A PZT-based textured piezoelectric ceramic, a phase-change assisted polarization preparation method and application thereof

Abstract

The application discloses a PZT-based textured piezoelectric ceramic and a phase transition assisted polarization preparation method and application thereof, and belongs to the technical field of piezoelectric materials. The preparation method comprises the following steps: preparing PMeN-PZT matrix powder; preparing a textured piezoelectric ceramic; and sequentially polishing the textured piezoelectric ceramic, sintering silver electrodes and performing phase transition assisted polarization to obtain the PZT-based textured piezoelectric ceramic; wherein the phase transition assisted polarization step is: heating the textured piezoelectric ceramic after sintering silver electrodes to a polarization temperature, the polarization temperature is higher than the trigonal-tetragonal phase transition temperature and lower than the Curie temperature, and the polarization is performed under a polarization electric field of 300 V / mm-1000 V / mm, then the polarization is naturally cooled to room temperature, and the electric field is removed. The technical problems of low piezoelectric / electromechanical / dielectric performance caused by insufficient polarization in traditional heating polarization and the technical problem that piezoelectric materials are difficult to have high piezoelectric performance and high Curie temperature at the same time are solved.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric materials technology, specifically relating to a lead zirconate titanate (PZT) based textured piezoelectric ceramic and its phase change-assisted polarization preparation method and application. Background Technology

[0002] Piezoelectric materials are functional ceramic materials that can convert mechanical energy and electrical energy into each other. They are widely used in ultrasonic transducers, non-destructive testing, ultrasonic motors, high-precision displacement control, and underwater acoustic detection. Common piezoelectric materials are mainly classified into three types: traditional ordinary piezoelectric ceramics, single-crystal ceramics, and textured piezoelectric ceramics. Textured piezoelectric ceramics, produced through a specific process that orients ceramic grains, combine the advantages of traditional ceramics and single-crystal ceramics. They can achieve piezoelectric properties and electromechanical coupling coefficients close to those of single-crystal ceramics through simple processes, and can be fabricated at low cost with high compositional uniformity, as well as heterogeneous and conformal fabrication. Therefore, they are currently a key research focus for high-performance piezoelectric ceramics.

[0003] Textured piezoelectric ceramics must be polarized to exhibit piezoelectric properties. Before polarization, the ferroelectric domains in the material have an equal probability of orientation in all directions, and do not exhibit piezoelectricity. During polarization, under the action of a DC electric field, the ferroelectric domains can be oriented along the direction of the electric field, thus giving the material piezoelectricity. The traditionally used polarization method for lead zirconate titanate (PZT)-based textured piezoelectric ceramics is conventional oil bath heating polarization. This involves placing the sample to be polarized in silicone oil, heating it to 120℃~140℃, and then applying a DC electric field of 3kV / cm~5kV / cm to both ends of the sample and holding it at that temperature for 10min~30min, so that the domains align as much as possible along the direction of the external electric field. Although this method has the advantages of simple equipment and convenient operation, it reveals its fundamental limitations when it comes to achieving full polarization of high-performance ceramics. First, the polarization temperature is difficult to increase effectively due to the boiling point of silicone oil, which limits the promoting effect of thermal activation on domain flipping. Meanwhile, as the oil temperature increases, the sample's conductivity increases, leading to a significant decrease in the breakdown field strength, making it highly susceptible to breakdown before reaching saturation polarization. This contradiction is particularly pronounced for large-sized or high-conductivity samples: on the one hand, extremely high voltages are required to drive polarization; on the other hand, conductive channels easily form inside the sample under a strong electric field, leading to polarization failure or even sample damage. Therefore, traditional oil bath polarization methods struggle to achieve sufficient and uniform polarization in complex samples, directly limiting further improvements in the material's piezoelectric, electromechanical, and dielectric properties, and making it difficult to simultaneously achieve a high piezoelectric coefficient at the intrinsic level of the material. d 33 ) and high Curie temperature T C The bottleneck of ) is further exacerbated in terms of process technology. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a PZT-based textured piezoelectric ceramic and its phase change-assisted polarization preparation method and application, so as to solve the technical problems of low piezoelectric / electromechanical / dielectric properties caused by insufficient polarization in traditional heating polarization, as well as the technical problem that it is difficult to obtain both high piezoelectric properties and high Curie temperature in piezoelectric materials.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics, comprising the following steps:

[0007] Preparation of PMeN-PZT matrix powder;

[0008] Textured piezoelectric ceramics were prepared by tape casting using PMeN-PZT matrix powder and sheet-like microcrystalline templates.

[0009] The textured piezoelectric ceramic was sequentially polished, sintered with silver electrodes, and subjected to phase change-assisted polarization to obtain the PZT-based textured piezoelectric ceramic.

[0010] The phase change-assisted polarization step involves heating the textured piezoelectric ceramic after the silver-infiltrated electrode has been sintered to a polarization temperature, wherein the polarization temperature is between the three sides of the textured piezoelectric ceramic. Between the tetragonal phase transition temperature and the Curie temperature, the material is kept at a polarization electric field of 300V / mm to 1000V / mm, then naturally cooled to room temperature, and the electric field is removed.

[0011] In one embodiment, the process for preparing the PMeN-PZT matrix powder is as follows:

[0012] According to A-doped (1-xy)Pb(Me) 1 / 2 Nb 1 / 2 The stoichiometric ratio of O3-yPbZrO3-xPbTiO3 is used to prepare the powder. After uniform mixing, the powder is ball-milled, dried, and pre-calcined to obtain a pre-calcined powder. The pre-calcined powder is then ball-milled and dried a second time to obtain PMeN-PZT matrix powder, wherein A is one of Sm, Mn, La, and Eu, and the doping amount of A is greater than 0 and not greater than 5 mol%; x ranges from 0.3 to 0.6; y ranges from 0.3 to 0.6, and x + y < 1; and Me is one of Yb, Mg, and In.

[0013] In one embodiment, the process of preparing the textured piezoelectric ceramic using PMeN-PZT matrix powder and a sheet-like microcrystalline template via a casting method is as follows:

[0014] The PMeN-PZT matrix powder, solvent, dispersant, binder and plasticizer are mixed and ball-milled to obtain a matrix slurry;

[0015] The matrix slurry is mixed with the sheet-like microcrystalline template to obtain a casting slurry; the casting slurry is then subjected to vacuuming, casting, drying, cutting, stacking, warm isostatic pressing, secondary cutting, glue removal, cold isostatic pressing, and sintering in sequence to obtain a textured piezoelectric ceramic.

[0016] In one embodiment, the solvent is a xylene-ethanol mixture or a xylene-methanol mixture; the dispersant is castor oil or fish oil; the binder is polyvinyl butyral; the plasticizer is a mixture of polyalkylene glycol and butyl benzyl phthalate in equal mass; the mass ratio of xylene to ethanol in the xylene-ethanol mixture is 1:(0.8~1.2); the mass ratio of xylene to methanol in the xylene-methanol mixture is 1:(0.8~1.2).

[0017] In one embodiment, the mass ratio of the PMeN-PZT matrix powder, solvent, dispersant, binder and plasticizer is 1:(0.2~0.6):(0.01~0.05):(0.02~0.06):(0.02~0.06).

[0018] In one embodiment, the molar ratio of the sheet-like microcrystalline template to the matrix slurry is w:1, where 0 < w ≤ 0.05.

[0019] In one embodiment, the sheet-like microcrystalline template is one of barium titanate seed crystals, barium zirconate titanate seed crystals, lead titanate seed crystals, and lead zirconate titanate seed crystals.

[0020] In one embodiment, the step of sintering the silver electrode is as follows: uniformly coating the two surfaces of the textured piezoelectric ceramic after polishing with silver paste, and holding it at a temperature of 500℃~850℃ for 5min~60min.

[0021] The heat preservation polarization time is 10 min to 60 min.

[0022] This invention also provides a PZT-based textured piezoelectric ceramic, prepared using the phase transition-assisted polarization method described above. The PZT-based textured piezoelectric ceramic has an A-doped (1-xy)Pb(Me) composition. 1 / 2Nb 1 / 2O3-yPbZrO3-xPbTiO3, where A is one of Sm, Mn, La and Eu, and the doping amount of A is greater than 0 and not greater than 5 mol%; x ranges from 0.3 to 0.6; y ranges from 0.3 to 0.6, and x+y<1; Me is one of Yb, Mg and In.

[0023] This invention also provides an application of PZT-based textured piezoelectric ceramics in the fabrication of ultrasonic transducers and hydrophones.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This invention provides a phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics. This method proposes for the first time a phase change-assisted polarization technique, which involves heating the textured piezoelectric ceramic to the rhombohedral-tetragonal phase transition temperature. T rt Above ) Curie temperature T C Below this temperature, a weak DC electric field (300V / mm~1000V / mm) is applied, followed by field cooling to room temperature. This method utilizes the structural instability and lattice reconstruction during the trigonal to tetragonal phase transition. When the temperature is above... T rt At this point, the material is in the tetragonal phase, and its spontaneous polarization direction is completely consistent with the direction of the applied electric field and the

[001] texture orientation of the grains, forming a single "1T" engineering domain structure. This process lays the foundation for subsequent polarization orientation. The key lies in the subsequent field cooling process: when the temperature decreases and after passing through... T rtAt point 001, a phase transition occurs in the crystal structure, transforming from a tetragonal phase to a trigonal phase. According to crystallographic relations, the

[001] polarization direction of the tetragonal phase will transform into that of the trigonal phase. <111> Directional families. Guided by an applied electric field, to minimize electrostatic and elastic energy, these newly formed trigonal domains do not distribute randomly, but spontaneously evolve into four energy-equivalent polarization variants, forming a specific "4R" engineered domain structure. It is the existence of this "4R" domain structure that makes the polarization vector form an angle of approximately 54.7° with the electric field direction, greatly promoting the ease of polarization rotation, significantly reducing the domain flipping barrier, and thus significantly improving polarization efficiency. This ultimately manifests as a breakthrough improvement in piezoelectric performance. Compared to traditional heating polarization, phase change-assisted polarization solves the problem of low piezoelectric / electromechanical / dielectric properties caused by insufficient polarization, achieving high-performance textured piezoelectric ceramics with sufficient polarization even under small electric fields. This is because traditional heating polarization is limited by the boiling point of silicone oil and the sample breakdown field strength, making it difficult to apply a sufficient electric field to achieve saturation polarization in complex compositions or large-sized samples. This results in a large number of non-180° domains being pinned and unable to flip, which is the root cause of its low piezoelectric performance. In contrast, the phase transition-assisted polarization proposed in this invention utilizes the structural softening effect and lattice reconstruction driving force during the phase transition process. When the material cools... T rt At this point, the crystal structure transforms from a tetragonal to a trigonal phase. At this time, the crystal lattice is in a highly unstable state, and the original ferroelectric domains disintegrate and reconstruct. In this state, even a weak DC electric field can effectively guide the newly generated trigonal domains to align along the direction of lowest energy, forming a highly ordered "4R" engineered domain structure. In short, traditional polarization involves "overcoming resistance" to flip domains, while this invention utilizes "phase transition kinetics" to reconstruct domains. The former requires a strong electric field, while the latter only requires a weak electric field, and the reconstructed domain structure is more regular and has higher mobility, thus fundamentally solving the problem of insufficient polarization in traditional methods. Furthermore, phase transition-assisted polarization does not change the basic chemical composition of the material (i.e., no sacrifice is made). T C Instead, it achieves this through a phase transition path of "1T→4R", while maintaining the original high... T C At the same time, a special “4R” domain structure was constructed at the microscale, which greatly improved the piezoelectric performance and solved the problem that it is difficult to achieve both high piezoelectric performance and high Curie temperature in piezoelectric materials.

[001] -PZT-based textured piezoelectric ceramics with ultra-high piezoelectric performance and ultra-high Curie temperature were obtained.

[0026] The textured piezoelectric ceramics prepared by phase change-assisted polarization according to the present invention are formed along

[001] . c Preferred grain orientation, texture exceeding 99%, Curie temperature up to 350℃, and piezoelectric constant. d 33Higher than 900 pC / N, high field piezoelectric coefficient With a value exceeding 1900 pm / V, a coercive field exceeding 10 kV / cm, and a strain as high as 0.65%, it is expected to have wide applications in fields such as ultrasonic transducers and hydrophones. Attached Figure Description

[0027] Figure 1 A schematic diagram of the process flow for conventional heating polarization and phase change-assisted polarization of the present invention;

[0028] Figure 2 This is a schematic diagram of the domain structure evolution of phase transition assisted polarization according to the present invention;

[0029] Figure 3 This is a schematic diagram of the phase change assisted polarization device used in this invention;

[0030] Figure 4 The image shows a scanning electron microscope (SEM) image of the high-performance PZT-based textured piezoelectric ceramic prepared by phase change-assisted polarization in Example 1.

[0031] Figure 5 The dielectric temperature spectrum of the high-performance PZT-based textured piezoelectric ceramic prepared by phase change-assisted polarization in Example 3 is shown.

[0032] Figure 6 X-ray diffraction (XRD) of the high-performance PZT-based textured piezoelectric ceramics prepared by phase change-assisted polarization in Examples 3 and 4. XRD (ray diffraction) plot.

[0033] Wherein: 1-High voltage power supply; 2-Box-type resistance furnace; 3-Clamping fixture. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] There is a high-temperature polarization method in the existing technology, which involves heating the piezoelectric ceramic to the Curie temperature (…). T C The temperature is increased by 10℃ to 20℃, then a weak DC electric field (typically 30V / mm to 40V / mm) is applied, followed by a cooling rate of 10℃ to 20℃. T C Next, the electric field is slowly increased to approximately 100V / mm to 300V / mm. Then, the furnace temperature is rapidly cooled to approximately 100°C, while the electric field is increased to approximately 400V / mm to 1000V / mm. The electric field is then removed below 100°C, and the sample is taken out. However, its polarization mechanism is fundamentally different from the phase change-assisted polarization method provided in this invention.

[0040] The invention provides a method for preparing high-performance PZT-based textured piezoelectric ceramics via phase change-assisted polarization. The polarization method is phase change-assisted polarization. The specific steps are as follows: the textured piezoelectric ceramic after being sintered with silver electrodes is heated to a polarization temperature, which is higher than the trigonal-tetragonal phase transition temperature and lower than the Curie temperature. The ceramic is then held in a polarization electric field of 300V / mm to 1000V / mm for 10 min to 60 min, and then naturally cooled to room temperature before the electric field is removed.

[0041] This invention provides a phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics, comprising the following steps:

[0042] 1. Preparation of PMeN-PZT matrix powder, according to the A-doped (1-xy)Pb(Me) 1 / 2Nb 1 / 2 The stoichiometric ratio of O3-yPbZrO3-xPbTiO3 was used to prepare the powder. After uniform mixing, the powder was ball-milled, dried, ground, sieved, pre-calcined, and then ground a second time to obtain pre-calcined powder. The pre-calcined powder was then ball-milled a second time, dried, ground a third time, and sieved a second time to obtain PMeN-PZT matrix powder. The specific steps are as follows:

[0043] (1) Preparation of precursor powder

[0044] Me2O3 and Nb2O5 were weighed out according to the stoichiometric ratio of MeNbO4 as raw materials. All the weighed raw materials were mixed evenly and placed into a nylon can. Zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mixture was ball-milled at a speed of 150 rpm to 300 rpm for 18 to 24 hours. The zirconia balls were separated, and the mixture obtained after ball milling was dried at 80℃ to 100℃ for 12 to 24 hours. The mixture was then ground in a mortar and passed through an 80-mesh sieve. The sieved powder was placed in an alumina crucible, covered, and calcined at 1000℃ to 1100℃ for 5 to 10 hours to synthesize MeNbO4 precursor powder.

[0045] (2) Ingredients

[0046] According to A-doped (1-xy)Pb(Me) 1 / 2 Nb 1 / 2 The stoichiometric ratio of O3-yPbZrO3-xPbTiO3 (x ranges from 0.3 to 0.6, y ranges from 0.3 to 0.6, and x + y < 1; A is Sm, Mn, La, or Eu, and the doping amount of A is greater than 0 and not greater than 5 mol%; Me is Yb, Mg, or In) is used for batching. For example, 3 mol% MnO2 doped with 0.3% Pb (Mg 1 / 3 Nb 2 / 3 The following raw materials were selected: 69.1276 g of PbO (99.9% purity), 12.4521 g of MgNb2O4 (99.9% purity), 9.3899 g of ZrO2 (99.9% purity), 8.5280 g of TiO2 (99.9% purity), and 0.8030 g of MnO2 (99% purity). All raw materials were mixed thoroughly and placed in a nylon container. Zirconia balls were used as grinding media, and anhydrous ethanol was used as the grinding medium. The mixture was ball-milled for 18-48 hours. The zirconia balls were separated, and the resulting mixture was dried at 80-100℃ for 12-24 hours. The mixture was then ground in a mortar and pestle and passed through an 80-200 mesh sieve.

[0047] (3) Pre-firing

[0048] Place the sieved raw material mixture from step (2) into an alumina crucible, compact it with an agate rod, cover it, place it in a resistance furnace, and pre-calcine it at a heating rate of 2℃ / min~10℃ / min to 750℃~950℃ for 2 hours~10 hours. Allow it to cool naturally to room temperature, remove it from the furnace, and grind it with a mortar and pestle to obtain pre-calcined powder.

[0049] (4) Secondary ball milling

[0050] The pre-calcined powder was placed in a nylon can, and zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The powder was thoroughly mixed and milled in a ball mill at a speed of 150 rpm to 300 rpm for 12 to 48 hours. The zirconia balls were separated, and the pre-calcined powder was dried at 80℃ to 100℃ for 12 to 24 hours. The powder was then ground in a mortar and passed through an 80-200 mesh sieve to obtain PMeN-PZT matrix powder.

[0051] 2. Preparation of textured piezoelectric ceramics: An organic system method is used to prepare a casting slurry. The PMeN-PZT matrix powder is ball-milled to obtain a matrix slurry. The matrix slurry is mixed with a sheet-like microcrystalline template to obtain a casting slurry. The casting slurry is then subjected to vacuuming, casting, drying, cutting, stacking, warm isostatic pressing, secondary cutting, debinding, cold isostatic pressing, and sintering in sequence to obtain the textured piezoelectric ceramic. The specific steps are as follows:

[0052] (1) Ball milling

[0053] The prepared PMeN-PZT matrix powder was placed in a ball mill jar, using zirconia balls as grinding balls, xylene-ethanol or xylene-methanol mixed solution as solvent, and castor oil or fish oil as dispersant, and ball milled for 10 to 48 hours. Then, a binder and plasticizer were added sequentially, and ball milling was continued for 10 to 48 hours to obtain a matrix slurry. The binder was polyvinyl butyral; the plasticizer was a mixture of equal masses of polyalkylene glycol and butyl benzyl phthalate. The PMeN-PZT matrix powder and the zirconia slurry were then ball milled. The mass ratio of toluene-ethanol mixed solution or xylene-methanol mixed solution is 1:(0.2~0.6), the mass ratio of xylene to ethanol in xylene-ethanol mixed solution is 1:(0.8~1.2), and the mass ratio of xylene to methanol in xylene-methanol mixed solution is 1:(0.8~1.2); the mass ratio of PMeN-PZT matrix powder, dispersant, binder and plasticizer is 1:(0.01~0.05):(0.02~0.06):(0.02~0.06).

[0054] (2) Preparation of casting slurry

[0055] The sheet-like microcrystalline template is selected according to the molar ratio w:1 between the sheet-like microcrystalline template and the matrix slurry. The sheet-like microcrystalline template is selected from one of barium titanate (BT), barium zirconate titanate (BZT), lead titanate (PT), and lead zirconate titanate (PZT), where 0 < w ≤ 0.05. The sheet-like microcrystalline template and the matrix slurry are mixed and ball-milled at a speed of 100 r / min to 300 r / min for 10 hours to 48 hours to obtain the casting slurry.

[0056] (3) Vacuuming

[0057] Under stirring conditions of 100 r / min to 300 r / min, the cast slurry is placed in a vacuum defoaming device and vacuumed for 1 hour to 12 hours to obtain a slurry with air bubbles removed.

[0058] (4) Casting

[0059] The de-bubbling slurry is cast using a casting machine at a speed of 10 cm / min to 60 cm / min. The thickness between the casting doctor blade and the base film is 50 μm to 450 μm. After casting, the film is dried for 1 to 4 hours to obtain a film sheet. The film sheet is then cut with a film cutter to obtain the cut film sheet.

[0060] (5) Overlapping

[0061] The cut membrane is vacuumed and multi-layered (20 to 30 layers), with a vacuum time of 10 to 60 seconds. The stacking machine parameters are: upper pressure table temperature 60℃ to 90℃, lower pressure table temperature 60℃ to 90℃, and pressure 5MPa to 45MPa, to obtain the stacked membrane.

[0062] (6) Warm isostatic pressing

[0063] Under pressure of 10MPa~45MPa and water temperature of 60℃~90℃, the stacked diaphragm was subjected to hot water uniform pressing for 15min~120min to obtain the hot water uniform pressing diaphragm.

[0064] (7) Cutting

[0065] The film after warm isostatic pressing was cut with a cutting machine to obtain a green sample;

[0066] (8) De-glue

[0067] The green sample after isostatic pressing was placed in a low-temperature furnace. The furnace was heated from room temperature to 550℃ to 650℃ at a heating rate of 0.1℃ / min to 0.8℃ / min. Then, the binder was removed at 550℃ to 650℃ for 0.5 hours to 10 hours. After the binder was removed, the sample was cooled to room temperature at a cooling rate of 0.1℃ / min to 0.8℃ / min to obtain the green sample after binder removal.

[0068] (9) Cold isostatic pressing

[0069] Under pressure of 150MPa~300MPa and oil temperature of room temperature, the raw blank after debinding is subjected to cold isostatic pressing for 1 minute to 30 minutes to obtain the cold isostatic pressing sample.

[0070] (10) Sintering

[0071] In an oxygen or air atmosphere, the cold isostatically pressed sample is sintered in a high-temperature furnace to develop a texture. The gas flow rate is 0.1 L / min to 2 L / min, the sintering temperature is 1000℃ to 1250℃, and the holding time is 0.25 hours to 45 hours, yielding A-doped (1-xy)Pb(Me). 1 / 2 Nb 1 / 2 O3-yPbZrO3-xPbTiO3 textured piezoelectric ceramic (A-PMeN-PZT ternary textured piezoelectric ceramic), wherein 0.3≤x≤0.6, 0.3≤y≤0.6, and x+y<1; A is Sm, Mn, La or Eu, and the doping amount of A is greater than 0 and not greater than 5mol%; Me is Yb, Mg or In; A-PMeN-PZT ternary textured piezoelectric ceramic is a trigonal phase, a tetragonal phase, or a coexistence of trigonal and tetragonal phases, along

[001] c The directional texture is all above 99%;

[0072] 3. Preparation of high-performance PMeN-PZT textured piezoelectric ceramics: The textured piezoelectric ceramics are sequentially polished, sintered with silver electrodes, and subjected to phase change-assisted polarization to obtain the high-performance PZT-based textured piezoelectric ceramics. The specific steps are as follows:

[0073] (1) Polishing

[0074] The sintered textured piezoelectric ceramic is then subjected to a process perpendicular to

[001] . c The upper and lower surfaces are polished with 600-2000 grit sandpaper, then polished with metallographic sandpaper to a thickness of 0.8mm-1.2mm, and then ultrasonically cleaned with deionized water and ethanol respectively, and dried.

[0075] (2) Burning silver-impregnated electrodes

[0076] Silver paste was uniformly coated on the two polished surfaces of the textured piezoelectric ceramic, and then placed in a resistance furnace. The temperature was maintained at 500℃~850℃ for 5min~60min to obtain A-PMeN-PZT textured piezoelectric ceramic with sintered silver electrodes.

[0077] (3) Phase transition assisted polarization

[0078] The A-PMeN-PZT textured piezoelectric ceramic with sintered silver electrodes is placed in fixture 3, and then fixture 3 is placed in box-type resistance furnace 2 and heated to the required polarization temperature. The polarization temperature is higher than the trigonal-tetragonal phase transition temperature and lower than the Curie temperature. The ceramic is held at a polarization electric field of 300V / mm to 1000V / mm for 10 min to 60 min. After natural cooling to room temperature, the voltage is removed to obtain a high-performance PZT-based textured piezoelectric ceramic.

[0079] like Figure 3 As shown, the above-mentioned phase change assisted polarization is performed using a phase change assisted polarization device, which consists of a high-voltage power supply 1, a box-type resistance furnace 2, and a clamp 3. The high-voltage power supply 1 is electrically connected to the box-type resistance furnace 2, and the clamp 3 is installed inside the box-type resistance furnace 2.

[0080] The embodiments of the present invention also provide a high-performance PZT-based textured piezoelectric ceramic prepared according to the above preparation method, which is a

[001] -PZT-based textured piezoelectric ceramic with an A-doped (1-xy)Pb(Me) composition. 1 / 2 Nb 1 / 2 O3-yPbZrO3-xPbTiO3, where A is Sm, Mn, La or Eu, and the doping amount of A is greater than 0 and not greater than 5 mol%; x ranges from 0.3 to 0.6; y ranges from 0.3 to 0.6, and x+y<1; Me is Yb, Mg or In.

[0081] Figure 1 This diagram illustrates a comparison between traditional heating polarization and phase change-assisted polarization processes. For PZT-based piezoelectric ceramics, the polarization temperature of traditional heating polarization is typically 140°C, and the polarization electric field generally needs to be greater than three times the coercive field (usually 3kV / cm~5kV / cm), followed by field cooling to room temperature. In contrast, the phase change-assisted polarization method used in this invention employs a polarization temperature higher than the trigonal-tetragonal phase transition temperature but lower than the Curie temperature, followed by the application of a weaker DC electric field (300V / mm~1000V / mm), and then field cooling to room temperature.

[0082] Figure 2 A schematic diagram illustrating the evolution of domain structures under phase transition-assisted polarization. When the temperature is above the trigonal-tetragonal phase transition temperature ( T rtWhen the material is in the tetragonal phase (T phase), the spontaneous polarization direction is... P s ), Direction of Applied Electric Field E The

[001] texture orientation of the crystal is completely consistent, forming a single "1T" engineering domain structure. During field cooling, when the temperature drops to... T rt At this point, the material undergoes a phase transition, transforming into a trigonal phase (R phase). The polarization direction changes from a single

[001] to four energy-equivalent

[001] directions. <111> The direction of polarization rotation forms a "4R" engineered domain structure that forms a certain angle with the direction of the electric field. This structure greatly promotes polarization rotation and is key to improving piezoelectric performance.

[0083] This invention provides a method for preparing high-performance PZT-based textured piezoelectric ceramics via phase change-assisted polarization, overcoming the problems of low piezoelectric / electromechanical / dielectric properties associated with traditional thermal polarization. The high-performance PZT-based textured piezoelectric ceramics obtained by this invention have a texture degree exceeding 99%, a Curie temperature of 340℃, and significantly improved electrical properties. For example, taking MnO2-doped PIN-PZT ceramics as an example, the piezoelectric performance of thermally polarized ceramics is significantly enhanced. d 33 The piezoelectric properties after phase change-assisted polarization are 709 pC / N. d 33 1035 pC / N; high-field piezoelectric coefficient with heating polarization The high-field piezoelectric coefficient after phase-change assisted polarization is 1328 pm / V. The strain is 1948 pm / V; the strain after heating polarization is 0.48%, and the strain after phase change-assisted polarization is 0.67%. Since it is difficult to simultaneously achieve high piezoelectric performance and a high Curie temperature, high piezoelectric performance often corresponds to a low Curie temperature. This invention employs phase change-assisted polarization to significantly improve polarization efficiency, thus maintaining a high Curie temperature while substantially improving piezoelectric performance, thereby enhancing the overall performance of the textured piezoelectric ceramic. d 33 T C It is far superior to other textured piezoelectric ceramics.

[0084] Embodiments of the present invention also provide the application of the above-mentioned high-performance PZT-based textured piezoelectric ceramics in the fabrication of ultrasonic transducers and hydrophones.

[0085] In the following embodiments and comparative examples of the present invention, the preparation methods of barium titanate BT seed crystals, barium zirconate titanate BZT seed crystals, lead titanate PT seed crystals, and lead zirconate titanate PZT seed crystals are all molten salt method and topological chemical microcrystal conversion method: the first step is to synthesize the corresponding precursor Bi4Ti3O using the molten salt method. 12 and PbBi4Ti4O 15 The second step involves synthesizing the corresponding barium titanate BT seed crystals, barium zirconate titanate BZT seed crystals, lead titanate PT seed crystals, and lead zirconate titanate PZT seed crystals using a topological chemical conversion method.

[0086] The relevant chemical reaction formulas are as follows:

[0087] Barium titanate BT seed crystals:

[0088] 2Bi₂O₃ + 3TiO₂ → Bi₄Ti₃O 12 Bi4Ti3O 12 +3BaCO3→3BaTiO3+2Bi2O3+3CO2;

[0089] Barium zirconate BZT seed crystals:

[0090] 2Bi₂O₃ + 3TiO₂ → Bi₄Ti₃O 12 ;

[0091] (1-x)Bi4Ti3O 12 +3BaCO3+3xZrO2→3Ba(Zr x Ti 1-x )O3+2(1-x)Bi2O3+3CO2;

[0092] Lead titanate PT seed crystals:

[0093] PbO + 2Bi₂O₃ + 4TiO₂ → PbBi₄Ti₄O 15 PbBi4Ti4O 15 +3PbO→4PbTiO3+2Bi2O3;

[0094] Lead zirconate titanate (PZT) seed crystals:

[0095] PbO + 2Bi₂O₃ + 4TiO₂ → PbBi₄Ti₄O 15 ;

[0096] (1-x)PbBi4Ti4O 15 +(3+x)PbO+4xZrO2→4Pb(Zr x Ti 1-x )O3+2(1-x)Bi2O3.

[0097] It should be noted that any aspects not described in detail in this invention are conventional practices in the art and are not the focus of this invention. For example, methods for preparing seed crystals using the molten salt method and the topological chemical microcrystal conversion method are both conventional methods in the art.

[0098] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0099] Unless otherwise specified, the room temperature in the following examples is 25±2℃.

[0100] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0101] Example 1

[0102] A phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics, comprising the following steps:

[0103] 1. Preparation of Mn-doped PIN-PZT matrix powder:

[0104] (1) Preparation of precursor powder

[0105] According to the stoichiometric ratio of InNbO4, 51.1391 g of In2O3 and 48.9610 g of Nb2O5 were weighed as raw materials. All the weighed raw materials were mixed evenly and placed in a nylon jar. Zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled at 250 rpm for 24 hours. The zirconia balls were separated, and the ball-milled mixture was dried at 80℃ for 24 hours. It was then ground in a mortar for 30 minutes and passed through an 80-mesh sieve. The sieved powder was placed in an alumina crucible, covered, and calcined at 1100℃ for 10 hours to synthesize InNbO4 precursor powder.

[0106] (2) Ingredients

[0107] Based on 0.25 mol% MnO2 doped with 0.2 Pb(In) 1 / 2 Nb 1 / 2The following raw materials were prepared for the preparation of O3-0.4PbZrO3-0.4PbTiO3: 67.3758g of PbO with a purity of 99.9%, 48.2023g of InNbO with a purity of 99.9%, 14.8652g of ZrO2 with a purity of 99.9%, 9.6434g of TiO2 with a purity of 99.9%, and 0.1324g of MnO2 with a purity of 99%. All raw materials were mixed thoroughly and placed in a nylon container. Zirconia balls were used as grinding media, and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled for 24 hours (at 250 rpm). The zirconia balls were separated, and the ball-milled mixture was dried at 80℃ for 24 hours. It was then ground in a mortar for 30 minutes and passed through a 200-mesh sieve.

[0108] (3) Pre-firing

[0109] The raw material mixture after passing through a 200-mesh sieve in step (2) is placed in an alumina crucible and compacted with an agate rod (compacted density of 1.5 g / cm³). 3 Cover the contents, place them in an electric resistance furnace, and pre-fire at 950°C for 10 hours with a heating rate of 5°C / min. Let them cool naturally to room temperature, remove them from the furnace, and grind them in a mortar for 10 minutes to obtain pre-fired powder.

[0110] (4) Secondary ball milling

[0111] The pre-calcined powder obtained in step (3) was loaded into a nylon can, and zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to pre-calcined powder was 1:1.2. The mixture was ball-milled at a speed of 250 rpm for 48 hours. The zirconia balls were separated, and the pre-calcined powder was dried at 80°C for 24 hours. It was then ground in a mortar for 10 minutes and passed through a 200-mesh sieve to obtain Mn-doped PIN-PZT matrix powder.

[0112] 2. Preparation of Mn-doped PIN-PZT textured piezoelectric ceramics:

[0113] (1) Ball milling

[0114] The Mn-doped PIN-PZT matrix powder prepared above was placed in a ball mill jar, using zirconia balls as milling balls, a xylene-ethanol mixture (xylene and ethanol in a mass ratio of 1:1) as solvent, and castor oil as dispersant, and milled for 24 hours. Then, a binder (polyvinyl butyral) and a plasticizer (a mixture of polyalkylene glycol and butyl benzyl phthalate in a mass ratio of 1:1) were added sequentially, and milled for 24 hours to obtain a matrix slurry. In this embodiment, the mass ratio of Mn-doped PIN-PZT matrix powder to xylene-ethanol mixture was 1:0.56, the mass ratio of Mn-doped PIN-PZT matrix powder to dispersant was 1:0.01, the mass ratio of Mn-doped PIN-PZT matrix powder to binder was 1:0.04, and the mass ratio of Mn-doped PIN-PZT matrix powder to plasticizer was 1:0.04.

[0115] (2) Preparation of casting slurry

[0116] Select a sheet-like microcrystalline template according to a molar ratio of 0.05:1 to the matrix slurry, wherein the sheet-like microcrystalline template is a barium titanate BT seed crystal; mix the sheet-like microcrystalline template with the matrix slurry in step (1) and ball mill it, and stir it on a magnetic stirrer for 24 hours (speed is 200r / min) to obtain the casting slurry;

[0117] (3) Vacuuming

[0118] Under stirring conditions of 200 r / min, the above cast slurry was placed in a vacuum degassing device and vacuumed for 4 hours to obtain a slurry with air bubbles removed.

[0119] (4) Casting

[0120] The above-mentioned de-bubbled slurry was cast using a casting machine at a casting speed of 10 cm / min. The thickness between the casting doctor blade and the base film was 150 μm. After casting, the film was dried for 2 hours to obtain a film sheet. The film sheet was then cut with a film cutter to obtain a 5 cm × 5 cm film sheet.

[0121] (5) Overlapping

[0122] The cut membrane is vacuumed and then multi-layered (25 layers) to obtain the laminated membrane. The vacuuming time is 30 seconds. The laminator parameters are: upper pressure table temperature 75℃, lower pressure table temperature 75℃, and pressure 20MPa.

[0123] (6) Warm isostatic pressing

[0124] Under a pressure of 20 MPa and a water temperature of 75 °C, the stacked diaphragm was subjected to hot water uniform pressing for 30 minutes to obtain the hot water uniform pressing diaphragm.

[0125] (7) Cutting

[0126] The isostatically pressed membrane was cut with a cutting machine to obtain a 2.5cm×2.5cm blank sample;

[0127] (8) De-glue

[0128] The green sample after isostatic pressing was placed in a low-temperature furnace. The furnace was heated from room temperature to 650°C at a heating rate of 0.1°C / min. Then, the binder was removed at 650°C for 10 hours. After the binder was removed, the temperature was lowered to room temperature at a cooling rate of 0.3°C / min to obtain the green sample after binder removal.

[0129] (9) Cold isostatic pressing

[0130] Under the conditions of pressure of 300MPa and oil temperature of room temperature, the raw blank after debinding was subjected to cold isostatic pressing for 30 minutes to obtain the cold isostatic pressing sample.

[0131] (10) Sintering

[0132] In an oxygen atmosphere, the cold isostatically pressed sample was sintered in a high-temperature furnace with a gas flow rate of 0.1 L / min, a sintering temperature of 1250 °C, and a holding time of 20 hours, yielding Mn-doped PIN-PZT textured piezoelectric ceramics with a composition of 0.25 mol% MnO2-0.2 Pb(In). 1 / 2 Nb 1 / 2 The textured piezoelectric ceramic is composed of trigonal and tetragonal phases, with the following structure:

[001] c The directional texture is 99%;

[0133] 3. Preparation of high-performance PZT-based textured piezoelectric ceramics (which are Mn-doped PIN-PZT textured piezoelectric ceramics with high electrical performance):

[0134] (1) Polishing

[0135] The sintered textured piezoelectric ceramic is then subjected to a process perpendicular to

[001] . c The upper and lower surfaces were polished with 2000-grit sandpaper, then polished with metallographic sandpaper to a thickness of 1.2mm, and then ultrasonically cleaned with deionized water and ethanol respectively, and dried.

[0136] (2) Burning silver-impregnated electrodes

[0137] A 0.02 mm thick layer of silver paste was coated on the upper and lower surfaces of the polished textured piezoelectric ceramic. The ceramic was then placed in a resistance furnace and held at 600 °C for 30 min, followed by natural cooling to room temperature. This yielded a 0.25 mol% MnO2-doped 0.2Pb(In) electrode after sintering and infiltration. 1 / 2 Nb 1 / 2 O3-0.4PbZrO3-0.4PbTiO3 textured piezoelectric ceramics;

[0138] (3) Polarization

[0139] Phase transition assisted polarization: such as Figure 3 As shown, 0.25 mol% MnO2-doped 0.2 Pb (In) electrode after sintering and silver infiltration is used. 1 / 2Nb 1 / 2 The O3-0.4PbZrO3-0.4PbTiO3 textured piezoelectric ceramic was placed in fixture 3, and then fixture 3 was placed in box-type resistance furnace 2 and heated to the required polarization temperature (270℃). The polarization electric field was 500V / mm, and the polarization time was 60min. After natural cooling to room temperature, the electric field was removed, and a high-performance PZT-based textured piezoelectric ceramic was obtained. The SEM image of the high-performance PZT-based textured piezoelectric ceramic prepared by phase change-assisted polarization in this embodiment is shown below. Figure 4 As shown, the seed crystals are neatly arranged in the matrix and induce the epitaxial growth of matrix grains, exhibiting strong orientation, texture, and dense microstructure.

[0140] The high-performance PZT-based textured piezoelectric ceramic prepared in this embodiment is along

[001] . c The directional texture is 99%, the Curie temperature is 357℃, the trigonal-tetragonal phase transition temperature is 230℃, and the electrical properties are as follows: piezoelectric constant after phase transition assisted polarization. d 33 With a piezoelectric coefficient of 1035 pC / N (higher than 900 pC / N), it has a high field piezoelectricity. The value is 1948 pm / V (higher than 1900 pm / V), the coercive field is 10.2 kV / cm, and the strain is 0.67%.

[0141] Comparative Example 1

[0142] Same as Example 1, except that step (3) of preparing high-performance PZT-based textured piezoelectric ceramics uses conventional heating polarization, the specific process of which is as follows: 0.25 mol% MnO2-doped 0.2Pb(In) electrode after sintering and infiltrating silver electrode is heated and infiltrated with silver. 1 / 2 Nb 1 / 2 O3-0.4PbZrO3-0.4PbTiO3 textured piezoelectric ceramics were placed in silicone oil, and a DC electric field was used to propel the textured piezoelectric ceramics along

[001] . cDirectional polarization was applied at a polarization temperature of 140℃, a polarization voltage of 40 kV / cm, and a polarization voltage holding time of 60 minutes, yielding 0.2 Pb(In) doped with the chemical formula 0.25 mol% MnO2. 1 / 2 Nb 1 / 2 Textured piezoelectric ceramics of O3-0.4PbZrO3-0.4PbTiO3.

[0143] The textured piezoelectric ceramic prepared by conventional heating polarization in this comparative example has a texture degree of 99%, a Curie temperature of 357℃, and the following electrical properties: piezoelectric constant. d 33 It has a piezoelectric coefficient of 709 pC / N and a high field piezoelectricity. The coefficient of performance is 1328 pm / V, the coercive field is 10.2 kV / cm, and the strain is 0.48%.

[0144] As can be seen from Example 1 and Comparative Example 1, the textured piezoelectric ceramics prepared by the method of the present invention exhibit superior strain and overall performance. d 33 T C Its value is much higher than that of other textured piezoelectric ceramics currently available.

[0145] Example 2

[0146] A phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics, comprising the following steps:

[0147] 1. Preparation of La-doped PYN-PZT matrix powder:

[0148] (1) Preparation of precursor powder

[0149] According to the stoichiometric ratio of YbNbO4, 59.7804 g of Yb2O3 and 40.3197 g of Nb2O5 were weighed as raw materials. All the weighed raw materials were mixed evenly and placed in a nylon jar. Zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled at 300 rpm for 18 hours. The zirconia balls were separated, and the ball-milled mixture was dried at 90℃ for 20 hours. It was then ground in a mortar and pestle for 30 minutes and passed through an 80-mesh sieve. The sieved powder was placed in an alumina crucible, covered, and calcined at 1000℃ for 8 hours to synthesize YbNbO4 precursor powder.

[0150] (2) Ingredients

[0151] Based on 1 mol% La2O3 doping of 0.19Pb(Yb) 1 / 2 Nb 1 / 2The following ingredients were prepared for the preparation of PbO3-0.51PbZrO3-0.3PbTiO3: 65.4529g of PbO (99.9% purity), 49.1922g of YbNbO (99.9% purity), 18.4288g of ZrO2 (99.9% purity), 7.0262g of TiO2 (99.9% purity), and 0.4749g of La2O3 (99.9% purity) were weighed out as raw materials. All raw materials were mixed thoroughly and placed in a nylon container. Zirconia balls were used as grinding media, and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled for 18 hours (250 rpm). The zirconia balls were separated, and the ball-milled mixture was dried at 100℃ for 12 hours. It was then ground in a mortar for 30 minutes and passed through a 200-mesh sieve.

[0152] (3) Pre-firing

[0153] The raw material mixture after passing through a 200-mesh sieve in step (2) is placed in an alumina crucible and compacted with an agate rod (compacted density of 1.5 g / cm³). 3 Cover the contents, place them in a resistance furnace, and pre-fire at 750°C for 5 hours at a heating rate of 5°C / min. Let them cool naturally to room temperature, remove them from the furnace, and grind them in a mortar for 10 minutes to obtain pre-fired powder.

[0154] (4) Secondary ball milling

[0155] The pre-calcined powder obtained in step (3) was loaded into a nylon can, and zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to pre-calcined powder was 1:1.2. The mixture was ball-milled at a speed of 150 rpm for 24 hours. The zirconia balls were separated, and the pre-calcined powder was dried at 80°C for 24 hours. It was then ground in a mortar for 10 minutes and passed through a 200-mesh sieve to obtain La-doped PYN-PZT matrix powder.

[0156] 2. Preparation of La-doped PYN-PZT textured piezoelectric ceramics:

[0157] (1) Ball milling

[0158] The La-doped PYN-PZT matrix powder prepared above was placed in a ball mill jar, using zirconia balls as milling balls, a xylene-methanol mixture (xylene and methanol mass ratio of 1:0.8) as solvent, and fish oil as dispersant, and milled for 10 hours. Then, a binder (polyvinyl butyral) and a plasticizer (a mixture of polyalkylene glycol and butyl benzyl phthalate, mass ratio of 1:1) were added sequentially, and milled for 24 hours to obtain a matrix slurry. In this embodiment, the mass ratio of La-doped PYN-PZT matrix powder to xylene-methanol mixture was 1:0.2, the mass ratio of La-doped PYN-PZT matrix powder to dispersant was 1:0.05, the mass ratio of La-doped PYN-PZT matrix powder to binder was 1:0.02, and the mass ratio of La-doped PYN-PZT matrix powder to plasticizer was 1:0.02.

[0159] (2) Preparation of casting slurry

[0160] Select a sheet-like microcrystalline template according to a molar ratio of 0.03:1 to the matrix slurry, wherein the sheet-like microcrystalline template is a barium zirconate BZT seed crystal; mix the sheet-like microcrystalline template with the matrix slurry in step (1) and ball mill it, and stir it on a magnetic stirrer for 48 hours (speed is 100r / min) to obtain the casting slurry;

[0161] (3) Vacuuming

[0162] Under stirring conditions of 300 r / min, the above cast slurry was placed in a vacuum degassing device and vacuumed for 8 hours to obtain a slurry with air bubbles removed.

[0163] (4) Casting

[0164] The above-mentioned de-bubbled slurry was cast using a casting machine at a casting speed of 30 cm / min and a thickness of 300 μm between the casting doctor blade and the base film. After casting, the film was dried for 4 hours to obtain a film sheet. The film sheet was then cut with a film cutter to obtain a 5 cm × 5 cm film sheet.

[0165] (5) Overlapping

[0166] The cut membrane is vacuumed and then multi-layered (20 layers) to obtain the laminated membrane. The vacuuming time is 60 seconds, and the laminating machine parameters are: upper pressure table temperature 60℃, lower pressure table temperature 60℃, and pressure 45MPa.

[0167] (6) Warm isostatic pressing

[0168] Under a pressure of 45 MPa and a water temperature of 60 °C, the stacked diaphragm was subjected to hot water uniform pressing for 30 minutes to obtain the hot water uniform pressing diaphragm.

[0169] (7) Cutting

[0170] The isostatically pressed membrane was cut with a cutting machine to obtain a 2.5cm×2.5cm blank sample;

[0171] (8) De-glue

[0172] The green sample after isostatic pressing was placed in a low-temperature furnace. The furnace was heated from room temperature to 600℃ at a heating rate of 0.5℃ / min. Then, the binder was removed at 600℃ for 3 hours. After the binder was removed, the temperature was lowered to room temperature at a cooling rate of 0.5℃ / min to obtain the green sample after binder removal.

[0173] (9) Cold isostatic pressing

[0174] Under the conditions of a pressure of 200 MPa and an oil temperature of room temperature, the raw blank after debinding was subjected to cold isostatic pressing for 20 minutes to obtain the cold isostatic pressing sample.

[0175] (10) Sintering

[0176] In an oxygen atmosphere, the cold isostatically pressed sample was sintered in a high-temperature furnace with a gas flow rate of 1 L / min, a sintering temperature of 1050 °C, and a holding time of 35 hours to obtain La-doped PYN-PZT textured piezoelectric ceramics with a composition of 1 mol% La₂O₃-0.19Pb(Yb). 1 / 2 Nb 1 / 2 The textured piezoelectric ceramic is O3-0.51PbZrO3-0.3PbTiO3, wherein the textured piezoelectric ceramic is a trigonal phase, along

[001] c The directional texture degree is 99.2%;

[0177] 3. Preparation of high-performance PZT-based textured piezoelectric ceramics (which are La-doped PYN-PZT textured piezoelectric ceramics with high electrical performance):

[0178] (1) Polishing

[0179] The sintered textured piezoelectric ceramic is then subjected to a process perpendicular to

[001] . c The upper and lower surfaces were polished with 2000-grit sandpaper, then polished with metallographic sandpaper to a thickness of 1.2mm, and then ultrasonically cleaned with deionized water and ethanol respectively, and dried.

[0180] (2) Burning silver-impregnated electrodes

[0181] A 0.02 mm thick layer of silver paste was coated on the upper and lower surfaces of the polished textured piezoelectric ceramic. The ceramic was placed in a resistance furnace and held at 700 °C for 20 min. It was then allowed to cool naturally to room temperature to obtain the textured piezoelectric ceramic with sintered silver electrodes.

[0182] (3) Polarization

[0183] Phase change assisted polarization: The textured piezoelectric ceramic after sintering and infiltrating silver electrodes is placed in fixture 3, and then fixture 3 is placed in box-type resistance furnace 2 and heated to the required polarization temperature (280℃). The polarization electric field is 300V / mm, and the holding polarization time is 50min. After naturally cooling to room temperature, the electric field is removed to obtain high-performance PZT-based textured piezoelectric ceramic.

[0184] The high-performance PZT-based textured piezoelectric ceramic prepared in this embodiment is along

[001] . c The directional texture is 99.2%, the Curie temperature is 364℃, the trigonal-tetragonal phase transition temperature is 236℃, and the electrical properties are as follows: piezoelectric constant after phase transition assisted polarization. d 33 With a piezoelectric coefficient of 962 pC / N, it has a high field piezoelectricity. The coefficient of performance is 1978 pm / V, the coercive field is 10.5 kV / cm, and the strain is 0.65%.

[0185] Comparative Example 2

[0186] Same as Example 2, the only difference being that step (3) of preparing the high-performance PZT-based textured piezoelectric ceramic uses conventional heating polarization. The specific process is as follows: the textured piezoelectric ceramic after the silver-impregnated electrode is placed in silicone oil, and a DC electric field is used to polarize the textured piezoelectric ceramic along

[001] . c Directional polarization was applied at a polarization temperature of 140℃, a polarization voltage of 40kV / cm, and a polarization voltage holding time of 60 minutes to obtain textured piezoelectric ceramics.

[0187] The textured piezoelectric ceramic prepared by conventional heating polarization in this comparative example has a texture degree of 99.2%, a Curie temperature of 364℃, and the following electrical properties: piezoelectric constant. d 33 With a piezoelectric coefficient of 685 pC / N, it has a high field piezoelectricity. The coefficient of performance is 1382 pm / V, the coercive field is 10.5 kV / cm, and the strain is 0.49%.

[0188] Example 3

[0189] A phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics, comprising the following steps:

[0190] 1. Preparation of Eu-doped PMN-PZT matrix powder:

[0191] (1) Preparation of precursor powder

[0192] According to the stoichiometric ratio of MgNb2O6, 13.1798 g of MgO and 86.9203 g of Nb2O5 were weighed as raw materials. All the weighed raw materials were mixed evenly and placed in a nylon jar. Zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled at 150 rpm for 24 hours. The zirconia balls were separated, and the ball-milled mixture was dried at 80℃ for 24 hours. It was then ground in a mortar for 30 minutes and passed through an 80-mesh sieve. The sieved powder was placed in an alumina crucible, covered, and calcined at 1100℃ for 5 hours to synthesize MgNb2O6 precursor powder.

[0193] (2) Ingredients

[0194] Based on 3 mol% Eu2O3 doping of 0.2 Pb(Mg) 1 / 3 Nb 2 / 3 The following raw materials were prepared for the preparation of O3-0.3PbZrO3-0.5PbTiO3: 70.2067g of PbO (99.9% purity), 66.2694g of MgNb2O (99.9% purity), 11.3462g of ZrO2 (99.9% purity), 12.2676g of TiO2 (99.9% purity), and 1.6202g of Eu2O3 (99.9% purity) were weighed out. All raw materials were mixed thoroughly and placed in a nylon container. Zirconia balls were used as grinding media, and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled for 20 hours (200 rpm). The zirconia balls were separated, and the ball-milled mixture was dried at 80℃ for 24 hours. It was then ground in a mortar for 30 minutes and passed through an 80-mesh sieve.

[0195] (3) Pre-firing

[0196] The raw material mixture after passing through an 80-mesh sieve in step (2) is placed in an alumina crucible and compacted with an agate rod (compacted density of 1.5 g / cm³). 3 Cover the contents, place them in a resistance furnace, and pre-fire at 750°C for 4 hours with a heating rate of 2°C / min. Let them cool naturally to room temperature, remove them from the furnace, and grind them in a mortar for 10 minutes to obtain pre-fired powder.

[0197] (4) Secondary ball milling

[0198] The pre-calcined powder obtained in step (3) was loaded into a nylon can, and zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to pre-calcined powder was 1:1.2. The mixture was ball-milled at a speed of 300 rpm for 12 hours. The zirconia balls were separated, and the pre-calcined powder was dried at 90°C for 12 hours. It was then ground in a mortar for 10 minutes and passed through an 80-mesh sieve to obtain Eu-doped PMN-PZT matrix powder.

[0199] 2. Preparation of Eu-doped PMN-PZT textured piezoelectric ceramics:

[0200] (1) Ball milling

[0201] The Eu-doped PMN-PZT matrix powder prepared above was placed in a ball mill jar, using zirconia balls as milling balls, a xylene-ethanol mixed solution (xylene and ethanol mass ratio of 1:1.2) as solvent, and castor oil as dispersant, and milled for 10 hours; then, a binder (polyvinyl butyral) and a plasticizer (a mixture of polyalkylene glycol and butyl benzyl phthalate, mass ratio of 1:1) were added sequentially, and milled for 24 hours to obtain a matrix slurry; in this embodiment, the mass ratio of Eu-doped PMN-PZT matrix powder to xylene-ethanol mixed solution was 1:0.6, the mass ratio of Eu-doped PMN-PZT matrix powder to dispersant was 1:0.03, the mass ratio of Eu-doped PMN-PZT matrix powder to binder was 1:0.06, and the mass ratio of Eu-doped PMN-PZT matrix powder to plasticizer was 1:0.06;

[0202] (2) Preparation of casting slurry

[0203] Select a sheet-like microcrystalline template according to a molar ratio of 0.01:1 to the matrix slurry, wherein the sheet-like microcrystalline template is a lead titanate PT seed crystal; mix the sheet-like microcrystalline template with the matrix slurry in step (1) and ball mill it, and stir it on a magnetic stirrer for 24 hours (speed is 200 r / min) to obtain the casting slurry;

[0204] (3) Vacuuming

[0205] Under stirring conditions of 200 r / min, the above cast slurry was placed in a vacuum degassing device and vacuumed for 3 hours to obtain a slurry with air bubbles removed.

[0206] (4) Casting

[0207] The above-mentioned de-bubbled slurry was cast using a casting machine at a casting speed of 60 cm / min. The thickness between the casting doctor blade and the base film was 50 μm. After casting, the film was dried for 1 hour to obtain a film sheet. The film sheet was then cut with a film cutter to obtain a 5 cm × 5 cm film sheet.

[0208] (5) Overlapping

[0209] The cut membrane was vacuumed and then multi-layered (25 layers) to obtain the laminated membrane. The vacuuming time was 60 seconds, and the laminating machine parameters were: upper pressure table temperature 90℃, lower pressure table temperature 90℃, and pressure 5MPa.

[0210] (6) Warm isostatic pressing

[0211] Under a pressure of 10 MPa and a water temperature of 90℃, the stacked diaphragm was subjected to hot water uniform pressing for 120 minutes to obtain the hot water uniform pressing diaphragm.

[0212] (7) Cutting

[0213] The isostatically pressed membrane was cut with a cutting machine to obtain a 2.5cm×2.5cm blank sample;

[0214] (8) De-glue

[0215] The green blank sample after warm isostatic pressing was placed in a low-temperature furnace. The furnace was heated from room temperature to 650℃ at a heating rate of 0.8℃ / min. Then, the binder was removed at 650℃ for 0.5 hours. After the binder was removed, the temperature was lowered to room temperature at a cooling rate of 0.8℃ / min to obtain the green blank after the binder was removed.

[0216] (9) Cold isostatic pressing

[0217] Under the conditions of 150 MPa pressure and room temperature oil, the raw blank after debinding was subjected to cold isostatic pressing for 10 minutes to obtain the cold isostatic pressing sample.

[0218] (10) Sintering

[0219] In an air atmosphere, the cold isostatically pressed sample was placed in a high-temperature furnace for sintering to create a texture. The gas flow rate was 2 L / min, the sintering temperature was 1000℃, and the holding time was 3 hours, resulting in Eu-doped PMN-PZT textured piezoelectric ceramics. The textured piezoelectric ceramics were trigonal phases, along

[001] . c The directional texture degree is 99.0%;

[0220] 3. Preparation of high-performance PZT-based textured piezoelectric ceramics (which are Eu-doped PMN-PZT textured piezoelectric ceramics with high electrical performance):

[0221] (1) Polishing

[0222] The sintered textured piezoelectric ceramic is then subjected to a process perpendicular to

[001] . c The upper and lower surfaces were polished with 600-grit sandpaper, then polished with metallographic sandpaper to a thickness of 0.8mm, and then ultrasonically cleaned with deionized water and ethanol respectively, and dried.

[0223] (2) Burning silver-impregnated electrodes

[0224] A 0.02 mm thick layer of silver paste was coated on the upper and lower surfaces of the polished textured piezoelectric ceramic. The ceramic was placed in a resistance furnace and held at 500 °C for 60 min. After natural cooling to room temperature, the textured piezoelectric ceramic with sintered silver electrodes was obtained.

[0225] (3) Polarization

[0226] Phase change assisted polarization: The textured piezoelectric ceramic after sintering and infiltrating silver electrodes is placed in fixture 3, and then fixture 3 is placed in box-type resistance furnace 2 and heated to the required polarization temperature (230℃). The polarization electric field is 1000V / mm, the holding polarization time is 10min, and the electric field is removed after natural cooling to room temperature to obtain high-performance PZT-based textured piezoelectric ceramic.

[0227] The high-performance PZT-based textured piezoelectric ceramic prepared in this embodiment is shown in

[001] . c With an directional texture of 99.5% and a Curie temperature of 360℃, the electrical properties are as follows: piezoelectric constant after phase change-assisted polarization. d 33 With a piezoelectric coefficient of 10¹⁴ pC / N, it has a high field piezoelectricity. The value is 1987 pm / V, the coercive field is 10 kV / cm, and the strain is 0.66%.

[0228] The dielectric temperature spectrum of the high-performance PZT-based textured piezoelectric ceramic prepared by phase change-assisted polarization in this embodiment is as follows: Figure 5 As shown, the trigonal-tetragonal phase transition temperature is approximately 200℃. Therefore, the phase transition-assisted polarization temperature for PZT-based textured piezoelectric ceramics is approximately 230℃~300℃.

[0229] Comparative Example 3

[0230] Same as Example 3, except that step (3) of preparing high-performance PZT-based textured piezoelectric ceramics uses conventional heating polarization. The specific process is as follows: the textured piezoelectric ceramic after the silver-impregnated electrode is placed in silicone oil, and a DC electric field is used to polarize the textured piezoelectric ceramic along

[001] . c Directional polarization was applied at a polarization temperature of 140℃, a polarization voltage of 40kV / cm, and a polarization voltage holding time of 60 minutes to obtain textured piezoelectric ceramics.

[0231] The textured piezoelectric ceramic prepared by conventional heating polarization in this comparative example has a texture degree of 99.5%, a Curie temperature of 360℃, and the following electrical properties: piezoelectric constant. d 33 It has a piezoelectric coefficient of 795 pC / N and a high field piezoelectricity. The coefficient of performance is 1408 pm / V, the coercive field is 10 kV / cm, and the strain is 0.53%.

[0232] Example 4

[0233] A phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics, comprising the following steps:

[0234] 1. Preparation of Sm-doped PYN-PZT matrix powder:

[0235] (1) Preparation of precursor powder

[0236] According to the stoichiometric ratio of YbNbO4, 59.7804 g of Yb2O3 and 40.3197 g of Nb2O5 were weighed as raw materials. All the weighed raw materials were mixed evenly and placed in a nylon jar. Zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled at 200 rpm for 24 hours. The zirconia balls were separated, and the ball-milled mixture was dried at 90℃ for 24 hours. It was then ground in a mortar for 30 minutes and passed through an 80-mesh sieve. The sieved powder was placed in an alumina crucible, covered, and calcined at 1050℃ for 8 hours to synthesize YbNbO4 precursor powder.

[0237] (2) Ingredients

[0238] Based on 5 mol% Sm2O3 doping of 0.3Pb(Yb) 1 / 2 Nb 1 / 2 The following raw materials were prepared for the preparation of O3-0.32PbZrO3-0.38PbTiO3: 65.7726g of PbO (99.9% purity), 14.2444g of YbNbO4 (99.9% purity), 11.3383g of ZrO2 (99.9% purity), 8.7346g of TiO2 (99.9% purity), and 2.5091g of Sm2O3 (99.9% purity) were weighed out. All raw materials were mixed thoroughly and placed in a nylon container. Zirconia balls were used as grinding media, and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to raw materials was 1:1.2. The mixture was ball-milled for 20 hours (at 200 rpm). The zirconia balls were separated, and the ball-milled mixture was dried at 90℃ for 20 hours. It was then ground in a mortar for 30 minutes and passed through an 80-mesh sieve.

[0239] (3) Pre-firing

[0240] The raw material mixture after passing through an 80-mesh sieve in step (2) is placed in an alumina crucible and compacted with an agate rod (compacted density of 1.5 g / cm³). 3 Cover the contents, place them in an electric resistance furnace, and pre-fire at 800°C for 3 hours at a heating rate of 6°C / min. Allow them to cool naturally to room temperature, remove them from the furnace, and grind them in a mortar for 10 minutes to obtain pre-fired powder.

[0241] (4) Secondary ball milling

[0242] The pre-calcined powder obtained in step (3) was loaded into a nylon can, and zirconia balls were used as grinding balls and anhydrous ethanol was used as the grinding medium. The mass ratio of anhydrous ethanol to pre-calcined powder was 1:1.2. The mixture was ball-milled at a speed of 200 rpm for 15 hours. The zirconia balls were separated, and the pre-calcined powder was dried at 90°C for 15 hours. It was then ground in a mortar for 10 minutes and passed through an 80-mesh sieve to obtain Sm-doped PYN-PZT matrix powder.

[0243] 2. Preparation of Sm-doped PYN-PZT textured piezoelectric ceramics:

[0244] (1) Ball milling

[0245] The Sm-doped PYN-PZT matrix powder prepared above was placed in a ball mill jar, using zirconia balls as milling balls, a xylene-ethanol mixture (xylene and ethanol in a mass ratio of 1:1) as solvent, and castor oil as dispersant, and milled for 48 hours. Then, a binder (polyvinyl butyral) and a plasticizer (a mixture of polyalkylene glycol and butyl benzyl phthalate in a mass ratio of 1:1) were added sequentially, and milled for 24 hours to obtain a matrix slurry. In this embodiment, the mass ratio of Sm-doped PYN-PZT matrix powder to xylene-ethanol mixture was 1:0.4, the mass ratio of Sm-doped PYN-PZT matrix powder to dispersant was 1:0.04, the mass ratio of Sm-doped PYN-PZT matrix powder to binder was 1:0.04, and the mass ratio of Sm-doped PYN-PZT matrix powder to plasticizer was 1:0.04.

[0246] (2) Preparation of casting slurry

[0247] Select a sheet-like microcrystalline template according to a molar ratio of 0.03:1 to the matrix slurry, wherein the sheet-like microcrystalline template is a lead zirconate titanate (PZT) seed crystal; mix the sheet-like microcrystalline template with the matrix slurry in step (1) and ball mill it, and stir it on a magnetic stirrer for 48 hours (speed is 200 r / min) to obtain the casting slurry;

[0248] (3) Vacuuming

[0249] Under stirring conditions of 300 r / min, the above cast slurry was placed in a vacuum degassing device and vacuumed for 1 hour to obtain a slurry with air bubbles removed.

[0250] (4) Casting

[0251] The above-mentioned de-bubbled slurry was cast using a casting machine at a casting speed of 40 cm / min. The thickness between the casting doctor blade and the base film was 150 μm. After casting, the film was dried for 2 hours to obtain a film sheet. The film sheet was then cut with a film cutter to obtain a 5 cm × 5 cm film sheet.

[0252] (5) Overlapping

[0253] The cut membrane is vacuumed and then multi-layered (20 layers) to obtain the laminated membrane. The vacuuming time is 40 seconds. The laminator parameters are: upper pressure table temperature 80℃, lower pressure table temperature 80℃, and pressure 25MPa.

[0254] (6) Warm isostatic pressing

[0255] Under a pressure of 25 MPa and a water temperature of 80℃, the stacked diaphragm was subjected to hot water uniform pressing for 90 minutes to obtain the hot water uniform pressing diaphragm.

[0256] (7) Cutting

[0257] The isostatically pressed membrane was cut with a cutting machine to obtain a 2.5cm×2.5cm blank sample;

[0258] (8) De-glue

[0259] The green sample after isostatic pressing was placed in a low-temperature furnace. The furnace was heated from room temperature to 550°C at a heating rate of 0.5°C / min. Then, the binder was removed at 550°C for 3 hours. After the binder was removed, the temperature was lowered to room temperature at a cooling rate of 0.5°C / min to obtain the green sample after binder removal.

[0260] (9) Cold isostatic pressing

[0261] Under the conditions of a pressure of 200 MPa and an oil temperature of room temperature, the raw blank after debinding was subjected to cold isostatic pressing for 25 minutes to obtain the cold isostatic pressing sample.

[0262] (10) Sintering

[0263] In an air atmosphere, the cold isostatically pressed sample was placed in a high-temperature furnace for sintering and texturing. The gas flow rate was 1.5 L / min, the sintering temperature was 1100℃, and the holding time was 0.25 hours, resulting in Sm-doped PYN-PZT textured piezoelectric ceramics. The textured piezoelectric ceramics were a mixture of trigonal and tetragonal phases, along

[001] . c The directional texture degree is 99.3%;

[0264] 3. Preparation of high-performance PZT-based textured piezoelectric ceramics (which are Sm-doped PYN-PZT textured piezoelectric ceramics with high electrical performance):

[0265] (1) Polishing

[0266] The sintered textured piezoelectric ceramic is then subjected to a process perpendicular to

[001] . cThe upper and lower surfaces were polished with 1000-grit sandpaper, then polished with metallographic sandpaper to a thickness of 1.0 mm, and then ultrasonically cleaned with deionized water and ethanol respectively, and dried.

[0267] (2) Burning silver-impregnated electrodes

[0268] A 0.02 mm thick layer of silver paste was coated on the upper and lower surfaces of the polished textured piezoelectric ceramic. The ceramic was placed in a resistance furnace and held at 850 °C for 5 min. It was then allowed to cool naturally to room temperature to obtain the textured piezoelectric ceramic with sintered silver electrodes.

[0269] (3) Polarization

[0270] Phase change assisted polarization: The textured piezoelectric ceramic after sintering and infiltrating silver electrodes is placed in fixture 3, and then fixture 3 is placed in box-type resistance furnace 2 and heated to the required polarization temperature (300℃). The polarization electric field is 800V / mm, and the holding polarization time is 30min. After naturally cooling to room temperature, the electric field is removed to obtain high-performance PZT-based textured piezoelectric ceramic.

[0271] The high-performance PZT-based textured piezoelectric ceramic prepared in this embodiment is along

[001] . c The directional texture is 99.3%, the Curie temperature is 359℃, the trigonal-tetragonal phase transition temperature is 267℃, and the electrical properties are as follows: piezoelectric constant after phase transition assisted polarization. d 33 With a piezoelectric coefficient of 978 pC / N, it has a high field piezoelectricity. The coefficient of performance is 1965 pm / V, the coercive field is 10.8 kV / cm, and the strain is 0.67%.

[0272] The XRD patterns of the high-performance PZT-based textured piezoelectric ceramics prepared by phase change-assisted polarization in Examples 3 and 4 are shown below. Figure 6 As shown, the intensity of the (001) peak and the (002) peak is much higher than that of other diffraction peaks, indicating that the high-performance PZT-based textured piezoelectric ceramic prepared by phase change-assisted polarization using the present invention has a high (001) orientation.

[0273] Example 5

[0274] A phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics is the same as in Example 1, except that the only difference is the feed preparation process: 0.3Pb(In) doped with 4mol% Eu2O3. 1 / 2 Nb 1 / 2The following materials were prepared for mixing: 66.6857g of PbO (99.9% purity), 12.1774g of InNbO4 (99.9% purity), 12.8738g of ZrO2 (99.9% purity), 8.3516g of TiO2 (99.9% purity), and 2.0737g of Eu2O3 (99.9% purity). The polarization temperature was 250℃, the polarization electric field was 600V / mm, and the polarization time was 20min.

[0275] The high-performance PZT-based textured piezoelectric ceramic prepared in this embodiment is along

[001] . c The directional texture is 99%, the Curie temperature is 352℃, the trigonal-tetragonal phase transition temperature is 215℃, and the electrical properties are as follows: piezoelectric constant after phase transition assisted polarization. d 33 With a piezoelectric coefficient of 1146 pC / N, it has a high field piezoelectricity. The coefficient of performance is 2032 pm / V, the coercive field is 10.6 kV / cm, and the strain is 0.67%.

[0276] Example 6

[0277] A phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics is the same as in Example 1, except that the only difference is the feed preparation process: 0.1% Pb (In) doped with 2 mol% MnO2 is used. 1 / 2 Nb 1 / 2 The following materials were prepared: 69.4568g of PbO (99.9% purity), 4.2278g of InNbO (99.9% purity), 11.4932g of ZrO2 (99.9% purity), 14.9119g of TiO2 (99.9% purity), and 0.5145g of MnO2 (99% purity). The polarization temperature was 270℃, the polarization electric field was 700V / mm, and the polarization time was 40min.

[0278] The high-performance PZT-based textured piezoelectric ceramic prepared in this embodiment is along

[001] . c The directional texture is 99.4%, the Curie temperature is 362℃, the trigonal-tetragonal phase transition temperature is 223℃, and the electrical properties are as follows: piezoelectric constant after phase transition assisted polarization. d 33 With a piezoelectric coefficient of 975 pC / N, it has a high field piezoelectricity. The coefficient of performance is 1936 pm / V, the coercive field is 11.0 kV / cm, and the strain is 0.65%.

[0279] Example 7

[0280] A phase change-assisted polarization preparation method for PZT-based textured piezoelectric ceramics is the same as in Example 3, except that the only difference is the feed preparation process: 0.1% Pb (Mg) doped with 0.75 mol% La2O3 is used. 1 / 3 Nb 2 / 3 The following materials were prepared for mixing: 67.9563g of PbO (99.9% purity), 63.0342g of MgNb2O (99.9% purity), 21.9651g of ZrO2 (99.9% purity), 7.1247g of TiO2 (99.9% purity), and 0.3609g of La2O3 (99.9% purity). The polarization temperature was 230℃, the polarization electric field was 900V / mm, and the polarization time was 10min.

[0281] The high-performance PZT-based textured piezoelectric ceramic prepared in this embodiment is along

[001] . c The directional texture is 99.2%, the Curie temperature is 365℃, the trigonal-tetragonal phase transition temperature is 205℃, and the electrical properties are as follows: piezoelectric constant after phase transition assisted polarization. d 33 With a piezoelectric coefficient of 1054 pC / N, it has a high field piezoelectricity. The coefficient of performance is 1986 pm / V, the coercive field is 10.5 kV / cm, and the strain is 0.66%.

[0282] This invention discloses a method for preparing high-performance PZT-based textured piezoelectric ceramics via phase change-assisted polarization, belonging to the field of piezoelectric materials technology. This invention, through phase change-assisted polarization, prepares high-performance PZT-based textured piezoelectric ceramics, solving the problem of low piezoelectric / electromechanical / dielectric properties caused by insufficient polarization in traditional heating polarization, significantly improving electrical properties; it also solves the problem of the difficulty in simultaneously achieving high piezoelectric performance and high Curie temperature in piezoelectric materials. The textured piezoelectric ceramics prepared using this method are formed along

[001] . c Preferred grain orientation, texture degree exceeding 99%, Curie temperature up to 350℃, and piezoelectric constant. d 33 Higher than 900 pC / N, high field piezoelectric coefficient With a value exceeding 1900 pm / V, a coercive field exceeding 10 kV / cm, and a strain as high as 0.65%, it is expected to have wide applications in fields such as ultrasonic transducers and hydrophones.

[0283] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A method for preparing PZT-based textured piezoelectric ceramics using phase change-assisted polarization, characterized in that, Includes the following steps: Preparation of PMeN-PZT matrix powder; the process for preparing PMeN-PZT matrix powder is as follows: According to A-doped (1-xy)Pb(Me) 1 / 2 Nb 1 / 2 The stoichiometric ratio of O3-yPbZrO3-xPbTiO3 was used to prepare the powder. After uniform mixing, the powder was ball-milled, dried, and pre-calcined to obtain a pre-calcined powder. The pre-calcined powder was then ball-milled and dried a second time to obtain PMeN-PZT matrix powder, wherein A is one of Sm, Mn, La, and Eu, and the doping amount of A is greater than 0 and not greater than 5 mol%; x ranges from 0.3 to 0.6; y ranges from 0.3 to 0.6, and x + y < 1; Me is one of Yb, Mg, and In. Textured piezoelectric ceramics were prepared by tape casting using PMeN-PZT matrix powder and a sheet-like microcrystalline template. The sheet-like microcrystalline template was one of barium titanate seed crystals, barium zirconate titanate seed crystals, lead titanate seed crystals, and lead zirconate titanate seed crystals. The textured piezoelectric ceramic was sequentially polished, sintered with silver-infiltrated electrodes, and subjected to phase-change assisted polarization to obtain the PZT-based textured piezoelectric ceramic. The phase transition assisted polarization step is as follows: the textured piezoelectric ceramic after being sintered with silver electrodes is heated to the polarization temperature, which is between the trigonal-tetragonal phase transition temperature and the Curie temperature of the textured piezoelectric ceramic. The ceramic is then held at this temperature under a polarization electric field of 300V / mm to 1000V / mm, and then allowed to cool naturally to room temperature before the electric field is removed.

2. The method for preparing PZT-based textured piezoelectric ceramics by phase change-assisted polarization according to claim 1, characterized in that, The process of preparing the textured piezoelectric ceramic using PMeN-PZT matrix powder and a lamellar microcrystalline template via a casting method is as follows: The PMeN-PZT matrix powder, solvent, dispersant, binder and plasticizer are mixed and ball-milled to obtain a matrix slurry; The matrix slurry is mixed with the sheet-like microcrystalline template to obtain a casting slurry; the casting slurry is then subjected to vacuuming, casting, drying, cutting, stacking, warm isostatic pressing, secondary cutting, glue removal, cold isostatic pressing, and sintering in sequence to obtain a textured piezoelectric ceramic.

3. The method for preparing PZT-based textured piezoelectric ceramics by phase change-assisted polarization according to claim 2, characterized in that, The solvent is a xylene-ethanol mixture or a xylene-methanol mixture; the dispersant is castor oil or fish oil; the binder is polyvinyl butyral; the plasticizer is a mixture of polyalkylene glycol and butyl benzyl phthalate in equal mass; the mass ratio of xylene to ethanol in the xylene-ethanol mixture is 1:(0.8~1.2); the mass ratio of xylene to methanol in the xylene-methanol mixture is 1:(0.8~1.2).

4. The method for preparing PZT-based textured piezoelectric ceramics by phase change-assisted polarization according to claim 2, characterized in that, The mass ratio of the PMeN-PZT matrix powder, solvent, dispersant, binder and plasticizer is 1: (0.2~0.6): (0.01~0.05): (0.02~0.06): (0.02~0.06).

5. The method for preparing PZT-based textured piezoelectric ceramics by phase change-assisted polarization according to claim 2, characterized in that, The molar ratio of the sheet-like microcrystalline template to the matrix slurry is w:1, where 0 < w ≤ 0.

05.

6. The method for preparing PZT-based textured piezoelectric ceramics by phase change-assisted polarization according to claim 2, characterized in that, The steps of the silver-infiltrated electrode are as follows: uniformly coating silver paste onto the two polished surfaces of the textured piezoelectric ceramic, and holding it at a temperature of 500℃~850℃ for 5min~60min. The heat preservation polarization time is 10 min to 60 min.

7. A PZT-based textured piezoelectric ceramic, characterized in that, The PZT-based textured piezoelectric ceramic was prepared by a phase transition-assisted polarization method according to any one of claims 1 to 6, wherein the PZT-based textured piezoelectric ceramic has an A-doped (1-xy)Pb(Me) composition. 1 / 2 Nb 1 / 2 O3-yPbZrO3-xPbTiO3, where A is one of Sm, Mn, La and Eu, and the doping amount of A is greater than 0 and not greater than 5 mol%; x ranges from 0.3 to 0.6; y ranges from 0.3 to 0.6, and x+y<1; Me is one of Yb, Mg and In.

8. The application of a PZT-based textured piezoelectric ceramic in the fabrication of ultrasonic transducers and hydrophones, characterized in that, The PZT-based textured piezoelectric ceramic described in claim 7 is used.

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