Effect Of Thermal Process On Potassium Sodium Niobate Ferroelectric Thin Films Bysol-gel Method

Lead-free sodium potassium niobate(KNN) piezoelectric materials has been regarded as one of the best choices to substitute for lead-based materials because of its high Curie temperature, excellent piezoelectric and ferroelectric properties, as well as biocompatibility. It can be applied to the drivers, transducers, sensors, transformers and other fields. Recently, with the increasing requirements for the miniaturization and integration of electronic devices, piezoelectric thin film has been attracting ever growing attention. The preparation of high-quality KNN thin film has become a hotspot in the field of piezoelectric materials. In this thesis, we try to prepare KNN thin films by alkoxide sol-gel method and non-alkoxide sol-gel method, the main research works and results are as follows:Firstly, the KNN precursor solution was prepared by alkoxide system, ethanol niobium, potassium acetate and sodium acetate were used as niobium source, potassium source and sodium source, respectively, and 2-MOE was used as the solvent. The effect of pyrolysis temperature and annealing temperature on the KNN thin film was studied. It indicates that lower or higher thermal treatment temperature will reduce the quality of KNN thin film. Lower pyrolysis temperature will make the organic incomplete decomposition, while higher pyrolysis temperature will result in serious volatilization of alkaline ions. Lower annealing temperature will make the film hard to completely crystallize, higher annealing temperature will also result in serious volatilization of the alkaline ions.Secondly, the KNN precursor solution was prepared by non-alkoxide system, Nb2O5 was selected as raw material to prepare for Nb(OH)5 of high activity, and the soluble niobate was obtained by citrate method, used as the niobium source. Besides, K2CO3, Na2CO3 were used as the potassium source and sodium source, respectively. Deionized water was used as the solvent. The KNN thin films were fabricated on the Ti substrates, the effects of thermal treatment on crystallinity, microstructure and electrical properties were studied. The results indicate that the films annealed at 700℃ show best crystallization and electrical properties.Thirdly, in order to prepare KNN thin films on the hydrophobic Pt substrates, the non-alkoxide KNN precursor solution as described above was adjusted. 2-MOE was selected as the main solvent, which improve the wettability of the film and the Pt/Ti/Si O2/Si substrate. The thermal treatment was invesgated, and the KNN thin films were successfully fabricated on the hydrophobic Pt substrate.