A lead-free piezoelectric energy harvesting ceramic material system with stable output voltage and controllable output current and its preparation method

Abstract

A lead-free piezoelectric energy harvesting ceramic material system with stable output voltage and controllable output current and its preparation are disclosed, belonging to the field of piezoelectric ceramic materials. The matrix chemical composition of this ceramic material is (1-x)(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-x(Bi) 0.5 Na 0.5 ZrO3 with x values ​​of 0.015, 0.03, and 0.04 exhibits stable output voltage and progressively increasing output current density in these three systems. Samples are prepared by wet grinding, drying, granulation, pressing, and sintering according to the corresponding stoichiometric ratios. This invention achieves stable output voltage and controllable output current density within the same lead-free piezoelectric ceramic material system, significantly advancing piezoelectric energy harvesting technology.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramic materials, specifically relating to a lead-free piezoelectric energy harvesting ceramic material system with stable output voltage and controllable output current density and its preparation. Background Technology

[0002] With the development of 5G technology, smart cities have emerged. Smart homes, smart healthcare, and smart transportation, ubiquitous in daily life, are important hallmarks of smart cities in the 5G Internet of Things era. Smart cities are home to tens of thousands of miniature sensors, and building a self-powered network sensing system is beneficial for further improving and developing smart cities. Compared to ecological energy sources such as solar, wind, and tidal power, piezoelectric energy harvesting technology has advantages such as less susceptibility to natural environmental influences, high power density, small size, ease of manufacturing, and integrability. It is considered one of the power sources for new electronic devices in smart cities and has received widespread attention and rapid development in recent years.

[0003] Over the past two decades, extensive research has been conducted on piezoelectric energy harvesting technology, resulting in significant progress. The output voltage of piezoelectric energy harvesters has become adjustable within the range of tens to hundreds of volts, meeting the requirements of most micro-sensors. However, low output current density and difficulty in controlling it remain bottlenecks for practical applications. Therefore, designing piezoelectric energy harvesters with stable output voltage and controllable output current density to meet the functional requirements of different micro-sensors is of significant practical importance. Moreover, low output current density is a bottleneck that piezoelectric energy harvesters urgently need to overcome; currently, there is still a lack of research on constructing piezoelectric energy harvesters with stable output voltage and high output current density. Piezoelectric ceramic materials are the core component of piezoelectric energy harvesting devices. Achieving stable output voltage and controllable output current density within the same piezoelectric material system would have significant industrial value and developmental implications for industrial production and practical applications.

[0004] The output voltage (V) of the piezoelectric energy harvester out It is related to the piezoelectric voltage constant (g) 33 ), and g 33 It can be represented as:

[0005]

[0006] Where ε0 is the vacuum permittivity, ε r is the relative permittivity.

[0007] The output current (I) of the piezoelectric energy harvester out It is related to the piezoelectric charge constant (d) 33 ), can be represented as:

[0008]

[0009] Where, d 33 Let F be the piezoelectric charge constant, F be the force, and t be the time.

[0010] According to classical phenomenological theory, d 33 It can also be expressed as:

[0011] d 33 =2ε0ε r P s Q 33 (3)

[0012] Among them, P s Q represents the spontaneous polarization intensity. 33 is the electrostriction coefficient.

[0013] Combining formulas (1) and (3), g 33 It can also be expressed as:

[0014]

[0015] Therefore, to achieve a stable output voltage and controllable output current density, the piezoelectric ceramic material system needs to have a stable g-axis. 33 And the gradually increasing d 33 That is, the gradually increasing P s and gradually decreasing Q 33 To maintain g 33 The P level is stable and gradually increases. s and ε r To obtain a gradual increase in d 33 .

[0016] Currently, lead-based piezoelectric ceramics are the main materials used in piezoelectric energy harvesting technology. However, due to the toxicity of lead, which poses serious threats to the ecological environment and human health, finding lead-free piezoelectric ceramics to replace lead-based materials is a current research hotspot. Potassium sodium niobate (KNN)-based lead-free piezoelectric ceramics have received widespread attention in recent years due to their abundant phase boundaries and ideal piezoelectric properties. By altering the phase boundary structure of KNN-based ceramics, the electrical properties of the material can be controlled. Therefore, to construct a KNN-based ceramic system with stable output voltage and controllable output current density, this invention, through precise composition control, constructs a series of materials with different proportions of trigonal-orthorhombic-tetragonal (ROT) polycrystalline phase boundaries. On the one hand, P in the system... s The gradual increase and Q 33 The gradual decrease of co-modulation produces a stable g 33 This results in a stable output voltage; on the other hand, P in the systems and ε r Gradually increasing, d was obtained. 33 This allows for a gradual increase in output current density. Ultimately, a KNN-based piezoelectric energy harvesting ceramic material system with stable output voltage and controllable output current density is obtained. Summary of the Invention

[0017] The purpose of this invention is to provide a KNN-based ceramic system with stable output voltage and controllable output current density, and its preparation method. The prepared lead-free piezoelectric ceramic simultaneously possesses stable g 33 and gradually improving d 33 The power generation characteristics were characterized using a cantilever beam energy harvester. To achieve a stable output voltage and controllable output current density, this invention prepared a series of trigonal-orthogonal-tetragonal (ROT) polycrystalline phase boundary materials with different proportions through compositional control. On one hand, the Q... 33 The gradual decrease and P s The gradual increase of g together modulates a stable g 33 This achieves a stable output voltage; on the other hand, P in the system s and ε r Gradually increasing, d was obtained. 33 This allows for a gradual increase in output current density.

[0018] To achieve the above objectives, the present invention adopts the following technical solution.

[0019] The lead-free piezoelectric material system of the present invention, characterized by having a stable output voltage and controllable output current density, is characterized by the following matrix chemical composition:

[0020] (1-x)(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-x(Bi) 0.5 Na 0.5 For ZrO3, with x values ​​of 0.015, 0.03, and 0.04, the output voltage is stable in these three systems, while the output current density gradually increases with increasing x. The output voltage V... out =21.3±0.2V, output current density I out The range is 6.09-20.16 μA / cm. 2 .

[0021] The lead-free piezoelectric material system with stable output voltage and controllable output current density described above in this invention is prepared by a conventional solid-state process, specifically including the following steps:

[0022] (1) According to the chemical formula (1-x)(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-x(Bi) 0.5 Na 0.5 The molar ratio of each element in ZrO3 is determined by weighing the raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3 and ZrO2, where the values ​​of x are 0.015, 0.03 and 0.04.

[0023] (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.

[0024] (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.

[0025] (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 1140℃, held for 3 hours, and cooled to room temperature in the furnace to obtain the target material.

[0026] The prepared lead-free piezoelectric material was first subjected to surface polishing and microstructure testing. Then, a silver electrode was coated and artificially polarized (e.g., in silicone oil at 100°C, at 40 kV·cm⁻¹). -1 The samples were polarized at a given voltage for 30 minutes, then aged at room temperature for 24 hours, and their piezoelectric properties were tested. Finally, the power generation performance was tested using a cantilever beam energy harvester.

[0027] Through meticulous composition design and sintering process, a dense ceramic sample was obtained, in which 0.985 (K) 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.015(Bi) 0.5 Na 0.5 ZrO3, the material properties can reach: ε r =1152, P s =18.5μC / cm 2 d 33 =160pC / N, Q 33 =0.023m 4 / C 2 g 33 =15.54(×10 -3 Vm / N), power generation performance at room temperature: output voltage V out =21.3V, output current density I out =6.09μA / cm 2 ; 0.97(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 )O3-0.03(Bi 0.5 Na 0.5 ZrO3, the material properties can reach: ε r =1548, P s =23.4μC / cm 2 d 33 =213pC / N, Q 33 =0.021m 4 / C 2 g 33 =15.69(×10 -3 Vm / N), power generation performance at room temperature: output voltage V out =21.5V, output current density I out =13.12μA / cm 2 ; 0.96(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 ZrO3, the material properties can reach: ε r =1975, P s =25.7μC / cm 2 d 33 =319pC / N, Q 33 =0.018m 4 / C 2 g 33 =15.54(×10 -3 Vm / N), power generation performance at room temperature: output voltage V out =22.1V, output current density I out =20.16μA / cm 2 It can meet the usage requirements of different micro sensors.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The lead-free piezoelectric material system of the present invention has a stable output voltage and a controllable output current density. On the one hand, P in the system s The gradual increase and Q 33 The gradual reduction of co-modulation produces a stable g 33 This achieves a stable output voltage; on the other hand, P in the system s and ε r Gradually increasing, d was obtained. 33 This allows for a gradual increase in output current density and represents a potential lead-free piezoelectric ceramic material system that can be applied to power various sensors.

[0030] (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 energy, and is energy-saving, environmentally friendly, and safe, with significant economic and social value. Attached Figure Description

[0031] Figure 1 The X-ray diffraction patterns and phase contents of ceramic samples with different compositions are shown in this invention.

[0032] Figure 2 The dielectric temperature curves and dielectric constants of ceramic samples with different compositions are shown in this invention.

[0033] Figure 3 The figures represent the hysteresis loops and spontaneous polarization intensities of ceramic samples with different compositions in this invention.

[0034] Figure 4 The strain-polarization curves and electrostriction coefficients of ceramic samples with different compositions are shown in this invention.

[0035] Figure 5 This represents the piezoelectric charge constant of ceramic samples with different compositions in this invention.

[0036] Figure 6 This represents the piezoelectric voltage constant of ceramic samples with different compositions according to the present invention.

[0037] Figure 7 The output voltage and output current density of ceramic samples with different compositions in this invention are shown. Detailed Implementation

[0038] 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.

[0039] Example 1:

[0040] According to the chemical formula 0.985 (K 0.48 Na 0.52 (Nb)0.96 Sb 0.04 O3-0.015(Bi) 0.5 Na 0.5 The ZrO3 was prepared by weighing out raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3, and ZrO2, and ball milling them in ethanol for 24 hours. The mixture was then dried and calcined at 850℃ for 6 hours. After a second ball milling and granulation, it was pressed into a green body at 100 MPa, and then the green body was debinded at 560℃. Finally, it was sintered at 1140℃ for 3 hours to obtain the target material.

[0041] Example 2:

[0042] According to the chemical formula 0.97 (K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 )O3-0.03(Bi 0.5 Na 0.5 The ZrO3 stoichiometric ratio is as follows: weigh out the raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3 and ZrO2, and other parameters are the same as in Example 1.

[0043] Example 3:

[0044] According to the chemical formula 0.96 (K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 The ZrO3 stoichiometric ratio is as follows: weigh out the raw materials K2CO3, Na2CO3, Nb2O5, Sb2CO3, Bi2O3 and ZrO2, and other parameters are the same as in Example 1.

[0045] Table 1 Performance Comparison of the Above Embodiments

[0046]

[0047]

Claims

1. A lead-free piezoelectric energy harvesting ceramic material system with stable output voltage and controllable output current density, characterized in that, The material system is (1-x)(K) 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 )O3-x(Bi 0.5 Na 0.5 The values ​​of x for ZrO3 are 0.015, 0.03, and 0.04, 0.985 (K). 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.015(Bi) 0.5 Na 0.5 ZrO3, material properties reach: ε r = 1152, P s = 18.5 μC / cm 2 d 33 = 160 pC / N, Q 33 = 0.023 m 4 / C 2 g 33 = 15.54 (×10 -3 Power generation performance at room temperature (Vm / N): Output voltage V out = 21.3, output current density I out = 6.09 μA / cm 2 ; 0.97(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 )O3-0.03(Bi 0.5 Na 0.5 ZrO3, material properties reach: ε r = 1548, P s =23.4 μC / cm 2 d 33 = 213 pC / N, Q 33 = 0.021 m 4 / C 2 g 33 = 15.69 (×10 -3 Power generation performance at room temperature (Vm / N): Output voltage V out = 21.5 V, output current density I out = 13.12 μA / cm 2 ; 0.96(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 O3-0.04(Bi) 0.5 Na 0.5 ZrO3, material properties reach: ε r = 1975, P s = 25.7 μC / cm 2 d 33 =319 pC / N, Q 33 = 0.018 m 4 / C 2 g 33 = 15.54 (×10 -3 Power generation performance at room temperature (Vm / N): Output voltage V out = 22.1 V, output current density I out = 20.16 μA / cm 2 This meets the power supply requirements of miniature sensors with the same driving voltage but different driving current specifications.

2. The lead-free piezoelectric energy harvesting ceramic material system with stable output voltage and controllable output current density according to claim 1, characterized in that, The material system with an x ​​value of 0.015 has a trigonal-orthorhombic-tetragonal (ROT) polymorphic phase boundary with a phase structure ratio of R:O:T = 41:36:23; the material system with an x ​​value of 0.03 has a trigonal-orthorhombic-tetragonal (ROT) polymorphic phase boundary with a phase structure ratio of R:O:T = 39:34:27; the material system with an x ​​value of 0.04 has a trigonal-orthorhombic-tetragonal (ROT) polymorphic phase boundary with a phase structure ratio of R:O:T = 31:33:

36.

3. A method for preparing the lead-free piezoelectric ceramic material according to claim 1, characterized in that, It is prepared by a conventional solid-state process, specifically including the following steps: (1) According to the chemical formula (1-x)(K 0.48 Na 0.52 (Nb) 0.96 Sb 0.04 )O3-x(Bi 0.5 Na 0.5 The molar ratio of each element in ZrO3 is determined by weighing the raw materials K2CO3, Na2CO3, Nb2O5, Sb2O3, Bi2O3 and ZrO2, where the values ​​of x are 0.015, 0.03 and 0.

04. (2) Place the weighed powder into a ball mill jar, and ball mill it in a horizontal ball mill for at least 24 hours with anhydrous ethanol as the medium. Then dry it to obtain the corresponding ceramic powder. (3) Then, granulation is carried out using a binder, and the mixture is pressed into shape. Then, the binder is removed, and the mixture is sintered at 1140 °C for 3 hours to obtain ceramic material.

4. The method according to claim 3, characterized in that, A 5% (w / w) aqueous solution of polyvinyl alcohol was used as a binder for granulation, which was then molded under a pressure of 100 MPa and the binder was removed at 560 °C.

5. The method according to claim 4, characterized in that, The amount of binder used is 1 ml of binder for every 10 g of ceramic powder.

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