The Effects of Doping and Process Conditions on the Characterization of PbTiO3-based Ceramics and Its Applications on SAW Devices
| Autor: | Te-Yi Chen, 陳德一 |
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| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 Lead titanate (PbTiO3) family ceramics have large electromechanical coupling factor kt, where kt is larger than 50﹪, which can be utilized for the piezoelectric applications. By doping and properly varying the process parameters, it will improve the properties of the ceramics. In this research, effects of calcium, strontium and cadmium dopants on the piezoelectric and dielectric properties of Sm-modified PbTiO3 ceramics have been investigated. Sm-modified PbTiO3 ceramics were prepared by conventional mixed-oxide methods. We successfully showed that Ca, Sr and Cd additives are helpful to obtain much higher thickness electromechanical coupling coefficient, kt, than that of conventional PbTiO3 based ceramics and still keep small planar electromechanical coupling coefficient, kp. In addition, by properly varying the sintering and poling conditions, the samples with zero temperature coefficient of resonant frequency were fabricated. Microstructural and compositional analyses of these doped ceramics have been carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface acoustic wave (SAW) filters were fabricated using these ceramic substrates and the properties, including phase velocity and electromechanical coupling coefficient, were measured. Poly-crystal ZnO films with c-axis (002) orientation have been successfully grown on the lead-based ceramic substrates by r.f. magnetron sputtering technique. The deposited films were characterized as a function argon-oxygen gas flow ratio and r.f. power. Crystalline structures of the films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Highly oriented films with c-axis normal to the substrates can be obtained by depositing under a total pressure of 10mTorr containing 50% argon and 50% oxygen and r.f. power of 70W. The phase velocity, electromechanical coupling coefficient and temperature coefficient of frequency of SAW device with ZnO/IDT/PT (IDT: Inter-digital transducer; PT: PbTiO3 ceramics) structure were investigated. It shows that the preferred oriented ZnO film is beneficial for improving the electromechanical coupling coefficient of SAW device. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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