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Research of the Performances of Ferroelectric Film and Compositional-Graded Ferroelectric Film

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Tutor: WangBiao
School: Harbin Institute of Technology
Course: Solid Mechanics
Keywords: Ferroelectric film,Compositional-graded ferroelectric film,Ginzburg-Landau equat
CLC: TM221
Type: Master's thesis
Year:  2008
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Ferroelectric films have been widely used in many applications such as memorizers, inductors, microwave implements and optics implements for its outstanding ferroelectricity, piezoelectricity, pyroelectricity and nonlinear optics properties. Ferroelectric thin films usually have better properties comparing with the bulk counterparts. The main reason is the mismatch stress induced by the substrate. The influences of size effect, surface effect, and depolarization effect on ferroelectric films are also significant.Compositional-graded ferroelectric film is a kind of functionally graded film. It is the development of ferroelectric in the field of functionally graded film. Such films have both the excellent properties of single comsitional ferroelectric film and some particular and eminent properties such as large charge offset and big pyroelectric coefficient etc. Design of such graded functional films is the focus of recent works.So, in our article, we do some research on the properties of ferroelectric film and compositional-graded ferroelectric film under the frame of Landau-Devonshire theory. The research on ferroelectric film is made up of these work, first, we analyse the free energy composition and apply the time dependent Ginzburg-Landau equation to build a free energy model. Secondly by using a definite difference way we simulate the properties of ferroelectric film. We discuss how stress, extrapolation length and temperature influence on the film, simulate hysteresis loops under different stress and film thickness, analyse and dicuss how size effect and depolarization effect imfluence on the coercive field and remanent polarization.The research on the compositional-graded ferroelectric film is made up of these work. As the same for the research on ferroelectric film, we first discuss the free energy compositon and apply time depedent Ginzburg-Landau equation to buit a free energy model. After that, we use definite differenct way to simulate the properties of compositional-graded film, analyse how temperature and graded compositon imfluence on the properties of the compositiona-graded ferroelectric film. At last, we apply one-dimentional passion equation to solve the charge offset and effective pyroelectric coefficient of the compositional-graded ferroelectric film.And after that, we dicuss how the temperature imfluence on the charge offset and the effective pyroelectric coefficient.
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