calculate the diameter converting to and there is bowlder of the same area, obtain average grain diameter by its mean value.

Then, whether the crystal grain by using the analysis being attached to the transmission electron microscope of elemental analyzer (EDS) to confirm to have core and shell portion is the crystal grain that shell portion surrounds core.As the sample analyzed, extract out the sample of the TEM made from processing laminated ceramic capacitor 10 ~ 20 particle diameters average grain diameter ± crystal grain of the scope of 30%.The spot size of electron beam when carrying out elementary analysis is set as 1 ~ 3nm, and the position of analysis is set as surface from crystal grain and the region of crystal boundary to central portion.In this case, obtain the concentration of rare earth element every 5 ~ 10nm from the surface of crystal grain and crystal boundary to central portion, make that transverse axis is distance, the longitudinal axis is the chart of concentration of element.Here, in chart, light from the mensuration closest to crystal boundary side and get 3 points successively, describe near linear, using the concentration gradient of the slope of this straight line as the element of skin section side with these 3.In addition, light from the mensuration of the center side closest to crystal grain in the measuring point in the scope of the crystal boundary 30 ~ 100nm of distance crystal grain and get 3 points successively, describe near linear, using the concentration gradient of the slope of this straight line as the element of central portion side by these 3.In this case, the concentration gradient of the element of crystal boundary side be 0.15 more than atom %/nm and the concentration gradient of the element of central portion side is 0.5 below atom %/nm time, formed core shell structure.

Then, utilize X-ray diffraction method to obtain and form the core of crystal grain and the respective crystal structure in shell portion.First, the X-ray diffraction pattern of the sample obtained according to dielectric layer is pulverized, (004) face ((040) face, (400) face overlap of the cubic system of the expression barium titanate occurred between tetragonal (004) face representing barium titanate and (400) face.) diffracted intensity with the diffracted intensity of any one represented in tetragonal (400) face of barium titanate and (004) face equal or larger than it time, crystal grain has the crystal structure of tetragonal system and cubic system.

And, the crystal grain confirmed by utilizing transmission electron microscope has core and surrounds the result that the analysis result in shell portion of core and crystal grain have the crystal structure of tetragonal system and cubic system, judges that crystal grain has tetragonal core and surrounds the shell portion of cubic system of core.

Then, for being judged to be, there is tetragonal core and the crystal grain 9 in the shell portion of the cubic system of encirclement core, utilizing following method to obtain the thickness in the shell portion of crystal grain.

The thickness of the shell of crystal grain utilizes above-mentioned numerical expression 1 and numerical expression 2 to obtain.Now, X-ray diffraction device uses the X ' Pertpro of Panalytical Inc..Now, for the crystal structure of the crystal grain as object, in the X-ray diffraction pattern measured, broaden compared with the reflection of selected X-ray diffraction pattern and pure regular crystal (hkl) or cubic crystal (h ' k ' l '), comprised the pattern of the reflection of regular crystal (hkl) and cubic crystal (h ' k ' l ') by the qualification selection of peak position.

Further, diffraction maximum using (002), (200) of regular crystal, cubic crystal (200) as measure object.The size of beam is set as longitudinal 0.5mm, horizontal direction 5mm.Wavelength is set as in the mensuration of dielectric-porcelain, be set as 0.02 ° by wide for step, the gate time of every 1 is set as 5.0 seconds.In addition, round number of times is set as 10 times, adding up as diffracted intensity using 10 secondary amounts.In addition, in evaluation, use peak to be separated software (PROFIT) and by diffraction maximum, peak separation is carried out to (002), (200) of regular crystal, (200) of cubic crystal under the following conditions.The condition that peak is separated is set as: background function: zero degree multinomial, radiating light: K α 1, profile function: thepsedo-Voigt function, half breadth: the objectivity for the different half breadth of all reflections, profile: object, data resolution capability: sensitive (minimum half breadth: about 0.1 °) and analyst coverage: 44 ° of < 2 θ < 47 °.

In addition, the composition analysis of the sample as sintered body obtained utilizes ICP (InductivelyCoupledPlasma) to analyze and atomic absorption spectroscopy is carried out.In this case, obtained dielectric-porcelain is mixed with boric acid and sodium carbonate, be dissolved in after making its melting in hydrochloric acid, first, atomic absorption spectroscopy is utilized to carry out the qualitative analysis of contained element in dielectric-porcelain, then, for specific each element, using the dilution of titer as standard specimen, carry out quantification with ICP emission spectrographic analysis.In addition, if the valence mumber of each element obtains oxygen amount for the valence mumber shown in periodic table.In addition, the composition of the dielectric layer of the formation laminated ceramic capacitor obtained is consistent with the composition shown in table 1.

Allotment composition and firing condition are shown in Table 1, the result of the average grain diameter of the crystal grain of the formation dielectric layer in obtained laminated ceramic capacitor and dielectric property (temperature characterisitic of relative dielectric constant, static capacity, AC biasing characteristic, dielectric loss) is shown in Table 2.

[table 1]

[table 2]

*: zero represents that core is tetragonal system, shell portion is the core shell structure of cubic system

× expression is not core is tetragonal system, shell portion is the core shell structure of cubic system

*: zero represent in-55 ~ 85 DEG C based on the rate of change of static capacity when 25 DEG C within ± 15%

× represent in-55 ~ 85 DEG C based on the rate of change of static capacity when 25 DEG C be greater than ± 15%

By table 1,2 result show, in sample No.I-1 ~ 4, I-6 ~ 10, I-12, I-13, I-15 ~ 19, I-21 ~ 24, I-26 ~ 29 and I-31 ~ 34, relative dielectric constant under room temperature (25 DEG C) is more than 3950, and the temperature characterisitic of static capacity meets X5R characteristic.

In addition, in sample No.I-2 ~ 4, I-6 ~ 10, I-12, I-13, I-16 ~ 19, I-22 ~ 24, I-27 ~ 29, I-31 and I-32, relative dielectric constant under room temperature (25 DEG C) is more than 4500, and the temperature characterisitic of static capacity meets X5R characteristic, AC biasing characteristic is less than 30%, and then dielectric loss is less than 5%.

Particularly with relative to barium titanate 100 moles containing with V ₂o ₅be scaled the above-mentioned vanadium of 0.04 ~ 0.1 mole, be scaled the above-mentioned magnesium of 0.5 ~ 1.2 mole with MgO, with RE ₂o ₃the dielectric-porcelain of the above-mentioned rare earth element (RE) being scaled 0.3 ~ 0.48 mole and the above-mentioned manganese being scaled 0.05 ~ 0.35 mole using MnO is as in sample No.No.I-2 ~ 3 of dielectric layer, I-6 ~ 10, I-12, I-13, I-16 ~ 19, I-22 ~ 24, I-27 ~ 29, I-31 and I-32, relative dielectric constant under room temperature (25 DEG C) is more than 4500, the temperature characterisitic of static capacity meets X5R characteristic, AC biasing characteristic is less than 29.00%, and then dielectric loss is less than 5%.

On the other hand, in sample No.I-5, I-11, I-14, I-20, I-25, I-30 and I-35, the relative dielectric constant do not met under room temperature (25 DEG C) be more than 3950 and the temperature characterisitic of static capacity meet arbitrary characteristic in X5R characteristic.

Embodiment 2

Then, in firing process, after by the capacitor formation body degreasing of making and before burning till with maximum temperature, carry out the heat treatment of 1 hour at temperature temporarily shown in table 3, in addition, all utilize method similarly to Example 1 to make sample, and carry out same evaluation, and then, be determined at the static capacity at 85 DEG C, obtain its deviation (CV).The deviation of static capacity is obtained by 32 samples respectively.

In addition, the concentration of rare earth element, magnesium and silicon between two in dielectric-porcelain in Grain-Boundary Phase and triple point Grain-Boundary Phase utilizes the X-ray microanalysis device (XMA) set up in transmission electron microscope to obtain.In this case, the sample that the sample for analyzing uses the laminal dielectric-porcelain cut out the dielectric layer from made laminated ceramic capacitor to carry out ion milling processing and obtains.Close the region analyzed, when Grain-Boundary Phase between two and triple point Grain-Boundary Phase are analysed and observe, select 5 places by least 3 crystal grain maximum gauge average grain diameter ± 20% within scope in the position that forms of crystal grain group.And, use X-ray microanalysis device (XMA), as shown in Figure 3, obtain the concentration of the rare earth element of the position S1 of Grain-Boundary Phase between two and the position S2 of triple point Grain-Boundary Phase, magnesium and silicon, obtain the mean value of the concentration C 1 of the element between two in Grain-Boundary Phase and the ratio C2/C1 of the concentration C 2 of the element in triple point Grain-Boundary Phase.Now, between two that analyze, the position S1 of Grain-Boundary Phase is set as the substantial middle of the width of Grain-Boundary Phase, and the position S2 of triple point Grain-Boundary Phase is set as the central authorities of triple point Grain-Boundary Phase.In addition, between two, the position S1 of Grain-Boundary Phase is set as that distance determines that the position of the position S2 of triple point Grain-Boundary Phase is about the position of 50nm.Manufacturing conditions is shown in Table 3, the evaluation result of dielectric property etc. is shown in Table 4.In addition, sample N is confirmed _o.II-1 ~ 28 all have core shell structure, and wherein, core is tetragonal system, and shell portion is cubic system.

[table 3]

[table 4]

#: ◎ represent the C2/C1 of the whole element of rare earth element, magnesium and silicon than be 0.8 ~ 1.20 scope in

The C2/C1 of the zero 2 kinds of elements represented in rare earth element, magnesium and silicon is in the scope of 0.8 ~ 1.2

The C2/C1 of a kind of element that △ represents in rare earth element, magnesium and silicon be 0.8 ~ 1.2 scope in the CV value (standard deviation/mean value x) of direct capacitance value at ##:85 DEG C

(condition determination: frequency 1.0kHz, AC voltage are 1.0V/ μm, sample number n=32)

By table 3,4 result show, the made relative dielectric constant of sample (sample No.II-1 ~ 28) all in the same manner as the sample utilizing the method for embodiment 1 to make under room temperature (25 DEG C) is more than 3950, and the temperature characterisitic of static capacity meets X5R characteristic.In addition, AC biasing characteristic is less than 30%, and dielectric loss is less than 5%.Wherein, in the mill, the heat treatment step kept after by obtained capacitor body formed body degreasing and under being increased in the temperature shown in table 3 reach maximum temperature in hydrogen-nitrogen atmosphere before and sample (sample No.II-1 ~ 23 of the laminated ceramic capacitor made, 25 ~ 28) with heat treatment step is not set and carries out compared with the sample (sample No.II-24) that burns till, the deviation (CV) of static capacity is all little of less than 2%, particularly the temperature of heat treatment step is set as sample (sample No.II-1 ~ 21 of 900 ~ 1000 DEG C, 25 ~ 28) in, the deviation (CV) of static capacity is less than 1.5%.

Symbol description

1 capacitor body

3 outer electrodes

5 dielectric layers

7 interior electrode layers

9 crystal grain

9a core

9b shell portion

11 Grain-Boundary Phases

Grain-Boundary Phase between 11a bis-

11b triple point Grain-Boundary Phase

Claims

1. a capacitor, it is characterized in that, dielectric layer is made up of dielectric-porcelain, described dielectric-porcelain has crystal grain and is positioned at this intercrystalline Grain-Boundary Phase, described crystal grain using barium titanate as principal component, comprise rare earth element RE, magnesium and silicon and to have crystal structure be tetragonal core and surround this core and the crystal structure shell portion that is cubic system, wherein, the thickness in described shell portion is 11.8 ~ 20.8nm, and the average grain diameter of described crystal grain is 0.17 ~ 0.34 μm

Described Grain-Boundary Phase is formed by Grain-Boundary Phase between two that utilize multiple described crystal grain to be formed and the triple point Grain-Boundary Phase that utilizes multiple described crystal grain to be formed and is comprised described rare earth element, described magnesium and described silicon, establishing the described rare earth element between described two in Grain-Boundary Phase, the respective concentration of described magnesium and described silicon is C1, if the described rare earth element in described triple point Grain-Boundary Phase, the respective concentration of described magnesium and described silicon is C2, if described rare earth element, when the concentration in described triple point Grain-Boundary Phase of any one element in described magnesium and described silicon and the ratio of the concentration between described two in Grain-Boundary Phase are C2/C1, described rare earth element, the respective C2/C1 of 2 kinds of elements in described magnesium and described silicon is 0.8 ~ 1.2.

2. capacitor according to claim 1, is characterized in that, described dielectric-porcelain comprises: vanadium; Described magnesium; Be selected from as at least a kind in the yttrium of rare earth element RE, dysprosium, holmium, terbium and ytterbium; Manganese; With described silicon,

Relative to barium titanate 100 moles, described vanadium is with V ₂o ₅be scaled 0.04 ~ 0.10 mole, described magnesium is scaled 0.4 ~ 1.2 mole with MgO, described rare earth element RE is with RE ₂o ₃be scaled 0.12 ~ 0.48 mole and described manganese is scaled 0.05 ~ 0.35 mole with MnO.

3. capacitor according to claim 2, is characterized in that, described rare earth element RE is with RE ₂o ₃be scaled 0.30 ~ 0.48 mole.

4. capacitor according to claim 1, it is characterized in that, establishing the described rare earth element between described two in Grain-Boundary Phase, the respective concentration of described magnesium and described silicon is C1, if the described rare earth element in described triple point Grain-Boundary Phase, the respective concentration of described magnesium and described silicon is C2, if described rare earth element, when the concentration in described triple point Grain-Boundary Phase of any one element in described magnesium and described silicon and the ratio of the concentration between described two in Grain-Boundary Phase are C2/C1, described rare earth element, the C2/C1 of each element in described magnesium and described silicon is 0.8 ~ 1.2.

5. capacitor according to any one of claim 1 to 4, it is characterized in that, described crystal grain is 0.15 more than atom %/nm at the described magnesium of skin section side or the concentration gradient of described rare earth element, is 0.5 below atom %/nm at the described magnesium of central portion side or the concentration gradient of described rare earth element.