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Medium damping influences on the resonant frequency and quality factor of piezoelectric circular microdiaphragm sensors

Medium damping influences on the resonant frequency and quality factor of piezoelectric circular microdiaphragm sensors (PCMSs) are investigated theoretically and experimentally in this paper. The acoustic radiation and viscosity damping as the two main sources of energy dissipation in a medium virtually added the mass of the diaphragm and therefore decrease the frequency and Q-factor of the diaphragm. The magnitude of medium damping inversely depends on the radius-to-thickness ratio. An increase in this ratio is the trend in the fabrication of thin microdiaphragms by MEMS fabrication processes, which implies the higher influence of medium damping on the dynamic behavior of microdiaphragms. The fabricated PCMSs were tested in vacuum, air, and ethanol. The Q-factor and the resonant frequency of the device increase by almost seven times, 4.7% from air to 0.05 atmpressure, respectively. The Q-value drops from 111.195 in air to 23.908 in ethanol. Throughout this work, theoretical and experimental values were compared and a fairly good correlation was observed.