Fiber-reinforced composite ceramic materials and their preparation methods, piezoelectric ceramic bicrystalline wafers and their preparation methods

Abstract

This invention provides a fiber-reinforced composite ceramic material and its preparation method, as well as a piezoelectric ceramic bilayer and its preparation method. The preparation method of the fiber-reinforced composite ceramic material includes: preparing a predetermined amount of piezoelectric ceramic slurry; doping the piezoelectric ceramic slurry with a fiber-reinforced material to obtain the fiber-reinforced composite ceramic material; wherein the weight ratio of the fiber-reinforced material to the piezoelectric ceramic slurry is 1% to 10%; and the length of the fiber-reinforced material is less than or equal to 15 μm. The fiber-reinforced composite ceramic material of this application is used to prepare a fiber-reinforced composite ceramic film for the driving layer of a piezoelectric ceramic bilayer. By adding fiber-reinforced material to the driving layers on both sides of the piezoelectric ceramic bilayer, the toughness and bending strength of the driving layers on both sides are enhanced.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric bicrystalline wafer technology, and more specifically, to a fiber-toughened composite ceramic material and its preparation method, and a piezoelectric ceramic bicrystalline wafer and its preparation method. Background Technology

[0002] The carbon fiber bicrystalline wafer, composed of a carbon fiber structural layer and upper and lower ceramic actuation layers bonded together, is the core component of a miniature air valve and is widely used in equipment or systems such as ventilators, non-invasive blood pressure monitors, and ophthalmic surgery.

[0003] Carbon fiber bilayers consist of upper and lower ceramic layers, and a carbon fiber layer between them. In terms of carbon fiber fabrication, the ceramic layer is prepared by sintering followed by grinding. The thin ceramic sheet is highly susceptible to breakage during grinding and handling, making the fabrication of carbon fiber bilayers very difficult, with high process control challenges and manufacturing costs. Furthermore, the bonding process between the ceramic sheet and the carbon fiber is also prone to breakage. Therefore, the manufacturing yield of this type of carbon fiber bilayer is relatively low. Summary of the Invention

[0004] The main objective of this invention is to provide a fiber-reinforced composite ceramic material and its preparation method, as well as a piezoelectric ceramic bicrystalline wafer and its preparation method, to solve the technical problem that the ceramic wafers of the bicrystalline wafer are prone to breakage during the preparation process in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a fiber-toughened composite ceramic material is provided, comprising: step S01: preparing a predetermined amount of piezoelectric ceramic slurry; step S02: doping the piezoelectric ceramic slurry with a fiber-toughening material to obtain a fiber-toughened composite ceramic material; wherein the weight ratio of the fiber-toughening material to the piezoelectric ceramic slurry is 1% to 10%; and the length of the fiber-toughening material is less than or equal to 15 μm.

[0006] Optionally, the length of the fiber-reinforced material is 5 μm to 15 μm.

[0007] Optionally, the fiber toughening material is zirconia fiber, glass fiber, or needle-like wollastonite fiber.

[0008] Optionally, in step S02, a ball mill is used to grind the piezoelectric ceramic slurry containing fiber-reinforced material, with a grinding speed of 10 rpm to 50 rpm and a grinding time of 10 h to 24 h.

[0009] According to another aspect of the present invention, a fiber-reinforced composite ceramic material is provided, which is prepared by the above-described preparation method.

[0010] According to a third aspect of the present invention, a method for preparing a piezoelectric ceramic bicrystalline wafer is provided, comprising:

[0011] Step S1: Obtain multiple ceramic membranes;

[0012] Step S2: Obtain the above-mentioned fiber-toughened composite ceramic material, and use a casting process to make multiple fiber-toughened composite ceramic films from the fiber-toughened composite ceramic material.

[0013] Step S3: Stack a portion of the fiber-toughened composite ceramic membranes in sequence to form the first driving membrane layer;

[0014] Step S4: Print an inner electrode metal paste on the upper surface of the first driving diaphragm layer to form an inner electrode pattern;

[0015] Step S5: A ceramic film is coated on the upper surface of the first driving film layer with the internal electrode pattern, and an internal electrode metal paste is printed on the upper surface of the coated ceramic film to form an internal electrode pattern on the upper surface of the coated ceramic film.

[0016] Step S6: On the upper surface of the ceramic film with the inner electrode pattern formed in step S5, another ceramic film is covered, and an inner electrode metal paste is printed on the upper surface of the covered ceramic film to form an inner electrode pattern on the upper surface of the covered ceramic film.

[0017] Step S7: Repeat step S6 until an intermediate structure film layer with multiple alternating layers of internal electrode patterns and ceramic films is formed;

[0018] Step S8: Stack another portion of the fiber-toughened composite ceramic films in sequence to form a second driving film layer; and cover the upper surface of the intermediate structure film layer with the internal electrode pattern to obtain a green blank.

[0019] Step S9: Cut the blank block to obtain multiple bicrystalline blanks;

[0020] Step S10: Heat-treat and apply external electrodes to multiple bicrystalline wafer blanks to finally obtain a piezoelectric ceramic bicrystalline wafer including a first driving layer, an intermediate structural layer and a second driving layer.

[0021] Optionally, in step S8, the preparation method further includes: performing stacking molding, vacuum sealing, and isostatic pressing on the green blank block.

[0022] Optionally, when performing isostatic pressing on the green blank block, the isostatic pressing pressure is 300 bar to 700 bar, and the isostatic pressing holding time is 5 min to 20 min.

[0023] Optionally, the heat treatment includes debinding and sintering steps.

[0024] Optionally, when performing the debinding step on multiple bicrystalline wafer blanks, the debinding temperature is 500°C to 700°C; when performing the sintering step on multiple bicrystalline wafer blanks, the sintering temperature is 950°C to 1000°C.

[0025] Optionally, the thickness of the fiber-toughened composite ceramic membrane is 20 μm to 40 μm, and the thickness of the ceramic membrane is 20 μm to 40 μm.

[0026] Optionally, the thickness of the first driving diaphragm layer is 120 μm to 150 μm; the thickness of the second driving diaphragm layer is 120 μm to 150 μm; and the thickness of the intermediate structure diaphragm layer is 200 μm to 250 μm.

[0027] According to a fourth aspect of the present invention, a piezoelectric ceramic bicrystalline wafer is provided, comprising a first driving layer, an intermediate structural layer, and a second driving layer stacked sequentially in a vertical direction; wherein the first driving layer and the second driving layer each include a plurality of stacked fiber-toughened composite ceramic dielectric layers formed of fiber-toughened composite ceramic films; the intermediate structural layer includes a plurality of ceramic dielectric layers formed of ceramic films and a plurality of inner electrode layers formed of inner electrode patterns, and the plurality of ceramic dielectric layers and the plurality of inner electrode layers are alternately stacked; an inner electrode layer is disposed between the first driving layer and the intermediate structural layer, and between the second driving layer and the intermediate structural layer; an outer electrode layer is disposed on the outer surface of both the first driving layer and the second driving layer.

[0028] According to the technical solution of the present invention, the preparation method of fiber-toughened composite ceramic material includes: step S01: preparing a predetermined amount of piezoelectric ceramic slurry; step S02: doping the piezoelectric ceramic slurry with fiber-toughening material to obtain fiber-toughened composite ceramic material; wherein, the weight ratio of fiber-toughening material to piezoelectric ceramic slurry is 0.01 to 0.1; and the length of fiber-toughening material is greater than 0 and less than or equal to 15 μm.

[0029] The fiber-toughened composite ceramic material of this application is used to prepare fiber-toughened composite ceramic films for the driving layer of piezoelectric ceramic bilayers. By adding fiber-toughening materials to the driving layers on both sides of the piezoelectric ceramic bilayer, the toughness and bending strength of the driving layers on both sides are enhanced.

[0030] The piezoelectric ceramic bicrystalline wafer fabrication method of this application avoids the direct fabrication of ultrathin ceramic sheets, that is, it eliminates the need to obtain ultrathin ceramic sheets through grinding, thus avoiding damage to the ceramic sheets during grinding and assembly; it significantly improves the yield and reduces the process cost.

[0031] The piezoelectric ceramic bicrystalline wafer of this application has the characteristics of simple fabrication process, large displacement, large thrust, long life and low driving voltage. Attached Figure Description

[0032] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 A schematic diagram of the structure of the piezoelectric ceramic bicrystalline wafer according to the present invention is shown;

[0034] Figure 2 A schematic diagram of the structure of the unfinished blank block according to the present invention is shown;

[0035] Figure 3 A schematic diagram of the structure of the ceramic diaphragm according to the present invention is shown;

[0036] Figure 4 A schematic diagram of the structure of the fiber-toughened composite ceramic membrane according to the present invention is shown;

[0037] Figure 5 A schematic diagram of the structure of the ceramic diaphragm and the internal electrode pattern on its upper surface according to the present invention is shown;

[0038] Figure 6 A schematic diagram of the structure of the fiber-toughened composite ceramic diaphragm and the internal electrode pattern on its surface according to the present invention is shown.

[0039] Figure 7 A schematic diagram of the structure of the biwafer blank and the external electrode patterns on its two outer surfaces according to the present invention is shown.

[0040] Figure 8 A schematic diagram of the actuation of a piezoelectric ceramic bicrystalline wafer according to the present invention is shown;

[0041] Figure 9 A schematic diagram of the test for the bending strength of bicrystalline wafers is shown.

[0042] The above figures include the following reference numerals:

[0043] 10. First driving layer; 20. Second driving layer; 30. Intermediate structure layer;

[0044] 40. Inner electrode pattern; 50. Ceramic diaphragm; 60. Driving diaphragm layer; 61. Fiber-toughened composite ceramic diaphragm; 70. Outer electrode pattern;

[0045] 91. Bottom support component; 92. Thrust test probe; 93. Tested dual crystal wafers. Detailed Implementation

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0048] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0049] This invention provides a method for preparing a fiber-toughened composite ceramic material, comprising: step S01: preparing a predetermined amount of piezoelectric ceramic slurry; step S02: doping the piezoelectric ceramic slurry with a fiber-toughening material to obtain a fiber-toughened composite ceramic material; wherein the weight ratio of the fiber-toughening material to the piezoelectric ceramic slurry is 0.01 to 0.1; and the length of the fiber-toughening material is greater than 0 and less than or equal to 15 μm.

[0050] The fiber-toughened composite ceramic material of this application is used to prepare fiber-toughened composite ceramic films for the driving layer of piezoelectric ceramic bilayers. By adding fiber-toughening materials to the driving layers on both sides of the piezoelectric ceramic bilayer, the toughness and bending strength of the driving layers on both sides are enhanced.

[0051] Optionally, the length of the fiber-reinforced material is 5 μm to 15 μm.

[0052] Optionally, the fiber toughening material is zirconia fiber, glass fiber, or needle-like wollastonite fiber.

[0053] Optionally, the piezoelectric ceramic slurry is PZT5H-L piezoelectric ceramic slurry.

[0054] In this application, the method for preparing the piezoelectric ceramic slurry in step S01 includes steps S011 to S013.

[0055] Step S011: Prepare a preset amount of piezoelectric ceramic powder; wherein the particle size of the piezoelectric ceramic powder is 500nm to 600nm, the piezoelectric ceramic powder is soft piezoelectric ceramic powder, the Curie temperature of the piezoelectric ceramic powder is 200℃ to 600℃, and the sintering temperature of the piezoelectric ceramic powder is 950℃ to 1010℃.

[0056] Step S012: Prepare the required raw materials according to the predetermined proportions. The required raw materials include piezoelectric ceramic powder, binder, plasticizer, solvent, and dispersant. The weight percentage of piezoelectric ceramic powder is 40% to 65%, the weight percentage of binder is 4% to 10%, the weight percentage of plasticizer is 2% to 5%, the weight percentage of solvent is 16% to 28%, and the weight percentage of dispersant is 2% to 7%, which is the predetermined proportion.

[0057] Optionally, the piezoelectric ceramic powder is PZT5H-L piezoelectric ceramic powder.

[0058] Optionally, the particle size of the piezoelectric ceramic powder is 500 nm.

[0059] Step S013: Ball mill the raw materials in a predetermined ratio to obtain the piezoelectric ceramic slurry to be used.

[0060] Optionally, a ball mill is used to ball mill the raw materials in a predetermined proportion, that is, the raw materials in a predetermined proportion are put into the ball mill jar of the ball mill; the ball mill speed is 300 rpm to 500 rpm, and the ball milling time is 6 h to 12 h.

[0061] Optionally, the ball mill used for ball milling the raw materials is a planetary ball mill.

[0062] In this application, step S02 includes the following specific steps: preparing fiber toughening material according to a preset ratio, wherein the preset ratio is the weight ratio of fiber toughening material to piezoelectric ceramic slurry; and pouring the fiber toughening material prepared according to the preset ratio into the piezoelectric ceramic slurry.

[0063] Specifically, in step S02, the specific operation steps further include: grinding the piezoelectric ceramic slurry containing fiber toughening material to obtain fiber toughening casting slurry.

[0064] The piezoelectric ceramic slurry containing fiber-reinforced material is ground and stirred to ensure that the fiber-reinforced material is uniformly mixed in the piezoelectric ceramic slurry.

[0065] Alternatively, a ball mill can be used to slowly grind the piezoelectric ceramic slurry containing fiber-reinforced material at a speed of 10 rpm to 50 rpm for a grinding time of 10 h to 24 h.

[0066] Optionally, the ball mill used to grind the piezoelectric ceramic slurry containing fiber-reinforced material is a drum ball mill.

[0067] The present invention also provides a fiber-toughened composite ceramic material, which is prepared by the above-described preparation method.

[0068] The present invention also provides a method for preparing a piezoelectric ceramic bicrystalline wafer, which includes steps S1 to S10.

[0069] Step S1: Obtain multiple ceramic membranes.

[0070] Optionally, the thickness of the ceramic membrane is 20 μm to 40 μm.

[0071] Specifically, the ceramic diaphragm is a piezoelectric ceramic diaphragm.

[0072] Step S2: Obtain the above-mentioned fiber-toughened composite ceramic material, and use a casting process to make multiple fiber-toughened composite ceramic films from the fiber-toughened composite ceramic material.

[0073] Optionally, the thickness of the fiber-toughened composite ceramic membrane is 20 μm to 40 μm.

[0074] Step S3: Stack a portion of the fiber-toughened composite ceramic membranes in sequence to form the first driving membrane layer.

[0075] Optionally, the thickness of the first driving diaphragm layer is 120 μm to 150 μm.

[0076] Step S4: Print an inner electrode metal paste on the upper surface of the first driving diaphragm layer to form an inner electrode pattern on the upper surface of the first driving diaphragm layer.

[0077] Step S5: A ceramic film is coated on the upper surface of the first driving film layer with the internal electrode pattern, and an internal electrode metal paste is printed on the upper surface of the coated ceramic film to form the internal electrode pattern on the upper surface of the coated ceramic film.

[0078] Step S6: On the upper surface of the ceramic film with the inner electrode pattern formed in step S5, another ceramic film is covered, and an inner electrode metal paste is printed on the upper surface of the covered ceramic film to form an inner electrode pattern on the upper surface of the covered ceramic film.

[0079] Step S7: Repeat the ceramic film coating operation and the internal electrode metal paste printing operation of step S6 until an intermediate structure film layer is formed; the intermediate structure film layer has multiple alternating layers of internal electrode patterns and ceramic films.

[0080] Specifically, the intermediate structure film layer includes multiple internal electrode patterns and multiple ceramic films, which are stacked alternately.

[0081] like Figure 2 As shown, multilayer internal electrode patterns 40 and multilayer ceramic films 50 are stacked alternately. Figure 3 A schematic diagram of the structure of the ceramic diaphragm 50 is shown. Figure 5 A schematic diagram of the structure of the ceramic diaphragm 50 and the internal electrode pattern 40 on its upper surface is shown.

[0082] Optionally, the thickness of the intermediate structure membrane layer is 200 μm to 250 μm.

[0083] Step S8: Stack another portion of the fiber-toughened composite ceramic films from the above plurality of fiber-toughened composite ceramic films in sequence to form a second driving film layer; and cover the upper surface of the intermediate structure film layer with the inner electrode pattern to obtain a green blank.

[0084] Optionally, the thickness of the second driving diaphragm layer is 120 μm to 150 μm.

[0085] Specifically, an automatic overprinting machine is used to obtain a blank block, that is, the automatic overprinting machine can perform the printing operation of internal electrode metal paste to obtain an internal electrode pattern.

[0086] Optionally, the internal electrode metal paste is a silver-palladium internal electrode paste. For example, the internal electrode metal paste is a 9010 silver-palladium internal electrode paste.

[0087] like Figure 2 As shown, the two driving diaphragm layers 60 are the first driving diaphragm layer and the second driving diaphragm layer, respectively. Figure 4 A schematic diagram of the structure of the fiber-toughened composite ceramic membrane 61 is shown. Figure 6 A schematic diagram of the structure of the fiber-toughened composite ceramic membrane 61 and the internal electrode pattern 40 on its surface is shown.

[0088] Step S9: Cut the blank block to obtain multiple bicrystalline blanks.

[0089] Specifically, a block cutting machine is used to cut the raw blank blocks.

[0090] Specifically, along the cutting line, the blank block is cut into multiple bi-crystal blanks.

[0091] Step S10: Heat-treat and apply external electrodes to multiple bicrystalline wafer blanks to obtain a piezoelectric ceramic bicrystalline wafer comprising a first driving layer 10, an intermediate structural layer 30, and a second driving layer 20. That is, the piezoelectric ceramic bicrystalline wafer is a toughened piezoelectric ceramic bicrystalline wafer.

[0092] In this application, the method for preparing multiple ceramic films includes: using a casting process to form multiple ceramic films from a piezoelectric ceramic slurry. Optionally, the piezoelectric ceramic slurry is PZT5H-L piezoelectric ceramic slurry.

[0093] Specifically, a casting machine is used to fabricate multiple ceramic films from the prepared piezoelectric ceramic slurry.

[0094] Specifically, the ceramic diaphragm is a piezoelectric ceramic diaphragm.

[0095] In this application, in step S2, the fiber-toughened composite ceramic material is made into a fiber-toughened composite ceramic film, that is, the ground fiber-toughened casting slurry is made into a fiber-toughened composite ceramic film.

[0096] Specifically, a casting machine is used to process the ground fiber-toughened casting slurry into fiber-toughened composite ceramic films.

[0097] Specifically, the fiber-toughened composite ceramic diaphragm is a fiber-toughened composite piezoelectric ceramic diaphragm.

[0098] In this application, step S8 further includes the following steps: performing stacking molding, vacuum sealing, and isostatic pressing on the obtained green blank block.

[0099] Specifically, the obtained preform blocks are first stacked and molded to obtain stacked preform blocks; then the stacked preform blocks are vacuum-sealed to obtain vacuum-sealed preform blocks; then the vacuum-sealed preform blocks are subjected to isostatic pressing to obtain isostatically pressed preform blocks.

[0100] Specifically, in step S9, the isostatically pressed blank block is cut to obtain multiple bicrystalline blanks.

[0101] Specifically, the unfinished blank is stacked and formed, that is, the unfinished blank is compressed in the thickness direction.

[0102] Specifically, the method for vacuum sealing the preform blocks includes: placing the preform blocks into a vacuum self-sealing bag, then evacuating and sealing them.

[0103] Specifically, when performing isostatic pressing on the green blank block, the isostatic pressing pressure is 300 bar to 700 bar, and the isostatic pressing holding time is 5 min to 20 min.

[0104] Specifically, an isostatic press is used to perform isostatic pressing on the green blank blocks.

[0105] In this application, the heat treatment in step S10 includes the steps of debinding and sintering.

[0106] Specifically, the process involves first removing the adhesive from multiple bicrystalline wafer blanks, then sintering the removed bicrystalline wafer blanks, and finally applying external electrodes to the sintered bicrystalline wafer blanks.

[0107] Specifically, a muffle furnace is used to perform debinding operations on multiple biwafer preforms.

[0108] Optionally, when performing the desizing step on multiple biwafer preforms, the desizing temperature is between 500°C and 700°C. For example, the desizing temperature is 650°C.

[0109] Specifically, a high-temperature furnace is used to sinter multiple bicrystalline wafer blanks, that is, high-temperature sintering is carried out in an atmospheric atmosphere.

[0110] Optionally, when performing the sintering step on multiple bicrystalline preforms, the sintering temperature is between 950°C and 1000°C. For example, the sintering temperature is 980°C. The piezoelectric ceramic powder used in this invention is a piezoelectric ceramic powder modified by low-temperature sintering.

[0111] The sintering temperature is lower than the melting point of the fiber-reinforced material to ensure that the fiber-reinforced material does not melt at the co-firing temperature and to ensure that the fiber-reinforced material does not react with the piezoelectric ceramic powder, or only reacts slightly.

[0112] In this application, the step of applying an external electrode to multiple biwafer blanks includes: printing an external electrode paste layer on each outer surface of each biwafer blank to form an external electrode pattern on each outer surface of each biwafer blank, thereby forming an external electrode layer on each outer surface of each biwafer blank. Each biwafer blank has two opposing outer surfaces along its thickness direction. Figure 7 A schematic diagram of the structure of the external electrode pattern 70 on the two outer surfaces of the biwafer blank is shown.

[0113] Specifically, the outer electrode pattern is sintered to form an outer electrode layer.

[0114] The present invention also provides a piezoelectric ceramic bicrystalline wafer, which is prepared by the above-described preparation method.

[0115] The piezoelectric ceramic bicrystalline wafer in this application is a co-fired piezoelectric ceramic bicrystalline wafer.

[0116] In this application, as Figure 1 As shown, the piezoelectric ceramic bicrystalline wafer includes a first driving layer 10, an intermediate structural layer 30, and a second driving layer 20 stacked sequentially in the vertical direction. The first driving film layer is sintered to form the first driving layer 10 of the piezoelectric ceramic bicrystalline wafer, the second driving film layer is sintered to form the second driving layer 20 of the piezoelectric ceramic bicrystalline wafer, and the intermediate structural film layer is sintered to form the intermediate structural layer 30 of the piezoelectric ceramic bicrystalline wafer.

[0117] Both the first driving layer 10 and the second driving layer 20 are toughened driving layers.

[0118] The first driving layer 10 and the second driving layer 20 both include multiple stacked fiber-toughened composite ceramic media layers; each fiber-toughened composite ceramic media layer is formed by a fiber-toughened composite ceramic membrane, that is, the fiber-toughened composite ceramic membrane is sintered to form the fiber-toughened composite ceramic media layer.

[0119] The intermediate structural layer 30 includes multiple ceramic dielectric layers and multiple internal electrode layers, and the multiple ceramic dielectric layers and multiple internal electrode layers are arranged alternately in a stacked manner; each ceramic dielectric layer is formed by a ceramic film, that is, the ceramic dielectric layer is formed after the ceramic film is sintered; each internal electrode layer is formed by an internal electrode pattern, that is, the internal electrode pattern is formed after the internal electrode pattern is sintered.

[0120] An inner electrode layer is provided between the first driving layer 10 and the intermediate structural layer 30, and an inner electrode layer is provided between the second driving layer 20 and the intermediate structural layer 30.

[0121] External electrode layers are provided on the outer surface of the first driving layer 10 and the outer surface of the second driving layer 20. The outer surface of the first driving layer 10 refers to the surface of the first driving layer 10 that is away from the intermediate structural layer 30, and the outer surface of the second driving layer 20 refers to the surface of the second driving layer 20 that is away from the intermediate structural layer 30.

[0122] Figure 8 A schematic diagram of the actuation of the piezoelectric ceramic bicrystalline wafer of this application is shown. The first driving layer 10 and the second driving layer 20 have the same polarization direction, and the intermediate structural layer 30 is a passive structural layer. The upper surface of the first driving layer 10 and the lower surface of the second driving layer 20 are positive electrodes, receiving a positive bias voltage; the intermediate structural layer 30 is connected to the lower surface of the first driving layer 10 and the upper surface of the second driving layer 20, respectively, serving as a negative electrode (0V) or ground. Thus, the first driving layer 10 becomes thicker in the thickness direction and shorter in the length direction, causing the bicrystalline wafer to tilt upwards, resulting in upward displacement. The second driving layer 20, due to receiving a voltage opposite to its polarization, becomes thinner in the thickness direction and longer in the length direction, further causing the bicrystalline wafer to tilt upwards, increasing the upward displacement. Since the first driving layer 10 and the second driving layer 20 exert force simultaneously, a larger displacement can be obtained with a relatively small input voltage.

[0123] A pneumatic valve is driven by the piezoelectric ceramic bicrystalline wafer of this application.

[0124] In this application, a two-point test method is used to test the bending strength of the bicrystalline wafer. For example... Figure 9 As shown, the dual-chip test 93 is placed on two bottom supports 91, which form two bottom fulcrums for the dual-chip test 93; a thrust test probe 92 is used to apply force to the dual-chip test 93 from above.

[0125] In Tables 1 through 3 below, the size of the tested bicrystalline wafers is 25 mm. 8mm 0.48mm.

[0126] Table 1

[0127]

[0128] The toughened bicrystalline wafers in Table 1 are toughened co-fired bicrystalline wafers prepared by doping zirconium oxide fibers of different contents and lengths.

[0129] As shown in Table 1, the higher the amount of zirconia fiber added, the greater the thrust and flexural strength of the bicrystalline wafer, but the lower the electrical properties and lifespan. If the amount added is too small, the zirconia fiber will be absorbed and reacted by the ceramic, failing to provide a toughening effect. Therefore, for 5μm long zirconia fibers, an addition amount of about 5% is appropriate.

[0130] Compared to PS11010-11L bicrystalline wafers and untoughened co-fired bicrystalline wafers, this invention, by doping the driving layer with a small amount of zirconia fiber, can significantly improve the resisting force and bending and fracture resistance of the bicrystalline wafers while maintaining the same displacement. However, excessive addition of zirconia fiber can cause fiber agglomeration, leading to stress concentration and becoming the source of fracture, resulting in a significant decrease in displacement and resisting force. Therefore, the length of the zirconia fiber should be controlled between 5μm and 10μm, and the content should be controlled between 3% and 8%. Too long, too many, or too few fibers will also reduce the toughening effect due to the entanglement of the fibers.

[0131] Optionally, when the fiber toughening material is zirconia fiber, the length of the zirconia fiber is 5 μm to 15 μm, and the weight ratio of zirconia fiber to piezoelectric ceramic slurry is 1% to 10%.

[0132] Optionally, when the fiber toughening material is zirconia fiber, the length of the zirconia fiber is 5 μm to 10 μm, and the weight ratio of zirconia fiber to piezoelectric ceramic slurry is 3% to 8%.

[0133] Table 2

[0134]

[0135] The toughened bicrystalline wafers in Table 2 are toughened co-fired bicrystalline wafers prepared by doping glass fibers of different contents and lengths.

[0136] As shown in Table 2, glass fiber toughening mainly stems from the transformation of the tetragonal phase to the monoclinic phase under stress, accompanied by volume changes to suppress crack propagation. Glass fibers primarily form a fiber support network in the ceramic layer to disperse stress. Because glass fiber-toughened bicrystalline wafers exhibit higher toughness, they have longer high-frequency service life and greater displacement. While glass fiber-toughened bicrystalline wafers show higher strength, they are more prone to plastic cracking and further propagation during long-term cyclic use, leading to a reduced service life. For glass fibers with a length of 5μm to 15μm, an addition amount of 1% to 5% is suitable.

[0137] Compared to PS11010-11L bicrystalline wafers and untoughened co-fired bicrystalline wafers, this invention, by doping the driving layer with a small amount of glass fiber, can significantly improve the resisting force and bending and fracture resistance of the bicrystalline wafers while maintaining the same displacement. However, excessive addition of glass fiber will cause fiber agglomeration, leading to stress concentration and becoming the source of fracture, resulting in a significant decrease in displacement and resisting force. Therefore, the length of the glass fiber should be controlled between 5μm and 15μm, and the addition amount should be controlled between 1% and 5% to ensure the basic toughness of the driving layer.

[0138] Optionally, when the fiber toughening material is glass fiber, the length of the glass fiber is 5 μm to 15 μm, and the weight ratio of glass fiber to piezoelectric ceramic slurry is 1% to 10%.

[0139] Optionally, when the fiber toughening material is glass fiber, the length of the glass fiber is 5 μm to 15 μm, and the weight ratio of glass fiber to piezoelectric ceramic slurry is 1% to 5%.

[0140] Table 3

[0141]

[0142] The toughened bicrystalline wafers in Table 3 are toughened co-fired bicrystalline wafers prepared by doping with needle-shaped wollastonite fibers of different contents and lengths.

[0143] As shown in Table 3, the toughening mechanism of acicular wollastonite mainly relies on physical interlocking effects such as fiber pull-out and crack deflection. Its addition to the driving layer has little impact on the matrix strength of the driving layer, and may even weaken it to some extent. Therefore, it can increase the toughness of the bicrystalline wafers, thereby improving their service life. However, due to the significant anisotropy of acicular wollastonite, its toughening effect depends on the fiber orientation and dispersion in the driving layer. Therefore, its modification of the driving layer's toughness is limited, and the reduction in the driving layer's flexural strength leads to a decrease in resistive force.

[0144] Compared to PS11010-11L bicrystalline wafers and untoughened co-fired bicrystalline wafers, this invention, by doping the driving layer with a small amount of needle-like wollastonite fibers, maintains the displacement while keeping the bicrystalline wafer's resistivity and resistance to bending and fracture essentially unchanged or only slightly reduced. Excessive addition of needle-like wollastonite can cause fiber agglomeration, leading to stress concentration and becoming a fracture source, resulting in a significant decrease in displacement and resistivity. Therefore, the content of needle-like wollastonite fibers should be controlled between 1% and 5%, with a length controlled within 10 μm, to ensure that the resistivity of the bicrystalline wafer is not too low.

[0145] Optionally, when the fiber toughening material is acicular wollastonite fiber, the length of the acicular wollastonite fiber is 5 μm to 15 μm, and the weight ratio of the acicular wollastonite fiber to the piezoelectric ceramic slurry is 1% to 10%.

[0146] Optionally, when the fiber toughening material is acicular wollastonite fiber, the length of the acicular wollastonite fiber is less than or equal to 10 μm, and the weight ratio of the acicular wollastonite fiber to the piezoelectric ceramic slurry is 1% to 5%.

[0147] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0148] The piezoelectric ceramic bicrystalline wafer of this application enhances the toughness and bending strength of the two driving layers by adding fiber material to the driving layers on both sides.

[0149] The piezoelectric ceramic bilayer of this application significantly enhances the toughness of the outer driving layer, increases its service life, and improves the displacement.

[0150] The piezoelectric ceramic bicrystalline wafer of this application has the characteristics of simple fabrication process, large displacement, large thrust, long life and low driving voltage.

[0151] The piezoelectric ceramic bicrystalline wafer fabrication method of this application avoids the direct fabrication of ultrathin ceramic sheets, that is, it eliminates the need to obtain ultrathin ceramic sheets through grinding, thus avoiding damage to the ceramic sheets during grinding and assembly; it significantly improves the yield and reduces the process cost.

[0152] The piezoelectric ceramic bicrystalline wafer of this application combines high rigidity and strong toughness. When faced with high pressure, the valve closure performance is better than that of carbon fiber bicrystalline wafers.

[0153] This application utilizes toughened driving layers on both sides, improving the overall stiffness and displacement of the piezoelectric ceramic bilayer. Gas valves using this piezoelectric ceramic bilayer effectively avoid air leakage problems caused by the valve's inability to completely close the inlet under high pressure, as well as inaccurate flow control issues.

[0154] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0155] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0156] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a piezoelectric ceramic bicrystalline wafer, characterized in that, include: Step S1: Obtain multiple ceramic membranes; Step S2: Obtain the fiber-toughened composite ceramic material and fabricate multiple fiber-toughened composite ceramic films using a casting process; wherein, the preparation method of the fiber-toughened composite ceramic material includes: preparing a predetermined amount of piezoelectric ceramic slurry; doping the piezoelectric ceramic slurry with a fiber-toughening material to obtain the fiber-toughened composite ceramic material; wherein, the fiber-toughening material is zirconia fiber, glass fiber, or needle-like wollastonite fiber; the weight ratio of the fiber-toughening material to the piezoelectric ceramic slurry is 1% to 10%; the length of the fiber-toughening material is 5 μm to 15 μm; Step S3: Stack a portion of the fiber-toughened composite ceramic membranes in sequence to form a first driving membrane layer; Step S4: Print an inner electrode metal paste on the upper surface of the first driving diaphragm layer to form an inner electrode pattern; Step S5: A ceramic film is coated onto the upper surface of the first driving diaphragm layer with the inner electrode pattern, and an inner electrode metal paste is printed on the upper surface of the coated ceramic film to form the inner electrode pattern. Step S6: Cover the upper surface of the ceramic film with the inner electrode pattern with another ceramic film, and print an inner electrode metal paste on the upper surface of the covered ceramic film to form an inner electrode pattern. Step S7: Repeat step S6 until an intermediate structure film layer with multiple alternating layers of internal electrode patterns and ceramic films is formed; Step S8: Stack another portion of the fiber-toughened composite ceramic films in sequence to form a second driving film layer; and cover the upper surface of the intermediate structure film layer with the inner electrode pattern to obtain a green blank. Step S9: Cut the blank block to obtain multiple bicrystalline blanks; Step S10: Heat treatment and external electrode application are performed on the multiple bicrystalline wafer blanks to finally obtain a piezoelectric ceramic bicrystalline wafer including a first driving layer (10), an intermediate structural layer (30) and a second driving layer (20).

2. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 1, characterized in that, In step S2, the length of the fiber-reinforced material is 5 μm to 10 μm.

3. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 1, characterized in that, In step S2, a ball mill is used to grind the piezoelectric ceramic slurry containing fiber-reinforced material. The grinding speed is 10 rpm to 50 rpm and the grinding time is 10 h to 24 h.

4. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 1, characterized in that, In step S8, the preparation method further includes: The raw blank is subjected to stacking, vacuum sealing, and isostatic pressing.

5. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 4, characterized in that, When performing the isostatic pressing step on the green blank block, the isostatic pressing pressure is 300 bar to 700 bar, and the isostatic pressing holding time is 5 min to 20 min.

6. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 1, characterized in that, The heat treatment includes the steps of debinding and sintering.

7. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 6, characterized in that, When performing the debinding step on the plurality of bicrystalline wafer blanks, the debinding temperature is 500°C to 700°C; when performing the sintering step on the plurality of bicrystalline wafer blanks, the sintering temperature is 950°C to 1000°C.

8. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 1, characterized in that, The thickness of the fiber-toughened composite ceramic membrane is 20 μm to 40 μm, and the thickness of the ceramic membrane is 20 μm to 40 μm.

9. The method for preparing a piezoelectric ceramic bicrystalline wafer according to claim 1, characterized in that, The thickness of the first driving diaphragm layer is 120 μm to 150 μm; the thickness of the second driving diaphragm layer is 120 μm to 150 μm; and the thickness of the intermediate structure diaphragm layer is 200 μm to 250 μm.

10. A piezoelectric ceramic bicrystalline wafer, characterized in that, The piezoelectric ceramic bicrystalline wafer is prepared by the method described in any one of claims 1-9, wherein the piezoelectric ceramic bicrystalline wafer comprises a first driving layer (10), an intermediate structural layer (30), and a second driving layer (20) stacked sequentially in the vertical direction. The first driving layer (10) and the second driving layer (20) each include multiple stacked fiber-toughened composite ceramic dielectric layers formed by fiber-toughened composite ceramic films; the intermediate structural layer (30) includes multiple ceramic dielectric layers formed by ceramic films and multiple inner electrode layers formed by inner electrode patterns, and the multiple ceramic dielectric layers and the multiple inner electrode layers are alternately stacked. An inner electrode layer is provided between the first driving layer (10) and the intermediate structure layer (30), and between the second driving layer (20) and the intermediate structure layer (30); Both the outer surfaces of the first driving layer (10) and the second driving layer (20) are provided with an outer electrode layer.

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