A method for improving piezoelectric performance based on alternating polarization regulation of domain morphology

Abstract

The application belongs to the technical field of piezoelectric ceramics, and discloses a method for improving piezoelectric performance based on alternating polarization regulation of domain morphology, and the specific steps are as follows: step one: ceramic material preparation selects a piezoelectric ceramic material with a chemical formula of 0.665Pb(Mg 1 / 3 Nb 2 / 3 )O3-0.3335PbTiO3-xSm (0.5≤x≤2), wherein the value range of x is 0.5 to 2; the required Nb2O5, MgO, TiO2, Sm2O3 and Pb3O4 raw material powders are accurately weighed according to the stoichiometric proportion. The innovative alternating polarization regulation technology is used to accurately arrange the domain structure, the problems of uneven domain distribution and residual stress caused by traditional direct current polarization are broken through, the control precision of piezoelectric constant and dielectric loss of the piezoelectric ceramic is significantly improved, the synergistic improvement of the material electromechanical performance and consistency is realized relying on the whole process fine process, high-performance piezoelectric materials are provided for high-end devices such as precision sensors and transducers, and the electronic component industry is upgraded to high precision and high reliability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of piezoelectric ceramics, and particularly relates to a method for improving piezoelectric performance based on AC polarization regulation of domain morphology. BACKGROUND

[0002] Piezoelectric ceramics are a kind of functional ceramic materials capable of converting mechanical energy and electrical energy, and belong to the category of inorganic non-metallic materials. The core characteristics thereof originate from the piezoelectric effect. When mechanical pressure is applied to the piezoelectric ceramics, the internal charge distribution of the piezoelectric ceramics changes, thereby generating a potential difference (positive piezoelectric effect) on the surface. Conversely, if an external electric field is applied thereto, the material will deform (inverse piezoelectric effect). This unique bidirectional energy conversion capability enables the piezoelectric ceramics to be widely applied in the fields of sensors, transducers, drivers, ultrasonic devices and precision positioning systems.

[0003] Due to excellent piezoelectricity, ferroelectricity and thermal stability, (1-x)Pb(Mg 1 / 3 Nb 2 / 3 )O3-xPbTiO3-based piezoelectric materials (referred to as PMN-xPT) are widely applied in the fields of ultrasonic transducers, sensors, actuators, energy harvesting devices and the like. Piezoelectric ceramics are a kind of ferroelectric material, and have a region of spontaneous polarization inside, which is referred to as a domain. In a natural state, the polarization directions of these domains are randomly arranged, and the overall piezoelectricity is not exhibited. Polarization treatment is to make the domain directions tend to be consistent by applying an external electric field, so as to obtain macroscopic piezoelectric performance. The polarization methods mainly include direct current polarization and alternating current polarization. There are significant differences between the direct current polarization and the alternating current polarization in the influence on the domain, mainly in the aspects of domain arrangement mode, residual polarization strength, internal stress and material performance stability and the like. The direct current polarization refers to the application of a unidirectional constant electric field to promote the highly consistent arrangement of the domains along the electric field direction. Most of the domains are turned to the direction of the electric field, and a strong uniaxial residual polarization is formed. However, there may be a region that is not completely turned due to lattice defects or stress. The alternating current polarization refers to the adjustment of the domains in multiple directions by an alternating or gradually changing electric field. The domain arrangement is more uniform, and a multi-domain structure may be formed, which reduces the direction singularity and improves the uniformity of the overall structure. The direct current polarization usually produces a high residual polarization strength due to the highly directional arrangement of the domains, and the piezoelectric performance (such as the d33 coefficient) is more optimal, which is suitable for high-sensitivity static applications. The residual polarization strength of the alternating current polarization may be lower, but the domain wall movement is optimized, which may perform better in dynamic response, such as reducing dielectric loss or improving wideband adaptability. The direct current polarization pursues high residual polarization and strong piezoelectric effect, but needs to balance the stress and aging problems. The alternating current polarization adjusts the domains in multiple directions to improve the uniformity and stability of the material, which is suitable for dynamic application scenarios. The selection of the polarization method needs to balance the performance parameters according to the specific application requirements.

[0004] In order to explore the influence of polarization mode on the domain structure and its effect on piezoelectric properties, researchers have done a lot of work. Through direct current polarization, the evolution of the domain structure of hot-pressed KNN ceramics before and after polarization and its effect on piezoelectric properties are studied, but the influence of alternating current polarization is not mentioned; 0.74Pb(Mg 1 / 3 Nb 2 / 3 )O3-0.26PbTiO3(PMN-0.26PT) single crystal is subjected to alternating current polarization (ACP), and the influence of low-frequency (0.1Hz) ACP on electrical properties is discussed. The piezoelectric coefficient and dielectric constant of the ACP treated sample are increased by 42.4% and 14.3% respectively compared with the conventional direct current polarization (DCP), but the influence of ACP on the electrical properties of the ceramic has not been mentioned, so it needs to be improved. SUMMARY

[0005] The purpose of the present application is to provide a method for improving piezoelectric properties based on alternating current polarization to regulate domain morphology, in order to solve the problems raised in the background art.

[0006] In order to achieve the above purpose, the present application provides the following technical scheme: a method for improving piezoelectric properties based on alternating current polarization to regulate domain morphology, the specific steps are as follows:

[0007] Step one: ceramic material preparation

[0008] Selecting a piezoelectric ceramic material with a chemical formula of 0.665Pb(Mg 1 / 3 Nb 2 / 3 )O3–0.3335PbTiO3-xSm (0.5≤x≤2), wherein the value of x ranges from 0.5 to 2; accurately weighing the required Nb2O5, MgO, TiO2, Sm2O3, Pb3O4 raw material powders according to the stoichiometric ratio;

[0009] Step two: wet ball milling

[0010] Put the weighed raw material powder into the ball mill tank, and use wet ball milling process for thorough mixing treatment, the ball milling time lasts for 12 hours to ensure uniform dispersion of the raw materials;

[0011] Step three: pre-sintering treatment

[0012] After ball milling, the mixed raw materials are placed in a drying oven to remove moisture, and then the dried powder is placed in a high temperature furnace to form a pre-sintered ceramic powder;

[0013] Step four: granulation and shaping

[0014] The pre-sintered ceramic powder obtained in step three is again subjected to wet ball milling, and after the ball milling is completed, drying is performed, followed by adding a binder to perform granulation, and after the granulation, a round piece with a thickness of 1.0 millimeter and a diameter of 10 millimeters is pressed;

[0015] Step four: high-temperature sintering

[0016] The formed round piece is placed in a crucible and sintered in a high-temperature sintering furnace, and after the sintering is completed, a ceramic body is obtained;

[0017] Step five: alternating current polarization experiment

[0018] The ceramic body described in step four is placed in a polarization device to perform an experiment, and the alternating current polarization (ACP) treated sample exhibits excellent performance: the piezoelectric coefficient d33 reaches 800 pC / N, and the room temperature dielectric constant is as high as 6221, which is respectively increased by 11.4% and 15.3% compared with traditional direct current polarization (DCP) samples.

[0019] Preferably, in step three, the temperature of the high-temperature furnace is controlled at 800-850°C, and the pre-sintering lasts for 4-6 hours.

[0020] Preferably, in step four, the binder is PVA or paraffin, and the mass fraction of the binder is 5%-10%, and PVA with a mass fraction of 7% is preferably used.

[0021] Preferably, in step five, the sintering temperature is 1230°C-1270°C, and the sintering time is 2-4 hours.

[0022] Preferably, in step five, the polarization device is set to have an alternating current polarization parameter of an electric field intensity of 30 kV / cm, a frequency of 0.1 Hz, and a polarization time of 10 minutes.

[0023] Preferably, the domain characteristics of the unpoled ceramic are a large irregular watermark area and local tiny domains, the domain direction is disordered, there is no obvious stripe or directionality, the domains cancel each other out, and the macroscopic appearance is isotropic, so the piezoelectric performance is close to 0.

[0024] Preferably, under the driving of a direct current electric field, the domains of the ceramic body are arranged in parallel along a single direction, forming clear unidirectional stripes, the directionality is significantly enhanced, and the local order is discontinuous in the long term.

[0025] Preferably, under the driving of an alternating current electric field, the domains of the ceramic body are densely arranged, the stripe spacing is significantly reduced, and the stripes are finer, and the periodic change of the alternating current electric field promotes the rearrangement of the domains in the alternating direction, forming a long-range ordered structure.

[0026] Preferably, in step one, the purity of the raw materials is not less than 99.9%, and the molar ratio of each component is ensured to meet the chemical formula.

[0027] The beneficial effects of the present application are as follows:

[0028] By innovative exchange polarization regulation technology, the domain structure is precisely arranged, the problems of uneven distribution of domains and residual stress caused by traditional direct current polarization are broken through, the control precision of piezoelectric constant and dielectric loss of piezoelectric ceramics is significantly improved, and the consistency of mechanical and electrical properties of the material is improved simultaneously by relying on the whole process fine process, which provides high-performance piezoelectric material support for high-end devices such as precision sensors and transducers, and promotes the upgrading of electronic component industry to high precision and high reliability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a comparison chart of the piezoelectric coefficient and dielectric performance of the PMN-PT-xSm ceramic of the present application with temperature change;

[0030] Figure 2 It is a base microstructure chart of the unpoled sample of the PMN-PT-xSm ceramic of the present application;

[0031] Figure 3 It is a comparison chart of local stripe domain and base disordered structure of the direct current polarization sample of the present application;

[0032] Figure 4 It is a structure chart of fine and uniform stripe domain and hole edge domain of the alternating current polarization sample of the present application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0034] As shown in the figure, the embodiment of the present application provides a method for improving piezoelectric performance based on exchange polarization regulation of domain morphology, and the specific steps are as follows: Figures 1 to 4

[0035] Step one: ceramic material preparation

[0036] The piezoelectric ceramic material with the chemical formula of 0.665Pb(Mg 1 / 3 Nb 2 / 3 )O3–0.3335PbTiO3-xSm (0.5≤x≤2) is selected, wherein the value range of x is 0.5 to 2; the required Nb2O5, MgO, TiO2, Sm2O3 and Pb3O4 raw material powders are accurately weighed according to the stoichiometric ratio;

[0037] Step two: wet ball milling ​

[0038] The weighed raw material powder is put into a ball mill tank, and a wet ball milling process is used for thorough mixing treatment, and the ball milling time lasts for 12 hours to ensure uniform dispersion of the raw materials;

[0039] Step three: pre-sintering treatment

[0040] After ball milling, the mixed raw materials are placed in a drying box for drying to remove moisture, and then the dried powder is placed in a high-temperature furnace to form a pre-sintered ceramic powder;

[0041] Step four: granulation and shaping

[0042] The pre-sintered ceramic powder obtained in step three is subjected to wet ball milling treatment again, and after ball milling treatment, drying is performed, and then a binder is added for granulation, and after granulation, a round piece with a thickness of 1.0 millimeter and a diameter of 10 millimeters is pressed;

[0043] Step four: high-temperature sintering

[0044] The shaped round piece is placed in a crucible and sintered in a high-temperature sintering furnace, and after sintering is completed, a ceramic body is obtained;

[0045] Step five: alternating current polarization experiment

[0046] The ceramic body in step four is placed in a polarization device for experiment, and the alternating current polarization (ACP) treated sample exhibits excellent performance: the piezoelectric coefficient d33 reaches 800 pC / N, and the room temperature dielectric constant is as high as 6221, which is 11.4% and 15.3% higher than that of the traditional direct current polarization (DCP) sample, respectively.

[0047] with a chemical formula of 0.665Pb(Mg 1 / 3 Nb 2 / 3 )O3–0.3335PbTiO3-xSm (0.5≤x≤2), the raw material powder is accurately weighed, uniformly dispersed by 12 hours of wet ball milling, pre-sintered ceramic powder is formed by drying and high-temperature pre-sintering, a binder is added after secondary ball milling and drying, and a round piece with a thickness of 1.0 millimeter and a diameter of 10 millimeters is pressed, after high-temperature sintering to obtain a dense ceramic body, the sample is treated by alternating current polarization (ACP) technology, and finally the piezoelectric coefficient d33 reaches 800 pC / N and the room temperature dielectric constant is 6221, which is 11.4% and 15.3% higher than that of the traditional direct current polarization (DCP) sample, respectively, significantly optimizing the domain orientation arrangement and electromechanical conversion efficiency.

[0048] In step three, the temperature of the high-temperature furnace is controlled at 800-850°C during pre-sintering, and the pre-sintering lasts for 4-6 hours.

[0049] By controlling the pre-sintering temperature at 800-850℃ for 4-6 hours, it ensures that the raw materials fully react to form a uniform pre-sintered ceramic powder during the pre-sintering process, avoiding the volatilization of components caused by excessive temperature, and preventing incomplete reaction caused by insufficient temperature.

[0050] In step four, the binder is PVA or paraffin wax, and the mass fraction of the binder is 5%-10%, and PVA with a mass fraction of 7% is preferred.

[0051] By controlling the mass fraction of the binder, the good formability and green strength of the powder during granulation are ensured, and the excessive binder is avoided to leave impurities during sintering.

[0052] In step five, the sintering temperature is 1230-1270℃, and the sintering time is 2-4 hours.

[0053] By controlling the sintering temperature at 1230-1270℃ for 2-4 hours, it ensures that the raw materials fully melt and diffuse to form a high-density ceramic body to enhance the mechanical strength and piezoelectric response efficiency.

[0054] In step five, the polarization device is set to an alternating polarization parameter of an electric field intensity of 30kV / cm, a frequency of 0.1Hz, and a polarization time of 10 minutes.

[0055] As shown in the accompanying drawings Figure 1 of the specification, the ACP sample has a higher domain wall density, a narrower domain wall width, and a significantly better uniformity than the DCP sample, and this microstructure feature is considered to be the key mechanism for improving the piezoelectric performance. This research not only provides an innovative strategy for optimizing the performance of PMN-xPT-based ceramics, but also lays a theoretical foundation for the engineering application of piezoelectric materials in functional devices, which has important guiding significance for promoting the development of high-performance piezoelectric devices.

[0056] In the unpoled ceramic, the domain characteristics are large irregular watermark areas and local small domains, the domain direction is disordered, there are no obvious stripes or directionality, the domains cancel each other out, and the macroscopic is isotropic, so the piezoelectric performance is close to 0.

[0057] As can be seen from the accompanying drawings Figure 2 of the specification, the domain characteristics of the unpoled ceramic are shown in the blue dashed box of (a2), and the local small domains are shown in the yellow dashed box of (a2).

[0058] In the unpoled ceramic, the domain characteristics are large irregular watermark areas and local small domains, the domain direction is disordered, there are no obvious stripes or directionality, the domains cancel each other out, and the macroscopic is isotropic, so the piezoelectric performance is close to 0.

[0059] As can be seen from the accompanying drawings Figure 3As can be seen from the description of the drawings, the unidirectional stripe as shown in the yellow dashed box in (b2) indicates that the piezoelectric / ferroelectric performance of the material in the polarization direction is improved, showing anisotropy.

[0060] In the long-range ordered structure, the ceramic body is in a dense domain arrangement under the driving of an alternating electric field, and the stripe spacing is significantly reduced, and the stripe is more fine, and the periodic change of the alternating electric field promotes the rearrangement of the domain in the alternating direction, forming a long-range ordered structure.

[0061] As can be seen from the description of the drawings Figure 4 As can be seen from the description of the drawings, the long-range ordered structure as shown in the yellow dashed box in (c2) indicates that the dielectric constant and the polarization stability are improved.

[0062] In the long-range ordered structure, the ceramic body is in a dense domain arrangement under the driving of an alternating electric field, and the stripe spacing is significantly reduced, and the stripe is more fine, and the periodic change of the alternating electric field promotes the rearrangement of the domain in the alternating direction, forming a long-range ordered structure.

[0063] By using high-purity raw materials, the interference of impurity elements on the lattice structure can be significantly reduced, the formation of non-stoichiometric defects can be avoided, and the single-phase nature of the PMN-PT-xSm ceramic solid solution can be ensured, providing a pollution-free base material for subsequent domain directional regulation.

[0064] It should be noted that, in this document, relational terms such as first and second and the like can be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0065] Although embodiments of the present application have been shown and described, it is to be understood that various modifications, substitutions, replacements and changes can be made to these embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for improving piezoelectric performance based on alternating current polarization regulation of domain morphology, characterized in that, The specific steps are as follows: Step one: ceramic material preparation The chemical general formula is 0.665Pb(Mg 1 / 3 Nb 2 / 3 )O3-0.3335PbTiO3-xSm (0.5≤x≤2), wherein the value range of x is 0.5 to 2; the required Nb2O5, MgO, TiO2, Sm2O3 and Pb3O4 raw material powders are accurately weighed according to the stoichiometric proportion; Step two: wet ball milling Put the weighed raw material powder into the ball mill tank, and use the wet ball milling process for thorough mixing treatment, with a ball milling time of 12 hours to ensure uniform dispersion of the raw materials; Step three: pre-sintering treatment After ball milling, the mixed raw materials are placed in a drying oven to remove moisture, and then the dried powder is placed in a high-temperature furnace to form a pre-sintered ceramic powder; Step four: granulation and shaping The pre-sintered ceramic powder obtained in step three is again subjected to wet ball milling treatment, and after ball milling treatment, drying is performed, followed by the addition of a binder for granulation. After granulation, a round piece with a thickness of 1.0 millimeters and a diameter of 10 millimeters is pressed; Step four: high-temperature sintering The shaped round piece is placed in a crucible and sintered in a high-temperature sintering furnace. After sintering is completed, a ceramic body is obtained; Step five: alternating current polarization experiment The ceramic body described in step four is placed in a polarization device for experiment. The polarization device is set to have an alternating current polarization parameter of an electric field intensity of 30 kV / cm and a frequency of 0.1 Hz, and the polarization time lasts for 10 minutes. The alternating current polarization treated sample exhibits excellent performance: the piezoelectric coefficient d33 reaches 800 pC / N, and the room temperature dielectric constant is as high as 6221, which is 11.4% and 15.3% higher than that of traditional direct current polarization samples, respectively. The domains of the ceramic body are densely arranged under the driving of alternating current electric field, and the stripe spacing is significantly reduced. The alternating periodic change of alternating current electric field promotes the rearrangement of domains in alternating directions, forming a long-range ordered structure.

2. The method of claim 1, wherein the method is based on alternating current (AC) electric field poling to control domain morphology for improved piezoelectric properties. In step three, the pre-sintering temperature of the high-temperature furnace is controlled at 800-850℃, and the pre-sintering time lasts for 4-6 hours.

3. The method of claim 1, wherein the method is based on alternating current (AC) electric field poling to control domain morphology for improved piezoelectric properties. In step four, the binder used is PVA or paraffin, and the mass fraction of the binder is 5%-10%.

4. The method of claim 3, wherein the method is characterized by: The binder preferably uses PVA with a mass fraction of 7%.

5. The method of claim 1, wherein the method is based on alternating electric field to control domain morphology to improve piezoelectric properties. In step five, the sintering temperature is 1230℃-1270℃, and the sintering time is 2-4 hours.

6. The method of claim 1, wherein the method is based on alternating electric field to control domain morphology to improve piezoelectric properties. The domain characteristics of the unpoled ceramic are large irregular watermark areas and local small domains, the domain direction is disordered, there is no obvious stripe or directionality, the domains cancel each other out, and the macroscopic appearance is isotropic, so the piezoelectric performance is close to 0.

7. The method of claim 1, wherein the method is based on alternating current (AC) electric field poling to control domain morphology for improved piezoelectric properties. Under the driving of direct current electric field, the domains of the ceramic body are arranged in parallel along a single direction, forming clear unidirectional stripes, and the directionality is significantly enhanced. The local order is discontinuous in the long range.

8. The method of claim 1, wherein the method is based on alternating current (AC) electric field poling to control domain morphology for improved piezoelectric properties. In step one, the purity of the raw material powder is not less than 99.9%, and the molar ratio of each component is ensured to meet the chemical formula.

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