High-strain bismuth ferrite-based lead-free piezoelectric ceramic and method for preparing the same

Abstract

The present invention provides a high-strain bismuth ferrite-based lead-free piezoelectric ceramic and a preparation method thereof, which is represented by the composition general formula (1-x-y)BiFeO3-xBaTiO3-yM, where 0.25 < x < 0.35 and 0.005 < y < 0.08; the dopant M is selected from BaHfO3, CaSiO3, MgSiO3, BeSiO3, SrSiO3, SrSnO3, BiYO3, SbYO3, SbGaO3, BiYO3, YGaO3 or LaAlO3. The bismuth ferrite-based lead-free ceramic material of the present invention has excellent density (>95%), high strain performance, high Curie temperature and other characteristics. At the same time, the solid-phase sintering process technology adopted by the present invention is simple in operation and low in cost, suitable for mass production, and the prepared bismuth ferrite-based ternary system lead-free ceramic material can be used as a dielectric material for multilayer ceramic brakes.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic non-metallic materials, and particularly relates to a high-strain bismuth ferrite-based lead-free piezoelectric ceramic and a preparation method thereof. Background Art

[0002] With the rapid development of electronic science and information technology, electronic devices are gradually developing towards miniaturization, integration and lightweight. Piezoelectric ceramics belong to important functional materials and have very wide applications in military, aerospace, electric vehicles and electronic components. With the great development of society and technology, energy consumption is serious and the environment is deteriorating, which promotes the miniaturization, lightweight and lead-free of electronic components. Research and development of lead-free piezoelectric ceramics with high piezoelectric performance is a topic of great social significance and economic value, and it is also the development trend and research focus in the field of piezoelectric materials in recent years.

[0003] Traditional piezoelectric ceramics are mainly lead zirconate titanate, which has excellent piezoelectric properties and high temperature stability. In lead-free piezoelectric materials, the bismuth ferrite-barium titanate binary system lead-free piezoelectric ceramic has a large electrostrain due to the existence of the morphotropic phase boundary and is usually considered as one of the excellent lead-based ceramic substitutes. The strain performance of the bismuth ferrite-barium titanate lead-free piezoelectric ceramic doped and modified by single element or multi-elements has been improved, but the Curie temperature decreases, the leakage current becomes larger, and the breakdown strength is not high. To overcome the above problems, it is necessary to modify the bismuth ferrite-based lead-free piezoelectric ceramic to improve the piezoelectric performance and dielectric performance, while improving the material density and breakdown strength and effectively reducing the leakage current. Summary of the Invention

[0004] To solve the problems proposed in the above background art, the present invention provides a perovskite structure salt that can be used for doping modification, a bismuth ferrite-based ternary system lead-free ceramic material and a preparation method thereof, which overcome the defects of the bismuth ferrite-barium titanate binary system lead-free piezoelectric ceramic in the prior art, improve the density, and achieve characteristics such as high strain and high Curie temperature.

[0005] One aspect of the present invention provides a bismuth ferrite-based ternary piezoelectric ceramic composition, which is represented by the general formula (1-x-y)BiFeO3-xBaTiO3-yM,

[0006] where 0.25 < x < 0.35, 0.005 < y < 0.08; the dopant M is selected from BaHfO3, CaSiO3, MgSiO3, BeSiO3, SrSiO3, SrSnO3, BiYO3, SbYO3, SbGaO3, BiYO3, YGaO3 or LaAlO3.

[0007] Further, 0.28 < x < 0.34, 0.01 < y < 0.08; More preferably, 0.30 < x < 0.32, 0.01 < y < 0.03.

[0008] In one aspect of the present invention, a method for preparing the above-mentioned bismuth ferrite-based ternary piezoelectric ceramic composition is provided. The preparation method includes the following steps:

[0009] 1) Calculate and weigh raw materials according to the general composition formula of the bismuth ferrite-based ternary piezoelectric ceramic composition to be prepared, and roll mill after adding a solvent to obtain a raw material mixed slurry;

[0010] 2) Dry and grind the raw material mixed slurry obtained in step 1) into raw material powder;

[0011] 3) Pre-burn the raw material powder obtained in step 2) to obtain pre-burned ceramic powder;

[0012] 4) Perform high-speed ball milling on the pre-burned ceramic powder obtained in step 3) to obtain a ceramic mixed slurry;

[0013] 5) Dry and grind the ceramic mixed slurry obtained in step 4) into ceramic grinding powder;

[0014] 6) Add a binder solution to the ceramic grinding powder obtained in step 5), stir evenly, and granulate to obtain granulated powder;

[0015] 7) Press the granulated powder obtained in step 6) into a sheet-shaped green body;

[0016] 8) Sinter the sheet-shaped green body obtained in step 7) to obtain the bismuth ferrite-based ternary piezoelectric ceramic composition;

[0017] The raw materials include Bi2O3, Fe2O3, TiO2, and BaCO3 for generating BiFeO3 and 0.30BaTiO3, and also include BaCO 3、 CaCO3, MgCO3, SrCO3, La2O3, Al2O3, Nb2O5, HfO2, SnO2, Ga2O3, Sb2O5, In2O3, Y2O3, BeO, SiO2 required raw materials.

[0018] Further, the method for calculating and weighing raw materials in step 1) is as follows:

[0019] S11) Confirm the ratio of each cation in the general composition formula,

[0020] S12) Confirm the amount of raw materials used to ensure that the molar ratio of cations in the raw materials is consistent with the ratio of each cation in the general composition formula.

[0021] Furthermore, in step 1), the solvent is an organic solvent, and further, the organic solvent is selected from ethanol and acetone.

[0022] Furthermore, in step 1), the mass ratio of zirconium balls, raw materials, and solvent used in the roller mill is (1-5):1:(0.5-2); even further, it is 2:1:0.5.

[0023] Further, in step 1), the rotation speed of the roller mill is 400 to 1000 rpm, and the roller milling time is 6 to 24 hours.

[0024] Furthermore, step 1) also includes the step of removing water of crystallization and carbonates from the raw materials at high temperature.

[0025] Further, step 2) involves drying the raw material mixture slurry obtained in step 1) at 80–120°C for 5–24 hours to form a solid, and then grinding it into raw material powder;

[0026] Further, step 3) involves placing the raw material powder obtained in step 2) in a container, heating it to 600-900°C at a heating rate of 5-10°C / min, holding it at that temperature for 2-4 hours for pre-firing, and then cooling it with the furnace to obtain pre-fired ceramic powder.

[0027] Further, step 4) involves placing the pre-fired ceramic powder obtained in step 3) into a ball mill and using anhydrous ethanol as a solvent and zirconia balls as a medium to perform roller milling to obtain a mixed slurry;

[0028] Preferably, the mass ratio of the zirconia balls, the pre-fired ceramic powder obtained in step 3), and anhydrous ethanol is (5-20):1:(0.5-2).

[0029] Preferably, the ball mill rotates at a speed of 200–800 rpm, and the ball milling time is 3–24 hours.

[0030] Further, step 5) specifically involves drying the mixed slurry obtained in step 4) at 80–120°C for 5–24 hours to form a solid, grinding it, and then passing it through a 200-mesh sieve to obtain ceramic grinding powder. Further, in step 6), the binder is selected from vinyl butyral and polyvinyl alcohol.

[0031] Further, in step 6), the adhesive is a polyvinyl butyral solution with a mass fraction of 6-12%.

[0032] Furthermore, in step 6), the mass of the adhesive is 20-40% of the mass of the ceramic grinding powder obtained in step 5).

[0033] Furthermore, the pressing pressure in step 7) is 80–254 MPa. Even further, it is 120–135 MPa.

[0034] Preferably, in step 8), the sintering temperature is increased to 550-600°C at a heating rate of 1-3°C / min, held at the temperature for 2-4 hours to remove the polyvinyl butyral binder, and then increased to the selected sintering temperature of 950-1400°C at a heating rate of 5-10°C / min, held for 2-4 hours, and cooled to room temperature at a cooling rate of 5-10°C / min.

[0035] In another aspect, the present invention provides a multilayer ceramic brake comprising a dielectric material composed of the above-described bismuth ferrite-based ternary piezoelectric ceramic composition.

[0036] The beneficial effects of this invention are as follows:

[0037] The bismuth ferrite-based lead-free ceramic material of this invention has excellent density (>95%), high strain performance, and high Curie temperature. Under an electric field of 60 kV / cm, the strain range is about 0.09 to 0.35%, the corresponding inverse piezoelectric coefficient is between 150 and 583 pm / V, and the Curie temperature is between 350 and 500℃.

[0038] Meanwhile, the solid-state sintering process technology used in this invention is simple to operate, low in cost, and suitable for large-scale production. The bismuth ferrite-based ternary lead-free ceramic material prepared can be used as the medium material for multilayer ceramic brakes. Attached Figure Description

[0039] Figure 1 Hysteresis loop of lead-free piezoelectric ceramics of 0.67BiFeO3-0.30BaTiO3-0.03BaHfO3.

[0040] Figure 2 Strain curves of lead-free piezoelectric ceramics of 0.67BiFeO3-0.30BaTiO3-0.03BaHfO3.

[0041] Figure 3 Dielectric temperature spectrum of lead-free piezoelectric ceramics of 0.67BiFeO3-0.30BaTiO3-0.03BaHfO3.

[0042] Figure 4 Grain morphology of lead-free piezoelectric ceramics of 0.67BiFeO3-0.30BaTiO3-0.03BaHfO3.

[0043] Figure 5 Hysteresis loop of lead-free piezoelectric ceramics consisting of 0.66BiFeO3-0.32BaTiO3-0.02CaSiO3.

[0044] Figure 6 Strain curves of lead-free piezoelectric ceramics of 0.66BiFeO3-0.32BaTiO3-0.02CaSiO3.

[0045] Figure 7 Dielectric temperature spectrum of lead-free piezoelectric ceramics of 0.66BiFeO3-0.32BaTiO3-0.02CaSiO3.

[0046] Figure 8 Grain morphology of lead-free piezoelectric ceramics consisting of 0.66BiFeO3-0.32BaTiO3-0.02CaSiO3. Detailed Implementation

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below, but should not be construed as limiting the scope of the present invention.

[0048] Example 1: Preparation and Testing of 0.67BiFeO3-0.30BaTiO3-0.03BaHfO3 Lead-Free Piezoelectric Ceramics

[0049] A lead-free ceramic material with high strain resistance was prepared using a ternary system of bismuth ferrite-barium titanate-barium hafnium oxide, with the formula (1-xy)BiFeO3-xBaTiO3-yBaHfO3, where x = 0.30 and y = 0.03, i.e., 0.67BiFeO3-0.30BaTiO3-0.03BaHfO3.

[0050] The preparation method includes the following steps:

[0051] 1) High-purity (99.9%) Bi2O3, Fe2O3, TiO2, BaCO3 and HfO2 raw materials were placed in crucibles and heated to 180℃, 600℃, 900℃, 180℃ and 1000℃ respectively in a muffle furnace at a heating rate of 5℃ / min and held for 6h to remove impurities such as water of crystallization and carbonates that may be contained in the raw materials at high temperature.

[0052] Weigh the dried Bi2O3 (15.7673g), Fe2O3 (5.4037g), TiO2 (2.4203g), BaCO3 (6.5253g) and HfO2 (0.6321g) from step 1) and add the powder to a roller mill jar containing zirconium balls. Add anhydrous ethanol as a solvent. The mass ratio of zirconium balls, raw materials and anhydrous ethanol is 2:1:0.5. Place the roller mill jar on a roller mill and roller mill at 700 rpm for 24 hours to obtain a raw material mixture slurry.

[0053] 2) Pour the raw material mixture obtained in step 2) into a beaker, place the beaker in an 80℃ forced-air drying oven and dry it for 24 hours to form a solid, then grind it thoroughly for 30 minutes to form raw material powder;

[0054] 3) Place the raw material powder obtained in step 3) into a crucible, place the crucible in a muffle furnace and heat it to 800°C at a heating rate of 5°C / min and hold it at that temperature for 2 hours. Then cool it with the furnace to obtain pre-fired ceramic powder.

[0055] 4) Place the pre-fired ceramic powder (10g) obtained in step 4) into a tungsten gold ball mill jar (80ml), add tungsten gold balls (1mm diameter) and anhydrous ethanol, wherein the mass ratio of zirconium balls, ceramic powder and anhydrous ethanol is 10:1:2. Place the tungsten gold jar into a high-speed ball mill, set the speed to 1000rpm and ball mill for 6 hours to obtain a ceramic mixture slurry;

[0056] 5) Pour the ceramic mixture into a beaker and dry it in an 80℃ oven for 24 hours. Grind it into powder and pass it through a 200-mesh sieve to obtain ceramic grinding powder.

[0057] 6) Add 4g of 8% polyvinyl butyral solution to 10g of ceramic grinding powder obtained in step 5), stir evenly, and granulate into granulated powder.

[0058] 7) The granulated powder obtained in step 6) is pressed into sheet-like green bodies in a stainless steel mold at a pressure of 127 MPa.

[0059] 8) Place the sheet-like green body in a crucible, and place the crucible in a muffle furnace for sintering. The muffle furnace is heated to 550℃ at a heating rate of 2℃ / min, held for 3h to remove the polyvinyl butyral binder, and then heated to the sintering temperature of 1000℃ at a heating rate of 5℃ / min, held for 3h, and then cooled to room temperature at a cooling rate of 5℃ / min to obtain a 0.67BiFeO3-0.30BaTiO3-0.03BaHfO3 ternary system lead-free piezoelectric ceramic with high strain performance and high Curie temperature.

[0060] The results of the tests showed that its piezoelectric, dielectric properties, and grain morphology were as follows: Figure 1-4 As shown.

[0061] Figure 4 The grain structure of piezoelectric ceramics, through Figure 4 It can be seen that the prepared bismuth ferrite-based lead-free ceramic materials have excellent density (>95%), high strain performance, and high Curie temperature. The material with the best performance has a strain of about 0.198% under an electric field of 60 kV / cm, with a corresponding inverse piezoelectric coefficient of 330 pm / V and a Curie temperature of 408℃.

[0062] Example 2: Preparation and Testing of 0.66BiFeO3-0.32BaTiO3-0.02CaSiO3 Lead-Free Piezoelectric Ceramics

[0063] A lead-free ceramic material with high strain performance was prepared using a ternary system of bismuth ferrite-barium titanate-calcium silicate, with the formula (1-xy)BiFeO3-xBaTiO3-yCaSiO3, where x = 0.32 and y = 0.02, i.e., 0.66BiFeO3-0.32BaTiO3-0.02CaSiO3. The preparation method includes the following steps:

[0064] 1) Analytical grade (AR grade) Bi2O3, Fe2O3, BaCO3, TiO2, CaCO3 and SiO2 raw materials were placed in crucibles and heated to 180℃, 600℃, 180℃, 900℃, 180℃ and 180℃ respectively in a muffle furnace at a heating rate of 5℃ / min. The high temperature was used to remove impurities such as water of crystallization and carbonates that may be present in the raw materials.

[0065] Weigh the dried Bi2O3, Fe2O3, BaCO3, TiO2, CaCO3, and SiO2 from step 1) according to the composition formula. Add the weighed Bi2O3 (15.5320g), Fe2O3 (5.3230g), BaCO3 (6.3275g), TiO2 (2.5817g), CaCO3 (0.2002g), and SiO2 (0.1202g) to a roller mill jar containing zirconium balls. Add anhydrous ethanol as a solvent. The mass ratio of zirconium balls, raw materials, and anhydrous ethanol is 2:1:0.5. Place the roller mill jar on a roller mill and roller mill at 600 rpm for 24 hours to obtain a raw material mixture slurry.

[0066] 2) Pour the raw material mixture obtained in step 2) into a beaker and place it in an 80℃ oven for 24 hours to solidify it. Grind it thoroughly for 30 minutes to obtain raw material powder.

[0067] 3) Place the raw material powder obtained in step 3) in a crucible, place the crucible in a muffle furnace and heat it to 800°C at a heating rate of 5°C / min, hold it at that temperature for 2 hours, and then cool it with the furnace to obtain pre-fired ceramic powder.

[0068] 4) Place the pre-fired ceramic powder obtained in step 4) into a ball mill, add a certain amount of zirconium balls and anhydrous ethanol, wherein the mass ratio of zirconium balls, ceramic powder and anhydrous ethanol is 2:1:0.5, the rotation speed is 800 rpm, and the ball mill is used for 24 hours to obtain a mixed slurry.

[0069] 5) Pour the mixed slurry into a beaker, place the beaker in an 80℃ forced-air drying oven and dry for 24 hours to form a solid, then grind it into ceramic grinding powder;

[0070] 6) Add 10g of a 5% polyvinyl butyral solution to the ceramic grinding powder obtained in step 5), stir evenly, and granulate into granulated powder.

[0071] 7) The granulated powder obtained in step 6) is pressed into a round blank in a stainless steel mold at a pressure of 139 MPa.

[0072] 8) Place the circular green blank in a crucible and sinter it in a muffle furnace. Heat the muffle furnace to 550℃ at a heating rate of 2℃ / min, hold for 3 hours to remove the binder, then heat to 1000℃ at a heating rate of 5℃ / min, hold for 6 hours and then cool with the furnace to obtain a ternary system of lead-free piezoelectric ceramics with high strain performance and high Curie temperature of 0.66BiFeO3-0.32BaTiO3-0.02CaSiO3.

[0073] The results of the tests showed that its piezoelectric, dielectric properties, and grain morphology were as follows: Figure 5-8 As shown.

[0074] from Figure 1 and Figure 5 It can be seen that the maximum polarizability of the piezoelectric ceramic composition of the present invention reaches 37-39 μC / cm. 2 ; Figure 2 and Figure 6 This reflects the inverse piezoelectric properties of the piezoelectric ceramic, with the strain values ​​reaching a maximum of 0.097–0.198%, corresponding to inverse piezoelectric constants of 162–330 pm / V. From Figure 3 and 7 It can be seen that the Curie temperature of the piezoelectric ceramic composition of the present invention reaches 360-412°C, and the dielectric loss is less than 0.15 in the range of room temperature to 300°C. Figure 4 and Figure 8 It can be seen that the piezoelectric ceramic composition of the present invention has a dense and uniform microstructure and is free of impurities.

[0075] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention.

Claims

1. A bismuth ferrite-based ternary piezoelectric ceramic composition, characterized in that, It is composed of the general formula (1- x - y BiFeO3- x BaTiO3- y M indicates, Where, 0.30≤x≤0.32, 0.01 <y≤0.03; The dopant M is selected from BaHfO3 and CaSiO3.

2. The method for preparing the bismuth ferrite-based ternary piezoelectric ceramic composition according to claim 1, characterized in that, The preparation method includes the following steps: 1) Weigh the raw materials according to the general formula of the bismuth ferrite-based ternary piezoelectric ceramic composition to be prepared, add solvent and roll mill to obtain raw material slurry; 2) Dry and grind the raw material mixture obtained in step 1) into raw material powder; 3) The raw material powder obtained in step 2) is pre-fired to obtain pre-fired ceramic powder; 4) The pre-fired ceramic powder obtained in step 3) is subjected to high-speed ball milling to obtain a ceramic slurry; 5) Dry and grind the ceramic mixture obtained in step 4) into ceramic grinding powder; 6) Add binder solution to the ceramic grinding powder obtained in step 5), stir evenly, and granulate to obtain granulated powder; 7) Press the granulated powder obtained in step 6) into sheet-like preforms; 8) The sheet-like preform obtained in step 7) is sintered to obtain the bismuth ferrite-based ternary piezoelectric ceramic composition; The raw materials include Bi2O3, Fe2O3, TiO2 and BaCO3 used to generate BiFeO3 and BaTiO3, and also include CaCO3, HfO2 and SiO2 used to generate the perovskite structure salt ABO3.

3. The preparation method according to claim 2, characterized in that, The method for calculating and weighing raw materials in step 1) is as follows: S11) Confirm the ratio of each cation in the general formula. S12) Confirm the amount of raw materials to ensure that the molar ratio of cations in the raw materials is consistent with the ratio of each cation in the general formula.

4. The preparation method according to claim 3, characterized in that, Step 3) involves placing the raw material powder obtained in step 2) in a container, heating it to 600-900°C at a heating rate of 5-10°C / min, holding it at that temperature for 2-4 hours for pre-firing, and then cooling it with the furnace to obtain pre-fired ceramic powder.

5. The preparation method according to claim 2, characterized in that, Step 5) Specifically, the mixed slurry obtained in step 4) is dried at 80~120°C for 5~24h to form a solid, ground, and then passed through a 200-mesh sieve to obtain ceramic grinding powder.

6. The preparation method according to claim 2, characterized in that, In step 6), the adhesive is selected from polyvinyl butyral and polyvinyl alcohol.

7. The preparation method according to claim 2, characterized in that, In step 6), the adhesive is a polyvinyl butyral solution with a mass fraction of 6-12%.

8. The preparation method according to claim 2, characterized in that, In step 6), the mass of the binder is 20-40% of the mass of the ceramic grinding powder obtained in step 5.

9. The preparation method according to claim 2, characterized in that, Step 7) The pressing pressure is 80~254MPa.

10. The preparation method according to claim 2, characterized in that, Step 7) The pressing pressure is 120~135MPa.

11. The preparation method according to claim 2, characterized in that, In step 8), the sintering temperature is increased to 550-600°C at a heating rate of 1-3°C / min, held at the temperature for 2-4 hours to remove the polyvinyl butyral binder, and then increased to the selected sintering temperature of 950-1400°C at a heating rate of 5-10°C / min, held for 2-4 hours, and cooled to room temperature at a cooling rate of 5-10°C / min.

12. A multi-layer ceramic brake, characterized in that, It comprises a dielectric material consisting of the bismuth ferrite-based ternary piezoelectric ceramic composition as described in claim 1.

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