Preparation And Properties Of Piezoelectric Ceramic PLZT,Piezoelectric Polymer PVDF Film And Their Composites

Preparation and study of Nano(doped)Piezoelectric ceramics/Piezoelectric Polymer compositesNanocrystalline PLZT was prepared by sol-gel method. Preparation and study of rare earth element La doped PZT piezoelectric ceramics Pb(1-x)Lax(Zr0.52Ti0.48)O3 (PLZT). The influence of solvent ratio on the crystallization temperature of precursor PLZT and PLZT product size was investigated. We studied the formation and the decomposition and the crystallization of gels carefully. It was found that both were increased with increase of V(C3H8O2)/V(H2O) ratio. At V(C3H8O2)/V(H2O)=4.55 the gel was formed moderately quick, and the nanocrystalline PLZT with uniform granularity(60~70nm) and low crystallization temperature(475℃) could be obtained. According to the results of experiments sol-gel process has following merits compared solid state reaction in the aspect of preparing powders: the temperature of reaction is decreased, powders are fine and the dimension of powders is even.The phase transition of PVDF was studied by FT-IR, WAXD and DSC.Structural changes caused by compressional plastic deformation were probably due to chains higher packing, which results in more dense crystals. There are differences in samples stretched to a given stretch ratio at a certain temperature. The applied stress to the film results in alignment of polymer chains into the crystals so that all trans planar zigzag (TTT) conformation was induced into the crystals. This allows the dipoles on the polymer chains to align normal to the direction of the applied stress. The maximum b-phase content was obtained at 90 °C and at a stretch ratio of about 4.5–5. Stretch ratio affects b-phase content more than stretching temperature. In the preparation and study of piezocomposites, the piezoelectricity of composites increases with the increasing of polarizing voltage, polarizing time and polarizing temperature. But composites will be broken down if the polarizing voltage is too high, and the piezoelectricity will also decrease if the polarizing temperature is too high. Generally, the piezoelectricity of composites increases with the increasing of the ceramic content under the same polarizing condition. But it is not advantageous for the piezoelectricity of composites if the ceramic content ceramic is too high because hot molding will be difficult and the ability of enduring high voltage will decrease.