Preparation method of high fatigue resistance lead-free piezoelectric thin film

Abstract

This invention relates to the field of piezoelectric materials and discloses a method for preparing a high-fatigue-resistant lead-free piezoelectric thin film. The method uses magnetron sputtering to directly prepare a lead-free piezoelectric thin film with a top electrode. The thin film layer of the lead-free piezoelectric thin film is a pure-phase potassium sodium niobate ceramic. An adhesive layer is disposed between the pure-phase potassium sodium niobate and the top electrode layer. The sputtering target for the adhesive layer is one or more of titanium, zirconium, ruthenium, titanium oxide, ruthenium oxide, and lanthanum nickelate. During the annealing process, the adhesive layer undergoes oxidation to form an oxide layer, which significantly improves the adhesion of the adhesive layer to the top electrode layer. The adhesive layer also significantly inhibits the volatilization of alkali metal elements in the thin film layer and significantly improves the fatigue resistance of the potassium sodium niobate thin film. The lead-free piezoelectric thin film prepared by this method exhibits high fatigue resistance at 10°C. 8 After the second electrical fatigue cycle, the residual polarization showed no significant decay.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric materials, and in particular to a method for preparing a high fatigue-resistant lead-free piezoelectric thin film. Background Technology

[0002] Piezoelectric materials are functional materials capable of electromechanical coupling conversion under the action of an applied electric field and mechanical stress, and are widely used in devices such as sensors, actuators, and microelectromechanical systems (MEMS). Existing piezoelectric ceramic materials are mostly based on lead-containing zirconium lead titanate (PZT) systems. However, lead poses environmental and health hazards, and international regulations have spurred research into lead-free alternatives. Among these, lead-free systems, represented by potassium sodium niobate (KNN), are considered the most promising environmentally friendly piezoelectric materials due to their high Curie temperature and good piezoelectric properties. However, potassium sodium niobate-based ceramic materials struggle to maintain their original long and intact hysteresis loops after repeated application of an external electric field, exhibiting poor fatigue resistance and hindering their practical application.

[0003] To address the poor fatigue resistance of potassium sodium niobate-based ceramic materials, relevant technical solutions have been disclosed in the prior art. For example, CN117285352B discloses a potassium sodium niobate-based ceramic material with excellent fatigue resistance and its preparation method, which provides a (1-x)K 0.5 Na 0.5 NbO3-x(Sr 0.7 La 0.2 (Mg) 1 / 3 Nb 2 / 3 O3, x is 0.03~0.12. Another example is CN113461422B, a high-voltage, fatigue-resistant potassium sodium niobate-based lead-free piezoelectric ceramic. Porcelain and its preparation method, wherein K is provided 0.48 Na 0.52 NbO3-xNaSbO3Bi 0.5 Na 0.5 A ZrO3-0.2%Fe2O3 potassium sodium niobate-based ceramic material, wherein 0.03≤x≤0.055, is used. This technical solution improves the piezoelectric properties, polarization intensity, and fatigue resistance of the piezoelectric ceramic by controlling the NaSbO3 content to form a multiphase coexistence at room temperature. Furthermore, the fatigue resistance of potassium sodium niobate ceramics can be improved by introducing elements such as manganese and tantalum to suppress oxygen vacancy migration. However, this method leads to the enrichment of dopants at grain boundaries during film growth, resulting in a decrease in the performance of the potassium sodium niobate-based piezoelectric film. Therefore, it is of great significance to provide a method that improves the fatigue resistance of potassium sodium niobate-based piezoelectric films without reducing their performance. Summary of the Invention

[0004] This invention provides a method for preparing a high-fatigue-resistant lead-free piezoelectric thin film. The method directly prepares a lead-free piezoelectric thin film with a top electrode using magnetron sputtering. First, a bonding layer and a top electrode layer are sequentially deposited on the thin film layer using magnetron sputtering to form a stacked structure. Then, the stacked structure is annealed to obtain the high-fatigue-resistant lead-free piezoelectric thin film. This method introduces a bonding layer between the top electrode and the potassium sodium niobate thin film. The sputtering target for the bonding layer is titanium, zirconium, ruthenium, titanium oxide, ruthenium oxide, and lanthanum nickelate. During annealing, the bonding layer oxidizes to form an oxide layer, effectively improving the adhesion of the top electrode layer. This oxide layer can reduce the volatilization of alkali metal elements during annealing, improve the crystallinity of the thin film, and also increase the oxygen vacancy migration barrier, constructing a diffusion barrier and improving the fatigue resistance of the potassium sodium niobate thin film.

[0005] The specific technical solution of this invention is as follows: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: hot pressing potassium sodium niobate raw material into a ceramic target, and preparing a thin film layer by magnetron sputtering of the ceramic target; then, using magnetron sputtering, sequentially setting an adhesive layer and a top electrode layer on the thin film layer to form a stacked structure; and then annealing the precursor to prepare a high fatigue-resistant lead-free piezoelectric thin film. The target material for sputtering the adhesive layer is one or more of titanium, zirconium, ruthenium, titanium oxide, ruthenium oxide, and lanthanum nickelate, and the thin film layer is potassium sodium niobate ceramic.

[0006] Preferably, the conditions for magnetron sputtering include: the working gas is one of argon and argon-oxygen mixture, the working gas pressure is 0.6~1.3 Pa, the power is 40~200 W, and the substrate temperature is set to 200~300 ℃.

[0007] Preferably, the argon-oxygen ratio of the argon-oxygen mixture is 10:1, and the pressure of the argon-oxygen mixture is 0.6 Pa.

[0008] Preferably, the pressure of argon gas is 1.3 Pa.

[0009] Preferably, the pressure of argon gas is 0.4 Pa.

[0010] Preferably, the thickness of the adhesive layer is 10~20 nm.

[0011] Preferably, the thickness of the top electrode layer is 200~300 nm.

[0012] Preferably, the annealing temperature is 600~700 ℃.

[0013] Preferably, the pressure for hot pressing is 60~80 MPa. Preferably, the hot pressing conditions are as follows: heat to 900 ℃ at a heating rate of 10 ℃ / min, hold at that temperature for 2 h, then cool to 800 ℃ at a cooling rate of 2 ℃ / min, remove the pressure, and cool to room temperature.

[0014] Preferably, the substrate for magnetron sputtering is a platinum-plated silicon wafer.

[0015] This invention provides a method for preparing a high fatigue-resistant lead-free piezoelectric thin film. The method uses magnetron sputtering to directly prepare a lead-free piezoelectric thin film with a top electrode. The thin film layer of the lead-free piezoelectric thin film is a pure phase potassium sodium niobate ceramic. An adhesive layer is provided between the thin film layer and the top electrode. The target material for sputtering the adhesive layer is one or more of titanium, zirconium, ruthenium, titanium oxide, ruthenium oxide, and lanthanum nickelate. During the annealing process, the adhesive layer undergoes oxidation to form an oxide layer, which can significantly improve the adhesion of the adhesive layer to the top electrode layer. It can also inhibit the volatilization of alkali metal elements in the thin film layer during the annealing process, improve the crystallinity of the thin film layer, and enhance the oxygen vacancy migration barrier, construct a diffusion barrier, and improve the fatigue resistance of the potassium sodium niobate thin film.

[0016] Compared with the prior art, this application has the following technical effects: This method directly prepares lead-free piezoelectric thin films with top electrodes using magnetron sputtering. The thin film layer is a pure-phase potassium sodium niobate ceramic, and an adhesive layer is placed between the pure-phase potassium sodium niobate and the top electrode layer. The sputtering target for the adhesive layer is one or more of titanium, zirconium, ruthenium, titanium oxide, ruthenium oxide, and lanthanum nickelate. During the annealing process, the adhesive layer undergoes oxidation to form an oxide layer, which significantly improves the adhesion of the adhesive layer to the top electrode layer. The adhesive layer also significantly inhibits the volatilization of alkali metal elements in the thin film layer and significantly improves the fatigue resistance of the potassium sodium niobate thin film. The lead-free piezoelectric thin film prepared by this method has a high tensile strength at 10 °C. 8 After the second electrical fatigue cycle, the residual polarization showed no significant decay. Attached Figure Description

[0017] Figure 1 The images show the XRD diffraction patterns of the piezoelectric thin film layers of Example 1 and Comparative Example 1. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments.

[0019] To better understand the content of this invention, further explanation is provided below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of this invention.

[0020] Example 1: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: (1) Niobium pentoxide, potassium carbonate and sodium carbonate are ball-milled and mixed in proportion, and sintered into potassium sodium niobate powder. The potassium sodium niobate powder is dry-pressed to form a blank by applying a pressure of 70 MPa through a metal mold. Then, a constant pressure of 30 MPa is applied along the outer axis of the blank and the blank is heated to 900 ℃ at a heating rate of 10 ℃ / min under argon atmosphere. The blank is hot-pressed and sintered for 2 h. Then, the temperature is cooled at a cooling rate of 2 ℃ / min. When the temperature drops to 800 ℃, the pressure is removed. After cooling to room temperature, the surface is polished to form a ceramic target. (2) Clean the substrate surface with alcohol, then dry the substrate with high-purity nitrogen, and then use low-temperature silver paste to adhere the substrate to the sample stage to form a substrate. Heat the silver paste at 150 °C for 1 min on the heating stage to solidify it. Install the sample stage and ceramic target into the corresponding positions of the magnetron sputtering device, and then evacuate the cavity to 5 × 10⁻⁶. -4 Pa, start the heating function to heat the sample stage to 300 ℃, use radio frequency magnetron mode to sputter the thin film layer, sputtering parameters are set as follows: atmosphere argon-oxygen mixture (argon:oxygen=10:1, pressure 0.6 Pa), power 150 W, sputtering time 7200 s (2 h). (3) After the thin film layer sputtering is completed, the binder layer and the top electrode layer are sputtered sequentially using the DC magnetron sputtering target of the magnetron sputtering device. The sputtering parameters of the binder layer are: target material is titanium, room temperature, argon atmosphere (pure argon, pressure 1.3 Pa), power 80 W, sputtering time 600 s, and the thickness of the binder layer is 15 nm. The sputtering parameters of the top electrode layer are: target material is platinum, room temperature, argon atmosphere (pure argon, pressure 0.4 Pa), power 40 W, sputtering time 1200 s, and the thickness of the top electrode layer is 250 nm. After the top electrode layer sputtering is completed, the sample stage is removed, the mask is removed, and the silver paste on the back of the sample is cleaned to form a stacked structure. (4) The precursor is placed in an alumina crucible and transferred to a muffle furnace for annealing. The annealing parameters are: heating to 700 °C at a heating rate of 5 °C / min and holding for 2 h. After holding, the sample is allowed to cool naturally to room temperature to form a high fatigue-resistant lead-free piezoelectric film. The high fatigue-resistant lead-free piezoelectric film includes a substrate, a thin film layer on the substrate, and an adhesive layer and a top electrode layer on the thin film layer. The adhesive layer bonds the thin film layer and the top electrode layer.

[0021] Example 2: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: (1) Niobium pentoxide, potassium carbonate and sodium carbonate are ball-milled and mixed in proportion, and sintered into potassium sodium niobate powder. The potassium sodium niobate powder is dry-pressed to form a blank by applying a pressure of 70 MPa through a metal mold. Then, a constant pressure of 30 MPa is applied along the outer axis of the blank and the blank is heated to 900 ℃ at a heating rate of 10 ℃ / min under argon atmosphere. The blank is hot-pressed and sintered for 2 h. Then, the temperature is cooled at a cooling rate of 2 ℃ / min. When the temperature drops to 800 ℃, the pressure is removed. After cooling to room temperature, the surface is polished to form a ceramic target. (2) Clean the substrate surface with alcohol, then dry the substrate with high-purity nitrogen, and then use low-temperature silver paste to adhere the substrate to the sample stage to form a substrate. Heat the silver paste at 150 °C for 1 min on the heating stage to solidify it. Install the sample stage and ceramic target into the corresponding positions of the magnetron sputtering device, and then evacuate the cavity to 5 × 10⁻⁶. -4 Pa, start the heating function to heat the sample stage to 300 ℃, use radio frequency magnetron mode to sputter the thin film layer, sputtering parameters are set as follows: atmosphere argon-oxygen mixture (argon:oxygen=10:1, pressure 0.6 Pa), power 150 W, sputtering time 7200 s (2 h). (3) After the thin film layer sputtering is completed, the binder layer and the top electrode layer are sputtered sequentially using the DC magnetron sputtering target of the magnetron sputtering device. The sputtering parameters of the binder layer are: zirconium target, room temperature, argon atmosphere (pure argon, pressure 1.3 Pa), power 80 W, sputtering time 600 s, and the thickness of the binder layer is 15 nm. The sputtering parameters of the top electrode layer are: platinum target, room temperature, argon atmosphere (pure argon, pressure 0.4 Pa), power 40 W, sputtering time 1200 s, and the thickness of the top electrode layer is 250 nm. After the top electrode layer sputtering is completed, the sample stage is removed, the mask is removed, and the silver paste on the back of the sample is cleaned to form a stacked structure. (4) The precursor was placed in an alumina crucible and transferred to a muffle furnace for annealing. The annealing parameters were: heating to 700 °C at a heating rate of 5 °C / min and holding for 2 h. After holding, the sample was allowed to cool naturally to room temperature to prepare a high fatigue-resistant lead-free piezoelectric film.

[0022] Example 3: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: (1) Niobium pentoxide, potassium carbonate and sodium carbonate are ball-milled and mixed in proportion, and sintered into potassium sodium niobate powder. The potassium sodium niobate powder is dry-pressed to form a blank by applying a pressure of 70 MPa through a metal mold. Then, a constant pressure of 30 MPa is applied along the outer axis of the blank and the blank is heated to 900 ℃ at a heating rate of 10 ℃ / min under argon atmosphere. The blank is hot-pressed and sintered for 2 h. Then, the temperature is cooled at a cooling rate of 2 ℃ / min. When the temperature drops to 800 ℃, the pressure is removed. After cooling to room temperature, the surface is polished to form a ceramic target. (2) Clean the substrate surface with alcohol, then dry the substrate with high-purity nitrogen, and then use low-temperature silver paste to adhere the substrate to the sample stage to form a substrate. Heat the silver paste at 150 °C for 1 min on the heating stage to solidify it. Install the sample stage and ceramic target into the corresponding positions of the magnetron sputtering device, and then evacuate the cavity to 5 × 10⁻⁶. -4 Pa, start the heating function to heat the sample stage to 300 ℃, use radio frequency magnetron mode to sputter the thin film layer, sputtering parameters are set as follows: atmosphere argon-oxygen mixture (argon:oxygen=10:1, pressure 0.6 Pa), power 150 W, sputtering time 7200 s (2 h). (3) After the thin film layer sputtering is completed, the binder layer and the top electrode layer are sputtered sequentially using the DC magnetron sputtering target of the magnetron sputtering device. The sputtering parameters of the binder layer are: the target material is ruthenium, room temperature, argon atmosphere (pure argon, pressure 1.3 Pa), power 80 W, sputtering time 600 s, and the thickness of the binder layer is 15 nm. The sputtering parameters of the top electrode layer are: the target material is platinum, room temperature, argon atmosphere (pure argon, pressure 0.4 Pa), power 40 W, sputtering time 1200 s, and the thickness of the top electrode layer is 250 nm. After the top electrode layer sputtering is completed, the sample stage is removed, the mask is removed, and the silver paste on the back of the sample is cleaned to form a stacked structure. (4) The precursor was placed in an alumina crucible and transferred to a muffle furnace for annealing. The annealing parameters were: heating to 700 °C at a heating rate of 5 °C / min and holding for 2 h. After holding, the sample was allowed to cool naturally to room temperature to prepare a high fatigue-resistant lead-free piezoelectric film.

[0023] Example 4: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: (1) Niobium pentoxide, potassium carbonate and sodium carbonate are ball-milled and mixed in proportion, and sintered into potassium sodium niobate powder. The potassium sodium niobate powder is dry-pressed to form a blank by applying a pressure of 70 MPa through a metal mold. Then, a constant pressure of 30 MPa is applied along the outer axis of the blank and the blank is heated to 900 ℃ at a heating rate of 10 ℃ / min under argon atmosphere. The blank is hot-pressed and sintered for 2 h. Then, the temperature is cooled at a cooling rate of 2 ℃ / min. When the temperature drops to 800 ℃, the pressure is removed. After cooling to room temperature, the surface is polished to form a ceramic target. (2) Clean the substrate surface with alcohol, then dry the substrate with high-purity nitrogen, and then use low-temperature silver paste to adhere the substrate to the sample stage to form a substrate. Heat the silver paste at 150 °C for 1 min on the heating stage to solidify it. Install the sample stage and ceramic target into the corresponding positions of the magnetron sputtering device, and then evacuate the cavity to 5 × 10⁻⁶. -4 Pa, start the heating function to heat the sample stage to 300 ℃, use radio frequency magnetron mode to sputter the thin film layer, sputtering parameters are set as follows: atmosphere argon-oxygen mixture (argon:oxygen=10:1, pressure 0.6 Pa), power 150 W, sputtering time 7200 s (2 h). (3) After the thin film layer sputtering is completed, the binder layer and the top electrode layer are sputtered sequentially using the DC magnetron sputtering target of the magnetron sputtering device. The sputtering parameters of the binder layer are: target material is titanium oxide, room temperature, argon atmosphere (pure argon, pressure 1.3 Pa), power 80 W, sputtering time 600 s, and the thickness of the binder layer is 15 nm. The sputtering parameters of the top electrode layer are: target material is platinum, room temperature, argon atmosphere (pure argon, pressure 0.4 Pa), power 40 W, sputtering time 1200 s, and the thickness of the top electrode layer is 250 nm. After the top electrode layer sputtering is completed, the sample stage is removed, the mask is removed, and the silver paste on the back of the sample is cleaned to form a stacked structure. (4) The precursor was placed in an alumina crucible and transferred to a muffle furnace for annealing. The annealing parameters were: heating to 700 °C at a heating rate of 5 °C / min and holding for 2 h. After holding, the sample was allowed to cool naturally to room temperature to prepare a high fatigue-resistant lead-free piezoelectric film.

[0024] Example 5: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: (1) Niobium pentoxide, potassium carbonate and sodium carbonate are ball-milled and mixed in proportion, and sintered into potassium sodium niobate powder. The potassium sodium niobate powder is dry-pressed to form a blank by applying a pressure of 70 MPa through a metal mold. Then, a constant pressure of 30 MPa is applied along the outer axis of the blank and the blank is heated to 900 ℃ at a heating rate of 10 ℃ / min under argon atmosphere. The blank is hot-pressed and sintered for 2 h. Then, the temperature is cooled at a cooling rate of 2 ℃ / min. When the temperature drops to 800 ℃, the pressure is removed. After cooling to room temperature, the surface is polished to form a ceramic target. (2) Clean the substrate surface with alcohol, then dry the substrate with high-purity nitrogen, and then use low-temperature silver paste to adhere the substrate to the sample stage to form a substrate. Heat the silver paste at 150 °C for 1 min on the heating stage to solidify it. Install the sample stage and ceramic target into the corresponding positions of the magnetron sputtering device, and then evacuate the cavity to 5 × 10⁻⁶. -4 Pa, start the heating function to heat the sample stage to 300 ℃, use radio frequency magnetron mode to sputter the thin film layer, sputtering parameters are set as follows: atmosphere argon-oxygen mixture (argon:oxygen=10:1, pressure 0.6 Pa), power 150 W, sputtering time 7200 s (2 h). (3) After the thin film sputtering is completed, the binder layer and the top electrode layer are sputtered sequentially using the DC magnetron sputtering target of the magnetron sputtering device. The sputtering parameters of the binder layer are: target material is zirconium oxide, room temperature, argon atmosphere (pure argon, pressure 1.3 Pa), power 80 W, sputtering time 600 s, and the thickness of the binder layer is 15 nm. The sputtering parameters of the top electrode layer are: target material is platinum, room temperature, argon atmosphere (pure argon, pressure 0.4 Pa), power 40 W, sputtering time 1200 s, and the thickness of the top electrode layer is 250 nm. After the top electrode layer sputtering is completed, the sample stage is removed, the mask is removed, and the silver paste on the back of the sample is cleaned to form a stacked structure. (4) The precursor was placed in an alumina crucible and transferred to a muffle furnace for annealing. The annealing parameters were: heating to 700 °C at a heating rate of 5 °C / min and holding for 2 h. After holding, the sample was allowed to cool naturally to room temperature to prepare a high fatigue-resistant lead-free piezoelectric film.

[0025] Example 6: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: (1) Niobium pentoxide, potassium carbonate and sodium carbonate are ball-milled and mixed in proportion, and sintered into potassium sodium niobate powder. The potassium sodium niobate powder is dry-pressed to form a blank by applying a pressure of 60 MPa through a metal mold. Then, a constant pressure of 30 MPa is applied along the outer axis of the blank and the blank is heated to 900 ℃ at a heating rate of 10 ℃ / min under argon atmosphere. The blank is hot-pressed and sintered for 2 h. Then, the temperature is cooled at a cooling rate of 2 ℃ / min. When the temperature drops to 800 ℃, the pressure is removed. After cooling to room temperature, the surface is polished to form a ceramic target. (2) Clean the substrate surface with alcohol, then dry the substrate with high-purity nitrogen, and then use low-temperature silver paste to adhere the substrate to the sample stage to form a substrate. Heat the silver paste at 150 °C for 1 min on the heating stage to solidify it. Install the sample stage and ceramic target into the corresponding positions of the magnetron sputtering device, and then evacuate the cavity to 5 × 10⁻⁶. -4 Pa, start the heating function to heat the sample stage to 300 ℃, use radio frequency magnetron mode to sputter the thin film layer, sputtering parameters are set as follows: atmosphere argon-oxygen mixture (argon:oxygen=10:1, pressure 0.6 Pa), power 150 W, sputtering time 7200 s (2 h). (3) After the thin film layer sputtering is completed, the binder layer and the top electrode layer are sputtered sequentially using the DC magnetron sputtering target of the magnetron sputtering device. The sputtering parameters of the binder layer are: target material is lanthanum nickelate, room temperature, argon atmosphere (pure argon, pressure 1.3 Pa), power 80 W, sputtering time 600 s, and the thickness of the binder layer is 10 nm. The sputtering parameters of the top electrode layer are: target material is platinum, room temperature, argon atmosphere (pure argon, pressure 0.4 Pa), power 40 W, sputtering time 1200 s, and the thickness of the top electrode layer is 200 nm. After the top electrode layer sputtering is completed, the sample stage is removed, the mask is removed, and the silver paste on the back of the sample is cleaned to form a stacked structure. (4) The precursor was placed in an alumina crucible and transferred to a muffle furnace for annealing. The annealing parameters were: heating to 700 °C at a heating rate of 5 °C / min and holding for 2 h. After holding, the sample was allowed to cool naturally to room temperature to prepare a high fatigue-resistant lead-free piezoelectric film.

[0026] Example 7: A method for preparing a high fatigue-resistant lead-free piezoelectric thin film includes the following steps: (1) Niobium pentoxide, potassium carbonate and sodium carbonate are ball-milled and mixed in proportion, and sintered into potassium sodium niobate powder. The potassium sodium niobate powder is dry-pressed to form a blank by applying a pressure of 80 MPa through a metal mold. Then, a constant pressure of 30 MPa is applied along the outer axis of the blank and the blank is heated to 900 ℃ at a heating rate of 10 ℃ / min under argon atmosphere. The blank is hot-pressed and sintered for 2 h. Then, the temperature is cooled at a cooling rate of 2 ℃ / min. When the temperature drops to 800 ℃, the pressure is removed. After cooling to room temperature, the surface is polished to form a ceramic target. (2) Clean the substrate surface with alcohol, then dry the substrate with high-purity nitrogen, and then use low-temperature silver paste to adhere the substrate to the sample stage to form a substrate. Heat the silver paste at 150 °C for 1 min on the heating stage to solidify it. Install the sample stage and ceramic target into the corresponding positions of the magnetron sputtering device, and then evacuate the cavity to 5 × 10⁻⁶. -4 Pa, start the heating function to heat the sample stage to 300 ℃, use radio frequency magnetron mode to sputter the thin film layer, sputtering parameters are set as follows: atmosphere argon-oxygen mixture (argon:oxygen=10:1, pressure 0.6 Pa), power 150 W, sputtering time 7200 s (2 h). (3) After the thin film layer sputtering is completed, the binder layer and the top electrode layer are sputtered sequentially using the DC magnetron sputtering target of the magnetron sputtering device. The sputtering parameters of the binder layer are: target material is titanium, room temperature, argon atmosphere (pure argon, pressure 1.3 Pa), power 80 W, sputtering time 600 s, and the thickness of the binder layer is 20 nm. The sputtering parameters of the top electrode layer are: target material is platinum, room temperature, argon atmosphere (pure argon, pressure 0.4 Pa), power 40 W, sputtering time 1200 s, and the thickness of the top electrode layer is 300 nm. After the top electrode layer sputtering is completed, the sample stage is removed, the mask is removed, and the silver paste on the back of the sample is cleaned to form a stacked structure. (4) The precursor was placed in an alumina crucible and transferred to a muffle furnace for annealing. The annealing parameters were: heating to 700 °C at a heating rate of 5 °C / min and holding for 2 h. After holding, the sample was allowed to cool naturally to room temperature to prepare a high fatigue-resistant lead-free piezoelectric film.

[0027] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that no adhesive layer was provided, while all other conditions were the same as in Example 1.

[0028] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the thin film layer was annealed first, and then the adhesive layer and top electrode layer were magnetron sputtered after the thin film layer was annealed. All other conditions were the same as in Example 1.

[0029] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that the adhesive layer is too thick, with a thickness of 30 nm. All other conditions are the same as in Example 1.

[0030] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that the thickness of the top electrode layer is too low, and the thickness of the top electrode layer is 100 nm. All other conditions are the same as in Example 1.

[0031] Detection Example 1: XRD diffraction was performed on the thin film layers of the high fatigue-resistant lead-free piezoelectric films prepared in Examples 1 to 7 and Comparative Examples 1 to 4. The test results are shown in [Figure 1]. Figure 1 .

[0032] like Figure 1 As shown, no secondary phase was observed in the thin film layers prepared in Example 1 and Comparative Example 1. However, the peak intensity of Example 1 was significantly higher than that of Comparative Example 1. This result indicates that the addition of an adhesive layer can significantly suppress the volatilization of alkali metal elements during the annealing process and significantly improve the crystallinity of the thin film. In contrast, the thin film layer without an adhesive layer exhibits strong alkali metal volatility at a high temperature of 700 °C, which leads to a decrease in the crystallinity of the thin film.

[0033] Detection Example 2: The relative remanent polarization and adhesion of the high fatigue-resistant lead-free piezoelectric films prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were tested. The testing method was as follows: The prepared piezoelectric thin film was subjected to a double-cycle ferroelectric test using a ferroelectric testing instrument. The temperature was room temperature, the voltage was ±40 V, the test frequency was 1 kHz, and the test duration was 10 minutes. 8 Record 10 times respectively. 0 10 5 and 10 8 The relative remanent polarization value; The adhesion strength test method was conducted according to the method disclosed in GB / T 45345-2025: Measurement of adhesion of metallic and other inorganic coatings for engineering DC magnetron sputtering silver coatings and nano-scratch test. The test results are shown in Table 1. Table 1 Test Results As shown in Table 1, the table displays the fatigue resistance (relative remanent polarization) and adhesion strength (adhesion) of the piezoelectric films prepared in Examples 1-7 and Comparative Examples 1-4. The results show that the piezoelectric films of Examples 1-7, after 10... 8 The relative remanent polarization value after one ferroelectric cycle is still above 0.94, and the difference from the initial remanent polarization value is less than 10%. This result indicates that the piezoelectric thin film prepared by the present invention has excellent fatigue resistance.

[0034] Comparative Example 1 is a technical solution without an adhesive layer, and the piezoelectric film produced therefrom undergoes 10... 8 The relative remanent polarization value after the second ferroelectric cycle decreased to 0.68, with a difference of 32% from the initial remanent polarization value. The fatigue resistance was significantly lower than that of Example 1. This result indicates that the fatigue resistance of the piezoelectric film can be significantly improved by setting an adhesive layer.

[0035] Comparative Example 2 uses a technique of annealing the thin film layer before applying the adhesive layer and top electrode layer. The initial relative remanent polarization of the piezoelectric thin film obtained in Comparative Example 2 is only 0.83, significantly lower than that in Example 1. This result indicates that directly annealing the thin film layer leads to a significant reduction in the piezoelectric properties of the piezoelectric thin film. Furthermore, the piezoelectric thin film obtained in Comparative Example 1 undergoes 10... 8 The relative residual polarization decreased by 6% after one ferroelectric cycle, which also shows that the adhesive layer can significantly improve the fatigue resistance of the piezoelectric film.

[0036] Analysis of the bond strength results in Examples 1 to 7 revealed that the type of material significantly affects the bond strength of the adhesive layer. Among different elemental metals, titanium exhibited the highest bond strength after annealing. Furthermore, compared to elemental metals, directly sputtered metal oxide adhesive layers showed lower bond strength. These results indicate that the bond strength of elemental metals is significantly enhanced after annealing, while the bond strength of metal oxides did not change significantly after annealing.

[0037] The effects of Comparative Examples 3 and 4 on the thickness of the adhesive layer and the top electrode layer were investigated. The results showed that an excessively thick adhesive layer would reduce the conductivity of the electrode, while an excessively thin top electrode layer would result in annealing damage and a decrease in the bonding strength of the adhesive layer.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing high fatigue resistance lead-free piezoelectric thin films, characterized by, Includes the following steps: Potassium sodium niobate raw material is hot-pressed into a ceramic target, and a thin film layer is prepared by magnetron sputtering of the ceramic target. Then, a bonding layer and a top electrode layer are sequentially set on the thin film layer by magnetron sputtering to form a stacked structure. The precursor is then annealed to form a high fatigue-resistant lead-free piezoelectric thin film. The target material for sputtering the bonding layer is one or more of titanium, zirconium, ruthenium, titanium oxide, ruthenium oxide and lanthanum nickelate, and the thin film layer is potassium sodium niobate ceramic.

2. The method of claim 1, wherein, The conditions for magnetron sputtering include: the working gas is one of argon and argon-oxygen mixture, the working gas pressure is 0.6~1.3 Pa, the power is 40~200 W, and the substrate temperature is set to 200~300 ℃.

3. The method of claim 2, wherein, The argon-oxygen mixture has an argon-oxygen ratio of 10:1 and a pressure of 0.6 Pa.

4. The method of claim 2 wherein, The pressure of argon gas is 1.3 Pa.

5. The method according to claim 2, characterized in that, The pressure of argon gas is 0.4 Pa.

6. The method according to claim 1, characterized in that, The thickness of the adhesive layer is 10~20 nm, and the thickness of the top electrode layer is 200~300 nm.

7. The method according to claim 1, characterized in that, The annealing temperature is 600~700 ℃.

8. The method according to claim 1, characterized in that, The pressure for hot pressing is 60~80 MPa.

9. The method according to claim 1, characterized in that, The hot pressing conditions are as follows: heat up to 900 ℃ at a heating rate of 10 ℃ / min, hold at that temperature for 2 h, then cool down to 800 ℃ at a cooling rate of 2 ℃ / min, remove the pressure, and cool to room temperature.

10. The method according to claim 1 or 2, characterized in that, The substrate for magnetron sputtering is a platinum-plated silicon wafer.

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