CN104529534B - Method for improving flexoelectric effect of ferroelectric oxide material - Google Patents
Method for improving flexoelectric effect of ferroelectric oxide material Download PDFInfo
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- CN104529534B CN104529534B CN201410834912.9A CN201410834912A CN104529534B CN 104529534 B CN104529534 B CN 104529534B CN 201410834912 A CN201410834912 A CN 201410834912A CN 104529534 B CN104529534 B CN 104529534B
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Abstract
The invention discloses a method for improving the flexoelectric effect of a ferroelectric oxide material. The method comprises the step of carrying out chemical reduction on the ferroelectric oxide material.
Description
Technical field
The invention belongs to field of functional materials, relates generally to improve a kind of electromechanical Coupling in material --- flexure electricity effect
The method answered.
Background technology
There is the material of electromechanical Coupling can realize the conversion between mechanical energy and electric energy for some, widely be employed
In the devices such as sensor, driver, transducer and energy regenerating are prepared, there is highly important answering in civilian and national defence
With.These electromechanical Couplings mainly include piezoelectric effect, electric hysteresis flex effect and Maxwell effect etc.；Wherein piezoelectricity is imitated
It should be a kind of electromechanical Coupling being most widely used.In recent years, another electromechanical Coupling --- flexoelectric effect
Paid close attention to.The definition of flexoelectric effect (is just bending electric effect for a kind of polarization response of material in the case where there is strain gradient
Should), or the stress response (inverse flexoelectric effect) in the case of it there is electric-force gradient, can be described as with formula：
Positive flexoelectric effect：
Inverse flexoelectric effect：
In above formula, P1 is the dielectric polarization intensity in material；E1 is the electric field intensity in material；TijAnd SijPoint
Stress and strain that Wei be in material；μijklFor flexoelectric coefficient, reflection be material flexoelectric effect power.Flexure electricity
Coefficient is the tetradic, thus there is the component that is not zero in all symmetric materials.In many documents, μijklJing is normal
It is reduced to determinant component form μij。
A kind of novel piezoelectric material is can be designed that using flexoelectric effect --- flexure voltage composite.This
In material, some ingredients have special shape or structure, the power for being applied or the signal of telecommunication can be converted into into strain ladder
Degree or electric-force gradient, material produces flexure electroresponse, so that material shows apparent piezoelectric property.Because flexure electricity
Coefficient is the tetradic, different from traditional piezo-electricity composite material in may reside in any symmetric material, is scratched in design
During bent voltage composite, it is not necessary to which any component is piezoelectric.This does not only design novel piezoelectric material and provides more
For extensive material selection range, and what is more important this be badly in need of solving by current piezoelectric field asks
The unleaded of topic --- piezoelectric provides one and possible solution.
At present, prepare piezo-electricity composite material using flexoelectric effect and obtain certain progress, in some flexure voltage electricity
Apparent piezoelectric effect has been measured in material.The such as flexure voltage composite of a pyramid-like type structure, due to existing
Dissymmetrical structure, the power that ferroelectric ceramics upper and lower surface applies produces strain gradient in thickness of sample direction, so as to produce flexure
There is apparent piezoelectric property in electrical effect, material.Another flexure type flexure voltage composite, its basic structure is class
The girder construction of three-point bending is similar to, in the case where stress is applied, the flexural deformation of material produces strain gradient, so as to produce table
The piezoelectric property of sight.
Because the piezoelectric response for bending voltage electric material originates from the flexoelectric effect of material, thus material piezoelectric response
Size is strong and weak closely related with the flexoelectric effect of material.Research shows, the flexoelectric effect of material and the dielectricity of material
Can there is certain relation, the material with high dielectric property typically has relatively higher flexoelectric coefficient.Due to ferroelectric material
With the dielectric properties higher than common dielectric material, thus the material with high flexoelectric coefficient is obtained at present substantially
All it is ferroelectric material.
Ferroelectric oxide is widely used due to having the advantages that strong ferroelectricity, good temperature stability.These materials
The main ferroelectric material including bismuth-containing of material, leaded ferroelectric material, BaTiO3The ferroelectric material of base, SrTiO3The ferroelectric material of base,
LiNbO3Base ferroelectric material, (Na, K) NbO3The ferroelectric material of base, the ferroelectric material with tungsten bronze structure etc..Current these ferrum
Up to 10 have been measured in oxide material-6-10-4The flexoelectric coefficient of C/m, this is electric for the flexure voltage of utilitarian design
Material is provided may.But up to now, for the mechanism of production of these ferroelectric material flexoelectric effects still lacks system
Research and understand, the flexoelectric effect to how to improve ferroelectric material still lacks the effective method of system
The content of the invention
Some embodiments of the disclosure are related to a kind of method of the flexoelectric effect of raising ferroelectric oxide material, described
Method includes for the ferroelectric oxide material carrying out electronation.
In some embodiments of the disclosure, the electronation include by ferroelectric oxide material it is high at room temperature
Uniform or non-homogeneous reduction reaction is carried out with reducing agent, so as to chemical constituent and ferroelectricity para-electric to the ferroelectric oxide material
Phase change characteristics are modified.
In some embodiments of the disclosure, the ferroelectric oxide material of the ferroelectric oxide material including bismuth-containing,
Leaded ferroelectric oxide material, BaTiO3The ferroelectric material of base, SrTiO3The ferroelectric material of base, LiNbO3Base ferroelectric material,
(Na, K) NbO3The every combination of the ferroelectric material of base, the ferroelectric material with tungsten bronze structure or more.
In some embodiments of the disclosure, the ferroelectric oxide material be ceramics, monocrystalline, thin film, granule or
The form of fiber.
In some embodiments of the disclosure, higher than 400 DEG C, preferably above 700 DEG C of temperature is carried out for the reduction.
It is described to reduce at 700 DEG C to 1150 DEG C in some embodiments of the disclosure, preferably 700 DEG C to 950 DEG C, then
It is preferred that 750 DEG C to 850 DEG C of temperature is carried out.
In some embodiments of the disclosure, the reducing agent includes graphite, hydrogen or carbon monoxide etc..
In some embodiments of the disclosure, the ferroelectric oxide material and graphite block two sides are polished so that
There is reduction reaction in the state of the single or double of the ferroelectric oxide material and graphite contact.
In some embodiments of the disclosure, the reaction carries out 1 minute to 24 hours, preferably 5 minutes to 12 hours,
Further preferably 0.5 hour to 6 hours.
Description of the drawings
The reducing process of Fig. 1 example strip ferroelectric ceramics samples.
Specific embodiment
The present invention proposes a kind of modified method of electronation for ferroelectric oxide material, can increase substantially material
The flexoelectric effect of material.
Ferroelectric oxide material can be used in the form of ceramics, monocrystalline or thin film, and its preparation technology is different.Than
As ferroelectric oxide ceramics can utilize traditional solid-phase synthesis to prepare.Its canonical process is first by various oxide raw materials
Mix homogeneously in ball mill is put into suitable proportioning, the then insulation synthesis at 800-1200 DEG C, then by synthetic powder
Body carries out the size that ball milling further reduces powder body, is subsequently adding binding agent, is pressed into the sample of required form, such as disk,
Strip etc..Finally sample is carried out after plastic removal and is sintered at a proper temperature ceramics.
At high temperature (400 DEG C of ＞) and reducing agent be such as to need have effigurate ferroelectric oxide material during reduction
The graphite of solid phase, hydrogen, carbon monoxide, nitrogen of gas phase etc. are contacted 5 minutes to 24 hours.One typically for unleaded
(1-x)Na1/2Bi1/2TiO3-x BaTiO3Ceramics are by ceramics sample by the use of graphite as the reducing process process of reducing agent and go back
The surface rubbing of former agent graphite block, is then in close contact the single or double of ceramics with graphite, then by graphite and Ceramic Like
Product are clipped between aluminium oxide or zirconium oxide cover plate to keep the close contact of ceramic material and graphite.Then these materials are put into
In electric furnace, reduce at 700-950 DEG C 5 minutes to 24 hours, sample is finally taken out from stove natural cooling in atmosphere.
Using the sample surfaces after reduction are by burning infiltration, evaporation or the method such as sputter and prepare metal electrode as conductive layer, so
The measurement of flexoelectric coefficient is carried out afterwards.
Flexoelectric coefficient measurement needs to prepare sample of different shapes, such as μ according to the flexoelectric coefficient of required measurement12System
Several measurements needs strip sample, and one end of sample is clamped during measurement, and the other end is promoted using a driver and causes length
Bar shaped sample forms bending, so as to occur gradient of the strain along its length in thickness direction in sample.According on electrode
The relation of the signal of telecommunication and the strain gradient that are produced due to flexoelectric effect that measurement is obtained, obtains μ12Coefficient.
Ours test result indicate that, after reduction chemical constituent change caused by component nonunf ormity and reduction
Tremendous influence to phase transformation between material ferroelectric phase and paraelectric phase, so as to cause material in be polarized in the presence of strain gradient
It is easier to turn to so that the flexoelectric coefficient of the sample after reduction improves a lot.
Ferroelectric oxide material can increase substantially flexoelectric coefficient after reducing process.Such as Na1/ 2Bi1/2TiO3After reducing process, flexoelectric coefficient can improve nearly two orders of magnitude to the ferroelectric ceramics of base.If by these
Materials application can increase substantially the apparent piezoelectric property of material in flexure voltage electric material.
This method of reducing is for some leadless piezoelectric material material systems such as Na1/2Bi1/2TiO3Base ferroelectric material more has
Effect, the flexoelectric coefficient of material is higher after reduction, can be used to prepare leadless piezoelectric flexure voltage composite, to replace biography
The lead base piezoelectric being widely used of system.
Embodiment 1
By Bi2O3, Na2CO3, BaCO3, TiO2(being pure, the Chinese medicines group of analysis) adds ethanol ball milling 6-8 hour after bake
It is dry, synthesize within 2 hours in 850 DEG C of insulations.Then by the powder body ball milling after synthesis, appropriate binding agent is added, is pressed into strip
Sample, is incubated 1 hour and sinters at 1180 DEG C, obtains 0.80Na1/2Bi1/2TiO3-0.20BaTiO3Ferroelectric ceramics, final ceramics
Sample size is 90mm × 10mm × 1.25mm.In the sample surface sputtering gold electrode of two.And then sample one end will be clamped,
The other end applies sinusoidal mechanical oscillation signal by an exciting instrument so that strip material produces bending.Material is produced due to bending
The signal of telecommunication of raw flexure electroresponse is by a stand lock phase amplifier measuring.The flexoelectric coefficient of final material is calculated by corresponding formula
Go out.Flexoelectric coefficient μ of this material before for reduction12For 2.4 μ C/m.
Embodiment 2
After the electrode of the rectangular-shaped ceramic sample described in embodiment 1 is ground off, press on one surface of strip sample
Upper graphite block (as shown in Figure 1), is then placed in high-temperature electric resistance furnace being reduced 3 hours at 825 DEG C.After reduction terminates, on sample
Lower surface sputters gold electrode.The flexoelectric coefficient of material is measured using the method described in embodiment 1.Sample after reduction
μ12Exceed 100 μ C/m, improve nearly 40 times.
Embodiment 3
By soft P (Zr, the Ti) O of strip3(P51) ferroelectric ceramics, two sides burning infiltration silver electrode measures the flexure of material
Electrostrictive coefficient, measures the μ for obtaining12For 4.1 μ C/m.Then electrode is ground off, is taken similar to the reduction side described by embodiment 2
Method, with graphite contact at a temperature of 840 DEG C, is incubated 2 hours, and then the upper and lower surface in the sample of reduction sputters gold electrode.
Measure the μ of the material after being reduced12About 8.5 μ C/m.The flexoelectric coefficient of the P51 ferroelectric ceramics after reduction is for before being reduced
Twice.
Embodiment 4
By rigid P (Zr, the Ti) O of strip3(P81) ferroelectric ceramics, two sides burning infiltration silver electrode measures the flexure of material
Electrostrictive coefficient, measures the μ for obtaining12For 2.3 μ C/m.Then electrode is ground off, is utilized similar to the method for reducing in embodiment 2 also
Original, with graphite contact at a temperature of 840 DEG C, is incubated 2 hours, and then the upper and lower surface in the sample of reduction sputters gold electrode.
Measure the μ of the material after being reduced12About 13.1 μ C/m.The flexoelectric coefficient of the P81 ferroelectric materials after reduction is about gone back
Five times before original.
Embodiment 5
By the BaTiO of strip3Ferroelectric ceramics sputters gold electrode, measures its flexoelectric coefficient, measures the μ for obtaining12For
25.3μC/m.Then electrode is ground off, using the method reduction being similar in embodiment 2, in 1000 DEG C or so reductase 12 hours, so
Afterwards the upper and lower surface in the sample of reduction sputters gold electrode, the μ for measuring12For 46.1 μ C/m, the twice of sample before about reducing.
Claims (5)
1. a kind of method of the flexoelectric effect for improving ferroelectric oxide material, methods described includes the ferroelectric oxide material
Material carries out electronation；
Wherein described electronation include by ferroelectric oxide material height carry out with reducing agent at room temperature it is uniform or non-homogeneous
Reduction reaction, so as to be modified to the chemical constituent of the ferroelectric oxide material and ferroelectricity para-electric phase change characteristics；
Wherein described reduction is carried out in 700 DEG C to 1150 DEG C of temperature；
Wherein described reducing agent includes graphite, hydrogen or carbon monoxide and the nitrogen of reduction effect can be produced to ferroelectric oxide
Gas, noble gases；
Wherein the ferroelectric oxide material and graphite block two sides are polished so that the ferroelectric oxide material one side or
There is reduction reaction in the state of two-sided and graphite contact.
2. the method described in claim 1, wherein the ferroelectric oxide material includes the ferroelectric oxide material of bismuth-containing, leaded
Ferroelectric oxide material, BaTiO3The ferroelectric material of base, SrTiO3The ferroelectric material of base, LiNbO3Base ferroelectric material, (Na, K)
NbO3The every combination of the ferroelectric material of base, the ferroelectric material with tungsten bronze structure or more.
3. the method described in claim 1, wherein the ferroelectric oxide material is ceramics, monocrystalline, thin film, granule or fiber
Form.
4. the method described in claim 1, wherein the reaction carries out 1 minute to 24 hours.
5. the method described in claim 1, wherein the reaction carries out 5 minutes to 12 hours.
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| CN105140387B (en) * | 2015-08-24 | 2017-12-22 | 中国科学技术大学 | One kind flexure voltage composite |
| CN107946453B (en) * | 2017-12-01 | 2020-05-05 | 中国科学技术大学 | Thermoelectric conversion method |
| CN109087988B (en) * | 2018-08-13 | 2020-12-25 | 中国科学技术大学 | Thermoelectric conversion method |
| CN110872190A (en) * | 2018-08-30 | 2020-03-10 | 中国科学技术大学 | Method for adjusting dielectric material apparent flexoelectric effect |
| CN113043582B (en) * | 2019-12-26 | 2023-03-31 | 中国科学技术大学 | Method for improving piezoelectric response of polymer material |
| CN114685187B (en) * | 2022-03-31 | 2023-05-12 | 中山大学 | Method for improving equivalent flexoelectric response of composite ceramic |
| CN116573932B (en) * | 2023-06-01 | 2024-07-30 | 中国科学技术大学 | Can improve MTiO3Sintering preparation method of ceramic flex electric response |
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