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.

本研究的目的是阐明赝立方铁电晶体KNbO_3的工程域结构和高压电特性，并开发利用高耦合因子的域控制方法和压电器件。本项目取得的成果总结如下： 1.计算了KNbO_3晶体各种机电耦合因子的取向依赖性，并计算了厚度延伸的所有已知压电体中耦合因子最高的切割2.结果表明，KNbO_3的赝立方(001)_<pc>切割的应变与电场曲线在低场下具有线性特征，但由于发生而呈现迟滞特性。 60゜域的高场并表现出比理论估计高得多的应变3.用于去除微裂纹的晶体化学蚀刻导致不出现60゜域，从而导致。 4. 研究了加热和冷却经过相变温度时的磁畴结构变化，并定性地解释了加热经过相变温度时保持单磁畴状态的方法。 5. 通过沿 (001)_<pc> 轴施加电场，同时通过相变点进行加热和冷却，可以形成工程域结构，该压电行为表现出很小的磁滞域。结构是首次显示由两种90゜层状畴组成。 6.与PZT陶瓷和LiNbO_3晶体相比，KNbO_3超声换能器具有更高效和更宽的频带特性，可实现更高的频率。开发了一种用于外延生长高质量 KNbO_3 薄膜的 ECR-PLD 系统。