Study On Preparation, Microstructure And Properties Of High CurieTemperature Perovskite Piezoelectric Thin Films

High Curie temperature piezoelectric thin films are the research frontier onfunctional ceramic materials. This dissertation mainly focuses on the high Curietemperature Bi（Me）O₃-PbTiO₃system,mainly BiScO₃-PbTiO₃（BSPT） systempiezoelectric thin films, and their fabrication, microstructures and properties weresystematically studied.Firstly, we briefly introduced the fabrication process of polycrystalline BSPT thinfilms via sol-gel method and characterization methods for structure and properties of thethin films. The effects of composition on structure and properties of BSPT thin filmsprepared on Pt（111）/Ti/SiO₂/Si substrates were discussed. The dependence of dielectric,ferroelectric and piezoelectric properties on film thicknesses and relative mechanismswere investigated, the results showed that the interface layer between the electrode andthe film had a major impact on the electrical properties of the film.Secondly, the preparation and performance of highly （100） preferential orientedBSPT thin films were discussed. The detailed preparation process of highly （100）oriented BSPT thin films by introducing the PbO seeding layers was discussed, and itsrelative growth mechanism was exploited. The results showed that the introduction ofPbO seeding layers both at the interface layer and inside the film body, can mosteffectively enhance the degree of （100） preferred orientation, and the Lotgering factor fcould maintain at a high value of0.92even when the film thickness was as thick as950nm. The highly （100）-oriented BSPT thin films had excellent electric properties, andthe piezoelectric coefficient was as high as150pm/V.（100） preferred oriented BSPTfilms were also prepared by using LaNiO3buffer layers, the piezoelectric coefficientsreached up to120pm/V, and fatigue property of the thin films was effectively improved.Thirdly, polycrystalline and epitaxial piezoelectric thin films of otherBi（Me）O₃-PbTiO₃material systems were also prepared via sol-gel method.BiSc_1/2Fe_1/2O₃-PbTiO₃，Bi(Zn_1/2Ti_1/2)O₃-PbTiO₃（BZT-PT）, as well as BZT-BS-PTpolycrystalline thin films were prepared on Pt（111）/Ti/SiO₂/Si substrates, and theirperformance were studied. BZT-PT thin films exhibited extremely high Curietemperature, for0.3BZT-0.7PT thin film, the curie temperature was higher than600℃,and its piezoelectric coefficient is about40pm/V. Epitaxial growth BZT-PT thin films were prepared on （001） SrTiO₃（STO） single crystal substrates by sol-gel method, themicrostructures and properties of these films were studied as well, which showedexcellent ferroelectric and piezoelectric properties. The remanent polarization ofepitaxial films were nearly three times of that of the corresponding orientedpolycrystalline films; and the piezoelectric coefficient were higher than75pm/V, alsomuch higher than that of the oriented polycrystalline BZT-PT films.Finally,（001） epitaxial growth BSPT thick films with thickness higher than3μmwas hydrothermally synthesized on STO（001） single crystals by optimizing the locationof the single crystals in the hydrothermal reactor, which exhibited a dense smoothstructure and unique ferroelectric and piezoelectric properties. The preparation processof BSPT nanotube arrays through templates by Electrophoretic deposition method wasstudied, and the influence of deposition conditions （deposition voltage, depositioncurrent, concentration of the sol, etc.） on the morphology and structure of the preparedsamples was analysed. Besides, the ferroelectric and piezoelectric properties of theBSPT nanotube arrays were preliminary characterized.