| Summary: | 碩士 === 國立臺灣科技大學 === 材料科技研究所 === 94 === The x(Pb(Zn1/3Nb2/3 )O3 ) + (1-x)(Pb(Zr0.52Ti0.48 )O3) (PZNZT) ceramics, which were used in ultrasonic radar system, were investigated to improve the characteristics of the temperature coefficient of capacitance (TCC), piezoelectric and fatigue properties. Various compositions (x=0~0.5) of PZNZT systems were designed to control the phase transformation and relaxor behavior, and to reduce the TCC at the temperature range from 25℃ to 80℃. We found that PZNZT system at the composition of x=0.1 which has high curie temperature (384℃) can reduce the TCC to 72 ppm/℃, but the sintering temperature of the specimen is higher than 1150℃. In electrical properties, the composition of x=0.2 has a high electrical mechanical coupling coefficient of 71％, high remant polarization (Pr) of 40 μC/cm2 and low coercive field (Ec) of 11 kV/cm. Specimens at this composition show higher fraction of the tetragonal phase, and it will make domain hard to switch and induce larger Pr reduction than the specimens containing more rhombohedra phase (x=0.4-0.5) after fatigue tests. In these experiments, we know that PZNZT system having high kp, low TCC and low Qm, is suitable to use in low power ultrasonic sensor.
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