A lead-free high-entropy piezoelectric ceramic material with excellent energy harvesting temperature stability and preparation

Abstract

The application discloses a lead-free high-entropy piezoelectric ceramic material with excellent energy collection temperature stability and a preparation method thereof, and belongs to the piezoelectric ceramic material field.The chemical composition of the ceramic material is (1-x)[0.96(K 0.48 Na 0.52 )(Nb 0.96 Sb 0.04 )O3-0.04(Bi 0.5 Na 0.5 )ZrO3]+x[0.70BiFeO3-0.30BaTiO3+0.1mol%MnO2], wherein the value of x is 0, 0.05 and 1, and the configuration entropy ΔS is 0.93R, 1.46R and 1.22R, preferably the high-entropy material system with the value of x being 0.05.The sample is prepared by adopting the steps of wet grinding, drying, granulation, compression molding and sintering according to the corresponding metering ratio.The application realizes stable power generation of the lead-free piezoelectric energy collector in a wide temperature range, 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 high-entropy piezoelectric ceramic material with excellent energy harvesting temperature stability and its preparation. Background Technology

[0002] With the increasing scarcity of fossil fuels globally, developing clean and new energy technologies and promoting a green and low-carbon transformation of global energy is imperative. Piezoelectric energy harvesting technology, through the positive piezoelectric effect, can convert wasteful low-frequency vibrational energy in the environment into electrical energy. It holds promise for replacing existing chemical battery power supply methods, enabling long-term self-powering of microelectronic devices such as wireless sensors, and better serving the low-carbon construction of 5G smart cities (such as smart home systems, medical health monitoring, and intelligent transportation). This technology has garnered widespread attention and rapid development worldwide. However, currently, the piezoelectric ceramics used in piezoelectric energy harvesters are mainly lead-based piezoelectric materials. To strengthen ecological environmental protection and promote green and low-carbon development, lead-free piezoelectric materials and devices are bound to become the mainstream of future development.

[0003] To improve the electrical properties of lead-free piezoelectric materials, polycrystalline phase boundaries (such as trigonal-tetragonal, trigonal-orthorhombic-tetragonal, etc.) are typically constructed within them. However, the polycrystalline phase boundaries in lead-free piezoelectric ceramics, where two or three phases coexist, are not only controlled by composition but also affected by temperature. Once they deviate from the polycrystalline phase boundaries, the piezoelectric performance deteriorates drastically, resulting in poor temperature stability. Piezoelectric energy harvesters often operate in complex vibration environments. Some devices (pipeline transport devices, engines, pumps, etc.) inevitably generate a large amount of heat during long-term vibration, and thermal shock places stringent requirements on the temperature stability of the piezoelectric materials, the core components of piezoelectric energy harvesters. The high-entropy strategy is a new materials design theory, initially developed from high-entropy alloys, and has recently been applied to inorganic perovskite piezoelectric ceramics. Constructing high-entropy ceramics has become a major focus in materials research. Entropy is a physical quantity in thermodynamics describing the degree of disorder in a system; the entropy generated by the disorder of the system's internal configuration is called configurational entropy. According to the Boltzmann entropy function, in the ideal case, the configurational entropy of a system and the disorder of its internal particles have a qualitative relationship:

[0004]

[0005] In the formula, ΔS represents the configuration entropy of the system, R = 8.314 J / (mol·K) is the molar gas constant, n represents the number of components, and x i This refers to the mole fraction of the i-th component. Materials with high configurational entropy exhibit good structural stability and excellent functional properties. Therefore, to improve the piezoelectric temperature stability of lead-free piezoelectric materials, this invention uses 0.96 (K) 0.48 Na 0.52 (Nb) 0.96Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 A five-phase polymorphic phase structure insensitive to temperature was constructed by solid solution composites of ZrO3 (0.96KNNS-0.04BNZ) and 0.70BiFeO3-0.30BaTiO3-0.1mol%MnO2 (0.70BF-0.30BT-MnO2) using a high-entropy strategy. Because the A-site and B-site of the ABO3 perovskite structure are simultaneously occupied by multiple ions, the differences in the radius, electronegativity, and bond strength of the coordinating cations lead to continuous phase transformations, thus forming a stable high-entropy five-phase polymorphic phase structure, which is beneficial for improving the temperature stability of lead-free piezoelectric ceramic materials. Therefore, in order to construct a lead-free high-entropy piezoelectric ceramic material with excellent energy harvesting temperature stability, this invention constructs a high-entropy five-phase coexisting polycrystalline phase structure by solid solution composite of 0.96KNNS-0.04BNZ and 0.70BF-0.30BT-MnO2, thereby obtaining a lead-free piezoelectric energy harvesting material system with excellent piezoelectric temperature stability. Summary of the Invention

[0006] The purpose of this invention is to provide a lead-free high-entropy piezoelectric ceramic material with excellent energy harvesting temperature stability and its preparation method. The prepared lead-free piezoelectric ceramic exhibits excellent piezoelectric temperature stability. Its power generation characteristics over a wide temperature range were characterized using a cantilever beam energy harvester. To achieve excellent energy harvesting temperature stability, this invention constructs a five-phase polycrystalline phase structure by compositing 0.96KNNS-0.04BNZ and 0.70BF-0.30BT-MnO2, thus realizing the piezoelectric charge constant d. 33 It maintains excellent piezoelectric temperature stability over a wide temperature range (25-120℃). 33 ≥200pC / N and Δd 33 ≤±10%), thereby obtaining a lead-free piezoelectric energy harvesting material system with excellent piezoelectric temperature stability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] The lead-free high-entropy piezoelectric ceramic material of the present invention, which exhibits excellent energy harvesting temperature stability, is characterized by having a matrix chemical composition of: (1-x)[0.96(K)] 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5The reaction is ZrO3]+x[0.70BiFeO3-0.30BaTiO3+0.1mol%MnO2], where x has values ​​of 0, 0.05 and 1, and the corresponding configurational entropy ΔS is 0.93R, 1.46R and 1.22R, respectively. The preferred high-entropy material system is one where x has a value of 0.05.

[0009] The lead-free high-entropy piezoelectric ceramic material with excellent energy harvesting temperature stability described above in this invention is prepared by a conventional solid-state process, specifically including the following steps:

[0010] (1) According to the chemical formula (1-x)[0.96(K) 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 The molar ratio of each element in [ZrO3]+x[0.70BiFeO3-0.30BaTiO3+0.1mol%MnO2] is determined by weighing the raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3, ZrO2, Fe2O3, BaCO3, TiO2 and MnO2, where x has values ​​of 0, 0.05 and 1.

[0011] (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 850°C for 6 hours and then cool it with the furnace.

[0012] (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.

[0013] (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 glue is removed (preferably the green body is removed at 560℃). Finally, it is sintered at 1120℃, kept at the temperature for 3 hours, and cooled to room temperature in the furnace to obtain the target material.

[0014] The prepared lead-free piezoelectric material was first surface-polished, then coated with a silver electrode and artificially polarized (e.g., in silicone oil at 100°C, 40 kV·cm). -1 The samples were polarized in an electric field for 30 minutes and aged at room temperature for 24 hours to test their piezoelectric properties. Finally, using a cantilever beam energy harvester, the variable-temperature power generation performance was tested from room temperature to 120°C under an external force stimulus of 89 Hz resonant frequency and 1g acceleration.

[0015] Through meticulous composition design and sintering process, dense ceramic samples were obtained. The optimal sample composition, after optimization, was: 0.95[0.96(K)]. 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 The mixture [ZrO3] + 0.05[0.70BiFeO3-0.30BaTiO3+0.1mol%MnO2] has a high configurational entropy ΔS = 1.46R and a polymorphic phase structure with five coexisting phases (trigonal phase R3c(R c ), trigonal phase R3m(R m The phases consist of orthorhombic phase Amm2(O), tetragonal phase P4mm(T), and pseudocubic phase Pm-3m(PC), with a volumetric phase ratio of R at 25°C. c :R m The ratio of O:T:PC is 6.2:20.9:6.8:56.6:9.5, and the volume ratio at 120℃ is R. c :R m With a :O:T:PC ratio of 4.4:14.5:4.2:61.3:15.6, the material properties can reach: d 33 The rate of change Δd within the range of 25-120℃ 33 Less than 10%; Output current density at 25°C: I out =15.46μA / cm 2 Output current density at 120℃: I out =10.05μA / cm 2 A material system with excellent energy harvesting temperature stability was obtained, realizing the requirement for stable power generation of piezoelectric energy harvesters over a wide temperature range.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The lead-free material system designed and synthesized in this invention is a high-entropy five-phase coexisting polycrystalline phase structure with excellent piezoelectric charge constant d. 33 Temperature stability, at room temperature d 33 Based on ≥200pC / N, within a wider temperature range of 25-120℃, d 33 The rate of change is less than 10%, and the constructed piezoelectric energy harvester exhibits excellent output current density I within the temperature range of 25-120℃. out Its properties make it a potential lead-free piezoelectric ceramic material with excellent energy harvesting temperature stability.

[0018] (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

[0019] Figure 1 These are X-ray diffraction patterns of ceramic samples with different compositions according to the present invention.

[0020] Figure 2 The figures represent the phase ratios of different ceramic samples with varying compositions at room temperature and as a function of temperature, according to the present invention.

[0021] Figure 3 The images show scanning electron microscope (SEM) images and average grain size statistics of ceramic samples with different compositions according to this invention.

[0022] Figure 4 This is a graph showing the relationship between the piezoelectric charge constant and the normalized piezoelectric charge constant of ceramic samples with different compositions in this invention and temperature. Detailed Implementation

[0023] 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.

[0024] Example 1:

[0025] According to the chemical formula (1-0)[0.96(K) 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 The raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3, ZrO2, Fe2O3, BaCO3, TiO2, and MnO2 were weighed according to the stoichiometric ratio of [0.70BiFeO3-0.30BaTiO3+0.1mol%MnO2] and ball-milled in ethanol for 24 h. After drying, the mixture was calcined at 850℃ for 6 h; after a second ball milling and granulation, it was pressed into a green body at 100 MPa to obtain a green body, and then the green body was debinded at 560℃. Finally, it was sintered at 1120℃ and held for 3 h to obtain the target material.

[0026] Example 2:

[0027] According to the chemical formula 0.95[0.96(K) 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi)0.5 Na 0.5 The raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3, ZrO2, Fe2O3, BaCO3, TiO2 and MnO2 were weighed according to the stoichiometric ratio of [ZrO3] + 0.05[0.70BiFeO3-0.30BaTiO3+0.1mol%MnO2], and the rest were the same as in Example 1.

[0028] Example 3:

[0029] According to the chemical formula 0[0.96(K) 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 The raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3, ZrO2, Fe2O3, BaCO3, TiO2 and MnO2 were weighed according to the stoichiometric ratio of [ZrO3] + 1 [0.70BiFeO3-0.30BaTiO3+0.1mol%MnO2], and the rest were the same as in Example 1.

[0030] Table 1 Performance Comparison of the Above Embodiments

[0031]

[0032] Note: The temperature range is 25 to 120℃.

Claims

1. A lead-free high-entropy piezoelectric ceramic material having excellent energy harvesting temperature stability, characterized by, The base chemical composition of the lead-free piezoelectric ceramic material is: (1-x) [0.96(K 0.48 Na 0.52 )(Nb 0.96 Sb 0.04 )O3-0.04(Bi 0.5 Na 0.5 )ZrO3]+x[0.70BiFeO3-0.30BaTiO3+0.1mol% MnO2], wherein the value of x is 0.

05. The material system with x value of 0.05 has high configuration entropy ΔS = 1.46R, and has a polymorphic phase structure with five-phase coexistence: trigonal phase R3c (R c ), trigonal phase R3m (R m ), orthorhombic phase Amm2 (O), tetragonal phase P4mm (T) and pseudo-cubic phase Pm-3m (PC), and the volume phase ratio at 25°C is R c : R m : O : T : PC = 6.2:20.9:6.8:56.6:9.5, and the volume phase ratio at 120°C is R c : R m : O : T : PC = 4.4:14.5:4.2:61.3:15.6; 0.95[0.96(K 0.48 Na 0.52 )(Nb 0.96 Sb 0.04 )O3-0.04(Bi 0.5 Na 0.5 )ZrO3]+0.05[0.70BiFeO3-0.30BaTiO3+0.1mol% MnO2] material performance reaches: d 33 The change rate Δd 33 within 25-120°C is less than 10%; the output current density at 25°C is I out = 15.46 μA / cm 2 , the output current density at 120°C is I out = 10.05 μA / cm 2 , and a material system with excellent energy collection temperature stability is obtained, realizing the use requirements of stable power generation of a piezoelectric energy collector in a wide temperature range.

2. A method of producing the lead-free piezoelectric ceramic material according to claim 1, characterized by, Prepared by a common solid phase process, specifically comprising the following steps: (1) According to the molar ratio of each element in the chemical formula (1-x) [0.96(K 0.48 Na 0.52 )(Nb 0.96 Sb 0.04 )O3-0.04(Bi 0.5 Na 0.5 )ZrO3]+x[0.70BiFeO3-0.30BaTiO3+0.1mol% MnO2], raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3, ZrO2, Fe2O3, BaCO3, TiO2 and MnO2 are weighed, wherein the value of x is 0.05; (2) Put the weighed powder into a ball mill tank, and ball mill in a horizontal ball mill with anhydrous ethanol as medium for at least 24 h, and then dry to obtain the corresponding ceramic powder; (3) Granulate using a binder, press-form, then remove the binder, and sinter at 1120℃ for 3 h to obtain the ceramic material.

3. The method of claim 2, wherein, Granulate using a 5% polyvinyl alcohol aqueous solution as a binder, form under a pressure of 100 MPa, and remove the binder at 560℃.

4. The method of claim 3, wherein, The amount of the binder is 1 ml per 10 g of ceramic powder.

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