Study On Structure And Properties Of PZT/Polymer Piezoelectric Composites

Combining a piezoelectric ceramic and a polymer matrix to form a flexible composite with coupling properties in between that of two individual phases has received much attention. The developing trend of piezoelectric composites has been reviewed in this paper. And the influence of the molding technique, poling condition, piezoelectric ceramic, polymer and additive on the piezoelectric, dielectric, ferroelectric properties and the acoustic impedances of 0-3 piezoelectric composites are investigated systemically. The mechanism of polarization is explained and the optimal constitute is confirmed in terms of experimental results. It is found that the properties of PZT/PVC composites are better than that of PZT/PVDF composites, which is a noval material for the purpose of hydrophone applications.(1) The PZT/PVDF composites have been prepared by three kinds of molding technique, i.e., high-temperature-pressing, cold-temperature pressing and microwave irradiation technique. The results show that the composites prepared by microwave technique have the best interface, high-temperature-pressing technique secondly. The piezoelectric eomposites are prepared by microwave technique for the first time, not recorded by any reports. The microwave technique will have an enormous application, if the equipment could be perfected.(2) It is founded that the dielectric and piezoelectric properties of the PZT/polymer composites highly depend on poling field, temperature and time. Appropriate poling time is 30 min, poling temperature is 80¹00℃ and poling field is 10¹5 kV/mm.(3) The dielectric, piezoelectric and ferroelectric properties of PZT/polymer composites nonlinearly increase with the increase of PZT volume fraction. When the PZT volume fraction is larger than 50%, the composites show good properties. And the remanent polarization (P_r) of the composites increase rapidly and the coercive field (E_c) decrease because of 0-3(1-3) mixed connectivity pattern being formed. At the same time, the density and acoustic impendence (Z) of the composites increases rapidly.(4) With the increasing of PZT particle size, the piezoelectric strain constant d₃₃, dielectric constant ε_r electromechanical coupling coefficient K_p and K_t increase,mechanical quality Qm and Z decrease and the piezoelectric voltage constant g33 keeps constant. The P-E hysteresis loops show that Pr increases and Ec values decreases with larger PZT particle size. The smaller-ceramic-particle composites have high density and are easy to fabricate thin sheet with large area. The nearly monodispersed particle size of the piezoelectric ceramic particle is benefit to improve integrative properties of the composites.(5) When the PZT powders annealed at high temperature, the results of DSC and XPS measurement show that the surface energy of the high-temperature-treated PZT decreases and the crystal surfacial microstructure is optimized. The composites with the high-temperature-treated PZT powders are more homogeneous and dense. The composites have better dielectric, piezoelectric and ferroelectric properties, and its Z value is nearly independent of the treatment.(6) Three kinds of thermoplastic polymer have been used to prepare the PZT/polymer composites with hot-temperature-pressing technique. The results show that polymer matrix has much influence on the piezoelectric, dielectric, ferroelectric properties and acoustic impendence of the composites. The PZT/PVDF composites have higher eT and tg values than that of the other composites. The saturate P-E hysteresis loops show that, the Ec values of PZT/PVDF composites are lower than that of the PZT/PVC composites, and the PZT ceramic in the PZT/PVDF composites is easy to be poled. The PZT/PVC composites using nanocrystalline PVC have higher g33 values than that of the PZT/PVDF composites. Compared in three systems, The optimized electric properties were obtained in 0.5PZT/0.5PVC composite, showing d33=l5 pC/N, g33=42.6 mV-m-N'1, Kp=0.226, Z=11.25xl06kg-s'1-m"2, which is flexible enough for mechanical process.(7) The effect of molding temperature on the propertied of the 0.5PVC/0.5PZT composites are investiged. The optimal electric properties have been obtained in 0.5PZT/0.5PVC composite at molding temperature being 150 °C, showing ex =45.66 , tgï¿¡ = 0.0286,coupling agent can improves the PVC morphology, increase the the density and the properties of the composites. The composites with 0.5 wt% aluminate coupling agent have optimal electric properties.(9) The in situ PVC/PAn composites are prepared by aniline polymerizing in the presence of PVC powders in hydrochloric acid. The PAn/PVC composite prepared by in-site technique has lower conductivity than that of composite made by blend. The O.5PZT//PAn/(0.5-j9PVC composites using PAn/PVC composite made by in-site technique are prepared by hot^temperature-pressing technique. A small content PAn added with the composites improve the piezoelectric properties, the optimized electric properties can be obtained when/is 6 %.(10) The three-phase 0.5?ZT/jC/(0.5-J)?VC composites have been prepared by hot-temperature-pressing technique. The optimized electric properties has been obtained in 0.5PZT/0.005C/0.0495PVC composite, showing cfo=24.5 pC/N, g33= 55.8 mV-m-N"1, Kp=0.249, K,=0.245, Qw=19.66,...