Preparation And Energy-storage Properties Of Sodium Bismuth Titanate Based Thin Films

Since1970s, pulse-power-technology has been widely used in laser technology,nuclear technique, accelerators, electron beam, etc. Energy storage technology is one ofthe key parts of pulse-power equipments. In most of the application field, pulse powersystem is enslaved to its volume and weight. So the high energy storage density materialis one of the key elements of pulse-power equipments. Ferroelectric materials couldmeet the high energy density requirement. Na0.5Bi0.5TiO3（abbreviated as NBT） is alead-free perovskite relaxor ferroelectrics, the storage properties of NBT based thinfilms were studied in the paper.In my thesis, NBT,6mol%BaTiO3composites0.94NBT-0.06BaTiO3（abbreviatedas NBT-BT94/6）, Pb（Zr,Ti）O₃with different Zr:Ti （40:60,52:48）（abbreviated as PZT40/60, PZT52/48, respectively） trilayered PZT40/60/NBT/PZT40/60, PZT52/48/NBT/PZT52/48, PZT40/60/NBT-BT94/6/PZT4060, PZT52/48/NBT-BT94/6/PZT52/48thin films were prepared on Pt/Ti/SiO2/Si substrates by sol-gel method. The phasecomposition and microstructure of the films were characterized by X-ray diffraction（XRD） and scanning electron microscopy （SEM）. NBT film annealed at700℃has thebest phase composition and microstructure. All the films have smooth surfaces, clearsection boundries, and no obvious diffusion phenomena.The ferroelectric and dielectric properties of NBT based thin films wereinvestigated. NBT-BT94/6, PZT/NBT/PZT, and PZT/NBT-BT94/6/PZT thin filmsmaximum polarization, remnant polarization are bigger than those of NBT thin films.All the films dielectric-temperature peaks were broading, suggesting relaxivity of thefilms. Compositing BT could reduce the Curie temperature of NBT thin film, but theCurie temperature of trilayered thin films are not change much. At various frequencies,compositing BT and trilayered thin films dielectric constant are bigger than NBT thinfilms.At room temperature, at the frequency of10kHz, and at different fields, the energystorage property of NBT thin film was better than NBT-BT94/6thin film, trilayeredthin films energy storage properties were better than those of corresponding NBTandNBT-BT94/6thin films. At an applied field of1000kV/cm, PZT40/60/NBT/PZT40/60thin film has the highest energy storage density, as high as18.875J/cm³. Energystorage density decreases with increasing temperature, but compositing BT and trilayered thin films energy storage density were greater than that of NBT thin film. Atthe temperature of145℃, at the frequency of10kHz, and at the applied field of1000kV/cm, PZT40/60/NBT/PZT40/60thin film has the highest energy storagedensity of16.373J/cm³. Therefore, compositing BT and reasonable trilayered structuredesign could improve the energy storage performance of NBT thin films.