弛豫铁电单晶随温度变化全矩阵材料参数的超声谐振谱定征技术

Ferroelectric relaxor-PbTiO3 single crystals have attracted extensive attentions over the last two decades, due to their ultra-higher piezoelectric properties than traditional Pb(Zr, Ti)O3 (PZT) ceramics. However, their application in acoustic engineering is limited by the deficiency of full matrix material constants as functions of temperature. The full matrix material constants obtained by the pulse-echo and electrical resonant methods from multiple samples with drastically different geometries may not be self-consistent, and the self-consistency problem becomes worse at higher temperatures. The resonant ultrasound spectroscopy (RUS) is presented to determine the full matrix constants of relaxor-PbTiO3 single crystals as functions of temperature in this project. The greatest advantage of the RUS technique is that the self-consistency of the determined results can be guaranteed because they are from the same sample. Firstly, the eigenvalue equation of the rectangular parallelepiped-shaped composite structure consisting of an elastic sample and a [001]c poled relaxor-PbTiO3 single crystal sample, and that of a rectangular parallelepiped sample of [011]c poled relaxor-PbTiO3 single crystal with or without electrode, will be derived. In addition, the programs used to solve them will be written. Secondly, the RUS measuring system will be built. A laser vibrometer and a piezoelectric ultrasonic transducer will be used by this system to measure the resonance spectra of each fabricated sample at two different points on its surface. Moreover, effective mode identification methods will be explored. Finally, the full matrix material constants of [001]c and [011]c poled ferroelectric relaxor-PbTiO3 single crystals as functions of temperature will be determined from identified resonance frequencies by using a robust and reliable non-linear least squares algorithm.

近20年来，弛豫铁电单晶由于压电性能远高于PZT压电陶瓷而倍受重视，然而，由于随温度变化全矩阵材料参数的缺失，限制了其在声学工程中的应用。传统超声脉冲-回波与电阻抗谐振技术所定征随温度变化压电材料全矩阵材料参数，难以自洽，因为其来自于多块尺寸差异显著的样品。本项目提出利用超声谐振谱(RUS)技术定征弛豫铁电单晶随温度变化全矩阵材料参数。RUS技术最大优点是可保证定征结果的自洽，因为其来自于同一块样品。本项目首先导出弹性体与[001]c方向极化弛豫铁电单晶长方体复合结构，以及 [011]c方向极化弛豫铁电单晶长方体的本征值方程，并对其进行求解；其次，构建激光测振仪与压电换能器两点测振的变温RUS测试系统，并对所加工样品进行超声谐振谱测试，建立有效的模式识别机制；最后，选取高鲁棒性与可靠性的非线性最小二乘算法，对[001]c与[011]c方向极化弛豫铁电单晶随温度变化全矩阵材料参数进行反演。

弛豫铁电单晶由于压电性能远高于PZT压电陶瓷而倍受重视,然而,由于随温度变化全矩阵材料参数的缺失,限制了其在声学工程中的应用。传统超声脉冲-回波与电阻抗谐振技术所定征随温度变化压电材料全矩阵材料参数,难以自洽,因为其来自于多块尺寸差异显著的样品。本项目提出利用超声谐振谱(RUS)技术定征弛豫铁电单晶随温度变化全矩阵材料参数。RUS技术最大优点是可保证定征结果的自洽,因为其来自于同一块样品。本项目主要针对以下问题展开研究:1)导出弹性体与[001]c方向极化弛豫铁电单晶长方体复合结构,以及[011]c方向极化弛豫铁电单晶长方体的本征值方程,并对其进行求解;2)构建变温RUS测试系统,并对所加工样品进行超声谐振谱测试,建立有效的模式识别机制;3),选取高鲁棒性与可靠性的非线性最小二乘算法,并编写相关程序对[001]c、[011]c、[111]c]弛豫铁电单晶全矩阵材料参数进行反演。本项目研究成果为弛豫铁电单晶的性能表征提供了新的方法和思路，可为基于弛豫铁电单晶的水声换能器设计提供精确的全矩阵材料系数。项目组按预定研究计划完成了相关研究内容，已在Scripta Materialia, Journal of Materials Sciences, Journal of Applied Physics等国际知名SCI收录期刊发表论文8篇。