Papers by Author: Seung Hwan Yi

Abstract: 0.03Pb(Sb0.5Nb0.5)O3-0.03Pb(Mn1/3Nb2/3)O3-(0.94-x)PbTiO3-xPbZrO3 ceramics doped with CeO2 were synthesized by conventional bulk ceramic processing technique. Phases analysis, microstructures and piezoelectric properties were investigated as a function of CeO2 contents (0.03, 0.05, 0.1 0.3, 0.5 and 0.7wt%). Microstructures and phases information were characterized using a scanning electron microscope (SEM) and an X-ray diffractometer (XRD). Relative dielectric constant (K33 T) and coupling factor (kp) were obtained from the resonance measurement method. Both K33 T and kp were shown to reach to the maximum at 0.1wt% CeO2. In order to evaluate the stability of resonance frequency and effective electromechanical coupling factor (Keff) as a function of CeO2 addition under strong electric field, the variation of resonance and anti-resonance frequency were also measured using a high voltage frequency response analyzer(FRA5096) under various alternating electric fields from 10V/mm to 80V/mm. It was shown that effective electromechanical coupling factor was increased by increasing the CeO2 additions.

Abstract: This paper describes a micromachined piezoelectric bimorph microphone, which is built on a low stress Parylene diaphragm with high quality ZnO films. The ZnO thin film has fine grain with the average grain size less than 1
and the grain orientation is perpendicular to the substrate. The highest sensitivity of piezoelectric bimorph microphone fabricated in this study is about 0.74 mV/Pa, which is twice higher than that of an individual segmented electrode. Based upon the experimental results, we proposed the equivalent electrical circuit model of piezoelectric bimorph microphone.