Ferroelectric Domain Inversion Caused by Heat Treatment of Piezoelectric Crystals and Its Application.

我们发现当LiNbO_3裸片在1060^0 ℃以上热处理时，或LiTaO_3片在质子交换后热处理时，都发生了铁电畴反转。本研究的目的是澄清这一现象，并开发利用反极性畴的压电器件。主要研究结果如下：1.研究了反型层厚度与热处理条件的关系。随着热处理时间的增加，反型层变厚，畴界最终停止在中面。大气中的水汽对畴反转有显著的促进作用。2.本文研究了质子交换LiTaO_3经热处理形成的反型层厚度与质子交换条件和热处理条件的关系。反型层随着质子交换时间和热处理时间的增加而增厚，而在较长的时间内几乎保持不变。 关于我们 n 1小时。结果表明，使用用于防止质子交换的掩模允许选择性域形成。3.提出了一种通过测量压电响应来估计反型层厚度的方法，阐明了反极性畴在热处理的初始阶段成核。这一事实否定了畴反转是由热释电场引起的可能性。4.提出了一个畴反转是由Li_2O外扩散或质子交换引起的空间电荷电场引起的模型，该模型可以解释大多数畴反转现象。这一点得到了实验结果的支持，当多畴LiTaO_3质子交换和热处理，单畴层的极化指向外的两个表面上形成。5.已经提出并开发了利用反转畴的各种高性能压电器件。它们包括弯曲振动器和无键合层的无阻尼致动器、以偶数阶模式工作的谐振器、SAW反射器和换能器。少

We found that ferroelectric domain inversion took place when bare LiNbO_3 plates underwent heat treatment above 1060^0 C, or when LiTaO_3 plates underwent proton exchange followed by heat treatment. The purpose of this research is to clarify the phenomena and develop piezoelectric devices utilizing antipolarity domains. The results can be summarized as follows :1. The dependence of the inversion layer thickness on heat treatment conditions was investigated. As the heat treatment time was increased, the inversion layer became thick and the domain boundary finally stopped at the median plane. Water vapor in the atmosphere exhibited a notable effect in promoting domain inversion. 2. The dependence of the thickness of inversion layers formed by heat treatment of proton-exchanged LiTaO_3 on conditions of proton exchange and heat treatment was examined. Inversion layers thickened with increasing proton exchange time and heat treatment time, while remaining almost constant at longer times tha … More n 1h. It was shown that the use of masks for preventing proton exchange permitted selective domain formation. 3. A method proposed for estimating the inversion laver thickness by measuring piezoelectric responses clarified that the antipolarity domain nucleated at the initial stage of heat treatment. This fact denies the possibility that the domain inversion is caused by pyroelectric fields. 4. A model that the domain inversion is caused by the electric field of space charges induced by Li_2O outdiffusion or proton exchange was proposed and shown to explain most of the domain inversion phenomena. This was supported by an experimental result that when a multi-domain LiTaO_3 was proton-exchanged and heat-treated, single-domain layers with a polarization directed outward were formed on both surfaces. 5. Various high-performance pizoelectric devices utilizing reversed domains have been proposed and developed. They include bending vibrators and hysteresis-free actuators with no bonding layer, resonators operating in even order modes, SAW reflectors, and transducers. Less