边界条件对温度梯度铁电薄膜热释电性质的影响

摘要

In the framework of the mean field approximation, a transverse Ising model was adopted to investigate the influence of different boundary conditions (clamped boundary condition and free boundary condition) on the pyroelectric properties of temperature-graded ferroelectric thin films. A function was introduced to characterize the distribution of the interaction couplings between two pseudo-spins under different boundary conditions. It is shown that the distribution of temperature gradient and boundary conditions have great influence on polarization distribution and pyroelectric coefficients. There are two pyroelectric peaks in curves for temperature-graded ferroelectric thin films. The second peak under free boundary condition is much higher than the peaks of non-graded film and peaks under clamped boundary condition.%在平均场近似的理论框架下,采用横场伊辛模型研究了不同边界条件(固定边界条件和自由边界条件)对温度梯度铁电薄膜热释电性质的影响.引入一个分布函数来描述不同边界条件下赝自旋相互作用系数的变化.研究表明,薄膜内部的温度梯度分布和薄膜所处的边界条件对其极化分布和热释电系数都有很大的影响.温度梯度铁电薄膜的热释电曲线中出现了2个热释电峰,其中自由边界条件下的薄膜所对应的第2个热释电峰比无温度梯度的铁电薄膜和固定边界条件下的温度梯度铁电薄膜的热释电峰都要高出许多.