High-density LiNbO3 target material, preparation method, piezoelectric coating and application thereof

Abstract

The invention discloses a high-density LiNbO3 target material, a preparation method, a piezoelectric coating and application of the high-density LiNbO3 target material, and the preparation method of the LiNbO3 target material comprises the following steps: mixing Li2CO3, Nb2O5 and Li2O, and performing compression molding to obtain a green body; and carrying out heat treatment on the green body to obtain the LiNbO3 target material. According to the preparation method, Li2CO3 and Nb2O5 are used, a sintering aid Li2O is introduced and pressed to obtain a green body, the green body is subjected to heat treatment to obtain the high-density LiNbO3 target material, the density reaches up to 4.62-4.64 g / cm < 3 >, the LiNbO3 target material can be used for preparing the single-phase LiNbO3 piezoelectric coating through a sputtering method, and meanwhile the LiNbO3 piezoelectric coating has a high piezoelectric constant.

Description

Technical Field

[0001] The present invention relates to the technical field of LiNbO3 piezoelectric materials and intelligent sensors, and particularly relates to a high-density LiNbO3 target, a preparation method, a piezoelectric coating and an application thereof. Background Art

[0002] Lithium niobate is a ferroelectric of the trigonal crystal system, having good photorefractive effect, piezoelectric effect, pyroelectric effect, acousto-optic effect, electro-optic effect and nonlinear optical effect, and has wide applications in holographic storage, piezoelectric sensors, pyroelectric sensors, acousto-optic modulators, electro-optic modulators, Q-switch in lasers, optical parametric oscillators, optical waveguides and the like. However, the basic substances Li2O and Nb2O5 for synthesizing LiNbO3 can also form three other compounds, namely Li3NbO4, LiNb3O8 and Li2Nb 28 O 71 , the Li3NbO4 phase is called lithium niobate or orthoniobate, while LiNbO3 is called lithium metaniobate. Due to crystal preparation and material properties, only the LiNbO3 phase has piezoelectric properties.

[0003] During the preparation of the target, it is very easy to have LiNb3O8 impurities, and it is impossible to prepare a pure LiNbO3 target. Secondly, during the preparation of thin film deposition, it is also easy to form a lithium-deficient phase LiNb3O8 in the LiNbO3 piezoelectric coating. Some methods use element doping to solve this problem. For example, CN119144930A provides a high-purity light metal-doped LiNbO3 piezoelectric coating and a preparation method thereof. By doping specific contents and specific types of metal elements, a high-purity LiNbO3 piezoelectric coating without lithium-deficient phase LiNb3O8 and without impurity phases such as NbO and Nb2O5 can be deposited. However, doping is not very controllable, and the ionization rates of various elements are different. Especially for light metals, due to the secondary sputtering of Ar ions on the thin film, there are differences in the element content in the thin film and the target.

[0004] Therefore, under the limitation of the sputtering process, optimizing the preparation method of the LiNbO3 target to improve the piezoelectric properties of the LiNbO3 piezoelectric coating has positive significance for expanding the application of the LiNbO3 piezoelectric coating in technical fields such as intelligent sensors, intelligent perception and control devices. Summary of the Invention

[0005] In order to overcome the problems existing in the prior art, the present invention provides a preparation method of a high-density LiNbO3 target, including, Mixing Li2CO3, Nb2O5 and Li2O and pressing them into a mold to obtain a green body; Heat-treating the green body to obtain a high-density LiNbO3 target.

[0006] Further, before mixing, the Li2CO3, Nb2O5 and Li2O are respectively subjected to water removal and preheating treatment; The Li2CO3 and Nb2O5 are proportioned according to the molar ratio of Li to Nb of 1:1, and the molar ratio of Nb2O5 to Li2O is 8 - 10:0.5 - 1.5.

[0007] Preferably, the water removal treatment can keep the Li2CO3, Nb2O5 and Li2O at 100 °C for 100 h respectively before mixing.

[0008] Further, the preheating treatment is carried out in multiple stages at 300 - 900 °C, wherein the temperature and time of the next stage of preheating treatment are higher than those of the previous stage; Preferably, the preheating treatment is carried out in three stages, and is kept at 400 °C, 600 °C and 800 °C for 5 h, 10 h and 20 h respectively.

[0009] Preferably, before pressing, the Li2CO3, Nb2O5 and Li2O are mixed by ball milling, then dried and passed through a 300 - 500 mesh sieve to obtain fine powder, and the fine powder is heat - treated at 100 - 500 °C in multiple stages. Among them, the temperature of the next stage is lower than that of the previous stage, but the time of the next stage is longer than that of the previous stage. Specifically, in the ball - milling process, the Li2CO3, Nb2O5 and Li2O are mixed with anhydrous ethanol or deionized water and put into a ball - milling tank, and ground with zirconia balls for 10 - 20 hours. The ball - milling speed is 200 - 300 rpm for the first 5 - 10 hours and 300 - 500 rpm for the last 5 - 10 hours; after drying, it is passed through a 300 - 500 mesh sieve to obtain fine powder.

[0010] Preferably, the heat treatment of the fine powder is kept at 400 - 500 °C, 200 - 400 °C and 100 - 200 °C for 1 - 2 h, 2 - 4 h and 10 - 14 h respectively.

[0011] Further, the purity of the Li2CO3, Nb2O5 and Li2O is higher than 99.99% and the particle size is lower than 800 nm; The pressing is carried out at a pressure of 200 - 500 MPa for 5 - 10 h. By extending the pressing time, internal pores are eliminated again and the voids between particles are reduced.

[0012] Preferably, the pressing is realized by isostatic pressing using a corresponding mold. In order to avoid non - uniform density in the plane direction, a pre - green body with a thickness of 2 mm is pressed each time, and finally multiple pre - green bodies are combined and pressed into a green body. Specifically, the thickness and shape of the green body can be selected according to the requirements of the target of the actual magnetron sputtering equipment, and there is no strict limitation. Exemplarily, the green body can be a cylinder with a height of 4 - 6 mm and a diameter of 145 - 195 mm.

[0013] Further, a sintering process is carried out on the green body. The sintering process is carried out in multiple stages at 500 - 1300 °C, wherein the temperature and time of the next heat treatment are lower than those of the previous stage.

[0014] Preferably, the sintering process is carried out in three stages, and is kept warm at 1000 - 1300 °C, 600 - 800 °C, and 300 - 500 °C for 1 - 2 h, 2 - 4 h, and 10 - 14 h respectively.

[0015] Preferably, after the sintering process of the green body, a slow cooling treatment is carried out, and the cooling rate is 5 - 10 °C / min to avoid cracking caused by thermal stress.

[0016] Preferably, after the cooling treatment, the surface of the product is polished to ensure that the surface of the obtained LiNbO3 target is flat.

[0017] The present invention also provides a high-density LiNbO3 target obtained by the above preparation method. The density of the prepared high-density lithium niobate target is between 4.62 - 4.64 g / cm 3 . (The theoretical density of single crystal lithium niobate is 4.64 g / cm³) The present invention also provides a preparation method of a LiNbO3 piezoelectric coating, which is prepared on the surface of a substrate by magnetron sputtering using the above high-density LiNbO3 target.

[0018] The magnetron sputtering method includes pre-sputtering, ultra-low oxygen pressure sputtering, and low oxygen pressure sputtering.

[0019] Further, the parameters of the target pre-sputtering are: radio frequency power 800 - 1200 W, total gas pressure of Ar and O2 0.5 - 1.5 Pa, Ar / O2 gas flow ratio 2.5 - 6.2 / 1, temperature 150 - 250 °C, time 5 - 15 min; when pre-sputtering the target, the substrate is placed back to the target to pre-sputter the target and fully remove the oxide layer on the surface of the target; The parameters of the ultra-low oxygen pressure sputtering are: radio frequency power 800 - 1200 W, total gas pressure of Ar gas and O2 0.5 - 1.5 Pa, Ar / O2 gas flow ratio 4.2 / 1 - 8.2 / 1, substrate temperature 320 - 390 °C, target-substrate distance 4.2 - 5.5 cm, coating time 3 - 6 h; since there is a small amount of O2 in the cavity at the initial stage of coating, the input oxygen partial pressure should be reduced at this time; The parameters of the low oxygen pressure sputtering are: radio frequency power 800 - 1200 W, total gas pressure of Ar gas and O2 0.5 - 1.5 Pa, Ar / O2 gas flow ratio 3.5 / 1 - 4.2 / 1, substrate temperature 320 - 390 °C, target-substrate distance 4.2 - 5.5 cm, coating time 3 - 6 h.

[0020] In the present invention, there is no strict limitation on the material and morphology of the substrate, which can be a silicon wafer, a stainless steel sheet, a bolt, etc. Preferably, before sputtering coating on the substrate, the substrate is treated by etching, polishing, etc. to remove the oxide film. Preferably, ion etching can be used to fully remove the oxide film on the surface layer of the substrate. The specific parameters are as follows: the total Ar gas pressure is 0.5 Pa - 1.0 Pa, the voltage is 150 - 250 V, the duty cycle is 40 - 90%, the current is 0.32 - 1.21 A, and the etching time is 30 - 60 min.

[0021] The present invention also provides a LiNbO3 piezoelectric coating obtained by the above preparation method.

[0022] The present invention further provides the application of the above LiNbO3 piezoelectric coating in the sensing field.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a preparation method of a high-density lithium niobate target. Starting from aspects such as raw material selection, process optimization, and post-heat treatment, the density of the target is increased, and the density is increased to 4.62 - 4.64 g / cm 3 .

[0024] The present invention uses Li2CO3 and Nb2O5, and after introducing the sintering aid Li2O, pressing to obtain a green body and then heat treatment to obtain a high-density LiNbO3 target. This LiNbO3 target can prepare a single-phase LiNbO3 piezoelectric coating by sputtering method, and at the same time, the LiNbO3 piezoelectric coating has a high piezoelectric constant. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0026] Figure 1 Shows the XRD pattern of the piezoelectric coating prepared in Example 1; Figure 2 Shows the XRD pattern of the piezoelectric coating prepared in Comparative Example 1; Figure 3 Shows the ultrasonic signal and piezoelectric constant diagram of the piezoelectric coating prepared in Example 1; Figure 4 Shows the ultrasonic signal and piezoelectric constant diagram of the piezoelectric coating prepared in Comparative Example 1; Figure 5Shows the XRD pattern of the piezoelectric coating prepared in Example 2; Figure 6 Shows the ultrasonic signal and piezoelectric constant diagram of the piezoelectric coating prepared in Example 2 during continuous annealing at 700 °C; Figure 7 Shows the ultrasonic signal diagram of the piezoelectric coating prepared in Example 3 during continuous annealing at 700 °C; Figure 8 Shows the piezoelectric constant diagram of the piezoelectric coating prepared in Example 3 when annealed at 700 °C for 0 h, 50 h, and 100 h; Figure 9 Shows the ultrasonic signal diagram of the piezoelectric coating prepared in Example 3 when annealed at 700 °C for 0 h, 50 h, and 100 h. Detailed implementation manners

[0027] In the ranges disclosed in the present invention, the endpoints and any values are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the specific embodiments of the present invention and the accompanying drawings of the specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0029] Example 1 A preparation method of a high-density LiNbO3 piezoelectric coating includes the following steps: 1. Prepare a high-density LiNbO3 target (1) Raw material preparation and pretreatment: Spherical Li2CO3, Nb2O5, and sintering aid Li2O with a purity of 99.99% and a particle size of 600 nm are each maintained at 100 °C for 100 h for water removal treatment to fully remove the moisture in Li2CO3, Nb2O5, and Li2O. Subsequently, the dried Li2CO3, Nb2O5, and Li2O are subjected to preheating treatment, specifically at 400 °C, 600 °C, and 800 °C for 5 h, 10 h, and 20 h respectively, to remove impurities and improve crystallinity.

[0030] (2) Raw material mixing: Li2CO3 and Nb2O5 treated in step (1) were weighed in a molar ratio (Li:Nb=1:1), and the molar ratio of Nb2O5 to sintering aid Li2O was 10:1.2. The mixture was put into a ball mill, and anhydrous ethanol was added. The mixture was milled using zirconia balls for 15 hours. The ball milling speed was 200 rpm for the first 7 hours and 500 rpm for the next 8 hours. After drying, the mixture was sieved through a 400-mesh sieve to obtain a fine powder.

[0031] (3) Heat treatment of fine powder: The fine powder obtained in the previous step was kept at 400°C, 300°C and 200°C for 2h, 4h and 14h respectively.

[0032] (4) Target forming: Using a mold, a green body with a diameter of 145 mm and a thickness of 4 mm was isostatically pressed. The pressing pressure was increased to 400 MPa and the pressing time was extended to 10 h to further eliminate internal pores and reduce the gaps between particles. A layered pressing method was used, that is, the target material was pressed 2 mm thick each time, and finally combined and pressed into a whole to avoid uneven density in the planar direction.

[0033] (5) Target sintering: The green body is placed in a N2 protective atmosphere (to prevent decomposition of lithium niobate) and sintered to promote grain growth and densification. A three-step sintering method is used, with a high-temperature rapid sintering at 1100°C for 2 hours, a medium-temperature sintering at 800°C for 4 hours, and a final low-temperature holding time of 500°C for 12 hours to inhibit excessive grain growth.

[0034] (6) Cooling: The sintered green body is cooled at a rate of 8°C / min.

[0035] (7) Surface treatment: The cooled blank was polished to ensure a smooth surface and obtain a high-density LiNbO3 target. The mass of the lithium niobate target was 305.49 g, and the calculated density was as high as 4.625 g / cm 3 , which is very close to the theoretical single crystal density of lithium niobate.

[0036] 2. Preparation of LiNbO3 piezoelectric coating (1) Substrate pretreatment: Use a stainless steel sheet as the substrate and perform ion etching on the stainless steel sheet to fully remove the oxide film on the surface of the substrate. The etching parameters are: Ar gas total pressure 0.6 Pa, voltage 200 V, duty cycle 50%, current 0.8 A, and etching time 40 min.

[0037] (2) Target pre-sputtering: Pre-sputter the high-density LiNbO3 target (the substrate is placed with its back to the target) to fully remove the surface oxide layer of the target. The sputtering parameters are: RF power 900W, total pressure of Ar gas and O2 0.9Pa, Ar / O2 gas flow ratio 4 / 1, temperature 150℃, and time 5min.

[0038] (3)Ultra-low oxygen pressure sputtering: Rotate the substrate to face the target, and adjust the distance between the center of the substrate and the center of the target. The distance is represented by the radial (distance from the center) distance. A radial distance of 0 indicates that the center of the substrate coincides with the center of the target. Define a direction. The larger the radial distance, the farther the center of the substrate deviates from the center of the target. Different signs of the radial distance indicate different directions. Adjust the radial distance from -7 cm to 7 cm and perform sputtering. Sputtering parameters: RF power 900 W, total gas pressure of Ar and O2 0.9 Pa, Ar / O2 gas flow ratio 4.25 / 1, substrate temperature 340 °C, target-substrate distance 4.3 cm, time 4 h. Since there is a small amount of O2 in the chamber at the initial stage of sputtering growth, the input oxygen partial pressure should be reduced at this time.

[0039] (4)Low oxygen pressure sputtering: Regulate the deposition parameters and continue sputtering growth. Sputtering parameters: RF power 900 W, total gas pressure of Ar and O2 0.9 Pa, Ar / O2 gas flow ratio 3.8 / 1, substrate temperature 340 °C, target-substrate distance 5.0 cm, time 4 h.

[0040] Example 2 It is basically the same as Example 1, except that: the target-substrate distances in ultra-low oxygen pressure sputtering and low oxygen pressure sputtering are both 5.1 cm, and the radial distances are adjusted to 0 and 4 cm.

[0041] Example 3 It is basically the same as Example 1, except that: a bolt is used as the substrate. The bolt is made of stainless steel, with a length of 5 cm. The target-substrate distances in ultra-low oxygen pressure sputtering and low oxygen pressure sputtering are both 5.1 cm, and the radial distance is adjusted to 0.

[0042] Comparative Example 1 Compared with Example 1, the difference is that: a conventional lithium niobate target is used to replace the high-density LiNbO3 target to prepare a piezoelectric coating on the surface of a stainless steel sheet substrate.

[0043] The conventional lithium niobate target is uniformly mixed and pressed from two-phase lithium niobate oxides of LiNbO3 and LiNb3O8 and Li2O powder, LiNbO3:LiNb3O8:Li2O = 1:1:1, and the density of the lithium niobate target is 4.40 g / cm 3 .

[0044] Test Example Use XRD to test the piezoelectric coatings prepared in Example 1 and Comparative Example 1. It can be seen from Figure 1 that when the radial distances are 0 and 4 cm, only the LiNbO3 piezoelectric phase exists in the piezoelectric coating prepared in Example 1. And from Figure 2It can be seen that under the same conditions, the piezoelectric coating prepared in Comparative Example 1 simultaneously has LiNbO3, LiNb3O8, NbO, and Nb2O5 phases, rather than a pure LiNbO3 piezoelectric phase.

[0045] The piezoelectric constant and ultrasonic signal of the piezoelectric coatings prepared in Example 1 and Comparative Example 1 were tested. It can be seen from Figure 3 and Figure 4 that in the same direction, the piezoelectric constant and ultrasonic signal of the piezoelectric coating decrease as the absolute value of the radial distance increases, and both have a maximum value when the radial distance is 0, that is, the center of the substrate coincides with the center of the target. In addition, the highest piezoelectric constant and ultrasonic signal of the piezoelectric coating prepared in Example 1 are 14.3 pC / N and 2.53 V respectively, and the highest piezoelectric constant and ultrasonic signal of the piezoelectric coating prepared in Comparative Example 1 are 2.9 pC / N and 0.24 V respectively. That is, under the same conditions, the high-density LiNbO3 target increases the piezoelectric constant and ultrasonic signal by 4.93 times and 10.54 times respectively.

[0046] The piezoelectric coating prepared in Example 2 was tested using XRD. It can be seen from Figure 5 that the crystal form of the prepared piezoelectric coating is basically the same as that of Example 1.

[0047] The piezoelectric coating prepared in Example 2 at a radial distance of 0 was transferred to 700 °C for annealing to study its high-temperature stability. It can be seen from Figure 6 that at 700 °C, as the annealing time prolongs, both the piezoelectric constant and ultrasonic signal gradually increase, and reach the highest value at 160 h, and there is no obvious decrease during the 300 h test time, indicating that the piezoelectric coating has high high-temperature stability.

[0048] The bolt with the piezoelectric coating prepared in Example 3 was transferred to 700 °C for annealing, and the ultrasonic signal and piezoelectric constant at different annealing times were tested. It can be seen from Figures 7 - 9 that the piezoelectric coating prepared on the bolt has high-temperature stability at 700 °C, and the piezoelectric constant remains stable at 7.7 pC / N after annealing for 100 h.

[0049] Comparative Example 2 Compared with Example 1, the difference is that during the preparation of the target, no sintering aid was used, and the density of the prepared lithium niobate target is 4.50 g / cm 3 .

[0050] The piezoelectric constant and ultrasonic signal of the piezoelectric coating prepared in Comparative Example 2 were tested. The highest piezoelectric constant and ultrasonic signal (i.e., at the sputtering center) were 4.3 pC / N and 0.55 V respectively, which were much lower than 14.3 pC / N and 2.53 V of Example 1. At the same time, the piezoelectric coating prepared in Comparative Example 2 contained LiNbO3, LiNb3O8, NbO, and Nb2O5 phases, rather than a pure LiNbO3 piezoelectric phase.

[0051] Comparative Example 3 Compared with Example 1, the difference lies in that during the preparation of the target, the molar ratio of Nb2O5 to the sintering aid Li2O was 10:1.6. Due to excessive sintering aid, the number of pores in the target increased, and the density of the prepared lithium niobate target was 4.58 g / cm 3 .

[0052] The piezoelectric constant and ultrasonic signal of the piezoelectric coating prepared in Comparative Example 3 were tested. The highest piezoelectric constant and ultrasonic signal (i.e., at the sputtering center) were 4.7 pC / N and 0.61 V respectively, which were much lower than 14.3 pC / N and 2.53 V of Example 1. At the same time, the piezoelectric coating prepared in Comparative Example 3 contained LiNbO3, LiNb3O8, NbO, and Nb2O5 phases, rather than a pure LiNbO3 piezoelectric phase.

[0053] Comparative Example 4 Compared with Example 1, the difference lies in that during the preparation of the target, instead of pressing a preform with a thickness of 2 mm each time, a blank with a thickness of 4 mm was directly pressed. The density of the prepared lithium niobate target was 4.60 g / cm 3 .

[0054] The piezoelectric constant and ultrasonic signal of the piezoelectric coating prepared in Comparative Example 4 were tested. The highest piezoelectric constant and ultrasonic signal (i.e., at the sputtering center) were 6.9 pC / N and 0.92 V respectively, which were much lower than 14.3 pC / N and 2.53 V of Example 1. At the same time, the piezoelectric coating prepared in Comparative Example 4 contained LiNbO3, LiNb3O8, NbO, and Nb2O5 phases, rather than a pure LiNbO3 piezoelectric phase.

[0055] Comparative Example 5 Compared with Example 1, the difference lies in that during the preparation of the target, in the target forming step, the pressing pressure was reduced to 190 MPa. The density of the prepared lithium niobate target was 4.45 g / cm 3 .

[0056] The piezoelectric constant and ultrasonic signal of the piezoelectric coating prepared in Comparative Example 5 were tested. The piezoelectric constant and the highest ultrasonic signal (i.e., at the sputtering center) were 3.6 pC / N and 0.34 V respectively, which were much lower than 14.3 pC / N and 2.53 V of Example 1. At the same time, the piezoelectric coating prepared in Comparative Example 5 contained LiNbO3, LiNb3O8, NbO, and Nb2O5 phases, rather than a pure LiNbO3 piezoelectric phase.

[0057] Comparative Example 6 Compared with Example 1, the difference lies in that during the preparation of the target, in the target forming step, the pressing time was shortened to 4.5 h. The density of the prepared lithium niobate target was 4.47 g / cm 3 .

[0058] The piezoelectric constant and ultrasonic signal of the piezoelectric coating prepared in Comparative Example 6 were tested. The piezoelectric constant and the highest ultrasonic signal (i.e., at the sputtering center) were 3.8 pC / N and 0.37 V respectively, which were much lower than 14.3 pC / N and 2.53 V of Example 1. At the same time, the piezoelectric coating prepared in Comparative Example 6 contained LiNbO3, LiNb3O8, NbO, and Nb2O5 phases, rather than a pure LiNbO3 piezoelectric phase.

[0059] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a high-density LiNbO3 target, characterized in that, including Mix Li2CO3, Nb2O5 and Li2O and press them into a compact to obtain a green body Heat-treat the green body to obtain a high-density LiNbO3 target 2. The preparation method of the high-density LiNbO3 target according to claim 1, wherein Before mixing, Li2CO3, Nb2O5 and Li2O are respectively dehydrated and preheated Li2CO3 and Nb2O5 are mixed in a molar ratio of Li to Nb of 1:1, and the molar ratio of Nb2O5 to Li2O is 8-10:0.5-1.5 The purities of Li2CO3, Nb2O5 and Li2O are higher than 99.99% and the particle sizes are lower than 800 nm 3. The preparation method of the high-density LiNbO3 target according to claim 2, characterized in that, The preheating is carried out in multiple stages at 300-900 °C, where the temperature and time of the next stage of preheating are higher than those of the previous stage 4. The preparation method of the high-density LiNbO3 target according to claim 1, wherein, Before pressing, Li2CO3, Nb2O5 and Li2O are mixed by wet ball milling, then dried and passed through a 300-500 mesh sieve to obtain fine powder, and the fine powder is heat-treated at 100-500 °C in multiple stages. Among them, the temperature of the next stage is lower than that of the previous stage, but the time of the next stage is longer than that of the previous stage 5. The preparation method of the high-density LiNbO3 target according to claim 1, characterized in that, The pressing is carried out at a pressure of 200-500 MPa for 5-10 h The heat treatment is carried out in multiple stages at 500-1300 °C, where the temperature and time of the next stage of heat treatment are lower than those of the previous stage 6. A high-density LiNbO3 target, characterized in that, Obtained by using the preparation method according to any one of claims 1-5 7. A preparation method of a LiNbO3 piezoelectric coating, characterized in that, Prepared on the surface of a substrate by magnetron sputtering using the high-density LiNbO3 target according to claim 6 The magnetron sputtering method includes target pre-sputtering, ultra-low oxygen pressure sputtering and low oxygen pressure sputtering 8. The preparation method of the LiNbO3 piezoelectric coating according to claim 7, characterized in that, The parameters of the target pre-sputtering are: radio frequency power 800-1200 W, total gas pressure of Ar and O2 0.5-1.5 Pa, Ar / O2 gas flow ratio 2.5-6.2 / 1, temperature 150-250 °C, time 5-15 min The parameters of the ultra-low oxygen pressure sputtering are: radio frequency power 800-1200 W, total gas pressure of Ar gas and O2 0.5-1.5 Pa, Ar / O2 gas flow ratio 4.2 / 1-8.2 / 1, substrate temperature 320-390 °C, target-substrate distance 4.2-5.5 cm, coating time 3-6 h The parameters of the low oxygen pressure sputtering are: radio frequency power 800-1200 W, total gas pressure of Ar gas and O2 0.5-1.5 Pa, Ar / O2 gas flow ratio 3.5 / 1-4.2 / 1, substrate temperature 320-390 °C, target-substrate distance 4.2-5.5 cm, coating time 3-6 h 9. A LiNbO3 piezoelectric coating, characterized in that, Obtained by using the preparation method according to claim 7 or 8 10. Application of the LiNbO3 piezoelectric coating according to claim 9 in the sensing field

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