CN103262190A

CN103262190A - Capacitor with a capacitor element

Info

Publication number: CN103262190A
Application number: CN2012800037448A
Authority: CN
Inventors: 山口胜义; 上野纯; 松原圣; 向山将太
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2011-12-17
Filing date: 2012-12-17
Publication date: 2013-08-21
Anticipated expiration: 2032-12-17
Also published as: JP5535402B2; CN103262190B; JPWO2013089269A1; WO2013089269A1

Abstract

The invention provides a capacitor capable of maintaining high electrostatic capacitance even when a voltage is applied at a high temperature. The capacitor is provided with a dielectric layer formed by a dielectric ceramic, wherein the dielectric ceramic is provided with crystal grains (9) taking barium titanate as a main component and contains at least one rare earth element (RE) selected from terbium, dysprosium, holmium, erbium and gadolinium, the crystal grains (9) comprise at least two crystal grains (9 a, 9 b) with the difference of the concentration of the rare earth element (RE) of more than 0.1 atomic percent at a position 20nm deep from a crystal boundary, and the crystal structure of the crystal grains (9) is a core-shell structure.

Description

Capacitor

Technical field

The present invention relates to the capacitor of dielectric ceramics as dielectric layer, it is the crystal grain of principal component that described dielectric ceramics comprises with the barium titanate.

Background technology

In recent years, along with the exploitation of the blue LED (LED:Light Emitting Diode) of high brightness, can realize high visual full color (full color) LED display unit and be the exploitation develop rapidly of the lighting apparatus of light emitting source with LED.

Use in the electronic equipment of such LED, the AC-DC transducer that is to use that adopts is generated the mode of the direct voltage that is used for driving LED by source power supply, the AC-DC transducer is that the alternating voltage by source power supply (100V) generates desirable VD and the circuit of driving LED, is used for being equipped with on the rectification circuit of such circuit FET (MOSFET) and capacitor (for example referring to Patent Document 1) as the control circuit element.

But, use in the electronic equipment of such LED, the voltage height that not only applies, and also the variations in temperature that the heating when luminous causes is big, therefore, as capacitor, requires to develop the capacitor that also can keep high static capacity when applying voltage.

The prior art document

Patent documentation

Patent documentation 1: TOHKEMY 2011-35112 communique

Summary of the invention

The problem that invention will solve

The present invention is the invention of finishing in view of the above problems, and its purpose is, the capacitor that also can keep high static capacity when at high temperature applying voltage is provided.

For the means of dealing with problems

Capacitor of the present invention is characterised in that, possesses the dielectric layer that is formed by dielectric ceramics, it is the crystal grain of principal component that described dielectric ceramics has with the barium titanate, and contain at least a rare earth element (RE) that is selected from terbium, dysprosium, holmium, erbium and the gadolinium, above-mentioned crystal grain comprises at least two kinds of crystal grain that have the difference more than the 0.1 atom % apart from the concentration of the above-mentioned rare earth element (RE) of the dark position of crystal boundary 20nm, and the crystal structure of above-mentioned crystal grain is core shell structure.

The invention effect

According to the present invention, can access the capacitor that also can keep high static capacity when at high temperature applying voltage.

Description of drawings

Among Fig. 1, (a) be the constructed profile of an example of expression capacitor of the present invention; (b) be the enlarged drawing of dielectric layer of the capacitor of pie graph 1, it is the schematic diagram of expression crystal grain and crystal boundary phase.

Among Fig. 2, (a) constitute the schematic diagram of the concentration gradient of the crystal grain of the 1st crystal group and its inner rare earth element (RE) for expression; (b) constitute the schematic diagram of the concentration gradient of the crystal grain of the 2nd crystal group and its inner rare earth element (RE) for expression.

Embodiment

Be elaborated based on the constructed profile of Fig. 1 capacitor to present embodiment.Among Fig. 1, (a) be the constructed profile of an example of expression capacitor of the present invention; (b) be the enlarged drawing of dielectric layer of the capacitor of pie graph 1, it is the schematic diagram of expression crystal grain and crystal boundary phase.Among Fig. 2, (a) constitute the schematic diagram of the concentration gradient of the crystal grain of the 1st crystal group and its inner rare earth element (RE) for expression, (b) constitute the schematic diagram of the concentration gradient of the crystal grain of the 2nd crystal group and its inner rare earth element (RE) for expression.

The capacitor of present embodiment forms outer electrode 3 at the both ends of capacitor body 1.Outer electrode 3 for example forms the alloy paste sintering of Cu or Cu and Ni.

Capacitor body 1 constitutes the dielectric layer that formed by dielectric ceramics 5 and interior electrode layer 7 are alternately laminated.Simplify the stacked state that dielectric layer 5 and interior electrode layer 7 are shown among Fig. 1, reach hundreds of layers duplexer but capacitor of the present invention is dielectric layer 5 and interior electrode layer 7.

The dielectric layer 5 that is formed by dielectric ceramics comprises crystal grain 9 and crystal boundary mutually 11, its average thickness be preferably 5 μ m following, be preferably below the 3 μ m especially, can make small-sized, the high capacity of laminated ceramic capacitor thus.In addition, from the fluctuation that reduces static capacity, the aspect consideration that makes the capacity temperature characteristic stabilisation and improve the high temperature load life-span, the average thickness of dielectric layer 5 is preferably more than the 1 μ m.

For interior electrode layer 7, even consider from the high-rise aspect that also can suppress manufacturing cost that dissolves, preferred nickel (Ni), copper base metals such as (Cu) are particularly considered from the aspect that can burn till simultaneously with the dielectric layer 5 of the capacitor that constitutes present embodiment, more preferably nickel (Ni).

In the capacitor of present embodiment, it is the crystal grain 9 of principal component that the dielectric ceramics of formation dielectric layer 5 has with the barium titanate, and contains at least a rare earth element (RE) that is selected from terbium, dysprosium, holmium, erbium and the gadolinium.Here, the dielectric ceramics that constitutes the capacitor of present embodiment refers to: will be with the barium titanate crystal grain 9 of principal component as principal crystal grain, and in the X-ray diffraction pattern that obtains carrying out X-ray diffraction from the diffracted intensity of the main peak of the barium titanate big dielectric ceramics of diffracted intensity than the main peak of the crystalline phase beyond the barium titanate.

In addition, this dielectric ceramics comprises at least two kinds of crystal grain that have the difference more than the 0.1 atom % apart from the concentration of the rare earth element (RE) of the dark position of crystal boundary 20nm.And then the crystal grain 9 that constitutes this dielectric ceramics has core shell structure.

Thus, even capacitor is in exposure at high temperature and has been applied in the state of direct voltage, also can access the little capacitor of reduction of static capacity.For example, when when under room temperature (25 ℃), not applying the static capacity that records under the condition of direct voltage and be benchmark, the rate of change of the static capacity in the time of making the direct voltage that under 125 ℃, applies about 50V (below, be called high temperature DC biasing (DCbias, direct current biasing) characteristic.) in 83%.In addition, below, when characteristic is described, replace static capacity sometimes and use relative dielectric constant.

Relative therewith, the concentration of contained rare earth element (RE) does not have difference and comprises apart from the concentration of the rare earth element (RE) of the dark position of crystal boundary 20nm not occur under crystal grain group's the situation of the difference more than the 0.1 atom % in constituting the crystal grain 9 of dielectric ceramics, when when not applying the static capacity that records under the condition of direct voltage be benchmark under room temperature (25 ℃), the rate of change of the static capacity when applying the direct voltage of about 50V under 125 ℃ is greater than 83%.

The inside that dielectric ceramics in the present embodiment is included in

crystal grain

9a, 9b is contained two kinds of

crystal grain

9a, 9b being selected from least a rare earth element (RE) in terbium, dysprosium, holmium, erbium and the gadolinium of different amounts respectively, but, for the crystal grain 9a of the 1st crystal group, the low central part that makes rare earth element (RE) be solid-solubilized in crystal grain 9a hardly of concentration owing to rare earth element contained in the crystal grain 9 (RE), therefore its central part is subjected to the domination of the few tetragonal crystalline phase of adding ingredient, can access the high dielectric ceramics of relative dielectric constant thus.

Among the crystal grain 9a of the 1st crystal group, the crystal structure that has cubic system in the solid solution of near surface adding ingredient, on the other hand, central part is tetragonal system, therefore, this crystal grain 9a have basically with tetragonal crystalline phase be core, the crystalline phase of cubic system forms the core shell structure of shell around it.Therefore, in X-ray diffraction pattern, for example, the diffraction maximum (index is 200,020,002 overlapping state) that is caused by cubic system appears between 200 diffraction maximums and 002 's diffraction maximum.The diffraction maximum of this cubic system has and 200 that are caused by tetragonal system diffraction maximum and 002 's the diffraction maximum diffracted intensity with degree.

On the other hand, for the crystal grain 9b of the 2nd crystal group, be in the state that rare earth element (RE) solid solution is put to crystal grain 9b inside very deep-seated owing to the concentration of rare earth element contained in the crystal grain 9 (RE) is high, therefore the crystal grain 9b ratio that presents the tetragonal system crystalline phase that does not contain adding ingredient tail off, the crystalline phase of the core shell structure of a large amount of adding ingredient solid solutions (in X-ray diffraction pattern, the tetragonal system crystalline phase that 200 and 002 's diffraction maximum is significantly highlighted).Its result, crystal grain 9b compares with crystal grain 9a, and defectives such as oxygen vacancies reduce, and can keep the voltage-dependent that reduces relative dielectric constant under the high relative dielectric constant state.In addition, for this dielectric ceramics, because crystal grain 9 has core shell structure, thereby dielectric loss is little, and for example, can make dielectric loss is below 5% under room temperature (25 ℃), and especially can make dielectric loss according to composition is below 2.5%.

Namely, the diffraction maximum that all occurs the diffraction maximum that caused by the 1st crystal grain with core shell structure in the dielectric ceramics of this execution mode simultaneously and caused by the 2nd crystal grain of a large amount of solid solutions of adding ingredient, here, the diffraction maximum that is caused by the 1st crystal grain 9a and the diffraction maximum that is caused by the 2nd crystal grain 9b, because the solid solubility difference of adding ingredient, thereby lattice constant is also different.

In addition, preferably, this dielectric ceramics also contains vanadium, magnesium, manganese and yttrium, and as the ratio of these adding ingredients, with respect to 100 moles of the titaniums that constitutes barium titanate, vanadium is with V ₂O ₅Be scaled 0.05～0.20 mole, yttrium with Y ₂O ₃Being scaled 0.5～2.0 mole, magnesium is scaled 1.0～3.0 moles, manganese with MgO and is scaled 0.22～0.50 mole, rare earth element (RE) with RE with MnO ₂O ₃Be scaled 0.65～2.80 mole, in addition, it is that the 1st crystal group of 0.02～0.42 atom % and the concentration of rare earth element (RE) are the 2nd crystal group of 0.45～0.70 atom % that crystal grain 9 has apart from the concentration of the rare earth element of the dark position of crystal boundary 20nm (RE), the average grain diameter that constitutes the crystal grain 9a of the 1st crystal group is 0.10～0.18 μ m, the average grain diameter that constitutes the crystal grain 9b of the 2nd crystal group is 0.2～0.5 μ m, and then, the area of the crystal grain 9a of observed formation the 1st crystal group is made as a on will the abradant surface at the dielectric ceramics of per unit area, in the time of will the area of the crystal grain 9b of observed formation the 2nd crystal group is made as b on the abradant surface of the dielectric ceramics of per unit area, b/ (a+b) be 0.4～0.7.

Thus, can access the capacitor of the reliability excellence in little and high temperature load life-span of the rate of temperature change of relative dielectric constant height, relative dielectric constant.For example, can make the relative dielectric constant under the room temperature (25 ℃) is more than 1900, make the temperature characterisitic of relative dielectric constant satisfy X7R characteristic (rate of change of relative dielectric constant is in ± 15% in-55～125 ℃ temperature range), and with respect to not applying the relative dielectric constant that records under the state (no-load condition) of direct voltage under 25 ℃, the rate of change that can make the relative dielectric constant that under the state of the voltage (direct voltage) of the per unit thickness dielectric layer that applies 5～10V under 125 ℃, records-50% with interior (near the direction of NPO (± 0%)), and then, can make applying 170 ℃, the high temperature load life-span of estimating under the condition of the direct voltage of 170V is more than 25 hours.Below, be designated as high temperature load and refer to high temperature load life-span of estimating under these conditions during the life-span.

At this moment, shown in the (a) and (b) of Fig. 2, the crystal grain 9a, the 9b that constitute this dielectric ceramics have the concentration gradient of different rare earth elements (RE) respectively, and the crystal grain 9a of the 1st crystal group is that the crystal grain 9b of 0.05～0.35 atom %/nm, the 2nd crystal group gets final product below the 0.03 atom %/nm.

Wherein, when being under the state below the 0.03 atom %/nm in the concentration gradient with the rare earth element (RE) of the crystal grain 9b of the 2nd crystal group, when making the concentration gradient of rare earth element (RE) of the crystal grain 9b of the 1st crystal group be 0.05～0.30 atom %/nm, be increased to more than 26 hours in the high temperature load life-span of capacitor.

When only having crystal grain 9a, the rate of temperature change of the relative dielectric constant when being difficult to reduce to apply direct voltage, but when making crystal grain 9b and crystal grain 9a coexistence, because crystal grain 9b just has the character of the voltage-dependent that can reduce relative dielectric constant originally, the rate of temperature change of the relative dielectric constant when therefore applying direct voltage diminishes.

In addition, in the dielectric ceramics of present embodiment, make the average grain diameter of crystal grain 9b bigger than the average grain diameter of crystal grain 9a, therefore can realize high-kization.

Its result, it is more than 1900 that the capacitor of this execution mode can make the relative dielectric constant under the room temperature (25 ℃), and, particularly with respect to not applying the relative dielectric constant that records under the state (no-load condition) of direct voltage under 25 ℃, can make state at the voltage (direct voltage) of the per unit thickness dielectric layer 5 that applies 5～10V under 125 ℃ (below, be called the high temperature load state) under the rate of change of relative dielectric constant in-50%, and, the reliability excellence in high temperature load life-span.Under this situation, the average grain diameter that constitutes the crystal grain 9b of the crystal grain 9a of the 1st crystal group of dielectric ceramics of this execution mode and the 2nd crystal group is that 0.13～0.23 μ m gets final product.

In the dielectric ceramics of present embodiment, as wherein contained rare earth element (RE), select terbium, dysprosium, holmium, erbium and gadolinium, this is because the easier solid solution of these rare earth elements (RE) is in the crystal grain 9 that is principal component in the rare earth element of the periodic table of elements with the barium titanate.And, by making these rare earth elements (RE) solid solution in crystal grain 9, and 2 kinds of

different crystal grain

9a, 9b of the concentration that in dielectric ceramics, forms rare earth element (RE), thereby can improve high temperature DC biasing characteristic, and, can improve the relative dielectric constant of dielectric ceramics, rate of temperature change and the voltage-resistent characteristic of relative dielectric constant.

The yttrium (Y) that contains in the lump with rare earth element (RE), be to be difficult to solid solution in the element of barium titanate than elements such as terbium, dysprosium, holmium, erbium and gadoliniums, utilize this point, can make the yttrium solid solution in the near surface of the crystal grain 9 of barium titanate, can control rate of temperature change and the reliability in high temperature load life-span of the relative dielectric constant under relative dielectric constant, no-load condition and the high temperature load state of dielectric ceramics like this.Under this situation, the concentration gradient of yttrium all is preferably 0.05～0.20 atom %/nm in

crystal grain

9a, 9b.

In addition, concentration and CONCENTRATION DISTRIBUTION for the rare earth element in the crystal grain 9 (RE), after the section of dielectric ceramics ground, on the image that the monitor that is attached to transmission electron microscope mirrors, described to include in the circle of about 30 crystal grain, be chosen in the circle and the crystal grain on the circumference, use the transmission electron microscope of setting up elementary analysis equipment to carry out elementary analysis.The crystal grain 9 that select this moment is as follows: utilize image to handle the area of obtaining each particle by its profile, calculate and replace with the diameter with bowlder of the same area, the diameter of the crystal grain of obtaining 9 is roughly at the crystal grain 9 of 0.08～0.60 scope.The spot size of the electron ray when analyzing is made as 0.5～2nm, and the position that analyze is made as crystal boundary 20nm apart from crystal grain 9 (± 1nm) dark position.

During the concentration of the rare earth element (RE) in calculating crystal grain 9, central part irradiation electron ray to crystal grain 9, output according to the X ray that obtains is calculated the amount of essential element contained in the crystal grain 9 as 100 atom %, obtain the wherein ratio of rare earth element (RE).Here, as main element, can list for example barium (Ba), titanium (Ti), vanadium (V), magnesium (Mg), manganese (Mn) and rare earth element (RE).

Then, when calculating the concentration gradient of rare earth element (RE), be arranged on from being positioned at the point of the roughly equally spaced position on the straight line of drawing to this center near the crystal boundary in the scope of the position at the center of central portion, by roughly 20nm and 200nm (are designated as d in the (a) and (b) of Fig. 2 deeply near crystal boundary and apart from crystal boundary _G) locate to analyze the value that obtains and obtain.At this moment, use that (concentration of the rare earth element in 0～1nm) (RE) deducts the concentration of rare earth element (RE) at the degree of depth 19～21nm and 195～205nm place respectively and the value (concentration of rare earth element) that obtains by the crystal boundary of crystal grain 9, divided by the distance of the scope of above-mentioned analysis (for example, 20nm-0nm=20nm, 200nm-0nm=200nm), obtain concentration gradient.Afterwards, each crystal grain 9 is calculated the concentration gradient of rare earth element (RE) respectively, thereby determine the crystal grain 9a of the 1st crystal group and the crystal grain 9b of the 2nd crystal group.

In addition, crystal grain 9 can be judged by the measurement result of the concentration gradient of above-mentioned rare earth element (RE) for the judgement of core shell structure.At this moment, the concentration gradient with rare earth element (RE) is that the above structure of 0.05 atom %/nm is made as core shell structure.In addition, also can be according to the X-ray diffraction pattern of pulverizing the sample that dielectric ceramics obtains, ((040) face, (400) face are overlapping by (004) face of the cubic system of the expression barium titanate that occurs between tetragonal (004) face of expression barium titanate and (400) face.) diffracted intensity identical with arbitrary diffracted intensity in expression tetragonal (400) face of barium titanate and (004) face or than its big pattern, judgement crystal grain 9 is core shell structure.

Constitute the crystal grain 9a of the 1st crystal group and constitute following the obtaining of average grain diameter separately of the crystal grain 9b of the 2nd crystal group: will the section of dielectric ceramics be ground (ion milling) and image input computer that the abradant surface that obtains mirrors in transmission electron microscope, the profile of the crystal grain that exists on this image is carried out image to be handled, obtain the area of each particle, calculate and replace to the diameter with bowlder of the same area, obtained by the mean value of 30 crystal grain of calculating.At this moment, based on from crystal grain 9, calculating the concentration of rare earth element (RE) or the result of concentration gradient before, distinguish crystal grain 9a and crystal grain 9b, obtain mean value respectively, obtain the average grain diameter of

crystal grain

9a, 9b.

In addition, the crystal grain 9a of formation the 1st crystal group that the crystal grain 9b that constitutes the 2nd crystal group comprises with respect to dielectric ceramics and constitute the area ratio of the gross area of the crystal grain 9b of the 2nd crystal group uses the data of using when calculating above-mentioned average grain diameter to calculate.

In addition, for the crystal grain 9a, the 9b that constitute dielectric ceramics, its constituent ratio b/ (a+b) had been made as 0.4～0.6 o'clock, can making the rate of temperature change of the relative dielectric constant under the high temperature load state for below-49.9%.

And then, in the capacitor of present embodiment, dielectric ceramics is contained with Y for 100 moles with respect to the titanium that constitutes barium titanate ₂O ₃Be scaled 1.0～2.0 moles yttrium, thus, can make the rate of temperature change of the relative dielectric constant under the high temperature load state less than-49.5%.

In addition, in the laminated ceramic capacitor of present embodiment, as long as in the scope that can keep desirable dielectric property, just can also contain mentioned component other composition in addition, for example, can in dielectric ceramics, the ratio with 0.5～2 quality % contain glass ingredient, other adding ingredient as the auxiliary agent that is used for improving agglutinating property.

Below, will the method for the capacitor of making present embodiment be described, but the manufacture method of following record only is an example that the present invention is not limited in this method.At first, as material powder, prepare purity and be the above barium titanate powder of 99 quality % (below, be called the BT powder.), V ₂O ₅Powder, MgO powder, MnCO ₃Powder, Y ₂O ₃Powder and be selected from Tb ₄O ₇Powder, Dy ₂O ₃Powder, Ho ₂O ₃Powder, Er ₂O ₃Powder and Gd ₂O ₃At least a powder in the powder.

Here, the average grain diameter of BT powder is preferably 0.10～0.35 μ m, is preferably 0.15～0.30 μ m especially.For the V as additive ₂O ₅Powder, MgO powder, MnCO ₃Powder, Y ₂O ₃Powder or Tb ₄O ₇Powder, Dy ₂O ₃Powder, Ho ₂O ₃Powder, Er ₂O ₃Powder and Gd ₂O ₃Powder also preferably uses these identical with the BT powder or littler than BT powder powder of average grain diameter.

Then, to use these material powders to prepare slurry, but when making the capacitor of present embodiment, from the total amount of the BT powder that is used to form dielectric ceramics, segment out the amount that is equivalent at the ratio that is burning till the crystal grain 9b that the back forms the 2nd crystal group in advance, in the BT powder that segments out, add the rare earth element (RE) of the suitable mol ratio of the ratio with the BT powder that from the oxide powder of the rare earth element (RE) that will add, also segments out, be coated with processing.Coating is handled by the BT powder of each ormal weight and oxide powder mixing back pre-burning under 450～800 ℃ temperature of rare earth element (RE) are carried out.

Then, add coating with ormal weight respectively and handle the BT powder of the oxide powder that rare earth element (RE) is arranged (hereinafter referred to as the lining powder.), the residue BT powder of the oxide powder of rare earth element (RE), oxide powder and the V of remaining rare earth element (RE) are handled in coating ₂O ₅Powder, MgO powder, MnCO ₃Powder and Y ₂O ₃Additive powders such as powder, the preparation dielectric medium powder.

Then, add special-purpose organic carrier (organic vehicle) in the dielectric medium powder for preparing cooperating as described above, the preparation ceramic size, afterwards, the skill in using a kitchen knife in cookery is scraped in use, mould is coated with method sheet material forming processes such as (die coater method) and forms ceramic green sheet.At this moment, consider that from the thin layerization that is used for making dielectric layer 5 high capacities, the aspect of keeping high-insulativity the thickness of ceramic green sheet is preferably 1～6 μ m.

Then, form the internal electrode pattern of rectangle in the interarea printing of the ceramic green sheet that obtains.Form the preferred Ni of conductor paste, Cu or their alloy powder of internal electrode pattern.

Then, will be formed with the overlapping required number of ceramic green sheet of internal electrode pattern, down not form the ceramic green sheet of internal electrode pattern so that levels is the overlapping multi-disc of mode of same piece number thereon, form laminate.At this moment, the internal electrode pattern in the laminate is at the length direction pattern that respectively staggers half.

Then, laminate is cut to clathrate, the mode of exposing with the end of internal electrode pattern forms the capacitor body formed body.Utilize such laminating method, can form internal electrode pattern in the mode of the end face that alternately exposes the capacitor body formed body after the cut-out.

Then, with the degreasing of capacitor body formed body, burn till then.Additive is to the solid solution of BT powder and lining powder and a reason of growing of crystal grain from suppress present embodiment, and firing temperature is preferably 1200～1300 ℃.

In addition, under weak reduction atmosphere, heat-treat again after burning till.This heat treatment is in order to make the dielectric ceramics oxidation again that is reduced, to make the insulation resistance that is reduced when burning till and reduces be recovered to carry out in reduction burning till under the atmosphere.From the grain growth that suppresses crystal grain 9 and the reason that improves the amount of reoxidizing, this temperature is preferably 900～1100 ℃.Thus, even can access the also little dielectric ceramics of the rate of temperature change of relative dielectric constant under the high temperature load state.

Then, the opposite end coating outer electrode paste at this capacitor body 1 carries out sintering, forms outer electrode 3.In addition, in order to improve installation, also can form electroplated film on the surface of this outer electrode 3.

Below, enumerate embodiment capacitor of the present invention is elaborated, but the present invention is not limited to following embodiment.

Embodiment

At first, as material powder, prepare BT powder, V ₂O ₅Powder, MgO powder, MnCO ₃Powder, Y ₂O ₃Powder and be selected from Tb ₄O ₇Powder, Dy ₂O ₃Powder, Ho ₂O ₃Powder, Er ₂O ₃Powder and Gd ₂O ₃The oxide powder of at least a rare earth element (RE) in the powder is (hereinafter referred to as the oxide powder of rare earth element.), above-mentioned various powder are mixed in the following order, finally be that the mode of the ratio shown in table 1, the table 2 prepares with the composition of dielectric medium powder.It is the powder of 99.9 quality % that these material powders use purity.It is the powder of 0.2 μ m that the BT powder uses average grain diameter.V ₂O ₅Powder, MgO powder, MnCO ₃Powder, Y ₂O ₃The oxide powder of powder, rare earth element uses average grain diameter to be the powder of about 0.1 μ m.The Ba/Ti of BT powder is than all being made as 1.

The oxide powder of the powder coated processing rare earth element of BT is adhered to the powder that obtains (hereinafter referred to as the lining powder in preparation.) time, respectively the amount of weighing BT powder corresponding with the ratio of crystal grain of the 2nd crystal group that forms in the dielectric ceramics in the total amount of the oxide powder of employed BT powder and rare earth element and with the oxide powder of the rare earth element of the corresponding ratio of the ratio of this BT powder that segments out, use ball mill with these powder, then, pack in the ceramic container made, carry out 500 ℃, 1 hour heat treatment.Prepare the lining powder thus.

Then, in the lining powder, add remaining BT powder, the oxide powder of remaining rare earth element, V ₂O ₅Powder, MgO powder, MnCO ₃Powder and Y ₂O ₃Powder, the preparation dielectric medium powder.

At this moment, the crystal grain of lining powder and the 2nd crystal group is corresponding and the BT powder is corresponding with the crystal grain of the 1st crystal group, and the b/ (a+b) that makes the mixing ratio of be covered powder and BT powder become table 1 compares.

Sintering aid uses SiO ₂=55, BaO=20, CaO=15, Li ₂The glass powder that O=10 (mole %) forms.The addition of glass powder is 1 mass parts with respect to 100 mass parts BT powder.

Then, use the zirconia ball of diameter 5mm, add toluene and ethanol mixed solvent as solvent, these material powders are carried out wet mixed.Add polyvinyl butyral resin and toluene and ethanol mixed solvent in the powder after wet mixed, use the zirconia ball of diameter 5mm to carry out wet mixed equally, the preparation ceramic size utilizes the scraper legal system to make the ceramic green sheet of thickness 2 μ m.

Forming a plurality of at the upper surface of this ceramic green sheet is the internal electrode pattern of the rectangle of principal component with Ni.The conductor paste that uses in the internal electrode pattern is as follows: the Ni powder adds the powder of average grain diameter 0.3 μ m, and adds BT powder 30 mass parts that are used for raw cook of conduct coexistence material with respect to 100 mass parts Ni powder.

Then, stacked 300 ceramic green sheets that are printed with internal electrode pattern, thereon below stacked 20 ceramic green sheets that do not print internal electrode pattern respectively, use extruder at 60 ℃ of temperature, pressure 10 it ⁷Carry out disposable stackedly under the condition of Pa, 10 minutes time, cut into the size of regulation, form and be laminated into body.

Programming rate with 10 ℃/h, in atmosphere, under 300 ℃, gained is laminated into body and carries out the processing of unsticking mixture, after identical programming rate heating, to be made as 300 ℃/h from 500 ℃ programming rate, burnt till under 1250 ℃ 2 hours in hydrogen-nitrogen, the cooling rate with 300 ℃/h is cooled to 1000 ℃ then, implements 4 hours heat treated (reoxidizing processing) afterwards in nitrogen atmosphere under 1000 ℃, with the cooling rate cooling of 300 ℃/h, make capacitor body.This capacitor body is of a size of the size of the model 3216 that is suitable for laminated ceramic capacitor.The average thickness of dielectric layer is 3.6 μ m, and the effective area of 1 layer of interior electrode layer is 3.54mm ²Here, effective area refers to the overlapped area of interior electrode layer that forms in the mode that the end face at the different directions of capacitor body exposes.

In addition, sample No.36, the 84th, (being not used in the material that coating is handled) rare earth element (Tb is added in the back ₄O ₇) whole amounts of oxide powder and the sample for preparing.Sample No.37, the 85th is with the rare earth element (Tb that all measures ₄O ₇) oxide powder and all amount the BT powder and prepare the lining powder, and add V therein ₂O ₅Powder, MgO powder, MnCO ₃Powder, Y ₂O ₃Powder and sintering aid and the sample that obtains.Sample No.38, the 86th is the sample that BT powder that the lining powder for preparing of the BT powder of 0.1 μ m and average grain diameter are 0.45 μ m prepares with using average grain diameter.Sample No.39, the 87th, to use average grain diameter be the powder of 0.2 μ m, the BT powder that adds as the back (in the table 1 crystal grain) corresponding with the crystal grain of the 1st crystal group uses average grain diameter to be the sample of the powder of 50nm as the BT powder for the preparation of the lining powder.Sample No.40,41,46～48,54,88,89,97～99 and 105 is 500 ℃ of samples to the programming rate of maximum temperature that changed when originally burning till, wherein, sample No.40,88 is 1000 ℃/h, sample No.41,89 is 1500 ℃/h, sample No.46,97 is 1300 ℃/h, sample No.47,98 is 150 ℃/h, and sample No.48,99 is 1900 ℃/h, and sample No.54,105 is 1100 ℃/h.

It is that the BT powder of 50nm is as the sample of the BT powder that forms the lining powder that sample No.49,100 is to use average grain diameter.

Sample No.50～53,101～104th, the sample of the calcined temperature when having changed preparation lining powder, wherein, sample No.50,101 is 450 ℃, and sample No.51,102 is 650 ℃, and sample No.52,103 is 300 ℃, and sample No.53,104 is 950 ℃.

Then, the capacitor body after burning till is carried out barreling, afterwards, be coated with the outer electrode paste that contains Cu powder and glass at the both ends of capacitor body, under 850 ℃, carry out sintering, form outer electrode., use electrolysis tumbling mill, the surface of this outer electrode is plated Ni and plating Sn successively, make the capacitor of cascade type thereafter.

＜estimate

The laminated ceramic capacitor that obtains is carried out following evaluation.Here, the evaluation for the temperature characterisitic of relative dielectric constant, dielectric loss, static capacity all is made as 10 with the sample number, obtains its mean value.

(1) relative dielectric constant and high temperature DC biasing characteristic

Under the condition determination of 25 ℃ of temperature, frequency 1.0kHz, mensuration voltage 1Vrms, measure static capacity, by the static capacity that obtains, convert and obtain relative dielectric constant based on the dielectric constant of the effective area sum of all layers of dielectric layer thickness, interior electrode layer and vacuum.

(2) dielectric loss

Under the condition identical with static capacity, measure.

(3) temperature characterisitic of relative dielectric constant

Measure static capacity, the rate of change of the static capacity when obtaining with respect to 25 ℃ down for 125 ℃ in temperature.In addition, apply the direct voltage of 25V and 50V, the static capacity under measuring 125 ℃ is obtained the rate of change with respect to the static capacity 25 ℃ time the under non-loaded (DC=0V) state.

(4) high temperature load test

170 ℃ of temperature, apply under the condition of voltage 170V and carry out.Sample number in the high temperature load test be 30 on each sample, and studying the time that probability of malfunction reaches at 50% o'clock is the mean down time.

(5) concentration, concentration gradient and the crystal grain of the rare earth element in the crystal grain (RE) are than the mensuration of the average grain diameter of (b/ (a+b)) and crystal grain

CONCENTRATION DISTRIBUTION for the rare earth element in the crystal grain (RE), after the section of dielectric ceramics ground, on the image that the monitor that is attached to transmission electron microscope mirrors, described to include in the circle of about 30 crystal grain, be chosen in the circle and the crystal grain on the circumference, use the transmission electron microscope of setting up elementary analysis equipment to carry out elementary analysis.In addition, in the present embodiment, will include the circle of about 30 crystal grain in as unit are.The crystal grain that select this moment is as follows: utilize image to handle the area of obtaining each particle by its profile, calculate and replace to the diameter with bowlder of the same area, the diameter of the crystal grain of obtaining is at the crystal grain of 0.08～0.60 scope roughly.The spot size of the electron ray when analyzing is made as 0.5～2nm, and the position that analyze is for apart from the crystal boundary 20nm of crystal grain (± 1nm) dark position.Particularly, when calculating the concentration of the rare earth element (RE) in the crystal grain, central part irradiation electron ray to crystal grain, output according to the X ray that obtains is calculated the amount of essential element contained in the crystal grain (barium (Ba), titanium (Ti), vanadium (V), magnesium (Mg), manganese (Mn) and rare earth element (RE)) as 100 atom %, obtain the wherein ratio of rare earth element (RE).

Then, when calculating the concentration gradient of rare earth element (RE), the position of analyzing is made as from being positioned at the point of the roughly equally spaced position on the straight line of drawing to this center near the crystal boundary of crystal grain in the scope of the position at the center of central portion, by roughly 20nm and 200nm depths are analyzed the value that obtains and obtained near crystal boundary and apart from crystal boundary.At this moment, use that (concentration of the rare earth element in 0～1nm) (RE) deducts the concentration of rare earth element (RE) at the degree of depth 19～21nm and 195～205nm place respectively and the value (concentration of rare earth element) that obtains by the crystal boundary of crystal grain, divided by the distance of the scope of above-mentioned analysis (for example, 20nm-0nm=20nm, 200nm-0nm=200nm), obtain concentration gradient.Afterwards, each crystal grain is calculated the concentration gradient of rare earth element (RE) respectively, thereby determine the crystal grain 9a of the 1st crystal group and the crystal grain 9b of the 2nd crystal group.Position, 5 place to each sample is carried out this analysis respectively, obtains mean value.

In such analysis, the crystal grain that the concentration gradient of rare earth element (RE) is shown as 0.05～0.20 atom % is as " constituting the crystal grain of the 1st crystal group ", and the concentration gradient of rare earth element (RE) is shown as the following crystal grain of 0.03 atom % as " constituting the crystal grain of the 2nd crystal group ".In addition, the sample that obtains pulverizing dielectric ceramics carries out X-ray diffraction, judges core shell structure by diffraction pattern.At this moment, crystal grain is that the situation of core shell structure refers to: ((040) face, (400) face are overlapping for (004) face of the cubic system of the expression barium titanate that occurs between tetragonal (004) face of expression barium titanate and (400) face.) diffracted intensity identical or bigger than it with arbitrary diffracted intensity in expression tetragonal (400) face of barium titanate and (004) face.

Constitute the crystal grain of the 1st crystal group and constitute following the obtaining of average grain diameter separately of the crystal grain of the 2nd crystal group: will the section of dielectric ceramics be ground (ion milling) and image input computer that the abradant surface that obtains mirrors in transmission electron microscope, the profile of the crystal grain that exists on this image is carried out image to be handled, obtain the area of each particle, calculate and replace to the diameter with bowlder of the same area, obtained by the mean value of 30 crystal grain of calculating.At this moment, based on the result of the concentration gradient that from crystal grain, calculates rare earth element (RE) before, distinguish the crystal grain of the 1st crystal group and the crystal grain of the 2nd crystal group, obtain mean value respectively, obtain the average grain diameter of crystal grain.

In the dielectric ceramics, the crystal grain that constitutes the 2nd crystal group with respect to the crystal grain that constitutes the 1st crystal group and constitute the 2nd crystal group crystal grain the gross area area ratio b/ (a+b) (wherein, a represents to constitute the area of the crystal grain 9a of the 1st crystal group, b represents to constitute the area of the crystal grain 9b of the 2nd crystal group), by the average grain diameter separately of the crystal grain of the crystal grain that above-mentioned about 30 crystal grain is calculated the 1st crystal group and the 2nd crystal group and the data that obtain calculate.The b/ of the sample that makes (a+b) is than the mixing ratio that all is equivalent to BT powder and lining powder.

(6) composition analysis of sample

The sintered body of gained is that the composition analysis of sample utilizes icp analysis and atomic absorption spectroscopy to carry out.At this moment, after the dielectric ceramics that obtains mixed with boric acid and sodium carbonate and making its fusion, be dissolved in the hydrochloric acid, at first, utilize atomic absorption spectroscopy to carry out the qualitative analysis of element contained in the dielectric ceramics, then, to each element of identifying with the titer dilution after, as standard specimen, carry out quantitatively with the ICP emission spectrographic analysis.In addition, the valence mumber of establishing each element is the valence mumber shown in the periodic table of elements, obtains the oxygen amount.In addition, manganese is converted into MnO and obtains.Analyzing the result who obtains is: in the sample, the composition of dielectric layer is all formed consistent with allotment arbitrarily.Allotment form and characteristic the results are shown in table 1～4.

[table 1]

[table 2]

[table 3]

[table 4]

By table 1,2,3 and 4 result as can be known, be coated on that BT powder, back add remainder and in sample No.1～35,38～83 and 86～105 that make in the part with the oxide powder of rare earth element, the concentration that dielectric ceramics comprises rare earth element has the crystal grain of the above difference of 0.1 atom %, and the high temperature biasing characteristic when applying 50V under 125 ℃ is in 83%.

In addition, in sample No.1～3,6,7,10,13,14,17,19,20,23,24,27,28,31～35,40,43,44～47,50,51,54,55,56,59,60,63,66,67,70,72,73,76,77,80,81,88,91～98,101, in 102 and 105, the relative dielectric constant of dielectric ceramics under room temperature (25 ℃) is more than 1900, the temperature characterisitic of static capacity satisfies the X7R characteristic, and the static capacity that records with respect to the state (no-load condition) that under 25 ℃, does not apply direct voltage, can make the rate of change of the static capacity that under the state of the direct voltage that under 125 ℃ dielectric layer is applied 25V, records (hereinafter referred to as at 125 ℃, high temperature DC biasing characteristic under the 25V)-50% with interior (near the direction of NPO (± 0%)), and then, at 170 ℃, applying the high temperature load life-span of estimating under the condition of direct voltage of 170V is more than 25 hours.

Wherein, be that the concentration gradient of the rare earth element (RE) of the crystal grain of the 1st crystal group under the state below the 0.03 atom %/nm is sample (sample No.1～3 of 0.05～0.30 atom %/nm in the concentration gradient of the rare earth element (RE) of the crystal grain of the 2nd crystal group, 6,7,10,13,14,17,19,20,23,24,27,28,31～35,40,43,44,45,47,50,51,54,55,56,59,60,63,66,67,70,72,73,76,77,80,81,88,91～96,98,101,102 and 105) in, the high temperature load life-span of capacitor is more than 26 hours.

In addition, the constituent ratio b/ (a+b) that constitutes crystal grain 9a, the 9b of dielectric ceramics is among 0.4～0.6 the sample No.1,2,6,7,10,13,14,17,19,20,23,24,28,31～35,40,43,44～47,50,51,54,55,56,59,60,63,66,67,70,72,73,76,77,81,88,91～96,98,101,102 and 105, and the high temperature DC biasing characteristic under 125 ℃, 25V is in-49.9%.

And then in the composition of dielectric ceramics, with respect to 100 moles of the titaniums that constitutes barium titanate, yttrium is with Y ₂O ₃Be scaled among 1.0～2.0 moles the sample No.1,2,6,7,10,13,14,17,19,20,23,24,27,28,31～35,40,43,44～47,50,51,54,55,59,60,63,66,67,70,72,73,76,77,81,88,91～96,98,101,102 and 105, the high temperature DC biasing characteristic under 125 ℃, 25V is less than-49.5%.

In addition, be basic composition, when only replacing Dy, Ho as the rare earth element beyond the Tb, Yb, Gd, the Er of half mole, also obtain the result identical with sample No.1 with sample No.1.

Relative therewith, handle or disposable interpolation all amount and the sample No.36,37,84 and 85 that makes for lining whole amounts of the oxide powder of rare earth element are disposable, the concentration of the rare earth element of the crystal grain of formation dielectric ceramics is below the 0.05 atom %, do not have above poor of 0.1 atom %, the high temperature DC biasing characteristic when applying 50V under 125 ℃ is greater than-83%.

In addition, except the sample shown in the table, the sample No.3 in the his-and-hers watches 1,3, using average grain diameter is the BT powder of 0.1 μ m, makes V ₂O ₅Be 0.15 mole, in addition, the sample of making capacitor that uses the same method is estimated.At this moment, the X-ray diffraction pattern that obtains by pulverizing dielectric ceramics as can be known, ((040) face, (400) face are overlapping for (004) face of the cubic system of the expression barium titanate that occurs between tetragonal (004) face of expression barium titanate and (400) face.) diffracted intensity all littler than arbitrary the diffracted intensity of expression tetragonal (400) face of barium titanate and (004) face.In addition, the concentration gradient of the rare earth element in the crystal grain (Tb) also is 0.02 atom %/nm, is in the state of a large amount of solid solutions of rare earth element in crystal grain, does not have core shell structure.The high temperature DC biasing characteristic of this sample under the condition that applies 50V under 125 ℃ for-86%, dielectric loss is up to 6.7%.

For other compositions, do not satisfy dielectric ceramics for the concentration apart from the rare earth element (RE) of the dark position of crystal boundary 20nm have the two or more crystal grain of the difference more than the 0.1 atom % and crystal structure be core shell structure the two the time, the high temperature DC biasing characteristic under the condition that applies 50V under 125 ℃ in minus value side greater than-83%.

Symbol description

1 capacitor body

3 outer electrodes

5 dielectric layers

7 interior electrode layers

11 crystal boundary phases

9 crystal grain

9a constitutes the crystal grain of the 1st crystal group

9b constitutes the crystal grain of the 2nd crystal group

Claims

1. capacitor, it is characterized in that, possesses the dielectric layer that is formed by dielectric ceramics, it is the crystal grain of principal component that described dielectric ceramics has with the barium titanate, and contain at least a rare earth element (RE) that is selected from terbium, dysprosium, holmium, erbium and the gadolinium, described crystal grain comprises at least two kinds of crystal grain that have the difference more than the 0.1 atom % apart from the concentration of the described rare earth element (RE) of the dark position of crystal boundary 20nm, and the crystal structure of described crystal grain is core shell structure.

2. capacitor according to claim 1 is characterized in that, described dielectric ceramics contains vanadium, magnesium, manganese and yttrium,

With respect to 100 moles of the titaniums that constitutes described barium titanate,

Contain with V ₂O ₅Be scaled 0.05～0.20 mole described vanadium,

With Y ₂O ₃Be scaled 0.5～2.0 mole described yttrium,

With MgO be scaled 1.0～3.0 moles described magnesium,

With MnO be scaled 0.22～0.50 mole described manganese and

With RE ₂O ₃Be scaled 0.65～2.80 mole described rare earth element (RE),

It is that the 1st crystal group of 0.02～0.42 atom % and the concentration of described rare earth element (RE) are the 2nd crystal group of 0.45～0.70 atom % that described crystal grain comprises apart from the concentration of the described rare earth element (RE) of the dark position of crystal boundary 20nm,

The average grain diameter that constitutes the crystal grain of described the 1st crystal group is that 0.10～0.18 μ m, the average grain diameter that constitutes the crystal grain of described the 2nd crystal group are 0.2～0.5 μ m, and,

On will the abradant surface at the described dielectric ceramics of per unit area the area of the crystal grain of described the 1st crystal group of observed formation be made as a, will the area of the crystal grain of described the 2nd crystal group of observed formation be made as b on the abradant surface of the described dielectric ceramics of per unit area the time, b/ (a+b) is 0.4～0.7.

3. capacitor according to claim 1 and 2, it is characterized in that, the concentration gradient that the concentration that the crystal grain of the crystal grain of described the 1st crystal group and described the 2nd crystal group all has a described rare earth element (RE) reduces to inside from described crystal boundary, the described concentration gradient in the dark scope of crystal boundary 20nm of the crystal grain of described the 1st crystal group is 0.05～0.30 atom %/nm, and the concentration gradient of the described rare earth element (RE) in the dark scope of crystal boundary 200nm of the crystal grain of described the 2nd crystal group is below the 0.03 atom %/nm.

4. according to each described capacitor in the claim 1～3, it is characterized in that described b/ (a+b) is 0.4～0.6.

5. capacitor according to claim 3 is characterized in that, described yttrium is with Y ₂O ₃Be scaled 1.0～2.0 moles.