Elucidation of engineered domain structures of ferroelectric crystals and their high piezoelectricity

阐明铁电晶体的工程域结构及其高压电性

基本信息

批准号：
13450118
负责人：
NAKAMURA Kiyoshi
金额：
$ 3.52万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

The purpose of this research is to elucidate the engineered domain structures of pseudo-cubic ferroelectric crystal KNbO_3 and the high piezoelectricity, and to develop domain control methods and piezoelectric devices utilizing the high coupling factor. The results obtained in this project are summarized as follows: 1. The orientation dependence of various electromechanical coupling factors for KNbO_3 crystal have been calculated and the cut with the highest coupling factor among all known piezoelectrics for the thickness-extensional mode has been found. 2. It was shown that the strain vs. electric-field curve for the pseudo-cubic (001)_<pc> cut of KNbO_3 had a linear characteristic for a low field, but it was hysteretic due to occurrence of 60゜ domains for a high field and exhibited a much higher strain than that estimated theoretically. 3. Chemical etching of crystals for removing micro-cracks lead to no occurrence of 60゜ domain, resulting in non-hysteretic behaviors even for a high electric field. 4. Domain structural change was examined when subjected to heating and cooling through the phase transition temperature and was explained qualitatively. The method for keeping the single domain state when heating through the phase transition temperature was devised and demonstrated to work out. 5. Engineered domain structures were formed by applying an electric field along the (001)_<pc> axis while heating and cooling through the phase transition point. The piezoelectric behavior was demonstrated to exhibit little hysteresis. The domain structure was shown for the first time to consist of two kind of 90゜ laminar domains. 6. It was demonstrated that the KNbO_3 ultrasonic transducer has a more efficient and broader-band characteristic as compared with those of PZT ceramics and LiNbO_3 crystals. To realize higher frequency ultrasonic transducers an ECR-PLD system for epitaxial growth of high quality KNbO_3 films was developed.

这项研究的目的是阐明伪立方体铁电晶体KNBO_3和高压电性的工程结构域结构，并使用高耦合因子开发域控制方法和压电设备。该项目中获得的结果总结如下：1。已经计算了KNBO_3晶体的各种机电耦合因子的方向依赖性，并且在所有已知的厚度延伸模式下所有已知的Piezoelectrics中均具有最高耦合因子的切割。 2。证明了伪立方体的应变与电场曲线（001）_ <pc>切割KNBO_3具有低场的线性特征，但由于发生在高场的60°域而导致的较高域，并且暴露了比理论高得多的应变。 3。用于去除微裂缝的晶体的化学蚀刻不会导致60°结构域发生，即使是高电场，也会导致非滞后行为。 4。在经过相变温度的热量和冷却时检查域的结构变化，并在定性上进行了解释。设计并证明可以奏效时，在通过相变温度加热时保持单个域状态的方法。 5。通过沿（001）_ <pc>轴施加电场时，形成了工程域结构。表明压电行为几乎没有滞后。首次显示了域结构，由两种90层层状结构域组成。 6。证明，与PZT陶瓷和Linbo_3晶体相比，KNBO_3超声传感器具有更有效，更宽的特性。为了实现较高的超声传感器，开发了一种用于高质量KNBO_3膜外延生长的ECR-PLD系统。