CN101823876B - Ceramic material for temperature stabilization type multilayer ceramic capacitor and preparation method thereof - Google Patents

Abstract

The invention relates to a dielectric material used for a high-temperature and high-stability multilayer ceramic capacitor, which is prepared by the method comprising the following steps: (1) evenly mixing K2CO3, Na2CO3 and Nb2O5, and presintering at the temperature of 600 DEG C and carrying out heat preservation for 2 hours to synthetize (K0.5Na0.5)NbO3 to obtain a (K0.5Na0.5)NbO3 powder; (2) mixing BaTiO3, Bi2O3, Sc2O3, (K0.5Na0.5)NbO3, PbO and TiO2 and then adding the mixture to an absolute ethyl alcohol solvent, carrying out ballmilling and drying to obtain a raw material powder; and (3) adding a binder to the raw material powder for pelleting and ageing; pressing into wafers and presintering at the temperature of 600 DEG C for 2 hours to obtain a ceramic material for the temperature stabilization type multilayer ceramic capacitor. The ceramic material for the temperature stabilization type multilayer ceramic capacitor prepared by the invention has big dielectric constant, low dielectric loss, very good temperature stability and low price and has two advantages that: 1. the range of the temperature stability is wide; 2. the ceramic material can be sintered at the intermediate temperature, is suitable for being jointly sintered with low-price metals and is used for preparing materials for the high-temperature and high-stability multilayer ceramic capacitor.

Description

Be used for temperature-stable multilayer ceramic capacitor porcelain and preparation method thereof

Technical field:

The invention belongs to the multi-layer ceramic capacitor material technical field, particularly dielectric materials of a kind of laminated ceramic capacitor for high temp. high stable and preparation method thereof.

Background technology:

Along with the fast development of information technology and electronic technology, also more and more higher to the requirement of electronics.The miniaturization of electronics.Chip type and lightness are the inexorable trends of development.The components and parts of electronics will have smaller size smaller and weight accordingly, and laminated ceramic capacitor (being called for short MLCC) needs to arise at the historic moment because of these.According to the international EIA of Electronic Industries Association USA standard, MLCC is take 25 ℃ capacitance as benchmark, in the scope of temperature-55～200 ℃, and rate of change of capacitance≤± 15%, dielectric loss≤2.5%.The core material of MLCC is by BaTiO ₃The R (Δ C/C≤± 15%) that the base ferroelectric ceramic(s) consists of is porcelain.

Because the sintering characteristic of barium titanate ceramics itself, when using barium titanate ceramics as main raw, its sintering temperature is higher, generally greater than 1300 ℃.And laminated ceramic capacitor requires material and interior electrode to burn altogether, and under common burning temperature, requirement not with interior electrode generation chemical reaction, interior electrode does not melt, and ensures good electroconductibility.This so that the selection of laminated ceramic capacitor inner electrode be restricted.During former laminated ceramic capacitor was produced, the precious metal of normal operation higher melt (such as Pt, Au, Pd metal or its alloy etc.) was as interior electrode.But, use these precious metals, improved greatly the manufacturing cost of electrical condenser.A lot of document announcements, the precious metal cost is 30～70% of laminated ceramic capacitor production cost.US Patent No. 007061748 report uses barium titanate based ceramic as main raw material, and sintering range is at 1200～1320 ℃.The interior electrode that uses is Pt, Au, Pd, Ag, Rh, Ru, a kind of or alloy among the Ir.Consider from production cost, this is worthless.Use cheap metal (such as Ni, Fe, Co, Cu etc.) greatly to reduce production costs, enhance competitiveness.But, since Ni, Fe, Co, the fusing point of the cheap metals such as Cu is lower, when burning altogether with stupalith, need to carry out sintering under middle cold condition.So, want to use cheap metal as inner electrode, best way is to reduce the sintering temperature of pottery.But, add too much low-melting additive, certainly will reduce the dielectric properties of barium titanate based ceramic.

Now widely used X7R porcelain can only using below+125 ℃, can't satisfy the stability requirement of higher temperature dielectric properties.When under higher temperature, using, its rate of change of capacitance will be far longer than ± 15% requirement.Therefore the use of laminated ceramic capacitor is very restricted.Exploitation has higher use temperature and the more much higher layer of job stability ceramic capacitor material is necessary.In the application of the special dimensions such as aerospace, automotive industry, military mobile communication, require its working temperature upper limit to bring up to 200 ℃ nearly, so the MLCC porcelain that the research and development working temperature is higher, temperature range is wider is the emphasis of studying both at home and abroad.

Summary of the invention:

The purpose of this invention is to provide a kind of intermediate sintering temperature performance that has, high stability multilayer ceramic capacitor ceramics (dielectric materials) of wide temperature range and preparation method thereof.This porcelain has high-k, low-loss, and high resistivity have simultaneously good stability, and preparation technology is simple.

Realize the technical scheme of the object of the invention:

A kind of for the temperature-stable multilayer ceramic capacitor porcelain, made by laxative remedy:

1), synthetic: according to K ₂CO ₃: Na ₂CO ₃: Nb ₂O ₅=1.03: 1.03: 2 mol ratio ratio mixes, at 2 hours synthetic (K of 600 ℃ of lower pre-burning insulations _0.5Na _0.5) NbO ₃Obtain (K _0.5Na _0.5) NbO ₃Powder, wherein K ₂CO ₃, Na ₂CO ₃Under 80 ℃ dry 24 hours in advance; Because K ₂CO ₃, Na ₂CO ₃Volatile in the time of 900 ℃, so need excessive interpolation 3mol% to offset volatile quantity;

2), with BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, (K _0.5Na _0.5) NbO ₃, PbO and TiO ₂According to (1-x): 0.05: 0.05: 0.2: x: add in the anhydrous ethanol solvent after the molar ratio of x mixes, mixing and ball milling 24 hours is dried to get material powder; X=0.03～0.12 wherein;

3), add the polyvinyl alcohol adhesive granulation with the 2.5wt% concentration of distilled water configuration in the material powder of gained, ageing is 24 hours in air; The powder of granulation is depressed to the disk of diameter 12 ± 2mm, thickness 1.5 ± 2mm at the pressure of 190～210MPa; The disk that is pressed into was 600 ℃ of lower pre-burnings 2 hours; Namely obtain for the temperature-stable multilayer ceramic capacitor porcelain.

Described BaTiO ₃, Bi ₂O ₃And Sc ₂O ₃Grain-size respectively below 1 μ m.

Above-mentioned BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, K ₂CO ₃, Na ₂CO ₃, Nb ₂O ₅, PbO and TiO ₂Purity is all greater than 99%.

The present invention preparation be used for the temperature-stable multilayer ceramic capacitor porcelain, has high-k, low dielectric loss, well temperature stability, material price is cheap, and has two large advantages: the one, have temperature stability scope wide (55～200 ℃); The 2nd, can sintering under middle temperature, be suitable for carrying out common sintering with the metal of cheapness, for the preparation of the multi-layer ceramic capacitor material of high-temperature stability.

Description of drawings:

Fig. 1 is the temperature variant curve of temperature coefficient of capacitance of the embodiment of the invention 1 sample;

Fig. 2 is the temperature variant curve of temperature coefficient of capacitance of the embodiment of the invention 2 samples;

Fig. 3 is the temperature variant curve of temperature coefficient of capacitance of the embodiment of the invention 3 samples;

Fig. 4 is the temperature variant curve of temperature coefficient of capacitance of the embodiment of the invention 4 samples.

Embodiment:

All samples all adopts the solid phase method preparation, at first prepares (K according to stoichiometric ratio _0.5Na _0.5) NbO ₃Powder, 800 ℃ temperature lower calcinations 10 hours, begin to take shape required ceramic phase.Stoichiometric ratio according to different ingredients prepares powder again,, dries after 24 hours with the planetary ball mill powder.Add the PVA binding agent granulation of 2.5wt% in the powder of gained, ageing is 24 hours in air.The powder of granulation is depressed to disk about diameter 12mm, thickness 1.5mm at the pressure about 200MPa.The disk that is pressed into is got rid of PVA glue 600 ℃ of lower pre-burnings 2 hours.Subsequently, ceramic plate sintering 2～10 hours under differing temps is to prepare fine and close ceramics sample.The sample segment that sintering obtains is used for performance test.Owing to being the cylindric of rule behind the sample sintering, can carry out with vernier callipers the measurement of diameter and the thickness of ceramics sample, thereby calculate the volume of ceramics sample, further according to the quality of pottery, can calculate the density of ceramic block.Generally speaking, there is a finest and close temperature of sintering in each component.In all experiments, obtain the optimum density point by the sintering temperature that changes pottery, the sample that various assays adopt in the following experiment all is to obtain under the temperature of sintering optimum density.It should be noted that, when the batching of reality, because yellow soda ash, salt of wormwood, plumbous oxide and bismuth oxide larger boiling characteristics at high temperature, it is excessive also will to add when reality is prepared burden, wherein yellow soda ash, the excessive 3%mol of salt of wormwood, the excessive 2%mol of plumbous oxide and bismuth oxide.When final sintering, the ceramic plate bottom places that some are alumina powder jointed, and purpose is to avoid ceramic plate in the sintering process and substrate bonding together.

Utilize respectively Archimedes's drainage to measure its volume density to the finished product ceramic plate; Adopt the X-ray diffraction technology to carry out the Phase Structure Analysis of material; Adopt SEM to observe the features such as pattern, composition synthetic body orientation of its surface and section; Specific inductivity and the loss TEMPERATURE SPECTROSCOPY of the test system and test sample that the TH2818 that use is produced with favour company and intelligent temperature controller form, the temperature range of test is-55～200 ℃, heat-up rate is 2～3 ℃/min, test frequency carries out the calculating of dielectric constant at 10kHz～300kHz according to following formula:

${\mathrm{\ϵ}}_r=\frac{4\mathrm{Ct}}{\mathrm{\π}{\mathrm{\ϵ}}_0{d}^2}$

In the formula, C is the electric capacity of test, and t is thickness of sample, permittivity of vacuum ε ₀=8.854 * 10 ^-12Fm ^-1Ferroelectric hysteresis loop and resistivity under the Precision Workstation test ceramics sample normal temperature of employing U.S. Radiant company, the Model 609A high-voltage power supply of U.S. Trek company applies external voltage, resistivity measurement adopts the drain current test method in the above-mentioned electrical performance testing equipment, carries out under the 100V volts DS.

Embodiment 1:

According to batching mode (1-x) BaTiO ₃-0.1BiScO ₃-0.2 (K _0.5Na _0.5) NbO _3-xPbTiO ₃, first K ₂CO ₃, Na ₂CO ₃Under 80 ℃ dry 24 hours in advance, again according to BaTiO ₃: PbTiO ₃=0.67: 0.03 molar ratio ingredient.Described main component BaTiO ₃The grain-size of raw material is below 1 μ m; In the porcelain ancillary component with purity greater than 99% Bi ₂O ₃, Sc ₂O ₃, K ₂CO ₃, Na ₂CO ₃, Nb ₂O ₅, PbO and TiO ₂Be reactant feed; Wherein said K ₂CO ₃, Na ₂CO ₃And Nb ₂O ₅According to the preheating of 1.03: 1.03: 2 mol ratio ratios by 600 ℃ of lower insulation 2h, synthesize (K _0.5Na _0.5) NbO ₃With material powder BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, (K _0.5Na _0.5) NbO ₃, PbO and TiO ₂Mix, ball milling, then dry, after sieving, add binding agent, binding agent employing mass concentration is 5% polyvinyl alcohol (PVA) solution, and dosage is 0.25% of powder total mass, be a granulated into single-size, compression moulding under 200MPa pressure, making the disk diameter is 12 millimeters, thickness is 1 millimeter.Disk falls the PVA binding agent 600 ℃ of lower calcinings, and then 1140～1200 ℃ of sintering temperatures, sintering time is 2～10 hours, and heat-up rate is 3 ℃/minute.The ceramic disks of burning till is through surface finish, and silver ink firing is measured its dielectric properties.The ceramics sample dielectric properties parameter that obtains sees Table 1.

Fig. 1 is the temperature variant curve of temperature coefficient of capacitance of embodiment 1 sample; As can be seen from the figure, in-55～200 ℃ of temperature ranges, electric capacity variation with temperature rate has good temperature stability in ± 15%, and up and down two dielectrics of the velocity of variation of distance ± 15% also have a very wide segment distance.

The dielectric properties parameter of the ceramics sample of table 1 embodiment 1 preparation

Embodiment 2:

According to batching mode (1-x) BaTiO ₃-0.1BiScO ₃-0.2 (K _0.5Na _0.5) NbO ₃-xPbTiO ₃,, first K ₂CO ₃, Na ₂CO ₃Under 80 ℃ dry 24 hours in advance, again according to BaTiO ₃: PbTiO ₃=0.64: 0.06 molar ratio ingredient.Described main component BaTiO ₃The grain-size of raw material is less than 1 μ m; In the porcelain ancillary component with purity greater than 99% Bi ₂O ₃, Sc ₂O ₃, K ₂CO ₃, Na ₂CO ₃, Nb ₂O ₅, PbO and TiO ₂Be reactant feed; Wherein said K ₂CO ₃, Na ₂CO ₃And Nb ₂O ₅According to the preheating of 1.03: 1.03: 2 mol ratio ratios by 600 ℃ of lower insulation 2h, synthesize (K _0.5Na _0.5) NbO ₃With material powder BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, (K _0.5Na _0.5) NbO ₃, PbO and TiO ₂Mix, ball milling, then dry, after sieving, add binding agent, binding agent employing mass concentration is 5% polyvinyl alcohol (PVA) solution, and dosage is 0.25% of powder total mass, be a granulated into single-size, compression moulding under the pressure of the 200MPa left and right sides, making the disk diameter is 12 millimeter, thickness is 1 millimeter.Disk falls the PVA binding agent 600 ℃ of lower calcinings, and then 1140～1200 ℃ of sintering temperatures, sintering time is 2～10 hours, and heat-up rate is 3 ℃/minute.The ceramic disks of burning till is through surface finish, and silver ink firing is measured its dielectric properties.The ceramics sample dielectric properties parameter that obtains sees Table 2.

Fig. 2 is the temperature variant curve of temperature coefficient of capacitance of embodiment 2 samples; As can be seen from the figure, in-55～200 ℃ of temperature ranges, electric capacity variation with temperature rate all in ± 15%, has good temperature stability, and up and down two dielectrics of distance ± 15% velocity of variation also have a segment distance, and its specific inductivity is along with PbTiO ₃Adding improve.

The dielectric properties parameter of the ceramics sample of table 2 embodiment 2 preparations

Embodiment 3:

According to batching mode (1-x) BaTiO ₃-0.1BiScO ₃-0.2 (K _0.5Na _0.5) NbO ₃-xPbTiO ₃, first K ₂CO ₃, Na ₂CO ₃Under 80 ℃ dry 24 hours in advance, again according to BaTiO ₃: PbTiO ₃=0.61: 0.09 molar ratio ingredient.Described main component BaTiO ₃The grain-size of raw material is less than 1 μ m; In the porcelain ancillary component with purity greater than 99% Bi ₂O ₃, Sc ₂O ₃, K ₂CO ₃, Na ₂CO ₃, Nb ₂O ₅, PbO and TiO ₂Be reactant feed; Wherein said K ₂CO ₃, Na ₂CO ₃And Nb ₂O ₅According to the preheating of 1.03: 1.03: 2 mol ratio ratios by 600 ℃ of lower insulation 2h, synthesize (K _0.5Na _0.5) NbO ₃With material powder BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, (K _0.5Na _0.5) NbO ₃, PbO and TiO ₂Mix, ball milling, then dry, after sieving, add binding agent, binding agent employing mass concentration is 5% polyvinyl alcohol (PVA) solution, and dosage is 0.25% of powder total mass, be a granulated into single-size, lower compression moulding about 200MPa pressure, making the disk diameter is 12 millimeter, thickness is 1 millimeter.Disk falls the PVA binding agent 600 ℃ of lower calcinings, and then 1140～1200 ℃ of sintering temperatures, sintering time is 2～10 hours, and heat-up rate is 3 ℃/minute.The ceramic disks of burning till is through surface finish, and silver ink firing is measured its dielectric properties.The ceramics sample dielectric properties parameter that obtains sees Table 3.

Fig. 3 is the temperature variant curve of temperature coefficient of capacitance of embodiment 3 samples; As can be seen from the figure, in-55～200 ℃ of temperature ranges, electric capacity variation with temperature rate is in ± 15%, good temperature stability is arranged, basically join with rolling off the production line of velocity of variation-15%, with the in addition segment distance of reaching the standard grade of velocity of variation 15%, along with PbTiO ₃Continuation add, its room temperature dielectric constant has 875.

The dielectric properties parameter of the ceramics sample of table 3 embodiment 3 preparations

Embodiment 4:

According to batching mode (1-x) BaTiO ₃-0.1BiScO ₃-0.2 (K _0.5Na _0.5) NbO ₃-xPbTiO ₃, first K ₂CO ₃, Na ₂CO ₃Under 80 ℃ dry 24 hours in advance, again according to BaTiO ₃: PbTiO ₃=0.58: 0.12 molar ratio ingredient.Described main component BaTiO ₃The grain-size of raw material is less than 1 μ m; In the porcelain ancillary component with purity greater than 99% Bi ₂O ₃, Sc ₂O ₃, K ₂CO ₃, Na ₂CO ₃, Nb ₂O ₅, PbO and TiO ₂Be reactant feed; Wherein said K ₂CO ₃, Na ₂CO ₃And Nb ₂O ₅According to the preheating of 1.03: 1.03: 2 mol ratio ratios by 600 ℃ of lower insulation 2h, synthesize (K _0.5Na _0.5) NbO ₃With material powder BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, (K _0.5Na _0.5) NbO ₃, PbO and TiO ₂Mix, ball milling, then dry, after sieving, add binding agent, binding agent employing mass concentration is 5% polyvinyl alcohol (PVA) solution, and dosage is 0.25% of powder total mass, be a granulated into single-size, compression moulding under the pressure of the 200MPa left and right sides, making the disk diameter is 12 millimeter, thickness is 1 millimeter.Disk falls the PVA binding agent 600 ℃ of lower calcinings, and then 1140～1200 ℃ of sintering temperatures, sintering time is 2～10 hours, and heat-up rate is 3 ℃/minute.The ceramic disks of burning till is through surface finish, and silver ink firing is measured its dielectric properties.The ceramics sample dielectric properties parameter that obtains sees Table 4.

Fig. 4 is the temperature variant curve of temperature coefficient of capacitance of embodiment 4 samples; As can be seen from the figure, in-55～200 ℃ of temperature ranges, electric capacity variation with temperature rate exceeds ± 15%, and requirement that can not satisfied temperature stability is so be difficult for too much adding PbTiO in body series ₃, example three has been the best composition prescription.

The dielectric properties parameter of the ceramics sample of table 4 embodiment 4 preparations

Claims (6)

1. one kind is used for the temperature-stable multilayer ceramic capacitor porcelain, is made by laxative remedy:

1), synthetic (K _0.5Na _0.5) NbO ₃Powder: with K ₂CO ₃, Na ₂CO ₃And Nb ₂O ₅Mol ratio ratio according to 1.03: 1.03: 2 mixes, and obtains (K in 2 hours 600 ℃ of lower pre-burning insulations _0.5Na _0.5) NbO ₃Powder, wherein K ₂CO ₃And Na ₂CO ₃Under 80 ℃, distinguish in advance dry 24 hours;

2), with BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, (K _0.5Na _0.5) NbO ₃, PbO and TiO ₂According to (1-x): 0.05: 0.05: 0.2: x: add in the anhydrous ethanol solvent after the molar ratio of x mixes, mixing and ball milling 24 hours is dried to get material powder; X=0.03～0.12 wherein;

3), add the polyvinyl alcohol adhesive granulation with the 2.5wt% concentration of distilled water configuration in the material powder of gained, ageing is 24 hours in air; The powder of granulation is depressed to the disk of diameter 12 ± 2mm, thickness 1.5mm at the pressure of 190～210MPa; The disk that is pressed into was 600 ℃ of lower pre-burnings 2 hours; Namely obtain for the temperature-stable multilayer ceramic capacitor porcelain.

2. described for the temperature-stable multilayer ceramic capacitor porcelain according to claim 1, it is characterized in that: described BaTiO ₃, Bi ₂O ₃And Sc ₂O ₃Grain-size respectively below 1 μ m.

3. described for the temperature-stable multilayer ceramic capacitor porcelain according to claim 1 and 2, it is characterized in that: above-mentioned BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, K ₂CO ₃, Na ₂CO ₃, Nb ₂O ₅, PbO and TiO ₂Purity is all greater than 99%.

4. the described preparation method for the temperature-stable multilayer ceramic capacitor porcelain of claim 1 comprises:

1), synthetic (K _0.5Na _0.5) NbO ₃: with K ₂CO ₃, Na ₂CO ₃And Nb ₂O ₅Mol ratio ratio according to 1.03: 1.03: 2 mixes, and obtains (K in 2 hours 600 ℃ of lower pre-burning insulations _0.5Na _0.5) NbO ₃Powder, wherein K ₂CO ₃, Na ₂CO ₃Under 80 ℃ dry 24 hours in advance,

2), with BaTiO ₃, Bi ₂O ₃, Sc ₂O ₃, (K _0.5Na _0.5) NbO ₃, PbO and TiO ₂According to (1-x): 0.05: 0.05: 0.2: x: add in the anhydrous ethanol solvent after the molar ratio of x mixes, mixing and ball milling 24 hours is dried to get material powder; X=0.03～0.12 wherein;

3), add the polyvinyl alcohol adhesive granulation with the 2.5wt% concentration of distilled water configuration in the material powder of gained, ageing is 24 hours in air; The powder of granulation is depressed to the disk of diameter 12 ± 2mm, thickness 1.5mm at the pressure of 190～210MPa; The disk that is pressed into was 600 ℃ of lower pre-burnings 2 hours; Namely obtain for the temperature-stable multilayer ceramic capacitor porcelain.

5. method according to claim 4 is characterized in that: described BaTiO ₃, Bi ₂O ₃And Sc ₂O ₃Grain-size respectively below 1 μ m.

6. it is characterized in that: above-mentioned BaTiO according to claim 4 or 5 described methods, ₃, Bi ₂O ₃, Sc ₂O ₃, K ₂CO ₃, Na ₂CO ₃, Nb ₂O ₅, PbO and TiO ₂Purity is all greater than 99%.

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