Investigation On Electrohydrodynamic Jet Deposition Of PZT Thick Films

PZT thick films have high piezoelectric property, electromechanical coupling coefficient, and have an extensive prospect in high-performance micro device such as high frequency ultrasonic sensors, micro transducer and micro deformable mirror. Preparation of film using electrohydrodynamic jet deposition (EJD) technology presents several advantages such as relatively high deposition rate, strong controllability of film structure.In this work, EJD technology combined with PZT composite slurry was used to prepare PZT thick films. Firstly, the effect of EJD parameters and slurry mixing condition on the compactness of PZT thick films were examined. Sol infiltrating thick films was also studied. Secondly, polishing was used to smooth the surface of thick films prepared by EJD. The effects of surface roughness and thickness on the piezoelectric property of thick films were examined. Finally, PZT thick films deposited on the flexible substrates were studied.Firstly, PZT composite slurry was prepared, EJD technology combined with PZT composite slurry was used to prepare PZT thick films on silicon substrate. The effect of EJD working distance, flow rate and slurry mixing condition on the compactness of PZT thick films were examined. The reduction of working distance and flow rate can reduce the pore size and lead a denser PZT thick film. Mixing PZT composite slurry using ball-milling method can significantly improve the compactness of the deposited thick films. Crack-free PZT thick films were deposited. In order to further improve the density of thick films, Sol infiltrating thick films was studied, the compactness of PZT thick films significantly improved after sol infiltration.Secondly, mechanical polishing of thick films prepared by EJD was researched. The surface roughness of PZT thick films reduced from 422 nm to 23 nm after mechanical polishing. The effects of surface roughness and thickness on the piezoelectric property of thick films were examined. The reduction of surface roughness contributed to the improvement of piezoelectric property of PZT thick films. Thick films’ piezoelectric property improved with the increase of film thickness when the film thickness between 10μm and 60μm. The piezoelectric property of thick films had no obvious change when the film thickness between 60μm and 80μm. Piezoelectric property dramatic declined when the film thickness was higher than 80μm. The piezoelectric constant of d33 was 91pC/N when the thickness of PZT film was 68μm.Finally, PZT thick films were deposited on the flexible substrates of iron-nickel alloy and stainless steel. Double layer deposition method was used to solve the bending of flexible substrate after sintering. Flexible substrate/PZT thick films composite components were obtained, and integrated in piezoelectric vibration energy harvester and electromagnetic vibration energy harvester.