Ⅰ. INTRODUCTION 1 1.1 Research Background 1 1.2 Piezoelectricity 2 Ⅱ. TRANSPARENT PIEZOELECTRIC LOUDSPEAKER 5 2.1 Introduction 5 2.1.1 Transparent electronics 5 2.1.2 Transparent piezoelectric materials 6 2.1.3 Piezoelectric loudspeaker 8 2.1.4 Research objective 9 2.2 Materials and Methods 11 2.2.1 Fabrication process of PLZT ceramics 11 2.3. Result and discussion 13 2.3.1 Material properties of PLZT ceramics 13 2.3.2 A transparent piezoelectric PLZT transducer with a glass diaphragm 17 2.3.3 A piezoelectric transparent PLZT loudspeaker with a PET diaphragm 20 Ⅲ. MULTI FREQUENCY PIEZOELECTRIC MICROMACHINED ULTRASOUND TRANSDUCER (PMUT) 25 3.1 Introduction 25 3.1.1 Background 25 3.1.2 Ultrasound transducer 26 3.1.3 Advantage of Broadband ultrasound transducer for ultrasound imaging 27 3.1.4 State of art for improving bandwidth of PMUT 28 3.1.5 Research objective 30 3.2 Design and fabrication 31 3.2.1 Design of a single cell PMUT 31 3.2.2 Design of Multi Frequency PMUT array 34 3.2.3 Fabrication process of Multifrequency PMUT 35 3.3 Characterization of Multifrequency PMUT 37 3.3.1 Image and Material properties of PMUT 37 3.3.2 Mechanical characterization of PMUT in the air 40 3.3.3 Acoustic characterization of PMUT in the water 42 Ⅳ. CONCLUSION 46 REFERENCES 48 요약문 54
