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High-Performance Piezoelectric Ceramic in Ternary System and Their Application of Energy Harvester Converged with Metamaterial

  • Tae-Gon Lee (이태곤, KU-KIST융합대학원 NBIT융합전공)

초록/요약

PbZrO3-PbTiO3-Pb(Ni1/3Nb2/3)O3 (PZ-PT-PNN) ternary system was investigated in three different concept; i) near the triple point composition, ii) characteristics of pseudocubic phase, and iii) high-performance ceramics for application. In the 1st investigation, the 0.16PZ-0.34PT-0.5PNN ceramic was determined as a triple point composition including rhombohedral, tetragonal, and pseudocubic phases and it exhibited a large d33, kp and εT33/εo values of 855 pC/N, 0.68 and 5800, respectively. However, its g33 and d33 × g33 values were relatively small because of its large εT33/εo. Similar results were obtained for specimens with rhombohedral-tetragonal (R-T) or pseudocubic-tetragonal (P-T) morphotropic phase boundary (MPB) compositions. However, specimens with a rhombohedral structure near the R-T MPB exhibited large g33 and d33 × g33 values because of their large d33 and small εT33/εo values that can be explained by their polarization characteristics. In order to determine characteristics of pseudocubic phase, various piezoelectric phases of PZ-PT-PNN ceramics near the triple point composition were further investigated (2nd investigation). The pseudocubic phase, which formed near the triple point composition, disappeared with increase in the PbZrO3 content. The structure of pseudocubic phase was similar to the R3m rhombohedral structure. The T-P MPB structure was developed during the tetragonal-to-cubic phase transformation. However, the rhombohedral phase directly transformed to the cubic phase because the structure of pseudocubic phase was similar to the rhombohedral structure. The specimens with pseudocubic phase and the specimens near pseudocubic phase exhibited nano-sized domains and small coercive electric fields, revealing their low domain wall energies. In addition, these specimens exhibited second-order ferroelectric-to-paraelectric phase transition and low Curie temperatures, confirming their low domain wall energies. The enhanced dielectric and piezoelectric properties of these specimens near the pseudocubic phase could be attributed to their low domain wall. However, the PZ-PT-PNN ceramics near the pseudocubic phase have low g33 and d33 × g33 values were relatively small because of its large εT33/εo In the 3rd investigation, high-performance PT-PT-PNN ceramics were studied in R-T MPB regions. Among the ceramics, 0.32PZ-0.39PT-0.29PNN exhibited the largest g33 of 43 × 10-3 V·m/N and d33 × g33 of 25.2 × 10-12 m2/N. Brief cantilever-type piezoelectric energy harvester (PEH) were constructed by using the (1-x-y)PZ-xPT-yPNN ceramics with 0.38 ≤ x ≤ 0.41 and y = 0.29 including the optimum composition to confirm effect of piezoelectric properties; whether better piezoelectric properties can make better output performances of application. The output power densities of PEH showed relationship with the k312 × d31 × g31 value of the piezoelectric ceramics and the optimum piezoelectric ceramic (0.32PZ-0.39PT-0.29PNN) exhibited the large output power density. By using the developed PZ-PT-PNN ceramics, metamaterial-assisted piezoelectric energy harvester (MPEH) was developed as a converging research and investigations of MPEH output performances were conducted in terms of design effects of PEH. Two-dimensional 5×11 phononic crystal supercell structure was used for the metamaterial, which focuses the input mechanical wave to the piezoelectric ceramic. The input mechanical wave is expected to produce a large strain inside the piezoelectric ceramic when the diameter of piezoelectric ceramic is similar or slightly smaller than the half-wavelength of the incident mechanical wave (9.5 mm). Hence, the MPEH with a piezoelectric ceramic of 8.0 mm diameter shows a largest output power. The output power of MPEH is also influenced by the thickness of the piezoelectric ceramic. The output power of MPEH decreases with the increase of the impedance difference between the aluminum plate and bi-layer consisted of the piezoelectric ceramic with the aluminum plate. This impedance difference increases with the increase of the thickness of piezoelectric ceramic and thus transmitted mechanical energy to PEH is decreased. Consequently, the optimum thickness of ceramic for output power and output power density was obtained as 2.0 mm. Moreover, the MPEH exhibits the largest output power when the soft piezoelectric ceramic having a large d33 × g33 value is used for the MPEH, probably because the MPEH is operated at the off-resonance condition. The MPEH, which uses a soft piezoelectric ceramic with 8.0 mm diameter and 2.0 mm thickness, exhibits a large output power of 2.7 mW and it is 25 times larger than the output power of a piezoelectric energy harvester without metamaterial. In addition, the MPEH output performances succeed to light up large number of LEDs.

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목차


Chapter 1. Introduction 1
Chapter 2. Literature Survey 4
2-1. Piezoelectricity 4
2-1-1. Definition and Principle 4
2-1-2. Ferroelectrics 6
2-1-2-1. Polarization and Domain 6
2-1-2-2. Thermodynamics 10
2-1-2-2-1. Curie-Weiss Law 11
2-1-2-2-2. First-Order Transition 12
2-1-2-2-3. Second-Order Transition 16
2-1-3. Properties 20
2-1-3-1. Tensor 20
2-1-3-2. Piezoelectric Constants 22
2-1-3-3. Permittivity and Dielectric Constant 25
2-1-3-4. Resonance and Anti-Resonance Frequencies with Phase Angle 27
2-1-3-5. Electro-Mechanical Coupling Factor 33
2-1-3-6. Mechanical Quality Factor 35
2-2. Piezoelectric Material 38
2-2-1. Crystal Structure 38
2-2-2. Morphotropic Phase Boundary 40
2-2-3. Lead-Free Ceramics 43
2-2-4. Lead-Based Ceramics 47
2-2-4-1. PZ and PT Ceramics 47
2-2-4-2. Relaxor Ceramics 48
2-2-4-3. Solid Solution System 49
2-3. Piezoelectric Applications 52
2-3-1. Actuator 52
2-3-2. Energy Harvester 33
2-4. Metamaterial 54
2-4-1. Definition 54
2-4-2. Applications 55
2-4-3. Wave Accumulation 56
2-4-3-1. Gradient-Index Lens 56
2-4-3-2. Phononic and Photonic Crystal 57
2-4-4. Mechanical Impedance 59
Chapter 3. Experimental Procedure 60
3-1. PZ-PT-PNN Piezoelectric Ceramic 60
3-1-1. Synthesis and Fabricating Process 60
3-1-2. Property Measurements 62
3-1-2-1. Structural Properties 62
3-1-2-2. Piezoelectric Properties 63
3-1-3. Cantilever-Type Piezoelectric Energy Harvester 64
3-2. Metamaterial Assisted Piezoelectric Energy Harvester 65
3-2-1. Metamaterial 65
3-2-1-1. Structure Design 65
3-2-1-2. Simulation 67
3-2-1-3. Fabrication 67
3-2-2. Piezoelectric Energy Harvesting Specimen 68
3-2-2-1. Fabrication 68
3-2-2-2. Property Measuring 69
3-2-3. Piezoelectric Energy Harvester with Metamaterial 70
3-2-3-1. Measuring Procedure 70
3-2-3-2. Light-up LEDs 72
Chapter 4. Results and Discussion 73
4-1. PZ-PT-PNN Ternary System 73
4-1-1. Near Triple-Point Composition 73
4-1-1-1. Structural Properties 73
4-1-1-2. Piezoelectric Properties 82
4-1-1-3. Property Characteristics of Phases and MPB 88
4-1-2. Pseudocubic Phase with Low Domain Wall Energy 94
4-1-2-1. Structural Properties 94
4-1-2-2. Piezoelectric Properties 103
4-1-2-3. TEM Analysis for Domain Structure 107
4-1-2-4. Domain Wall Energy Analysis with P-E Curves 110
4-1-2-5. Interpretation of Domain Wall Energy 113
4-1-3. High-Performance Ceramics in R-T MPB Region 118
4-1-3-1. Structural Properties 118
4-1-3-2. Piezoelectric Properties 121
4-1-3-3. Output Performances of Cantilever-Type Energy Harvester 124
4-1-3-4. Effect of Piezoelectric Properties for Performance of Energy Harvester 127
4-2. Metamaterial Assisted Piezoelectric Energy Harvester 131
4-2-1. Performance of Metamaterial 132
4-2-1-1. Band Structure of Phononic Crystal 132
4-2-1-2. Wave Propagation Simulation 134
4-2-1-3. Elastic Wave Localization 136
4-2-1-4. Experimental Visualization of Elastic Wave 137
4-2-2. Effect of Geometric Properties of Harvesting Specimens 139
4-2-2-1. Output Performances with Various Diameters 139
4-2-2-2. Output Performances with Various Thicknesses 143
4-2-3. Effect of Material Properties of Harvesting Specimens 149
4-2-3-1. Structure and Piezoelectric Properties of Harvesting Specimens 149
4-2-3-2. Output Performances with Various Material 153
4-2-4. Amplification Ratio of Output Power 158
4-2-5. Light-up LEDs by MPEH 161
Chapter 5. Conclusions 163
5-1. PZ-PT-PNN Ternary System 163
5-2. Metamaterial Assisted Piezoelectric Energy Harvester 166
References 169

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