A yttrium phosphate-based piezoelectric single crystal thin film, a piezoelectric inkjet head, and a method for manufacturing the same

Abstract

This invention relates to the field of piezoelectric inkjet printing technology, specifically to a yttrium phosphate-based piezoelectric single-crystal thin film, a piezoelectric inkjet head, and a method for preparing the same. The piezoelectric thin film is formed from a high-purity yttrium phosphate ceramic target, prepared through surface timing control, spray granulation, sintering, and hot isostatic pressing densification, via radio frequency magnetron sputtering and annealing. The preparation process sequentially employs yttrium ion pre-anchoring, phytic acid dilution treatment, yttrium ion outer layer bridging, and ammonia gas phase fixation, combined with a three-stage deposition process, which improves the reliability of film adhesion and high-frequency driving stability, making it suitable for piezoelectric inkjet heads.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric inkjet printing technology, specifically to a yttrium phosphate-based piezoelectric single-crystal thin film, a piezoelectric inkjet head, and a method for preparing the same. Background Technology

[0002] Piezoelectric inkjet heads are commonly used in high-resolution patterning printing, micro-liquid dispensing, printed electronics, and functional material deposition. As droplet volume decreases and driving frequency increases, the piezoelectric driving layer not only needs a high piezoelectric response but also needs to maintain stable output after long-term cyclic driving. If the film response decays, the film-substrate interface peels off, or the pressure wave is unstable, it can easily cause droplet volume fluctuations, a decrease in jetting speed, and trajectory deviation.

[0003] Existing piezoelectric inkjet heads mostly use thin films such as lead zirconate titanate, aluminum nitride, and zinc oxide as the driving layer. Although these materials have a mature technological foundation, they are still affected by grain orientation, interfacial stress, stoichiometry, and electrode adhesion under small droplet and high-frequency driving conditions. For yttrium phosphate piezoelectric thin films, if the transition between the initial nucleation layer and the platinum under electrode is abrupt, a defect concentration area is easily formed at the interface, which weakens the adhesion reliability and long-term driving stability.

[0004] Yttrium phosphate piezoelectric films are typically obtained by magnetron sputtering from a yttrium phosphate ceramic target. The quality of the target material affects the stability of the film composition and particle defects. Existing processes focus on powder purity, powder particle size, or target density, but they lack sufficient control over phosphorus-deficient sites on the powder surface, the pore closure sequence of soft agglomerates, and the local migration of phosphate ions during sintering. This can easily lead to local phosphorus depletion on the target surface, abnormal grains, and particle sputtering, causing fluctuations in the phosphorus-yttrium ratio of the YPO4 film.

[0005] Meanwhile, powder processing, ceramic target sintering and thin film deposition are often optimized as independent processes, and there is a lack of continuous transfer between the preceding and following processes; even if the performance of a single process is good, it is difficult to solve the problems of target metering fluctuation, thin film interface abrupt change and high-frequency d33 attenuation at the same time. Summary of the Invention

[0006] In view of this, the purpose of this invention is to propose a piezoelectric single crystal thin film based on yttrium phosphate, a piezoelectric inkjet head and its preparation method, so as to solve the problems of existing yttrium phosphate inkjet head powder, target material and thin film processes being separated, which easily causes interface peeling and high frequency d33 attenuation.

[0007] To achieve the above objectives, the present invention provides a yttrium phosphate-based piezoelectric single crystal thin film, wherein the yttrium phosphate piezoelectric single crystal thin film material is obtained by radio frequency magnetron sputtering deposition and annealing of a high-purity yttrium phosphate ceramic target; The high-purity yttrium phosphate ceramic target is obtained by wet pre-dispersing high-purity yttrium phosphate powder, acid pre-adjusting it, and then sequentially treating it with a first yttrium ion dispersion, a phytic acid dilution solution, and a second yttrium ion dispersion. It is then subjected to ammonia gas phase fixation, spray granulation, calcination, pressing, sintering, hot isostatic pressing densification, and machining. The high-purity yttrium phosphate powder is calculated in parts by weight of 250, and the amounts of the first yttrium ion dispersion, phytic acid diluent, and second yttrium ion dispersion are 50 parts, 20 parts, and 20 parts, respectively.

[0008] Preferably, the high-purity yttrium phosphate powder has a purity of 99.99% and a D50 of 150-300 nm, which is a submicron or nanoscale powder.

[0009] Preferably, the amount of yttrium nitrate hexahydrate in the first yttrium ion dispersion is 0.8-1.2 parts by weight, and the remainder is deionized water.

[0010] Preferably, the amount of yttrium nitrate hexahydrate in the second yttrium ion dispersion is 1.8-2.2 parts by weight, and the remainder is deionized water.

[0011] Preferably, the phytic acid solution contains 20 parts by weight, with 1.5-2.5 parts of phytic acid and the remainder being deionized water.

[0012] Preferably, the wet pre-dispersion includes drying high-purity yttrium phosphate powder at 110-130℃ for 2 hours; adding the dried high-purity yttrium phosphate powder to a mixed dispersion medium and ball-milling at 180-220 r / min for 3-5 hours to obtain yttrium phosphate slurry; and filtering the slurry through a 200-mesh nylon sieve after ball milling.

[0013] Preferably, the acid preconditioning includes adding nitric acid to deionized water to form a dilute nitric acid solution; and adding the dilute nitric acid solution to the obtained yttrium phosphate slurry to stabilize the slurry pH at 3-4.

[0014] Preferably, the first yttrium ion dispersion treatment includes dissolving yttrium nitrate hexahydrate in deionized water to form a first yttrium ion dispersion; and adding the first yttrium ion dispersion dropwise to the acid-pre-conditioned slurry, and stirring for 20-40 minutes after the addition is completed.

[0015] Preferably, the phytic acid dilution treatment includes diluting an aqueous phytic acid solution with deionized water to form a phytic acid dilution; and adding the phytic acid dilution dropwise to the slurry treated with the first yttrium ion dispersion, and continuing to stir for 20-40 minutes after the addition is completed.

[0016] Preferably, the concentration of the phytic acid aqueous solution is 50%.

[0017] Preferably, the second yttrium ion dispersion treatment includes dissolving yttrium nitrate hexahydrate in deionized water to form a second yttrium ion dispersion; and adding the second yttrium ion dispersion to the slurry treated with phytic acid dilution solution, and continuing to stir for 20-40 minutes after the addition is completed.

[0018] Preferably, the ammonia gas phase fixation includes introducing a mixture of ammonia and nitrogen into the slurry treated with the second yttrium ion dispersion to slowly raise the pH of the slurry to 5-6; after stopping the gas flow, the slurry is allowed to stand and age at 40-50°C for 1.5-2.5 hours.

[0019] Preferably, the ammonia molar fraction in the ammonia-nitrogen mixture is 2%-4%.

[0020] Preferably, the spray granulation includes adding polyvinyl alcohol 1788 to deionized water to obtain a polyvinyl alcohol aqueous solution; adding the polyvinyl alcohol aqueous solution to the slurry after standing and aging, continuing to stir for 20-40 minutes, and then performing spray granulation.

[0021] Preferably, the inlet temperature of the spray granulation is 165-175℃, the outlet temperature is 80-90℃, the atomization pressure is 250-350kPa, and the resulting granulated powder retains a particle size fraction of 20-60μm after sieving.

[0022] Preferably, the calcination includes placing the soft agglomerated powder obtained by spray granulation in an alumina crucible, heating it to 280-320°C at 1°C / min and holding it at that temperature for 1 hour in an air atmosphere furnace, then heating it to 630-670°C at 2°C / min and holding it at that temperature for 1.5-2.5 hours, and then cooling it with the furnace to obtain pretreated yttrium phosphate powder.

[0023] Preferably, the pressing, sintering, and hot isostatic pressing densification include: Take pretreated yttrium phosphate powder, grind it into powder and pass it through a 100-mesh sieve; place the sieved pretreated yttrium phosphate powder in a mold and press it unidirectionally at 70-90 mPa for 50-70 seconds. After demolding, put the circular blank into a rubber sleeve and cold isostatically press it at 200-240 mPa for 4-6 minutes to obtain yttrium phosphate ceramic target blank. The yttrium phosphate ceramic target blank is placed on an alumina sintering plate, and high-purity yttrium phosphate powder of the same specification is placed around the blank as a non-contact sintering powder, with the sintering powder maintaining a distance of more than 5 mm from the blank; the temperature is increased to 590-610℃ at 1℃ / min in an air atmosphere and held for 1 hour, then increased to 1430-1470℃ at 3℃ / min and held for 2 hours, then increased to 1500-1540℃ at 2℃ / min and held for 3-5 hours, and then cooled with the furnace; The sintered body is densified by hot isostatic pressing (HIP), with an argon atmosphere, a temperature of 1430-1470℃, a pressure of 150-170mPa, and a holding time of 1.5-2.5h. Finally, high-purity yttrium phosphate ceramic targets are obtained by external cylindrical grinding, double-sided grinding, and polishing.

[0024] Furthermore, the present invention also provides a method for preparing a piezoelectric single crystal thin film based on yttrium phosphate, wherein the high-purity yttrium phosphate ceramic target is loaded into an RF magnetron sputtering cavity, pre-sputtered with an argon-oxygen mixed gas in a baffle-closed state, followed by sputtering deposition, and after deposition is completed, annealing is performed to obtain a piezoelectric single crystal thin film based on yttrium phosphate.

[0025] Preferably, the sputtering deposition includes evacuating the sputtering chamber to a background vacuum of no more than 5 × 10⁻⁶. -4 The substrate temperature is raised to 650-680℃, and the working pressure is controlled at 0.6-0.8Pa. The first stage of RF power is 90-110W, and the deposition time is 8-12min, forming a micro-phosphorus-rich nucleation layer with a thickness of 60-80nm. The second stage of deposition time is 35-45min, the RF power is linearly increased from 100-110W to 180W, and the argon to oxygen ratio is linearly transitioned from 4:1 to 9:1, forming a transition layer with a thickness of 400-500nm. The third stage of RF power is maintained at 180W, the argon to oxygen ratio is maintained at 9:1, and the deposition time is 200-220min, forming a yttrium phosphate piezoelectric single crystal thin film with a total thickness of 2.8-3.2μm.

[0026] Preferably, the annealing process is carried out in an oxygen atmosphere at 700-740°C for 20-40 minutes.

[0027] Furthermore, the present invention also provides a piezoelectric inkjet head based on a yttrium phosphate piezoelectric single crystal thin film, the piezoelectric inkjet head comprising a silicon-based piezoelectric drive sheet, an ink cavity layer, and a nozzle plate; The silicon-based piezoelectric drive chip includes a monocrystalline silicon substrate, a silicon dioxide insulating layer disposed on the surface of the monocrystalline silicon substrate, a titanium adhesion layer disposed on the surface of the silicon dioxide insulating layer, a platinum lower electrode disposed on the surface of the titanium adhesion layer, a yttrium phosphate piezoelectric single crystal thin film material disposed on the surface of the platinum lower electrode, and a patterned platinum upper electrode disposed on the surface of the yttrium phosphate piezoelectric single crystal thin film material.

[0028] Preferably, the thickness of the silicon dioxide insulating layer is 1 μm, the thickness of the titanium adhesion layer is 20 nm, the thickness of the platinum lower electrode is 180 nm, and the thickness of the patterned platinum upper electrode is 220 nm.

[0029] Preferably, the nozzle plate is provided with nozzles with a diameter of 15μm; the ink cavity layer is provided with an ink cavity and an ink inlet channel, and the volume of the ink cavity is set according to the requirement of 1pL ink droplet ejection.

[0030] Furthermore, the present invention also provides a method for preparing a piezoelectric inkjet head based on a yttrium phosphate piezoelectric single crystal thin film, comprising the following steps: (1) Preparation of high-purity yttrium phosphate ceramic target; (2) A silicon dioxide insulating layer, a titanium adhesion layer and a platinum lower electrode are prepared on the surface of a single crystal silicon substrate to obtain a silicon wafer with a platinum lower electrode; (3) Using the high-purity yttrium phosphate ceramic target as the radio frequency sputtering target, deposit and anneal the yttrium phosphate piezoelectric single crystal thin film material on the surface of the silicon wafer with the platinum lower electrode; (4) Fabrication of patterned driving electrode: A patterned platinum top electrode is formed on the surface of the yttrium phosphate piezoelectric single crystal thin film to obtain a piezoelectric driving sheet; (5) Prepare inkjet structure and package: Prepare a nozzle plate with nozzles, form an ink cavity and an ink inlet channel on the back of the piezoelectric drive sheet, and then align and package the nozzle plate with the piezoelectric drive sheet that forms the ink cavity and ink inlet channel to obtain a piezoelectric inkjet head based on yttrium phosphate piezoelectric single crystal thin film.

[0031] Preferably, the formation of the patterned platinum upper electrode includes: spin-coating AZ5214E ​​image reversal photoresist onto the surface of the yttrium piezoelectric single crystal thin film, pre-baking at a temperature of 95°C for 90 seconds, and forming an upper electrode pattern window after exposure and development with AZ300MIF developer; depositing a 220nm platinum upper electrode using DC magnetron sputtering, followed by removing excess metal and photoresist using a stripping process to obtain the patterned driving electrode.

[0032] Preferably, the inkjet structure and encapsulation includes: taking a single-crystal silicon wafer as the nozzle plate substrate, forming nozzle patterns by photolithography, and then processing nozzles with a diameter of 15μm using a deep silicon etching process; forming an ink cavity and ink inlet channel on the back of the piezoelectric drive sheet using a deep silicon etching process, with the ink cavity volume designed according to the 1pL ink droplet ejection requirement; finally, aligning and encapsulating the nozzle plate and ink cavity layer using oxygen plasma surface activation and 300℃ low-temperature direct bonding to obtain a piezoelectric inkjet head based on a yttrium phosphate piezoelectric single-crystal thin film.

[0033] Preferably, the deep silicon etching process uses alternating introduction of sulfur hexafluoride and octafluorocyclobutane for etching.

[0034] The beneficial effects of this invention are: This invention sequentially performs low-dose yttrium ion pre-anchoring, phytic acid dilution treatment, high-concentration yttrium ion short-term outer layer bridging, and ammonia gas phase fixation on high-purity yttrium phosphate powder. This allows yttrium hexahydrate, phytic acid aqueous solution, and ammonia-nitrogen mixture to act on the powder surface in a time sequence, which is beneficial for forming stable inorganic phosphate microregions at particle contact sites and reducing local pore closure and target surface metering fluctuations during subsequent sintering.

[0035] This invention produces a high-purity yttrium phosphate ceramic target by subjecting surface-treated yttrium phosphate slurry to polyvinyl alcohol 1788-assisted spray granulation, pyrolysis pretreatment, unidirectional pressing, cold isostatic pressing, sintering, and hot isostatic pressing densification. This process helps improve the pore closure path and sintering uniformity of the target material, and reduces the risk of particle splashing and yttrium phosphate ratio drift during sputtering.

[0036] This invention uses gradient deposition to gradually transition the yttrium phosphate piezoelectric film from the interface to the substrate layer, which helps to mitigate abrupt changes at the film-substrate interface, improves the film adhesion reliability and the stability of the piezoelectric response after high-frequency driving, and is therefore suitable for piezoelectric inkjet heads with small ink droplets and high-frequency jetting. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0038] Raw material source and model parameters High-purity yttrium phosphate powder: 99.99% purity, D50 of 150-300nm (submicron or nanoscale); phytic acid aqueous solution: 50% by mass; polyvinyl alcohol: type 1788, degree of alcoholysis 87-89%; nitric acid: 65% by mass; monocrystalline silicon wafer: 4-inch P-type boron-doped wafer. <100> Single-crystal silicon wafer, 100mm in diameter and 525μm in thickness; titanium and platinum targets: high-purity metal sputtering targets with a purity of not less than 99.99%; photoresist: AZ5214E ​​image reversal photoresist; developer: AZ300MIF developer.

[0039] Example 1: A method for preparing a piezoelectric single-crystal thin film and a piezoelectric inkjet head based on yttrium phosphate, the specific steps of which are as follows: S1 yttrium phosphate powder pre-dispersion: Weigh 250g of high-purity yttrium phosphate powder and dry it at 120℃ for 2 hours to remove physically adsorbed water. Add the dried 250g of high-purity yttrium phosphate powder to a mixed dispersion medium consisting of 300g of deionized water and 300g of anhydrous ethanol, then add 750g of high-purity zirconia grinding balls, place the mixture in a polytetrafluoroethylene ball mill jar, and ball mill at 200r / min for 4 hours to obtain yttrium phosphate slurry. After ball milling, filter the slurry through a 200-mesh nylon sieve to remove occasional hard agglomerates. S2 slurry acid preconditioning: 1g of nitric acid was slowly added to 12g of deionized water to prepare 13g of dilute nitric acid solution; all 13g of dilute nitric acid solution was added to the yttrium phosphate slurry obtained in S1, and stirred at 400r / min for 20min at 25℃ to stabilize the pH of the slurry at 3-4. S3 first yttrium ion dispersion treatment: 1g of yttrium nitrate hexahydrate was dissolved in deionized water to obtain 50g of the first yttrium ion dispersion; 50g of the first yttrium ion dispersion was added dropwise to the slurry obtained in S2 at a rate of 1g / min, and the addition was carried out at 25℃ and 400r / min. After the addition was completed, the stirring was continued for 30min. Treatment with S4 phytic acid dilution: Dilute 2g of phytic acid aqueous solution with deionized water to obtain 20g of phytic acid diluted solution; add 20g of phytic acid diluted solution dropwise to the slurry obtained in S3 within 10min, and continue stirring for 30min after the addition is completed, keeping the stirring temperature at 25℃. S5 second yttrium ion dispersion treatment: 2g of yttrium nitrate hexahydrate was dissolved in deionized water to obtain 20g of second yttrium ion dispersion; 20g of second yttrium ion dispersion was added to the slurry obtained in S4 within 4min, and then stirring was continued for only 6min. S6 ammonia gas phase stationary: The slurry obtained from S5 was transferred to a sealed stirring container equipped with a gas inlet, a mechanical stirring paddle, and a tail gas absorption bottle. It was stirred at 300 r / min at 25°C while 30 g of an ammonia-nitrogen mixture was introduced. The ammonia molar fraction in the ammonia-nitrogen mixture was 3%, and the nitrogen was used as a balance gas. The aeration time was controlled at 30 min to allow the pH of the slurry to slowly rise to 5-6. After the aeration was stopped, the mixture was allowed to stand and age at 45°C for 2 h. The tail gas was then treated in a dilute sulfuric acid absorption bottle. S7 spray granulation forms soft agglomerated powder: 1g of polyvinyl alcohol 1788 was added to deionized water and stirred at 95℃ until completely dissolved. After cooling to 40℃, 20g of polyvinyl alcohol aqueous solution was obtained. The 20g polyvinyl alcohol aqueous solution was added to the slurry aged by S6 and stirred for 30min. Then, spray granulation was performed. The inlet temperature of spray granulation was 170℃, the outlet temperature was 85℃, and the atomization pressure was 300kPa. The resulting granulated powder was sieved and retained a particle size fraction of 20-60μm. S8 calcination: All the soft agglomerate powder obtained from S7 was collected. 255g of soft agglomerate powder was placed in an alumina crucible and heated to 300℃ at 1℃ / min in an air atmosphere furnace and held for 1h. Then the temperature was increased to 650℃ at 2℃ / min and held for 2h. The powder was then cooled with the furnace to obtain pretreated yttrium phosphate powder. S9 ceramic target blank forming: Take 230g of pretreated yttrium phosphate powder obtained from S8, lightly grind it, and pass it through a 100-mesh sieve. Place the sieved 230g of pretreated yttrium phosphate powder into a circular mold with an inner diameter of 115mm, and press it unidirectionally at 80mPa for 60s. After demolding, place the circular blank into a rubber sleeve and cold isostatically press it at 220mPa for 5min to obtain a yttrium phosphate ceramic target blank. Place the obtained yttrium phosphate ceramic target blank on an alumina sintering plate, and place 120g of high-purity yttrium phosphate powder of the same specification around the blank as a non-contact sintering powder. The sintered powder is kept at a distance of more than 5 mm from the green body; the temperature is increased to 600℃ at 1℃ / min and held for 1 hour in an air atmosphere, then increased to 1450℃ at 3℃ / min and held for 2 hours, then increased to 1520℃ at 2℃ / min and held for 4 hours, and then cooled in the furnace; the sintered body is then densified by hot isostatic pressing in an argon atmosphere at a temperature of 1450℃ and a pressure of 160mPa for 2 hours; finally, the high-purity yttrium phosphate ceramic target is obtained by external cylindrical grinding, double-sided grinding and polishing. S10 pre-sputtering treatment: The high-purity yttrium phosphate ceramic target obtained from S9 was loaded into the radio frequency magnetron sputtering cavity and pre-sputtered with an argon-oxygen mixture for 20 minutes with the baffle closed. Fabrication of S11 silicon substrate and lower electrode: One monocrystalline silicon wafer was used as the substrate. A first cleaning solution was prepared using 400g deionized water, 80g hydrogen peroxide solution, and 80g ammonia. The wafer was cleaned at 75°C for 10 minutes. A second cleaning solution was then prepared using 400g deionized water, 80g hydrogen peroxide solution, and 80g hydrochloric acid. The wafer was cleaned at 75°C for 10 minutes. After cleaning, the wafer was rinsed with deionized water and dried. Subsequently, 9g of oxygen was introduced into a thermal oxidation furnace, and the wafer was thermally oxidized at 1000°C for 60 minutes to form a 1μm thick silicon dioxide insulating layer. Then, a 20nm titanium adhesion layer and a 180nm platinum lower electrode were sequentially deposited on the silicon wafer surface using DC magnetron sputtering. The purity of both the titanium and platinum targets used for deposition was not less than 99.99%. After deposition, the wafer was annealed at 650°C for 30 minutes. Preparation of S12 piezoelectric single crystal thin film: The high-purity yttrium phosphate ceramic target obtained from S10 was used as the RF sputtering target, and the silicon wafer with a platinum bottom electrode obtained from S12 was used as the substrate; the sputtering cavity was evacuated to a background vacuum of no more than 5 × 10⁻⁶. -4The substrate temperature was raised to 660℃, and the working pressure was controlled at 800mPa. The first stage involved a 100W RF power deposition time of 10min, forming a 70nm thick micro-phosphorus-rich nucleation layer. The second stage was a linear transition layer deposition time of 40min, with the RF power linearly increasing from 100W to 180W and the argon-to-oxygen ratio linearly transitioning from 4:1 to 9:1, forming a 450nm thick transition layer. The third stage maintained a 180W RF power deposition time of 210min, with the argon-to-oxygen ratio maintained at 9:1, forming a 3μm thick piezoelectric film. After deposition, the film was annealed at 720℃ for 30min in an oxygen atmosphere. Fabrication of the upper electrode and piezoelectric driving pattern of S13: 3g of AZ5214E ​​image reversal photoresist was spin-coated onto the surface of the YPO4 piezoelectric thin film obtained in S12. The pre-baking temperature was 95℃ and the pre-baking time was 90s. After exposure and development with 20g of AZ300MIF developer, the upper electrode pattern window was formed. A 220nm platinum upper electrode was deposited by DC magnetron sputtering, and the purity of the platinum target used for deposition was not less than 99.99%. Subsequently, a conventional stripping process was used to remove excess metal and photoresist to obtain the patterned driving electrode. S14 ink chamber, ink inlet channel, nozzle plate and packaging: Another single-crystal silicon wafer was used as the nozzle plate substrate. 3g of AZ5214E ​​image reversal photoresist was spin-coated and developed with 20g of AZ300MIF developer to form the nozzle pattern. The nozzle with a diameter of 15μm was processed using conventional deep silicon etching process. The etching gas was alternately introduced with sulfur hexafluoride and octafluorocyclobutane, with a cumulative amount of 20g of sulfur hexafluoride and 15g of octafluorocyclobutane. The ink cavity and ink inlet channel were formed on the back of the piezoelectric drive wafer obtained in S13 using the same deep silicon etching method. The ink cavity volume was designed according to the requirement of 1pL ink droplet ejection. Finally, oxygen plasma surface activation and 300℃ low-temperature direct bonding were used to align and encapsulate the nozzle plate and the ink cavity layer to obtain a piezoelectric inkjet head based on a piezoelectric single-crystal thin film.

[0040] Example 2: A method for preparing a piezoelectric single-crystal thin film and a piezoelectric inkjet head based on yttrium phosphate, the specific steps of which are as follows: S1 yttrium phosphate powder pre-dispersion: Weigh 240g of high-purity yttrium phosphate powder and dry it at 110℃ for 2 hours to remove physically adsorbed water. Add the dried high-purity yttrium phosphate powder to a mixed dispersion medium consisting of 280g of deionized water and 280g of anhydrous ethanol, then add 720g of high-purity zirconia grinding balls, place the mixture in a polytetrafluoroethylene ball mill jar, and ball mill at 180r / min for 3 hours to obtain yttrium phosphate slurry. After ball milling, filter the slurry through a 200-mesh nylon sieve to remove occasional hard agglomerates. S2 slurry acid preconditioning: 1g of nitric acid was slowly added to 12g of deionized water to prepare a dilute nitric acid solution; the entire dilute nitric acid solution was added to the yttrium phosphate slurry obtained in S1, and stirred at 350r / min for 15min at 25℃ to stabilize the pH of the slurry at 3-4. S3 first yttrium ion dispersion treatment: 0.8 g of yttrium nitrate hexahydrate was dissolved in deionized water to obtain 50 g of yttrium ion dispersion. 50 g of yttrium ion dispersion was added dropwise to the slurry obtained in S2 at a rate of 0.8 g / min. During the addition, stirring was maintained at 25 °C and 350 r / min. After the addition was completed, stirring was continued for 20 min. Treatment with S4 phytic acid dilution: 1.5g of phytic acid aqueous solution was diluted with deionized water to obtain 20g of phytic acid diluted solution; the 20g of phytic acid diluted solution was added dropwise to the slurry obtained in S3 within 8min, and stirring was continued for 20min after the addition was completed, while the stirring temperature was maintained at 25℃. S5 second yttrium ion dispersion treatment: 1.8g of yttrium nitrate hexahydrate was dissolved in deionized water to obtain 20g of second yttrium ion dispersion; 20g of second yttrium ion dispersion was added to the slurry obtained in S4 within 3min, and then stirring was continued for only 5min. S6 ammonia gas phase stationary: The slurry obtained from S5 was transferred to a sealed stirring container equipped with a gas inlet, a mechanical stirring paddle, and a tail gas absorption bottle. It was stirred at 250 r / min at 25°C while 25 g of an ammonia-nitrogen mixture was introduced. The ammonia molar fraction in the ammonia-nitrogen mixture was 2%, and the nitrogen was used as a balance gas. The aeration time was controlled at 20 min to allow the pH of the slurry to slowly rise to 5-6. After the aeration was stopped, the slurry was allowed to stand and age at 40°C for 1.5 h. The tail gas was then treated in a dilute sulfuric acid absorption bottle. S7 spray granulation forms soft agglomerated powder: 0.8g of polyvinyl alcohol 1788 was added to deionized water and stirred at 90℃ until completely dissolved. After cooling to 35℃, 20g of polyvinyl alcohol aqueous solution was obtained. The 20g polyvinyl alcohol aqueous solution was added to the slurry aged by S6 and stirred for 20min. Then, spray granulation was performed. The inlet temperature of spray granulation was 165℃, the outlet temperature was 80℃, and the atomization pressure was 250kPa. The resulting granulated powder was sieved and retained a particle size fraction of 20-60μm. S8 calcination: All the soft agglomerate powder obtained from S7 was collected. 245g of the soft agglomerate powder was placed in an alumina crucible and heated to 280℃ at 1℃ / min in an air atmosphere furnace and held for 1h. Then the temperature was increased to 630℃ at 2℃ / min and held for 1.5h. The powder was then cooled with the furnace to obtain pretreated yttrium phosphate powder. S9 ceramic target blank forming: Take 220g of pretreated yttrium phosphate powder obtained from S8, lightly grind it, and pass it through a 100-mesh sieve. Place the sieved pretreated yttrium phosphate powder into a circular mold with an inner diameter of 112mm, and press it unidirectionally at 70mPa for 50s. After demolding, place the circular blank into a rubber sleeve and cold isostatically press it at 200mPa for 4min to obtain a yttrium phosphate ceramic target blank. Place the obtained yttrium phosphate ceramic target blank on an alumina sintering plate, and place 100g of high-purity yttrium phosphate powder of the same specification around the blank as a non-contact sintering powder. Maintain a distance of more than 5 mm from the blank; heat to 590℃ at 1℃ / min and hold for 1 hour in air atmosphere, then heat to 1430℃ at 3℃ / min and hold for 2 hours, then heat to 1500℃ at 2℃ / min and hold for 3 hours, and then cool with the furnace; perform hot isostatic pressing (HIP) densification on the sintered body in an argon atmosphere at 1430℃ and 150 MPa for 1.5 hours; finally, obtain a high-purity yttrium phosphate ceramic target by external cylindrical grinding, double-sided grinding and polishing. S10 pre-sputtering treatment: The high-purity yttrium phosphate ceramic target obtained from S9 was loaded into the radio frequency magnetron sputtering cavity and pre-sputtered with an argon-oxygen mixture for 15 min with the baffle closed. Fabrication of S11 silicon substrate and lower electrode: A single-crystal silicon wafer was used as the substrate. A first cleaning solution was prepared using 400g deionized water, 80g hydrogen peroxide solution, and 80g ammonia. The wafer was cleaned at 75°C for 10 minutes. A second cleaning solution was then prepared using the same 400g deionized water, 80g hydrogen peroxide solution, and 80g hydrochloric acid. The wafer was cleaned at 75°C for 10 minutes. After cleaning, the wafer was rinsed with deionized water and dried. Subsequently, 9g of oxygen was introduced into a thermal oxidation furnace, and the wafer was thermally oxidized at 1000°C for 60 minutes to form a 1μm thick silicon dioxide insulating layer. Then, a 20nm titanium adhesion layer and a 180nm platinum lower electrode were sequentially deposited on the silicon wafer surface using DC magnetron sputtering. After deposition, the wafer was annealed at 650°C for 30 minutes. Preparation of S12 piezoelectric single crystal thin film: The high-purity yttrium phosphate ceramic target obtained from S10 was used as the RF sputtering target, and the silicon wafer with a platinum bottom electrode obtained from S12 was used as the substrate; the sputtering cavity was evacuated to a background vacuum of no more than 5 × 10⁻⁶. -4The substrate temperature was raised to 650℃, and the working pressure was controlled at 600mPa. The first stage involved a radio frequency (RF) power of 90W and a deposition time of 8 minutes, forming a 60nm thick micro-phosphorus-rich nucleation layer. The second stage involved a deposition time of 35 minutes, with the RF power linearly increasing from 100W to 180W and the argon-to-oxygen ratio linearly transitioning from 4:1 to 9:1, forming a 400nm thick transition layer. The third stage maintained a RF power of 180W, with the argon-to-oxygen ratio maintained at 9:1, and a deposition time of 200 minutes, forming a piezoelectric film with a total thickness of 2.8μm. After deposition, the film was annealed at 700℃ for 20 minutes in an oxygen atmosphere. Fabrication of the upper electrode and piezoelectric driving pattern in S13: 3g of AZ5214E ​​image reversal photoresist was spin-coated onto the surface of the piezoelectric thin film obtained in S12. The pre-baking temperature was 95℃ and the pre-baking time was 90s. After exposure and development with 20g of AZ300MIF developer, the upper electrode pattern window was formed. A 220nm platinum upper electrode was deposited by DC magnetron sputtering, and the purity of the platinum target used for deposition was not less than 99.99%. Subsequently, excess metal and photoresist were removed by conventional stripping process to obtain the patterned driving electrode. S14 ink chamber, ink inlet channel, nozzle plate and packaging: Another single-crystal silicon wafer was used as the nozzle plate substrate. 3g of AZ5214E ​​image reversal photoresist was spin-coated and developed with 20g of AZ300MIF developer to form the nozzle pattern. The nozzle with a diameter of 15μm was processed using conventional deep silicon etching process. The etching gas was alternately introduced with sulfur hexafluoride and octafluorocyclobutane, with a cumulative amount of 20g of sulfur hexafluoride and 15g of octafluorocyclobutane. The ink cavity and ink inlet channel were formed on the back of the piezoelectric drive wafer obtained in S13 using the same deep silicon etching method. The ink cavity volume was designed according to the requirement of 1pL ink droplet ejection. Finally, oxygen plasma surface activation and 300℃ low-temperature direct bonding were used to align and encapsulate the nozzle plate and the ink cavity layer to obtain a piezoelectric inkjet head based on a piezoelectric single-crystal thin film.

[0041] Example 3: A method for preparing a piezoelectric single-crystal thin film and a piezoelectric inkjet head based on yttrium phosphate, the specific steps of which are as follows: S1 yttrium phosphate powder pre-dispersion: Weigh 260g of high-purity yttrium phosphate powder and dry it at 130℃ for 2 hours to remove physically adsorbed water. Add the dried high-purity yttrium phosphate powder to a mixed dispersion medium consisting of 320g of deionized water and 320g of anhydrous ethanol, then add 780g of high-purity zirconia grinding balls, place the mixture in a polytetrafluoroethylene ball mill jar, and ball mill at 220r / min for 5 hours to obtain yttrium phosphate slurry. After ball milling, filter the slurry through a 200-mesh nylon sieve to remove occasional hard agglomerates. S2 slurry acid preconditioning: 2g of nitric acid was slowly added to 18g of deionized water to prepare a dilute nitric acid solution; the entire dilute nitric acid solution was added to the yttrium phosphate slurry obtained in S1, and stirred at 450r / min for 25min at 25℃ to stabilize the pH of the slurry at 3-4. S3 first yttrium ion dispersion treatment: 1.2 g of yttrium nitrate hexahydrate was dissolved in deionized water to obtain 50 g of the first yttrium ion dispersion; 50 g of the first yttrium ion dispersion was added dropwise to the slurry obtained in S2 at a rate of 1.2 g / min, while maintaining stirring at 25 °C and 450 r / min during the addition, and stirring was continued for 40 min after the addition was completed; Treatment with S4 phytic acid dilution: Dilute 2.5g of phytic acid aqueous solution with deionized water to obtain 20g of phytic acid diluted solution; add 20g of phytic acid diluted solution dropwise to the slurry obtained in S3 within 12min, and continue stirring for 40min after the addition is completed, while maintaining the stirring temperature at 25℃. S5 second yttrium ion dispersion treatment: 2.2g of yttrium nitrate hexahydrate was dissolved in deionized water to obtain 20g of second yttrium ion dispersion; 20g of second yttrium ion dispersion was added to the slurry obtained in S4 within 5min, and then stirring was continued for only 8min. S6 ammonia gas phase stationary: The slurry obtained from S5 was transferred to a sealed stirring container equipped with a gas inlet, a mechanical stirring paddle, and a tail gas absorption bottle. It was stirred at 350 r / min at 25°C while 35 g of an ammonia-nitrogen mixture was introduced. The ammonia molar fraction in the ammonia-nitrogen mixture was 4%, and the nitrogen was used as a balance gas. The aeration time was controlled at 40 min to allow the pH of the slurry to slowly rise to 5-6. After the aeration was stopped, the slurry was allowed to stand and age at 50°C for 2.5 h. The tail gas was then treated in a dilute sulfuric acid absorption bottle. S7 spray granulation forms soft agglomerated powder: 1.2g of polyvinyl alcohol 1788 was added to deionized water and stirred at 98℃ until completely dissolved. After cooling to 45℃, 20g of polyvinyl alcohol aqueous solution was obtained. The 20g polyvinyl alcohol aqueous solution was added to the slurry aged by S6 and stirred for 40min. Then, spray granulation was performed. The inlet temperature of spray granulation was 175℃, the outlet temperature was 90℃, and the atomization pressure was 350kPa. The resulting granulated powder was sieved and retained a particle size fraction of 20-60μm. S8 calcination: All the soft agglomerate powder obtained from S7 was collected. 265g of the soft agglomerate powder was placed in an alumina crucible and heated to 320℃ at 1℃ / min in an air atmosphere furnace and held for 1h. Then the temperature was increased to 670℃ at 2℃ / min and held for 2.5h. The powder was then cooled with the furnace to obtain pretreated yttrium phosphate powder. S9 ceramic target blank forming: Take 240g of pretreated yttrium phosphate powder obtained from S8, gently grind it, and pass it through a 100-mesh sieve. Place the sieved pretreated yttrium phosphate powder into a circular mold with an inner diameter of 118mm, and press it unidirectionally at 90mPa for 70s. After demolding, place the circular blank into a rubber sleeve and cold isostatically press it at 240mPa for 6min to obtain a yttrium phosphate ceramic target blank. Place the obtained yttrium phosphate ceramic target blank on an alumina sintering plate, and place 140g of high-purity yttrium phosphate powder of the same specification around the blank as a non-contact sintering powder. Maintain a distance of more than 5 mm from the blank; heat to 610℃ at 1℃ / min and hold for 1 h in air atmosphere, then heat to 1470℃ at 3℃ / min and hold for 2 h, then heat to 1540℃ at 2℃ / min and hold for 5 h, then cool with the furnace; perform hot isostatic pressing (HIP) densification on the sintered body in an argon atmosphere at 1470℃ and 170 mPa for 2.5 h; finally, obtain a high-purity yttrium phosphate ceramic target by external cylindrical grinding, double-sided grinding and polishing. S10 pre-sputtering treatment: The high-purity yttrium phosphate ceramic target obtained from S9 was loaded into the radio frequency magnetron sputtering cavity and pre-sputtered with an argon-oxygen mixture for 25 min with the baffle closed. Fabrication of S11 silicon substrate and lower electrode: A single-crystal silicon wafer was used as the substrate. A first cleaning solution was prepared using 400g deionized water, 80g hydrogen peroxide solution, and 80g ammonia. The wafer was cleaned at 75°C for 10 minutes. A second cleaning solution was then prepared using the same 400g deionized water, 80g hydrogen peroxide solution, and 80g hydrochloric acid. The wafer was cleaned at 75°C for 10 minutes. After cleaning, the wafer was rinsed with deionized water and dried. Subsequently, 9g of oxygen was introduced into a thermal oxidation furnace, and the wafer was thermally oxidized at 1000°C for 60 minutes to form a 1μm thick silicon dioxide insulating layer. Then, a 20nm titanium adhesion layer and a 180nm platinum lower electrode were sequentially deposited on the silicon wafer surface using DC magnetron sputtering. After deposition, the wafer was annealed at 650°C for 30 minutes. Preparation of S12 piezoelectric single crystal thin film: The high-purity yttrium phosphate ceramic target obtained from S10 was used as the RF sputtering target, and the silicon wafer with a platinum bottom electrode obtained from S11 was used as the substrate; the sputtering cavity was evacuated to a background vacuum of no more than 5 × 10⁻⁶. -4The substrate temperature was raised to 680℃, and the working pressure was controlled at 800mPa. The first stage involved a radio frequency (RF) power of 110W and a deposition time of 12min, forming a micro-phosphorus-rich nucleation layer with a thickness of 80nm. The second stage involved a deposition time of 45min, with the RF power linearly increasing from 110W to 180W and the argon-to-oxygen ratio linearly transitioning from 4:1 to 9:1, forming a transition layer with a thickness of 500nm. The third stage maintained a RF power of 180W, with the argon-to-oxygen ratio maintained at 9:1, and a deposition time of 220min, forming a piezoelectric film with a total thickness of 3.2μm. After deposition, the film was annealed at 740℃ for 40min in an oxygen atmosphere. Fabrication of the upper electrode and piezoelectric driving pattern in S13: 3g of AZ5214E ​​image reversal photoresist was spin-coated onto the surface of the piezoelectric thin film obtained in S12. The pre-baking temperature was 95℃ and the pre-baking time was 90s. After exposure and development with 20g of AZ300MIF developer, the upper electrode pattern window was formed. A 220nm platinum upper electrode was deposited by DC magnetron sputtering, and the purity of the platinum target used for deposition was not less than 99.99%. Subsequently, excess metal and photoresist were removed by conventional stripping process to obtain the patterned driving electrode. S14 ink chamber, ink inlet channel, nozzle plate and packaging: Another single-crystal silicon wafer was used as the nozzle plate substrate. 3g of AZ5214E ​​image reversal photoresist was spin-coated and developed with 20g of AZ300MIF developer to form the nozzle pattern. The nozzle with a diameter of 15μm was processed using conventional deep silicon etching process. The etching gas was alternately introduced with sulfur hexafluoride and octafluorocyclobutane, with a cumulative amount of 20g of sulfur hexafluoride and 15g of octafluorocyclobutane. The ink cavity and ink inlet channel were formed on the back of the piezoelectric drive wafer obtained in S13 using the same deep silicon etching method. The ink cavity volume was designed according to the requirement of 1pL ink droplet ejection. Finally, oxygen plasma surface activation and 300℃ low-temperature direct bonding were used to align and encapsulate the nozzle plate and the ink cavity layer to obtain a piezoelectric inkjet head based on a piezoelectric single-crystal thin film.

[0042] Comparative Example 1: The difference from Example 1 is that the powder surface site control in S3 to S6 is not performed; after the acidity pre-conditioning of the slurry is completed in S2, 95g of deionized water is directly added to the slurry, and then polyvinyl alcohol aqueous solution is added according to S7 of Example 1 and spray granulation is performed; the remaining conditions are the same as in Example 1.

[0043] Comparative Example 2: The difference from Example 1 is that the 50g of the first yttrium ion dispersion in S3 is not added dropwise before the addition of the phytic acid aqueous solution, but after the 20g of the second yttrium ion dispersion in S5 is added and stirred for 6 minutes, the 50g of the first yttrium ion dispersion is added dropwise at a rate of 1g / min and stirred for 30 minutes, and then S6 is carried out; the other conditions are the same as in Example 1.

[0044] Comparative Example 3: The difference from Example 1 is that the yttrium ions are not introduced in two stages, S3 and S5. Instead, 3g of yttrium nitrate hexahydrate is dissolved in deionized water all at once. In S3, it is added dropwise to the slurry obtained in S2 at a rate of 1g / min. After the addition is completed, stirring is continued for 30min. Phytic acid diluent is added in S4. No second yttrium ion dispersion is added in S5. The other conditions are the same as in Example 1.

[0045] Comparative Example 4: The difference from Example 1 is that in S4, instead of adding phytic acid aqueous solution, an equal amount of deionized water is added and added dropwise to the slurry obtained in S3 within 10 minutes. After the addition is completed, stirring is continued for 30 minutes. The other conditions are the same as in Example 1.

[0046] Comparative Example 5: The difference from Example 1 is that in S6, instead of introducing 30g of ammonia-nitrogen mixed gas, 2g of ammonia water is added to 28g of deionized water to obtain 30g of alkaline conditioning solution, which is then added to the slurry obtained in S5 in one go within 1 minute. Subsequently, it is stirred at 300r / min at 25°C for 30 minutes, and then allowed to stand and age at 45°C for 2 hours; the other conditions are the same as in Example 1.

[0047] Comparative Example 6: The difference from Example 1 is that S12 adopts a one-step constant deposition method; specifically, the substrate temperature is raised to 660°C, the working pressure is controlled at 800mPa, the radio frequency power is maintained at 180W, the ratio of argon to oxygen is maintained at 9:1, the deposition time is 260min, and a yttrium phosphate piezoelectric film with a total thickness of about 3μm is formed. After deposition, it is annealed at 720°C for 30min in an oxygen atmosphere.

[0048] Test sample preparation: Density test: The relative density of the ceramic target was tested according to GB / T 25995-2010 "Test Method for Density and Apparent Porosity of Fine Ceramics" using the Archimedes method. Three samples were taken for each group and the average value was taken. Piezoelectric strain constant test: The longitudinal piezoelectric strain constant d33 was tested according to GB / T 11309-1989 "Test Methods for Performance of Piezoelectric Ceramic Materials - Quasi-static Test of Longitudinal Piezoelectric Strain Constant d33". During the test, a piezoelectric thin film sample after the upper electrode was formed in S13 was taken and placed in an environment of 25℃ and 50% relative humidity for 24 hours. The upper and lower electrodes were then connected to a quasi-static d33 tester. The loading frequency was 110Hz, and the test force was 0.25N. Five electrode units were tested for each sample, and three films were taken from each group of samples, and the average value was calculated. Film substrate adhesion reliability test: The pull-off adhesion test was conducted according to GB / T 5210-2006 "Paints and Varnishes Pull-off Adhesion Test". The film sample obtained in S13 was taken, and a pull-off test column with a diameter of 5 mm was bonded to the film surface. After curing at room temperature for 24 h, the pull-off test was carried out at a loading rate of 1 mPa / s, and the failure strength and failure location were recorded. Droplet volume and ejection velocity tests: The ink droplet volume of the inkjet head was measured according to GB / T 47122.2-2026 "Printing Electronic Inkjet Printing Equipment Part 2: Imaging-based Droplet Volume Measurement". The inkjet head sample was a complete piezoelectric inkjet head obtained from S15. The test liquid was 25℃ deionized water. The driving frequency was set to 120kHz, the driving voltage was set to 30V, and the pulse width was set to 3μs. An industrial vision camera with a pixel resolution of not less than 0.5μm / pixel was used to capture images of the ejected droplets. 100 droplets were continuously recorded for each nozzle, and the average droplet volume was calculated. The droplet ejection velocity was measured according to GB / T 47122.1-2026 "Printing Electronic Inkjet Printing Equipment Part 1: Imaging-based Droplet Ejection Velocity Measurement". The ejection velocity was calculated using the displacement and time interval between two adjacent frames of droplet images. High-frequency cyclic drive stability test: The complete piezoelectric inkjet head obtained from S15 was continuously driven for 1000h at a driving frequency of 120kHz, driving voltage of 30V and pulse width of 3μs in an environment of 25℃ and relative humidity of 50%. The test liquid was deionized water and the inlet pressure of the flow channel was maintained at 20kPa. Before and after the cycle, the film d33 was tested according to the piezoelectric strain constant and the film substrate adhesion reliability was tested according to the film substrate adhesion reliability. The film peeling area and nozzle clogging were observed with a microscope. Three inkjet heads were tested in each group, and the d33 attenuation rate, visible peeling area and number of nozzle abnormalities were recorded. The test results are shown in Table 1.

[0049] Table 1 Performance Test Results

[0050] Data Analysis: Table 1 shows that the embodiments exhibit superior overall performance in terms of ceramic target densification, film substrate adhesion reliability, and high-frequency spraying stability, indicating that the present invention does not rely on single powder purification or conventional sputtering deposition to achieve performance improvement. Compared with Comparative Example 1, the embodiments form stable inorganic phosphate microregions on the surface of yttrium phosphate powder through low-dose yttrium ion pre-anchoring, phytic acid dilution treatment, short-term outer layer bridging with high-concentration yttrium ions, and ammonia gas phase fixation. This makes the growth of particle contact necks and pore closure during ceramic target sintering more coordinated, thereby reducing film sputtering defects and high-frequency attenuation. Comparative Example 2 changed the low-dose yttrium ion pre-anchoring sequence and the... In Comparative Example 3, the addition of yttrium ions in a single step did not achieve the effect of Example 1, indicating that the inner layer pre-anchoring and outer layer bridging cannot be simply combined or interchanged. In Comparative Example 4, the removal of phytic acid resulted in the lack of a temporary spatial carrier of phosphate groups, making it difficult to form an effective metering buffer in the particle contact area. In Comparative Example 5, the replacement of ammonia gas phase fixation with ammonia liquid phase adjustment led to excessively rapid changes in local alkalinity, which easily caused non-localized flocculation. Although Comparative Example 6 retained the improvement effect of powder and ceramic targets, the removal of the three-stage gradient deposition resulted in a decrease in film adhesion and jetting stability, indicating that the continuous transition between the low-energy nucleation layer, the linear transition layer, and the main piezoelectric layer plays an important role in the reliability of the inkjet head.

[0051] In summary, the data from the embodiments show that the present invention can continuously improve the performance of piezoelectric inkjet heads from three aspects: powder surface site regulation, ceramic target sintering stability, and piezoelectric thin film gradient deposition. It is suitable for scenarios with 1pL-level small ink droplets, high-frequency driven jetting, and high-resolution inkjet printing, and can reduce the risks of film peeling, jetting attenuation, and droplet volume fluctuation.

[0052] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A piezoelectric single crystal thin film based on yttrium phosphate, characterized in that, The yttrium phosphate piezoelectric single crystal thin film material is obtained by sputtering deposition and annealing of a high-purity yttrium phosphate ceramic target; The high-purity yttrium phosphate ceramic target is obtained by wet pre-dispersing high-purity yttrium phosphate powder, acid pre-adjusting it, and then sequentially treating it with a first yttrium ion dispersion, a phytic acid dilution solution, and a second yttrium ion dispersion. It is then subjected to ammonia gas phase fixation, spray granulation, calcination, pressing, sintering, hot isostatic pressing densification, and machining. Based on 250 parts by weight of high-purity yttrium phosphate powder, the amounts of the first yttrium ion dispersion, the phytic acid diluent, and the second yttrium ion dispersion are 50 parts, 20 parts, and 20 parts, respectively.

2. The piezoelectric single crystal thin film according to claim 1, wherein The first yttrium ion dispersion contains 50 parts by weight, with 0.8-1.2 parts of yttrium nitrate hexahydrate in the first yttrium ion dispersion and the remainder being deionized water; the second yttrium ion dispersion contains 1.8-2.2 parts of yttrium nitrate hexahydrate in the second yttrium ion dispersion and the remainder being deionized water; and the phytic acid diluent contains 1.5-2.5 parts of phytic acid in the phytic acid diluent in the second yttrium ion dispersion and the remainder being deionized water.

3. The piezoelectric single-crystal thin film according to claim 1, characterized in that, The wet pre-dispersion process includes drying high-purity yttrium phosphate powder, adding the dried high-purity yttrium phosphate powder to a mixed dispersion medium for ball milling to obtain yttrium phosphate slurry; after ball milling, filtering the slurry through a 200-mesh nylon sieve; the acid pre-conditioning process includes adding nitric acid to deionized water to form a dilute nitric acid solution; and adding the dilute nitric acid solution to the obtained yttrium phosphate slurry to stabilize the pH of the slurry at 3-4.

4. The piezoelectric single crystal thin film of claim 1, wherein, The ammonia gas phase fixation includes introducing an ammonia-nitrogen mixture into the slurry treated with the second yttrium ion dispersion to slowly raise the pH of the slurry to 5-6; after stopping the gas flow, the slurry is allowed to stand and age at 40-50°C for 1.5-2.5 hours; the ammonia molar fraction in the ammonia-nitrogen mixture is 2%-4%.

5. The piezoelectric single crystal thin film of claim 1, wherein, The spray granulation inlet temperature is 165-175℃, the outlet temperature is 80-90℃, and the atomization pressure is 250-350kPa; the calcination includes placing the powder obtained from spray granulation in an alumina crucible, heating it to 280-320℃ in an air atmosphere furnace at 1℃ / min and holding it at that temperature for 1h, then heating it to 630-670℃ at 2℃ / min and holding it at that temperature for 1.5-2.5h, and then cooling it with the furnace to obtain pretreated yttrium phosphate powder.

6. A method for producing a piezoelectric single crystal thin film according to any one of claims 1 to 5, characterized by, The high-purity yttrium phosphate ceramic target was loaded into the radio frequency magnetron sputtering cavity, pre-sputtered with an argon-oxygen mixture with the baffle closed, and then sputtered to deposit. After the deposition was completed, annealing was performed to obtain a yttrium phosphate-based piezoelectric single crystal thin film.

7. The preparation method according to claim 6, characterized in that, The sputtering deposition process involves evacuating the sputtering chamber to a base vacuum of no more than 5 × 10⁻⁶. -4 The substrate temperature is raised to 650-680℃, and the working pressure is controlled at 0.6-0.8Pa. The first stage of RF power is 90-110W, and the deposition time is 8-12min, forming a micro-phosphorus-rich nucleation layer with a thickness of 60-80nm. The second stage of deposition time is 35-45min, the RF power is linearly increased from 100-110W to 180W, and the argon to oxygen ratio is linearly transitioned from 4:1 to 9:1, forming a transition layer with a thickness of 400-500nm. The third stage of RF power is maintained at 180W, the argon to oxygen ratio is maintained at 9:1, and the deposition time is 200-220min, forming a yttrium phosphate piezoelectric single crystal thin film with a total thickness of 2.8-3.2μm.

8. A piezoelectric ink jet head based on a thin film of a yttrium phosphate piezoelectric single crystal, characterized by The piezoelectric inkjet head includes a silicon-based piezoelectric drive sheet, an ink cavity layer, and a nozzle plate; the yttrium phosphate film in the silicon-based piezoelectric drive sheet is the piezoelectric single crystal film as described in claim 1. The silicon-based piezoelectric drive chip includes a monocrystalline silicon substrate, a silicon dioxide insulating layer disposed on the surface of the monocrystalline silicon substrate, a titanium adhesion layer disposed on the surface of the silicon dioxide insulating layer, a platinum lower electrode disposed on the surface of the titanium adhesion layer, a yttrium phosphate piezoelectric single crystal thin film material disposed on the surface of the platinum lower electrode, and a patterned platinum upper electrode disposed on the surface of the yttrium phosphate piezoelectric single crystal thin film material.

9. The piezoelectric ink-jet head according to claim 8, wherein The thickness of the silicon dioxide insulating layer is 1 μm, the thickness of the titanium adhesion layer is 20 nm, the thickness of the platinum lower electrode is 180 nm, and the thickness of the patterned platinum upper electrode is 220 nm.

10. A method of manufacturing a piezoelectric inkjet head based on a thin film of a yttrium phosphate piezoelectric single crystal according to any one of claims 8 to 9, characterized by, Includes the following steps: (1) Preparation of high-purity yttrium phosphate ceramic target; (2) A silicon dioxide insulating layer, a titanium adhesion layer and a platinum lower electrode are prepared on the surface of a single crystal silicon substrate to obtain a silicon wafer with a platinum lower electrode; (3) Using the high-purity yttrium phosphate ceramic target as the radio frequency sputtering target, deposit and anneal the yttrium phosphate piezoelectric single crystal thin film material on the surface of the silicon wafer with the platinum lower electrode; (4) Fabrication of patterned driving electrode: A patterned platinum top electrode is formed on the surface of the yttrium phosphate piezoelectric single crystal thin film to obtain a piezoelectric driving sheet; (5) Prepare inkjet structure and package: Prepare a nozzle plate with nozzles, form an ink cavity and an ink inlet channel on the back of the piezoelectric drive sheet, and then align and package the nozzle plate with the piezoelectric drive sheet that forms the ink cavity and ink inlet channel to obtain a piezoelectric inkjet head based on yttrium phosphate piezoelectric single crystal thin film.

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