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Effect of electromechanical boundary conditions on the properties of epitaxial ferroelectric thin films 下载免费PDF全文
The effects of internal stresses and depolarization fields on the properties of epitaxial ferroelectric perovskite thin films are discussed by employing the dynamic Ginzburg-Landau equation (DGLE). The numerical solution for BaTiO3 film shows that internal stress and the depolarization field have the most effects on ferroelectric properties such as polarization, Curie temperature and susceptibility. With the increase of the thickness of the film, the polarization of epitaxial ferroelectric thin film is enhanced rapidly under high internal compressively stress. With the thickness exceeding the critical thickness for dislocation formation, the polarization increases slowly and even weakens due to relaxed internal stresses and a weak electrical boundary condition. This indicates that the effects of mechanical and electrical boundary conditions both diminish for ferroelectric thick films. Consequently, our thermodynamic method is a full scale model that can predict the properties of ferroelectric perovskite films in a wide range of film thickness. 相似文献
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本文采用动态金茨堡-朗道(DGL)方程研究了薄膜厚度与错配应变对 取向单畴外延PbTiO3(PTO)铁电薄膜相结构与稳定性的影响。结合平面内松弛应变(等效应变)、表面效应与退极化场等机电耦合边界条件,通过数值求解DGL方程获得外延单畴铁电薄膜错配应变-厚度相图和错配应变-温度相图。数值分析结果显示,由于生成的界面位错松弛了薄膜内错配应变,在理论高应变区相图与传统分析结果有较大差别,文中发现在更广的理论错配拉应变区出现稳定的四方相(c相)结构和单斜相(r相)结构。结果也显示,随着薄膜厚度的减小,表面效应与退极化效应会把顺电相扩展到更低温度区域,从而压缩稳定的铁电相存在的温度区域。 相似文献
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采用喷射微波燃烧合成法制备了上转换发光显示器中发绿光的上转换发光材料NaYF4∶Er,Yb.测试了该材料的XRD衍射图谱和发光效率.给出了该材料在1 064 nm三种激光功率激发下的发光光谱.分析了该材料的上转换发光机理,得到545 nm和662 nm峰值发光分别是Er3+的4S3/2→4I15/2和4F9/2→4I15/2跃迁产生的.NaYF4∶Er,Yb具有较强的上转换绿光,同时存在的较弱的红光易于用滤色膜滤除,满足显示对三基色中绿色的要求;并且喷射微波燃烧合成法制备的该材料达到了高分辨率显示应用超细粉体的要求. 相似文献
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利用电致伸缩基本方程,采用伪总应力和复变函数解法,并利用级数展开方法得出了含圆形夹杂的无限大电致伸缩材料应力场,在一般情况下,与Eshelby夹杂理论不同,在电致伸缩材料圆形夹杂内部应力场是非均匀的. 相似文献
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It is shown that the constitutive equation and electric body force used to discuss the stress analysis of electrostrictive material in some previous literature are not appropriate. This paper presents the corrected stress solution for the infinite plane with an insulated elliptic hole under an applied electrical field. The numerical result obtained for the PMN material constants show that the stress near the end of the narrow elliptic hole is the tensile stress. 相似文献
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根据弹性力学轴对称平面应变问题的基本方程,采用有限Hankel变换及其逆变换辅以Laplace变换技术,得到了轴对称径向突加电场载荷条件下电致伸缩材料实心圆柱体的动态位移和应力响应的解析解.由于电冲击引起圆柱体内弹性波的传播,动态位移和应力随时间呈不同峰值的周期性变化.数值计算表明,随着半径增大,位移的响应相应增加,在圆柱表面达到静态位移数值的5倍以上;在圆柱表面附近,动态应力响应呈周期性拉压变化,最大幅度可达到静态应力的20倍左右.因此,在计算位移和应力场时,必须考虑电场冲击因素. 相似文献
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基于保角变换技术和Faber级数展开,研究了含任意形状夹杂或缺陷的无限大Reissner板弯曲问题.将变换域中单位圆内、外解析函数分别展开成Faber级数,并将波动函数展开成第一类和第二类修正的n阶Bessel函数;利用边界位移、剪力和弯矩连续性条件得到问题的高阶线性方程组.以含椭圆形夹杂和缺陷的无限大Reissner板柱面弯曲为例,进一步给出了数值算例和理论分析.结果表明,对于软夹杂,板内力矩随夹杂与板厚尺寸比a/h变化非常敏感;在含硬夹杂条件下,板内力矩随夹杂尺寸变化相对不敏感. 相似文献