外加应力对外延Pb(Zr_(1-x)Ti_x)O_3薄膜相图及物理性质的影响

Effect of the External Stress on the Phase Diagrams and Physical Properties of Single-domain Epitaxial Pb(Zr_(1-x)Ti_x)O_3 thin Films

用非线性热力学方法,研究了外加应力及组分对外延单畴Pb(Zr1-xTix)O3(PZT)薄膜的相图及物理性质的影响。通过数值计算,得到了PZT薄膜在不同组分下的"外加应力-失配应变"相图。由相图可知,外加应力可以使薄膜发生铁电相变。在室温下,外加压应力能使薄膜的铁电相转变到顺电相。薄膜的压电系数对相变非常的敏感,施加一个适当的外加应力,可以大幅度提高压电系数。本文的计算结果,可以解释压痕仪和扫描力电镜研究铁电薄膜时所观察到的实验现象。

A nonlinear thermodynamic theory is used to investigate the effect of external stress and composition on the phase diagrams and physical properties of single-domain Pb（Zr1-xTix）O3（PZT） thin films epitaxially grown on dissimilar cubic substrates. The ＂external stress-misfit strain＂ phase diagrams are constructed for PZT films with different compositions. For the phase diagrams, the external stress may lead to phase transitions and the most remarkable theoretical prediction is the stress-induced ferroelectric to paraelectric phase transition, which may take place in PZT films even at room temperature. For the piezoelectric properties, it is very sensitive to the phase transitions, and reaches very high value by adjusting appropriate external stress. The calculated results can be used to explain the experimental phenomena observed via the nanoindentation and scanning force microscopy of ferroelectric films.