Development of novel actuator materials by control of rare earth 4f electron number

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K19019
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 29:Applied condensed matter physics and related fields
• Research Institution: Nagoya University
• Principal Investigator: Takenaka Koshi 名古屋大学, 工学研究科, 教授 (60283454)
• Project Period (FY): 2018-06-29 – 2020-03-31
• Keywords: アクチュエータ / 硫化サマリウム / 価数揺動 / 金属絶縁体転移 / 体積変化 / 負熱膨張

Outline of Final Research Achievements

Sintered bodies of SmS containing various dopants (Y, Ce, Nd, etc.) has been successfully grown by an original method, which is a solid-phase reaction method that enables growth at low temperature and in a short time compared with the conventional method. It was found that these sintered bodies develop a large isotropic negative thermal expansion from a higher temperature than previously reported. Moreover, the difference in the temperature at which the valence transition occurs between the pressure-induced and element-substituted cases was explained from the viewpoint of the electronic state by reflectivity spectroscopy using the single crystals. Furthermore, the system that enables simultaneous measurement of nonlinear conduction and strain induced by an electric field was constructed. Using this system, direct measurement of the strain associated with the valence transition by the electric field was verified for the first time for SmS.

Free Research Field

固体物理学

Academic Significance and Societal Importance of the Research Achievements

「価数揺動」という、基礎物理学の概念を活用し、負熱膨張や体積変化アクチュエータといった、革新的な体積機能を創出する基礎を築いた点で、画期的である。鉛フリーのアクチュエータ材料創出につながるもので、材料学分野に大きな波及効果をもたらすと期待される。
精密な反射分光測定により、Sm1-xRxS系の伝導状態の特異性を示すことができた。この知見は、長い研究の歴史を有する価数揺動の研究でもこれまで明確に意識されてこなかったものであり、価数揺動の理解に貢献するものと考えられる。