A high-temperature energy harvesting lead-free piezoelectric ceramic material applied to 250 DEG C and preparation thereof

Abstract

The application relates to a lead-free piezoelectric ceramic material capable of being applied to high-temperature energy collection at 250 DEG C and a preparation method thereof, and belongs to the piezoelectric ceramic material field. The chemical composition of the ceramic material is Bi 1.02 FeO3-BaTiO3-x mol% MnO2, wherein the value of x is 0.0-0.5, preferably the material system with the value of x being 0.2. The sample is prepared by adopting the wet grinding, drying, granulating, pressing forming and sintering steps according to the corresponding metering ratio. The application realizes that the lead-free piezoelectric ceramic has excellent power generation characteristics at 250 DEG C, and has a great promoting effect on the piezoelectric energy collection technology industry.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramic materials, specifically relating to a lead-free piezoelectric ceramic material for high-temperature energy harvesting at 250°C and its preparation method. Background Technology

[0002] Piezoelectric energy harvesters (PEHs), based on piezoelectric ceramics, serve as a substitute or supplement to traditional fossil fuels and are widely used in high-tech fields such as aerospace and electric vehicles to provide tiered power to wireless sensors. In these fields, the operating environment temperature of wireless sensors is generally above 200°C, posing a significant challenge to the temperature adaptability of piezoelectric ceramics.

[0003] Currently, BiScO3-PbTiO3 (BS-PT) lead-based perovskite piezoelectric materials dominate the high-temperature piezoelectric market due to their combination of high-voltage piezoelectric activity and high-temperature stability, and are widely used in high-temperature PEH (polyelectric harmonics). However, such lead-based materials have adverse effects on the natural environment and human health, and are subject to strict restrictions under environmental laws in various countries. Furthermore, lead-free bismuth layered compounds, although possessing extremely high Curie temperatures (T0...),... C However, due to its inherent two-dimensional polarization configuration, lead-based ceramics have weak piezoelectric properties and cannot provide sufficient electrical energy as a PEH (petroelectric harmonic device). The novel lead-free piezoelectric ceramic BiFeO3-BaTiO3 (BF-BT) is considered the most likely lead-free ceramic system to replace lead-based ceramics for energy harvesting in high-temperature regions due to its ultra-high Curie temperature and high piezoelectric activity.

[0004] For high-temperature piezoelectric energy harvesting materials with high electromechanical conversion capabilities, a high energy density (u) is first required, expressed as:

[0005]

[0006] Where d×g is the transduction coefficient of the piezoelectric ceramic, A is the force-bearing area of ​​the piezoelectric ceramic, and F is the external excitation force. g is related to d and the dielectric constant ε. r Closely related, their relationship can be expressed as:

[0007]

[0008] Where ε0 is the vacuum permittivity, ε r is the relative permittivity. As can be seen from formulas (1) and (2), a high piezoelectric constant and a low permittivity are beneficial to the improvement of energy density.

[0009] Considering the impact of temperature changes that high-temperature piezoelectric energy harvesters face in practical applications, the ceramics are also required to have extremely high depolarization temperatures (T0).d This ensures that PEH maintains stable piezoelectric properties at higher temperatures. Furthermore, at high temperatures, the activation of oxygen vacancies leads to a significant decrease in the ceramic's insulation resistivity; therefore, the resistivity must be maintained at 10 ohms during application. 7 Above Ω·cm. If it is below this range, the generated charge will be difficult to capture by the electrodes, and no output current can be formed. This point has often been overlooked in previous studies.

[0010] In this invention, 0.70Bi was prepared using the excess Bi compensation method. 1.02 Using FeO3-0.30BaTiO3 as the matrix, Mn doping was introduced to construct 0.70Bi... 1.02 The FeO3-0.30BaTiO3-x mol%MnO2 (abbreviated as BF-BT-xMn) high-temperature piezoelectric ceramic material system was developed. The optimal BF-BT-xMn sample simultaneously exhibits high transducer coefficient, high depolarization temperature, and high insulation resistivity at 250℃, meeting the requirements for high-temperature energy harvesting and filling the gap in stable power generation of lead-free piezoelectric ceramics at 250℃. To date, no other lead-free materials with such excellent transducer coefficients and high-temperature applications have been reported in this patented system. Summary of the Invention

[0011] The purpose of this invention is to provide a lead-free piezoelectric ceramic material applicable to high-temperature piezoelectric energy harvesters and its preparation method. The prepared lead-free piezoelectric ceramic exhibits high transducer coefficient, high depolarization temperature, and high insulation resistivity at high temperatures. Its power generation characteristics at 250℃ were characterized using a cantilever beam energy harvester. To maintain good energy harvesting performance at high temperatures, this invention introduces excess bismuth and Mn doping to promote the increase of the transducer coefficient and improve the depolarization temperature of the ceramic. Simultaneously, the Mn doping and excess bismuth significantly improve the high-temperature insulation resistivity of the ceramic, solving the leakage problem at 250℃. Combining these factors, piezoelectric energy harvesting at 250℃ using lead-free ceramic materials is achieved.

[0012] To achieve the above objectives, the present invention adopts the following technical solution.

[0013] The lead-free piezoelectric material of the present invention, characterized by having a matrix chemical composition of 0.70Bi, is described in this invention. 1.02 The material system is FeO3-0.30BaTiO3-x mol%MnO2, where x is 0.0 to 0.5, and preferably x is 0.2.

[0014] The lead-free piezoelectric ceramic material with wide-temperature-range power generation characteristics described above in this invention is prepared by a conventional solid-state process, specifically including the following steps:

[0015] (1) According to the chemical formula 0.70Bi 1.02 The molar ratio of each element in FeO3-0.30BaTiO3-x mol%MnO2 is determined by weighing the raw materials Bi2O3, Fe2O3, BaCO3, TiO2 and MnO2, where the value of x is 0.0 to 0.5.

[0016] (2) Place the weighed raw material into a ball mill jar and ball mill it in a horizontal mill for 24 hours with anhydrous ethanol as the medium. After ball milling, dry the slurry and calcine the dried powder at 800°C for 3 hours and then cool it with the furnace.

[0017] (3) The powder cooled in step (2) is ball-milled twice and dried. The dried powder is then ground and granulated. PVA granulation is preferred. A 5% polyvinyl alcohol aqueous solution is used as a binder for granulation. The amount of binder is 1 ml of binder for every 10 g of ceramic powder.

[0018] (4) After the powder obtained by granulation in step (3) is left to stand, it is pressed into shape (e.g., under a pressure of 100MPa) to obtain a green body. Then, the debinding treatment is carried out (preferably the green body is debinded at 560℃). Finally, it is sintered at 980-1000℃, held for 3 hours, and cooled to room temperature with the furnace to obtain the target material.

[0019] The prepared lead-free piezoelectric material was first polished, and then its microstructure was tested. Next, a silver electrode was coated onto it, and artificial polarization was performed (e.g., in silicone oil at 90°C, at 50 kV·cm). -1 The samples were polarized at a given voltage for 30 minutes, followed by aging at room temperature for 24 hours, and their piezoelectric properties were tested. Finally, the variable-temperature power generation performance was tested using a cantilever beam energy harvester.

[0020] Through meticulous composition design and sintering process, dense ceramic samples were obtained. The optimal sample composition, after selection, was 0.70 Bi. 1.02 FeO3-0.30BaTiO3-0.2mol%Mn. The piezoelectric constant d of the material at 250℃. 33 =270pC / N, dielectric constant ε r =1677, transduction coefficient d×g=4905×10 -15 m 2 / N. Depolarization temperature T d ≈250℃. And at 250℃, the resistivity ρ>10 7 Ω·cm, power density P 250℃ = 5.83 μW / cm 3 It can meet the requirements for the use of high-temperature piezoelectric energy harvesting devices.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The lead-free piezoelectric ceramic material for high-temperature energy harvesting of the present invention can simultaneously possess a high transduction coefficient d×g, a high depolarization temperature, and a high insulation resistivity at a high temperature of 250℃. The above three points ensure that the system has excellent power generation characteristics at 250℃, and it is a potential lead-free piezoelectric ceramic material for high-temperature energy harvesting devices.

[0023] (2) The lead-free piezoelectric ceramic material of the present invention has a stable structure, a simple preparation method, low cost, and is easy to operate. When applied to piezoelectric energy harvesting devices, the present invention can effectively recover and reuse waste vibration energy, and is energy-saving, environmentally friendly, and safe, with significant economic and social value. Attached Figure Description

[0024] Figure 1 These are the dielectric temperature curves of ceramic samples with different compositions according to the present invention.

[0025] Figure 2 This is a graph showing the relationship between the in-situ piezoelectric constant of ceramic samples with different compositions and temperature.

[0026] Figure 3 The piezoelectric constants and dielectric constants of ceramic samples with different compositions in this invention are given at 250°C.

[0027] Figure 4 The transduction coefficients of ceramic samples with different compositions according to the present invention at 250°C are given.

[0028] Figure 5 This refers to the depolarization temperature of ceramic samples with different compositions in this invention.

[0029] Figure 6 This is a graph showing the relationship between the insulation resistivity of ceramic samples with different compositions and temperature.

[0030] Figure 7 The power density of different ceramic samples of the present invention at 250°C. Detailed Implementation

[0031] The essential features and significant advantages of the present invention are further illustrated below through examples. It should be noted that the present invention is by no means limited to the embodiments described.

[0032] Example 1:

[0033] According to the chemical formula 0.70Bi 1.02The raw materials Bi₂O₃, Fe₂O₃, BaCO₃, and TiO₂ were weighed according to the stoichiometric ratio of FeO₃-0.30BaTiO₃ and ball-milled in ethanol for 24 hours. After drying, the mixture was calcined at 800℃ for 3 hours; after a second ball milling and granulation, it was pressed into a green body at 100 MPa to obtain a green body. The green body was then subjected to debinding treatment at 560℃. Finally, it was sintered at 1000℃ for 3 hours to obtain the target material.

[0034] Example 2:

[0035] According to the chemical formula 0.70Bi 1.02 The stoichiometric ratio of FeO3-0.30BaTiO3-0.1mol%MnO2 was used. The raw materials Bi2O3, Fe2O3, BaCO3, TiO2 and MnO2 were weighed, and the rest was the same as in Example 1.

[0036] Example 3:

[0037] According to the chemical formula 0.70Bi 1.02 The stoichiometric ratio of FeO3-0.30BaTiO3-0.2mol%MnO2 was used. The raw materials Bi2O3, Fe2O3, BaCO3, TiO2 and MnO2 were weighed, and the rest was the same as in Example 1.

[0038] Example 4:

[0039] According to the chemical formula 0.70Bi 1.02 The stoichiometric ratio of FeO3-0.30BaTiO3-0.3mol%MnO2 was used. The raw materials Bi2O3, Fe2O3, BaCO3, TiO2 and MnO2 were weighed, and the rest was the same as in Example 1.

[0040] Example 5:

[0041] According to the chemical formula 0.70Bi 1.02 The stoichiometric ratio of FeO3-0.30BaTiO3-0.5mol%MnO2 was used. The raw materials Bi2O3, Fe2O3, BaCO3, TiO2 and MnO2 were weighed, and the rest was the same as in Example 1.

[0042] Table 1 Performance Comparison of the Above Embodiments

[0043]

[0044]

Claims

1. A lead-free piezoelectric ceramic material for high-temperature energy harvesting at 250 °C, characterized in that, For high-temperature energy harvesting at 250 °C, the matrix chemical composition of this lead-free piezoelectric ceramic material is: 0.70Bi. 1.02 FeO3-0.30BaTiO3-xmol% MnO2, where x is 0.1~0.5; The preparation method of lead-free piezoelectric ceramic materials includes the following steps: (1) According to the chemical formula 0.70Bi 1.02 The molar ratio of each element in FeO3-0.30BaTiO3-x mol% MnO2 is determined by weighing the raw materials Bi2O3, Fe2O3, BaCO3, TiO2 and MnO2, where the value of x is 0.1~0.

5. (2) Place the weighed raw material into a ball mill jar and ball mill it in a horizontal mill for 24 hours with anhydrous ethanol as the medium. After ball milling, dry the slurry and calcine the dried powder at 800°C for 3 hours and then cool it with the furnace. (3) The powder cooled in step (2) is ball-milled twice and dried. The dried powder is then granulated using PVA and a 5% polyvinyl alcohol aqueous solution is used as a binder. (4) After the powder obtained by granulation in step (3) is left to stand, it is pressed into shape to obtain a green body. Then, the glue is removed and sintered at 980-1000 ℃ for 3 hours. The material is then cooled to room temperature in the furnace to obtain the target material.

2. The lead-free piezoelectric ceramic material according to claim 1, characterized in that, The material system with an x ​​value of 0.2 exhibits excellent energy harvesting performance at 250 ℃: transduction coefficient d×g = 4905×10 -15 m 2 / N; High depolarization temperature T d ≈250℃; insulation resistivity ρ>10 at 250℃ 7 Ω·cm, power density P 250 ℃ =5.83 μW / cm 3 .

3. The lead-free piezoelectric ceramic material according to claim 1, characterized in that, The amount of binder used is 1 ml of binder for every 10 g of ceramic powder.

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