Study of Pb(Zr _0.52 Ti _0.48 )O ₃ microelectromechanical system piezoelectric accelerometers for health monitoring of mechanical motors

In this study, piezoelectric Pb(Zr _0.52 Ti _0.48 )O ₃ (PZT) thick films were fabricated on Pt-coated Si substrates by a modified sol-gel method via dispersing the piezoelectric submicron powders of composition (Pb, Sr)La _x (Ti, Zr) _1-1/4x O ₃ (PZT-5A, having a high d ₃₃ value of 520 and a high k _p value of 0.64) in the PZT sol-gel solution. Then, piezoelectric microelectromechanical system (MEMS) accelerometers were designed and fabricated on Si substrates via micromachining techniques. A mathematic approximation model was firstly proposed. It used an effective thickness of Si membrane (h _eff ) to replace the thickness of Si membrane, derived by math theory. The resonant frequency using the mathematic approximation model would be closer to the values of the experimental data than using the original math theory. Finally, the self-made thick film accelerometers with best properties were fabricated via a modified sol-gel method. They had voltage sensitivities in the range of 2.21-2.14 mV/g, which is pretty high compared with the reported data, and the resonant frequency is in the range of 6.5-7.1 kHz. In addition, the accelerometers with amplifier circuit and power source were practically used in vibration detection of health monitoring of mechanical motors.