兰州大学机构库 >土木工程与力学学院
力-电场作用下铁电材料微观结构演变的相场模拟研究
Alternative TitlePhase field simulation of microstructure evolution of ferroelectric materials under mechanical and electric fields
孙芮
Thesis Advisor王省哲
2016-05-28
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name硕士
Keyword铁电材料 有限元方法 微结构演化 相场理论
Abstract铁电材料作为一类具有力-电转化功能的智能材料,其宏观的力电转化效能、相变与力学行为与材料细微观的畴结构、畴界、极化取向等密切关联。众所周知,铁电材料内部的电畴结构又极易被机械约束、温度、电场等外界因素所改变,进而直接影响铁电宏观器件的使用性能和工作周期,同时也使得铁电材料的力电耦合行为比一般材料更加复杂。因此,开展多场耦合下铁电材料微观结构演变以及研究畴结构及畴翻转动力学性能的研究不仅是提高以铁电材料为基础的宏观器件性能不可或缺的途径,同时也是促进铁电材料在复杂的工作环境应用的有效手段。 本文采用相场方法,以热力学和动力学基本原理为基础,针对铁电材料相变过程中微结构演化及电畴特征进行了数值仿真研究。采用时变的金兹堡-朗道(Time Dependent Ginzburg-Landau)方程来描述铁电材料在多场耦合作用下相变过程中畴结构以及畴界等微观结构的演化动力学特性,开展了PbTiO3材料外电场、外力诱发下的相变机制与畴结构演变过程的模拟。研究表明:无外场作用下,铁电材料内部电畴结构随着系统整体能量的演化,发生形核和生长的过程;其中新畴通过扩张和吞噬周边畴的形式长大,达到稳定结构后,畴结构不再随时间变化,畴壁规整,畴结构满足一定的规律性。在无外场下稳定演变结果的基础上,外加电场作用,平衡状态被打破后,电畴随着畴壁的运动生长变大,其中不同区域的极化畴分别进行着90度或180度的极化反转,当系统能量达到极小值时,结构达到稳定状态,不再随时间变化。在无外场下稳定演变结果的基础上,外加应力作用,平衡状态被打破后,只发生可以降低弹性能的90度畴的极化反转,达到稳定状态时,畴结构不再随时间变化。 本文建立的可以用来描述力电耦合下作用铁电材料微观组织结构演变过程的相场模型,为深入探究铁电材料的细微观研究方法提供基本的理论依据与分析途径。同时也为以铁电材料为基础的敏感器件在实际工程应用中力电学性能的预测与评价提供一定的理论指导。
Other AbstractAs is known to all, the electric domain structure of ferroelectric materials is vulnerable to be changed by external factors, such as the electric field, temperature, and mechanical constraints, which directly affect the macro ferroelectric device performance and working cycle. And at the same time, electromechanical coupling behaviors of ferroelectric materials are much more complex than other ordinary materials. Therefore, to carry out the research of ferroelectric materials’ performance under multi field coupled microstructure evolution as well as the macro mechanical and electrical properties is not only the indispensable way to improve the performance of macroscopic devices which are based of ferroelectric materials, but also the effective means to promote ferroelectric materials working in increasingly complex environment. Based on the basic principle of thermodynamics and kinetics, phase field method is established to predict the microstructure evolution during the process of phase transformation. In this paper, we select the time dependent Ginzburg Landau equation to establish a phase field model to describe the dynamic microstructure evolution characteristics of phase boundary, domain boundaries during the process of phase transition of ferroelectric materials under multi field coupling loading. We carry out the simulation of evolutionary process and transformation mechanism about ferroelectric materials under external electric field and mechanical stress field. The results showed that the formation of ferroelectric domains is a process of nucleation and growth with the energy reduction under the condition of no external electric field. The new domain grows through the expansion and devour circumjacent domain, after reaching the stable structure, domain structure is no longer changing with the time, domain wall regularization and domain structure satisfies certain regularity. However, when a constant electric field is applied to the system, equilibrium is broken, those ferroelectric domains who have the same direction with the electric field gradually grow up with 90 or 180 degrees of polarization reversal in different regions respectively. Domain structure is no longer changing with the time when the system energy reaches a minimum value. When a constant force field is applied to the system, after equilibrium is broken, we will find that only 90 degrees domain inversion occurred. This is because the forming process of 90 degrees along with t...
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Language中文
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/226139
Collection土木工程与力学学院
Recommended Citation
GB/T 7714
孙芮. 力-电场作用下铁电材料微观结构演变的相场模拟研究[D]. 兰州. 兰州大学,2016.
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