CN110002497B - Sodium bismuth titanate nanotube and preparation method thereof - Google Patents

Sodium bismuth titanate nanotube and preparation method thereof Download PDF

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CN110002497B
CN110002497B CN201910312901.7A CN201910312901A CN110002497B CN 110002497 B CN110002497 B CN 110002497B CN 201910312901 A CN201910312901 A CN 201910312901A CN 110002497 B CN110002497 B CN 110002497B
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CN110002497A (en
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朱哲
李俊鹏
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Xiangtan University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
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    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G29/00—Compounds of bismuth
    • C01G29/006—Compounds containing, besides bismuth, two or more other elements, with the exception of oxygen or hydrogen
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
    • C01P2004/13—Nanotubes

Abstract

The invention discloses a sodium bismuth titanate nanotube and a preparation method thereof. The sodium bismuth titanate nanotube has a stripe domain structure, the stripe domains are alternately arranged along the length direction of the sodium bismuth titanate nanotube, and the width of the stripe domains is 10-50 nm. The regular stripe domain structure can effectively improve the piezoelectric coefficient of the sodium bismuth titanate nanotube, and the high piezoelectric coefficient of the sodium bismuth titanate nanotube is close to that of a lead-containing perovskite type material. The preparation method comprises the following steps: (1) preparing bismuth sodium titanate precursor solution (2) synthesizing the bismuth sodium titanate nanotube by a spin-out method. The method can simply prepare the sodium bismuth titanate nanotube array with controllable size and uniform wall thickness.

Description

Sodium bismuth titanate nanotube and preparation method thereof
Technical Field
The invention relates to a sodium bismuth titanate nanotube and a preparation method thereof, belonging to the technical field of inorganic non-metallic materials.
Background
Due to the characteristics of small volume and large specific surface area, the one-dimensional piezoelectric material has wide application prospect in the fields of Ferroelectric Random Access Memory (FRAM), nano electromechanical systems, energy collectors and the like. With the development concept of green environmental protection and the rapid development of the integration of the microelectronic industry, the preparation and application research of the one-dimensional lead-free piezoelectric material gradually become a focus of scientific community. The preparation of the one-dimensional lead-free piezoelectric material is not only for observing the structure, but also for the performance research and the device application, so the research of the preparation method is also a great challenge. The common one-dimensional leadless piezoelectric materials at present are: nanowires, nanofibers, nanotubes, and the like. The morphology structure is one of the main factors influencing the piezoelectric performance of the one-dimensional lead-free piezoelectric material, and when piezoelectric response is observed, compared with the nano wire and the nano fiber, the nano tube with uniform wall thickness is less influenced by the clamping effect, so that the piezoelectric coefficient of the nano tube is favorably improved. The method for preparing the one-dimensional leadless piezoelectric nanotube at present mainly comprises the following steps: hydrothermal method, electrostatic spinning method, template method. In patent CN 106564942A, a hydrothermal method is adopted to prepare titanate nanotubes, and the preparation method has the technical problems of complex process, high cost and the like. In patent CN 105401260 a, an electrostatic spinning method is adopted to prepare strontium titanate nanotubes, and the preparation method has the technical problems of complicated equipment and process, and the like. The hydrothermal method and the electrostatic spinning method for preparing the nano tube have the defects of inaccurate wall thickness control and difficult synthesis and uniform length. In the process of preparing the nanotube structure by the template method, the manner of filling the sol is generally limited to: soaking method, suction filtration method, and spin coating method. In patent CN 101279767A, lanthanide rare earth doping is synthesized by adopting a soaking methodThe preparation time of the bismuth titanate nanotube is about 7h, and the preparation time is long; haiballa A S et al prepared LSCF64 nanotube arrays by soaking for about 24 hours, a longer preparation time [ Haiballa A S, Ismail I, Osman N, et al0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF64)perovskite nanotubes via sol-gel template synthesis[C]//AIP Conference Proceedings.AIP Publishing,2017,1885(1):020234.](ii) a And the driving force of the soaking method is only the self-gravity of the sol and the adsorption force of the template holes to the sol, which can cause the efficiency of filling the template with the sol to be reduced. Therefore, the preparation method has the technical problems of long preparation time, low filling rate and the like. In patent CN 10376527A, lanthanum molybdate-based nanotube arrays were prepared by suction filtration, and the KNN nanotube arrays [ Zhou D, Gu H, Hu Y, et al Synthesis, chromatography and fluorescence Properties of lead-free K ] were also prepared by suction filtration0.5Na0.5NbO3 nanotube arrays[J].Journal of applied physics,2011,109(11):114104.]However, the suction filtration method has the technical problem that the wall thickness is not easy to control because the sol lacks the centrifugal force pointing to the inner wall of the template, so that the phenomenon of nonuniform wall thickness of the nanotube occurs in the annealing process of the sol. In patent CN 102093048, perovskite ferroelectric nanotube arrays were prepared by spin coating, and Li Z et al also prepared PZT nanotube arrays by spin coating [ Li Z, Xu Z, Ma Z, et al0.52Ti0.48)O3 nanotubes synthesis and infrared absorption properties[J].Optical Materials,2016,51:171-174.]. The spin coating method causes the depth of a sol filling template to be smaller due to the lack of downward negative pressure of the sol, so that the prepared nanotube has shorter length and small length-diameter ratio and other technical problems. The patents and documents for preparing the nanotube by the soaking method, the suction filtration method and the spin coating method have the technical problems that the application purpose of the device is difficult to evaluate and the like because the piezoelectric coefficient of the nanotube is not given.
Li X et al prepared a beta-phase PVDF nanotube array by soaking method, with a piezoelectric coefficient of about 19.2pm/V [ Li X, Lim Y F, Yao K, et al. Ferro electric Poly (vinylidenefluoride) ] Home Polymer Nanotubes arrayion in Anodic Alumina Membrane Template[J].Chemistry of Materials,2013,25(4):524–529.]The preparation method has the technical problems of small piezoelectric coefficient and the like. Bhavanasi V et al also prepared PVDF-TrFE nanotube arrays by soaking methods with piezoelectric coefficients of about 44pm/V [ Bhavanasi V, Kusuma D Y, Lee P S. polization organization, Piezoelectricity, and Energy Harvesting Performance of Ferroelectric PVDF-TrFE Nanotubes Synthesized by nanocontaining [ J].Advanced Energy Materials,2014,4(16):1400723.]The preparation method still has the technical problems of small piezoelectric coefficient and the like. ZHONG C et al combined with template for preparing isotypic phase boundary BiScO with different wall thickness by electrodeposition3-PbTiO3The nanotube array has a wall thickness of 30nm and a piezoelectric coefficient of 50-70 pm/V [ Zhong C, Lu Z, Wang X, et al, template-based synthesis and piezoelectric properties of BiScO3-PbTiO3 nanotube arrays[J].Journal of Alloys and Compounds,2016,655:28-31.]. The lead-containing morphotropic phase boundary nanotube obtained by the preparation method has a large piezoelectric coefficient. In summary, the one-dimensional lead-free piezoelectric material prepared by a single template method is difficult to approach the piezoelectric coefficient of the lead-containing piezoelectric material, and the method also has the technical problems of high cost, complex process, incompatibility with high length-diameter ratio, accurate wall thickness control and the like. Therefore, the one-dimensional sodium bismuth titanate (Na) prepared by the spin-out process provided by the invention0.5Bi0.5TiO3Hereinafter abbreviated as NBT) nanotubes have the advantages of low cost, simple method, high length-diameter ratio, accurate control of wall thickness, high piezoelectric coefficient and the like.
Disclosure of Invention
In view of the defects of the prior art, the first object of the invention is to provide a one-dimensional lead-free perovskite sodium bismuth titanate (NBT) nanotube which has high length-diameter ratio, different contrast alternating stripe domain structures and high piezoelectric coefficient.
The second purpose of the invention is to provide a preparation method of the sodium bismuth titanate nanotube, which is simple and low in cost, and can controllably obtain the sodium bismuth titanate nanotube with high length-diameter ratio, uniform wall thickness and stripe domain structure.
In order to achieve the above object, the present invention adopts the following technical solutions.
The sodium bismuth titanate nanotube has a stripe domain structure, stripe domains are alternately arranged along the length direction of the sodium bismuth titanate nanotube, and the width of the stripe domains is 10-50 nm.
In the technical scheme of the invention, the provided NBT nanotube has a stripe-shaped domain structure which is alternately arranged along the length direction in the inner part under the unpolarized (non-voltage-applied) state, and the spontaneous polarization of the NBT nanotube has certain directionality. The existence of the regularly arranged specific domain structure leads the nanotube to tend to have higher anisotropy along the growth direction, thereby leading the nanotube to show stronger piezoelectric performance and high piezoelectric coefficient. After polarization, the stripe domains of the NBT nanotube are arranged more regularly, and the polarization direction is more directional, so that the piezoelectric performance of the NBT nanotube is more excellent. The NBT nanotube has a unique hollow tubular structure, and can effectively reduce the influence of a clamping effect when observing piezoelectric response, thereby greatly improving the piezoelectric coefficient of the NBT nanotube.
Preferably, the length of the sodium bismuth titanate nanotube is 5-30 μm, and the length-diameter ratio is 100-1000.
More preferably, the length of the sodium bismuth titanate nanotube is 15-25 μm, and the aspect ratio is 100-500.
In a preferable scheme, the diameter of the sodium bismuth titanate nanotube is 30-200nm, and the wall thickness is 10-35 nm.
The invention relates to a preparation method of a sodium bismuth titanate nanotube, which comprises the following steps:
dropwise adding a bismuth source-containing solution into a sodium source-containing solution to obtain a bismuth source-sodium source-containing solution, then adding a titanium source into the bismuth source-sodium source-containing solution to obtain a mixed solution, adding a stabilizer into the mixed solution to obtain an NBT precursor solution, then carrying out suction filtration and filling on the NBT precursor solution in a template, carrying out spin coating for more than 2 times to enable sol filled in the template to form a sol tube with uniform wall thickness in the template, and finally drying, annealing and corroding the template filled with the NBT precursor solution to obtain the NBT nanotube.
In the technical scheme of the invention, the NBT precursor solution is prepared and is in a sol state, and the precursor solution is filled in the template by utilizing a method combining suction filtration and spin coating (hereinafter referred to as spin-draw method for short), and the inventors find that the spin-draw method for preparing the NBT nanotube has the advantages of low cost, simple method, high length-diameter ratio, accurate wall thickness control and the like through research. The pumping and spinning method firstly uses a pumping and filtering device, and improves the filling rate and the filling length of the sol in the AAO template by utilizing the negative atmospheric pressure, the sol gravity and the template hole adsorption force; and then, a spin coating device is used, mechanical rotation is utilized to generate centrifugal force on the sol, and the uniform wall thickness and the accurate wall thickness control are achieved by adjusting the rotation times. The NBT nanotube with high filling rate, large length-diameter ratio and accurately controlled wall thickness can be prepared by combining the suction filtration process and the spin coating process and the optimal combination parameters, the problems of long preparation period and low filling rate of the soaking method are solved, the problem that the wall thickness is not easy to control in the preparation process of the suction filtration method is solved, and the problem that the length-diameter ratio is low in the preparation process of the spin coating method is also solved. The surface ratio of the NBT nanotube is obviously increased along with the reduction of the tube diameter, and the piezoelectric coefficient is obviously improved.
The inventor also finds that the depth of the sol filled in the AAO template by adopting the spin-out method is deeper, and the time is enough for the particles with similar sizes to directionally grow into particle chains with consistent orientation along the thickness direction of the template, so that the nanotube with high length-diameter ratio and a stripe domain structure is obtained. This cannot be achieved by any single other method. Due to the existence of the regularly arranged specific domain structure, the spontaneous polarization has certain directionality, so that the nanotube tends to have higher anisotropy along the growth direction, the nanotube shows stronger piezoelectric performance, the diameter of the nanotube is reduced along with the reduction of the template aperture, the length-diameter ratio and the specific surface area of the nanotube are obviously increased, the ratio of the atomic number on the surface of the nanotube to the total atomic number is obviously increased, the atomic number on the surface of the nanotube is relatively increased, the surface atoms have high activity, and the piezoelectric performance of the nanotube is further enhanced.
In a preferred embodiment, the bismuth source is bismuth nitrate.
In a preferable scheme, in the solution containing the bismuth source, the solid-liquid mass volume ratio of the bismuth source to the solvent is 0.06-0.08 g:1 mL.
In a preferred embodiment, the solvent in the bismuth source-containing solution is ethylene glycol monomethyl ether.
In a preferred embodiment, the sodium source is sodium acetate.
In a preferable scheme, in the solution containing the sodium source, the solid-liquid mass volume ratio of the sodium source to the solvent is 0.05-0.06 g:1 mL.
In a preferred embodiment, the solvent in the solution containing the sodium source is glacial acetic acid.
In a preferred embodiment, the titanium source is titanate.
More preferably, the titanium source is tetrabutyl titanate.
Preferably, in the mixed solution, the ratio of Na to Bi to Ti is 1:1 to 1.1:2 to 2.1.
In a preferred embodiment, the stabilizer is acetylacetone.
More preferably, the volume fraction of the stabilizer in the NBT precursor solution is 3-6 vol%.
The medicament can be seen from the above, the invention accurately limits the selected sodium source, titanium source, bismuth source and related solvent, and simultaneously accurately limits the medicament proportion and solvent proportion in a small range, because the preparation of the nano material is a finely regulated and controlled process with a larger difficulty coefficient, and different medicaments have larger influence on the controllability of the appearance and performance of the NBT nanotube.
Preferably, the template is a porous alumina template (hereinafter referred to as AAO template), the pore diameter of the template is 30-200nm, and the depth of the template is 20-30 μm.
In the preferable scheme, during suction filtration, the negative pressure is less than 10-1Pa。
Preferably, the spin coating process is to spin at a speed of 300-.
More preferably, the spin-coating process is performed at a speed of 400-600r/min for 10-35s, and then at a speed of 2500-3500r/min for 50-70 s.
Preferably, the spin coating times are 2-5.
The inventor finds that the number of spin coating times cannot be less than 2, and if the number of spin coating times is less than 2, although a sol tube with a certain thickness can be formed, defects such as holes and the like can be generated on part of the surface of the nanotube in the annealing and crystallization processes, and the defects are not ideal nanotubes and greatly influence the performance of the nanotube.
If the processes of suction filtration and spin coating are not in the scope of the invention, the obtained final product may not prepare the NBT nanotube which is compatible with the length-diameter ratio and can not accurately control the wall thickness, and further, the regular stripe domain structure on the surface of the nanotube can not be obtained, thereby influencing the piezoelectric performance of the nanotube. If a single suction filtration method is used, the phenomenon of nonuniform wall thickness of the nanotube can occur in the annealing process of the sol due to the lack of centrifugal force pointing to the inner wall of the template, so that the wall thickness of the nanotube is difficult to accurately control; if a single spin coating method is used, the depth of the sol filled template is smaller due to the lack of negative pressure downwards of the sol, so that the prepared nanotube has shorter length and is difficult to obtain the nanotube with large length-diameter ratio. Therefore, the process of the spin-out method is very important in the invention, and not only can the NBT nanotube which is compatible with the length-diameter ratio and can accurately control the wall thickness be prepared, but also the prepared nanotube presents a stripe domain structure and further presents more excellent piezoelectric performance.
Preferably, the drying temperature is 100-150 ℃, and the drying time is 2-5 min.
In a preferred scheme, the annealing process parameters are as follows: firstly heating to 170 ℃ and 180 ℃, and preserving heat for 8-12 min; then heating to 380 ℃ and 420 ℃, and preserving the heat for 10-20 min; then the temperature is raised to 680 ℃ and 720 ℃, and the temperature is kept for 45-90 min; the heating rate is controlled to be 4-6 ℃/min.
The annealing process also has great influence on the NBT nanotube prepared by the invention, and in the annealing process, gel is formed within the range of 170-180 DEG CVolatilizing the organic solvent in the solvent; decomposing and burning organic matters such as ethylene glycol monomethyl ether and inorganic matters such as nitrate in the gel at the temperature of 380-420 ℃; in the range of 680-720 ℃, the gel needs to be kept for 45-90min, and a typical perovskite phase is generated by crystallization. According to the steps of the annealing process, the NBT nanotube with the fringe domain structure, which is compatible with the length-diameter ratio and can accurately control the wall thickness, can be prepared. If the heat preservation time of the high-temperature region is less than 45min, the crystallization effect of the NBT nanotube is poor, and the domain structure distribution on the surface of the nanotube is influenced, so that the piezoelectric performance of the nanotube is influenced; above 90min, the amorphous alumina template will be converted to relatively pure gamma-Al2O3The use of alkaline solutions to corrode alumina templates requires a relatively long time to obtain a single nanotube, which in turn affects the rate of experimental progress.
Preferably, the etching solution used for etching is a phosphoric acid solution with the mass fraction of 3-8wt%, and the etching time is 6.5-7.5 h.
The invention has the beneficial effects that:
(1) the preparation method of the invention has low cost and simple method.
(2) The invention can prepare the NBT nanotube with high length-diameter ratio, accurately controlled wall thickness and uniform wall thickness.
(3) The NBT nanotube prepared by the method has a stripe domain structure, and the structure effectively improves the piezoelectric property of the NBT nanotube.
(4) The NBT nanotube prepared by the method has excellent piezoelectric property, the piezoelectric property of the nanotube is obviously improved along with the reduction of the diameter of the NBT nanotube, the specific surface area of the NBT nanotube is obviously increased along with the reduction of the diameter of the nanotube, and the piezoelectric property of the nanotube is further enhanced, wherein the piezoelectric coefficient range of the nanotube with the diameter of about 200nm is 25-29pm/V, and the effective piezoelectric coefficient d of the nanotube with the diameter of about 30nm is33Is 60-65 pm/V.
Drawings
FIG. 1 is a flow chart of an experiment for preparing NBT nanotube arrays;
FIG. 2 is an XRD pattern of NBT nanotube arrays prepared in different filling modes;
NBT nanotubes prepared in different filling regimes were tested using an X-ray diffractometer (XRD, X' PertPRO, Pa Naco., Netherlands) and the XRD pattern obtained is shown in FIG. 2. As can be seen from the figure, all diffraction peaks are matched with the diffraction peaks of a typical perovskite structure, and no secondary phase exists, which shows that the NBT nanotube prepared by four filling modes has a perovskite structure and a good crystallization effect.
FIG. 3 is an SEM image of a 200nm NBT nanotube array prepared by a soaking method;
the NBT nanotube array prepared by the soaking method was characterized by scanning electron microscopy (SEM, MIRA3LMU, tai siken, czech), and the obtained SEM image is shown in fig. 3.
FIG. 3(a) is an SEM image of an NBT nanotube array prepared by the dipping method in comparative example 1 of the present invention, in which the nanotubes are filled in the AAO template. FIG. 3(b) is a partial enlarged view of the red box of FIG. 3(a), with only a portion of the nanotubes in the AAO template, illustrating the low filling rate of NBT nanotubes in the AAO template.
FIG. 4 is an SEM image of a 200nm NBT nanotube array prepared by suction filtration;
the NBT nanotube array prepared by suction filtration was characterized by scanning electron microscopy (SEM, MIRA3LMU, zeeken, czech), and the obtained SEM image is shown in fig. 4.
FIG. 4(a) is an SEM image of an NBT nanotube array prepared by suction filtration in comparative example 2 of the present invention, in which the nanotubes are significantly filled in the AAO template. FIG. 4(b) is a partial enlarged view of the red box of FIG. 4(a), in which there are many nanotubes in the AAO template, but the wall thickness of the nanotubes is not uniform, indicating that the NBT nanotubes have a high filling rate in the AAO template and that it is difficult to control the wall thickness of the nanotubes by suction filtration.
FIG. 5 is an SEM image of 200nm NBT nanotube array prepared by spin coating;
the NBT nanotube array prepared by spin coating was characterized using a scanning electron microscope (SEM, MIRA3LMU, tesken, czech) and the resulting SEM image is shown in fig. 5.
FIG. 5(a) is an SEM image of an NBT nanotube array prepared by spin coating in comparative example 3 of the present invention, where the nanotubes had significant filling in the AAO template. Fig. 5(b) is a partial enlarged view of the red box in fig. 5(a), there are more nanotubes in the AAO template, but the length of the prepared nanotubes is shorter due to the lack of negative pressure downward of the sol, which indicates that the filling rate of NBT nanotubes in the AAO template is higher, and the spin coating method is difficult to prepare nanotubes with large aspect ratio.
FIG. 6 is a comparative analysis table of preparation mechanism under different filling modes;
by comparing the mechanisms of preparing the nanotube array by a soaking method, a suction filtration method and a spin-coating method, the problems of long preparation period, low filling rate and the like in the soaking method, the problems of difficulty in controlling wall thickness and the like in the suction filtration method and the problems of low length-diameter ratio and the like in the prepared nanotube in the spin-coating method are found, and the three methods are not the optimal scheme for preparing the NBT nanotube with high filling rate, accurate wall thickness control and large length-diameter ratio.
FIG. 7 is an SEM image of NBT nanotube array of 200nm prepared by spin-draw method;
the NBT nanotube array prepared by the spin method was characterized by scanning electron microscopy (SEM, MIRA3LMU, Tessenken, Czech) and the SEM image is shown in FIG. 7.
Fig. 7(a) is an SEM image of NBT nanotube array prepared by spin-draw method in example 1 of the present invention, and the filling rate of nanotubes in AAO template is significantly improved compared to the soaking method. Fig. 7(b) is a partial enlarged view of fig. 7(a), in which nanotubes are uniformly distributed in the AAO template and the wall thickness of the nanotubes is relatively uniform, compared to the suction filtration method and the spin coating method.
FIG. 8 is an EDS energy spectrum of a 200nm NBT nanotube array prepared by spin extraction;
fig. 8(a) is an SEM image of NBT nanotube array prepared by spin-draw method, and it can be seen that the filling rate of nanotubes in AAO template is high. Fig. 8(b) and 8(c) are the EDS energy spectrum of the purple frame of fig. 8(a) and the corresponding element composition table, which can be found as follows: (1) the NBT nanotube consists of Na, Bi, Ti and O elements, and the atomic percentage is close to 1:1: 2: 6 with NBT (Na)0.5Bi0.5TiO3) The stoichiometric ratio is substantially the same; (2) the existence of the Al element is caused by the growth of the NBT nanotube in the porous AAO template; the Au element is present because it acts as a conducting medium for SEM observation.
FIG. 9 is an SEM image of a modified single 200nm NBT nanotube;
FIG. 9(a) is an SEM image of single NBT nanotubes prepared by the spin-draw method, and it can be seen that the single NBT nanotubes have smooth surfaces, a length of about 14 μm and a diameter of about 200nm, which is substantially consistent with the pore size of the template used. Fig. 9(b) is a partial enlarged view of fig. 9(a), which clearly shows a tubular structure and a relatively uniform wall thickness, and it is fully demonstrated that when the nano-structure is prepared by the template method, the solvent is volatilized during the high-temperature annealing process, so that the sol is shrunk to both sides of the hole, and finally the tubular structure is formed.
FIG. 10 is a schematic diagram of a single 200nm NBT nanotube in example 1 of the present invention;
the microstructure of the single NBT nanotubes obtained in example 1 was characterized using a contact mode using a Piezoelectric Force Microscope (PFM) module in an atomic force microscope (AFM, MFP-3D Infinity, arylum Research), and the resulting topography is shown in fig. 10. It can be seen from FIG. 10 that the surface of the single NBT nanotube is smooth and has a diameter of about 240 nm.
FIG. 11 is the phase-voltage hysteresis curve and amplitude-voltage butterfly curve of a single 200nm NBT nanotube in example 1 of the present invention.
The piezoelectric performance of a single 200nm NBT nanotube obtained in example 1 was tested by PFM to obtain a phase-voltage hysteresis curve and an amplitude-voltage butterfly curve as shown in FIG. 11.
As can be seen from FIG. 11, the NBT nanotube has a typical "butterfly curve", the two wings of the curve are symmetrical, the deviation of the symmetry center is small, which shows that the NBT nanotube has excellent piezoelectric performance and an effective piezoelectric coefficient d33About 27.53 pm/V. Meanwhile, it can be seen that the phase is turned over by 180 ° at a voltage of about ± 35V, which indicates that the NBT nanotube has excellent ferroelectric properties.
FIG. 12 is a domain state evolution diagram of a single 200nm NBT nanotube under the action of an applied electric field in example 1 of the present invention.
The single 200nm NBT nanotube obtained in example 1 was tested for domain state under an applied electric field by PFM, and the obtained domain state evolution diagram is shown in FIG. 12.
Fig. 12(a) is an original domain diagram of a single NBT nanotube, where the top domain state of the nanotube is blue, the polarization direction is directed to the top, the left domain state is blue, yellow, and red, and the polarization directions are directed to the top, the bottom, and the horizontal direction, respectively; FIG. 12(b) shows domain state distribution at-15V, where the top turns red to 90 ° domain inversion and the left side turns blue to yellow to 180 ° domain inversion; fig. 12(c) shows domain state distribution at +10V, where the top red color changes to a domain state with alternating blue and dark red colors, 90 ° domain inversion occurs, and the left red color changes to blue color, 90 ° domain inversion occurs; fig. 12(d) shows the domain state distribution at the voltage of +15V, which tends to the original domain state distribution of fig. 12 (a). By applying different voltages, the surface domain state of the NBT nanotube is changed greatly and regularly, which shows that the electric field can not only cause 180-degree domain inversion, but also cause 90-degree domain inversion.
After polarization, the stripe domains of the NBT nanotube are arranged more regularly, and the polarization direction is more directional, so that the piezoelectric performance of the NBT nanotube is more excellent. The NBT nanotube has a unique hollow tubular structure, and can effectively reduce the influence of a clamping effect, thereby greatly improving the piezoelectric coefficient of the NBT nanotube.
FIG. 13 is a phase-voltage hysteresis curve diagram and an amplitude-voltage butterfly curve diagram of a single 30nm NBT nanotube in example 3 of the present invention.
The piezoelectric performance of the single 30nm NBT nanotube obtained in example 3 was tested by PFM to obtain a phase-voltage hysteresis curve and an amplitude-voltage butterfly curve as shown in fig. 13.
As can be seen from fig. 13, the NBT nanotube has a typical "butterfly curve", compared to the 200nm nanotube, the two wings of the curve are more symmetrical, the deviation of the symmetry center is smaller, which indicates that the NBT nanotube has excellent piezoelectric performance; along with the reduction of the pipe diameter size of the nano-tube, the piezoelectric property of the 30nm nano-tube is greatly improved, and the effective piezoelectric coefficient d33About 62.11pm/V, which is close to or equivalent to the piezoelectric coefficient of one-dimensional lead-containing piezoelectric material. Meanwhile, it can be seen that when the voltage is about +/-5V, the phase is turned over by 180 degrees, the required turning voltage is obviously reduced, and the 30nm NBT nanotube has excellent ferroelectricityEnergy is saved; meanwhile, the NBT nanotube has the advantages that the body surface ratio is obviously increased along with the reduction of the tube diameter, and the piezoelectric coefficient is obviously improved.
FIG. 14 is a schematic diagram of a mechanism for preparing striped domain NBT nanotubes by spin-draw;
the sol filled in the AAO template by adopting the spin-draw method has deeper depth, and has enough time to allow the particles with similar sizes to directionally grow into particle chains with consistent orientation, thereby obtaining the nanotube with high length-diameter ratio and a stripe domain structure. And with the reduction of the aperture of the template, the diameter of the nanotube is reduced, the length-diameter ratio and the specific surface area of the nanotube are obviously increased, the ratio of the surface atomic number of the nanotube to the total atomic number is obviously increased, and the surface atomic number of the nanotube is relatively increased, so that the surface atoms have high activity, and the piezoelectric performance of the nanotube is further enhanced.
Meanwhile, with the increase of the wall thickness, the nanotube wall contains larger sol ions, the crystal grains with larger size formed after annealing can reduce the gaps among the crystal grains, and the crystal grains with similar size are oriented and arranged more tightly along the thickness direction of the AAO template for growth. From a thermodynamic perspective, the driving force for spontaneous and directed adsorption causes a large reduction in the free energy of the particle surface; in addition, the thickness of the wall inhibits the size of the grain size, TiO6The increase of the octahedron deformation can generate larger internal stress, and further promote the aggregation of crystal grains with similar sizes, thereby forming the NBT nanotube with a fringe domain structure.
Due to the existence of the regularly arranged specific domain structure, the spontaneous polarization of the nanotube has certain directionality, so that the nanotube tends to have higher anisotropy along the growth direction, and the nanotube has stronger piezoelectric performance.
Detailed Description
Testing the NBT nanotube array microstructure, comprising the steps of:
(1) putting the obtained partial NBT nanotube and AAO template composite structure into 3ml of 5 wt% phosphoric acid solution to corrode for 7 h;
(2) sucking the supernatant obtained in the step (1) by using a rubber head dropper, and then washing the AAO template containing the NBT nanotube for multiple times by using deionized water until the AAO template is neutral;
(3) and placing the AAO template in a constant-temperature drying oven at 60 ℃ for heat preservation for 1 h. Then naturally cooling to room temperature;
(4) the microstructure of the NBT nanotube array was tested using a scanning electron microscope (SEM, MIRA3LMU, tesken, czech).
The method for testing the piezoelectric performance and the domain state evolution of the single NBT nanotube comprises the following steps:
(1) placing the obtained part of the NBT nanotube and AAO template composite structure in a 10 wt% NaOH solution for corrosion for 2h, then adding absolute ethyl alcohol for cleaning, and standing for 12 h;
(2) sucking the supernatant obtained in the step (1) by using a rubber head dropper, and repeating the step (1) for three times to obtain a suspension containing the NBT nanotube;
(3) adding absolute ethyl alcohol into the suspension obtained in the step (2), and standing for 10 hours;
(4) sucking the supernatant by using a rubber head dropper, and repeating the step (3) for three times to obtain a relatively pure NBT nanotube suspension;
(5) taking a small amount of NBT nanotube suspension obtained in the step (4) by using a rubber head dropper, and placing the NBT nanotube suspension in Pt/Ti/SiO2On a Si substrate, placing the substrate in a vacuum drying oven at 50 ℃ for drying for 5 min;
(6) placing the substrate obtained in the step (5) in an annealing furnace, setting the sintering temperature at 700 ℃, heating at the rate of 5 ℃/min, keeping the temperature for 2h after heating to 700 ℃, and then naturally cooling to room temperature;
(7) the piezoelectric properties and domain evolution of NBT nanotubes were tested using a contact mode using a Piezoelectric Force Microscope (PFM) module in an atomic force microscope (AFM, MFP-3D Infinity, arylum Research).
Comparative example 1:
a preparation method of an NBT nanotube array comprises the following steps:
the method comprises the following steps: preparing NBT precursor solution
(1) Weigh 1.078g Bi (NO)3)3·5H2O dissolved in 15mL CH3OCH2CH2OH neutralizing and magnetically stirringIs solution A, the mass volume ratio of which is 0.072 g/mL;
(2) weigh 0.166g CH3COONa dissolved in 3mL CH3COOH is stirred evenly and is marked as a B solution, and the mass-volume ratio of the B solution is 0.055 g/mL;
(3) dropwise adding the solution B into the solution A, and magnetically stirring the obtained mixed solution for 20 min;
(4) 1.375g of Ti (OC) was added to the resulting mixed solution, respectively4H9)4、1mL CH3COCH2COCH3Stirring for 2h at room temperature to obtain a uniformly mixed precursor solution, which is shown in figure 1 illustrated by the attached drawings of the invention;
CH as mentioned above3COONa、Bi(NO3)3Aqueous solution, Ti (OC)4H9)4The amount of the aqueous solution is as CH3COONa：Bi(NO3)3：Ti(OC4H9)4The molar ratio of (A) to (B) is 1:1: 2;
step two: synthesis of NBT nanotube array by template method
(1) Soaking an AAO template (the aperture of the template is 200nm) in the precursor solution obtained in the step one for 5 days, and filling NBT sol into holes of the template;
(2) taking out the AAO template, wiping the surface of the template by using propanol, and drying for 3min in a constant-temperature drying oven at 120 ℃;
(3) placing the product obtained in the step (2) in a muffle furnace for annealing treatment, wherein the annealing process parameters are as follows: heating to 175 deg.C at room temperature, and maintaining for 10 min; then heating to 400 ℃, and preserving the heat for 10 min; continuously heating to 700 ℃, and keeping the temperature for 1h, wherein the heating rate is 5 ℃/min; finally, naturally cooling to room temperature along with the furnace temperature;
(4) corroding the product obtained in the step (3) with 5 wt% phosphoric acid to obtain the NBT nanotube array.
Comparative example 2:
a preparation method of an NBT nanotube array comprises the following steps:
only changing the filling mode of the step two (1) into a suction filtration method: soaking an AAO template (with the template aperture of 200nm) in the precursor solution obtained in the step one for 15min, filling NBT sol into holes of the AAO template by using a suction filtration device, repeating the steps for 3-5 times, and obtaining the NBT nanotube array by repeating the steps as in the comparative example 1.
Comparative example 3:
a preparation method of an NBT nanotube array comprises the following steps:
only changing the filling mode of the step two (1) into a spin coating method: firstly, fixing an AAO template (the aperture of the template is 200nm) on the upper surface of a Si sheet by using a polyimide adhesive tape, and placing the lower surface of the Si sheet on a spin-coating platform; then sucking a small amount of NBT sol on the AAO template by using a rubber head dropper, and standing for 20 min; and rotating at a low rotating speed of 500r/min for 20s, rotating at a high rotating speed of 3000r/min for 60s, repeating the steps for 3-5 times, and obtaining the NBT nanotube array by the same steps as the comparative example 1.
Example 1:
the method comprises the following steps: preparing NBT precursor solution
(1) Weigh 1.078g Bi (NO)3)3·5H2O dissolved in 15mL CH3OCH2CH2OH is added and magnetically stirred, and is marked as solution A, and the mass volume ratio of the solution A is 0.072 g/mL;
(2) weigh 0.166g CH3COONa is dissolved in 3mLCH3COOH is stirred evenly and is marked as a B solution, and the mass-volume ratio of the B solution is 0.055 g/mL;
(3) dropwise adding the solution B into the solution A, and magnetically stirring the obtained mixed solution for 20 min;
(4) 1.375g of Ti (OC) was added to the resulting mixed solution, respectively4H9)4、1mL CH3COCH2COCH3Stirring for 2h at room temperature to obtain a uniformly mixed precursor solution, which is shown in figure 1 illustrated by the attached drawings of the invention;
CH as mentioned above3COONa、Bi(NO3)3Aqueous solution, Ti (OC)4H9)4The amount of the aqueous solution is as CH3COONa：Bi(NO3)3：Ti(OC4H9)4The molar ratio of (A) to (B) is 1:1: 2;
step two: drawing rotary
Soaking an AAO template (the aperture of the template is 200nm) in the precursor solution obtained in the step one for 10 min; then using a suction filtration device to ensure that the negative pressure is less than 10-1Filling the NBT sol into holes of the AAO template under Pa; then, firstly, placing the AAO template fixed on the Si wafer on a spin coating platform, rotating at a low rotating speed of 500r/min for 10s and at a high rotating speed of 3000r/min for 60s, taking out the AAO template, wiping the surface of the template by using propanol, drying for 3min in a constant-temperature drying oven at 120 ℃, and repeating the steps for 5 times;
and (3) placing the product obtained in the step two in a muffle furnace for annealing treatment, wherein the annealing process parameters are as follows: heating to 175 deg.C at room temperature, and maintaining for 10 min; then heating to 400 ℃, and preserving the heat for 10 min; continuously heating to 700 ℃, and keeping the temperature for 1h, wherein the heating rate is 5 ℃/min; finally, naturally cooling to room temperature along with the furnace temperature; finally, the NBT nanotube array with high filling rate, large length-diameter ratio and accurately controlled wall thickness is prepared.
Example 2:
a preparation method of an NBT nanotube array comprises the following steps:
other conditions are the same as the example 1, only the AAO template (the aperture of the template is 110nm) is selected in the second step, and the steps of suction filtration and spin coating are repeated for 4 times, so that the NBT nanotube array with the diameter of about 110nm is finally obtained.
Example 3:
a preparation method of an NBT nanotube array comprises the following steps:
other conditions are the same as the embodiment 1, only the AAO template (the aperture of the template is 30nm) is selected in the second step, the steps of repeated suction filtration and spin coating are 2 times, wherein after the first repeated step is finished, the AAO template containing the sol is placed in a muffle furnace for annealing treatment, and the annealing process parameters are as follows: heating to 175 deg.C at room temperature, and maintaining for 2 min; then the temperature is raised to 400 ℃, and the temperature is preserved for 5min, and finally the NBT nanotube array with the diameter of about 30nm is obtained.
In summary, the invention provides a sodium bismuth titanate nanotube with high piezoelectric coefficient and a preparation method thereof, and finds out a preparation method of an NBT nanotube array with high filling rate, large length-diameter ratio and accurately controlled wall thickness by comparing the formation mechanisms of preparing the NBT nanotube array in different filling modes: firstly, a suction filtration device is used, and the filling rate of sol in the AAO template is improved by utilizing the negative pressure of atmosphere, the gravity of the sol and the adsorption force of template holes; and then, a spin coating device is used, mechanical rotation is utilized to generate centrifugal force on the sol, and the rotation frequency is adjusted so as to achieve uniform wall thickness and accurately control the wall thickness. The interior of the piezoelectric ceramic shows a stripe domain structure with different contrasts and a unique hollow tubular structure, so that a high piezoelectric coefficient is obtained.

Claims (3)

1. A preparation method of a sodium bismuth titanate nanotube is characterized by comprising the following steps: dropwise adding a bismuth source-containing solution into a sodium source-containing solution to obtain a bismuth source-and sodium source-containing solution, then adding a titanium source into the bismuth source-and sodium source-containing solution to obtain a mixed solution, adding a stabilizer into the mixed solution to obtain a sodium bismuth titanate precursor solution, then carrying out suction filtration and filling on the sodium bismuth titanate precursor solution in a template, carrying out spin coating for more than 2 times to enable sol filled in the template to form a sol tube with uniform wall thickness in the template, and finally drying, annealing and corroding the template filled with the sodium bismuth titanate precursor solution to obtain the sodium bismuth titanate nanotube;
the bismuth source is bismuth nitrate, the solid-liquid mass volume ratio of the bismuth source to the solvent in the bismuth source-containing solution is 0.06-0.08 g:1mL, and the solvent is ethylene glycol monomethyl ether;
the sodium source is sodium acetate, the solid-liquid mass volume ratio of the sodium source to the solvent in the solution containing the sodium source is 0.05-0.06 g:1mL, and the solvent is glacial acetic acid;
the titanium source is titanate;
in the mixed solution, Na, Bi and Ti =1: 1-1.1: 2-2.1;
the stabilizer is acetylacetone, and the volume fraction of the stabilizer in the bismuth sodium titanate precursor solution is 3-6 vol%;
during the suction filtration, the negative pressure is less than 10-1Pa；
The spin coating process comprises the steps of firstly adopting the speed of 300-;
the annealing process parameters are as follows: firstly heating to 170 ℃ and 180 ℃, and preserving heat for 8-12 min; then heating to 380 ℃ and 420 ℃, and preserving the heat for 10-20 min; then the temperature is raised to 680 ℃ and 720 ℃, and the temperature is kept for 45-90 min; the heating rates are controlled to be 4-6 ℃/min;
the sodium bismuth titanate nanotube has a stripe domain structure, the stripe domains are alternately arranged along the length direction of the sodium bismuth titanate nanotube, and the width of the stripe domains is 10-50 nm;
the length-diameter ratio of the bismuth sodium titanate nanotube is 100-1000; the wall thickness of the sodium bismuth titanate nanotube is 10-35 nm.
2. The method for preparing sodium bismuth titanate nanotubes according to claim 1, which is characterized in that: the corrosive liquid used for corrosion is phosphoric acid solution with the mass fraction of 3-8wt%, and the corrosion time is 6.5-7.5 h.
3. The method for preparing sodium bismuth titanate nanotubes according to claim 1, which is characterized in that: the length of the sodium bismuth titanate nanotube is 5-30 mu m, and the diameter of the sodium bismuth titanate nanotube is 30-200 nm.
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"钛酸铋钠一维纳米材料的制备及性能研究";夏华婷;《中国优秀硕士学位论文全文数据库（电子期刊）》;20130715;B020-161，正文第18、27、29-30页 *
"阳极氧化铝模板表面自组织条纹的形成";刘虹雯等;《物理学报》;20040229;第 53 卷(第 2 期);第659页左栏第1段和右栏第1段 *

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