CN-118637901-B - Preparation method of BF-BT-BKT leadless piezoelectric ceramics with high-temperature thermal stability and high-voltage electrical property

Abstract

The invention discloses a preparation method of BF-BT-BKT leadless piezoelectric ceramics with high-temperature thermal stability and high-voltage electric performance, wherein the ceramic composition general formula is ：(1-x)Bi 1.02 FeO 3 -xBaTiO 3 -y(Bi 0.5 K 0.5 )TiO 3 +mLi 2 CO 3 +nMnO 2 ,, wherein x, y, m and n represent the mole fraction of components, x is more than 0.25 and less than or equal to 0.35, y is more than 0.05, m is more than 0.01, n is more than 0 and less than or equal to 0.01. In the preparation method, BKT is utilized to regulate and control the phase structure of BF-BT, so that the BKT has higher tetragonal distortion to improve the thermal stability of the ceramic. The preparation method of the ceramic with the textured microstructure is obtained by adding a low-temperature sintering auxiliary agent, constructing a temperature gradient field, externally adding an electric field and other technologies to influence the growth direction of ceramic grains and the electric domain structure. The BF-BT-BKT ceramic prepared by the method has piezoelectric performance of more than 460 pC/N at the temperature higher than 350 ℃, and can be used for high-temperature sensors, drivers and the like.

Inventors

• YANG XINYI
• CHEN QIAOHONG
• Huang Fenghao
• QIU SHAOHONG
• HOU YUXIN
• LUO FENG
• PAN XIAOMENG

Assignees

• 桂林电子科技大学

Dates

Publication Date

20260512

Application Date

20240622

Claims (4)

1. 1. A preparation method of BF-BT-BKT leadless piezoelectric ceramics with high temperature thermal stability and high piezoelectric property is characterized in that the preparation method comprises the step of controlling the growth direction of crystal grains and influencing domain structure by an external electric field by temperature gradient sintering; the preparation method comprises the following steps: 1) The analytical grade Bi 2 O 3 、Fe 2 O 3 、BaCO 3 、TiO 2 、K 2 CO 3 、Li 2 CO 3 and MnO 2 are used as raw materials, the proportioning is carried out according to (1-x)Bi 1.02 FeO 3 -xBaTiO 3 -y(Bi 0.5 K 0.5 )TiO 3 +mLi 2 CO 3 +nMnO 2 , the Bi element is excessive by 2.0 percent mol to compensate the volatilization of the bismuth element in the sintering process, wherein x, y, m and n represent the mole fraction of the components, and x is more than or equal to 0.25 and less than or equal to 0.35, y is more than or equal to 0 and less than 0.05, and m is more than or equal to 0 and less than or equal to 0.01,0 and less than or equal to 0.01; 2) Taking out the raw materials after ball milling for 24 hours by taking absolute ethyl alcohol as a medium, drying at 100 ℃ in a drying oven, sieving with a 200-mesh sieve, then putting the powder into a high-alumina crucible, compacting, capping, putting into a muffle furnace, quickly heating to 780 ℃ at the temperature rising rate of 300 ℃ per hour for presintering, keeping the temperature for 4 hours, powering off, cooling along with the furnace, and taking out for later use; 3) Taking out the presintered powder, performing secondary ball milling for 12 hours, taking out, drying, sieving, adding 5% PVA solution for granulating, tabletting and forming under 25MPa pressure in a tablet press to obtain cylindrical plain tablets with the diameter of 11.0mm and the height of 20.0 mm; 4) Placing the formed plain film into a tube furnace, horizontally placing the cylindrical plain film, wherein two ends of the cylindrical plain film are respectively positioned in two temperature areas with the set sintering temperature of T 1 、T 2 , wherein the temperature of the T 1 ≤900℃、960℃≤T 2 is not more than 850 ℃ and not more than 1010 ℃, two electrode plates are arranged at two ends of the tube furnace and are respectively connected with the positive electrode and the negative electrode of a direct current power supply, slowly heating to 600 ℃ at the heating rate of 60 ℃ per hour, preserving heat for 4 hours for discharging glue, then rapidly heating the two temperature areas to T 1 and T 2 at the heating rate of 5 ℃ per minute, simultaneously applying a direct current voltage U to the electrode plates at two ends of the tube furnace, wherein the voltage U is not more than 12V and not more than 36V, forming a stable direct current electric field in the tube furnace, keeping the electric field unchanged, cutting off the power after preserving heat and sintering for 240 minutes, keeping the external electric field unchanged, and cooling the sample to room temperature along with the furnace; 5) Transversely cutting the sintered ceramic sheet along the direction perpendicular to the length of the cylinder, wherein the cut sample is coin-shaped, has the thickness of 1.0mm and the diameter of 10.0mm, polishing the surface of the cut sample, plating silver paste on the surfaces of the two ends of the cut sample, and burning silver for 15min at 550 ℃; 6) Polarizing the ceramic sheet after silver firing in silicone oil, wherein the polarizing electric field is 6000V/mm, the polarizing temperature is 120 ℃, the time is 15min, the polarizing electric field is kept, and the ceramic sheet is taken out after being cooled to room temperature.
2. 2. A preparation method of BF-BT-BKT leadless piezoelectric ceramics with high temperature heat stability and high voltage performance is characterized by comprising the following steps: (1) Using analytical grade Bi 2 O 3 、Fe 2 O 3 、BaCO 3 、TiO 2 、K 2 CO 3 、Li 2 CO 3 and MnO 2 as raw materials, and preparing according to a formula of 0.70Bi 1.02 FeO 3 -0.30BaTiO 3 +0.015BKT+0.006Li 2 CO 3 +0.005MnO 2 , wherein the excessive Bi element is 2.0% mol when preparing to compensate volatilization of bismuth element in the sintering process; (2) Taking out the raw materials after ball milling for 24 hours by taking absolute ethyl alcohol as a medium, drying at 100 ℃ in a drying oven, sieving with a 200-mesh sieve, then putting the powder into a high-alumina crucible, compacting, capping, putting into a muffle furnace, quickly heating to 780 o ℃ at the temperature rising rate of 300 ℃ per hour for presintering, keeping the temperature for 4 hours, powering off, cooling along with the furnace, and taking out for later use; (3) Taking out the presintered powder, performing secondary ball milling for 12 hours, taking out, drying, sieving, adding 5% PVA solution for granulating, and performing tablet feeding molding under the pressure of 25MPa in a tablet press to obtain cylindrical plain tablets with the diameter of 10.0mm and the height of 20.0-25.0 mm; (4) Placing the formed plain film into a tube furnace, horizontally placing the cylindrical plain film, respectively placing two ends of the cylindrical plain film in two temperature areas with set sintering temperatures of T 1 and T 2 , slowly heating to 600 ℃ at a heating rate of 60 ℃ per hour, discharging glue when the temperature is kept for 4 hours, then quickly heating the two temperature areas to T 1 =900 ℃ and T 2 =990 ℃ at a heating rate of 5 ℃ per minute, switching on a direct current power supply to electrode plates at two ends of the tube furnace, keeping the voltage unchanged after the voltage is increased to 24V, keeping the power off after the temperature is kept for 240 minutes, keeping the external electric field unchanged, and cooling the sample to room temperature along with the furnace; (5) Cutting the sintered ceramic sheet along the radial direction into coin-shaped wafer samples with the thickness of 1.0mm and the diameter of 10.0mm, polishing the surfaces of the cut samples, plating silver paste on the surfaces of the two ends of the cut samples, and burning silver for 15min at 550 ℃; (6) Polarizing the silver-fired piezoelectric ceramic sheet in silicone oil, polarizing an electric field at 6000V/mm and a polarizing temperature of 120 ℃, preserving heat and maintaining pressure for 15min, keeping the voltage unchanged, powering off, cooling, and taking out after the temperature is reduced to room temperature.
3. 3. The ceramic prepared by the preparation method of the BF-BT-BKT leadless piezoelectric ceramic with high-temperature heat stability and high-voltage electric performance according to claim 1, which has the following composition general formula: (1-x)BiFeO 3 -xBaTiO 3 -y(Bi 0.5 K 0.5 )TiO 3 +mLi 2 CO 3 +nMnO 2 , Wherein x, y, m and n represent the mole fraction of the components, and 0.25≤x≤0.35, 0< y < 0.05, 0< m < 0.01,0 < n≤0.01.
4. 4. The ceramic prepared by the preparation method of BF-BT-BKT leadless piezoelectric ceramics with high-temperature heat stability and high-voltage electric performance according to claim 2, wherein the chemical formula is 0.70BiFeO 3 -0.30BaTiO 3 +0.015BKT+0.006Li 2 CO 3 +0.005MnO 2 .

Description

Preparation method of BF-BT-BKT leadless piezoelectric ceramics with high-temperature thermal stability and high-voltage electrical property Technical Field The invention relates to the technical field of preparation of lead-free piezoelectric ceramics, in particular to a bismuth ferrite-barium titanate-based ceramic with ultrahigh voltage performance, d 33 >450 pC/N and highest real-time working temperature (T dr) of more than 350 o C, and specifically relates to a preparation method of BF-BT-BKT lead-free piezoelectric ceramics with high temperature thermal stability and high voltage performance. Background Piezoelectric ceramics are a functional material capable of mutually converting mechanical energy and electric energy, and are widely applied to the fields of sensors, actuators, ultrasonic equipment and the like due to excellent piezoelectric effect and electromechanical coupling performance. The traditional piezoelectric ceramics mostly take lead zirconate titanate (PZT) as a main component, and have serious environmental pollution problems. Therefore, development of piezoelectric ceramics with environmental protection, low cost and high performance is a necessary trend of future development. Along with the continuous progress of technology, the high-temperature piezoelectric material is more and more widely applied to the high-temperature fields such as aerospace, automobile industry, petroleum exploration, 3D printing and the like. However, the existing studies show that high temperature stability and high voltage performance are opposite, the higher the piezoelectric performance, the lower the temperature stability, and the higher the curie temperature, the lower the piezoelectric performance. At present, a piezoelectric ceramic system with high-voltage electrical property and high-temperature thermal stability is only a bismuth scandium acid-lead titanate (BiScO 3-PbTiO3) system. However, the expensive price of scandium metal and the toxicity of lead severely limit its range of application. Therefore, the research on obtaining the high-performance lead-free piezoelectric ceramic with high-voltage electrical performance and high-temperature thermal stability has important significance. The BiFeO 3-BaTiO3 (BF-BT) system is paid attention to because of a perovskite structure system and a high Curie temperature, however, the improvement of the performance of the system is mainly controlled by a phase structure, and ceramics with high-voltage electric performance and high-temperature thermal stability are difficult to obtain at present. The highest room temperature piezoelectric performance of the four-element system of bismuth ferrite-barium titanate-sodium bismuth titanate-bismuth magnesium niobate (BF-BT-BNT-BMN) reaches about 210 pC/N. Liu Laijun of Guilin university prepares BF-BT-BKT ceramics through high temperature quenching and other processes to obtain ceramic samples with the room temperature piezoelectric performance reaching 150pC/N, but the high temperature quenching process is easy to form a large number of microcracks in the ceramics, is easy to age in the use process, is extremely easy to damage equipment, is complex in operation and is not suitable for industrial production. The prior researches show that the thermal stability of the piezoelectric ceramic is not only related to the Curie temperature, but also related to the phase structure, and the larger the tetragonal distortion is, the higher the temperature stability is. Meanwhile, the piezoelectric performance of the piezoelectric ceramic is closely related to the microstructure of the ceramic, and the grain growth presents certain direction selectivity through a texturing process, so that the piezoelectric performance can be greatly improved. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a preparation method of BiFeO 3-BaTiO3-(Bi0.5K0.5)TiO3 (BF-BT-BKT) lead-free piezoelectric ceramic with high-temperature thermal stability and high-voltage electrical property, which influences the grain growth direction through a temperature gradient structure and influences the domain structure direction by utilizing external electric field induction, thereby improving the piezoelectric activity of the system. The method does not need high-temperature quenching, and compared with the prior art, the ceramic has higher piezoelectric property and higher thermal stability. In order to realize the purpose of keeping high Curie temperature and improving the piezoelectric performance and the thermal stability, BF-BT with high Curie temperature and perovskite structure is selected as a matrix material, and the phase structure of the BF-BT is regulated and controlled near MPB component points by (Bi 0.5K0.5)TiO3 (BKT) with high Curie temperature and tetragonal phase structure, so that BF-BT-BKT leadless piezoelectric ceramics with the vicinity of the three-tetragonal phase MPB structure and close to one side