Study On Electrophoretic Deposition Process For Fabrication Of PZT Ceramic Thick Films

Fabrication of piezoelectric ceramic films on silicon wafer is becomingvery important for the applications in microelectromechanical systems(MEMS). Compared with other existing methods, electrophoretic deposition(EPD) is a promising, simple and cost-effective method for fabrication ofpiezoelectric ceramic thick films. In this study, commercial lead zirconatetitanate (PZT) powders were deposited onto Pt/Ti/SiO2/Si(100) substrates byusing electrophoretic deposition method in ethanol solution. A proper amountof HCl was added into the PZT slurry to introduce surface charges to PZTparticles to keep a stable suspension. The deposition behavior wasinvestigated under different applied voltages and deposition duration.Deposition quality and the relative density of each deposition were verifiedby microstructural examination using a scanning electron microscope (SEM).It was found that the surface quality was satisfactory as the applied electricfield were 50V/cm in 15min. The deposited microstructure gradually changedacross the film thickness. Such a phenomenon was explained by using DLVOtheory.In order to sinter the deposited PZT films at low temperature, aliquid-phase sintering aid consisting of Cu2O-PbO eutectic compound wasadded into the PZT starting powder. The stability of the suspension and thedeposition quality of the as-deposited thick film of the PZT powder withsintering aids were investigated by changing the amount of HCl and theapplied electric field. It was found that the surface quality was satisfactory asthe applied electric field were 30V/cm in 5min. The above sintering aid iseffective in reducing the sintering temperature. Furthermore, sol infiltrationstechnique was proposed to combine with EPD to obtain dense thick PZT filmsat low temperature. Using the combined process, a dense crack-free anduniform PZT thick film was achieved at 750℃. Phase development of thePZT thick films was analyzed by X-ray diffraction, which indicated that thePZT films were of perovskite phase. A polarization hysteresis and dielectricparameters for the sintered and EPD-derived PZT films were measured toshow the ferroelectric properties of the obtained PZT films. The PZT thickfilm sintered for 2h showed a better property than that for 0.5h at the same750℃.