Preparation And Research Of PZT Ferroelectric Films

When PZT film is prepared, organic- alkoxides are usually used to produce PZT sol, among which Zr- alkoxide is expensive and has rigorous request for equipment. However, inorganic zirconium have no these disadvantages. On the other hand, when thinking for the substrates, the Si/SiO₂/Ti/Pt multiplayer substrate is used to prepare films. It is a high cost and complex process. But few reports focused on the process of PZT film on other substrates, such as alumina, quartz, BeO and so on.According to appropriate processes, compact and crack-free PZT ferroelectric films with thickness less than one micron were prepared on the Pt/Al₂O₃ and Al₂O₃ substrates by sol-gel method. Lead acetatetrihydrate(Pb(CH₃COO)₂·3H₂O), zirconium nitrate butoxide (Zr(NO₃)₄·5H₂O) and titanium butoxide(Ti(OC₄H₉)₄) were used as the starting materials. The 2-methoxyethnaol(CH₃OC₂H₄OH) was used as solvent, acetylacetone and acid were used as additives. As for the problem of thin thickness, PZT powders were prepared by sol-gel method. Then the PZT thick films were prepared by 0-3 composite method with a slurry, which is prepared by mixed with PZT powders and its' sol.The influence of different conditions on the surface topography of PZT films were investigated, such as sol, substrate, thermal treatment and so on. The growth of PZT films on the substrate was discussed. The form and development of "islet"(or crystal nucleus) on the substrate were analyzed by evaporation-coacervation, surface and volume diffusion mechanisms. The pyknosis and crystallization of PZT film were explained by the sintering of ceramics. The mechanism of crack in the film induced by stress was analyzed. We had calculated and analyzed the stress in the film from the mismatch of thermal expansion and phase transition. The release mechanism of stress was discussed. Arid the methods to avoid crack were put forward. Combined with differential thermal analysis and X- diffraction, the crystallization of PZT film on different substrates were discussed. And the influence of sol-gel process on the crystallization of PZT were also discussed. The influence of anneal temperature, thickness and voltage on the ferroelectric were investigated in the end.The PZT powders with different granularity and dispersity were prepared by sol-gel method. The influence of three modes of gelation (adding ammonia, direct desiccation, heating in water) on the granularity and dispersity was investigated. The influence of different processes on the state of reunite was explained by Lamer model.We had discussed the growth mode of PZT powders in liquid state (the self-growth and reunite-growth of crystal nucleus) and the pyknosis mechanism during the period of sintering. Several steps were put forward to synthesize powders with thin granule, uniformity and good dispersity.In the end, the dispersity and stability in sol of PZT powders were discussed. The thick film with 15 micron was prepared by 0-3 composite method. The influence of powders prepared by different processes on the surface topography of the thick film was investigated. As a result, the thick film prepared with powders, which had stabilized by acetylacetone during the the preparation presented excellent surface topography, the granule in the film were thin and compact.