A large electrostrain BNT-KNN-BT-based lead-free piezoelectric ceramic and its preparation

Abstract

This invention proposes a large electrostrain BNT-KNN-BT-based lead-free piezoelectric ceramic and its preparation method, with the general chemical formula (0.95-x)Bi. 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-xK 0.48 Na 0.52 NbO3-0.05BaTiO3-yMO (M=Cu / Mn / Zn). The preparation method involves drying K2CO3, Na2CO3, Nb2O5, Bi2O3, Li2CO3, TiO2, BaCO3, and ZnO, CuO, or MnO2, then mixing them in a fluidized bed mill to obtain a mixed powder. This powder is then pre-sintered. The sintered powder is dispersed in anhydrous ethanol or deionized water, then milled in a sand mill and dried to obtain a mixed powder. The mixed powder is cold-pressed to obtain a ceramic preform, which is then sintered to obtain a ceramic sample. The ceramic sample is then polarized to obtain BNT-KNN-BT-based lead-free piezoelectric ceramics. The BNT-KNN-BT-based lead-free piezoelectric ceramics prepared by this invention exhibit good electrostrain coefficient and temperature stability.

Description

Technical Field

[0001] This invention relates to the field of lead-free piezoelectric materials technology, and in particular to a large electrostrain BNT-KNN-BT-based lead-free piezoelectric ceramic and its preparation. Background Technology

[0002] Piezoelectric ceramics are used to convert mechanical parameters (such as pressure and acceleration) into electrical parameters, or conversely, to convert electrical signals into mechanical motion or vibration. In sensors, they can convert force, pressure, and acceleration into electrical signals; in acoustic and ultrasonic transducers and actuators, they can convert electrical force into vibration or deformation.

[0003] With the advancement of science, electrostrictive materials are increasingly being used in aerospace, robotics, optics, mechanical manufacturing, and biomedicine. Currently, most piezoelectric devices are composed of PZT-based piezoelectric ceramics, which contain lead and pose environmental hazards. Therefore, researching and developing lead-free piezoelectric ceramics to replace PZT-based piezoelectric ceramics is of great significance.

[0004] BNT-based ceramics are a typical ABO3-type perovskite structure, possessing excellent ferroelectric properties, a large electromechanical coupling coefficient, and good acoustic characteristics, showing broad application prospects in electrostriction, high-temperature dielectrics, and energy storage. In the modification research of BNT ceramics, ion substitution is the most commonly used method, mainly divided into A-site ion substitution, B-site ion substitution, and simultaneous A-site and B-site substitution. The addition of "soft" additives such as La, Nb, Sb, and Nd ions increases the elastic compliance coefficient of the ceramic, decreases the coercivity and Qm, increases the dielectric constant and dielectric loss, and improves time stability; the mechanism of action of "hard" additives such as Fe, Co, Mn, and Al ions is the opposite of that of "soft" additives. Zhang et al. used 2% K... 0.5 Na 0.5 NbO3 replaces 0.94Bi 0.5 Na 0.5 Bi in TiO3-0.06BaTiO3 0.5 Na 0.5 TiO3 was used to achieve a small hysteresis electroinduced strain of 0.45%. Pham et al. studied Nb-doped Bi. 1 / 2 (Na 0.82 K 0.18 ) 1 / 2 TiO3 exhibited a large strain of 0.449% under an electric field of 7 kV / mm. This invention proposes to optimize the properties of BNT-BKT-KNN-based multi-component ceramics through non-equivalent ion doping. Summary of the Invention

[0005] This invention provides a new technical solution based on a multi-component BNT-KNN-BT-based lead-free piezoelectric ceramic. According to a first aspect of the invention, a large electrostrain BNT-KNN-BT-based lead-free piezoelectric ceramic is provided, the chemical composition of which is:

[0006] (0.95-x)Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-xK 0.48 Na 0.52 NbO3-0.05BaTiO3-yMO (M=Cu / Mn / Zn); the x , y For mole percentage, 0 < x ≤0.25, 0≤y≤0.1.

[0007] The present invention proposes a method for preparing the BNT-KNN-BT-based lead-free piezoelectric ceramic, which specifically includes the following steps:

[0008] (1) Preparation: Place K2CO3, Na2CO3, Nb2O5, Bi2O3, Li2CO3, TiO2, BaCO3, and ZnO or CuO or MnO2 into a petri dish and dry it in an oven at 110-150℃ for 3-5 hours.

[0009] (2) Mixing: Add the prepared raw materials to a fluidized bed air jet mill for mixing. After the air jet milling is completed, sieve the resulting powder to obtain mixed powder.

[0010] (3) Pre-calcination: The premixed powder obtained in step (2) is placed in a box furnace and continuously heated to 750-850℃, kept at the temperature for 4-6 hours, cooled to room temperature, pulverized and sieved to obtain pre-calcined powder.

[0011] (4) Fine grinding: The ceramic powder is finely ground by a sand mill. After grinding, the resulting slurry is dried and sieved to obtain mixed powder.

[0012] (5) Sintering: The pre-fired powder is cold-pressed into a green body with a diameter of 10 mm and a thickness of 1.0~1.5 mm, and sintered in a sintering furnace at 900-1200℃ for 4-10 h to obtain a dense piezoelectric ceramic sheet.

[0013] (6) Post-processing: The sintered piezoelectric ceramic sheet is processed into the required shape, silver layer is plated on both sides, and polarization aging is performed to obtain the BNT-KNN-BT based lead-free piezoelectric ceramic.

[0014] Further, the mixed raw materials described in step (2) are added to a fluidized bed air jet mill for mixing. The air pressure of the fluidized bed air jet mill is set to 0.7~0.85 MPa, and the mixing time is 3-8 hours.

[0015] Furthermore, the raw materials described in step (4) can be dispersed in anhydrous ethanol or deionized water.

[0016] Further, the pre-calcined powder in step (4) is mixed by a sand mill with a speed of 1200-3000 rpm for 2-4 hours.

[0017] This invention uses a fluidized bed air jet mill and a sand mill to refine and mix powders, which improves the grinding efficiency by 40% compared to a conventional ball mill, and the homogeneity of the processed powder is over 90%.

[0018] This invention modifies the BNT-KNN-BT group through ion doping, with Li + The addition of Cu disrupts the ferroelectric order, causing a transition from the ferroelectric phase to the relaxation phase, resulting in a gradual increase in electroinduced strain and a gradual decrease in negative strain. 2+ The addition of plasma lowers the sintering temperature while increasing the density and grain size of the ceramic; K

[0019] The increase in the relative content of NN also promotes the transformation of the electroplated phase to the relaxor phase. The BNT-KNN-BT-based lead-free piezoelectric ceramic prepared according to the above formula and method has an inverse piezoelectric coefficient d. 33 * It can reach over 500 pm / V, and its field-induced strain value can reach over 0.3% at 6kV / mm, exhibiting good electro-induced strain coefficient and temperature stability. Attached Figure Description

[0020] Figure 1 Examples 1, 2, 3, 4, 5, and 6 are shown in the formulation composition and electro-induced strain. Detailed Implementation

[0021] This specific implementation method is merely an explanation of the present invention and is not intended to limit it. Any modifications made by those skilled in the art after reading this specification, as long as they fall within the scope of the claims, will be protected by patent law.

[0022] This invention proposes a BNT-KNN-BT-based lead-free piezoelectric ceramic, characterized in that the BNT-KNN-BT-based lead-free piezoelectric ceramic has a chemical composition of (0.95-x)Bi as shown in the following general formula. 0.5 (Na 0.84 K 0.06 L

[0023] i 0.1) 0.5 TiO3-xK 0.48 Na 0.52 NbO3-0.05BaTiO3-yMO (M=Cu / Mn / Zn); the x , y For mole percentage, 0 < x ≤0.25, 0≤y≤0.1. With Li + The addition of [something] disrupts the ferroelectric order, causing a transition from the ferroelectric phase to the relaxation phase. The electroinduced strain gradually increases while the negative strain gradually decreases, and the inverse piezoelectric coefficient d [is affected]. 33 * It can reach over 500 pm / V; Cu 2+ The addition of plasma lowers the sintering temperature while increasing the density and grain size of the ceramic; the increase in the relative content of KNN also promotes the transformation of the electroplated phase to the relaxor phase.

[0024] The present invention proposes a method for preparing the BNT-KNN-BT-based lead-free piezoelectric ceramic, which specifically includes the following steps:

[0025] (1) Preparation: Place K2CO3, Na2CO3, Nb2O5, Bi2O3, Li2CO3, TiO2, BaTiO3, and ZnO or CuO or MnO2 into an oven and dry at 110-150℃ for 3-5 hours;

[0026] (2) Mixing: Add the prepared raw materials to a fluidized bed air jet mill for mixing. Set the air pressure to 0.7~0.85 MPa and the time to 3-8 hours. After grinding, sieve the powder to obtain mixed powder.

[0027] (3) Pre-calcination: The premixed powder obtained in step (2) is placed in a box furnace and continuously heated to 750-850℃, kept at the temperature for 3-8 hours, cooled to room temperature, pulverized and sieved to obtain pre-calcined powder;

[0028] (4) Fine grinding: The ceramic powder is dispersed in anhydrous ethanol and finely ground in a sand mill at a speed of 1200-3000 rpm for 2-4 hours. After grinding, the resulting slurry is dried and sieved to obtain a mixed powder. The second sand milling further refines the particle size to the set particle size, ensuring uniform particle size and improving its specific surface area and sintering activity.

[0029] (5) Sintering: The pre-fired powder is cold-pressed into a green body with a diameter of 10 mm and a thickness of 1.0~1.5 mm, and sintered in a sintering furnace at 900-1200℃ for 4-10 h to obtain a dense piezoelectric ceramic sheet.

[0030] (6) Post-processing: The sintered piezoelectric ceramic sheet is processed into the required shape, silver layer is plated on both sides, and polarization aging is performed to obtain the BNT-KNN-BT based lead-free piezoelectric ceramic.

[0031] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0032] Example 1:

[0033] (1) Preparation of materials: 7.602g Na2CO3, 0.935g K2CO3, 0.619g Li2CO3, 4.167g BaTiO3, 38.653g Bi2O3, 26.773g TiO2, 0.959g Nb2O5, 0.293g CuO;

[0034] (2) Mixing: Add the prepared raw materials to a fluidized bed air jet mill for mixing. The air pressure is set to 0.8 MPa and the time is 5 hours. After the air jet mill is completed, the powder obtained is sieved to obtain mixed powder.

[0035] (3) Pre-calcination: The premixed powder obtained in step (2) is placed in a box furnace and continuously heated to 850°C, kept at the temperature for 4 hours, cooled to room temperature, pulverized and sieved to obtain pre-calcined powder;

[0036] (4) Fine grinding: The ceramic powder is dispersed in anhydrous ethanol and finely ground in a sand mill at a speed of 2000 rpm for 3 hours. After grinding, the resulting slurry is dried and sieved to obtain mixed powder.

[0037] (5) Sintering: The pre-fired powder is cold-pressed into a green body with a diameter of 10 mm and a thickness of 1.5 mm, and sintered in a sintering furnace at 1150 °C for 4 h to obtain a dense piezoelectric ceramic sheet.

[0038] (6) Post-processing: The sintered piezoelectric ceramic sheet is processed into the required shape, cleaned, dried, screen-printed with silver paste, dried again, and fully polarized at 60℃ and 6kV / mm electric field for 15 minutes. Polarization aging yields a product with the general formula 0.93Bi. 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-0.02K 0.48 Na0.52 BNT-KNN-BT based lead-free piezoelectric ceramics of NbO3-0.05BaTiO3-0.01CuO.

[0039] Example 2:

[0040] The material composition is: 0.93Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-0.02K 0.48 Na 0.52 NbO3-0.05Ba

[0041] TiO3-0.02CuO. The piezoelectric ceramic with the above composition was obtained by repeating the preparation method of Example 1.

[0042] Example 3:

[0043] The material composition is: 0.92Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-0.03K 0.48 Na 0.52 NbO3-0.05Ba

[0044] TiO3-0.03CuO. The piezoelectric ceramic with the above composition was obtained by repeating the preparation method of Example 1.

[0045] Example 4:

[0046] The material composition is: 0.93Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-0.02K 0.48 Na 0.52 NbO3-0.05Ba

[0047] TiO3-0.01MnO. The piezoelectric ceramic with the above composition was obtained by repeating the preparation method of Example 1.

[0048] Example 5:

[0049] The material composition is: 0.92Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-0.03K 0.48 Na 0.52NbO3-0.05Ba

[0050] TiO3-0.02MnO. The piezoelectric ceramic with the above composition was obtained by repeating the preparation method of Example 1.

[0051] Example 6:

[0052] The material composition is: 0.91Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-0.04K 0.48 Na 0.52 NbO3-0.05Ba

[0053] TiO3-0.03MnO. The piezoelectric ceramic with the above composition was obtained by repeating the preparation method of Example 1.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A large electro-strained BNT-KNN-BT based lead-free piezoelectric ceramic, whose chemical composition is: (0.95-x)Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-xK 0.48 Na 0.52 NbO3-0.05BaTiO3-yMO, M = Cu / Mn / Zn; the x, y are molar percentages, 0 < x ≤ 0.25, 0 ≤ y ≤ 0.

1.

2. A method for manufacturing a large electro-strained BNT-KNN-BT based lead-free piezoelectric ceramic, characterized in that, The large electro-strain BNT-KNN-BT-based lead-free piezoelectric ceramic has a chemical composition of: (0.95-x)Bi 0.5 (Na 0.84 K 0.06 Li 0.1 ) 0.5 TiO3-xK 0.48 Na 0.52 NbO3-0.05BaTiO3-yMO, M=Cu / Mn / Zn; wherein x and y are molar percentages, 0 The manufacturing method comprises: (1) Preparation: K2CO3, Na2CO3, Nb2O5, Bi2O3, Li2CO3, TiO2, BaCO3, and ZnO or CuO or MnO2 are put into a culture dish and placed in an oven at 110-150°C for drying for 3-5h; (2) Mixing: The prepared raw materials are added into a fluidized bed jet mill for air jet milling, and the obtained powder is sieved to obtain a premixed powder; (3) Pre-sintering: The premixed powder obtained in step (2) is placed in a box furnace and continuously heated to 750-850°C for 4-6h, and then cooled to room temperature and crushed and sieved to obtain a pre-sintered powder; (4) Fine grinding: The pre-sintered powder is finely ground by a sand mill, and the obtained slurry is dried and sieved to obtain a mixed powder; (5) Sintering: The mixed powder is cold-pressed into a green body with a diameter of 10mm and a thickness of 1.0-1.5mm, and sintered at 900-1200°C for 4-10h in a sintering furnace to obtain a dense piezoelectric ceramic sheet; (6) Post-treatment: The sintered piezoelectric ceramic sheet is processed into the required shape, plated with a silver layer on both sides, and polarized and aged to obtain the BNT-KNN-BT-based lead-free piezoelectric ceramic.

3. The method for fabricating a large electrostrain BNT-KNN-BT-based lead-free piezoelectric ceramic according to claim 2, wherein, The prepared raw materials in step (2) are mixed in a fluidized bed jet mill, and the fluidized bed jet mill is set at an air pressure of 0.7-0.85Mpa for 3-8h.

4. The method of claim 2, wherein the BNT-KNN-BT based lead-free piezoelectric ceramic has a large electrostriction. The pre-sintered powder in step (4) can be dispersed in anhydrous ethanol or deionized water.

5. The method of claim 2, wherein the BNT-KNN-BT based lead-free piezoelectric ceramic has a large electrostriction. The pre-sintered powder in step (4) is mixed by a sand mill at a speed of 1200-3000rpm for 2-4h.