A bismuth ferrite-barium titanate textured piezoelectric ceramic and a preparation method thereof

Abstract

The application discloses a kind of bismuth ferrite-barium titanate textured piezoelectric ceramics and preparation method thereof, belong to ceramic preparation technical field, the preparation method includes: with (001) crystal direction BaTiO3 flaky microcrystal as template, with (1-x) BiFeO3-xBaTiO3 ceramic matrix powder is mixed, through casting process, matrix powder is grown along the template crystal direction, during, by controlling the amount of BaTiO3 flaky microcrystal, so that the volume ratio of it and ceramic matrix powder does not exceed 0.06, the thickness of casting film is 30~50 μm, and high-temperature sintering and high-temperature quenching mode with temperature up to 970 ℃~1040 ℃ is used, finally form textured BF-BT ceramic, the formed ceramic has good piezoelectric property and texture degree, and the above method process is simple, without adding additional material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic preparation, in particular to a BiFeO3-BaTiO3 textured piezoelectric ceramic and a preparation method thereof. BACKGROUND

[0002] BiFeO3-BaTiO3 (BF-BT) ceramic has high Curie temperature and good piezoelectric performance, and has become one of the most potential materials in the field of high-temperature piezoelectric ceramics. BF-BT ceramic exhibits more excellent piezoelectric performance along the (001) crystal direction, and texturing along the (001) crystal direction can effectively improve the piezoelectric performance of the ceramic without reducing the Curie temperature. At present, the Templated Grain Growth (TGG) method is used to make the template directional distribution in the ceramic matrix through the tape casting process, and the ceramic grains grow along the orientation of the (001) template, thereby improving the piezoelectric performance of the ceramic.

[0003] For example, patent CN115745597A "Method for preparing BiFeO3-BaTiO3 piezoelectric textured ceramic by cold sintering technology" discloses a BF-BT ceramic textured along the (001) crystal direction, which uses (001) crystal direction BaTiO3 flaky microcrystalline as a template, mixes with (1-x) BiFeO3-xBaTiO3 ceramic matrix powder, and grows the matrix powder along the template crystal direction through the tape casting process to form a textured BF-BT ceramic. During the preparation, a sintering process is involved, and the temperature directly affects the performance of the ceramic. If the temperature is too high, the template will react with the ceramic matrix, causing the template to disappear and the ceramic grains to be unable to grow along the template crystal phase, resulting in low or even no texture degree of the ceramic. Therefore, the patent emphasizes the use of cold sintering technology, and finally obtains a BF-BT ceramic with a piezoelectric coefficient of up to 210 pC / N and a texture degree of up to 62%.

[0004] However, the use of cold sintering technology requires the addition of auxiliary materials such as MnO2 and sintering aid Ba(OH)2·8H2O, which increases the consumption of materials. SUMMARY

[0005] In view of the above defects or improvement needs of the prior art, the present application provides a BiFeO3-BaTiO3 textured piezoelectric ceramic and a preparation method thereof, which aims to use high-temperature sintering to prepare a textured piezoelectric ceramic with excellent performance without the need for additional auxiliary materials.

[0006] To achieve the above-mentioned purpose, according to one aspect of the present application, a method for preparing a BiFeO3-BaTiO3 textured piezoelectric ceramic by using high-temperature sintering technology is provided, characterized in that it comprises:

[0007] Step S1: preparing BaTiO3 flaky templates with crystal orientation of (001) and ceramic matrix powder, wherein the ceramic matrix powder is obtained by ball milling pre-sintered powder of (1-x)BiFeO3-xBaTiO3;

[0008] Step S2: mixing the ceramic matrix powder with a dispersant and a solvent, ball stirring to obtain a mixed slurry, removing the ball, adding the BaTiO3 flaky templates to the mixed slurry, non-ball stirring, adding a binder and a plasticizer to the mixed slurry, non-ball stirring to obtain a casting slurry, wherein the volume ratio of the ceramic matrix powder to the BaTiO3 flaky templates ranges from 1: [0.02-0.06];

[0009] Step S3: defoaming the casting slurry;

[0010] Step S4: casting the defoamed casting slurry to obtain a casting film, and controlling the thickness of the casting film to be 30-50 μm;

[0011] Step S5: cutting the casting film into pieces, and then stacking and hot-pressing to obtain a green ceramic;

[0012] Step S6: cold isostatic pressing and degassing the green ceramic;

[0013] Step S7: high-temperature sintering the cold isostatic pressed green ceramic at a high temperature of 950-1040 °C for 3-16 h, and then high-temperature quenching to obtain a textured ceramic.

[0014] In one embodiment, the volume ratio of the ceramic matrix powder to the BaTiO3 flaky templates ranges from 1: [0.02-0.03].

[0015] In one embodiment, the high-temperature quenching is directly transferring the sintered product from a high-temperature environment to a room-temperature environment for quenching.

[0016] In one embodiment, in step S2, the solvent is ethanol and toluene, the dispersant is glycerol trioleate, the binder is polyvinyl butyral, the plasticizer is polyethylene glycol and butyl benzyl phthalate, and the mass ratio of the ceramic matrix powder: ethanol: toluene: glycerol trioleate: polyvinyl butyral: polyethylene glycol: butyl benzyl phthalate is 1:0.521:0.2:0.01:0.0125:0.005:0.005.

[0017] In one embodiment, in the pre-sintered powder of (1-x)BiFeO3-xBaTiO3, x=0.2-0.5.

[0018] In one embodiment, in step S6, the cold isostatic pressing and degassing operation includes:

[0019] The ceramic green body is cold isostatic pressed, then de-binding, and then cold isostatic pressed again. The de-binding process is to raise the temperature to 550-600℃ at a rate of 0.4-0.6℃ / min and keep for 2-3h. The pressure of the two cold isostatic pressing is 150-200MPa and the time is 5-10min.

[0020] In one of the embodiments, the operation process of preparing the BaTiO3 flaky template with the crystal direction of (001) in step S1 includes:

[0021] Step S11: Bi2O3 and TiO2 are mixed according to the reaction formula 2Bi2O3+3TiO2→Bi4Ti3O 12 , ball-milled with ethanol for 5-17h, then equal mass of KCl / NaCl with the molar ratio of 1:1 is added for further ball-milling, dried, sieved, and then put into a crucible and heated to 1025-1100℃ at a rate of 1-10℃ and kept for 1-4h, then repeatedly washed with hot deionized water to remove the salt, to obtain Bi4Ti3O 12 precursor;

[0022] Step S12: Bi4Ti3O 12 precursor is mixed with TiO2 and BaCO3 according to the reaction formula Bi4Ti3O 12 +BaCO3+TiO2→BaBi4Ti4O 15 +CO2, ball-milled with ethanol, then equal mass of KCl / BaCl2·2H2O with the molar ratio of 1:1 is added for further ball-milling, dried, sieved, and then kept at 1050℃ for 2-3h, then repeatedly washed with hot deionized water to remove the salt, to obtain BaBi4Ti4O 15 precursor;

[0023] Step S13: BaBi4Ti4O 15 precursor is mixed with BaCO3 according to the molar ratio of 1:4, then uniformly stirred with KCl / NaCl with the molar ratio of 1:1 in ethanol, dried, and then kept at 900-950℃ for 3-4h, then repeatedly washed with hot deionized water to remove the salt, then repeatedly washed with dilute nitric acid to remove Bi2O3 and BaO, and finally washed with deionized water to obtain the BaTiO3 flaky template with the crystal direction of (001).

[0024] In one of the embodiments, the operation process of preparing the ceramic matrix powder in step S1 includes:

[0025] Bi2O3, Fe2O3, TiO2, BaCO3 powder is weighed according to (1-x) BiFeO3-xBaTiO3 stoichiometry, then added to anhydrous ethanol for first ball milling to obtain a slurry, the slurry is dried and then calcined to prepare (1-x) BiFeO3-xBaTiO3 pre-fired powder, and then the pre-fired powder is subjected to second ball milling to obtain ceramic matrix powder.

[0026] In one of the embodiments, the method further comprises:

[0027] Step S8: grinding the textured ceramic surface and applying conductive silver paste on the upper and lower surfaces thereof;

[0028] Step S9: calcining the textured ceramic coated with the conductive silver paste and then polarizing.

[0029] According to another aspect of the present application, a BiFeO3-BaTiO3 textured piezoelectric ceramic is provided, which is prepared by the above method.

[0030] Overall, compared with the prior art, the above technical solution conceived by the present application can achieve the following beneficial effects:

[0031] The present application provides a method for preparing a BiFeO3-BaTiO3 textured piezoelectric ceramic, which uses (001) crystal direction BaTiO3 flaky microcrystal as a template, mixes it with (1-x) BiFeO3-xBaTiO3 ceramic matrix powder, and grows the matrix powder along the template crystal direction through a casting process. During the process, the volume ratio of BaTiO3 flaky microcrystal to ceramic matrix powder is controlled to be not more than 0.06, the casting film thickness is 30-50 μm, and high-temperature sintering and high-temperature quenching at a temperature as high as 970-1040 °C are used, finally forming a textured BF-BT ceramic. The formed ceramic has good piezoelectric properties and texture degree, and the above method is simple and does not require the addition of additional materials.

[0032] Further, controlling the volume ratio of the ceramic matrix powder to the BaTiO3 flaky template in the range of 1: [0.02-0.03] can obtain a relatively higher piezoelectric coefficient and texture degree, and its performance is much better than that of the BiFeO3-BaTiO3 textured piezoelectric ceramic prepared by the prior art.

[0033] Further, the (1-x) BiFeO3-xBaTiO3 pre-fired powder is configured according to x=0.2-0.5, and the ceramic in this range obtains optimal piezoelectric properties near the morphotropic phase boundary.

[0034] Further, in step S6, the ceramic green body is cold isostatic pressed, then degassing is performed, and after degassing, cold isostatic pressing is performed again, so that residual pores in the sample are removed, the sample is densified, and the large-size sheet-shaped template and the fine powder grains of the matrix are combined more closely, which is beneficial to the formation of the texture. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A step flow chart for preparing the BiFeO3-BaTiO3 textured piezoelectric ceramic by using high-temperature sintering technology in an embodiment of the present application;

[0036] Figure 2 An XRD image of the BaTiO3 sheet-shaped template in an embodiment of the present application;

[0037] Figure 3 An SEM image of the BaTiO3 sheet-shaped template in an embodiment of the present application;

[0038] Figure 4 A cross-sectional SEM image of the BaTiO3 sheet-shaped template textured BF-BT ceramic in an embodiment of the present application;

[0039] Figure 5 An XRD image of a textured sample with a template content of 0.03 and a sintering temperature of 970°C in the present application. DETAILED DESCRIPTION

[0040] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0041] As Figure 1 A step flow chart for preparing the BiFeO3-BaTiO3 textured piezoelectric ceramic by using high-temperature sintering technology in an embodiment of the present application is shown in the figure, which mainly includes the following steps:

[0042] Step S1: preparing a BaTiO3 sheet-shaped template with a crystal direction of (001) and a ceramic matrix powder, wherein the ceramic matrix powder is obtained by ball milling (1-x) BiFeO3-xBaTiO3 pre-sintered powder.

[0043] Specifically, the BaTiO3 sheet-shaped template with a crystal direction of (001) can be prepared by the following operations:

[0044] Step S11, Bi2O3 and TiO2 are mixed according to the reaction formula 2Bi2O3+3TiO2→Bi4Ti3O 12Bi4Ti3O 12 precursor;

[0045] Step S12, the Bi4Ti3O 12 precursor and TiO2, BaCO3 are mixed according to the reaction formula Bi4Ti3O 12 + BaCO3 + TiO2→ BaBi4Ti4O 15 + CO2, and then ethanol ball milling is performed for 5h, and then equal mass of KCl / BaCl2·2H2O with a molar ratio of 1:1 is added for further ball milling for 5h, and after drying and sieving, heat treatment is performed at 1050℃ for 3h, and then hot deionized water is repeatedly used to clean the salt to obtain BaBi4Ti4O 15 precursor;

[0046] Step S13, the BaBi4Ti4O 15 precursor and BaCO3 are mixed according to a molar ratio of 1:4, and in order to make the BaBi4Ti4O 15 fully react, BaCO3 is appropriately excessive, and then KCl / NaCl with a molar ratio of 1:1 (wherein the mass ratio of the salt and the powder is (0.5-3):1) is uniformly stirred in ethanol, and the reaction formula is BaBi4Ti4O 15 + 3BaCO3→ 4BaTiO3+ 2Bi2O3+ 3CO2, and after drying, heat treatment is performed at 970℃ for 3-4h, and then hot deionized water is repeatedly used to clean the salt, and then dilute nitric acid with a concentration of 1mol / L is repeatedly used to clean Bi2O3 and BaO, and finally deionized water is used to clean to obtain BaTiO3 flaky microcrystals with a crystal direction of (001).

[0047] Specifically, the ceramic matrix powder can be prepared by the following operations:

[0048] After Bi2O3, Fe2O3, TiO2, and BaCO3 powder are weighed according to the stoichiometry of (1-x)BiFeO3-xBaTiO3 (x=0.2-0.5), the first ball milling is performed in anhydrous ethanol to obtain a slurry, the slurry is dried and sieved through an 80-mesh sieve, and then (1-x)BiFeO3-xBaTiO3 (x=0.2-0.5) pre-fired powder is prepared by calcination, and then the pre-fired powder is subjected to second ball milling to obtain the ceramic matrix powder.

[0049] Specifically, the grinding balls used in the ball milling are zirconium balls, the rotation speed of the ball mill is 365 r / min, and the ball milling time is 12-24 h.

[0050] Specifically, the slurry obtained by the first ball milling is dried by an oven and then calcined at 800 ℃ for 6 h to prepare the (1-x)BiFeO3-xBaTiO3 pre-sintered powder. In an embodiment, x = 0.2-0.5, and the ceramic in this range achieves the optimal piezoelectric performance near the morphotropic phase boundary.

[0051] In step S2, the ceramic matrix powder is mixed with a dispersant and a solvent, ball stirring is performed to obtain a mixed slurry, the balls are removed, BaTiO3 flaky templates are added to the mixed slurry, non-ball stirring is performed, a binder and a plasticizer are added to the mixed slurry, non-ball stirring is performed to obtain a casting slurry, and the volume ratio of the ceramic matrix powder to the BaTiO3 flaky templates ranges from 1: [0.02-0.06].

[0052] Specifically, the solvent is ethanol and toluene, the dispersant is glycerol trioleate, the binder is polyvinyl butyral, the plasticizer is polyethylene glycol and butyl benzyl phthalate, and the mass ratio of the ceramic matrix powder: anhydrous ethanol: toluene: glycerol trioleate: polyvinyl butyral: polyethylene glycol: butyl benzyl phthalate is 1: (0.3-0.7): (0.1-0.3): (0.001-0.02): (0.005-0.02): (0.001-0.01): (0.001-0.01).

[0053] It can be understood that the auxiliary agents are not necessarily limited to the above examples. For example, the solvent can also be butanone, the dispersant can also be corn oil, the binder can also be polyvinyl alcohol or polyacrylic acid, and the plasticizer can also be dibutyl phthalate.

[0054] It should be noted that in this step, the ball stirring is changed to non-ball stirring during and after the addition of the BaTiO3 flaky templates, and the non-ball stirring can reduce the damage to the structure of the BaTiO3 flaky templates.

[0055] Specifically, step S2 is performed in a stirring defoaming machine, the ball stirring time is 45 minutes, the first non-ball stirring time is 5 minutes, and the second non-ball stirring time is 15 minutes.

[0056] Meanwhile, the application emphasizes that the volume ratio of the ceramic matrix powder to the BaTiO3 flaky template is in the range of 1:[0.02-0.06]. Under the conventional high-temperature sintering, too much BaTiO3 flaky template will reduce the Curie temperature and depolarization temperature. The application finds through experiments that, by controlling the amount of the BaTiO3 flaky template and adding no more than 0.06 of the BaTiO3 flaky template, and by cooperating with subsequent high-temperature quenching, the textured BF-BT ceramic can be obtained, and the piezoelectric coefficient is good.

[0057] Step S3: defoaming treatment is performed on the casting slurry.

[0058] Specifically, the vacuum defoaming time is 5-7 minutes.

[0059] Step S4: the defoamed casting slurry is cast to obtain a casting film, and the thickness of the casting film is controlled to be 30-50 microns.

[0060] Specifically, the casting slurry is cast on a casting machine by a doctor blade with a thickness of 100-250 microns, the casting speed is 0.5 cm / s-1.5 cm / s, the thickness of the casting film is 30-50 microns, the casting film is too thin to be easily formed, and the BaTiO3 flaky template is difficult to be horizontally laid in the casting film, and the arrangement is irregular, resulting in a low texture degree.

[0061] Step S5: the casting film is cut into pieces, and then is laminated and hot-pressed to obtain a ceramic green body.

[0062] Specifically, the ceramic green body obtained by cutting, laminating and hot-pressing has a size of 10x10x1 mm.

[0063] Step S6: cold isostatic pressing and degassing are performed on the ceramic green body.

[0064] Specifically, the ceramic green body is cold isostatic pressed, and then is degassed, and after degassing, the ceramic green body is cold isostatic pressed again, the degassing process is to increase the temperature to 550-600 DEG C at a temperature increasing rate of 0.4-0.6 DEG C / min and then to keep the temperature for 2-3 hours, the pressure of the two times of cold isostatic pressing is 150-200 MPa, and the time is 5-10 minutes. Through the two times of cold isostatic pressing before and after degassing, the residual pores in the sample can be removed, the sample is more dense, and the large-size flaky template and the matrix fine powder grains can be combined more closely, which is beneficial to the formation of texture.

[0065] Step S7: the ceramic green body after cold isostatic pressing is high-temperature sintered at 970-1040 DEG C for 3-16 hours, and then is high-temperature quenched to obtain a textured ceramic.

[0066] Specifically, after high-temperature sintering, the sample is directly moved from the high-temperature environment to the room-temperature air to realize high-temperature quenching. It is found through experiments that the ceramic can maintain good texture degree and piezoelectric coefficient after high-temperature quenching.

[0067] In an embodiment, the preparation method further comprises:

[0068] Step S8: polishing the textured ceramic surface and coating conductive silver paste on the upper and lower surfaces thereof.

[0069] Step S9: performing polarization after calcination treatment of the textured ceramic coated with the conductive silver paste.

[0070] Specifically, in step S8, the textured ceramic is polished to a thickness of 0.5 mm, the conductive silver paste is high-temperature silver paste, and the ceramic surface is coated with the paste through an 8*8 mm square screen.

[0071] Specifically, in step S9, the silver calcination conditions include a calcination temperature of 850℃ and a holding time of 30 minutes; and the polarization conditions include a polarization temperature of 80℃, a polarization voltage of 4kV / mm, and a polarization time of 15 minutes.

[0072] In summary, the bismuth ferrite-barium titanate textured piezoelectric ceramic is prepared through the above steps, the (001) crystal direction BaTiO3 flaky microcrystal is used as a template, mixed with (1-x) BiFeO3-xBaTiO3 ceramic matrix powder, the matrix powder is grown along the template crystal direction through a casting process, during which, the amount of BaTiO3 flaky microcrystal is controlled so that the volume ratio of the BaTiO3 flaky microcrystal to the ceramic matrix powder is not more than 0.06, and high-temperature sintering and high-temperature quenching are used to finally form the textured BF-BT ceramic. The formed ceramic has good piezoelectric performance and texture degree, and the above method is simple and does not need to add additional materials.

[0073] Correspondingly, the application also relates to a bismuth ferrite-barium titanate textured piezoelectric ceramic prepared through the above method.

[0074] Hereinafter, specific embodiments are described.

[0075] Embodiment 1

[0076] a. Preparation of BaTiO3 flaky template

[0077] Bi2O3 and TiO2 are mixed according to a molar ratio of 2:3, ball-milled for 5-17h at a speed of 365r / min, then equal mass of KCl / NaCl with a molar ratio of 1:1 is added and ball-milled for 5h, dried, sieved and then put into a crucible and heated at a rate of 1-10℃ to 1025-1100℃ for 1-4h, then repeatedly washed with hot deionized water to remove the salt, to obtain Bi4Ti3O 12 precursor.

[0078] Bi4Ti3O 12 The precursor is mixed with TiO2 and BaCO3 in a molar ratio of 1:1:1, ball-milled in ethanol for 5 h, and then KCl / BaCl2·2H2O in a molar ratio of 1:1 is added in an equal amount, and the ball-milling is continued for 5 h. After drying and sieving, the mixture is heated at 1050°C for 3 h, and then repeatedly washed with hot deionized water to remove the salt, to obtain BaBi4Ti4O 15 precursor.

[0079] BaBi4Ti4O 15 The precursor is mixed with BaCO3 in a molar ratio of 1:4, and then KCl / NaCl in a molar ratio of 1:1 is added, and the mixture is gently stirred in ethanol until uniform, and then dried and heated at 970°C for 3-4 h. The salt is removed by repeatedly washing with hot deionized water, and then Bi2O3 and BaO are removed by repeatedly washing with dilute nitric acid with a concentration of 1 mol / L, and finally the product is washed with deionized water to obtain BaTiO3 flaky microcrystals.

[0080] The XRD image of the BaTiO3 flaky template is shown in Figure 2 The SEM image of the BaTiO3 flaky template is shown in Figure 3 The diameter-thickness ratio is 7-10.

[0081] b. Preparation of ceramic matrix powder

[0082] Bi2O3, Fe2O3, TiO2 and BaCO3 powders are weighed according to the stoichiometry of (1-x)BiFeO3-xBaTiO3, and then added to anhydrous ethanol for first ball-milling to obtain a slurry. After drying in an oven and sieving through an 80-mesh sieve, the slurry is calcined at 800°C for 6 h to prepare (1-x)BiFeO3-xBaTiO3 pre-fired powder. The pre-fired powder is then subjected to second ball-milling to obtain ceramic matrix powder. The ball-milling is performed using zirconium balls at a speed of 365 r / min for 12-24 h.

[0083] Example 2

[0084] The ceramic matrix powder obtained in Example 1 was mixed with glycerol trioleate, ethanol and toluene, and stirred in a ball stirring deaerator for 45 minutes, then the ball was removed, and BaTiO3 flaky template obtained in Example 1 was added into the mixed slurry, the volume ratio of BaTiO3 flaky template to ceramic matrix powder was 0.02. The mixed slurry was stirred in the ball stirring deaerator for 5 minutes, then polyvinyl butyral, polyethylene glycol and butyl benzyl phthalate were added into the mixed slurry, and stirred for 15 minutes to obtain a casting slurry. The mass ratio of ceramic matrix powder: anhydrous ethanol: toluene: glycerol trioleate: polyvinyl butyral: polyethylene glycol: butyl benzyl phthalate was 1:0.521:0.2:0.01:0.0125:0.005:0.005.

[0085] The casting slurry was placed in a vacuum deaerator for deaeration treatment for 5 minutes.

[0086] The casting slurry was cast on a casting machine by a doctor blade with a gap of 100-250 μm to obtain a casting film, the casting speed was 0.5 cm / s-1.5 cm / s, and the thickness of the casting film was 30-50 μm.

[0087] The casting film was cut into square pieces, and then stacked and hot-pressed to obtain a green ceramic body with a size of 10×10×1 mm.

[0088] The green ceramic body was cold isostatic pressed, then degreased, and then cold isostatic pressed again. The degreasing process was performed at a temperature increasing rate of 0.5 ℃ / min, and the degreasing temperature was 550-600 ℃, and the degreasing time was 2-3 h. The cold isostatic pressing pressure was 150-200 MPa, and the time was 5 min.

[0089] The cold isostatic pressed green ceramic body was heat treated at 970 ℃, 1020 ℃ and 1040 ℃ for 3-16 h, and then quenched to obtain a textured ceramic.

[0090] The thickness of the textured ceramic was polished to 0.5 mm, and conductive silver paste was high-temperature silver paste, which was coated on the surface of the ceramic through an 8×8 mm square screen.

[0091] The textured ceramic coated with conductive silver paste was calcined and then polarized, the calcination temperature was 850 ℃, and the holding time was 30 min. The polarization conditions included: the polarization temperature was 80 ℃, the polarization voltage was 4 kV / mm, and the polarization time was 15 min.

[0092] Example 3

[0093] The preparation process of this example was the same as that of Example 2, except that the volume ratio of BaTiO3 flaky template to ceramic matrix powder was 0.03.

[0094] Example 4

[0095] The preparation process of this example is the same as that of example 2, except that the volume ratio of BaTiO3 sheet-shaped template to ceramic base powder is 0.05.

[0096] Example 5

[0097] The preparation process of this example is the same as that of example 2, except that the volume ratio of BaTiO3 sheet-shaped template to ceramic base powder is 0.06.

[0098] The properties of the ceramics obtained in examples 2 to 5 are tested.

[0099] As shown in Fig. 1, the cross-sectional SEM image of the BiFeO3-BaTiO3 textured piezoelectric ceramic shows that the BaTiO3 sheet-shaped template exists obviously, proving that the ceramic grains grow along the crystal around the BaTiO3 sheet-shaped template. Figure 4 As shown in Table 1, the piezoelectric coefficients of the ceramics in examples 2 to 5 are as follows, and as shown in Table 2, the texture degrees of the ceramics in examples 2 to 5 are as follows.

[0100] Table 1 Piezoelectric coefficients of each example

[0101] Table 2 Texture degrees of each example

[0102] As can be seen from Table 1, the piezoelectric coefficients of all the ceramic samples exceed 210 pC / N. As can be seen from Table 2, the texture degrees of all the ceramic samples exceed 59%. That is, the ceramic prepared by the above preparation method has good piezoelectric coefficient and texture degree. In combination of Table 1 and Table 2, when the volume ratio of BaTiO3 sheet-shaped template to ceramic base powder is 0.03 and the sintering temperature is 970°C, the texture degree is as high as nearly 80% (as shown in Fig. 2), the piezoelectric coefficient exceeds 260 pC / N, and the performance is very excellent.

[0103] Figure 5

[0104] Those skilled in the art will easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.​​

Claims

1. A method for fabricating a BiFeO3-BaTiO3 textured piezoelectric ceramic using a high-temperature sintering technique, characterized in that, The method comprises the following steps: Step S1: preparing BaTiO3 flaky templates with a crystal direction of (001) and ceramic matrix powder, wherein the ceramic matrix powder is obtained by ball milling pre-fired powder of (1-x)BiFeO3-xBaTiO3; Step S2: mixing the ceramic matrix powder with a dispersant and a solvent, stirring with balls to obtain mixed slurry, removing the balls, adding the BaTiO3 flaky templates to the mixed slurry, stirring without balls, adding a binder and a plasticizer to the mixed slurry, and stirring without balls to obtain a casting slurry, wherein the volume ratio of the ceramic matrix powder to the BaTiO3 flaky templates ranges from 1:0.02 to 1:0.06; Step S3: performing defoaming treatment on the casting slurry; Step S4: casting the defoamed casting slurry to obtain a casting film, and controlling the thickness of the casting film to be 30-50 μm; Step S5: cutting the casting film into pieces, and then performing lamination and hot pressing to obtain a green ceramic body; Step S6: performing cold isostatic pressing and degassing on the green ceramic body; Step S7: performing high-temperature sintering on the green ceramic body at a high temperature of 950-1040 °C for 3-16 hours, and then performing high-temperature quenching to make the ceramic matrix powder grow along the template crystal direction to obtain a textured ceramic with (001) crystal direction texture; wherein the high-temperature quenching is performed by directly transferring the sintered product from a high-temperature environment to a room-temperature environment.

2. The method of producing a BiFe03-BaTi04 textured piezoelectric ceramic according to claim 1, wherein The volume ratio of the ceramic matrix powder to the BaTiO3 flaky templates ranges from 1:0.02 to 1:0.

03.

3. The method of claim 1, wherein the BiFeO3-BaTiO3 textured piezoelectric ceramic is prepared by the steps of: In step S2, ethanol and toluene are used as the solvent, glyceryl trioleate is used as the dispersant, polyvinyl butyral is used as the binder, and polyethylene glycol and butyl benzyl phthalate are used as the plasticizer, and the mass ratio of the ceramic matrix powder:ethanol:toluene:glyceryl trioleate:polyvinyl butyral:polyethylene glycol:butyl benzyl phthalate is 1:0.521:0.2:0.01:0.0125:0.005:0.

005. In the pre-fired powder of (1-x)BiFeO3-xBaTiO3, x=0.2-0.

5.

4. The method for preparing bismuth ferrite-barium titanate textured piezoelectric ceramics as described in claim 1, characterized in that, In step S6, the cold isostatic pressing and degassing operation comprises:

5. The method for preparing bismuth ferrite-barium titanate textured piezoelectric ceramics as described in claim 1, characterized in that, The green ceramic body is cold isostatically pressed, then degassed, cold isostatically pressed again, and degassed, the degassing process is performed at a temperature increasing rate of 0.4-0.6 °C / min to a temperature of 550-600 °C and then kept for 2-3 hours, the pressure of the two cold isostatic pressing processes is 150-200 MPa, and the time is 5-10 minutes. In step S1, the operation process of preparing the BaTiO3 flaky templates with a crystal direction of (001) comprises:

6. The method for preparing bismuth ferrite-barium titanate textured piezoelectric ceramics as described in claim 1, characterized in that, In step S1, the operation process of preparing the ceramic matrix powder comprises: Step S11: Bi2O3 and TiO2 are mixed in a ratio according to the reaction formula 2Bi2O3+3TiO2→Bi4Ti3O 12 , ball-milled with ethanol for 5h~17h, then equal mass of KCl / NaCl with a molar ratio of 1:1 is added for further ball-milling, dried, sieved, and then put into a crucible, heated at a rate of 1℃~10℃ to 1025℃~1100℃ for 1h~4h, and then repeatedly washed with hot deionized water to remove the salt, to obtain Bi4Ti3O 12 precursor; Step S12: Bi4Ti3O 12 The precursor is mixed with TiO2 and BaCO3 in a molar ratio according to the reaction formula Bi4Ti3O 12 + BaCO3 + TiO2 → BaBi4Ti4O 15 + CO2, ball-milled with ethanol, and then an equal mass of KCl / BaCl2·2H2O with a molar ratio of 1:1 is added for continuous ball-milling. After drying and sieving, the mixture is kept at 1050°C for 2-3 hours, and then repeatedly washed with hot deionized water to remove the salt, to obtain BaBi4Ti4O 15 precursor; Step S13: BaBi4Ti4O 15 The precursor is mixed with BaCO3 in a molar ratio of 1:4, and then is uniformly stirred with KCl / NaCl in a molar ratio of 1:1 in ethanol. After drying, the mixture is kept at 900-950°C for 3-4h. The salt is removed by repeatedly washing with hot deionized water, and Bi2O3 and BaO are removed by repeatedly washing with dilute nitric acid. Finally, the BaTiO3 flaky template with a crystal direction of (001) is obtained by washing with deionized water.

7. The method of producing a BiFe03-BaTi04 textured piezoelectric ceramic according to claim 1, wherein The Bi2O3, Fe2O3, TiO2 and BaCO3 powders are weighed according to the stoichiometry of (1-x)BiFeO3-xBaTiO3, added to anhydrous ethanol for first ball milling to obtain slurry, the slurry is dried and calcined to prepare the pre-fired powder of (1-x)BiFeO3-xBaTiO3, and then the pre-fired powder is subjected to second ball milling to obtain the ceramic matrix powder. The method further comprises:

8. The method for preparing bismuth ferrite-barium titanate textured piezoelectric ceramics as described in claim 1, characterized in that, ​ Step S8: grinding the textured ceramic surface and applying conductive silver paste on the upper and lower surfaces thereof; Step S9: performing polarization after firing the textured ceramic coated with the conductive silver paste.

9. A BiFe03-BaTi04 textured piezoelectric ceramic, characterized by, The method for preparing a BiFeO3-BaTiO3 textured piezoelectric ceramic according to any one of claims 1 to 8.

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