Title Page
Contents
초록 10
Abstract 12
1. Introduction 14
2. Literature review 19
2.1. Overview of Bi₀.₅Na₀.₅TiO₃(BNT) 19
2.2. Dielectric mechanisms 21
2.3. Dielectric constant 24
2.4. Fundamental Principle of Energy Storage of dielectric materials 27
3. Methodology 29
3.1. Synthesis process of BNT 29
3.2. Characterization tools 35
3.2.1. X-Ray Diffraction (XRD) Study 35
3.2.2. Scanning Electron Microscopy (SEM) 35
3.2.3. Zetasizer nano-size measurement 36
3.2.4. Sintering 37
3.2.5. Density measurement 37
3.2.6. Dielectric constant and loss measurement 38
4. Results and discussion 40
4.1. Phase formation 40
4.2. Microstructure and particle size analysis of calcined samples 43
4.3. Sintering and density 47
4.4. Microstructure of sintered samples 49
4.5. Dielectric properties analysis 51
5. Conclusion 54
References 55
Table 3.1. Starting materials used in the synthesis of BNT 31
Table 4.1. Density measurement of BNT ceramic samples 47
Table 4.2. Grain size of BNT sintered samples 50
Fig. 1.1. (a) An electric charge is produced by the direct piezoelectric effect when mechanical strain is applied whereas (b), the inverse piezoelectric effect explains the circumstance in which... 15
Fig. 1.2. Publications in peer-reviewed journals throughout the past ten years (2012-2022) on lead-free piezoelectric ceramics. The "ISI Web of Science" database is the source of the statistics... 16
Fig. 2.1. Representation of the unit cell of BNT perovskite. 19
Fig. 2.2. frequency response of dielectric mechanisms 21
Fig. 2.3. Dipole rotation in electric field 22
Fig. 2.4. Parallel plate capacitor, DC case 24
Fig. 2.5. Parallel plate capacitor, AC case 25
Fig. 2.6. Tangent loss vector diagram 26
Fig. 3.1. Top-down and Bottom-up methods for nanoparticle synthesis. 29
Fig. 3.2. Schematic diagram of BNT synthesis by wet precipitation process. 32
Fig. 3.3. Schematic diagram of BNT synthesis by solid-state reaction process. 34
Fig. 4.1. XRD patterns of the BNT powders synthesized by Wet precipitation method and calcined at different temperature (400℃, 500℃, 600℃, 700℃ and 800℃) 41
Fig. 4.2. XRD patterns of the BNT powders synthesized by solid state method and calcined at 500℃, 600℃ and 700℃. 41
Fig. 4.3. SEM images of BNT powder samples synthesized by wet precipitation and calcined at 500℃ (a and b), 600℃ (c and d), 700℃ (e and f), and 800℃ (g and h). 45
Fig. 4.4. Particle size analysis of BNT powders calcined at 600℃ and 700℃. 46
Fig. 4.5. Relative density with respect to sintering temperatures. 48
Fig. 4.6. SEM images of BNT ceramic samples prepared by wet precipitation (a and b), and solid- state reaction (c and d) and sintered at 1000℃ (a and c) and 1050℃ (b and d). 49
Fig. 4.7. Dependence on temperature of the dielectric constant and dielectric loss (tan δ) of BNT samples prepared by wet process and sintered at (a) 1000℃ and (b) 1050℃ for 3 h. 52