Trilateral phase relaxor ferroelectric single crystal depolarization inhibition method based on interface modification

Abstract

The invention relates to the technical field of piezoelectric materials, and discloses an interface modification-based trigonal phase relaxor ferroelectric single crystal depolarization inhibition method, which comprises single crystal pretreatment, polarization electric field optimization, interface modification layer construction, gradient annealing treatment, stabilization electric field application and protection layer packaging. Through single crystal pretreatment and polarization electric field optimization, it is guaranteed that the surface of a single crystal is smooth and clean, a main polarization electric field is applied in the protective atmosphere through a stepped boosting method, single crystal oxidative damage is avoided, the polarization effect is improved, and a foundation is laid for depolarization inhibition; through construction of an interface modification layer and gradient annealing treatment, a high-dielectric-constant interface layer is formed on the surface of a single crystal, internal stress is eliminated under a protective atmosphere through multi-stage program temperature control annealing, the interface bonding strength and the crystal structure stability are enhanced, and the depolarization process is inhibited.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric materials technology, specifically to a method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification. Background Technology

[0002] Underwater acoustic transducers are typically driven by piezoelectric materials such as lead zirconate titanate polycrystalline piezoelectric ceramics, relaxor ferroelectric single crystals, or piezoelectric ceramic-polymer composites. As the front end of a sonar system, underwater acoustic transducers are responsible for transmitting and receiving sound waves and are widely used in fields such as ship and submarine sonar, marine resource exploration, environmental protection, and medical equipment.

[0003] Currently, in the polarization process of trigonal relaxor ferroelectric single crystals, the lack of precise control over the surface state of the single crystal and optimization of the polarization electric field parameters leads to insufficient interface stability after polarization. At the same time, conventional annealing treatment is difficult to effectively eliminate internal stress and lacks subsequent stabilization measures, making the single crystal prone to depolarization under long-term use or environmental changes, affecting the stability of its piezoelectric properties.

[0004] Therefore, a method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification is proposed to solve the above problems.

[0005] In this application, standard notation rules in materials science and crystallography are used: Crystal orientation: indicated by square brackets, for example

[001] . This represents a specific orientation.

[0006] Crystal plane: indicated by parentheses, for example (001). This represents a specific plane.

[0007] Crystal family: indicated by angle brackets, for example <001> This represents the set of all directions that are mutually equivalent by crystal symmetry, such as in a cubic crystal system. <001> The family includes directions such as

[001] ,

[010] ,

[100] , [00-1], [0-10], and [-100]. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification. This method solves the problems mentioned in the background art, such as insufficient interface stability of single crystals after polarization and the tendency of single crystals to depolarize under long-term use or environmental changes, which affect the stability of their piezoelectric properties.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification, comprising the following steps: Step 1: Single crystal pretreatment. Select trigonal phase relaxor ferroelectric single crystals and perform surface polishing, cleaning, and drying. Step 2: Polarization electric field optimization. The pretreated single crystal is placed in a temperature-controlled polarization device, and a main polarization electric field with a field strength of 0.5-3.0kV / mm is applied along its spontaneous polarization direction. The polarization temperature is 80-150℃ and the polarization time is 10-60 minutes. Step 3: Construction of interface modification layer. An interface modification layer with a thickness of 10-500 nanometers is prepared on the polarized single crystal surface. Step 4: Gradient annealing treatment. Place the single crystal in a programmable temperature controlled furnace for multi-stage gradient annealing. First, heat the crystal to 200-300℃ at a rate of 1-5℃ / min and hold it for 30-90 minutes. Then, cool the crystal to 100-180℃ at a rate of 0.5-2℃ / min and hold it for 60-180 minutes. Finally, cool the crystal with the furnace. Step 5: Apply a stabilizing electric field. Apply a stabilizing bias electric field with a field strength of 0.1-0.8 kV / mm and a direction consistent with the main polarization electric field at room temperature for 1-24 hours. The interface modification layer is made of 40-60 parts of high dielectric constant ceramic powder, 10-20 parts of glass powder, 20-30 parts of organosilicon resin precursor and 1-5 parts of coupling agent.

[0010] Preferably, in step one, the single crystal pretreatment includes the following steps: The single crystal surface is finely polished with diamond polishing slurry until the surface roughness Ra≤5nm. Then, it is ultrasonically cleaned in acetone, ethanol and deionized water for 10-20 minutes each. After cleaning, it is placed in a clean drying oven and dried at 60-80℃ for 1-2 hours.

[0011] Preferably, in step two, the application of the main polarization electric field employs a stepped voltage boosting method, specifically as follows: First, apply an initial electric field of 0.2-0.5 kV / mm and maintain it for 5-10 minutes, then gradually increase it to the target field strength at a rate of 0.1-0.3 kV / min. The environment inside the polarization device is a silicone oil or inert gas atmosphere to prevent oxidation of the single crystal during high-temperature polarization.

[0012] Preferably, in the construction of the interface modification layer, when physical vapor deposition is used, the process parameters are: sputtering power 100-300W, working pressure 0.5-2.0Pa, substrate temperature 100-200℃, and deposition rate 0.1-0.5nm / s. When using spin coating, the interface modification layer material is first dispersed in an organic solvent to form a slurry with a solid content of 10-30 wt%. The spin coating speed is 2000-5000 rpm and the spin coating time is 30-60 seconds. Then, the solvent is removed by preheating at 80-120℃ for 10-20 minutes.

[0013] Preferably, the high dielectric constant ceramic powder in the interface modification layer material is barium titanate, strontium titanate, or lead-based perovskite ceramic powder; The glass powder is borosilicate glass or phosphate glass, with a softening temperature of 400-600℃. The organosilicon resin precursor is methyltriethoxysilane or tetraethyl orthosilicate; The coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0014] Preferably, in the gradient annealing process of step four, the first stage of the heating process is carried out in a nitrogen protective atmosphere with an oxygen content of less than 50 ppm to prevent the interface modification layer and the single crystal surface from deteriorating at high temperatures.

[0015] Preferably, the stabilizing bias electric field in step five is applied as a DC electric field or a quasi-DC square wave electric field with a frequency of less than 1 Hz, and the duty cycle of the square wave electric field is 50%-80%.

[0016] Preferably, after step five, the method further includes: Step Six: Protective Layer Encapsulation. The single crystal treated with the stabilized electric field is vacuum encapsulated using epoxy resin or parylene to form a protective layer with a thickness of 10-100 micrometers. The encapsulation process is carried out at room temperature to 60°C.

[0017] Preferably, the epoxy resin is a bisphenol A type epoxy resin, and the curing agent is an acid anhydride or amine curing agent, with the mass ratio of epoxy resin to curing agent being 10:1 to 5:1. The parylene was deposited using chemical vapor deposition (CVD) at a deposition chamber pressure of 10-50 Pa and a deposition rate of 0.5-2 μm / h.

[0018] Preferably, the trigonal phase relaxor ferroelectric single crystal is a lead magnesium niobate-lead titanate, lead zinc niobate-lead titanate, or lead indium niobate-lead titanate relaxor ferroelectric single crystal, and the crystallographic direction of its <001> orientation deviates from the direction of the main polarization electric field by less than 5°.

[0019] The physical principle of single-crystal pretreatment in this method is as follows: Polishing controls surface roughness to the nanometer level, reducing microcracks and defects and avoiding localized breakdown caused by electric field concentration. The chemical principle is that ultrasonic cleaning with acetone and ethanol can remove organic contaminants and ion residues, deionized water cleaning eliminates electrostatic adsorption, and the drying process prevents hydrolysis and oxidation, thereby ensuring the chemical inertness and electrical uniformity of the single crystal surface and providing an ideal interface for subsequent polarization.

[0020] The physical principle of polarization electric field optimization is that the step-by-step voltage boosting method gradually increases the electric field strength, causing the electric domains to gradually turn, avoiding domain wall pinning or breakdown caused by abrupt electric field changes. The chemical principle is that silicone oil or an inert gas atmosphere creates an oxygen-deficient environment, which inhibits the oxidation reaction of the single crystal surface at high temperatures, maintains the chemical stability of the crystal structure, and thus improves polarization efficiency and durability.

[0021] The physical principle of the interface modification layer is that the high dielectric constant ceramic powder forms a continuous dielectric layer, reducing the accumulation of interfacial charge and electric field distortion, and enhancing the interfacial bonding strength. The chemical principle is that the glass powder softens and flows during annealing, and fills the pores through sintering densification. The organosilicon resin precursor forms a -Si-O- network through condensation reaction. The coupling agent bridges the inorganic-organic interface through hydrolysis and condensation, improving the interlayer adhesion and chemical stability.

[0022] The chemical principle of the interface modification layer: The B2O3 and SiO2 network in borosilicate glass forms a low-melting-point liquid phase during annealing, promoting interfacial diffusion bonding; the POP chains of phosphate glass enhance hydrolysis resistance; the organosilicon resin precursor hydrolyzes to generate silanol, which condenses to form a three-dimensional cross-linked structure, providing flexibility and thermal stability; the amino or epoxy groups of the coupling agent form covalent bonds with the hydroxyl groups on the single crystal surface, achieving molecular-level interface modification and inhibiting ion migration during depolarization.

[0023] The physical principle of using a DC or quasi-DC electric field to stabilize the polarization state is that the DC electric field provides a continuous polarization force, causing the residual electric domains to align in an oriented manner and reducing the domain wall energy. The chemical principle is that the low-frequency alternating characteristics of the quasi-DC square wave electric field promote the pinning of domain walls to the interface modification layer through periodic small perturbations, and suppress depolarization caused by thermal activation. The duty cycle optimization ensures the proportion of electric field action time, balancing polarization efficiency and energy consumption.

[0024] Compared with the prior art, the present invention provides a method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification, which has the following beneficial effects: 1. In this invention, single crystal pretreatment and polarization electric field optimization are used to ensure that the single crystal surface is smooth and clean. A step-by-step voltage boosting method is used to apply the main polarization electric field in a protective atmosphere to avoid single crystal oxidation damage and improve polarization effect, thus laying the foundation for depolarization suppression.

[0025] 2. In this invention, a high dielectric constant interface layer is formed on the surface of a single crystal by constructing an interface modification layer and performing gradient annealing. Internal stress is eliminated under a protective atmosphere by multi-stage programmed temperature-controlled annealing, thereby enhancing the interface bonding strength and crystal structure stability and suppressing the depolarization process.

[0026] 3. In this invention, by applying a stable bias electric field and encapsulating a protective layer, the polarization state is further stabilized by a DC or quasi-DC electric field, and a protective layer is formed by vacuum encapsulation to prevent performance degradation caused by environmental factors and achieve long-term depolarization suppression. Attached Figure Description

[0027] Figure 1 A comparison diagram showing the effects of existing trigonal phase relaxor ferroelectric single crystal depolarization suppression methods and the method implemented in Embodiment 2 of the present invention; Figure 2 This is a flowchart of a method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification according to the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1: Please refer to Figure 2 A method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification, comprising the following steps: Step 1: Single crystal pretreatment. Select trigonal phase relaxor ferroelectric single crystals and perform surface polishing, cleaning, and drying. Step 2: Polarization electric field optimization. The pretreated single crystal is placed in a temperature-controlled polarization device, and a main polarization electric field with a field strength of 0.5kV / mm is applied along its spontaneous polarization direction. The polarization temperature is 80℃ and the polarization time is 10 minutes. Step 3: Construction of the interface modification layer. An interface modification layer with a thickness of 10 nanometers is prepared on the polarized single crystal surface. Step 4: Gradient annealing treatment. The single crystal is placed in a programmable temperature controlled furnace for multi-stage gradient annealing. First, the temperature is increased to 200℃ at 1℃ / min and held for 30 minutes. Then, the temperature is decreased to 100℃ at 0.5℃ / min and held for 60 minutes. Finally, the crystal is cooled in the furnace. Step 5: Apply a stabilizing electric field. Apply a stabilizing bias electric field with a field strength of 0.1 kV / mm and a direction consistent with the main polarization electric field at room temperature for 1 hour. The interface modification layer is made of 40 parts of barium titanate powder as a high dielectric constant ceramic powder, 10 parts of borosilicate glass powder as a glass powder, 20 parts of methyltriethoxysilane as an organosilicon resin precursor, and 1 part of γ-aminopropyltriethoxysilane as a coupling agent.

[0030] In step one, the single crystal pretreatment includes the following steps: The single crystal surface was finely polished with diamond polishing slurry until the surface roughness Ra≤5nm. Then, it was ultrasonically cleaned in acetone, ethanol and deionized water for 10 minutes each. After cleaning, it was placed in a clean drying oven and dried at 60℃ for 1 hour.

[0031] In step two, the main polarization electric field is applied using a stepped voltage boosting method, specifically as follows: First, apply an initial electric field of 0.2 kV / mm and maintain it for 5 minutes, then gradually increase it to the target field strength at a rate of 0.1 kV / min. The environment inside the polarization device is a silicone oil or inert gas atmosphere to prevent oxidation of the single crystal during high-temperature polarization.

[0032] In the construction of the interface modification layer, when physical vapor deposition is used, the process parameters are: sputtering power 100W, working pressure 0.5Pa, substrate temperature 100℃, and deposition rate 0.1nm / s. When using spin coating, the interface modification layer material is first dispersed in an organic solvent to form a slurry with a solid content of 10wt%. The spin coating speed is 2000rpm and the spin coating time is 30 seconds. Then, the solvent is removed by preheating at 80℃ for 10 minutes.

[0033] In the raw materials of the interface modification layer, the glass powder is borosilicate glass or phosphate glass with a softening point temperature of 400℃. The precursor of the organosilicon resin is methyltriethoxysilane or tetraethyl orthosilicate; The coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0034] The gradient annealing process in step four involves the first stage of heating under a nitrogen protective atmosphere with an oxygen content of less than 50 ppm to prevent the interface modification layer and the single crystal surface from deteriorating at high temperatures.

[0035] The stabilizing bias electric field in step five is applied as a DC electric field or a quasi-DC square wave electric field with a frequency of less than 1 Hz and a duty cycle of 50%.

[0036] Following step five, the following is also included: Step 6: Protective layer encapsulation. The single crystal treated with the stabilized electric field is vacuum encapsulated using epoxy resin or parylene to form a protective layer with a thickness of 10 micrometers. The encapsulation process is carried out at room temperature to 60°C.

[0037] The epoxy resin is a bisphenol A type epoxy resin, and its curing agent is an acid anhydride or amine curing agent. The mass ratio of epoxy resin to curing agent is 10:1. Parylene was deposited using chemical vapor deposition at a deposition chamber pressure of 10 Pa and a deposition rate of 0.5 μm / h.

[0038] Trigonal relaxor ferroelectric single crystals are lead magnesium niobate-lead titanate, lead zinc niobate-lead titanate, or lead indium niobate-lead titanate relaxor ferroelectric single crystals, and the crystallographic direction of their <001> orientation deviates from the direction of the main polarization electric field by less than 5°.

[0039] Example 2: Please refer to Figure 1 and Figure 2 A method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification, comprising the following steps: Step 1: Single crystal pretreatment. Select trigonal phase relaxor ferroelectric single crystals and perform surface polishing, cleaning, and drying. Step 2: Polarization field optimization. The pretreated single crystal is placed in a temperature-controlled polarization device, and a main polarization electric field with a field strength of 1.7 kV / mm is applied along its spontaneous polarization direction. The polarization temperature is 115℃ and the polarization time is 35 minutes. Step 3: Construction of the interface modification layer. An interface modification layer with a thickness of 445 nanometers is prepared on the polarized single crystal surface. Step 4: Gradient annealing treatment. The single crystal is placed in a programmable temperature controlled furnace for multi-stage gradient annealing. First, the temperature is increased to 250℃ at 3℃ / min and held for 60 minutes. Then, the temperature is decreased to 140℃ at 1.2℃ / min and held for 120 minutes. Finally, the crystal is cooled in the furnace. Step 5: Applying a stabilizing electric field. A stabilizing bias electric field with a strength of 0.4 kV / mm and a direction consistent with the main polarization electric field is applied at room temperature for 12 hours. The interface modification layer is made of 50 parts of barium titanate powder as a high dielectric constant ceramic powder, 15 parts of phosphate glass powder as a glass powder, 25 parts of tetraethyl orthosilicate as an organosilicon resin precursor, and 3 parts of γ-glycidyl etheroxypropyltrimethoxysilane as a coupling agent.

[0040] In step one, the single crystal pretreatment includes the following steps: The single crystal surface was finely polished with diamond polishing slurry until the surface roughness Ra≤5nm. Then, it was ultrasonically cleaned in acetone, ethanol and deionized water for 15 minutes each. After cleaning, it was placed in a clean drying oven and dried at 70℃ for 1.5 hours.

[0041] In step two, the main polarization electric field is applied using a stepped voltage boosting method, specifically as follows: An initial electric field of 1.1 kV / mm is applied and maintained for 7 minutes, and then gradually increased to the target field strength at a rate of 0.2 kV / min. The environment inside the polarization device is a silicone oil or inert gas atmosphere to prevent oxidation of the single crystal during high-temperature polarization.

[0042] In the construction of the interface modification layer, when physical vapor deposition is used, the process parameters are: sputtering power 200W, working pressure 1.2Pa, substrate temperature 150℃, and deposition rate 0.3nm / s. When using spin coating, the interface modification layer material is first dispersed in an organic solvent to form a slurry with a solid content of 20wt%. The spin coating speed is 3500rpm and the spin coating time is 45 seconds. Then, the solvent is removed by preheating at 100℃ for 15 minutes.

[0043] In the raw materials of the interface modification layer, the glass powder is borosilicate glass or phosphate glass with a softening point temperature of 500℃. The precursor of the organosilicon resin is methyltriethoxysilane or tetraethyl orthosilicate; The coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0044] The gradient annealing process in step four involves the first stage of heating under a nitrogen protective atmosphere with an oxygen content of less than 50 ppm to prevent the interface modification layer and the single crystal surface from deteriorating at high temperatures.

[0045] The stabilizing bias electric field in step five is applied as a DC electric field or a quasi-DC square wave electric field with a frequency of less than 1 Hz and a duty cycle of 65%.

[0046] Following step five, the following is also included: Step 6: Protective layer encapsulation. The single crystal treated with the stabilized electric field is vacuum encapsulated using epoxy resin or parylene to form a protective layer with a thickness of 55 micrometers. The encapsulation process is carried out at room temperature to 60°C.

[0047] The epoxy resin is a bisphenol A type epoxy resin, and its curing agent is an acid anhydride or amine curing agent. The mass ratio of epoxy resin to curing agent is 5:1. Parylene was deposited using chemical vapor deposition at a deposition chamber pressure of 30 Pa and a deposition rate of 1.2 μm / h.

[0048] Trigonal relaxor ferroelectric single crystals are lead magnesium niobate-lead titanate, lead zinc niobate-lead titanate, or lead indium niobate-lead titanate relaxor ferroelectric single crystals, and the crystallographic direction of their <001> orientation deviates from the direction of the main polarization electric field by less than 5°.

[0049] Example 3: Please refer to Figure 2 A method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification, comprising the following steps: Step 1: Single crystal pretreatment. Select trigonal phase relaxor ferroelectric single crystals and perform surface polishing, cleaning, and drying. Step 2: Polarization electric field optimization. The pretreated single crystal is placed in a temperature-controlled polarization device, and a main polarization electric field with a field strength of 3.0 kV / mm is applied along its spontaneous polarization direction. The polarization temperature is 150℃ and the polarization time is 60 minutes. Step 3: Construction of the interface modification layer. An interface modification layer with a thickness of 500 nanometers is prepared on the polarized single crystal surface. Step 4: Gradient annealing treatment. The single crystal is placed in a programmable temperature controlled furnace for multi-stage gradient annealing. First, the temperature is increased to 300℃ at 5℃ / min and held for 90 minutes. Then, the temperature is decreased to 180℃ at 2℃ / min and held for 180 minutes. Finally, the crystal is cooled with the furnace. Step 5: Apply a stabilizing electric field. Apply a stabilizing bias electric field with a field strength of 0.8 kV / mm and a direction consistent with the main polarization electric field at room temperature for 24 hours. The interface modification layer is made of 60 parts of lead zirconate titanate powder as a high dielectric constant ceramic powder, 20 parts of borosilicate glass powder as a glass powder, 30 parts of methyltriethoxysilane as an organosilicon resin precursor, and 5 parts of γ-aminopropyltriethoxysilane as a coupling agent.

[0050] In step one, the single crystal pretreatment includes the following steps: The single crystal surface was finely polished with diamond polishing slurry until the surface roughness Ra≤5nm. Then, it was ultrasonically cleaned in acetone, ethanol and deionized water for 20 minutes each. After cleaning, it was placed in a clean drying oven and dried at 80℃ for 2 hours.

[0051] In step two, the main polarization electric field is applied using a stepped voltage boosting method, specifically as follows: First, apply an initial electric field of 0.5 kV / mm and maintain it for 10 minutes, then gradually increase it to the target field strength at a rate of 0.3 kV / min. The environment inside the polarization device is a silicone oil or inert gas atmosphere to prevent oxidation of the single crystal during high-temperature polarization.

[0052] In the construction of the interface modification layer, when physical vapor deposition is used, the process parameters are: sputtering power 300W, working pressure 2.0Pa, substrate temperature 200℃, and deposition rate 0.5nm / s. When using spin coating, the interface modification layer material is first dispersed in an organic solvent to form a slurry with a solid content of 30wt%. The spin coating speed is 5000rpm and the spin coating time is 60 seconds. Then, the solvent is removed by preheating at 120℃ for 20 minutes.

[0053] In the raw materials of the interface modification layer, the glass powder is borosilicate glass or phosphate glass with a softening point temperature of 600℃. The precursor of the organosilicon resin is methyltriethoxysilane or tetraethyl orthosilicate; The coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0054] The gradient annealing process in step four involves the first stage of heating under a nitrogen protective atmosphere with an oxygen content of less than 50 ppm to prevent the interface modification layer and the single crystal surface from deteriorating at high temperatures.

[0055] The stabilizing bias electric field in step five is applied as a DC electric field or a quasi-DC square wave electric field with a frequency of less than 1 Hz and a duty cycle of 80%.

[0056] Following step five, the following is also included: Step 6: Protective layer encapsulation. The single crystal treated with the stabilized electric field is vacuum encapsulated using epoxy resin or parylene to form a protective layer with a thickness of 100 micrometers. The encapsulation process is carried out at room temperature to 60°C.

[0057] The epoxy resin is a bisphenol A type epoxy resin, and its curing agent is an acid anhydride or amine curing agent. The mass ratio of epoxy resin to curing agent is 5:1. Parylene was deposited using chemical vapor deposition at a deposition chamber pressure of 50 Pa and a deposition rate of 2 μm / h.

[0058] Trigonal relaxor ferroelectric single crystals are lead magnesium niobate-lead titanate, lead zinc niobate-lead titanate, or lead indium niobate-lead titanate relaxor ferroelectric single crystals, and the crystallographic direction of their <001> orientation deviates from the direction of the main polarization electric field by less than 5°.

[0059] Comparative Example 1: The difference between this comparative example and Example 1 is that no interface modification layer was constructed in this comparative example.

[0060] Comparative Example 2 differs from Example 1 in that gradient annealing was not performed in this comparative example.

[0061] Comparative Example 3 differs from Example 1 in that no stabilizing bias electric field is applied in this comparative example.

[0062] Comparative Example 4 differs from Example 1 in that it is not encapsulated with a protective layer.

[0063] The performance of the trigonal phase relaxor ferroelectric single crystals prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test items and test methods are as follows: The piezoelectric constant d33 was measured at room temperature (25℃) and frequency (100Hz) using a quasi-static d33 measuring instrument with a pressure of 0.25N. Dielectric loss testing was conducted at a frequency of 1kHz and a voltage of 1Vrms using an impedance analyzer to measure the dielectric constant and loss tangent. Depolarization rate test: aged at 150℃ for 100 hours, then cooled to room temperature, and the percentage decrease of piezoelectric constant d33 was measured. Bending strength was tested using a universal testing machine.

[0064] The test data of the trigonal relaxor ferroelectric single crystals prepared in Examples 1-3 and Comparative Examples 1-4 are recorded in the table below: By comparing and analyzing the data in the table, it can be seen that the trigonal phase relaxor ferroelectric single crystals prepared by the methods in Examples 1-3 have significantly better performance than the single crystals prepared by the methods in Comparative Examples 1-4. This indicates that the present invention, through single crystal pretreatment and polarization electric field optimization, ensures a smooth and clean single crystal surface and applies the main polarization electric field in a protective atmosphere using a stepped voltage boosting method, avoiding single crystal oxidation damage and improving polarization effect, thus laying the foundation for depolarization suppression. Through interface modification layer construction and gradient annealing, a high dielectric constant interface layer is formed on the single crystal surface, and internal stress is eliminated in a protective atmosphere through multi-stage programmed temperature-controlled annealing, enhancing the interface bonding strength and crystal structure stability, and suppressing the depolarization process. Through the application of a stabilizing bias electric field and protective layer encapsulation, the polarization state is further stabilized using a DC or quasi-DC electric field, and a protective layer is formed through vacuum encapsulation to prevent performance degradation caused by environmental factors, thereby achieving depolarization suppression.

[0065] By comparing and analyzing the relevant data in the table, it can be seen that the trigonal phase relaxor ferroelectric single crystal prepared by the method of the present invention has a high piezoelectric constant, low dielectric loss, low depolarization and good mechanical strength.

[0066] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing depolarization in trigonal phase relaxor ferroelectric single crystals based on interface modification, characterized in that: The method comprises the following steps: Step 1: single crystal pretreatment, selecting a rhombohedral relaxor ferroelectric single crystal, polishing, cleaning and drying the surface; Step 2: polarization field optimization, placing the pretreated single crystal in a controllable temperature polarization device, applying a main polarization electric field with a field strength of 0.5-3.0 kV / mm along the spontaneous polarization direction, a polarization temperature of 80-150℃, and a polarization time of 10-60 minutes; Step 3: interface modification layer construction, preparing an interface modification layer with a thickness of 10-500 nm on the surface of the polarized single crystal; Step 4: gradient annealing treatment, placing the single crystal in a program-controlled temperature furnace for multi-stage gradient annealing, first increasing the temperature to 200-300℃ at a rate of 1-5℃ / min and maintaining for 30-90 minutes, then decreasing the temperature to 100-180℃ at a rate of 0.5-2℃ / min and maintaining for 60-180 minutes, and finally cooling with the furnace; Step 5: application of a stabilizing electric field, applying a stabilizing bias electric field with a field strength of 0.1-0.8 kV / mm and the same direction as the main polarization electric field at room temperature, and the application time is 1-24 hours; The interface modification layer is made of 40-60 parts of high dielectric constant ceramic powder, 10-20 parts of glass powder, 20-30 parts of organic silicon resin precursor, and 1-5 parts of coupling agent.

2. The method of depolarization suppression of a ternary phase relaxor ferroelectric single crystal based on interface modification according to claim 1, characterized in that: In step 1, the single crystal pretreatment comprises the following steps: The surface of the single crystal is finely polished with diamond polishing liquid to a surface roughness Ra≤5 nm, then ultrasonic cleaning in acetone, ethanol and deionized water for 10-20 minutes respectively, and then drying in a clean dry box at 60-80℃ for 1-2 hours.

3. The method of claim 1, wherein the interface-modified ternary relaxor ferroelectric single crystal is represented by the formula: (1-x)Pb(Mg1 / 3Nb2 / 3)O3-xPbTiO3. In step 2, the application of the main polarization electric field uses a step-by-step voltage increasing method, specifically: First apply an initial electric field of 0.2-0.5 kV / mm for 5-10 minutes, then gradually increase to the target field strength at a rate of 0.1-0.3 kV / min; The environment in the polarization device is silicon oil or inert gas atmosphere to prevent oxidation of the single crystal during high-temperature polarization.

4. The method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification according to claim 1, characterized in that: In the construction of the interface modification layer, when using physical vapor deposition, the process parameters are: sputtering power 100-300 W, working pressure 0.5-2.0 Pa, substrate temperature 100-200℃, deposition rate 0.1-0.5 nm / s; When using spin coating, first disperse the interface modification layer raw materials in an organic solvent to form a slurry with a solid content of 10-30 wt%, spin coating speed 2000-5000 rpm, spin coating time 30-60 seconds, then pre-treatment at 80-120℃ for 10-20 minutes to remove the solvent.

5. The method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification according to claim 1, characterized in that: In the interface modification layer raw materials, the high dielectric constant ceramic powder is barium titanate, strontium titanate or lead-based perovskite ceramic powder; The glass powder is borosilicate glass or phosphate glass, with a softening point temperature of 400-600℃; The organic silicon resin precursor is methyl triethoxysilane or tetraethyl orthosilicate; The coupling agent is γ-aminopropyl triethoxysilane or γ-glycidyl ether propyl trimethoxysilane.

6. The method of suppressing depoling in an interface-modified ternary phase relaxor ferroelectric single crystal according to claim 1, wherein: The gradient annealing process in the fourth step is performed in a nitrogen atmosphere with an oxygen content less than 50 ppm to prevent the interface modification layer and the single crystal surface from being deteriorated at high temperature.

7. The method of suppressing depoling in an interface-modified ternary phase relaxor ferroelectric single crystal according to claim 1, wherein: The stabilizing bias electric field in the fifth step is a direct current electric field or a quasi-direct current square wave electric field with a frequency less than 1 Hz and a duty cycle of 50%-80%.

8. The method of suppressing depoling in an interface-modified ternary phase relaxor ferroelectric single crystal according to claim 1, wherein: After the fifth step, the following steps are further included: Step six: protective layer packaging, the single crystal treated by the stabilizing electric field is packaged by epoxy resin or poly-p-xylylene to form a protective layer with a thickness of 10-100 microns, and the packaging process is performed at room temperature to 60℃.

9. A method for suppressing depolarization of trigonal phase relaxor ferroelectric single crystals based on interface modification according to claim 8, characterized in that: The epoxy resin is bisphenol A type epoxy resin, and the curing agent is anhydride or amine curing agent, and the mass ratio of the epoxy resin to the curing agent is 10:1 to 5:

1. The poly-p-xylylene is deposited by chemical vapor deposition, and the deposition chamber pressure is 10-50 Pa, and the deposition rate is 0.5-2 microns / hour.

10. The method of suppressing depoling in an interface-modified ternary phase relaxor ferroelectric single crystal according to claim 1, wherein: The trigonal phase relaxor ferroelectric single crystal is a lead magnesium niobate-lead titanate, lead zinc niobate-lead titanate or lead indium niobate-lead titanate relaxor ferroelectric single crystal, and the deviation between the crystallographic direction of the < 001 > orientation and the direction of the main polarization electric field is less than 5°.

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