Micromachined Piezoelectric Ultrasonic Transducer Force Electrical Properties Studies

In this dissertation, we will do some researches to the static deformation of the piezoelectric micromachined ultrasonic transducers (pMUTs). Presently piezoelectric ultrasonic transducers are widespread used in all kinds of domain, such as medical imaging method, telemetry technology, imaging information acquisition for robots and so on. Traditional transducer is limited to its size.So that will be to expensive to machine into two-dimensional transducer arrays. And this transducer arrays will be too heavy and unwieldy. The piezoelectric micromachined ultrasonic transducers, by contrast, are light weight,small in size, low inertial mass, short response time. These advantages are incomparable for traditional transducers.The piezoelectric micromachined ultrasonic transducers we researched consist of a piezoelectric layer, a passive layer, top electrode layer and bottom electrode layer. The thickness of the transducer membrane is in micron scale, so we should use theory of strain gradient to evaluate the static deformation. In this degree paper, we used the Couple Stress theory. Because of piezoelectric effect the membrane was bent when the external electric field applied. If the external electric field is strong enough the electrostricitive character must be considered. And the electrostricitive character is directly proportional to even number power of electric field strength. Research the static deformation will be great value for optimize the performance of the transducers.The results show that the optimal value for the ratio of the top electrode diameter and the membrane diameter is around 0.673, and the ratio is not dependent on any other parameters if the thickness of the two electrodes can be negligible compared to the piezoelectric and passive layers. As the size dependence of the membrane deformationThe optimal value of the ratio for the passive layer and the piezoelectric layer should be bigger than 1.0. when a strong external electric field is applied the nonlinearity of the piezoelectric layer will increase by the increase of the electric field. That means the membrane rigidity has a downward trend when the electric field increased.