Preparation And Electric Properties Of Lead And Bismuth Based Perovskite Ferroelectric Thin Films

Ferroelectric thin films have attracted much attention as one of the main multifunctional materials, and have wide application prospects in electronic devices, information technology and energy storage devices. Lead titanate and bismuth ferrite are typical perovskite materials with excellent properties such as ferroelectric and piezoelectric. The structure and properties of the films can be effectively controlled and improved by the substitution of elements and the regulation of strain engineering. In this thesis, lead titanate and bismuth ferrite were used as the starting point; a series of excellent performance ferroelectric thin films were prepared by the use of different chemical and physical methods through the A-site,B-site different element doping, the introduction of isotropic strain and biaxial strain. The effects of element substitution and strain control on the crystal structure, electronic structure, lattice dynamics, ferroelectricity, ferromagnetism and ferroelectric related properties of PbTiO3-based and BiFeO3-based ferroelectric thin films were systematically investigated.The effects of the substitution of different elements on the synthesis and ferroelectric properties of PbTiO3-BiMeO3 were investigated. Through the exploration of PbTiO3-Bi(Zn1/2Zr1/2)O3, PbTiO3-Bi(Mg1/2Ti1/2)O3, PbTiO3-Bi(Mg1/2Zn/2)O3, systems, the ferroelectric thin films with good ferroelectric, fatigue, temperature stability were obtained. The results directly experimently revealed the ferroelectric activities of Ti and Zn ions in PbTiO3-BiMeO3 system are better than Zr and Mg ions, respectively. At the same time, the high-resolution X-ray synchrotron radiation was used to firstly observe that the polarization wake-up is due to the change of domain structure in the ferroelectric.The super-tetraganol PbTiO3 epitaxial composite thin films with large axis ratio were prepared by the introduction of interface strain. The maximum remanent polarization (236.3 ?C/cm2) in ferroelectrics was reported. The phase transition temperature increased from 490 ? of bulk's to 725 ?. First-principles calculations, transmission electron microscopy, X-ray absorption spectroscopy and other means coherently explain the role of interface strain and the reason of giant polarization.The epitaxial films with large axis ratio of BiFeO3 were successfully prepared on the Al2O3 substrate by PLD method for the first time. The low thermal expansion properties of the films were obtained by the tests of temperature-dependent synchrotron radiation XRD, which would be explained by the coupling of ferroelectricity, magnetic phase transition, and biaxial strain through the first-principle calculation and temperature-dependent magnetic properties.With the substitution of Co and Ni for BiFeO3-based thin films, the novel ferroelectric thin films with excellent ferroelectricity, large ferroelectric resistive switching, and switchable ferroelectric photovoltaic were obtained. At the same time through the interface control, the ferroelectric photovoltaic response increased more than three times.