手で粉砕するだけで相転移する超セラミックスを開発～新規圧力・応力センサーの開発に期待～

2025-03-25 北海道大学,北陸先端科学技術大学院大学,京都大学

＜関連情報＞

• https://www.hokudai.ac.jp/news/2025/03/post-1828.html
• https://www.hokudai.ac.jp/news/pdf/250325_pr.pdf
• https://pubs.acs.org/doi/10.1021/jacs.5c00962

マルカサイト型カルボジイミドにおける手粉砕誘起の相転移 Hand Milling Induced Phase Transition for Marcasite-type Carbodiimide

Yuzuki Yamamoto,Kazuki Kume,Suzuka Miyazaki,Ayako Shinozaki,Peng Song,Sayed Sahriar Hasan,Kenta Hongo,Ryo Maezono,Hiroki Ubukata,Hiroshi Kageyama,Mikio Higuchi,and Yuji Masubuchi
Journal of the American Chemical Society  Published: March 24, 2025
DOI:https://doi.org/10.1021/jacs.5c00962

Abstract

While high-pressure phase transitions have been widely studied in inorganic compounds such as oxides and chalcogenides, relatively little attention has been given to compounds containing molecular anions, such as carbodiimides and cyanamides. This study investigates the phase transition of marcasite-type orthorhombic Ba_0.9M_0.1NCN carbodiimides, where a transformation to a CsCl-type tetragonal phase was observed at room temperature under hydrostatic pressure of 0.8 GPa (M = Ca) and 0.3 GPa (M = Sr). This transition, accompanied by an increase in the metal coordination under from 6 to 8, occurs at pressures significantly lower than those required for the high-pressure phase transitions of rock-salt-type metal halides and marcasite-type metal diantimonides. Remarkably, partial phase transitions were also induced by hand milling, a process that applies localized shear forces, distinct from the particle-crushing effects of high-energy ball milling. The transition mechanism, analyzed via variable-cell nudged elastic band (VCNEB) calculations, revealed that while the linear NCN^2– anions remain stable, the shear-sliding of Ba²⁺ cations and the rotation of NCN^2– anions are critical to the structural transformation. These findings underscore the potential of hand milling to effectively induce phase transitions in compounds containing linear molecular anions, offering new strategies for predicting and controlling such transitions in similar materials.