Success in Capturing Instantaneous Atomic Movement Induced by Application of Voltage for Millionths of a Second (Press Release)
- Release Date
- 11 Nov, 2011
- BL02B1 (Single Crystal Structure Analysis)
Hiroshima University
Japan Synchrotron Radiation Research Institute
RIKEN
The University of Tokyo
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Scientists from Hiroshima University (President, Toshimasa Asahara), in cooperation with scientists from The University of Tokyo (President, Junichi Hamada), Japan Synchrotron Radiation Research Institute (JASRI; President, Tetsuhisa Shirakawa), and RIKEN (President, Ryoji Noyori), successfully observed that piezoelectric* crystals to which an electric field is applied converge to a certain size after repeated expansion and contraction similar to that of a pressed spring, from the change in the crystal-lattice size with time at the atomic level. The instantaneous atomic movement during the piezoelectric vibration of crystals was observed for the first time in the world by the structural measurement of crystals at a level of one-millionth of a second. This study was carried out as a Power User Project of SPring-8 by Chikako Moriyoshi (Associate Professor) and Yoshihiro Kuroiwa (Professor) of Hiroshima University; Yuji Noguchi (Associate Professor) and Masaru Miyayama (Professor) of The University of Tokyo; Hitoshi Osawa (Research Scientist) and Kunihisa Sugimoto (Research Scientist) of JASRI; and Masaki Takata (Chief Scientist) of RIKEN. The results of this study were published as a spotlight paper in the international journal of The Japanese Society of Applied Physics, Japanese Journal of Applied Physics (JJAP). Piezoelectric crystals microscopically expand, contract, and deform upon the application of an electric field. This phenomenon was discovered by J. Curie and P. Curie in the late 19th century. Today, piezoelectric elements utilizing this phenomenon are indispensable to our everyday lives; for example, they are used to control the ejection of ink in ink-jet printers and in the touch panels of cell phones. Several mechanisms underlying changes in the exterior of piezoelectrics have been discussed; however, it is necessary to examine how atoms are displaced in crystals upon the application of a voltage at the microscopic level to understand the essence of the mechanism. The atomic displacement is too small to be detected; even the movement of a crystal lattice has not been clarified thus far. In this study, by combining two advanced measurement techniques, i.e., crystallography and a high-speed time-resolved measurement technique, the research group succeeded in the in situ observation of a change in the crystal-lattice size of piezoelectric crystals with time of microsecond order during piezoelectric vibration for the first time in the world. The achievements of this study are expected to lead to developments in research on the dynamics of atomic displacement of nanosecond or picosecond order and enable the observation of atoms in an electronic device during operation in a perspective manner. Also, this technology is considered to be applicable to the development of new materials for electric storage devices, such as capacitors and batteries. The results of this study were published in the September issue of JJAP, and the paper was selected as a spotlight paper recommended by the editors of JJAP. Publication: |
<Figures>
An electric field is applied to the c-axis direction of a tetragonal barium titanate (BaTiO3) single crystal. The synchrotron radiation is chopped using an X-ray chopper so that it is synchronized with the waveform of the external electric field. There is a timing adjuster between the X-ray chopper and a voltage pattern generator. The synchrotron radiation pulse is irradiated onto the crystal arbitrary Δt after the direction of the electric field is changed from negative to positive. In this way, instantaneous images of the diffraction spots are recorded on the imaging plate.
When the electric field is changed from negative (I) to positive, polarization reversal occurs (II), and the crystal slightly contracts in the c-axis direction. When the polarization reversal is complete (III), the crystal can significantly expand in the c-axis direction. However, the crystal cannot maintain the expanded condition; c/a decreases and returns to its original value (III-VI). This behavior is similar to the damped oscillation of a spring.
<Glossary>
* Piezoelectric
The piezoelectric effect refers to the following phenomena: a phenomenon in which a potential difference is observed on the surface of a material owing to its polarization as a result of atomic displacement when pressure is applied, and a phenomenon in which the material itself deforms upon the application of an electric field. Materials exhibiting the piezoelectric effect are called piezoelectrics.
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